JPH0555875B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a light amount control device for a laser emitting means.

Prior Art Conventionally, control is performed to maintain the amount of light emitted by a laser emitting means at a predetermined value. For example, the control includes controlling the temperature of the laser emitting means to a predetermined temperature so as to eliminate changes in the amount of light emitted due to changes in ambient temperature, or stabilizing the amount of light emitted by detecting the amount of light emitted and feeding it back to the light emitting means.

However, for example, in a printer device that uses laser light, the recording material that is irradiated with laser light has different effects of temperature and its photosensitivity characteristics, so it is not possible to perform optimal control by simply keeping the amount of laser light emitted constant. It doesn't mean that it was.

Purpose The present invention has been made in view of the above points, and includes a semiconductor laser (semiconductor laser generator 1 of the embodiment (see Figs. 1 and 2) that emits laser light that is on/off modulated by a recording signal. ), forced lighting signal output means (flip-flop 15 (FIG. 2)) for outputting a forced lighting signal for lighting the semiconductor laser regardless of the recording signal; Light amount detection means (light detection circuit 11) that detects the amount of laser light
(corresponding to Fig. 2)), detection means for detecting a signal representing the sensitivity of the laser irradiated member (corresponding to the select circuit 37 (Fig. 4)), and a reference value capable of generating a plurality of different reference values. A generating means (corresponding to the reference value generating circuits 31 to 33 (FIG. 4)) selects a reference value from the plurality of reference values according to the sensitivity of the laser irradiated member represented by the signal detected by the detecting means. selection means (AND circuits 39-4
1. Comparison means (corresponding to the OR circuit 42 (FIG. 4)) for comparing the reference value selected by the selection means and the output from the light amount detection means (corresponding to the comparators 34 to 36 (FIG. 4)); (corresponding), the current applied to the semiconductor laser is changed when the forced lighting signal is on, and the current applied to the semiconductor laser is changed when the output of the light amount detection means reaches the selected reference value. Therefore, the present invention includes applied current control means (corresponding to the counter 16 (FIG. 2)) for setting the current applied to the semiconductor laser when the recording signal is turned on after the forced lighting signal is turned off. By doing so, in a device that controls the amount of laser light when a recording signal is turned on, changes in the amount of laser light caused by temperature changes etc. are removed and the laser light is emitted with a stable amount of light, but the stability is deteriorated. It is an object of the present invention to provide a light amount control device that can perform optimal light amount control according to a member to be irradiated with a laser.

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

FIG. 1 shows an embodiment in which a light amount control device according to the present invention is applied to a beam recording device.

A laser beam L generated by a semiconductor laser generator 1 is collimated by a collimator lens 2, and is incident on a rotating polygon mirror 3 that rotates at a constant speed in the direction of an arrow F.

The laser beam deflected by this rotating polygon mirror 3 constituting a deflector is imaged by an imaging lens 4 onto a photosensitive drum 5 having predetermined photosensitivity characteristics constituting an electrostatic recording device, and this imaging spot is moves in the direction of arrow P according to the rotation of the rotating polygon mirror 3. Therefore, if the rotating polygon mirror 3 is rotated at high speed and the photosensitive drum 5 is rotated in a constant direction at a constant speed, the entire area of the photosensitive drum 5 can be scanned with a laser beam.

Note that the photosensitivity characteristics of the photosensitive drum 5 vary depending on the quality of materials and environment during the manufacturing process of the drum, and when the drum is replaced due to fatigue or damage to the photosensitive drum, the characteristics of the newly installed drum may vary. It is necessary to change the output of the semiconductor laser generator 1 according to the photosensitivity characteristics.

Reference numeral 6 indicates a beam detector provided outside the information recording area of the photosensitive drum 5, which detects the arrival of the laser beam to the beam detector 6, forms a synchronization signal, and processes this synchronization signal for information processing. The signal is applied to the circuit 7, and a recording signal is applied to the semiconductor laser generator 1 at a timing controlled by the synchronization signal. As a result, the laser generator 1 emits a laser beam modulated by the recording signal.

The laser beam 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 irradiation with the laser beam An electrostatic latent image is formed according to 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 the transferred paper is By fixing the image using a fixing device (not shown), it is possible to obtain recording paper on which an image corresponding to the recording signal is recorded.

As mentioned above, the semiconductor laser generator 1 emits the laser beam (front beam) L toward the front and at the same time emits the back beam BB toward the rear.
The BB receives light in the photodetection circuit 11 to form a detection signal corresponding to the beam intensity, and applies this detection signal to the control circuit 12 to control the beam output intensity of the semiconductor laser generator 1.

