JPH11204890A - Image forming equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the deterioration in a semiconductor laser (LD) accurately and to properly control the semiconductor laser corresponding to its deterioration. SOLUTION: The tilt of a light volume-drive current characteristic curve of an LD becomes gentle with the progress of deterioration in the LD. Then, the drive currents of a semiconductor laser are detected when detected light volumes each get equal to five light volumes. By this setup, five detection points A1 , A2 , A3 , A4 , and A5 as to the light volume-drive current characteristic curve of the LD can be obtained. A differential efficiency η between the two adjacent detection points is calculated. For instance, a differential efficiency η1 between the detection points A1 and A2 and another differential efficiently η2 between the detection points A2 and A3 are calculated respectively. Furthermore, differential efficiencies are indicated on a display, whereby an operator is capable of accurately recognizing the state of deterioration in an LD from the differential efficiencies.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus having a laser light emitting section for emitting laser light according to a drive current, and deflecting light emitted from the laser light emitting section. The present invention relates to an image forming apparatus that forms an electrostatic latent image on an image carrier by scanning.

[0002]

2. Description of the Related Art In a conventional image forming apparatus such as a laser beam printer or a copying machine, a laser exposure device causes a laser beam to blink in accordance with an output image signal, and a uniformly charged photosensitive member surface is caused to blink. An electrostatic latent image is formed on the photoreceptor by exposing with a laser beam. The electrostatic latent image is visualized by developing with toner, the obtained toner image is transferred onto a recording medium such as paper, and fixed on the recording medium to form an image by a so-called electrophotographic method.

As a light source of a laser exposure apparatus for forming such an image on a photoreceptor, a semiconductor laser (laser diode, hereinafter referred to as LD) is generally used. In this LD, a laser beam is modulated and output according to an image to be formed. Further, a light receiving element is provided on the image writing side on the deflection scanning optical path, and horizontal synchronization is established by detecting the laser light passing through the light receiving element, and the image writing timing (that is, the laser light emission timing) is determined. doing.

The laser light is a rotating polygon mirror (polygon mirror)
After being deflected by the optical system, the beam is corrected by an optical system such as a beam diameter. Then, the laser light is focused on the photoconductor and scanned while the horizontal synchronization is performed by the light receiving element, whereby a latent image of a desired output image is formed on the photoconductor.

In such an image forming apparatus, a monitor voltage corresponding to the light output is sequentially compared with a desired voltage reference value (Vref) so that the light output from the laser light becomes a required light output value. And the drive current of the LD is controlled so that the monitor voltage becomes equal to the voltage reference value. Such control is performed by automatic light output adjustment (APC: Auto Power Control).
lol), which is performed in a general laser printer or copying machine, and forms a desired output image.

Next, characteristics of an LD used as a light source will be described. Generally, as a characteristic of an LD, as shown in the graph of FIG. 6, the relationship between the drive current to be supplied and the optical output does not cause laser oscillation until a certain threshold current (Ith), and the threshold current ( When a current exceeding Ith) is supplied, the light output L and the magnitude of the supply current I show linear characteristics (IL characteristics).

Here, the degradation of the IL characteristic will be described. The deterioration of the IL characteristic is roughly classified into the following three factors.

A first factor is a characteristic shift due to temperature. As shown in the graph of FIG.
Of the threshold current (It
As h) increases, the slope of the IL curve in the laser oscillation region slightly decreases.

A second factor is a characteristic shift due to an external factor. An external current applied from outside the LD, for example, an overcurrent that exceeds a rating such as a surge flows into the LD for some reason. Thereby, the optical output of the power corresponding to the overcurrent value is momentarily turned on inside the LD chip. At this time, melting occurs instantaneously at the tip end face.
Depending on the degree of the melting, some of the LDs may be destroyed, while others may be relatively minor injuries and operate normally in normal operation.

[0010] However, even if the deterioration is slight, the luminous efficiency of the one in which the melting occurs on the end face is lower than that in the initial state. That is, a drive current for obtaining the same light output is required to be larger than that in the initial state (see FIG. 5), and the amount of generated heat is increased. At this time, as can be seen from the drive current I-light output L characteristic (see FIG. 6), a higher drive current is required as the temperature rises. Thereby, the luminous efficiency is further deteriorated. By this repetition, the deterioration proceeds, leading to destruction. Looking at the above-mentioned IL characteristics, as shown in FIG. 4, each time static electricity is applied, the IL curve gradually falls on the supply current (drive voltage) axis side. In addition to it,
In the high output region, the linearity of the IL curve is also lost.
That is, the characteristic is such that the slope of the IL curve in the high output region becomes small (bows).

The third factor is deterioration over time. The drive current value for obtaining the same light emission amount gradually increases according to the accumulated time for supplying current to the LD. Similarly to the deterioration state due to the external factors, the curve of the IL characteristic shows a characteristic that gradually falls as shown in the graph of FIG.

Further, in addition to these three factors, L
There is also variation in the element D itself.

On the other hand, the following techniques for monitoring the lifetime of an LD have conventionally been proposed. For example, JP-A-61-166
No. 085 describes the following technique. That is, in a printer, a copying machine, or the like, an upper limit value of a drive current value for obtaining a necessary light output is set in advance. The drive current value is monitored when the drive current value is increased to obtain a required light output. When the drive current value exceeds the upper limit, L
A warning is issued when the life of D is determined.

The following technique is described in Japanese Patent Application Laid-Open No. 2-98462. That is, the threshold current value at power-on is stored. In addition, a driving current value for obtaining an optical output value of 80% of the maximum value of the optical output required for the image forming process during the image forming process is stored. Then, when the difference between the drive current value and the threshold current value is larger than a predetermined determination reference value, the life of the LD is determined.

[0015]

However, in the technique proposed in Japanese Patent Application Laid-Open No. 61-166085,
Since the determination is made based on the drive current value set and stored in advance, it is difficult to accurately detect a deteriorated state due to the influence of temperature fluctuations inside the apparatus during operation of the image forming apparatus and variations in individual apparatuses. It is. In addition, JP-A-2-98
According to the technique proposed in Japanese Patent Application Publication No. 462, a difference between two current values at the time of power-on and at the time of image forming processing is obtained. Therefore, the difference between the two current values includes the effect of temperature fluctuation inside the device. Therefore, it is difficult to detect an accurate deterioration state.

On the other hand, in the prior art example, only the life expectancy is notified, and when the image forming apparatus is deteriorated for some reason, the life of the image forming apparatus cannot be substantially extended. Actually, even if the life of the LD is announced, if the light output does not increase to the specified light amount required for image writing when the initial light amount of the LD is set, the image forming function is stopped at that point, and the built-in optical scanning Until the device is replaced, the image forming apparatus cannot operate normally.

When adjusting the initial light amount of the LD, the drive current is adjusted so that the light output becomes a desired value while increasing the drive current by a predetermined unit light amount adjustment width. On the other hand, as the deterioration of the LD progresses, the slope of the IL curve becomes smaller. Therefore, the number of adjustments of the initial light amount adjustment of the LD increases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has an image forming apparatus capable of detecting an accurate deterioration state of an LD and performing control according to the detected accurate deterioration state. The purpose is to provide.

[0019]

In order to achieve the above object, an image forming apparatus according to the present invention provides a laser beam which emits a laser beam in accordance with a predetermined drive current supplied thereto. An optical scanning device that includes an emission unit and deflects and scans light emitted from the laser light emission unit to form an electrostatic latent image on an image carrier; and a light amount that detects the amount of light emitted from the laser light emission unit Detecting means for detecting a driving current and a light amount based on a plurality of light amount values having different magnitudes detected by the light amount detecting means when a plurality of driving currents having different magnitudes are supplied to the laser beam emitting unit; Differential efficiency represented by the ratio of the other difference to one difference of the values, or calculating means for calculating the ratio of the differential efficiency, and the value of the differential efficiency or the value of the ratio of the differential efficiency calculated by the calculating means Notification means for notifying Characterized in that it.

In the image forming apparatus according to the present invention, the optical scanning device forms an electrostatic latent image on the image carrier by deflecting and scanning light emitted from a laser light emitting section (for example, a semiconductor laser). I do. In such an image forming apparatus, when a plurality of driving currents having different magnitudes are supplied to the laser light emitting unit, the calculating unit may calculate a plurality of light amount values having different magnitudes emitted from the laser light emitting unit. That is, the differential efficiency expressed by the ratio of one difference between the drive current and the light amount value to the other difference from the plurality of light amount values each having a different size detected by the light amount detection means, or Calculate the differential efficiency ratio (if obtained).

