JPH08171061A - Beam scanning device - Google Patents

Abstract

PURPOSE: To prolong the life of a semiconductor laser array outputting plural beams, to reduce the exchange by reason of the life and to suppress the running cost of a device using the semiconductor laser array. CONSTITUTION: An available LD selecting means 31 judges the light emitting efficiency of each laser diode or whether or not it is used from the contents of a control signal for drive controlling a laser diode stored in a memory 33 or whether or not the laser diode is used at the time of a previous job or at the time of printing the previous page, etc., and selects a laser diode to be used next from among laser diodes in a semiconductor laser array 1. A LD control means 32 drives/controls a laser diode selected by the available LD selecting means 31 and controls the light quantity of the semiconductor laser diode array 1 at the time of starting. Consequently, a less deteriorated laser diode is selected preferably and the respective laser diodes are equally used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam scanning device,
In particular, scanning a plurality of laser beams on the medium to be scanned,
It is a beam scanning device capable of obtaining a plurality of images of different resolutions on a medium to be scanned by switching the number of beams.

[0002]

2. Description of the Related Art In recent years, in devices using semiconductor lasers such as laser printers, copying machines, and facsimile machines,
Image quality and resolution are rapidly increasing. In order to deal with this, Japanese Patent Laid-Open No. 52-119938 (hereinafter, referred to as known document 1) discloses that only one semiconductor laser is provided by switching the video clock frequency and the rotation speed of the photoconductor driving motor. Discloses a technique in which the pixel density is changed to obtain a high resolution image. Further, Japanese Patent Laid-Open No. 1-299042 (hereinafter, referred to as known document 2
Has a device for simultaneously scanning a plurality of beams in parallel, and the number of scanning beams to obtain a plurality of resolutions, or the rotation speed of a scanner motor for scanning the beams is set to a desired resolution. A technique is disclosed that is adapted and changed. In this publication, a plurality of beams are simultaneously scanned in parallel so that a high resolution image can be obtained even with a scanner motor having a low rotation speed. On the other hand, when a low resolution image is requested, only one beam of the plurality of beams is used to obtain the low resolution image.

In Japanese Patent Laid-Open No. 3-287181 (hereinafter referred to as known document 3), an optimum beam diameter is selected from a plurality of beams having different beam diameters in accordance with a desired resolution. A technique is disclosed in which a beam having a beam diameter is switched to obtain an image with a desired resolution. Further, Japanese Patent Laid-Open No. 4-246877 (hereinafter, referred to as known document 4
If two semiconductor lasers are provided, one of the semiconductor lasers should be selected and operated, or another semiconductor laser should be selected and operated. This technology is disclosed.

[0004]

In the conventional beam scanning devices described in the above-mentioned prior art documents 1 to 3, a plurality of beams are used when a high resolution image is obtained, and light is emitted when a low resolution image is obtained. The use of a reduced number of beams is not taken into consideration, and the fact that there is a difference in the degree of aging deterioration among a plurality of beams is not taken into consideration. That is, even when a certain semiconductor laser is frequently used and deteriorates quickly to reach the end of its life, the certain semiconductor laser is rarely used and the degree of deterioration may be small. For example, as shown in FIG. 9, two laser diodes L are provided in a semiconductor laser array.
When Da and LDb are present, the luminous efficiencies of the laser diodes LDa and LDb in the initial stage are almost equal,
The difference in the amount of drive current required for light emission is small. However, either laser diode (LD in this case)
When the frequency of use of b) is higher than the frequency of use of the other laser diode (LDa in this case), there is a difference in the luminous efficiency of the laser diodes LDa and LDb after aging, and the difference in the drive current amount required for light emission is growing. Therefore, in the laser array composed of the plurality of semiconductor lasers, even one of the semiconductor lasers has a life,
If the performance is extremely deteriorated, the entire laser array must be replaced, which is very uneconomical. Further, there is a problem that means for extending the life of a plurality of semiconductor lasers in such a laser array is not considered.

