JPH0887076A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] The light intensity of the fluorescent lamp when setting the amplification factor of the amplifier that amplifies the output signal of the photoelectric conversion means is almost the same regardless of the difference in ambient temperature. (EN) Provided is an image forming apparatus capable of eliminating the influence on image density by reducing the difference from the light amount during formation. [Arrangement] A thermistor 25 detects the ambient temperature in the scanner unit and sends the detection result to the CPU 51. CPU5
1 determines the lighting time of the fluorescent lamp 13 before setting the amplification factor of the amplifier 58 that amplifies the output signal of the line sensor 14 in accordance with the detected ambient temperature, and the fluorescent lamp 13 only during the determined lighting time. Light up. When the lighting time of the fluorescent lamp 13 ends, the CPU 51 determines that the fluorescent lamp 1 at that time
The reference plate data due to the reflected light from the white reference plate due to the light of No. 3 is fetched from the output of the A / D converter 59, and the amplification factor of the amplifier 58 is set to the optimum value according to the reference plate data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention, for example, irradiates a document placed on a document table with light from a light source that moves along the document table, photoelectrically converts the reflected light, and outputs an image signal. The present invention relates to an image forming apparatus such as a digital copying machine which outputs an image and forms an image by an electrophotographic method based on the image signal.

[0002]

2. Description of the Related Art Recently, light from a light source in a scanning unit which moves along a platen is irradiated onto a document surface placed on the platen, and the reflected light is photoelectrically converted to output an image signal. Then, the laser beam light is modulated based on this image signal and scanning exposure is performed on the photoconductor drum to form an electrostatic latent image on the photoconductor drum. A digital copying machine for forming an image thereon has been put into practical use.

Conventionally, in such a digital copying machine, a fluorescent lamp is used as a light source for irradiating a document with light.
A CCD line sensor is used as photoelectric conversion means for photoelectrically converting the reflected light from the original.

Generally, since the output signal of the line sensor is a very small signal, it is amplified to a predetermined level by an amplifier, A / D converted, and then sent to an image processing unit or the like. There is.

Now, in such a digital copying machine, after the power is turned on, it is in a ready state (copyable state).
Until then, the process of setting the amplification factor of the amplifier that amplifies the output signal of the line sensor to the optimum value is performed. This amplification rate setting process energizes the lamp heater provided to keep the temperature of the fluorescent lamp tube wall at a constant value at the same time as turning on the power, and turns on the fluorescent lamp when the tube wall temperature reaches a constant value. Then, the light of the fluorescent lamp at that time is applied to the white reference plate disposed near the document table, and the light reflected from the white reference plate due to this light irradiation causes the above-mentioned output signal from the amplifier to be output. The amplification factor of the amplifier is set.

[0006]

Generally, the rising characteristics of the light quantity of a fluorescent lamp are faster as the ambient temperature is higher and slower as the ambient temperature is lower. In setting the amplification factor of the amplifier, the light quantity of the fluorescent lamp is for determining the amplification degree of the signal, and the rising characteristic of the light quantity is very important.

However, as in the prior art, merely heating the tube wall temperature of the fluorescent lamp with the lamp heater does not warm up the temperature inside the tube of the fluorescent lamp, so that it takes time until the amount of light becomes stable. Therefore, especially when the ambient temperature is low, a difference occurs between the light amount when the amplification factor of the amplifier is set and the light amount during image formation, which affects the image density. There is a problem that a difference in image density occurs due to the difference.

Therefore, according to the present invention, the light quantity of the fluorescent lamp at the time of setting the amplification factor of the amplifier for amplifying the output signal of the photoelectric conversion means becomes almost the same regardless of the difference in ambient temperature, and the light quantity at the time of setting the amplification factor and the image An object of the present invention is to provide an image forming apparatus that can reduce the difference between the light amount during formation and the influence on the image density.