FIG. 2 shows the control circuit 12 and the information processing circuit 7.
13 is a circuit diagram illustrating in more detail the light amount control device included in a part of the device, 13 is a reference level setting circuit that generates reference signals of three different potentials;
4 is a comparison circuit, and 15 is a flip-flop, which compares the magnitude of the detection signal A from the photodetection circuit 11 and three reference signals from the reference level setting circuit 13 according to the drum sensitivity signal DS. , if the detection signal becomes larger, flip-flop 1
Outputs signal C to reset 5. 20 is an oscillation circuit that oscillates a signal of a constant frequency; 16 is a counter that is connected to the oscillation circuit 20 and counts the oscillation signal; it is cleared by the timing signal TS, and is set by the timing signal TS; Counting is performed when a set signal (enable signal) from the flip-flop 15 is input, and when the enable signal is turned off, the count value at that time is held. 17 is the counter 1
A D/A conversion circuit 18 for converting the count value of 6 into an analog quantity is connected to the D/A conversion circuit 17,
A current amplification circuit that amplifies the obtained analog signal,
19 is a switch circuit that operates in response to the high logic level output applied from the OR circuit 21; when the switch circuit 19 is turned on, the current from the current amplification circuit 18 is applied to the semiconductor laser generator 1; , when it is off, the semiconductor laser generator 1 is controlled so that no current is applied to it.

The operation of the circuit shown in FIG. 2 will be explained with reference to the time chart shown in FIG.

In FIG. 2, flip-flop 15 is set by timing signal TS. At the same time that the flip-flop 15 is set, the counter 16 is reset once and starts counting by the set output of the flip-flop 15. Further, the output of the OR circuit 21 also becomes a high logic level, and the current switch 19 is turned on. As a result, the count value of the counter 16 becomes the current value that is passed through the laser generator 1 through the D/A conversion circuit 17, current amplifier 18, and current switch 19. In other words, counter 16
As the count increases, the value of the current flowing through the laser generator 1 also increases. And the laser current of laser generator 1 is the threshold for laser generation (=I _TH )
When it reaches , the laser generator 1 starts emitting light.

When the laser generator 1 starts emitting light, the light detection circuit 11 converts the amount of light into an amount of electricity. The comparator circuit 14 then compares the reference value of the reference level circuit 13 with the output of the photodetector circuit 11, and determines whether or not to reset the flip-flop 15. When the output of the photodetector circuit 11 reaches the reference value of the reference level circuit 13 and the flip-flop 15 is reset, the counter 16 stops counting up and holds the count value at that time. Further, the output of the OR circuit 21 is also switched to the image signal VIDEO, and the laser generator 1 blinks in synchronization with the image signal VIDEO.
In other words, the current value flowing through the laser generator 1 is once returned to the initial value by the timing signal TS, and the current value is gradually increased, so that the amount of laser light reaches the reference value according to the drum sensitivity determined by the reference level circuit 13. When the count value is reached, the counter 16 stops counting up and holds the count value. After this, the laser generator 1 maintains a constant light intensity until the flip-flop 15 is set by the next input timing signal TS. In this way, by inputting the timing signal TS, it is possible to cause the laser generator 1 to output an amount of light emitted according to the drum sensitivity.

FIG. 4 shows detailed circuit configurations of the comparison circuit 14 and reference level circuit 13 shown in FIG. 31 to 33 are 3 depending on the photosensitivity characteristics of the photosensitive drum that can be mounted.
This is a reference value generation circuit that outputs reference values H, M, and L of voltage levels that are prepared in advance, and each has variable resistors VR1 to VR3 for fine adjustment. The outputs H, M, and L of the reference value generation circuits 31 to 33 are independently compared with the output A of the photodetection circuit 11 in comparators 34 to 36. Each comparator 34~
The comparison result of 36 is applied to AND circuits 39 to 41 of the selector circuit 37. The selector circuit 37 selects comparators 34 to 3 according to a drum sensitivity signal SD indicating the light sensitivity characteristics of the attached photosensitive drum.
One of the six outputs is selected.

The drum sensitivity signal SD can be obtained by the operator operating a lever etc. installed on the device, or
Alternatively, it can be obtained from a microswitch or the like that is operated by the attachment of the photosensitive drum 5 or photosensitive drum unit, and three types of photosensitivity characteristics are expressed as 2-bit signals. This 2-bit signal is sent to the AND circuit 39 directly or via inverting circuits 43 and 44.
~41. That is, a signal of "00" is assigned to a high-sensitivity drum, a signal of "01" is assigned to a medium-sensitivity drum, and a signal of "11" is assigned to a low-sensitivity drum. This allows comparator 3 to be used if a high sensitivity drum is installed.
The output of No. 4 is valid, the comparator 35 is valid when a medium-sensitivity drum is installed, and the output of the comparator 36 is valid when a low-sensitivity drum is installed. AND circuit 39-41
The output of is applied to the OR circuit 42, and the output of the OR circuit 42
The output of the flip-flop 15 becomes the reset signal C.