Here, for example, the calculating means calculates a plurality of light quantity values having different magnitudes detected by the light quantity detecting means when a plurality of driving currents having different magnitudes are supplied to the laser beam emitting section. You may get it. Further, the calculating means may obtain a plurality of drive current values having different magnitudes when the adjustment is performed so as to have a plurality of light quantity values having different magnitudes.

For example, in the characteristic shown in FIG. 11 showing the relationship between the monitor voltage corresponding to the light amount value and the drive current value,
A drive current value of the laser beam emitting unit when the detected light amount value becomes equal to each of the five light amount values is detected. This gives 5
Two detection points A1, A2, A3, A4, A5 are obtained. Then, the differential efficiency η in the section between two adjacent detection points, that is, (difference in light amount value / difference in drive current value) is calculated. In FIG. 11, (difference in monitor voltage corresponding to light amount value / difference in drive current value) is obtained. As described above, the differential efficiency η may be calculated using a predetermined physical amount (here, a voltage value) corresponding to the light amount value.

Specifically, the differential efficiency η1 is higher than the detection points A1 and A2 in FIG. 11, and the differential efficiency η2 is higher than the detection points A2 and A3.
From the detection points A3 and A4,
4. Differential efficiency η4 is calculated from A5.

The value of the differential efficiency or the value of the ratio of the differential efficiency calculated in this way is reported by the reporting means.
It can be referenced by an operator or the like. As a method of outputting these values, for example, the values may be displayed on a display, printed out on paper, or notified by voice.

As described above, as the deterioration of the laser beam emitting portion progresses, as shown in FIG. 4 and FIG.
As the slope of the characteristic curve in the drive current value characteristic decreases, the characteristic curve bends, and the degree of the bend increases. That is, the value of the differential efficiency and the value of the ratio of the differential efficiency calculated as described above can be said to be a value correlated with the degree of progress of the deterioration of the laser light emitting unit.

Therefore, by outputting the value of the differential efficiency or the value of the ratio of the differential efficiency calculated as described above, the operator can recognize the accurate deterioration state of the laser beam emitting section. Specifically, when the value of the differential efficiency changes by a predetermined value or more from its initial value, or when the value of the ratio of the differential efficiency changes by a predetermined value or more from its initial value “1”,
The operator can recognize that the laser light emitting unit is in a deteriorated state.

Here, the value of the differential efficiency and the value of the ratio of the differential efficiency calculated as described above indicate the state of deterioration of the laser light emitting portion, and the laser light emitting portion includes a plurality of driving units having different sizes. Since the differential efficiency or the ratio of the differential efficiencies is calculated based on a plurality of light amounts each having a different magnitude detected when the current is supplied, the calculated differential efficiency or the ratio of the differential efficiencies is calculated based on the individual image formation. It is a value that eliminates the effects of individual variations of the device and the temperature of the installation location. Therefore, it is possible to detect an accurate deterioration state of the laser light emitting unit. Therefore, the operator can more accurately recognize the deterioration state.

The upper limit of the range of the light amount detected by the light amount detecting means when a drive current having a different magnitude is supplied to the laser beam emitting section is set for the image forming process in the image forming apparatus. It is desirable to set the value larger than the upper limit of the range of the light amount value. For example, as shown in FIG. 11, it is desirable to detect the light amount value of the laser light emitting unit at the detection points A5 and A6 in the light amount region higher than the light amount setting range (1 V to 2 V as the monitor voltage).

As is clear from FIG. 4 and FIG. 11, the bending (curving) of the characteristic curve when deteriorated is particularly conspicuous in the region where the light output is high. By detecting and calculating the differential efficiency and the ratio thereof, it is possible to more clearly detect the bending of the characteristic curve, that is, the deterioration of the laser light emitting unit.

In particular, a plurality of light intensity values having different magnitudes detected by the light intensity detection means include at least two light intensity values which are larger than the upper limit of the light intensity value range set for the image forming process in the image forming apparatus. Value (for example, detection point A5,
A6). By calculating the differential efficiency and its ratio from at least two light intensity values larger than the upper limit of the light intensity value range set for the image forming process in the image forming apparatus, the characteristic curve is bent, that is, Deterioration of the light emitting portion can be more clearly detected. However, the light amount larger than the set upper limit of the light amount value does not exceed the absolute maximum rated light output of the laser light emitting unit.

By the way, as shown in FIG. 11, when the laser beam emitting portion approaches the deteriorated state, the region where the laser light emitting portion is not deteriorated is larger than the upper limit value of the light amount range set for the image forming process. Is smaller than the slope of the IL curve. Therefore, the laser light emitting unit is deteriorated based on the differential efficiency calculated from the light intensity value detected by the light intensity detection unit and the ratio thereof in an area larger than the upper limit value of the light intensity value range set for the image forming process. Is recognized.

Therefore, the notifying means is configured to calculate the differential efficiency or the ratio of the differential efficiency calculated by the calculating means based on at least two light values larger than the upper limit of the range of the light values set for the image forming process. If is less than the predetermined value, it may be further notified that the laser light emitting unit is close to a deteriorated state. Thereby, it can be notified that the laser light emitting unit is in a state close to a deteriorated state.

At the time when the deterioration of the laser beam emitting portion is recognized (that is, when the value of the differential efficiency changes by more than a predetermined value from the initial value, or the value of the ratio of the differential efficiency changes by more than the predetermined value from the initial value) In such a case, the notifying means may notify the operator or the like of the deterioration of the laser beam emitting section to the operator or the like so that the operator or the like can surely recognize the state of deterioration of the laser beam emitting section.

By the way, as described above, the deterioration of the laser light emitting portion progresses, and the light amount of the laser light emitting portion is set to a predetermined light amount necessary for the image forming process in an initial light amount setting stage such as when starting up the image forming apparatus. In order to avoid a situation where the differential efficiency does not rise to the level, the laser beam is emitted to the image forming apparatus when the value of the differential efficiency changes from the initial value by a predetermined value or more, or when the value of the ratio of the differential efficiency changes from the initial value by a predetermined value or more. It is desirable to provide a light amount reference value setting unit that resets a predetermined light amount reference value at the time of initial light amount adjustment of the unit to a low value.

The light amount reference value setting means is provided at the time when the deterioration of the laser beam emitting portion is recognized (that is, when the value of the differential efficiency changes from the initial value by a predetermined value or when the value of the ratio of the differential efficiency changes to the initial value). , A predetermined light amount reference value at the time of adjusting the initial light amount of the laser light emitting unit is reset to a low value. Thereby, even when the maximum drive current is supplied to the laser light emitting unit when the initial light amount of the laser light emitting unit is adjusted, it is possible to avoid a situation in which the light amount of the laser light emitting unit does not increase to the light amount setting level. That is, it is possible to avoid a situation in which the image forming apparatus stops functioning, and to extend the life of the apparatus.

However, in the case where the reference light amount at the time of adjusting the initial light amount of the laser beam emitting unit is set low, the exposure amount of the image carrier may decrease and the density of the formed image may decrease. It is desirable that the developing bias adjusting means adjust the developing bias voltage of the developing device so that the density of the formed image does not decrease. As a result, it is possible to avoid a situation in which the image forming apparatus stops functioning, and also to avoid a decrease in the density of the formed image.

By the way, as described above, the differential efficiency calculated from the light intensity value detected by the light intensity detecting means in the area larger than the upper limit value of the light intensity value range set for the image forming process, and the ratio thereof, It is recognized whether or not the laser light emitting unit is close to a deteriorated state. Therefore, when a plurality of drive currents having different magnitudes are supplied to the laser light emitting unit, at least two drive currents which are detected by the light amount detecting means and are larger than the upper limit of the light amount value range set for the image forming process. Based on the light amount value, a differential efficiency represented by a ratio of one of the difference between the drive current and the light amount value or a ratio of the differential efficiency is calculated, and the calculated differential efficiency is less than a predetermined value or the differential efficiency is calculated. When the efficiency ratio is less than the predetermined value, the predetermined light amount reference value at the time of adjusting the initial light amount of the laser beam emitting unit may be reset to a low value. Also in this case, it is possible to avoid a situation in which the image forming apparatus stops functioning, and to extend the life of the apparatus. When the laser beam emitting unit is in a deteriorated state, the reference light amount is reset to a low value to extend the life of the apparatus, so that the life of the apparatus can be further extended.

