JPS60163476A - Light source stabilization device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

TECHNICAL FIELD The present invention relates to a light source stabilizing device for stabilizing the output of a light emitting source such as a laser beam.

BACKGROUND ART Conventionally, some apparatuses of this type perform light intensity control in order to stabilize the laser light intensity during recording. For example, Japanese Patent Application No. 55-7643 proposes a method of detecting the back beam of a laser and controlling the amount of laser light in accordance with the amount of light detected.

However, although the method of detecting the laser back beam and applying feedback could stabilize the amount of light, it was not possible to stabilize the emission wavelength. For this reason, if the sensitivity of the photoreceptor exposed to laser light changes depending on the wavelength,
Even if the amount of light is stabilized, the density of the recorded image changes, and there is a drawback that it is not possible to record an image with a constant density.

Furthermore, when the ambient temperature changes, the sensitivity of the photodetecting element changes, resulting in a change in the amount of laser light.

the purpose The object of the present invention is to eliminate the drawbacks mentioned above.

Another object of the present invention is to provide a light source stabilizing device that can provide stable beam output.

Another object of the present invention is to provide a light source stabilizing device that stabilizes both the light intensity and emission wavelength of a beam.

Another object of the present invention is to provide a light source stabilizing device that prevents temperature drift of the light receiving element by simultaneously heating the light emitting element and the light receiving element and controlling the temperature thereof.

A further object of the present invention is to provide an image recording apparatus that can perform excellent image recording using a stable beam.

Another object of the present invention is to provide a light source stabilizing device that is simple in construction and inexpensive.

A further object of the present invention is to provide a highly safe light source stabilizing device.

Example Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows an embodiment in which the light source stabilizing device according to the present invention is applied to a beam recording device, in which a laser beam L1 generated from a semiconductor laser generator 1 is converted into a parallel beam L2 by a collimator lens 2. The light then enters a deflector 3 in the form of a rotating polygon mirror that rotates at a constant speed in the direction of arrow F.

The laser beam L3 deflected by the rotating polygon mirror 3 is directed to a photosensitive drum 5 constituting an electrostatic recording device by an imaging lens 4.
imaged on top. This imaging spot moves in the direction of arrow P according to the rotation of the rotating polygon mirror 3.

Therefore, by rotating the rotating polygon mirror 3 at a high speed and rotating the photosensitive drum 5 in a certain direction at a constant speed, the entire area of the photosensitive drum 5 can be scanned with the laser beam L3.

6 is a beam detector disposed outside the information recording area of the photosensitive drum 5, and the laser beam L3 is transmitted to the beam detector 6.
Detects the arrival of the synchronizing signal and forms a synchronizing signal (BD double signal. This synchronizing signal is applied to the information processing circuit 7, and a recording signal is applied to the semiconductor laser generator 1 at a timing controlled by the synchronizing signal. do.

Therefore, the laser generator 1 emits a laser beam Ll modulated by the recording signal. Since such control is widely known, for example, in Japanese Patent Application Laid-open No. 51-89346, detailed explanation will be omitted here.

The laser beam L3 modulated by the recording signal is irradiated onto the photosensitive drum 5 in this way, but since the photosensitive drum 5 has been uniformly charged in advance by a charger (not shown), the laser beam L3 is An electrostatic latent image corresponding to the irradiation is formed by the irradiation, this electrostatic latent image is visualized by a developing device (not shown), this developed image is transferred to paper etc. by a transfer device (not shown), and this transfer is performed. By fixing the printed paper using a fixing device (not shown), it is possible to obtain a recording paper on which an image corresponding to the recording signal is recorded. Incidentally, since the above-mentioned sequence is well known, a detailed explanation thereof will be omitted.

As mentioned above, the semiconductor laser generator l emits the laser beam (front beam) Ll forward and at the same time emits the back beam BB backward. The element it receives the light and forms a detection signal according to the beam intensity. Note that, for example, a photodiode or the like is suitable as the photodetecting element. This detection signal is applied to the control circuit 12 to control the beam emission intensity of the semiconductor laser generator l.

The WtJz diagram shows the aforementioned control circuit 12 and information processing circuit 7.
2 is a circuit diagram illustrating in more detail the light amount control device included in a part of the device, in which 13 is a reference level setting circuit that generates a reference signal of a constant potential, and 14 is a circuit diagram of a photodetection circuit 11a including a photodetection element 11. Detection signal and reference level setting circuit 1
This is a comparison circuit that compares the detection signal with three reference signals and stops the counting operation of the counter 16 when the detection signal becomes larger. 15 is an oscillation circuit that oscillates a signal of a constant frequency, and 16 is a counter that is connected to the oscillation circuit 15 and counts the oscillation signal. Counting starts when a timing signal is applied to the counter 16 from the input terminal T1. However, if the counting operation does not stop due to the output of the comparator circuit 14 even after counting up to a predetermined value, a one-digit overflow signal is derived from the signal line SCI to clear the counter and stop the counting operation, and at the same time, the output of the comparator circuit 14 Stop comparison operation.