Further, in the above-mentioned known document 4, the life of the semiconductor laser is doubled, but only two semiconductor lasers are used one by one. If the two semiconductor lasers are used at the same time to obtain a high-resolution image, there is a problem that the life of the semiconductor lasers cannot be extended as planned. An object of the present invention is to eliminate the above-mentioned problems of the prior art, extend the life of a semiconductor laser array that outputs a plurality of beams as much as possible, reduce the replacement due to the life, and improve the device using the semiconductor laser array. An object of the present invention is to provide a beam scanning device that can reduce running costs.

[0006]

In order to achieve the above-mentioned object, the invention of claim 1 stores a memory for storing a value of a control signal for individually driving and controlling a plurality of semiconductor lasers, and a memory for storing in the memory. LD selection means for determining whether the emission efficiency of the semiconductor laser is high or low based on the control signal for driving and controlling each semiconductor laser, and selecting the semiconductor laser having high emission efficiency for use in the next beam scanning. When,
It is characterized in that it is provided with an LD control means for driving and controlling the semiconductor laser selected by the used LD selection means and for controlling the light quantity of the semiconductor laser array when the apparatus is started. According to the invention of claim 2, whether or not each semiconductor laser is used is determined from a memory that stores which semiconductor laser was used when printing was performed in the previous job and the contents stored in the memory. Then, the LD to be used is selected to use the semiconductor laser different from the semiconductor laser used in the previous job at the time of the next beam scanning.
It is characterized in that it is provided with selection means and LD control means for driving and controlling the semiconductor laser selected by the used LD selection means and for controlling the light quantity of the semiconductor laser array when the apparatus is started. The invention of claim 3 is
3. The semiconductor laser according to claim 2, wherein the memory is a memory that stores which semiconductor laser was used when the previous page was printed, and the used LD selection means selects each semiconductor laser from the contents stored in the memory. It is characterized in that it is a used LD selection means for judging whether or not the semiconductor laser is used and selecting a semiconductor laser different from the semiconductor laser used in the previous page.

[0007]

According to the first aspect of the present invention, the used LD selection means preferentially selects and uses a semiconductor laser having a small value of the control signal and a high luminous efficiency. Further, according to the invention of claim 2, the used LD selection means preferentially selects and uses a semiconductor laser different from the semiconductor laser used in the previous job for each job. Further, according to the invention of claim 3, the used LD selection means preferentially selects and uses a semiconductor laser different from the semiconductor laser used in the previous page for each page. For this reason,
According to the present invention, each semiconductor laser of the semiconductor laser array can be used evenly, and the life of the semiconductor laser array can be extended.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 2 is a plan view showing a main configuration of a beam scanning device according to an embodiment of the present invention, and FIG. 3 is a side view of the same. 2 and 3, reference numeral 1 denotes two laser diodes LDa.
And LDb, and a photodiode for detecting the amount of light emitted from the laser diodes LDa and LDb. Reference numerals 2 and 3 are lenses through which the laser beams 9 and 10 emitted from the laser diodes LDa and LDb respectively pass, and 4 is a mirror that reflects the laser beams 9 and 10. Reference numeral 5 denotes a rotary polygon mirror which has a plurality of reflecting surfaces and which is rotated in the direction of arrow A by a driving source (not shown). , 10 are reflected, and the laser beams 9 and 10 reach the photoconductor 11 via the scanning lens 6 and the cylinder lens 7. Since the rotary polygon mirror 5 rotates in the direction of arrow A, the laser beams 9 and 10 scan the photoconductor 11 in the direction of arrow B. The scanning lens 6 and the cylinder lens 7 transfer the laser beams 9 and 10 to the photoconductor 11
It is provided between the rotary polygon mirror 5 and the photoconductor 11 in order to scan at a constant speed.

Reference numeral 8 denotes an optical position detector composed of a photoelectric conversion element such as a photodiode, which detects the laser beams 9 and 10 reflected by the mirror 8a and synchronizes the optical laser beam generation position with the modulation signal. Detection signal (S
OS) is generated. The photoconductor 11 is rotatably supported by, for example, a housing (not shown) of the image forming apparatus, and is rotated at a predetermined speed in the direction of arrow D by a drive source (not shown). Around this photoconductor 11, the photoconductor 1
1. A charger, an exposure device, for uniformly charging the surface layer of 1.
Although a developing device, a transfer device, and the like are provided, they are not shown because they are not the main part of this embodiment. In addition, in FIG.
In order to clearly show the optical paths of the laser beams 9 and 10, the axis of the rotary polygon mirror 5 is illustrated as being inclined for convenience. Although the photosensitive member 11 is described as a drum-shaped member in the drawing, it is not limited to this and may be a flat plate-shaped member or the like.