However, also in this case, setting the light amount reference value at the time of adjusting the initial light amount of the laser light emitting section to a low value may decrease the exposure amount of the image carrier and decrease the density of the formed image. In some cases, it is desirable to adjust the developing bias voltage of the developing device by the developing bias adjusting means so that the density of the formed image does not decrease. This allows
It is possible to avoid a situation in which the image forming apparatus stops functioning from a state in which the laser beam emitting unit is almost deteriorated, and to avoid a decrease in the density of an image to be formed.

By the way, when the deterioration of the laser beam emitting portion progresses, the driving of the laser beam emitting portion is set to a predetermined light amount at an initial light amount setting stage such as when starting up the image forming apparatus. The current value increases. For example, in the light output value-drive current value characteristic of FIG. 5, when the characteristic S0 in the initial state and the characteristic S1 after the lapse of time t ₀ are compared, the drive current value for obtaining the light output value P ₀ is the initial value. in the state while was Iop (0), after time t ₀ has elapsed becomes Iop (t _0).

Therefore, if the unit light amount adjustment width when adjusting the light amount (ie, performing the above-described APC control) in the initial light amount setting stage of the laser light emitting unit is constant, the light amount of the laser light emitting unit is changed to the predetermined light amount. The time to raise is longer.

Therefore, when deterioration of the laser beam emitting portion is recognized (that is, when the value of the differential efficiency changes by a predetermined value or more from the initial value, or the value of the ratio of the differential efficiency changes by a predetermined value or more from the initial value) In this case, it is desirable to adjust the initial light amount of the laser beam emitting unit by increasing the predetermined unit light amount adjustment width by the light amount adjustment control unit.

By doing so, it is possible to reduce the time required for controlling the amount of light irrespective of the state of deterioration of the laser light emitting section, and to shorten the cumulative lighting time of the laser light emitting section accordingly. Also, when starting up the image forming apparatus,
The time required until the output image of the first page is output (so-called FCOT or FPOT) can be shortened accordingly. That is, the speed of the image forming apparatus can be increased.

Further, the lower limit of the light amount detection range is set smaller than the lower limit of the light amount value range set for the image forming process, and the light amount in the light amount region lower than the light amount value range is set. By increasing the unit light amount adjustment width at an early point in time when the differential efficiency is calculated from the value, it is possible to further reduce the time for increasing the light amount of the laser beam emitting unit to the target light amount for APC control.

Here, the light amount adjusting means adjusts the light amount of the laser light emitting unit until the light amount approaches a target value (for example, an upper limit value) within the range of the light amount value set for the image forming process in the image forming apparatus. The initial light amount of the laser light emitting unit is roughly adjusted with the increased unit light amount adjustment width, and when the light amount of the laser light emitting unit approaches the target value, the unit light amount adjustment smaller than the increased unit light amount adjustment width The initial light amount of the laser beam emitting unit may be finely adjusted by the width. Since the coarse adjustment and the fine adjustment are performed as described above, the light output of the laser light emitting unit can be quickly and accurately set to the target value.

Further, the light amount adjusting means adjusts the light amount emitted from the laser beam emitting section based on the value of the differential efficiency or the value of the ratio of the differential efficiency so that the image forming apparatus sets the light amount for image forming processing. The coarse adjustment is performed by supplying a predetermined drive current corresponding to the value of the differential efficiency or the value of the ratio of the differential efficiency to become the target value within the range of the value to the laser light emitting unit. It may be. As described above, when the coarse adjustment is performed, a predetermined drive current corresponding to the value of the differential efficiency or the value of the ratio of the differential efficiency for providing the target value is supplied to the laser light emitting unit. The light output of the light emitting section can be quickly set to the target value.

In this case, the value of the differential efficiency for determining the drive current or the value of the ratio of the differential efficiency is determined by the calculating means so that the light amount is smaller than the lower limit of the light amount range set for the image forming process. May be a value calculated based on.
Thus, since the value of the differential efficiency or the value of the ratio of the differential efficiency is obtained based on the light amount value smaller than the lower limit value of the light amount value range set for the image forming process, the laser light emitting unit is driven. The drive current can be obtained at an early stage of the current supply, and the light output of the laser light emitting section can be set to the target value more quickly.

By the way, when deterioration of the laser beam emitting portion is recognized (that is, when the value of the differential efficiency changes by more than a predetermined value from the initial value, or when the ratio of the differential efficiency changes by more than the predetermined value from the initial value). In such a case, it is desirable to notify the operator or the like of the deterioration of the laser beam emitting unit by the notifying unit, and to make the operator or the like surely recognize the state of deterioration of the laser beam emitting unit.

The calculating means may calculate the ratio of the differential efficiencies by calculating the ratio between one differential efficiency and the differential efficiencies other than the differential efficiency adjacent to the differential efficiency. That is, for example, in FIG. 11, the initial state will be described as an example.
When two differential efficiencies are obtained, when calculating the ratio of the differential efficiencies, the differential efficiencies and the differential efficiencies other than the differential efficiencies adjacent to the differential efficiencies (the differential efficiencies obtained from the detection points A2 and A3) are calculated. For example, the differential efficiency obtained from the detection points A3 and A4, the differential efficiency obtained from the detection points A4 and A5, the detection point A
5, the ratio with the differential efficiency or the like obtained from A6 may be calculated.

As described above, the ratio of one differential efficiency to the differential efficiency other than the differential efficiency adjacent to the differential efficiency is calculated to calculate the ratio of the differential efficiency. It can be calculated more clearly. In particular, the further apart one differential efficiency is from the differential efficiency other than the differential efficiency adjacent to the differential efficiency, the more clearly the deterioration state of the laser light emitting unit can be calculated. That is, as the order of the deterioration state → the deterioration state → the deterioration state, the detection point is calculated from the ratio between the differential efficiency obtained from the points corresponding to the detection points A1 and A2 and the differential efficiency obtained from the points corresponding to the detection points A3 and A4. The ratio between the differential efficiency obtained from the points corresponding to A1 and A2 and the differential efficiency obtained from the points corresponding to the detection points A4 and A5 can more clearly calculate the deterioration state of the laser beam emitting unit. it can. That is, it is desirable to obtain one differential efficiency from the drive current and the optical output on the smaller value side, and to obtain the differential efficiency other than the differential efficiency adjacent to the differential efficiency from the drive current and the optical output on the larger value side.

[0050]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of the present invention will be described below.

[First Embodiment] First, a first embodiment will be described.

[Schematic Configuration of Image Forming Apparatus] FIG. 1 is a configuration diagram of a main part of an image forming apparatus 30 according to the present embodiment. As shown in FIG. 1, the image forming apparatus 30 is provided with a photosensitive drum 1 as an image carrier, and the photosensitive drum 1 rotates at a predetermined angular velocity in a direction indicated by an arrow Q in FIG. In the vicinity of the outer peripheral portion of the photosensitive drum 1, a charging device 21, a developing device 23, a transfer device 24, and a cleaning device 26 are sequentially installed along the outer periphery. Also,
Above the photosensitive drum 1, an optical scanning device 22 that scans the surface of the photosensitive drum 1 with laser light modulated according to image data of an image to be formed is provided. The scanning position of the laser beam by the optical scanning device 22 is determined by the charging device 2.
1 and the developing position by the developing device 23.

The surface of the photosensitive drum 1 charged by the charging device 21 is scanned and exposed by a laser beam from an optical scanning device 22 modulated according to image data of an image to be formed, thereby forming an electrostatic latent image. Is done. Further, the electrostatic latent image is developed by the developing device 23, and a toner image corresponding to the electrostatic latent image is formed on the surface of the photosensitive drum 1.

On the other hand, the paper P is transferred to the photosensitive drum 1 and the transfer device 2 along a predetermined path in synchronization with the formation of the toner image.
4 is conveyed to the nip portion. A predetermined transfer bias voltage is applied to the transfer device 24 at the timing when the sheet P is conveyed to the nip portion, and the photosensitive member is caused by the application of the transfer bias voltage and the pressing action of the sheet P against the photosensitive drum 1 by the transfer device 24. The toner image on the drum 1 is transferred to the paper P.