[0009]

SUMMARY OF THE INVENTION An image forming apparatus according to the present invention includes a reference plate arranged near a platen and a fluorescent lamp for irradiating a document placed on the platen with light. And a moving means for moving the fluorescent lamp relative to the reference plate and the original, and converting light from the reference plate and the original by the light irradiation of the fluorescent lamp moved by the moving means into an electric signal. Image forming means for forming an image on the basis of an output signal corresponding to the light from the original by the light irradiation of the fluorescent lamp, which is output from the amplifier, and an amplifier for amplifying the output signal of the photoelectric converting means. Means, heating means for heating the tube wall of the fluorescent lamp to a constant temperature when the device is powered on, and heating the tube wall of the fluorescent lamp to a constant value by heating the heating means. The atmosphere of the device Temperature detecting means for detecting the temperature, time according to the tube wall temperature detected by the temperature detecting means, fluorescent lamp control means for turning on the fluorescent lamp, and lighting time of the fluorescent lamp by the fluorescent lamp control means When finished, irradiate the light of the fluorescent lamp at that time to the reference plate,
Amplification factor setting means for setting the amplification factor of the amplifier to a predetermined value based on the output signal output from the amplifier by this light irradiation.

Further, the image forming apparatus of the present invention includes a reference plate arranged near the platen, a fluorescent lamp for irradiating a document placed on the platen with light, and the fluorescent lamp. Moving means for moving the lamp relatively to the reference plate and the original document, and photoelectric conversion means for converting light from the reference plate and the original document by light irradiation of the fluorescent lamp moved by the moving means into an electric signal. An amplifier for amplifying the output signal of the photoelectric conversion means, an image forming means for forming an image based on the output signal corresponding to the light from the original by the light irradiation of the fluorescent lamp output from the amplifier, and the book. When the power of the device is turned on, the device is energized to heat the tube wall of the fluorescent lamp to a constant temperature, and when the temperature of the tube wall of the fluorescent lamp becomes a constant value by the heating of this heating means, Check ambient temperature Temperature detecting means, a lighting time determining means for determining a lighting time of the fluorescent lamp according to the tube wall temperature detected by the temperature detecting means, and a lighting time is determined by the lighting time determining means, Lighting control means for lighting the fluorescent lamp, time counting means for counting the lighting time determined by the lighting time determining means, and when this time counting means finishes counting the lighting time, the fluorescent lamp at that time Amplification factor setting means for irradiating the reference plate with light and setting the amplification factor of the amplifier to a predetermined value based on an output signal output from the amplifier by the light irradiation, and amplification of the amplifier by the amplification factor setting means. An extinguishing control means for extinguishing the fluorescent lamp when the rate setting is completed is provided.

Further, in the image forming apparatus of the present invention, a reference plate disposed near the document table, a fluorescent lamp for irradiating a document placed on the document table with light, and the fluorescent lamp. Moving means for moving the lamp relatively to the reference plate and the original document, and photoelectric conversion means for converting light from the reference plate and the original document by light irradiation of the fluorescent lamp moved by the moving means into an electric signal. An amplifier for amplifying the output signal of the photoelectric conversion means, an image forming means for forming an image based on the output signal corresponding to the light from the original by the light irradiation of the fluorescent lamp output from the amplifier, and the book. When the power of the device is turned on, the device is energized to heat the tube wall of the fluorescent lamp to a constant temperature, and when the temperature of the tube wall of the fluorescent lamp becomes a constant value by the heating of this heating means, Ambient temperature A lighting time determining means that determines the lighting time of the fluorescent lamp until the amount of light of the fluorescent lamp reaches about 70% of the stable time according to the known temperature detecting means and the ambient temperature detected by the temperature detecting means. When the lighting time is determined by the lighting time determination means, a lighting control means for lighting the fluorescent lamp, a time counting means for counting the lighting time determined by the lighting time determination means, and a time counting means When the counting of the lighting time is completed, the reference plate is irradiated with the light of the fluorescent lamp at that time, and the amplification factor of the amplifier is set to a predetermined value based on the output signal output from the amplifier by this light irradiation. And an extinction control means for extinguishing the fluorescent lamp when the amplification factor setting means completes the amplification factor setting.

[0012]

According to the present invention, the ambient temperature of the apparatus is detected, and the lighting time of the fluorescent lamp before setting the amplification factor of the amplifier for amplifying the output signal of the photoelectric conversion means is changed according to the detected ambient temperature. As a result, the light amount of the fluorescent lamp at the time of setting the amplification factor of the amplifier becomes almost the same regardless of the difference in ambient temperature, and the difference between the light amount at the time of setting the amplification factor and the light amount during image formation decreases, and Can be removed (difference in image density due to difference in ambient temperature).

