JPH01179058A - Method for controlling light quantity - Google Patents

Abstract

PURPOSE:To prevent the occurrence of unbalance in the deterioration of a photosensitive body by starting a power set action synchronously with a gate signal which acts with a synchronizing detection signal. CONSTITUTION:After inputting a power set start signal, the power set action is started synchronously with the gate signal from a gate signal generation part 22 which acts with the synchronizing detection signal of a synchronizing detection part 18. Therefore, the on/off of a laser diode signal is performed synchronously with the on/off of the gate signal so as to make the laser diode emit light in a photosensitive body scanning area, and exposure in one scanning line is uniformized. Thus, the deteriorated part of the photosensitive body is prevented from being unbalanced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a light amount control method for a laser printer having a laser power setting mechanism.

(Prior art) As the speed and density of laser printers increases, the rotational speed of the laser beam deflector has increased, and the scanning time for one line has accordingly become shorter, making it easier to scan a non-photoreceptor area within the laser scanning area. The time will also be shorter.

In addition, the reference clock of the laser power set mechanism (UP
/DOWN counter count speed) has the characteristic that it is uniformly determined by the responsiveness of a part of the power monitor.

During the laser power setting, the laser diode is turned on, so in order to prevent deterioration of the photoreceptor, it is desirable to perform the power setting within the time it takes to scan the non-photoreceptor area. As the scanning time of the non-photoreceptor area has become shorter with the increase in density, a problem has arisen in which power cannot be set within that time. In other words, it is difficult to adjust or readjust the laser power to a predetermined value.

Therefore, conventionally, as shown in the power set timing chart of FIG. 8, when the power set start signal C from the CPU is input to the enable signal generator, the enable signal g is set to H level (gl), and the laser diode signal is f
The laser diode is turned on with d turned on at H level (f), and the monitor signal d changes from L level to H level (
dl), the end signal e from the end signal generator causes the laser diode signal f from the enable signal generator to
is set to an OFF state at L level (f2), and at the same time, the enable signal g is also set to L level (g2) to terminate lighting of the laser diode.

In other words, power setting has been performed regardless of the photoreceptor scanning area (the H level period of the gate signal) and the non-photoreceptor scanning area (the L level period of the gate signal).

Therefore, - within the scanning line (81-a of synchronization detection signal a)
, period), there was a drawback that the portion of the photoreceptor deteriorated was unevenly distributed due to the power setting.

(Problems to be Solved by the Invention) As mentioned above, even when the speed and density are increased, it is important that the photoreceptor is exposed uniformly by the power set. Since the power setting is performed as shown in FIG. 8 regardless of the scanning area or non-scanning area of the body, there is a drawback that the laser beam exposure is biased to one side within the scanning line and becomes non-uniform.

SUMMARY OF THE INVENTION The present invention aims to eliminate the above-mentioned drawbacks of the prior art, and to - uniformize the exposure of the photoreceptor within a scanning line to produce high-quality images.

(Structure and operation) In order to achieve the above object, the present invention provides a laser printer having a laser power set mechanism that synchronizes with a gate signal from a gate signal generator that operates with a synchronization detection signal after inputting a power set start signal. This feature is characterized in that the power set operation is started.

The present invention performs 0N10FF of the laser diode signal in synchronization with the gate signal 0N10F'F, exposes the laser diode in the photoreceptor scanning area, and uniformizes the exposure within the -scanning line.

(Embodiment) FIG. 7 is a sectional view showing a schematic configuration of a laser printer in which the present invention is implemented. For an overview of this operation, please refer to the paper feed bag W.
The recording paper 2 fed in the direction of arrow A from 11 is timed by a pair of registration rollers 3 and is transported to a latent image carrier consisting of a drum-shaped photoreceptor 4. The photoreceptor 4 is rotationally driven in a counterclockwise direction, the surface of which is charged by a charging charger 5, and irradiated with laser light from a laser optical system 6 to form an electrostatic latent image on the photoreceptor.

This latent image is the developer bag V! 17, the toner forms a visible image, and this visible image is transferred to the recording paper 2, which is conveyed to the photoreceptor 4, by the transfer charger 8.

The transferred visible image on the recording paper is fixed by a fixing device 9. Then, the recording paper 2 that has left the fixing device is fed to the paper discharge section 11 in the direction of arrow B. On the other hand, residual toner is removed from the photoreceptor 4 after the visible image has been transferred by a cleaning device having a cleaning blade 12 . The toner removed from the photoreceptor is collected in a toner collection tank 13 and stored there. Note that IO is the printer body, 14
is the controller.