The sheet P after the transfer is conveyed to the fixing device 25, and the toner image formed on the sheet P is fixed on the sheet P. The fixed sheet P is conveyed in the direction of arrow W and discharged to a discharge tray (not shown).

Next, the configuration of the optical scanning device 22 will be described with reference to FIG. As shown in FIG. 2, a laser diode (hereinafter, referred to as an LD) 4 is provided in the optical scanning device 22. On the optical axis of the LD 4, a collimator lens 5, a cylinder lens 6. A rotating polygon mirror (polygon mirror) 8 is arranged. The rotating polygon mirror 8 is installed on a motor drive board 11 including a motor for driving the rotating polygon mirror 8 and rotates at a constant angular velocity in a predetermined direction.

On this optical axis, the fθ lens 7, the folding mirror 13 and the folding mirror 10 are arranged in this order from the side closer to the rotary polygon mirror 8, and the light reflected by the folding mirror 10 is (See FIG. 1).

That is, the laser beam emitted from the LD 4
The light passes through the collimator lens 5 and the cylinder lens 6 and is incident on the rotating polygon mirror 8, and is deflected by the rotating polygon mirror 8. The laser beam deflected by the rotating polygon mirror 8 passes through the fθ lens 7 and is reflected by the turning mirrors 13 and 10 in order, and then is irradiated on the surface of the photoconductor 1. At this time, the surface of the photoreceptor 1 is scanned and exposed with the laser light by the deflection of the laser light by the rotary polygon mirror 8. The optical path of the laser light is indicated by a broken line 12 in FIG. The direction in which the photoconductor 1 is scanned by the laser light deflected by the rotary polygon mirror 8 is referred to as a main scanning direction, and the direction orthogonal to the main scanning direction is referred to as a sub-scanning direction.

In the optical scanning device 22, the mirror 9 is arranged at a predetermined position before the position where the photosensitive member 1 first enters the image forming area of the photosensitive member 1 when the photosensitive member 1 is scanned by the laser beam. A horizontal synchronization sensor (SOS sensor) 3 is arranged on the optical axis of the laser beam reflected by the mirror 9.

[Configuration of Circuit for Controlling LD] Next, the configuration of the circuit for controlling the LD 4 will be described with reference to FIGS. As shown in FIG. 7, an LD drive circuit 14 for driving the LD 4 is connected to the LD 4, and the LD drive circuit 14 operates under the control of a microcomputer 32 of the main control board 15, which will be described later. Specifically, the main control board 15
Applies the drive current setting voltage Vop to the LD drive circuit 14, and drives the LD 4 by the LD drive circuit 14. LD
The drive circuit 14 includes a photodiode (not shown). Light from the LD 4 is also received by this photodiode. The photodiode outputs a voltage having a magnitude corresponding to the amount of received light. At this time, the main control board 15
The voltage output from the photodiode according to the light output from D4 is monitored as a monitor voltage Vmo. Note that FIG.
Shows the relationship between the monitor current I _mon corresponding to the monitor voltage Vmo and the light output, and it can be seen that the two are approximately proportional. That is, the main control board 15 detects the light emission amount of the LD 4 by detecting the monitor voltage Vmo.

As shown in FIG. 8, the main control board 15 is provided with a microcomputer (microcomputer) 32 including a CPU, a ROM, a RAM, and the like (not shown). A control panel 16 including a display and a key operation unit is connected to the SOS sensor 3 described above. The microcomputer 32 receives a signal from the SOS sensor 3 and controls the drive timing of the LD 4 based on the signal. Further, the microcomputer 32 displays the LD 4 on the display of the control panel 16 when detecting the deterioration of the LD 4 described later.
A warning message is displayed indicating that has deteriorated.

The microcomputer 32 applies a drive current setting voltage Vop to the LD drive circuit 14 via a circuit composed of the resistors 39 and 38. The microcomputer 32 and the LD drive circuit 1
4, a sample and hold circuit 40 for monitoring the drive current setting voltage Vop, a sample and hold circuit 34 for monitoring a monitor voltage Vmo corresponding to the optical output from the LD 4, and signals for transmitting various control data. A line 46 is provided.

[Regarding the Control by the LD Driving Circuit 14 and the Microcomputer 32] In the image forming apparatus 30, at the stage of adjusting the light amount, the monitor voltage Vmo at which a predetermined light amount is obtained on the photosensitive member 1 is set to a certain value. . For example, the monitor voltage Vmo when a light amount of 0.5 mW is obtained on the photoconductor 1 is 3 V
In this case, the drive current value of the LD 4 is changed so that the monitor voltage becomes 3 V. As described above, in the image forming apparatus 30, so-called APC control (Auto Power Co
ntro1) is executed.

[Operation of First Embodiment] Next, a control routine for detecting deterioration of the LD 4 in the first embodiment will be described with reference to the flowchart of FIG. First, in step 102 of FIG. 9, the drive current value If when the light emission amount of the LD 4 corresponds to each of the three predetermined light amounts P1, P2, and P3 is measured. However, it is assumed that P1 <P2 <P3.

Specifically, the drive current value If1 (mA) when the light emission amount of the LD 4 obtains the monitor voltage value Vmo1 (V) corresponding to the predetermined light amount P1 (mW) is measured. Similarly,
Monitor voltage value Vmo2 corresponding to predetermined light amount P2 (mW)
The drive current value If2 (mA) for obtaining (V) is measured. Similarly, a drive current value If3 (m) for obtaining a monitor voltage value Vmo3 (V) corresponding to a predetermined light amount P3 (mW).
Measure A).

In the next step 104, three measurement points A
1 (If1, Vmo1), A2 (If2, Vmo2), A3
From the measured value at (If3, Vmo3), the measurement point A1-
The differential efficiency η1 in the section of A2 is calculated by the following equation (1), and the differential efficiency η2 in the section of the measurement points A2-A3 is calculated by the following equation (2).
, Respectively.

Η1 = (Vmo2-Vmo1) / (If2-If1) (1) η2 = (Vmo3-Vmo2) / (If3-If2) (2) Further, in the next step 106, The value α of the differential efficiency ratio is calculated by the following equation (3).

Α = η2 / η1 (3) Here, a specific method of the processing in steps 104 and 106 will be described. First, the light emission amount of the LD 4 is equal to a predetermined light amount P.
The drive current value is gradually increased so that a monitor voltage value Vmo1 (V) corresponding to 1 (mW) is obtained.
APC control of the drive current is performed so that Vmol (V) = 1V. The drive current value at this time or the drive current setting voltage Vop1 corresponding thereto is held by the sample and hold circuit 40.

Similarly, when the light emission amount of the LD 4 is equal to the predetermined light amount P 2
(MW), the drive current value is gradually increased so as to obtain a monitor voltage value Vmo2 (V).
The drive current is APC-controlled so that mo2 (V) = 2 V, and the drive current value at this time or the drive current setting voltage Vop2 corresponding thereto is held by the sample-and-hold circuit 40.

Similarly, when the light emission amount of the LD 4 is equal to the predetermined light amount P 3
(MW) so as to obtain a monitor voltage value Vmo3 (V), and gradually increase the drive current value.
The drive current is APC-controlled so that mo3 (V) = 3 V, and the drive current value at this time or the drive current setting voltage Vop3 corresponding to this is held by the sample hold circuit 40.

The microcomputer 32 shown in FIG. 8 monitors a monitor voltage Vmo corresponding to the amount of light from the LD 4, and when the monitor voltage Vmo is a predetermined value (=
Vref (V) and Vmo (V) so that Vref (V)> Vmo (V). If Vref (V)> Vmo (V), the drive current setting voltage Vop (V) is increased, and vice versa. To Vref
When (V) <Vmo (V), the drive current setting voltage Vop
The process of decreasing the value of (V) is repeated. This allows
The light amount from the LD 4 can be set to a predetermined light amount level.

At this time, Vref (V) = 1 V when setting to the predetermined light amount P1 (mW), Vref (V) = 2 V when setting to the predetermined light amount P2 (mW), and the predetermined light amount P3 (mW).
W) can be realized by setting Vref (V) = 3V. Note that Vref (V) = 1 V, Vref (V)
= 2V, Vref (V) = 3V, Vmo (V) is also approximately Vmo (V) = 1V, Vmo (V) = 2V, Vmo (V)
= 3V, the drive current setting voltage Vop (V) is held. Further, from the circuit configuration, the drive current value of the LD can be easily obtained by a return formula from the drive current setting voltage Vop (V).

