JPH04291377A - Laser output controller - Google Patents

Abstract

PURPOSE:To prevent an increase in circuit scale and easily vary a set value of laser power. CONSTITUTION:A storage part (ROM) 11 is stored with set values corresponding to resolution and set values for fine adjustments of respective resolution values. Resolution specification data RS and adjustment quantity specification data AJ outputted by a resolution specification data generation part 12 and an adjustment quantity specification data generation part 13 are paired into address data of the storage part 11 and a set value is read out of the storage part and inputted to a DA converter 14. A comparison part 16 inputs a signal corresponding to the difference between laser power detected by a laser output detection part 20 and set power outputted by the DA converter 14 to a laser diode driving circuit 18, which drives a laser diode 19 according to the input signal to adjusts the laser power to the set value.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser output control device, and more particularly to a laser output control device suitable for controlling the resolution of a laser printer.

0002

2. Description of the Related Art In a laser printer, a photosensitive drum is rotated and a laser is repeatedly moved at a predetermined speed in the longitudinal direction (main scanning direction) of the photosensitive drum. During this movement, dot image data is Turns on the laser emission based on the
This forms an electrostatic latent image on the surface of the photosensitive drum, after which a toner image is formed (developed) and transferred to print characters and images as dot images on printing paper.

Such laser printers have a plurality of types of resolution, and the resolution can be changed by switching the laser power. Laser power control is based on the laser power output from the laser diode.
The feedback control is performed by comparing the set value and driving the laser based on the difference, and by changing the set value, the laser power can be changed.

[0004] Conventionally, therefore, in order to change the resolution, a plurality of switches (analog switches) are provided, and a reference signal having a set value corresponding to the desired resolution is generated by switching the resistor using a predetermined switch. It has become.

In laser printers, variations in sensitivity of the photosensitive drum (photosensitive member), toner concentration, potential on the surface of the photosensitive drum,
Due to variations in transfer current, etc., variations may occur in the thickness of printed lines (resolution). Therefore, in addition to the circuit for changing the resolution, a fine adjustment circuit is required to finely adjust the laser power to change the line thickness (resolution).

This fine adjustment circuit is realized by providing a reference signal generating section that outputs a large number of reference signals and a switch for selecting the reference signal.

[0007]

As described above, conventional resolution changing circuits and fine adjustment circuits each consist of a reference signal generating section and a large number of switches, resulting in a problem of large circuit scale. In particular, there is a problem that the larger the number of resolutions and the number of fine adjustment steps, the larger the circuit scale becomes.

Furthermore, with conventional resolution changing circuits and fine adjustment circuits, if the set value of the laser power changes due to a change in the specifications of the photoreceptor, modification is required, and there is a problem in that the modification work is extremely troublesome. .

From the above, it is an object of the present invention to provide a controller whose circuit scale is relatively small and whose setting values can be easily changed.
An object of the present invention is to provide a power output control device.

0010

[Means for Solving the Problems] FIG. 1 is a diagram illustrating the principle of the present invention. 11 is a storage unit (ROM) that stores setting values according to the resolution and setting values for fine adjustment of each resolution; 12
Reference numeral 13 indicates a resolution specification data generation unit that generates data specifying resolution; 13 indicates an adjustment amount specification data generation unit that generates data that specifies the amount of fine adjustment of resolution; and 14 converts the set value read from the storage unit 11 into digital-to-analog. 16 is the laser power and DA converter output (setting power
), 18 is a laser diode drive circuit that drives the laser diode based on the difference between the laser power and the DA converter output, 19 is a laser diode, 2
0 is a laser output detection section.

[0011]

[Operation] Setting values corresponding to resolutions and setting values for fine adjustment of each resolution are stored in advance in the storage unit (ROM) 11. Then, the resolution designation data RS and adjustment amount designation data AJ output from the resolution designation data generation section 12 and the adjustment amount designation data generation section 13 are combined into a storage section 1.
1, the set value is read from the storage section, and input to the DA converter 14. The comparator 16 inputs a signal corresponding to the difference between the laser power detected by the laser output detector 20 and the set power output from the DA converter 14 to the laser diode drive circuit 18. , the laser diode drive circuit 18 drives the laser diode based on the input signal.
19 and set the laser power to the set value.

