JP2001253111A - Controller for quantity of light - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller for the quantity of light in which the lifetime of a photosensitive body can be prolonged without relying upon a conventional regulation method for scanning the same part of the photosensitive body continuously with intensive light. SOLUTION: At first, a CPU 84 lights the LD of a reference light source, i.e., a semiconductor laser 36K, and then increases the value of data to a D/A converter 85K gradually such that a target quantity of light is detected by means of a PD thus increasing the drive current of the LD. After ending regulation of the quantity of light of the semiconductor laser 36K, the quantity of light is regulated by lighting the LD of the semiconductor laser 36K at the detection timing of a light beam emitted from the LD of the semiconductor laser 36K in a non-imaging region. According to the arrangement, a photosensitive body is not irradiated with the light beam from a semiconductor laser 36 other than the reference light source when regulating the quantity of light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light quantity control device, and more particularly to a method of scanning a plurality of beams on a photosensitive member and combining a plurality of images formed on the photosensitive member as a single image. The present invention relates to a light amount control device used in an image forming apparatus such as a laser printer for outputting.

[0002]

2. Description of the Related Art A laser beam emitted from a laser diode is reflected by a rotating polygon mirror to optically scan a photoreceptor to form an electrostatic latent image. Then, toner is adhered to the electrostatic latent image and developed. A laser beam printer which forms an image or the like by transferring it onto a recording paper is generally well known.

[0003] When a printer performs a recording operation, the laser light must maintain a constant brightness. However, if the brightness fluctuates, the recorded image becomes uneven and the recording quality deteriorates.

[0004] The laser diode starts oscillating when the power is turned on, the emitted light quantity gradually increases, and eventually reaches a predetermined light quantity. Even after reaching a predetermined light amount, the light amount is likely to fluctuate due to various ambient conditions. Therefore, always check to maintain a certain amount of light,
And need to be adjusted.

In light quantity adjustment, first, a laser diode is turned on, and this light is received by an optical sensor to detect the light quantity. Then, the light amount is increased or decreased based on the detection result, and adjustment is performed so as to maintain a predetermined light amount.

However, in the conventional printer, the laser light continuously turned on for detecting the light amount is simultaneously reflected by the rotary polygon mirror and scans the photosensitive member. If the photoconductor does not move when adjusting the light amount, the same portion of the photoconductor is optically scanned many times, and as a result, the photoconductor locally fatigues, and the life of the photoconductor is significantly reduced. There was a problem.

On the other hand, Japanese Patent No. 2739215 discloses that the sensitivity of an optical sensor for detecting light at the head of a scanning line is set higher than that of a photosensitive member, and the optical sensor serves as a reference for writing timing. A technique is disclosed in which the adjustment is performed continuously when the power is turned on without generating the synchronization detection signal.

In this technique, when a light amount increases and a synchronization detection signal is generated, a laser diode is turned on only in a non-image forming area in synchronization with the synchronization signal, and the light amount is increased to a target light amount set value. I am adjusting.

[0009]

However, in the above-mentioned prior art, the sensitivity of the optical sensor is set higher than that of the photoreceptor. Therefore, when the light beam is scanned, the light reflected by a wall or the like in the image forming apparatus is used. Sensor malfunctions,
There was a problem.

Further, when this technique is applied to an image forming apparatus using a plurality of light sources for forming a color image, a circuit for adjusting the light amounts of the plurality of light sources is required, and the circuit configuration becomes complicated. There was also a problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and extends the life of a photosensitive member without employing a conventional adjustment method of continuously scanning the same portion of the photosensitive member with intense light. It is an object of the present invention to provide a light amount control device capable of performing the following.

[0012]

In order to achieve the above object, according to the present invention, a plurality of light sources, scanning means for scanning light beams emitted from the plurality of light sources on a photosensitive member, A light beam detector that detects a light beam emitted from a predetermined reference light source among the plurality of light sources in a non-image forming area of a main scanning area of the light beam; and a light beam emitted from the plurality of light sources. A plurality of light amount detecting means for detecting the amount of light, a plurality of drive current supply means for supplying a drive current for lighting the plurality of light sources, and the reference light source is continuously turned on and emitted from the reference light source. After controlling the drive current of the reference light source such that the light amount of the light beam reaches the target light amount, the reference light source and the reference light source in the non-image forming area are synchronized with the detection timing of the light beam detection means. Control means for controlling the drive currents of the light sources other than the reference light source such that the light source is turned on and the light amount of the light beam emitted from the light source other than the reference light source becomes the target light amount. I do.

According to the present invention, first, a predetermined reference light source among a plurality of light sources is continuously turned on to perform light amount control. That is, for example, the light amount of the light beam emitted from the reference light source is detected, the detected light amount is compared with the target light amount, and the drive current for turning on the reference light source is gradually increased until the detected light amount reaches the target light amount. .

Then, at the detection timing of the light beam detecting means, that is, at the timing of detecting the light beam emitted from the reference light source in the non-image forming area, the light amount adjustment of the light sources other than the reference light source, that is, the control of the drive current is performed. As described above, the light sources other than the reference light source are turned on only in the non-image forming area to perform the same light amount adjustment as that of the reference light source.