From the driving current values for the respective predetermined amounts of light obtained in this way, from the above equations (1) and (2),
The differential efficiency of each section is calculated. In addition, the ratio of these values is calculated from equation (3).

When calculating the differential efficiencies η1 and η2, the light amount range is assumed to be wider than the range of the light amount level actually used in the image forming apparatus 30. That is,
As shown in FIG. 11, the light amount range (actual use light amount range) that can be set in the image forming apparatus 30 is from Pmin (mW) to Pm.
ax (mW), the above P1 (mW) is P
min (mW) or less, the above P3 (mW) is Pmax
(MW) or more. That is, P1 (mW) <Pmin (mW) <Pmax (mW) <P3 (mW) (4) The light amount level of P2 (mW) is not particularly limited.

In the next step 108 in FIG. 9, the differential efficiencies η1 and η2 calculated as described above and the value of the ratio α are displayed on the display of the control panel 16. Thereby, the operator can determine the driving current value−
The slopes of the characteristic curves in the light amount value characteristics are represented by differential efficiencies η1, η
2 and the degree of bending of the characteristic curve is recognized by the value of the ratio α between the differential efficiencies η1 and η2,
The deterioration state of the LD 4 can be accurately recognized.

Further, in the next step 110, it is determined whether or not the ratio α of the differential efficiencies η1 and η2 is 0.8 or less.

Here, the meaning of the criterion value “0.8” of the ratio α will be described. As can be seen from the graph of FIG. 4, the monitor voltage Vmo shows a substantially linear characteristic at least in the actual use range (monitor voltage Vmo is in the range of 1 V to 2 V) until the third static electricity (+2 kV) application. On the other hand, thereafter, the deterioration proceeds extremely rapidly. Therefore, the third time can be regarded as the limit of the normal operable range of the image forming apparatus 30. With this third characteristic, the differential efficiency in the section where the monitor voltage Vmo is 1 V to 2 V is η.
1. Assuming that the differential efficiency in the section where the monitor voltage Vmo is 2 V to 2.5 V is η2, the ratio α (= η2 / η1) is about “0.8”.

Therefore, in the present embodiment, the differential efficiency η1,
When the ratio α of η2 becomes 0.8 or less, it is determined that there is a high possibility that the function of the image forming apparatus 30 will be stopped.

If it is determined in step 110 that the ratio α is equal to or less than 0.8, the process proceeds to step 112, where a warning message indicating that the deterioration of the LD 4 has considerably progressed is displayed on the display of the control panel 16.

Thus, the operator can be informed that the deterioration of the LD 4 is considerably progressing, and can be surely recognized.

Further, since the state of the LD 4 built in the image forming apparatus 30 can be known, it is easy to find out that a certain surge is applied to the LD 4 during the manufacturing process and the LD 4 is degraded, and to isolate the trouble. Can be done quickly. In addition, CE (Customer Eng)
In the case where the CE performs the maintenance service of the image forming apparatus 30, the CE can easily perform the isolation of the trouble and shorten the maintenance service time, that is, the time during which the customer cannot use the image forming apparatus 30. Can be.

Further, by detecting the deterioration state of the LD 4 at an early stage, the operator can recognize that the replacement time of the optical scanning device 22 and the like is near and replace the optical scanning device 22 and the like. For this reason, it is possible to prevent a situation in which the image forming apparatus 30 suddenly stops operating and takes a long time to isolate a failed portion.

In the first embodiment, the drive current value of the LD 4 when the light quantity reaches a predetermined value is measured and the differential efficiency is calculated. Conversely, the light output at the predetermined drive current value is monitored by the monitor voltage. More specifically, the differential efficiency may be calculated.

For example, in the control routine shown in FIG. 10, first, at step 103, a predetermined drive current value Iop
1 (mA), Iop2 (mA), Iop3 (mA)
Monitor voltages Vmo1 (V) and Vmo2 when supplied to D4
(V) and Vmo3 (V) are measured.

Then, in the next step 104, the differential efficiency may be calculated using the following equations (5) and (6).

Η1 = (Vmo2−Vmo1) / (Iop2−Iop1) (5) η2 = (Vmo3−Vmo2) / (Iop3−Iop2) (6) The processing after step 106 is the first This is the same as in the first embodiment.

In the first embodiment described above, the light amount range for calculating the differential efficiency is wider than the actual light amount level range in the image forming apparatus 30, but the present invention is not limited to this. Instead, the light amount value at the time of calculating the differential efficiency may be at least two values larger than the upper limit value of the actual light amount level range in the image forming apparatus 30. That is, as shown in FIG. 16, in step 152, the image forming apparatus 3
As described above, the drive current values If5, If6, and If7 corresponding to three light amounts P5, P6, and P7 (see also FIG. 17) larger than the upper limit value of the actual use light amount level range at 0 are measured as described above. I do. However, it is assumed that P5 <P6 <P7.

In the next step 154, as shown in FIG. 17, three measurement points A5 (If5, Vmo5) and A6 (Imo
f6, Vmo6) and A7 (If7, Vmo7), the differential efficiency η5 in the section between the measurement points A5-A6 is calculated by the following equation, and the differential efficiency η6 in the section between the measurement points A6-A7 is calculated by the following equation. Each is calculated as described above.

Η5 = (Vmo6-Vmo5) / (If6-If5) η6 = (Vmo7−Vmo6) / (If7−If6) Further, in the next step 156, the value β of the above-mentioned differential efficiency ratio is given by β = η6 Calculated from / η5.

In the next step 158, the differential efficiency η5, η6 calculated as described above and the value of the ratio β are displayed on the display of the control panel 16.
Accordingly, the operator recognizes the slope of the characteristic curve in the drive current value-light amount characteristic by the differential efficiencies η5 and η6, and determines the degree of the curve of the characteristic curve by the differential efficiency η.
5, the deterioration state of the LD 4 can be accurately recognized by the recognition based on the value of the ratio β of η6.

In the next step 160, it is determined whether or not the ratio β of the differential efficiencies η5 and η6 is less than a predetermined reference value β0. Here, the determination reference value β0 is a value obtained from a number of experiments and capable of determining whether or not the LD 4 is in a state close to a deteriorated state.

If the ratio β of the differential efficiencies η5 and η6 is less than the predetermined judgment reference value β0, in step 162, the LD4
Is displayed on the display of the control panel 16 to the effect that it is in a state close to the state of deterioration.

Also in the above case, the light output at a predetermined drive current value for obtaining a light amount larger than the upper limit of the actual use light amount level range in the image forming apparatus 30 is measured from the monitor voltage, and the differential efficiency is measured. May be calculated.

In the above example, when the ratio β of the differential efficiencies η5 and η6 is less than the predetermined reference value β0, the LD4
Is displayed on the display of the control panel 16, but the present invention is not limited to this, and at least one of the differential efficiencies η5 and η6 has the LD4 deteriorated. If the value is less than a determination value that can be used to determine whether the state is close to the state, L
The fact that D4 is in a state close to a deteriorated state may be displayed on the display of the control panel 16.

[Second Embodiment] Next, a second embodiment will be described. The configuration relating to the control of the image forming apparatus 30 and the LD 4 in the second embodiment is the same as that of the first embodiment, and thus the description is omitted.

[Operation of Second Embodiment] Next, a control routine for detecting deterioration of the LD 4 in the second embodiment will be described with reference to the flowchart of FIG. It is assumed that the values of the differential efficiencies ηi1 and ηi2 in the initial state of the image forming apparatus 30 are stored in the ROM of the microcomputer 32.

First, in step 102 of FIG. 12, similarly to the control routine of FIG. 9, the drive current value If when the light emission amount of the LD 4 corresponds to each of three predetermined light amounts P1, P2, and P3 is determined. Measure. However, P1 <P2 <
P3.

More specifically, the drive current value If1 (mA) when the light emission amount of the LD 4 obtains the monitor voltage value Vmo1 (V) corresponding to the predetermined light amount P1 (mW) is measured. Similarly,
Monitor voltage value Vmo2 corresponding to predetermined light amount P2 (mW)
The drive current value If2 (mA) for obtaining (V) is measured. Similarly, a drive current value If3 (m) for obtaining a monitor voltage value Vmo3 (V) corresponding to a predetermined light amount P3 (mW).
Measure A).