[0012] In this way, the setting values for the resolution and the resolution after fine adjustment are stored in the storage unit (ROM) 11, and the predetermined setting values corresponding to the designated resolution and fine adjustment amount are read out and DA converted. Since the configuration is configured to generate the set power, the circuit scale does not become relatively large, and even if the number of resolutions or the number of fine adjustment steps increases, the circuit scale does not increase. Also, setting values can be easily changed by simply rewriting the memory contents or changing the ROM.

[
In addition, a plurality of setting value tables corresponding to the resolution and adjustment amount are prepared and stored in the storage unit in correspondence with the print thickness, and a print thickness specification data generation unit is provided to determine the print thickness. Print thickness can be controlled by reading setting values based on resolution specification data and adjustment amount specification data from a table indicated by the specification data and inputting them to the DA converter.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (a) Overall configuration of first embodiment of the present invention FIG. 2 is a block diagram of one embodiment of the present invention, and the same parts as in FIG. 1 are given the same reference numerals.

In the figure, reference numeral 11 denotes a storage unit (ROM
), 12 is 2-bit data RS01 that specifies the resolution
, RS02, and 13 is 4-bit data AJ01 that specifies the amount of fine adjustment of the resolution.
~AJ04 is generated by an adjustment amount designation data generation section, 14 is a DA converter that converts the setting value read from the storage section 11 into digital/analog, and 15 is an amplifier and low-pass filter section that amplifies and smoothes the DA conversion output. , 16 is the laser power and the setting power output from the DA converter 14.
A comparator 17 outputs a signal RPS corresponding to the difference between the comparator 16 and a sampling hole.
A sampling and hold circuit 18 is used to hold the laser signal based on the difference between the laser power and the DA converter output (set power).
Laser diode drive circuit that drives the laser diode, 1
9 is a laser diode, 20 is a laser output detector, 21
is a switch section, which has a switch SW6 that turns on and off based on the laser emission signal RES.

Resolution specification data generation unit and adjustment amount specification data generation unit The resolution specification data generation unit 12 is composed of, for example, two switches (not shown), and selects four resolutions by turning the switches on and off. It is now possible to do so. The adjustment amount designation data generating section 13 is composed of four switches SW1 to SW4, four resistors R1 to R4, and four not gates NT1 to NT4. ,
Each resolution can be fine-tuned in 16 steps.

Memory section (ROM) The memory section 11 having a ROM configuration has a 6-bit address terminal A0.
~A5 and 8-bit data output terminals D0 to D7,
4-bit adjustment amount designation data AJ01 to AJ04 (switch SW1
~ Corresponds to SW4 on/off) below 4 of address data
The upper 2 bits of the address data are expressed by 2-bit resolution designation data RS01 to RS02 output from the resolution designation data generation section 12.

The storage unit 11 stores a total of 64 (=16×4) setting values when each of the four resolutions is adjusted in 16 steps (including zero adjustment amount). Figure 3
is a relationship diagram between 16 setting values (ROM data) and on/off states of switches SW1 to SW4 when one resolution is finely adjusted in 16 steps. If the setting value according to the resolution is x, then when switches SW1 to SW4 are all off (adjustment amount is zero), the ROM data is x, when only switch SW1 is on, x+a, and when only switch SW2 is on, the ROM data is x. In this case, x+2a, and so on, switch SW1~
When all SW4 are on, the value is x+15a, and the fine adjustment increments are a.

Therefore, the 16 set values x1 to x1+15a corresponding to the first resolution are stored at address 000 of the storage unit 11.
000 to 001111, 16 setting values x2 to x2+15a corresponding to the second resolution are stored in addresses 010000 to 011111 of the storage unit 11, and 16 setting values x3 to x3+15a corresponding to the third resolution. is stored at addresses 100000 to 101111 of the storage unit 11, and 16 setting values x4 to x4 according to the fourth resolution
+15a is address 110000-111 of storage unit 11
111.

Comparison section The comparison section 16 is composed of an amplifier A1 that amplifies the laser output signal, resistors R5 to R7, and a differential amplifier D1, and is
A difference signal RPS proportional to the difference between the current power and the set power is output.

Sampling and Holding Circuit The sampling and holding circuit 17 includes a resistor R8 and a laser emission signal RES.
It is composed of a switch SW5 that is turned on and off based on , a capacitor C1, and an amplifier A2.

