KR0119696Y1 - Optical power automatic control system of laser - Google Patents

Abstract

The present invention is a laser generating means for emitting light 14; Light receiving means (15, 16) for receiving the output light of the laser generating means (14); Charging / discharging means (C) for charging and discharging according to the output (Vf) of the light receiving means (15, 16); Control signal generating means (11) for generating a predetermined reset signal and a voltage holding signal (APC gate signal) in accordance with the input video data; Reset means (100) for initializing the charge / discharge means (C) when the reset signal is generated; Voltage holding means (28, 23) for outputting a value proportional to the value charged in the charging / discharging means (C), and maintaining the output when the voltage holding signal is generated; And laser driving means 13 for controlling the output of the laser generating means 14 in accordance with the output of the voltage holding means 28, 23, thereby simplifying the circuit to reduce the manufacturing cost, The present invention relates to an automatic light output control device of a laser having an effect of blocking line noise that can be troubled through a cable by correcting by utilizing extra time during laser scanning.

Description

Laser light output automatic control device

1 is a block diagram of an apparatus for automatically controlling light output of a conventional laser.

Figure 2 is a block diagram of the automatic light output control device of the laser according to the present invention.

Figure 3 is a detailed block diagram of the laser drive board of Figure 2 according to an embodiment of the present invention.

4 is the main signal waveform diagram in FIG.

5 is a detailed block diagram of the laser driving board of FIG. 2 according to another embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

11: control signal generator 12: automatic output controller

13: Laser drive part 14: Laser diode

15: Photodiode 16: Comparator

100: reset part 200: voltage holding part

300: current addition unit

The present invention relates to a laser light output automatic control device.

In general, when a semiconductor laser is used as a light source of an image recording apparatus, the light output is sensitive to changes in ambient temperature due to the characteristics of the semiconductor laser. Therefore, in order to obtain a good image, it is necessary to control the light output to be recognized. Mainly use light output automatic control device.

A conventional laser light output automatic control apparatus is shown in FIG. 1, in which 1 is an automatic power controller (hereinafter referred to as APC), 2 is a laser driver, and 3 is a laser diode (LD). 4 denotes a photodiode, and 5 denotes a comparator.

As shown in the drawings, conventionally, the APC 1 is located on the main board, the laser driver 2, the LD 3, and the light receivers 4, 5 are located on the laser drive board, and information exchange between them is long. The cable is used.

As an example of the conventional laser light output automatic control device looks at the up / down counter method and the method using analog and digital converters.

First, the up / down counter method controls the laser output to approach the target value step by step by increasing the up-down counter when the light output is lower than the target value and decreasing it when it is above the target value.

However, in this case, since the target value is approached in incremental or decremented manner, a considerable time is required until the end of the control, and during this time, the toner is unnecessarily attached to the photosensitive member, thereby increasing the toner consumption amount.

In the method using analog and digital converters, the A / D (Analog to Digital) converted optical output value is read by the central processing unit of the motherboard and then the current value required by the program is read. Calculate and control the light output by setting the D / A (Digital to Analog) converter to that value. In this case, the time is shorter than the above-described method, but there are additional problems such as A / D and D / A converters are additionally required and described below together with the up / down counter method.

First, analog-to-digital and digital-to-analog conversions complicate circuits and increase manufacturing costs.

Second, although the two methods differ in degree, processing takes a lot of time, so it is difficult to calibrate every line and to compensate every page or more.

Third, since the light output signal by the light detection sensor is transmitted to the APC through a long cable in the layout of the system, there is a fear that the light output value is incorrectly detected by noise or the like.

Therefore, the present invention devised to solve the above problems by using the feedback / hold circuit to stabilize the light output by simplifying the circuit to reduce the manufacturing cost, by using the extra time during laser scanning every line It is also an object of the present invention to provide a laser light output automatic control device capable of correcting and blocking noise that may be a problem through a cable by inserting an APC into a laser drive board.

The present invention to achieve the above object, the laser generating means for emitting light; Light receiving means for receiving output light of the laser generating means; Charging / discharging means for charging and discharging according to the output of the light receiving means; Control signal generating means for generating a predetermined reset signal and a voltage holding signal in accordance with the input video data; Reset means for initializing the charge / discharge means when the reset signal is generated; Voltage holding means for outputting a value proportional to the value charged in the charging / discharging means, and maintaining the output when the voltage holding signal is generated; And laser driving means for controlling the output of the laser generating means in accordance with the output of the voltage holding means.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings 2 to 5 as follows.