In the next step 104, three measurement points A
1 (If1, Vmo1), A2 (If2, Vmo2), A3
From the measured value at (If3, Vmo3), the measurement point A1-
The differential efficiency η1 in the section of A2 is calculated by the following equation (1), and the differential efficiency η2 in the section of the measurement points A2-A3 is calculated by the following equation (2).
, Respectively.

Η1 = (Vmo2-Vmo1) / (If2-If1) (1) η2 = (Vmo3-Vmo2) / (If3-If2) (2) Then, in the next step 120, calculation is performed. It is checked whether or not the obtained differential efficiency η1 is equal to or less than the differential efficiency ηi1 × 0.5 in the initial state. If the differential efficiency η1 is equal to or smaller than the differential efficiency ηi1 × 0.5 in the initial state, ,
It is considered that the degree of deterioration of the LD 4 is severe, and the process proceeds to step 128 described later.

On the other hand, if the differential efficiency η1 is larger than (the differential efficiency ηi1 × 0.5 in the initial state), step 12 is executed.
Then, it is checked whether or not the calculated differential efficiency η2 is equal to or less than (the differential efficiency ηi2 × 0.5 in the initial state). If the differential efficiency η2 is equal to or less than (the differential efficiency ηi2 × 0.5 in the initial state), it is considered that the degree of deterioration of the LD 4 is severe, and the process proceeds to step 128, which will be described later. × 0.5)
If greater, go to step 124. Step 12
In step 4, the value α of the ratio of the two differential efficiencies is calculated by the following equation (3).

Α = η2 / η1 (3) In the next step 126, the calculated value α of the ratio is 0.8
It is checked whether the ratio is less than or equal to 0.
If it is not more than 8, it is considered that the degree of deterioration of the LD 4 is severe, and the process proceeds to step 128 described later.

As described above, the case where the degree of deterioration of the LD 4 is considered to be severe (that is, when the differential efficiencies η1 and η2 are reduced to half or less of the values in their initial states, and
If the value α of the ratio of the two differential efficiencies drops to 0.8 or less), in step 128, the image forming apparatus 30
Photoconductor 1 in the initial light amount setting stage such as at the start of
The light amount setting value Pset (mW) above is, for example, 1
Lower by the equivalent of nJ / mm2. That is, Pset (mW) = Pset (mW)-(light amount corresponding to 1 nJ / mm2) (7)

At step 128, the light amount set value P
The developing bias voltage value of the developing device 23 is reset in order to prevent the density of the image formed by the image forming device 30 from being reduced due to the change of set (mW). The relationship between the developing bias voltage value and the image density in the image forming apparatus 30 is determined in advance by the image forming apparatus 3.
This is grasped at the stage of designing the parameters of 0 itself, and the optimum value of the developing bias voltage when the light amount corresponding to 1 nJ / mm2 is changed as described above can be easily derived.

Further, at step 128, a warning message indicating that the deterioration of the LD 4 has considerably progressed is displayed on the display of the control panel 16. As a result, the operator can be reliably notified and recognized that the deterioration of the LD 4 is considerably progressing.

In step 128, the light amount setting value Pse
When t (mW) is changed, APC control based on the changed light amount set value Pset (mW) is immediately executed after the processing in FIG.

According to the second embodiment described above, the LD
When the deterioration of No. 4 is recognized, the predetermined light amount set value Pset (mW) is reset to a low value, so that even if the maximum drive current is supplied to the LD 4 as in the conventional case, the light amount set value Ps
et (mW) can be avoided,
A situation in which the image forming apparatus 30 stops functioning can be avoided. In addition, early precautionary measures can be taken.

Further, since the developing bias voltage is adjusted in accordance with the resetting of the light amount set value Pset (mW), it is possible to avoid a situation where the density of the formed image is reduced.

In the second embodiment, the drive current value of the LD 4 at a predetermined light amount is measured to calculate the differential efficiency. On the contrary, the light output at the predetermined drive current value is monitored by the monitor voltage. More specifically, the differential efficiency may be calculated.

Further, the light amount corresponding to 1 nJ / mm 2 as the width for reducing the light amount set value Pset (mW) is merely an example, and it is desirable to set the reduction width according to the characteristics of each image forming apparatus.

It is not essential to adjust the developing bias voltage in accordance with the resetting of the light amount setting value Pset (mW). If the resetting of the light amount setting value Pset (mW) hardly affects the image density, It is not always necessary to adjust the developing bias voltage.

In the second embodiment described above, the light amount range for calculating the differential efficiency is wider than the range of the light amount level actually used in the image forming apparatus 30, but the present invention is not limited to this. As shown in FIG. 18, the light amount value at the time of calculating the differential efficiency may be at least two values larger than the upper limit value of the actually used light amount level range in the image forming apparatus 30. The example illustrated in FIG. 18 is substantially the same as the example illustrated in FIG. 16, and thus only different portions will be described, and description of the same portions will be omitted. In the example shown in FIG.
8 is performed, and when it is determined in step 160 that the ratio β of the differential efficiencies η5 and η6 is less than the predetermined determination reference value β0, the state is close to the state where the LD 4 is deteriorated.
At this stage, the process of step 128 is performed. That is,
Light amount set value Pset (mW) on photoreceptor 1 at the initial light amount setting stage such as when starting up image forming apparatus 30
Is reduced by an amount equivalent to 1 nJ / mm2 as an example. Further, the developing bias voltage value of the developing device 23 is reset.
Further, a warning message indicating that the LD 4 is almost in a state of deterioration is displayed on the display of the control panel 16. As a result, the operator is reliably notified that the LD 4 is in a state close to a deteriorated state,
Can be recognized. Also, at a stage where the LD 4 is in a state close to a deteriorated state, the light amount setting value Pset is set.
(MW), it is possible to further extend the life of the device. This is because, when the LD 4 is in a state close to the state of deterioration, the time until the LD 4 is deteriorated is shorter than the time until the state of the LD 4 becomes close to the state of deterioration. The light amount setting value Pset (mW) is lowered early so as to further extend the life of the apparatus.

[Third Embodiment] Next, a third embodiment will be described. The configuration relating to the control of the image forming apparatus 30 and the LD 4 in the third embodiment is the same as that of the first embodiment, and thus the description is omitted.

When the deterioration of the LD 4 progresses, the drive current value of the semiconductor laser for setting the light amount of the LD 4 at a predetermined light amount at an initial light amount setting stage such as when the image forming apparatus is started up becomes high. For example, in the driving current-light amount characteristic graph shown in FIG. 13, the characteristic Y1 changes to the characteristic Y2 due to the deterioration of the LD4. Accordingly, the drive current If for increasing the light amount of the LD 4 to the light amount set value in FIG. 13 increases from the current I1 to the current I2. Therefore,
When the light amount is set with a predetermined light amount adjustment one step width ΔJ1, 12 steps are required instead of the conventional 8 steps. In the third embodiment, control for solving such inconvenience will be described.

[Operation of Third Embodiment] Next, a control routine in the third embodiment will be described with reference to the flowchart of FIG. The ROM of the microcomputer 32 stores the differential efficiencies ηi1 and ηi2 in the initial state of the image forming apparatus 30.
Is stored.

First, in step 102 of FIG. 14, similarly to the control routine of FIG. 9, the drive current value If when the light emission amount of the LD 4 corresponds to each of the three predetermined light amounts P1, P2, and P3 is determined. Measure. However, P1 <P2 <
P3.

Specifically, the drive current value If1 (mA) when the light emission amount of the LD 4 obtains the monitor voltage value Vmo1 (V) corresponding to the predetermined light amount P1 (mW) is measured. Similarly,
Monitor voltage value Vmo2 corresponding to predetermined light amount P2 (mW)
The drive current value If2 (mA) for obtaining (V) is measured. Similarly, a drive current value If3 (m) for obtaining a monitor voltage value Vmo3 (V) corresponding to a predetermined light amount P3 (mW).
Measure A).

In the next step 104, three measurement points A
1 (If1, Vmo1), A2 (If2, Vmo2), A3
From the measured value at (If3, Vmo3), the measurement point A1-
The differential efficiency η1 in the section of A2 is calculated by the following equation (1), and the differential efficiency η2 in the section of the measurement points A2-A3 is calculated by the following equation (2).
, Respectively.

