JPS62237473A - Laser beam quantity controller - Google Patents

Abstract

PURPOSE:To always obtain the image of a prescribed density, and also, to intentionally make an image density variable, by constituting the titled device so that a reference value can be freely set without executing the adjustment of a voltage dividing resistance. CONSTITUTION:A ROM 14c stores a reference data corresponding to a light quantity level, and a microcomputer 14 selects an optional reference value data. A D/A converter 15 receives digital signals outputted from ports 01-09 of the microcomputer 14, by ports A1-A9 and converts them to analog signals, and outputs them to a current-voltage converting circuit 16. As for a changeover switch 39 being a selecting means, when this changeover switch 39 is on, an automatic mode for determining automatically a light quantity set value is set, and when said switch is off, a manual mode for making the light quantity set value manually is set. A variable resistor 40 being a voltage generating means inputs an analog input AN2 which becomes a manual reference value, to the internal memory of the microcomputer, when the changeover switch 39 is off.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a laser light amount control device that controls the amount of laser light of an image forming apparatus that irradiates a recording medium such as a photoreceptor with a laser beam to form a latent image. It is something.

[Conventional technology]

Conventionally, this type of device was developed by Japanese Patent Application Publication No. 5E! -10825
Publication No. 9 etc. have been proposed.

In devices that scan a photosensitive drum with a laser beam to form a latent image, when replacing the photosensitive drum, the amount of laser light is changed according to variations in drum sensitivity, and adjustments are made so that an image with a constant density is always obtained. There is a need.

For this reason, in the past, multiple comparators were installed to compare the output from detecting the laser light intensity with a reference voltage, the sensitivity signal taken out from the drum unit was decoded, and the laser light intensity was adjusted to the specified value using the comparator output corresponding to the sensitivity. The amount of laser light was controlled by determining whether the

[Problem that the invention seeks to solve]

However, when multiple reference voltages are provided, the reference voltage tends to change due to variations in the voltage dividing resistor used to generate the reference voltage or changes in the input current of the comparator, which poses the problem of causing errors in the amount of laser light. . Further, since the reference voltage is determined by the value of the voltage dividing resistor, there is a problem in that the reference value cannot be freely selected. Furthermore, there are many other problems, such as the fact that it takes time and effort to adjust the voltage dividing resistors.

This invention was made to solve the above problems, and it is possible to freely set a reference value without adjusting the voltage dividing resistor, and also to automatically correct sensitivity variations when replacing a drum, for example. The object of the present invention is to provide a laser light amount control device that can manually and variably set automatically set image density.

[Means for solving problems]

A laser light amount control device according to the present invention includes an A/D conversion means that converts an analog signal output from a light amount detection means into a digital signal, and reference value data that stores in advance reference value data corresponding to a light amount level of a laser beam. A storage means, a voltage generation means for generating a reference value voltage for setting an arbitrary image density, and a reference value data creation means for creating reference value data by A/D converting the analog voltage of the voltage generation means. , selection means for selecting either the reference value data stored in the reference value data storage means or the reference value data created by the reference value data creation means; and the reference value data selected by the selection means and A. a comparison means for comparing the output of the /D conversion means; a D/A conversion means for converting the output of the comparison means into an analog signal;
A current control means for controlling the current applied to the laser according to the output of the /A conversion means is provided.

[Effect]

In this invention, when the light amount detection means detects laser emission, the A/D conversion means converts the output of the light amount detection means into a digital signal. here.

When the pre-stored reference value data for tearing is selected according to the light intensity level input by the selection means, the comparison means compares the pre-stored reference value data and the output of the A/D conversion means. When the selection means selects the value obtained by A/D converting the reference value voltage generated by the voltage generation means, the comparison means compares the arbitrarily set reference value data and the output of the A/D conversion grid. , the current control means controls the current applied to the laser based on the output of the comparison means.

〔Example〕

FIG. 1 is a block diagram illustrating the configuration of a laser light amount control device showing an embodiment of the present invention, in which 1 is a semiconductor laser and 2 is a diode to protect the semiconductor laser 1. In FIG. A resistor 3 prevents overshoot of the current flowing through the semiconductor laser 1. 4.5 is a capacitor, 6.7 is a resistor, and when the wiring cable between the semiconductor laser 1 and the drive circuit is long, each of 4 to 7 is provided at both ends to correct one frequency characteristic.

A photodiode 8 detects the amount of laser light. A variable resistor 9 corrects variations in sensitivity of the photodiode 8. 10 is a load resistor, which is connected to the variable resistor 9. 11 and 12 are resistors that determine the gain of the operational amplifier 13. 14 is a one-chip microcomputer (
(hereinafter referred to as a microcontroller), an analog multiplexer (M
P
It has c. The ROM 14c stores reference data (digital values) corresponding to the light intensity level, which will be described later, and the microcomputer 14 selects arbitrary reference value data according to the input light intensity level. Reference numeral 15 denotes a D/Al converter, which receives digital signals output from the ports 01 to 09 of the microcomputer 14 at the ports Al to A9, converts them into analog signals, and outputs the analog signals to the current-voltage conversion circuit 16 from the port 10UI.