17 is D that converts the count value of the counter 16 into an analog quantity.
/A conversion circuit 18 is connected to D/A conversion circuit 17,
A current amplifying circuit 19 amplifies the obtained analog signal, and 19 is a switch circuit that operates on/off according to the recording signal applied from the input terminal T2. is applied to turn on the switch circuit 19, a current is applied to the semiconductor laser generator l via the signal line SLI, and when a ≠digital °°0°' signal is applied to terminal T2 and the switch circuit 19 is turned off, the current is applied to the semiconductor laser generator l via the signal line SLI. The structure is such that no current is applied to the semiconductor laser generator l.

To further explain the operation of the beam recording device configured as described above, when a timing signal is applied from the input terminal T1 (for example, this timing signal is transmitted when the beam recording device has completed recording an image equivalent to one page). (deduced during the idle time between recording of the next page), the switch circuit 19 is held in the on state, and after the counter 16 is cleared, the counting operation is started.

Therefore, as the callan 16 performs counting, the count value Na gradually increases, so the signal line SLI
The current above also increases in response to this, and as a result, the intensity of the emitted beam from the semiconductor laser generator also gradually increases. can be continued.

In this way, if the detection signal becomes larger than the reference signal when the counter 16 reaches the predetermined count value Na, the counting operation is stopped by the output of the comparison circuit 14,
The counter 16 holds this count value Na until the next timing signal is applied, and the ON state of the switch circuit 19 is cleared.

Therefore, a current Ia corresponding to this count value Na is derived to the signal line S L l l, and when a recording signal is applied to the input terminal T2, the semiconductor laser generator l is activated in accordance with this current Ia. Driven.

When the counter stop signal is not derived from the comparator circuit 14 even if the counter 16 reaches the preset count value N2 due to a failure in the photodetector circuit 11a or the like, the counter 16
derives an overflow signal to the signal line SCIJ2, stops the operation of the comparator circuit 14, clears the ON state of the switch circuit 19, and clears the counter 16 to set the count value N1 in the initial state. Return to Therefore, when the current on the signal line SLI becomes large and the semiconductor laser generator 1 is about to be damaged, the drive current is reduced and damage to the semiconductor laser generator 1 can be prevented in advance.

FIG. 3 shows another embodiment, in which w42
Oscillation circuit 15 shown in the figure. Instead of the counter 16 and the D/A converter 17, a ramp wave generation circuit 20 whose output level increases with the passage of time is used, and a ramp wave generation circuit 20 starts generating a ramp wave by applying a timing signal to the input terminal T1. The current output level is held at the output.

In this example, the operation of other circuits is the same as in the embodiment of FIG. 2, and the same circuits as in FIG. 2 are designated by the same numbers.

In the embodiment shown in FIGS. 2 and 3 below,
The timing signal described above is derived before the laser beam L1 finishes recording a certain page on the photosensitive drum 5f and starts recording the next page, and starts recording the corresponding page after the light intensity adjustment is completed. However, as another embodiment, a timing signal is derived from when the laser beam L1 reaches the beam detector 6 until it reaches the left end WS of the transfer area (WS, -WT) on the photosensitive drum 5F. , and the light amount adjustment may be completed before the beam reaches the left end WS.

In each of the embodiments described above, the back beam BB of the semiconductor laser generator l is used as the incident light of the photodetector circuit 12.
However, it is also possible to guide the front beam L1 to the photodetection circuit using an optical system only for a part of the front beam L1 or during the light amount control period.

Next, the temperature control circuit 24 shown in FIG. 1 will be described. As shown in FIG. 1, the semiconductor laser generator 1 and the photodetector 11 are mounted on a base 211 . (A metal plate made of aluminum, copper, etc. is suitable as the base 21.) A heating element 22 is attached in close contact with this base 21, and a temperature detection element 23 is further attached to the base 21. Install closely. This temperature detection element 23 can be, for example, a thermistor or a thermocouple. Note that in order to accurately detect the temperature of the semiconductor laser, it is preferable to attach a temperature detection element near the semiconductor laser. The heating element 22 can be, for example, a nichrome heater insulated with silicone rubber, mica, or the like.