Η1 = (Vmo2-Vmo1) / (If2-If1) (1) η2 = (Vmo3-Vmo2) / (If3-If2) (2) Then, in the next step 130, calculation is performed. It is checked whether the differential efficiency η1 at the lowest light level is equal to or less than (the differential efficiency ηi1−0.1 in the initial state), and if the differential efficiency η1 is (the differential efficiency ηi1− If 0.1) or less, it is considered that the degree of deterioration of the LD 4 is severe, and the process proceeds to step 132.

In step 132, the APC control is performed by doubling the drive current value (= 1 step width) changed in one step in the APC control. For example, in the state of the drive current-light amount characteristic Y2 shown in FIG. 13, the light amount adjustment one step width is changed from ΔJ1 to ΔJ2 (= ΔJ1) from the fifth step.
By resetting to × 2), the light amount adjustment in the fifth and subsequent steps is performed as shown by the thick line in FIG. 13, and the light amount adjustment is completed in eight steps instead of the twelve steps.

As described above, it is possible to prevent the light amount control time from being lengthened due to the deterioration of the LD 4.

It should be noted that hereafter (steps 134 to 1 in FIG. 14)
40) corresponds to step 106 in FIG. 9 in the first embodiment.
To 112.

By the way, in step 132, the AP
The drive current value (= 1 step width) changed in one step in the C control is doubled to adjust the light amount. However, the present invention is not limited to this, and as shown in FIG.
Instead of step 132, in step 164, the drive current value (= 1 step width) to be changed in one step in the APC control is set twice (coarse adjustment) to the current value (coarse adjustment).
At 65, power increment (increase the drive current) is performed. By this power increment, the light output is close to the target value of the light amount setting range, for example, the upper limit, that is,
For example, since the value is 80%, as a result, step 1
66 is affirmatively determined, and in step 168, the driving current value (= 1 step width) changed in one step in the APC control is adjusted to half the current value to adjust the light amount (fine adjustment), and the light output is adjusted to the target value. You may make it become.

By the way, in the initial light quantity setting stage, the LD
In order to increase the light amount of No. 4 to a predetermined light amount set value, it is possible to calculate how much drive current should be supplied from the value of the differential efficiency η.

Therefore, instead of the control routine of FIG.
The control routine of FIG. 15 may be executed. That is, FIG.
If the differential efficiency η1 is equal to or less than (the differential efficiency ηi1−0.1 in the initial state) in step 130, it is considered that the degree of deterioration of the LD 4 is severe, and in step 131, the light output of the LD 4 is changed to the light amount for the image forming process. The remaining drive current value ΔIf up to the upper limit value of the setting range is obtained by the following equation (8).

ΔIf (mA) = (Vset−Vmo2) / η1 (8) where LD corresponding to the predetermined light amount level Pset (mW)
Is set to Vset (V).

The present invention is not limited to this. The driving current value for the light output of the LD 4 to become the upper limit of the light amount setting range for the image forming process is stored in accordance with the differential efficiency, and the calculated differential efficiency is stored. May be obtained by searching for a drive current corresponding to

Further, in the next step 133, the drive current value is increased at once by the calculated drive current value ΔIf.

By performing such control, the light amount control time can be reduced regardless of the state of deterioration of the LD.

In the example shown in FIG. 19, instead of step 164, the coarse adjustment may be performed by supplying the driving current searched and obtained as described above.

In the third embodiment, the drive current value of the LD 4 at the predetermined light amount is measured to calculate the differential efficiency. On the contrary, the light output at the predetermined drive current value is monitored by the monitor voltage. More specifically, the differential efficiency may be calculated.

Further, when the differential efficiency η1 has decreased to (differential efficiency ηi1−0.1 in the initial state) or less,
The deterioration of LD4 was determined, but the above "0.1"
This is merely an example, and it is desirable to set a constant at the time of determination according to the characteristics of each image forming apparatus.

Further, in the third embodiment, after calculating the differential effects η1 and η2, if the differential efficiency η1 changes from the initial value by a predetermined value or more, the one step width in the APC control is doubled. (See step 132 in FIG. 14),
The remaining drive current value ΔIf is increased at a stretch (see steps 131 and 133 in FIG. 15), and coarse adjustment and fine adjustment are performed (steps 164 to 168 in FIG. 19). However, the present invention is not limited to this. At the stage when the differential effect η1 is determined, one step width in the APC control is doubled (FIG. 14), the remaining drive current value ΔIf is increased at a stretch (FIG. 15), and coarse adjustment and fine adjustment are performed (FIG. 15). 19). As a result, the time required to increase the light output to the target value can be reduced.

In the first to third embodiments, the case where the number of measurement points is three has been described. However, measurement may be performed with more measurement points. Further, the differential efficiency ratio is determined based on adjacent differential efficiencies, but the present invention is not limited to this, and the differential efficiency ratio may be determined based on distant differential efficiencies.

That is, the ratio of the differential efficiency may be calculated by calculating the ratio between one differential efficiency and the differential efficiency other than the differential efficiency adjacent to the differential efficiency. That is,
For example, taking the initial state in FIG. 11 as an example, when one differential efficiency is obtained from the detection point A1 and the detection point A2, when obtaining the ratio of the differential efficiency, the differential efficiency and the differential efficiency are obtained. Differential efficiency (detection point A2,
Differential efficiency other than the differential efficiency obtained from A3), for example, the differential efficiency obtained from the detection points A3 and A4, the detection point A
4, the ratio between the differential efficiency obtained from A5, the differential efficiency obtained from the detection points A5 and A6, and the like may be calculated.

As described above, the ratio of the differential efficiency is calculated by calculating the ratio of one differential efficiency to the differential efficiency other than the differential efficiency adjacent to the differential efficiency. Can be calculated. In particular, 1
The more the two differential efficiencies and the differential efficiencies other than the differential efficiencies adjacent to the differential efficiencies are better, the more clearly the degradation state of the LD 4 can be calculated. In other words, the detection point A
1, the differential efficiency obtained from the points corresponding to A2 (the points at which the drive current or the optical output corresponds to the detection points A1 and A2) and the detection point A
3. From the ratio with the differential efficiency obtained from the point corresponding to A4,
The ratio between the differential efficiency obtained from the points corresponding to the detection points A1 and A2 and the differential efficiency obtained from the points corresponding to the detection points A4 and A5 can calculate the deterioration state of the LD 4 more clearly. . That is, it is desirable to obtain one differential efficiency from the drive current and the optical output on the smaller value side, and to obtain the differential efficiency other than the differential efficiency adjacent to the differential efficiency from the drive current and the optical output on the larger value side.

For example, when calculating the ratio between the differential efficiency obtained from the points corresponding to the detection points A1 and A2 and the differential efficiency other than the differential efficiency adjacent to the differential efficiency, the detection point A
1, the differential efficiency obtained from the point corresponding to A2 and the detection point A
1 drive current and light amount value (light output) and detection points A2, A
, The ratio of the differential efficiency obtained from the drive current and the light intensity value (light output) at a point corresponding to any of A4,..., And the differential obtained from the points corresponding to the detection points A1 and A2. From the efficiency, the drive current and the light amount (light output) at the point corresponding to the detection point A2 and the drive current and the light amount (light output) at the point corresponding to any of the detection points A4, A5, A6,. The ratio between the obtained differential efficiency and the obtained differential efficiency may be obtained or obtained.

[0138]

As described above, according to the present invention, when a plurality of drive currents having different magnitudes are supplied to the laser beam emitting portion, based on a plurality of light quantity values having different magnitudes detected respectively. Since the differential efficiency or the ratio of the differential efficiencies that indicate the state of deterioration of the laser light emitting unit is calculated, the accurate deterioration state that eliminates the effects of individual variations in the individual image forming devices of the laser light emitting unit and the temperature of the installation location is removed. Can be detected,
It has the effect of.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus.

FIG. 2 is a schematic configuration diagram of an optical scanning device.

FIG. 3 is a graph showing an optical output-monitor current characteristic for each temperature.

FIG. 4 is a graph showing deterioration of drive voltage-monitor voltage characteristics due to static electricity application.

FIG. 5 is a graph showing the deterioration over time of the light output-current characteristics.

FIG. 6 is a graph showing light output-forward current characteristics for each temperature.

FIG. 7 is an overall configuration diagram of a semiconductor laser, a semiconductor laser drive circuit, and a control circuit.

FIG. 8 is a block diagram of a semiconductor laser drive circuit and a control circuit.

FIG. 9 is a flowchart illustrating a control routine according to the first embodiment.