The current-voltage conversion circuit 16 includes an operational amplifier 17 and the like. The D/A converter (D/A) 15 has a resistor 18.
19 determines the reference potential.

Mata v(,R), ■(-R) indicate the reference current value of the D/A converter 15, 20 is a constant current circuit, operational amplifier 21,
Transistor 22. The capacitor 23 prevents overshoot occurring during output conversion of the D/A converter 15.

24 is a resistor, 25 is a coil, coil 25 and resistor 24
This improves frequency characteristics. Reference numeral 26 denotes a current switch, which is composed of transistors 27, 28, resistors 29 to 32, and the like. 33 is an OR gate which performs an OR operation between the signal output from the port 010 of the microcomputer 14 and the image signal VDO (sent from the host side, not shown). 3
4 is a NAND gate which takes the NAND of the output of the OR gate 33 and the scan ready signal 5CNRDY. The output of the Nandt gate 34 is output to the base of the transistor 27 of the current switch 26. 35 is a terminal, which receives the light amount control start signal A.
PC3T is applied and input to the input port 4 of the microcomputer 14. 36 to 38 are terminals r, and light intensity switching signals 5l-
S3 is applied, and the input ports Il to I of the microcomputer 14,
3 is input. Reference numeral 39 denotes a changeover switch serving as the selection means of the present invention. When the changeover switch 39 is on, an automatic mode is set to automatically determine the light intensity setting value, and when it is off, a manual mode is set to manually vary the light intensity setting value. mode is set. 40 is a variable resistor which constitutes the voltage generating means of the present invention, and when the changeover switch 39 is off,
The analog human power AN2 serving as a manual reference value is input into the internal memory of the microcomputer 14. Note that the output of the operational amplifier 13 becomes an analog input ANI of the microcomputer 14.

The scan ready signal 5CNRDY is a signal indicating that a motor for driving a rotating polygon mirror for laser beam deflection (not shown) is rotating at a specified speed. moreover,
The light quantity control start signal APC3T is a signal outputted from a printer control means (not shown) prior to the start of image recording. Note that the microcomputer 14 also serves as a comparison means of the present invention.

Next, the laser light amount control operation according to the present invention will be explained with reference to FIG.

FIG. 2 is a flowchart illustrating an example of the laser light amount control operation according to the present invention. In addition, (1) to (17)
indicates each step.

First, the light amount control start signal APC3T is applied to the terminal 35, and it is determined whether it is input to the input port I4 of the microcomputer 14 (1). If No, proceed to step (11) or later; if YES, the light amount control start signal APC3T is input to the input port E4. 2). If NO, proceed to step (11) and subsequent steps; if YES, start the internal timer of the microcomputer 14, and (3) 14 ports 01-09
(4) As a result, the port Iout of the D/A converter 15 becomes rQJ, and the current flowing through the transistor 22 of the constant current circuit 20 also becomes "0". Therefore, even if the transistor 28 of the current switch 26 is turned on, no current is applied to the semiconductor laser 1. Next, the microcomputer 14
Set port 010 of to HIG)i (content rl)
(5) Next, determine whether the 4A conversion switch 39 is on, that is, whether automatic mode is requested, from the contents of input port I5 of the microcomputer 14 (6), and if NO, analog manual operation is required. The AN2e A/D converter 14b performs A/D conversion (7) and stores the A/D converted value (reference value data) in the internal memory of the microcomputer 14 (
1G), when converting the analog input AN2 to A/D, take into account conversion errors and noise superimposed on the analog signal, read the data multiple times, and calculate the average value as the true value. It is being processed into data.

On the other hand, if the judgment in step (8) is YES, the ROM
The mode is set to control the light amount based on the data stored in 14c, and the light amount switching signal 3 is input to terminals 36 to 38.
Enter 1-33 and take the Uke from II to 3. Then,
The light intensity switching signals 51 to S3 are decoded (8) and the reference value data corresponding to the specified light intensity level is stored in the ROM 14.
(9) and stores the selected reference data in the internal memory (10).

On the other hand, if the determination in step (2) is NO, it is determined whether a timer (not shown) of the microcomputer 14 is operating (11), and if No, the port o i o of the microcomputer 14 is determined.
Set t-Low (12) and end the control. This turns off the transistor 28 of the current switch 26 and cuts the current of the semiconductor laser 1.