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 schematically shows the configuration of a digital copying machine as an example of the image forming apparatus of the present invention.
This digital copying machine is roughly classified into a scanner unit (reading unit) 1 for optically reading image information of a document, and
The printer unit 2 is configured as an image forming unit that forms an image on a sheet by electrophotography according to an image signal read by the scanner unit 1 or supplied from an external device (not shown). .

The scanner unit 1 is placed on the original table 11 on which the original O to be copied is placed, an openable / closable original cover 12 for pressing the original O placed on the original table 11, and the original table 11. The fluorescent lamp 13 as a light source for illuminating the original O, and the CCD type line sensor 14 as photoelectric conversion means for photoelectrically converting the reflected light from the original O by the light irradiation from the fluorescent lamp 13.
have. Note that the fluorescent lamp 13 is provided with a lamp heater (not shown) as a heating means for heating the tube wall to a constant temperature.

Beside the fluorescent lamp 13, a reflector 15 for efficiently focusing the light from the fluorescent lamp 13 on the original O is provided.
Is provided. In addition, the fluorescent lamp 13 and the line sensor 1
4, a plurality of mirrors 16, 17, 18 for bending the light traveling from the original O to the line sensor 14, that is, the optical path through which the reflected light from the original O passes, and the reflected light. A lens unit 19 for focusing the light on the light receiving surface of the line sensor 14 is provided.

Then, the original O placed on the original table 11
The scanning system including the fluorescent lamp 13 and the mirrors 16 to 18 reciprocates along the lower surface of the document table 11 in the direction of arrow a, so that exposure scanning is performed during the reciprocation. In this case, the mirrors 17 and 18 are designed to move at half the speed of the mirror 16 so as to maintain the optical path length.

The reflected light from the original O by the scanning of the scanning system, that is, the reflected light from the original O by the light irradiation of the fluorescent lamp 13 is reflected by the mirrors 16 to 18 and then passes through the lens unit 19. The image of the original O is guided to the line sensor 14 and is formed on the light receiving surface of the line sensor 14.

The fluorescent lamp 13, the line sensor 14, the mirrors 16 to 18, and the lens unit 19 constitute a scanning unit 20. And fluorescent light 1
3, the reflector 15 and the mirror 16 are provided on the first carriage 21, the mirrors 17 and 18 are provided on the second carriage 22, and these carriages 21 and 22 are moved by motors not shown respectively. There is.

In the vicinity of the document table 11, the first carriage 21
A white reference plate 23 used for amplification factor setting processing and shading correction, which will be described later, is arranged at a portion facing the initial position (start position). In this case, the white reference plate 23 is irradiated with the light from the fluorescent lamp 13 prior to the optical scanning of the document O, and the reflected light is guided to the line sensor 14.

In the vicinity of the line sensor 14 in the scanning unit 20, a printed circuit board 24 incorporating a scanner control section (which will be described in detail later) for controlling the scanner section 1 is incorporated.
Is provided, and at a predetermined position (for example, a corner on the substrate 24) on the printed circuit board 24 where the influence of wind and heat is minimal, a thermistor 25 as a temperature detecting means for detecting the ambient temperature of the apparatus. Is provided.

The printer unit 2 has a cylindrical shape and is rotatable in a desired direction by a motor or the like (not shown). The printer unit 2 is charged to a desired electric potential and is irradiated with a beam light modulated according to print data. The photosensitive drum 31 as an image carrier on which an electrostatic latent image is formed
have.

Around the photosensitive drum 31, a charging device (charging device) 32 for charging the surface of the photosensitive drum 31, and on the surface of the photosensitive drum 31, print data (image information to be copied or output) is provided. A laser unit 33 for outputting a beam light (laser beam light) modulated by the
A developing device 34 for developing the electrostatic latent image formed on the electrostatic latent image by adhering toner to the electrostatic latent image, and a developed toner image on the photosensitive drum 31 on a paper P supplied from a paper feeding unit 39 described later. A transfer device (charging device) 35 for transferring the sheet P to a sheet, a peeling device (charging device) 36 for peeling the sheet P adsorbed on the photosensitive drum 31, and the like are sequentially arranged.