An apparatus for recording an image by using a scanning method using LD includes an image region in which image data is recorded on a photosensitive member with respect to the entire scanning region, and a non-image region which is not recorded but is used for synchronization detection of each line.

In general, in a system having such a structure, the main board generates a gate signal, a video signal, or a similar signal to control the LD.

The present invention is an apparatus in which APC is implemented in a region in which a gate signal is low, that is, a non-image region, in a system similar to the above.

First, FIG. 2 is a block diagram of an automatic optical output control apparatus of a laser according to the present invention, in which FIG. 11 is a control signal generator, 12 is an APC, 13 is a laser driver, 14 is LD, 15 is a photodiode, and 16 is Each comparator is shown.

Here, the APC 12 that controls the laser driver 13 in accordance with the control signal generated from the control signal generator 11 in the main board and the output of the light receivers 15 and 16 is located on the laser drive board, thereby making noise. Minimize the impact of

In addition, the control signal generator 11 is configured to generate a reset signal when a non-picture region of the input video data is applied, and generate an APC gate signal before a predetermined time before the picture region of the input video data is applied.

3 is a detailed block diagram of the laser driving board of FIG. 2 according to an embodiment of the present invention, in which 21, 26 to 28 are analog switches, 22 are zener diodes, 23 are buffers, 24 are adders, and 25 are comparators. Respectively.

As shown in the drawing, the laser driving board according to an embodiment of the present invention includes a light receiving unit 15 that detects the light emitted from the laser driving unit 13 and the LD 16 and makes its intensity constant voltage V _f . 16), V _f is greater or less than the reference voltage by the comparator 25, the resistors R2 and R3 and the analog switches 26 and 27, which compare the V _f and the reference voltage V _ref to produce a high and low signal. In order to maintain the voltage determined by the current deceleration unit 300, the comparator 25 and the current deceleration unit 300 for adding or subtracting a current, a voltage holding unit having a buffer 23 composed of a capacitor C and an op amp ( 200), the voltage V _fM output from the voltage holding part 200 and the base voltage V _B are added to add an adder 24 for supplying the output voltage V ₀ to the laser driver 13, and an initial voltage of the capacitor C. In order to set, a reset section consisting of a resistor R1, a zener diode 22, and an analog switch 21 ( 100) and an analog switch 28 for connecting the circuit at the start of the APC and isolating it after a certain time.

Looking at the detailed operation of the present invention having the configuration as shown in FIG. 3 as follows.

The reset signal is sent to the laser drive board at the start of the non-picture area on the main board. The capacitor C is discharged to the limit of the zener diode 22 when the reset signal is low. At this time, the resistor R1 is considerably smaller than the resistors R2 and R3, and it is necessary to use a smaller value for quick discharge. The reason the design using the Zener diode 22 so as to have a fixed voltage even when the discharge is in a short period of time after stop the zoom at the same time reset to the voltage during charging and discharging changing rapidly by the resistor (R2, R3) V _f is V _ref To get to.

Once discharged, the voltage V _{h at} that time becomes V _z , and this voltage is supplied to the adder together with the base voltage V _{B in} the form of V _fM via the amplifier 23. At this time, it is preferable to set V _B near the minimum voltage at which the LD light output comes out. The reason for driving V ₀ by the sum of V _B and V _fM is to adjust the light output more precisely. The LD 14 makes light output by V ₀ immediately after the reset, and V _f is formed through the photo diode 15 and the comparator 16.

Since V _f will be V _f V _ref , the analog switch 26 is closed and the analog switch 27 is open under the condition that current can flow into the capacitor C (assuming all analog switches are connected low). do).

When the APC gate signal generated from the motherboard goes low after reset, the analog switch 28 is connected and current flows through the resistor R2, and this current is charged to the capacitor C to increase V _h → increase V ₀ → This leads to an increase in V _f , which continues with V _f V _ref .

When V _f ≥ V _ref , the switch 26 is opened, and the switch 27 is closed to discharge.