On the other hand, if the determination in step (11) is YES, it is determined whether the reference value data (Ml data) stored in the internal memory is larger than the A/D conversion value obtained by A/D converting the analog input ANI. 13), if No, proceed to step (IB) and after; if YES, add rlJ to the values output from ports 01 to 09 (14). As a result, the current of the semiconductor laser 1 is changed to the D/A converter 15. is increased by 1 bit (15). Next, when the ports 01 to 09 of the microcomputer 14 are changed, the laser current increases, and a predetermined delay correction time (1+) until the laser current is transmitted to the analog input ANI of the microcomputer 14, that is, step (1
It is determined whether or not the timer started in step 1) has timed up (16). If NO, the control is terminated; if YES, the timer is stopped (17) and the control is terminated.

In the above embodiment, a case has been described in which the time for adjusting the light amount is controlled by a timer, but instead of the timer, an area may be provided in the RAM of the microcomputer 14 to store whether or not the light amount adjustment operation is in progress. Further, by providing a plurality of variable resistors 40, the adjustment ratio may be finely adjusted.Furthermore, the variable resistor 4o is not limited to being variable, and may be a fixed resistor.

Next, the laser light amount readjustment operation according to the present invention will be explained with reference to FIG.

FIG. 3 is a flowchart for explaining the laser light amount readjustment operation according to the present invention. In addition.

(21) to (23) indicate each step, and if the operation is the same as the flow in FIG. 2, the same step number will be added and redundant explanation will be omitted.

When replacing the photosensitive drum, it is necessary to readjust the amount of laser light that was manually set before the replacement. There□, 3 steps (
If the answer is No in step 6), proceed to step (8).
), perform (9) 0, then press switch 3 again
The input port I5 of the microcomputer 14 determines whether or not 9 is on, that is, whether automatic mode is requested.
Judging from the contents of (21), if YES, return to step (10); if No, normalize the value converted in step (7) by setting the median value of variable resistor 4o to "1" (22 ), then the normalized value is multiplied by the reference data selected in step (θ) (23), and the multiplication result, that is, the rate (%) of changing the light amount, is stored in the internal memory of the microcomputer 14 ( 10). This results in
It becomes possible to change the amount of laser light at a rate that is manually set when replacing the photosensitive drum.

〔Effect of the invention〕

As explained above, the present invention is an A/D converter that converts an analog signal output from a light amount detection means into a digital signal.
a conversion means, a reference value data storage means for storing in advance reference value data corresponding to a laser light intensity level, a voltage generation means for generating a reference value voltage for setting an arbitrary image density, and a voltage generation means for generating a reference value voltage for setting an arbitrary image density; Analog voltage A/
Selection of selecting one of the reference value data creation means that performs D conversion to create reference value data, and the reference value data stored in the reference value data storage means or the reference value data created by the reference value data creation means. a comparison means for comparing the reference value data selected by the selection means with the output of the A/D conversion means; a D/A conversion means for converting the output of the comparison means into an analog signal; Since a current control stage is provided to control the current applied to the laser according to the output of the A conversion means, there is no need to adjust the variation in the voltage dividing resistor, and it is not affected by the value of the voltage dividing resistor. Reference values can be set freely. Furthermore, since it automatically corrects sensitivity variations in the photosensitive drum when replacing the photosensitive drum, it is not only possible to always obtain an image with a constant density, but also to automatically correct the sensitivity variation of the photosensitive drum when replacing the photosensitive drum. Since the amount of light can be varied, excellent effects such as being able to intentionally vary the image density can be achieved.

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating the configuration of a laser light amount control device showing an embodiment of the present invention, and FIG. 2 is a flowchart explaining an example of a laser light amount control operation according to the present invention.
FIG. 3 is a flowchart for explaining the laser light amount readjustment operation according to the present invention. In the figure, 1 is a semiconductor laser, 2 is a photodiode, 14
is a microcontroller, 14a is an analog multiplexer, 14b
is A/D converter, 14c is ROM, 15 is D
/A converter, 20 is a constant current circuit, 26 is a current switch,
39 is a changeover switch, and 40 is a variable resistor. Figure 2 Figure 3

Claims (1)

[Claims] A laser light amount control device that controls the amount of laser light emitted according to a light amount signal output from a light amount detection means that detects the amount of laser light, and an A/D converter that converts an analog signal output from the light amount detection means into a digital signal. D conversion means, reference value data storage means for storing in advance reference value data corresponding to the light intensity level of the laser, voltage generation means for generating a reference value voltage for setting an arbitrary image density, and this voltage generation means. Reference value data creation means for creating reference value data by A/D converting the analog voltage of the means;
selection means for selecting either the reference value data stored in the reference value data storage means or the reference value data created by the reference value data creation means; the reference value data selected by the selection means and the reference value data; a comparison means for comparing the output of the A/D conversion means; a D/A conversion means for converting the output of the comparison means into an analog signal; and a current applied to the laser according to the output of the D/A conversion means. 1. A laser light amount control device comprising: current control means for controlling.