A cleaner unit 37 for removing the toner remaining on the surface of the photoconductor drum 31 on the downstream side of the peeling device 36 around the photoconductor drum 31, and
The potential on the photosensitive drum 31 is changed to the next image formation (printing).
An erasing device 38 for erasing is sequentially arranged.

Between the developing device 34 and the transfer device 35,
A paper feed unit 39 is provided to supply the paper P for transferring the toner image formed on the photoconductor drum 31 toward between the photoconductor drum 31 and the transfer device 35.

In the subsequent stage of the peeling device 36, the paper P on which the toner image is transferred is separated from the photosensitive drum 31 by the peeling device 36.
A fixing device 40 for fixing the toner image on the paper P and a conveying device 41 for conveying the paper P peeled by the peeling device 36 toward the fixing device 40 are arranged in the direction of peeling by the paper. Has been done.

The paper P, on which the toner image is fixed by the fixing device 40, is ejected to the paper ejection tray 43 by the paper ejection roller 42. FIG. 1 shows the control system of the digital copying machine configured as described above, mainly with respect to the scanner control section. That is, the CPU (Central
The processing unit) 51 controls the entire scanner unit 1, and includes a fluorescent lamp driving unit 52 for driving the fluorescent lamp 13 and a lamp heater 53 for heating the tube wall of the fluorescent lamp 13. Heater control unit 5 for drive control
4, a counter 55 as time counting means for counting the lighting time of the fluorescent lamp 13, a memory unit 56 for storing the control program of the CPU 51, various data, and the like;
A signal processing unit 57 that amplifies the output signal of the thermistor 25 and converts it into a digital signal is connected to each.

In addition, the CPU 51 amplifies the output signal of the line sensor 14, and an amplifier 58 whose amplification factor is variably set by a control signal from the CPU 51.
Also, an A / D converter 59 for converting the output signal of the amplifier 58 into a digital signal is connected.

Further, the CPU 51 is connected to a printer control unit 60 for controlling the printer unit 2. Although not shown in the figure, the printer controller 60 includes a CPU 51
An output signal of the line sensor 14 sent via the image sensor, that is, a memory for storing image information, an image processing unit for performing image processing such as enlarging and reducing the image information, and the like are included.

Next, in such a configuration, the operation of the main part, that is, the operation from the power-on to the ready state will be described with reference to the flow charts shown in FIGS.

First, when the power of this device is turned on (turned on), the CPU 51 drives the lamp heater 53 via the heater controller 54 to heat the tube wall of the fluorescent lamp 13. In this case, the tube wall temperature of the fluorescent lamp 13 is detected by a thermistor (not shown) in the lamp heater 53 and sent to the heater control unit 54 as a tube wall temperature detection signal.
While the power is turned on, the temperature is controlled so as to always reach a predetermined constant temperature (for example, 45 ° C.).

The graph shown in FIG. 5 shows the rising characteristics of the light quantity of the fluorescent lamp due to the difference in the ambient temperature. As is clear from the graph, the rising of the light quantity becomes slower as the ambient temperature becomes lower. There is. Line sensor 1
In order to set the amplification factor of the amplifier 58 for amplifying the output signal of No. 4 with almost the same light amount regardless of the difference in ambient temperature, the lighting time of the fluorescent lamp must be lengthened as the ambient temperature decreases.

Therefore, in the present embodiment, the thermistor 25 for detecting the ambient temperature in the scanner section 1 is provided, and the lighting time of the fluorescent lamp 13 is changed according to the difference in ambient temperature. This thermistor 25 is located at a position where it is not affected by wind and heat so as to prevent erroneous detection, and in the present embodiment, as described above, a predetermined position on the printed circuit board 24 in which the scanner control section with the least influence is incorporated. It is installed in the position.

Further, in general, as for the lighting time of the fluorescent lamp, if the light amount is 70% when the light amount is stable according to the experimental result, the copied image is not affected. Therefore, in this embodiment, the light amount is 70% when the light amount is stable.
The control is performed so that the fluorescent lamp 13 is turned on until it becomes. FIG. 6 shows the lighting time, that is, the lighting time with respect to the ambient temperature, and the corresponding data is stored in the memory unit 56 in advance as table data.