[0022] In a laser printer, a laser is moved at a predetermined speed in the longitudinal direction (main scanning direction) of a photosensitive drum, and during the movement, the laser emission is turned on and off based on dot image data. , thereby forming an electrostatic latent image of a dot image on the surface of the photosensitive drum. For this reason, in a laser printer, the laser does not emit light all the time, and there are times when it does not emit light. When the light emission stops, the laser output becomes zero,
The difference signal RPS becomes large and malfunctions. For this reason,
When laser light is emitted (laser light emitting signal RES="1"), switch SW5 is turned on and the value of difference signal RPS is set to capacitor C1.
When the laser emission stops (laser
The light emission signal RES="0") turns off the switch SW5, and outputs a hold signal while the switch is off.

Laser diode drive circuit Laser diode
The head drive circuit 18 drives the laser diode 19 based on the difference signal RPS' between the laser power and the set power output from the sampling and hold circuit 17, and is connected to the resistors R9 to R12 and the difference signal RPS'. It is composed of a transistor TR that controls the value of current flowing through the laser diode 19 by changing its conductivity based on the signal RPS'.

Laser power detection section The laser power detection section 20 is composed of a photodiode that detects the brightness of the laser output from the laser diode 19, that is, the laser power. A voltage signal Vm corresponding to the laser power is input to the amplifier A1 of the comparator 16.

Switch section The switch SW6 of the switch section 21 is turned off when the laser is emitted (laser emission signal RES="1"), and is turned off when the laser emission is stopped (laser emission signal RES="0"). ”). When the switch SW6 is turned on, the base voltage of the transistor TR becomes 0 volts, the transistor is cut off, and the laser diode 19 stops emitting light.

Overall operation Setting values corresponding to resolutions and setting values for fine adjustment of each resolution (see FIG. 3) are stored in the storage section (ROM) 11 in advance.

Then, two switches (not shown) of the resolution designation data generating section 12 are turned on and off, and a predetermined resolution is selected from among the four resolution levels based on the combination thereof. As a result, 2-bit resolution designation data RS01 to RS02 corresponding to the selected resolution is output. Further, the switches SW1 to SW4 of the adjustment amount designation data generating section 13 are turned on and off, and a predetermined adjustment amount is selected from among the 16 levels of adjustment amounts based on the combination thereof. As a result, 4-bit adjustment amount designation data AJ01~
AJ04 is output.

6-bit address data is formed by the resolution designation data RS01 to RS02 and the adjustment amount designation data AJ01 to AJ04, and as a result, the storage unit (ROM) 1
1, a setting value corresponding to the selected resolution and the selected adjustment amount is read out and input to the DA converter 14.

The DA converter 14 converts the input setting value into a DA converter.
The converted signal is input to the comparison section 16 via the amplifier and low-pass filter section 15. The comparator 16 generates a signal Vm' corresponding to the laser power detected by the laser output detector 20.
A signal (difference signal) RPS corresponding to the difference between the signal Va and the set power outputted from the DA converter 14 (difference signal) RPS is outputted to the laser diode drive circuit 18 via the sampling and hold circuit 17. input.

The laser diode drive circuit 18 controls the conductivity of the transistor TR based on the input signal RPS', and controls the value of the current flowing through the laser diode 19. After that, the laser power is detected, compared with the set power, and feedback control by driving the laser diode based on the difference continues, and the laser power is controlled to match the set power. .

In this way, setting values corresponding to the resolution and fine adjustment are stored in the storage unit (ROM) 11, and setting values corresponding to the specified resolution and fine adjustment amount are read out and DA converted. Since power is generated, the circuit scale does not increase, and even if the number of resolutions and fine adjustment steps increases, the circuit scale does not increase. Furthermore, the set values can be easily changed by simply rewriting the stored contents or changing the ROM.

(b) Second Embodiment of the Invention FIG. 4 is a block diagram of a second embodiment of the invention, in which the same parts as in the first embodiment of FIG. 2 are given the same reference numerals. The second embodiment differs from the first embodiment in the following points: i. A print thickness designation data generating section 22 is provided, and 2-bit print thickness designation data P0 is provided.
~The point of outputting P1, b. C. The storage capacity of the storage section (ROM) 11 has been increased, the address terminal has been made 8 bits A0 to A7, and three types of ROM data have been stored depending on the type of print thickness; c. 4-bit adjustment amount specification data AJ0
1 to AJ04 and 2-bit print thickness specification data P0 to
P1 and 2-bit resolution specification data RS01 to RS0
2 constitutes 8-bit address data.