FIG. 1 shows a block diagram of a printer control section 15 of an embodiment of the present invention implemented in the laser printer described above, and FIG. 2 is a schematic diagram of the construction of the laser optical system of FIG. 1.

A controller 14 of the printer main body 10 is connected to a host computer 16 , and print data sent from the host computer 16 is converted into a video signal by the controller 14 and sent to a print control section 15 . The print control section 15 includes a CPU 15A, a power adjustment section 21, and a gate signal generation section 22. Power adjustment section 2
1, the laser diode 20 of the laser optical system 6 is set to 0N10FF in accordance with the video signal, and as shown in FIG. A laser beam is scanned (main scan) on the body 23 to form an electrostatic latent image on the photoreceptor.

Further, the synchronization detection section 18 generates a synchronization detection signal once for each line scan, and sends it to the gate signal generation section 22.
Power set of the above video signal (light emission start timing)
control. Further, the power monitor part 19 monitors the light emission of the laser diode 20. In other words, even if the current flowing through the laser diode is constant, the light emitting power of the laser diode changes over time and varies between individuals, so the power is not constant. To obtain a stable image, the light emitting power Control is required to keep it constant.

FIG. 3 shows a control circuit for the laser power adjustment section 21 and the power monitor part 19 of FIG. 1.

The laser power adjustment section 21 includes an UP/DOWN counter 21A, a D/A converter 21B, an operational amplifier 21G,
It consists of a transistor 21D. The power monitor portion 19 includes a pin photodiode 19A that is in contact with the laser diode 20 and monitors its power, an operational term multiplier 19B, a comparator 190, and a volume 19G that adjusts the laser power to a predetermined value. 24 is a NOR gate, which takes the logical sum of the laser diode signal and the video signal, and controls the laser diode 20 to 0N10.
FF. Reference numeral 25 denotes a termination signal generating section, which outputs this termination signal (FIG. 4g) when the monitor signal (FIG. 4g) changes from L level to H level (dl). Reference numeral 26 denotes an enable signal generator, which generates a laser diode signal (
The laser diode 20 emits light (ON state) by changing the enable signal (FIG. 4 f) and the enable signal (FIG. 4 g) from L level to H level (fi)-(gz), and the gate signal changes from H level to L level. (b2), the laser diode signal changes from H level to L level (f2)
, the laser diode 20 stops emitting light (OF
F state).

Next, to describe the operation, in response to the power set start signal (FIG. 4g) from the CPU 15A in FIG. ) is input to the UP/DOWN counter 21A of the laser power adjustment section 21. This counter 21A is enabled (the enable signal is at H level), and if the monitor signal (g in FIG. 4) is at H level, the UP/DOWN counter 21
A counts down in synchronization with the clock signal GK, and counts up if the monitor signal is at L level. The output of this counter 21A is input to the D/A converter 21B, and when the counter counts down, the D/A converter output current becomes smaller, and the operational amplifier 21C and transistor 21D increase the current of the laser diode 20 to increase the light emitting power. increase. Similarly, when the counter counts up.

It is designed to reduce the luminous power. In this way, the monitor signal (Fig. 4g) detected by the bin photodiode 19A is transmitted to the UP/DOWN counter 21A.
is input to the end signal generating section 25.

Here, the output of the monitor signal is controlled by the operational amplifier 19B and the comparator 190 so that it is output as an H level if it is lower than a predetermined value adjusted by the volume 19C, and as an L level if it is higher than the predetermined value. In this way, the light emitting power approaches a predetermined value, and when the monitor signal changes from L level to H level (Fig. 4, d□), a termination signal (Fig. 4, g) is generated, and an enable signal is generated. The enable signal of the generator 26 (Fig. 4g) is changed from H level to L level.
level (Fig. 4 gz), and the power set operation is completed.

Note that FIG. 5 shows another example of the laser power adjustment section 21, and the input polarity of the operational amplifier 21C in FIG.

Inverter 21 with separate monitor signal (Fig. 4g)
E is used to invert the input polarity so that when the counter 21A counts up, the light emitting power of the laser diode 20 increases, and when the counter 21A counts down, the light emitting power decreases.