This process is repeated until the APC gate signal goes high.

When the APC gate becomes high, the switch 28 is disconnected and the capacitor C maintains the potential at that time. Since the input impedance of the operational amplifier 23 is very large, if the value of the capacitor C is increased to some extent, the potential drop due to natural discharge can be ignored.

When the next non-picture area (the area where the gate signal goes low again) comes, the previous process is repeated.

For reference, the main signal waveform diagram of the present invention operated as described above is shown in FIG. 4, and it can be easily seen from the drawing that the output of the LD is quickly stabilized in the non-picture region.

FIG. 5 is a detailed block diagram of the laser driving board of FIG. 2 according to another embodiment of the present invention, in which 31 is a differential amplifier and 32 is an adder.

As shown in the figure, another embodiment of the present invention, instead of using the comparator in the above embodiment, after amplifying the _difference between V _ref and V _f by a constant ratio A through a differential amplifier 31 to make V _d Is a modified circuit in which the sum of another base voltage V _B1 is supplied to the capacitor C so that the potential of the capacitor C is held by V _d . At this time, the value of V _B1 is that it is effective to set such that V _Z V _B1 + V _d. In addition, a modified circuit using feedback and hold concept is possible.

The present invention made as described above reduces the manufacturing cost by simplifying the circuit, and makes it possible to calibrate every line by utilizing an extra time during laser scanning, and also to block noise that may be a problem through the cable. There is.

Claims (10)

Laser generating means (14) for emitting light; Light receiving means (15, 16) for receiving the output light of the laser generating means (14); Charging / discharging means (C) for charging and discharging according to the output (V _f ) of the light receiving means (15, 16); Control signal generating means (11) for generating a predetermined reset signal and a voltage holding signal (APC gate signal) in accordance with the input video data; Reset means (100) for initializing the charge / discharge means (C) when the reset signal is generated; Voltage holding means (28, 23) for outputting a value proportional to the value charged in the charging / discharging means (C), and maintaining the output when the voltage holding signal is generated; And laser driving means (13) for controlling the output of the laser generating means (14) in accordance with the output of the voltage holding means (28, 23). 2. The apparatus according to claim 1, wherein the control signal generating means (11) is configured to generate a reset signal when a non-picture area of the input video data is applied. 2. The apparatus according to claim 1, wherein the control signal generating means (11) is configured to generate a voltage holding signal before a predetermined time is applied to the image region in the input video data. 2. The apparatus of claim 1, wherein the reset means (100) comprises: a switch (21) turned on and off in accordance with the reset signal; And a zener diode (22) for charging the charge / discharge means (C) at a constant voltage in accordance with the on / off state of the switch (21). The method of claim 1, wherein the voltage holding means (28, 23), according to the voltage holding signal transfers a predetermined signal according to the output of the light receiving means (15, 16) to the charging and discharging means (C). And a switch 28 to cut off; And a buffer (23) receiving the output of the charging and discharging means (C). 2. The apparatus of claim 1, further comprising: comparing means (25) for comparing the output of the light receiving means (15, 16) with a predetermined first reference voltage (V _ref ); And supplying a current to the charging and discharging means (C), the automatic light output of the laser, characterized in that it further comprises a current addition means 300 for adding or subtracting the current supplied according to the output of the comparison means (25) Control unit. 2. The apparatus of claim 1, further comprising: differential amplifying means (31) for differentially amplifying an output of said optical receiving means (15, 16) and a predetermined second reference voltage (V _ref ); And a first adding means 32 for adding the output of the automatic amplifying means 31 and the predetermined third reference voltage V _B1 to provide the result to the charging / discharging means C. Automatic light output control device of the laser. 8. The laser light output of claim 7, wherein the third reference voltage is set larger than a difference between an initial value of the charging and discharging means (C) and an output of the differential amplifying means (31). Control unit. 2. The second adding means according to claim 1, further configured to add the outputs of the voltage holding means (28, 23) and the predetermined fourth reference voltage (V _B ) to control the laser driving means (13) according to the result. An optical output automatic control device for a laser, characterized by further comprising (24). 10. The apparatus of claim 9, wherein the fourth reference voltage is set to be larger or smaller than a minimum voltage at which the laser generating means outputs light.