After the power is turned on, when the tube wall temperature of the fluorescent lamp 13 reaches a predetermined temperature (for example, 45 ° C.), the CPU 51, which recognizes it, fetches information on the ambient temperature detected by the thermistor 25 and The lighting time of the fluorescent lamp 13 corresponding to the ambient temperature is determined. That is, for example, if the detected ambient temperature is 21 to 25 ° C.,
The lighting time is determined to be 20 seconds by referring to the corresponding data in FIG. 6 stored in the memory unit 56.

When the lighting time is determined in this way, the CPU 5
1, the lamp heater 53 is turned off, the fluorescent lamp 13 is turned on via the fluorescent lamp driving unit 52, and the counter 55
The determined lighting time (20 seconds) is set to and the down count is started.

When the counting of the lighting time by the counter 55 is completed, the fluorescent lamp 13 is lit at 70% of the stable light amount at this time, and the white reference plate 23 is irradiated with the light. The CPU 51 takes in reference plate data by the reflected light from the white reference plate 23 from the output of the A / D converter 59. The CPU 51 sets the amplification factor of the amplifier 58 to an optimum value based on the acquired reference plate data, and then turns off the fluorescent lamp 13. The setting timing of the amplification factor is as shown in FIG. 7, and when the setting of the amplification factor is completed and the fixing device 40 is at the fixing possible temperature at this time, the ready state (copyable state) is set.

After the ready state is set in this manner, the document O is placed on the document table 11 and a copy key on an operation panel (not shown) is turned on to start a known copy operation.

As described above, according to the above-described embodiment, the thermistor 25 detects the ambient temperature in the scanning unit 20 of the scanner section 1, and the output signal of the line sensor 14 is amplified according to the detected ambient temperature. Amplifier 58
By changing the lighting time of the fluorescent lamp 13 before the amplification factor is set, the light amount of the fluorescent lamp 13 when the amplification factor of the amplifier 58 is set becomes substantially equal regardless of the difference in the ambient temperature. The difference with the light quantity during copying is reduced,
The influence on the image density, that is, the difference in image density due to the difference in ambient temperature can be removed.

[0039]

As described in detail above, according to the present invention, when the amplification factor of the amplifier for amplifying the output signal of the photoelectric conversion means is set, the light quantity of the fluorescent lamp becomes substantially equal regardless of the difference in ambient temperature. It is possible to provide an image forming apparatus capable of reducing the difference between the light amount at the time of setting the amplification factor and the light amount during image formation, and removing the influence on the image density.

[Brief description of drawings]

FIG. 1 is a block diagram mainly showing a scanner control section of a control system of a digital copying machine according to an embodiment of the present invention.

FIG. 2 is a side view schematically showing the configuration of a digital copying machine.

FIG. 3 is a flowchart for explaining the operation of the main part.

FIG. 4 is a flowchart for explaining the operation of the main part.

FIG. 5 is a light quantity characteristic diagram of a fluorescent lamp.

FIG. 6 is a diagram showing an example of correspondence data between ambient temperature and lighting time of a fluorescent lamp.

FIG. 7 is a timing chart for explaining an operation of a main part.

[Explanation of symbols]

1 ... Scanner section, 2 ... Printer section, 11 ... Original plate, 0 ... Original, 13 ... Fluorescent lamp, 14 ... Line sensor (photoelectric conversion means), 20 ... Scanning unit, 21, 2
2 ... Carriage, 23 ... White reference plate (reference plate), 2
5 ... Thermistor (temperature detecting means), 31 ... Photosensitive drum (image carrier), 32 ... Charging device, 33 ... Laser unit, 34 ... Developing device, 35 ... Transfer device, 39
...... Paper feed unit, 40 ...... Fixing device, 51 ...... CPU, 52
...... Fluorescent lamp drive unit, 53 ...... Lamp heater (heating means), 54 ...... Heater control unit, 55 ...... Counter (time counting means), 56 ...... Memory unit, 57 ...... Signal processing unit,
58 ... Amplifier, 59 ... A / D converter, 60 ... Printer control unit.