Next, the gate signal generating section 22 receives the synchronization detection signal (FIG. 4g) from the synchronization detection section 18 shown in FIGS. 1 and 2, and its □ internal counter (not shown) starts operating. A gate signal (FIG. 4b) indicating the timing at which the laser scanning light is on the photoreceptor 23 is output. That is, in the present invention, the primary gate signal rises after inputting the power set start signal (Fig. 4g).

(H level), the power set operation is started (enable signal gttH level... point g1), and the power set is completed (point b) before the gate signal falls (point b).
Even if the enable signal g reaches the L level at point g2, the laser diode signal f remains at the H level until the falling point of the gate signal b8 (becomes the L level) to turn on the laser diode 20 for power set. (ON state). Therefore, the laser diode signal f is turned ON10 F F in accordance with the photoreceptor scanning area (the H level period of the gate signal) in the -scanning line (a, -a, period) of the synchronization detection signal (Fig. 4a), In a high-speed, high-density laser printer, the laser diode can be made to emit light in an optimal state.

FIG. 6 shows another embodiment of the invention, - scanning line A1
shows an example of control when the above-mentioned power set is not completed; in this case, the next scan A,
At the rising point b3 of the gate signal B2, the enable signal g is set to H level (point ga), so that the power setting is continued from the power value of the previous line A1. The power set end processing timing is line A.

This is done in the same manner as in FIG.

(Effects of the Invention) As described above, the present invention performs 0N10FF control of the laser diode signal using a gate signal so that the photoreceptor area is uniformly exposed during power setting, so that deterioration of the photoreceptor is reduced as compared to conventional methods. There is no unevenness in the images, which prevents abnormal images from being printed.

Moreover, the power adjustment was completed in the middle of the photoreceptor area of the - scanning line. Regardless of whether or not the photoconductor area is used, exposure for power adjustment can be performed in the photoreceptor area.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a printer control unit according to an embodiment of the present invention, FIG. 2 is a schematic diagram of the configuration of the laser optical system shown in FIG. Control circuit, FIG. 4 is an operation timing chart of photoelectric control of the present invention. 5 is a circuit diagram of another embodiment of the laser power adjustment section shown in FIG. 3, FIG. 6 is an operation timing chart when power is set across two scanning lines by the method of the present invention, and FIG.
The figure is a sectional view showing a schematic configuration of a laser printer in which the present invention is implemented, and FIG. 8 is an operation timing chart of a conventional power set. 6... Laser optical system, 10... Printer main body. 14... Controller, 15... Printer control unit. 15A...CPU, 16...Host computer, 17...Deflector, 18...Synchronization detection section, 1
9...Part of power monitor, 19A...Bin photodiode, 19B...Operation amplifier, 19G...
・Volume A, 19D... Comparator, 20
...Laser diode, 21...Power adjustment unit, 21A...UP/DOWN counter, 21B...
・D/A converter, 21C... operational amplifier, 21
D...transistor, 21E...inverter. 22... Gate signal generation section, 23... Photoreceptor, 2
4...NOR gate, 25... Termination signal generation section,
26... Enable signal generation section. Patent applicant Ricoh Co., Ltd. - Figure 2
Figure 7 +b 1...Kyubukai 1 2 Ore chest 3/Registration roller pair 4-[-Fan 4ki5...Electrification charge-
Cram 6, Rhea = Kusu Tsume 7... Tsukimi 4 Koshiki ρ1
8... Transcription h-ji arm 9... Moxibustion ka reward direct
10 Desonta Book Festival 11...n) #,
e 12 Cleaning field 13...t→”-W) Housing link 14
° Controller 15...Printer 0.00 ℃ 0) Procedural amendment (February 19, 1985 Kunio Ogawa, Commissioner of the Patent Office 1, Indication of case Patent application 1988- 336548 No. 2, Title of the invention Light amount control method 3, Relationship to the case of the person making the amendment Patent applicant address 1-3-6 Nakamagome, Ota-ku, Tokyo Name (674) Ricoh Co., Ltd. Representative
Hama 1) Hiro 4, Agent 5, Subject of amendment Drawing 6, Contents of amendment The drawing No. 5 will be corrected as shown in the attached corrected drawing.

Claims (2)

[Claims] (1) A laser printer having a laser power set mechanism is characterized in that after inputting a power set start signal, the power set operation is started in synchronization with a gate signal from a gate signal generation section that operates with a synchronization detection signal. Light amount control method. (2) Even if the power set operation ends during the period in which the gate signal is active, the laser diode signal for power set is output until the gate signal becomes inactive. The light amount control method described in scope (1).