Next, a light quantity control device for setting the light quantity of the laser beam emitted from the semiconductor laser array 1 will be described. FIG. 4 is a block diagram showing a circuit of the light quantity control device. In the figure, reference numerals 12 and 13 denote modulators (hereinafter referred to as switches) that are turned on or off by video signals Video.a and Video.b, respectively. The switches 12 and 13 are video signals Video. When a and Video · b are respectively at a high level, they are closed, and as a result, a current flows through the laser diodes LDa and LDb. Reference numerals 14 and 15 denote the laser diodes LDa,
A constant current circuit for supplying a constant current to LDb, 16 is a current / voltage converter (I / V) for converting current into voltage, 17, 18
And 20 are D / A converters for converting digital signals into analog signals, and 19 is the current / voltage converter 16
From the D / A converter 20 and the reference voltage V from the D / A converter 20.
It is a comparator for comparing ref.

Reference numeral 21 denotes a control signal Da via the D / A converter 17, and control signal D via the D / A converter 18.
CPU 22 for outputting b to the constant current circuits 15 and 14 and giving an instruction to a video control circuit 22 described later.
Is a video signal Vi based on image information supplied from the outside.
A video control circuit for outputting deo.a and Video.b and supplied to the switches 12 and 13, respectively, is a keyboard for giving the CPU 21 an instruction from an operator, for example, an instruction of a print mode. The video control circuit 22 outputs video signals Video.a and Video.b to the switches 12 and 13 based on an instruction from the CPU 21 or image information supplied from the outside.

The photodiode PD provided in the semiconductor laser array 1 is the laser diode L.
Both the outputs from Da and LDb can be made incident. Further, the photodiode PD has a cathode connected to a power source, and an anodized one is a current / voltage converter (I / V).
It is connected to one input side of the comparator 19 via 16. Further, the laser diode LDa and the switch 1
2 and the constant current circuit 15 are connected in series between the power source and the ground, and similarly, the laser diode LDb and the switch 1 are connected.
3 and the constant current circuit 14 are also connected in series between the power supply and ground. The current flowing through the laser diode LDa is determined by the control signal Da supplied to the constant current circuit 15. The control signal Da is supplied from the CPU 21 via the D / A converter 17. Similarly, the current flowing through the laser diode LDb is determined by the control signal Db supplied from the CPU 21 to the constant current circuit 14 via the D / A converter 18.

Further, the laser diodes LDa and LD
When a current flows through b, a laser beam having an intensity corresponding to the current is emitted, and a current due to the reception of the laser beam flows through the photodiode PD. This current is converted into the voltage Vmon and input to the comparator 19 as described above. A reference voltage Vref corresponding to the target light amount is supplied to the other input side of the comparator 19. The reference voltage Vref is the signal Dd output from the CPU 21 that is D / A converted by the D / A converter 20. The output signal Dc of the comparator 19 becomes a high level signal “H” when one input signal Vmon of the comparator 19, that is, a signal having a magnitude corresponding to the amount of light detected by the photodiode PD is larger than the reference voltage Vref. The output signal of the comparator 19 is the CPU
21. The CPU 21 uses the comparator 19
The control signals Da and Db are increased stepwise in a predetermined cycle until the output signal Dc of "H" becomes "H", and when the output signal Dc becomes "H", these control signals Da, Db are fixed.

Next, the light amount control operation at the time of starting the image output device will be described with reference to the drawings. FIG. 5 is a timing chart showing the operation of controlling the light amount of the laser beam performed at the time of starting the image output device. First, in the figure, at timing t1, the video signal Video.a is set to a high level signal and the control signal Da is raised stepwise to increase the light quantity of the laser diode LDa. The detection result, that is, the signal Vmon also increases. Then, when the signal Vmon reaches the reference signal Vref, that is, at the timing t2, the output signal Dc of the comparator 19 changes to “H”. After the output signal Dc changes to "H", the video signal Vi is output at the timing t3.
The control signal Da is fixed by setting deo · a to a low level signal. When the video signal Video.a is set to a low level signal, the current stops flowing through the laser diode LDa,
The output signal Dc of the comparator 19 changes to "L".