Print thickness specification data generation section The print thickness specification data generation section 22 is composed of two switches (not shown), and depending on the on/off combination of the switches, three
You can select the print thickness (thick, normal, thin).

Memory section (ROM) The memory section 11 having a ROM configuration has an 8-bit address terminal A0.
~A7 and 8-bit data output terminals D0 to D7,
4-bit adjustment amount designation data AJ01 to AJ04 (switch SW1
~ Corresponding to ON/OFF of SW4), the lower 4 bits of the address data are output from the print thick data generation section 22.
The next two high-order bits of the address data in the bit print thickness designation data P0 to P1 are generated by the resolution designation data generation unit 12.
2-bit resolution specification data RS01~ output from
The most significant two bits of address data are expressed by RS02.

The storage unit 11 stores types of print thickness (line thickness,
The 64 setting values described in the first embodiment are stored, respectively, depending on the type (normal, thin line). In other words, for fine lines, when each of the four resolutions is adjusted in 16 steps (including zero adjustment amount), a total of 64 resolutions (= 16 × 4
), the total of 64 (=16 x 4) setting values when each of the four resolutions is adjusted in 16 steps (including zero adjustment amount) for ordinary lines is as follows. Furthermore, for line thickness, a total of 64 (=16×4) setting values are stored in the storage unit 11 when each of the four resolutions is adjusted in 16 steps (including zero adjustment amount). has been done.

FIG. 5 shows 48 points (
=3×16) setting value (ROM data) and switch SW
1 to SW4 are on/off relationship diagrams. FIG. If the setting value according to the resolution is x, if the print thickness is normal (adjustment amount is zero), the setting value is x, if the line is thin (adjustment amount is zero), the setting value is x - c, if the line is thick (adjustment amount zero) becomes x+b. Then, each setting value is determined and stored in the storage unit 11 so that the resolution can be finely adjusted in increments of a by a combination of on/off of the switches SW1 to SW4.

The overall operation is almost the same as that in FIG. That is, the storage unit 11 stores in advance setting values according to the resolution and setting values for fine adjustment of each resolution for each type of print thickness (thick line, normal line, thin line).

Then, a predetermined print thickness is selected by turning on and off two switches (not shown) of the print thickness designation data generation section 22, and two switches (not shown) of the resolution designation data generation section 12 are turned on and off. to select the resolution, and turn on/off switches SW1 to SW4 of the adjustment amount designation data generating section 13 to select the adjustment amount.

[0039] As a result, the resolution designation data RS01~
8-bit address data is formed by RS02, print thickness designation data P0 to P1, and adjustment amount designation data AJ01 to AJ04, and is stored in the storage unit (ROM) 11 with the selected print thickness and the selected resolution. A set value corresponding to the selected adjustment amount is read out, DA converted, and input to the comparison section 16.

[0040] From then on, the same fields as in the first embodiment will be used.
Back-back control is performed, and the power of the laser is controlled to the set power.

Another example of ROM data when controlling print thickness FIG. 6 shows setting values (ROM data) when finely adjusting one resolution in 16 steps for each of three types of print thickness. This is another example.

[0042] If the setting value corresponding to a certain resolution is x, then
When the printing thickness is normal, the setting values (x, x+a, x+2a, . . . ) are determined so that the resolution can be finely adjusted in increments of a by turning on and off the switches SW1 to SW4. In addition, in the case of a thin line, the setting value (e
x, e(x+a), e(x+2a),...), and in the case of a thick line, the setting value ( dx, d(x+a
), d(x+2a),...) and stores it in the storage unit 11.
I try to remember it.

Further examples of ROM data for controlling print thickness In FIGS. 5 and 6, one resolution can be set for each of three types of print thickness by adding/subtracting or multiplying constants. 48 (=3×16) setting values (ROM data) for fine adjustment in 16 steps are determined and stored in the storage unit 11, but each setting value is set to be optimal. You can also do that.