Claims (3)

[Claims] 1. A reference plate disposed in the vicinity of a platen, a fluorescent lamp for irradiating a document placed on the platen with light, and the fluorescent lamp for the reference plate and the document. Moving means for relatively moving with respect to each other, photoelectric conversion means for converting light from the reference plate and the original by light irradiation of the fluorescent lamp moved by the moving means into an electric signal, and an output of the photoelectric conversion means An amplifier for amplifying a signal, an image forming means for forming an image based on an output signal corresponding to the light from the original by the light irradiation of the fluorescent lamp output from the amplifier, and when the power of the apparatus is turned on. A heating unit that is energized to heat the tube wall of the fluorescent lamp to a constant temperature, and a temperature detection unit that detects the ambient temperature of the device when the tube wall temperature of the fluorescent lamp reaches a constant value by the heating of the heating unit. And this Time corresponding to the detected wall temperature at the temperature detecting means,
Fluorescent lamp control means for lighting the fluorescent lamp, and when the fluorescent lamp control means finishes the lighting time of the fluorescent lamp, the light of the fluorescent lamp at that time is irradiated to the reference plate, and the light irradiation causes An image forming apparatus comprising: an amplification factor setting unit that sets an amplification factor of the amplifier to a predetermined value based on an output signal output from the amplifier. 2. A reference plate arranged in the vicinity of a platen, a fluorescent lamp for irradiating a document placed on the platen with light, and the fluorescent lamp for the reference plate and the document. Moving means for relatively moving with respect to each other, photoelectric conversion means for converting light from the reference plate and the original by light irradiation of the fluorescent lamp moved by the moving means into an electric signal, and an output of the photoelectric conversion means An amplifier for amplifying a signal, an image forming means for forming an image based on an output signal corresponding to the light from the original by the light irradiation of the fluorescent lamp output from the amplifier, and when the power of the apparatus is turned on. A heating unit that is energized to heat the tube wall of the fluorescent lamp to a constant temperature, and a temperature detection unit that detects the ambient temperature of the device when the tube wall temperature of the fluorescent lamp reaches a constant value by the heating of the heating unit. And this A lighting time determining means for determining a lighting time of the fluorescent lamp according to a tube wall temperature detected by a temperature detecting means, and a lighting control for lighting the fluorescent lamp when the lighting time is determined by the lighting time determining means. Means, time counting means for counting the lighting time determined by the lighting time determining means, and when the time counting means finishes counting the lighting time,
Amplification factor setting means for irradiating the reference plate with the light of the fluorescent lamp at that time, and setting the amplification factor of the amplifier to a predetermined value based on the output signal output from the amplifier by this light irradiation, and the amplification factor. An image forming apparatus comprising: an extinguishing control unit for extinguishing the fluorescent lamp when the setting of the amplification factor of the amplifier by the setting unit is completed. 3. A reference plate arranged near the platen, a fluorescent lamp for irradiating a document placed on the platen with light, and the fluorescent lamp for the reference plate and the document. Moving means for relatively moving with respect to each other, photoelectric conversion means for converting light from the reference plate and the original by light irradiation of the fluorescent lamp moved by the moving means into an electric signal, and an output of the photoelectric conversion means An amplifier for amplifying a signal, an image forming means for forming an image based on an output signal corresponding to the light from the original by the light irradiation of the fluorescent lamp output from the amplifier, and when the power of the apparatus is turned on. A heating unit that is energized to heat the tube wall of the fluorescent lamp to a constant temperature, and a temperature detection unit that detects the ambient temperature of the device when the tube wall temperature of the fluorescent lamp reaches a constant value by the heating of the heating unit. And this A lighting time determining means for determining a lighting time of the fluorescent lamp until the light quantity of the fluorescent lamp reaches about 70% of the stable time according to the ambient temperature detected by the temperature detecting means, and the lighting time determining means When the lighting time is determined, a lighting control unit that lights the fluorescent lamp, a time counting unit that counts the lighting time determined by the lighting time determination unit, and the time counting unit finishes counting the lighting time. Then,
Amplification factor setting means for irradiating the reference plate with the light of the fluorescent lamp at that time, and setting the amplification factor of the amplifier to a predetermined value based on the output signal output from the amplifier by this light irradiation, and the amplification factor. An image forming apparatus comprising: an extinguishing control unit for extinguishing the fluorescent lamp when the setting of the amplification factor of the amplifier by the setting unit is completed.