Similarly, at timing t4, the video signal V
When the signal ide · b is set to a high level signal and the control signal Db is raised stepwise to increase the light amount of the laser diode LDb, the signal Vmon also increases accordingly. Then, the output signal Dc of the comparator 19 changes to "H" at the timing t5 when the signal Vmon reaches the reference signal Vref. After the output signal Dc changes to "H", the video signal Video.b is set to a low level signal at timing t6 to fix the control signal Db. Video signal Video
When b is a low level signal, the laser diode LDb
No current flows to the output signal D of the comparator 19
c changes to "L". As described above, the laser diodes LDa and LDb can be adjusted so as to emit laser beams having the same light amount.

Next, the operation of the first embodiment of the laser printer to which the beam scanning device of the present invention is applied will be described. FIG. 6 is a flowchart showing the operation of selecting the laser diode to be used by comparing the magnitudes of the control signals Da and Db. First, in step S1, light amount control of the laser diodes LDa and LDb is performed. This light amount control is performed as shown in FIG. 5, and the laser diode L
Da and LDb are adjusted so as to emit laser beams having the same light amount. In step S2, the control signals Da and Db fixed at the timings t3 and t6 shown in FIG. 5 are stored. The control signals Da and Db are stored in, for example, a memory (not shown), a memory provided in the CPU 21, or the like. In step S3, the keyboard 23 is instructed by an external device or is operated by an operator.
High-resolution printing (HRP) mode input from
Alternatively, the designation of the low resolution printing (LRP) mode is read.

In step S4, the print mode specified in step S3 is H.264. R. P. It is determined whether or not the mode. If this determination is affirmative, the process proceeds to step S5, while if the determination is negative, the process proceeds to step S7. In step S5, the CPU 21 causes the laser diode L
In addition to designating the use of Da and LDb, the video control circuit 22 receives a video signal V in response to an instruction from the CPU 21.
Use video.a and Video.b as image information. In step S6, the laser diodes LDa and LDb
High-resolution printing is performed using the and ends. The resolution of the image obtained by the high resolution printing is, for example, 6
In the case of 00SPI, two laser diodes are simultaneously scanned, and the rotation speed of the motor for scanning the laser beam is K.
(Rpm).

At step S7, the control signals Da and Db are sent.
, It is determined whether or not Da ≦ Db. If this determination is affirmative, the process proceeds to step S8, and step S5 is performed.
Similarly, the use of laser diode LDa is specified,
Video signal Video.a is image information, and Video.b is the same.
Is turned off. On the other hand, if negative, step S1
0, the use of the laser diode LDb is designated and the video signal Vide is specified as in steps S5 and S8.
o · a is a no signal, and Video · b is the image information.
In step S9, low resolution printing is performed using the laser diode LDa or LDb, and the process ends. When the resolution of the image obtained by the low resolution printing is, for example, 300 SPI, one laser diode is scanned and the rotation speed of the motor for scanning the laser beam is K (rpm).

As described above, in the case of low resolution printing, a laser diode having a high luminous efficiency, that is, a laser diode which is not so deteriorated is preferentially selected and used. Therefore, the laser diodes LDa, L
Db can be used almost equally. Therefore,
It is possible to prevent the emission efficiency of the laser diodes LDa and LDb after aging from becoming substantially equal to each other, and it is possible to prevent only one of the laser diodes LDa and LDb from reaching the end of its life first. Therefore, it is possible to prevent the semiconductor laser array 1 from being unnecessarily exchanged, to effectively use the semiconductor laser array 1, and to keep the running cost of the apparatus low.