FIG. 7 shows an example of ROM data in such a case. If the setting value corresponding to a certain resolution is x1, when the print thickness is normal, switches SW1 to SW4 are turned on and off.
Set each setting value x1 so that the resolution can be fine-tuned by turning it off.
, x2, x3, ...
,...Determine y16, and if the line is thick, switch SW
Each setting value z1, z2, z3, . Note that each set value increases as the suffix number increases, and for the same suffix, z<x<y.

(c) Third Embodiment of the Present Invention FIG. 8 shows a third embodiment of the present invention, in which the same parts as in the second embodiment of FIG. 4 are given the same reference numerals. In a third embodiment,
The difference from the second embodiment is i. A ROM data selection signal generator 23 is provided, and a 2-bit ROM data selection signal M is provided.
Point of outputting 0 to M1, b. By increasing the storage capacity of the memory unit (ROM) 11 and increasing the address terminal to 10 bits A0 to A9, three types of ROs with the configurations shown in FIGS. 5, 6, and 7 are available.
C. M data (first to third ROM data) is stored.
2. Which of the three types of ROM data is selected by the ROM data selection signal generator 23; The 10-bit data is determined by the 4-bit adjustment amount specification data AJ01 to AJ04, the 2-bit print thickness specification data P0 to P1, the 2-bit resolution specification data RS01 to RS02, and the 2-bit ROM data selection signals M1 and M2. This is the point that constitutes address data. Furthermore, Figure 9 shows a 2-bit ROM.
The relationship between data selection signals M0 and M1 and ROM data to be used is shown.

The present invention has been explained above using examples, but
The present invention can be modified in various ways according to the gist of the present invention as described in the claims, and the present invention does not exclude these modifications.

[0047]

As described above, according to the present invention, setting values for the resolution and resolution after fine adjustment are stored in the memory, and predetermined setting values corresponding to the designated resolution and fine adjustment amount are read out and the DA
Since the configuration is such that the set power is generated by conversion, the circuit scale does not become relatively large, and even if the number of resolutions or fine adjustment steps increases, the circuit scale does not increase. Also, setting values can be easily changed by simply rewriting the memory contents or changing the ROM.

00
[48] Furthermore, according to the present invention, a plurality of setting value tables corresponding to the resolution and adjustment amount are prepared in correspondence with the print thickness and stored in the storage unit, and the print thickness specification data generation unit The print thickness can be controlled by reading a set value from a table indicated by the print thickness designation data based on the resolution designation data and the adjustment amount designation data and inputting it to the DA converter.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention.

FIG. 2 is a configuration diagram of an embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between ROM data and switch on/off states.

FIG. 4 is a configuration diagram of a second embodiment of the present invention.

FIG. 5 is an explanatory diagram of first ROM data.

FIG. 6 is an explanatory diagram of second ROM data.

FIG. 7 is an explanatory diagram of third ROM data.

FIG. 8 is a configuration diagram of a third embodiment of the present invention.

FIG. 9 is a relationship diagram between a ROM data selection signal and ROM data.

[Explanation of symbols]

11...Memory unit (ROM) 12...Resolution specification data generation section 13...Adjustment amount specification data generation section 14...DA converter 16... Comparison section 18...Laser diode drive circuit 19...Laser diode 20... Laser output detection section

Claims (2)

[Claims] [Claim 1] A laser output from a laser diode.
In the laser output control device of a laser printer, the laser power is compared with the set value and the laser is driven based on the difference to set the laser power to the set value. and a storage section that stores setting values for fine adjustment of each resolution, a resolution specification data generation section that generates data that specifies the resolution, an adjustment amount specification data generation section that generates data that specifies the amount of fine adjustment of the resolution, and a resolution specification. A DA converter converts the set value read from the storage unit into digital/analog by combining data and adjustment amount designation data as address data in the storage unit, and converts the setting value read from the storage unit into digital/analog data based on the difference between the laser power and the output of the DA converter. 1. A laser output control device comprising a laser diode drive circuit for driving a laser diode. 2. A plurality of sets of setting value tables corresponding to the resolution and adjustment amount are prepared in correspondence with print thickness and stored in the storage unit, and a print thickness specification data generation unit is provided, 2. The laser output control device according to claim 1, wherein the set value is read from a table indicated by the print thickness designation data based on the resolution designation data and the adjustment amount designation data, and inputted to the DA converter. .