The temperature control circuit 24 is a circuit that changes the current of the heating element 22 according to the output detected by the temperature detection element 23, and a detailed example of this circuit is shown in FIG.
25 and 26 are input terminals that connect the temperature detection element 23 to the circuit 24; 27 is a resistor that supplies the power supply Vcc to the temperature detection element 23;

28 and 29 are voltage dividing resistors that determine the reference voltage, 30 is an operational amplifier, 31 is a feedback resistor of the operational amplifier 30, and 32
33 is a current amplifying transistor to which the output of the operational amplifier 30 is supplied via the resistor 32, and is connected to the power supply Vcc. 34 and 35 are output terminals connecting the heating element 22 between the transistor 33 and ground potential.

When the temperature of the base 21 is low, the resistance of the temperature sensing element 23 increases and the voltage at the input terminal 25 increases. When the voltage becomes higher than the reference voltage determined by voltage dividing resistors 28 and 29,
Operational amplifier 30 operates to increase the collector current of transistor 33. As a result, the current of the heater 22 increases and the temperature of the base 21 rises by a bit. On the other hand, when the temperature of the base 21 is high, the collector current decreases compared to when the base 21 temperature is low. As a result, the temperature of the base 21 is kept constant. Therefore, when controlling the amount of light, fluctuations in sensitivity due to temperature changes of the photodetecting element can be prevented and the amount of light can be stabilized. At the same time, it is possible to prevent fluctuations in the emission wavelength of the light emitting element due to temperature changes. Therefore, even if there are variations in the wavelength sensitivity characteristics of the photoreceptor, stable image density can be ensured. By the way, this constant temperature is called a control temperature. Therefore, this control temperature is determined by the voltage dividing resistors 28 and 29. Since semiconductor lasers are sensitive to heat, when controlling the heating temperature, the control temperature is set to be approximately equal to the maximum ambient temperature (for example, 45° C.).

Here, the maximum ambient temperature refers to the maximum ambient temperature of a device (semiconductor laser) when a semiconductor laser is used.

By the way, it is also possible to use a single element that uses the Beltier effect to perform both laser heating and cooling, but in this case, the Beltier element is expensive.

In addition, the Beltier element will heat up if the direction of the current is not switched.
Control was complicated because the cooling could not be switched, but
In the case of the present invention, since only heating is required, an inexpensive heater can be used, and the drive circuit can also be of simple construction, so that the device can be constructed at low cost.

As detailed above, by controlling the temperature of the light emitting element and the photodetecting element placed on the same base at the same time at the maximum ambient temperature and controlling the light amount, the light amount and emission wavelength of the light emitting element can be stabilized with an inexpensive configuration. I was able to make it happen.

As another embodiment according to the present invention, as shown in FIG. 5, the resistor 29 in FIG. 4 is replaced with a variable resistor 29', and a service person, for example, can change the resistance value depending on the area where the device is used.
It may be configured to switch the control temperature. For example, when the device is used in a region with a low temperature, by setting the control temperature low, the semiconductor laser and the photodetection element can reach the control temperature more quickly. Therefore, the device can be made ready (usable) in a short time.

Furthermore, when the control temperature is changed, the amount of light may be changed at the same time. This switching of the amount of light is achieved by interlocking the reference level setting circuit 13 shown in FIG. 2 with the variable resistor 29'.
It is sufficient to switch the reference signal according to the change in the resistance value of '.

Normally, the sensitivity of a photosensitive drum changes depending on the temperature, so a stable image can be obtained by changing the amount of light at the same time as the control temperature depending on the region.

Furthermore, in all the embodiments described above, it is preferable to control the light amount after the semiconductor laser and the photodetection element reach the control temperature, because as in this example, one page of image recording is completed and the next In a device that adjusts the light intensity during idle time while recording one page, if the light intensity is controlled because the semiconductor laser and photodetection element have not reached a certain temperature (control temperature), the image recording of one page will not be possible. This is because there is a risk that the temperature of the semiconductor laser changes during the process, the amount of light changes accordingly, and the image density changes.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one example of the configuration of a beam recording device to which the present invention is applied, FIGS. 2 and 3 are diagrams showing two examples of a light amount control circuit, and FIG. 4 is a diagram showing a temperature control circuit according to the present invention. FIG. 5 is a diagram showing an example of the configuration of a temperature control circuit in another embodiment. Here, 1 is a semiconductor laser, 2 is a collimator lens, 3 is a rotating polygon mirror, 5 is a photosensitive drum, 7 is an information processing circuit, 11
is a photodetection element, lla is a photodetection circuit, 21 is a base, 2
2 is a heating element, 23 is a temperature detection element, and 24 is a temperature control circuit. Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] a light emitting means; a heating means for heating the light emitting means;
temperature detection means for detecting the temperature of the light emitting means;
A light source stabilizing device comprising: temperature control means for controlling the heating means according to the output of the temperature detection means; and switching means for switching the control temperature of the temperature control means.