Next, the operation of the second embodiment will be described. FIG. 7 is a flowchart showing the operation of selecting the laser diode to be used for each job. At the time of starting the printer to which the beam scanning device of this embodiment is applied,
R. P. Since the operation of the mode is the same as that of the first embodiment, it is omitted, the low resolution printing (LRP) mode is designated in step S3 of FIG. 6, and the determination in step S4 is negative. The case will be described. Step S
At 21, the laser diode used in the previous job is read from the memory storing whether or not the laser diode is used. Here, the laser diode is a laser diode LDa. In step S22,
A different one from the read laser diode is specified,
The video signal is converted into image information. Here, the laser diode LDb is designated and the video signal V
video / b is used as image information. In step S23,
Low resolution printing is performed using the laser diode designated in step S22, and the fact that the laser diode has been used is stored in the memory, and the process ends.
As described above, the laser diodes LDa and LD
By alternately using b for each job, the laser diodes LDa and LDb can be used almost uniformly. Further, the laser diodes LDa and LDb can be used almost equally even when the error in the current value output from the constant current circuits 14 and 15 is large with respect to the control signals Da and Db.

Next, the operation of the third embodiment will be described. FIG. 8 is a flowchart showing the operation of selecting the laser diode to be used for each page of printing. Similar to the second embodiment, the description of the same operation as in the first embodiment is omitted, the low resolution printing (LRP) mode is designated in step S3 of FIG. 6, and the determination in step S4 is made. The case of denial will be described. In step S31, the laser diode used on the previous page is read from the memory. Here, the laser diode is a laser diode LDa. In step S32, a laser diode different from the read laser diode is designated, and the video signal is used as image information. Here, the laser diode LDb is designated and
The video signal Video.b is converted into image information. In step S33, low resolution printing is executed using the laser diode specified in step S32, and the fact that the laser diode has been used is stored in the memory, and the process ends. As described above, by alternately using the laser diodes LDa and LDb for each page, the laser diodes LDa and LDb can be used almost uniformly.

Next, the functional configuration of the present invention will be described with reference to the block diagram of FIG. In the figure, 31 is a memory 3
LD selection means for selecting the laser diode to be used next from the plurality of laser diodes in the semiconductor laser array 1 by judging the luminous efficiency of each laser diode or the presence / absence of use from the contents stored in 3. Is.
Reference numeral 32 is an LD control means for driving and controlling the laser diode selected by the used LD selection means 31, and for controlling the light quantity of the semiconductor laser array 1 when the apparatus is started. The memory 33 stores a control signal for driving and controlling the laser diode and whether or not each laser diode is used at the time of printing the previous job or the previous page. Reference numeral 34 is a print mode input means for inputting a print mode designation command.

Next, the operation of the block diagram of FIG. 1 will be described. First, the used LD selection means 31 reads from the memory 33 the control signals Da and Db, or data regarding whether or not the laser diode is used at the time of printing the previous job or the previous page. When the used LD selection means 31 reads the control signals Da and Db, the used LD selection means 31 compares the control signals Da and Db with each other and selects the laser diode driven by the smaller control signal. On the other hand, when the used LD selection means 31 reads out whether or not the laser diode is used during the previous job or the printing of the previous page, the used LD selection means 31 selects a laser diode different from the used laser diode. To do. Then, the LD control means 32 determines the LD to be used.
The laser diode selected by the selection means 31 is driven and controlled.

In each of the above embodiments, the semiconductor laser array 1
Laser diodes LDa, LDb
However, the present invention is not limited to this.
The number of laser diodes may be three or more. Also,
In each of the above-described embodiments, the case where the beam scanning device is used in the laser printer is described, and the keyboard 2 is used to instruct the print mode.
However, if a facsimile machine is used, the instruction may be given by the resolution information included in the facsimile communication protocol. When the laser printer is connected to information equipment such as a computer, the print mode follows the instructions from these information equipment. Further, by adding the function of the first embodiment to the function of the second and third embodiments, when there is a large difference in deterioration due to aging of the laser diodes LDa and LDb, the laser diodes LDa and LDb are alternately switched. It is also possible to select and use a laser diode with less deterioration without using it.

[0025]

As is apparent from the above description, according to the invention of claim 1, the used LD selection means reads the value of the control signal for driving each semiconductor laser of the semiconductor laser array from the memory. And the comparison is performed to determine whether the emission efficiency of each semiconductor laser is high or low. From this judgment, the semiconductor laser having a small control signal value and a high light emission efficiency is preferentially selected, and the LD control means emits the semiconductor laser. Therefore, the semiconductor lasers are used evenly, and even after aging, the emission efficiency of the semiconductor lasers does not vary. Therefore, among the semiconductor lasers,
Only one of them will not reach the end of its life soon. Therefore, the semiconductor laser array can be effectively used, the frequency of exchanging the semiconductor laser array can be reduced, and the running cost of the device can be kept low.