FIG. 10 is a flowchart illustrating an example of another control routine according to the first embodiment.

FIG. 11 is a graph for explaining a differential efficiency and a light amount setting level.

FIG. 12 is a flowchart illustrating a control routine according to the second embodiment.

FIG. 13 is a graph for explaining a change of one step width in APC control.

FIG. 14 is a flowchart illustrating a control routine according to a third embodiment.

FIG. 15 is a flowchart illustrating an example of another control routine according to the third embodiment.

FIG. 16 is a flowchart illustrating an example of a control routine according to a modification of the first embodiment.

FIG. 17 is an explanatory diagram for describing processing by the control routine in FIG. 16;

FIG. 18 is a flowchart illustrating an example of a control routine according to a modification of the second embodiment.

FIG. 19 is a flowchart illustrating an example of a control routine according to a modification of the third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor (image carrier) 4 Semiconductor laser 8 Rotating polygon mirror 14 Semiconductor laser drive circuit 15 Control circuit 21 Charging device 22 Optical scanning device 23 Developing device

Claims (16)

[Claims] An image carrier that deflects and scans light emitted from the laser light emitting section when a predetermined driving current is supplied to emit laser light corresponding to the driving current. An optical scanning device that forms an electrostatic latent image thereon; a light amount detection unit that detects a light amount emitted from the laser light emitting unit; and a plurality of driving currents having different magnitudes are supplied to the laser light emitting unit. The differential efficiency expressed by the ratio of one difference between the drive current and the light intensity value to the other difference, based on the plurality of light intensity values detected by the light intensity detection means. An image forming apparatus comprising: a calculating unit that calculates a ratio of the differential efficiency; and a notifying unit that notifies a value of the differential efficiency or a value of the ratio of the differential efficiency calculated by the calculating unit. 2. An upper limit value of a range of a light amount value detected by the light amount detecting means when a driving current having a different magnitude is supplied to the laser light emitting unit, the upper limit value being set for an image forming process in the image forming apparatus. 2. The image forming apparatus according to claim 1, wherein the light amount is set to be larger than an upper limit value of the range of the light amount value. 3. The method according to claim 1, wherein the plurality of light amount values having different magnitudes detected by the light amount detecting means include at least two light amount values larger than an upper limit of a light amount value range set for image forming processing in the image forming apparatus. The image forming apparatus according to claim 2, wherein the image forming apparatus includes one light amount value. 4. The notifying means, according to the calculating means,
When the differential efficiency or the ratio of the differential efficiencies calculated based on at least two light intensity values larger than the upper limit value of the light intensity value range set for the image forming process is less than a predetermined value, the laser light emitting unit The image forming apparatus according to claim 3, further notifying that the image is close to a deteriorated state. 5. The laser light emitting unit according to claim 1, wherein the notifying unit changes the differential efficiency value from the initial value by a predetermined value or more or the differential efficiency ratio value changes by a predetermined value or more from the initial value. The image forming apparatus according to any one of claims 1 to 4, further notifying that the image has deteriorated. 6. An image carrier which is provided with a laser beam emitting section for emitting a laser beam corresponding to the driving current when a predetermined driving current is supplied, and deflects and scans the beam emitted from the laser beam emitting section. An optical scanning device that forms an electrostatic latent image thereon; a light amount detection unit that detects a light amount emitted from the laser light emitting unit; and a plurality of driving currents having different magnitudes are supplied to the laser light emitting unit. The differential efficiency expressed by the ratio of one difference between the drive current and the light amount to the other difference based on the plurality of light amounts each having a different magnitude detected by the light amount detecting means, Calculating means for calculating the ratio of the differential efficiency calculated by the calculating means when the value of the differential efficiency has changed by a predetermined value or more from the initial value or the value of the differential efficiency calculated by the calculating means has a predetermined value from the initial value The place that changed A light amount reference value setting unit that resets a predetermined light amount reference value at the time of initial light amount adjustment of the laser light emitting unit to a low value. 7. A developing bias for adjusting a developing bias voltage of a developing device of an image forming apparatus so that the density of an image to be formed does not decrease when the light amount reference value is reset by the light amount reference value setting means. The image forming apparatus according to claim 6, further comprising an adjusting unit. 8. An image carrier which is provided with a laser beam emitting section for emitting a laser beam corresponding to the driving current when a predetermined driving current is supplied, and deflects and scans the beam emitted from the laser beam emitting section. An optical scanning device that forms an electrostatic latent image thereon; a light amount detection unit that detects a light amount emitted from the laser light emitting unit; and a plurality of driving currents having different magnitudes are supplied to the laser light emitting unit. In this case, based on at least two light amount values that are detected by the light amount detection means and are larger than the upper limit value of the light amount value range set for the image forming process, one of the difference between the driving current and the other light amount value Differential efficiency represented by the ratio of the difference, or calculating means for calculating the ratio of the differential efficiency, and if the differential efficiency calculated by the calculating means is less than a predetermined value or the ratio of the differential efficiency is less than a predetermined value, The laser light An image forming apparatus comprising: a light amount reference value setting unit that resets a predetermined light amount reference value at the time of initial light amount adjustment of the emission unit to a low value. 9. A developing bias for adjusting a developing bias voltage of a developing device of an image forming apparatus so that the density of an image to be formed does not decrease when the light quantity reference value is reset by the light quantity reference value setting means. 9. The image forming apparatus according to claim 8, further comprising an adjusting unit. 10. An image carrier, comprising: a laser beam emitting section for emitting a laser beam corresponding to the driving current when a predetermined driving current is supplied, and deflecting and scanning light emitted from the laser beam emitting section. An optical scanning device that forms an electrostatic latent image thereon; a light amount detection unit that detects a light amount emitted from the laser light emitting unit; and a plurality of driving currents having different magnitudes are supplied to the laser light emitting unit. The differential efficiency expressed by the ratio of one difference between the drive current and the light amount to the other difference based on the plurality of light amounts each having a different magnitude detected by the light amount detecting means, Calculating means for calculating the ratio of the differential efficiency calculated by the calculating means when the value of the differential efficiency has changed by a predetermined value or more from the initial value or the value of the differential efficiency calculated by the calculating means has a predetermined value from the initial value Changed In this case, the image forming apparatus includes: a light amount adjusting unit that adjusts an initial light amount of the laser light emitting unit by increasing a predetermined unit light amount adjustment width. 11. A lower limit value of a range of a light amount value detected by the light amount detecting means when a driving current having a different magnitude is supplied to the laser light emitting unit, the lower limit value being used for image forming processing in the image forming apparatus. 11. The light amount value set to be smaller than the lower limit value of the range of the light amount value set to (10).
The image forming apparatus as described in the above. 12. The light amount adjusting means until the light amount of the laser beam emitting unit approaches a target value within a range of a light amount value set for image forming processing in the image forming apparatus.
The initial light amount of the laser light emitting unit is roughly adjusted with the increased unit light amount adjustment width, and when the light amount of the laser light emitting unit approaches the target value, a unit smaller than the increased unit light amount adjustment width. The image forming apparatus according to claim 10, wherein an initial light amount of the laser light emitting unit is finely adjusted by a light amount adjustment width. 13. The image forming apparatus according to claim 13, wherein the light amount adjusting unit controls the amount of light emitted from the laser beam emitting unit based on the value of the differential efficiency or the value of the ratio of the differential efficiency for image forming processing in the image forming apparatus. By supplying a predetermined drive current corresponding to the value of the differential efficiency or the value of the ratio of the differential efficiency to the target value within the range of the set light amount value to the laser light emitting unit, The image forming apparatus according to claim 12, wherein the coarse adjustment is performed. 14. A value of a differential efficiency for determining the drive current or a value of a ratio of the differential efficiency is calculated by the calculating means.
14. The image forming apparatus according to claim 13, wherein the value is calculated based on a light amount value smaller than a lower limit value of a light amount value range set for the image forming process. 15. When the value of the differential efficiency changes by a predetermined value or more from an initial value, or when the value of the ratio of the differential efficiency changes by a predetermined value or more from the initial value, it is notified that the laser light emitting unit has deteriorated. The image forming apparatus according to any one of claims 6 to 14, further comprising a notifying unit for notifying. 16. The differential efficiency is calculated by calculating a ratio between one differential efficiency and differential efficiencies other than the differential efficiency adjacent to the differential efficiency. The image forming apparatus according to claim 1.