In this way, by setting the reference value voltages H, M, and L corresponding to the sensitivity of each photoreceptor drum in the reference value voltage generation circuits 31, 32, and 33, the comparators 34, 35, and 36 are connected to the photodetector circuit 11. The detected light amount voltage A and each reference value H, M, L are compared. The selector circuit 37 includes comparators 34 to
36 comparison results are communicated. On the other hand, a 2-bit drum sensitivity signal SD is input to the selector circuit 37 from the photosensitive drum unit, and this signal SD
One of comparators 34 to 36 depending on
Only one comparator output is validated (selected), and only the comparison result of that comparator is sent to the flip-flop 15 as the output signal C of the selector circuit 37, and control is performed to keep the laser light amount at a constant value.

That is, detecting the amount of light emitted from the laser generator 1,
The circuit feeds back the detected value to the laser generator 1 and stabilizes the light intensity.The circuit has several comparators with different reference value voltages, and the comparison results of the comparators are used to calculate the photosensitivity of the attached photosensitive drum. By switching according to the characteristics, several levels of light intensity suitable for the photosensitive drum can be obtained.

In addition, the three reference values set in advance are not necessarily suitable for all drums, and in this case, the fine adjustment circuit consisting of variable resistors VR1 to VR3 provided in each reference value generation circuit 31 to 33 is further operated. By doing so, it is possible to obtain the optimum amount of light emission depending on the photosensitivity characteristics.

In the embodiments described above, switching is controlled based on the photosensitivity characteristics of the photosensitive drum, but the selection circuit 37 may also be operated based on the characteristics of the charger, the developer, the lens, the filter, etc. Furthermore, the amount of light may be switched based on information other than the photoreceptor drum sensitivity, such as temperature or humidity.

Further, in this embodiment, the light intensity was switched in three stages, but it goes without saying that if n reference value generation circuits and comparators are provided, the light intensity can be switched in n stages.

Furthermore, instead of providing a plurality of reference value generation circuits and comparators, the reference value applied to the comparator may be changed by a drum sensitivity signal or the like.

In this embodiment, the back laser of the laser generator is detected, but the front laser may also be detected, and the beam detector can also be used as a detector.

Effects As explained above, according to the present invention, in a device that controls the amount of laser light when a recording signal is turned on, changes in the amount of laser light due to temperature changes etc. are removed and a stable light amount is maintained. While emitting light, it is possible to perform optimal light amount control according to the laser irradiated member without deteriorating its stability.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a beam recording device to which the present invention is applied, FIG. 2 is a circuit diagram showing an example of a circuit configuration for controlling the amount of light, and FIG. 3 is a timing chart showing the output status of each part of the circuit shown in the second diagram. 4 are detailed circuit diagrams of a part of the circuit shown in the second diagram, in which 1 is a semiconductor laser generator, 5 is a sensitive drum, 6 is a beam detector, 11 is a photodetection circuit, and 13 is a reference level circuit. ,
14 is a comparison circuit, DS is a drum sensitivity signal, TS is a timing signal, 31 to 33 are reference value generation circuits, 3
4 to 36 are comparators, and 37 is a selection circuit.

Claims (1)

[Scope of Claims] 1. A semiconductor laser that emits laser light that is modulated on and off by a recording signal; A forced lighting signal output means that outputs a forced lighting signal for lighting the semiconductor laser regardless of the recording signal; A light amount detection means for detecting the amount of laser light output from a semiconductor laser; a detection means for detecting a signal representing the sensitivity of a member to be irradiated with the laser; a reference value generation means capable of generating a plurality of different reference values; and the plurality of standards. selection means for selecting a reference value according to the sensitivity of the laser irradiated member represented by the signal detected by the detection means from among the values; comparing the reference value selected by the selection means with the output from the light amount detection means; comparing means for changing the current applied to the semiconductor laser when the forced lighting signal is on, and changing the current applied to the semiconductor laser when the output of the light amount detection means reaches the selected reference value; Accordingly, the light amount control device is characterized by comprising applied current control means for setting the current applied to the semiconductor laser when the recording signal is turned on after the forced lighting signal is turned off.