According to the second aspect of the present invention, the used LD selection means preferentially selects and uses the semiconductor laser which is not used in the previous job for each job.
Therefore, each semiconductor laser of the semiconductor laser array can be used evenly, and the life of the semiconductor laser array can be extended. Further, even when the output of the driving power source for driving the respective semiconductor lasers corresponding to the control signal is different, the respective semiconductor lasers can be used almost equally. According to the invention of claim 3, the used LD selection means preferentially selects and uses a semiconductor laser not used in the previous page for each page. Therefore, each semiconductor laser of the semiconductor laser array can be used evenly, and the life of the semiconductor laser array can be extended.

[Brief description of drawings]

FIG. 1 is a block diagram showing a functional configuration of the present invention.

FIG. 2 is a plan view showing a main configuration of an image output apparatus according to an embodiment of the present invention.

FIG. 3 is a side view of FIG. 2;

FIG. 4 is a block diagram showing a circuit of a light quantity control device.

FIG. 5 is a timing chart showing an operation of controlling the light amount of a laser beam performed at the time of starting the image output device.

FIG. 6 is a flowchart showing an operation of selecting a laser diode to be used by comparing the magnitudes of control signals.

FIG. 7 is a flowchart showing an operation of selecting a laser diode to be used for each job.

FIG. 8 is a flowchart showing an operation of selecting a laser diode to be used for each page.

FIG. 9 is an explanatory diagram showing characteristics of a driving current and a light output of a semiconductor laser.

[Explanation of symbols]

1 ... Semiconductor laser array, 2, 3 ... Lens, 4 ... Mirror, 5 ... Rotating polygon mirror, 6 ... Scan lens, 7 ... Cylinder lens, 8 ... Optical position detector, 9, 10 ... Lens, 11 ... Photoconductor, 12, 13 ... Switch, 14, 15 ... Constant current circuit, 16 ... Current / voltage converter, 17, 18, 20 ... D /
A converter, 19 ... Comparator, 21 ... CPU, 22 ...
Video control circuit, 23 ... Keyboard, 31 ... Used LD selection means, 32 ... LD control means, 33 ... Memory, 34 ... Print mode input means.

Claims (3)

[Claims] 1. A semiconductor laser array comprising a plurality of semiconductor lasers and photodiodes, wherein a plurality of laser beams output from the semiconductor laser array are simultaneously or independently scanned on a medium to be scanned to obtain a plurality of laser beams. In a beam scanning device for obtaining an image of the resolution of, a memory storing a value of a control signal for driving and controlling the semiconductor laser, and a control signal for driving and controlling each semiconductor laser stored in the memory, Use LD selection means for determining whether the emission efficiency of the semiconductor laser is high or low and selecting the semiconductor laser having high emission efficiency for use in the next beam scanning, and driving control of the semiconductor laser selected by the use LD selection means And an LD control means for controlling the light amount of the semiconductor laser array when the apparatus is started. Beam scanning device. 2. A semiconductor laser array comprising a plurality of semiconductor lasers and photodiodes, wherein a plurality of laser beams outputted from the semiconductor laser array are simultaneously or independently scanned on a medium to be scanned to obtain a plurality of laser beams. In the beam scanning device that obtains the image of the resolution of, the memory that stores which semiconductor laser was used when printing in the previous job, and whether or not each semiconductor laser is used, based on the contents stored in the memory. And selecting a semiconductor laser different from the semiconductor laser used in the previous job for use in the next beam scanning, and driving the semiconductor laser selected by the use LD selecting means. LD control means for controlling the light quantity of the semiconductor laser array when the apparatus is started. Characteristic beam scanning device. 3. The semiconductor memory is a memory that stores which semiconductor laser was used when a previous page was printed, and the used LD selection means selects each semiconductor from the contents stored in the memory. 3. The beam scanning apparatus according to claim 2, further comprising a used LD selection unit configured to determine whether or not a laser is used and select a semiconductor laser different from the semiconductor laser used on the previous page.