As described above, the light amount is adjusted by continuously lighting only the reference light source, and the other light sources are lighted only in the non-image forming area to adjust the light amount. In addition, it is possible to prevent the photoconductor from deteriorating. Therefore, the life of the photoconductor can be extended.

Further, the control means may determine a drive current value initially supplied to a light source other than the reference light source based on the drive current value of the reference light source. You may. That is, after performing the light amount adjustment of the reference light source, for example, a drive current value lower than the drive current value of the reference light source corresponding to the target light amount is set as a drive current value to be initially supplied to the light sources other than the reference light source. The light amount is adjusted by gradually increasing the drive current value from the set drive current value. For this reason, the time for adjusting the light amount of the light sources other than the reference light source can be significantly reduced.

Further, the control means may randomly determine the reference light source from the plurality of light sources at the time of starting up or restarting the light amount control device. .

For example, when the light amount control device is started up or restarted, a reference light source is determined from a plurality of light sources using, for example, a random number or the like prior to light amount adjustment. As a result, since the light source that is continuously turned on changes, it is possible to prevent a specific photoconductor from deteriorating.

The control means may determine the reference light source from the plurality of light sources in a predetermined order when the light amount control device is started up or restarted. It may be. As described above, by changing the reference light source in a predetermined order, it is possible to prevent a specific photoconductor from being deteriorated.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] An example of a first embodiment of the present invention will be described below in detail with reference to the drawings.
FIG. 1 shows a so-called spray paint type color image forming apparatus 10 as an image forming apparatus according to the present invention. The color image forming apparatus 10 includes three transport rollers 1
2A to 12C, an endless transfer belt 14 wound around transport rollers 12A to 12C, and a transfer roller 16 disposed opposite to the transport roller 12C with the transfer belt 14 interposed therebetween.
And

Above the transfer belt 14, the transfer belt 1
The photosensitive drum 18K for forming a black (K) image and the photosensitive drum 18Y for forming a yellow (Y) image along the moving direction of the transfer belt 14 (the direction of arrow A in FIG. 1) when the roller 4 is driven to rotate. , A photosensitive drum 18M for forming a magenta (M) image and a photosensitive drum 18C for forming a cyan (C) image are arranged at substantially equal intervals. Each photoreceptor drum 18 is arranged such that the axis is orthogonal to the moving direction of the transfer belt 14.

In the following, for the portions provided for each of the colors K, Y, M, and C, the codes of the respective portions are denoted by K in the same manner as described above.
It is distinguished by adding the symbol of / Y / M / C.

Around each photoreceptor drum 18, a charger 20 for charging the photoreceptor drum 18 is disposed, and above each of the photoreceptor drums 12, there is provided a charger 20. A plurality of beam scanning devices 30 (details of which will be described later) for irradiating laser beams onto the photosensitive drums 18 to form electrostatic latent images on the respective photosensitive drums 18 are arranged.

An electrostatic latent image formed on the photosensitive drum 18 is formed around each photosensitive drum 18 at a position downstream of the laser beam irradiation position along the rotation direction of the photosensitive drum 18. A developing unit 22 for developing a color (K or Y or M or C) toner to form a toner image; a transfer unit 24 for transferring the toner image formed on the photosensitive drum 18 to the transfer belt 14; Are sequentially disposed.

The toner images of different colors formed on the respective photosensitive drums 18 are transferred to the transfer belt 14 so as to overlap each other on the belt surface of the transfer belt 14. Thus, a color toner image is formed on the transfer belt 14, and the formed color toner image is transferred to the transfer material 28 sent between the transport roller 12 </ b> C and the transfer roller 16. Then, the transfer material 28 is sent to a fixing device (not shown), and the transferred toner image is fixed. Thus, a color image (full color image) is formed on the transfer material 28.

Next, the multi-beam scanning device 30 will be described with reference to FIGS. Multiple beam scanning device 30
Is a casing 32 having a substantially rectangular bottom shape (see also FIG. 3).
And a rotary polygon mirror 34 that is rotated at a high speed by a motor (not shown) is disposed at a substantially central portion of the casing 32. A photosensitive drum 18 is attached to one end of the casing 32 along a direction orthogonal to the axis of the rotary polygon mirror 34.
A semiconductor laser (hereinafter, referred to as LD) 36K for emitting a laser beam for irradiating K and an LD 36Y for emitting a laser beam for irradiating the photosensitive drum 18Y are arranged near the corners, respectively.

A collimator lens 38K and a plane mirror 40 are arranged in this order on the laser beam emitting side of the LD 36K. The laser beam K emitted from the LD 36K is converted into a parallel light beam by the collimator lens 38K and is incident on the plane mirror 40. A collimator lens 38Y and a plane mirror 42 are arranged in this order on the laser beam emission side of the LD 36Y. The laser beam Y emitted from the LD 36Y is converted into a parallel light beam by the collimator lens 38Y and then reflected by the plane mirror 42. The plane mirror 40
Is incident on.

An fθ lens 44 is disposed between the plane mirror 40 and the rotary polygon mirror 34. The laser beam K and the laser beam Y reflected by the plane mirror 40 are fθ
After passing through the lens 44 and entering the rotary polygon mirror 34 and being reflected and deflected by the rotary polygon mirror 34, the fθ lens 4
4 (a so-called double-pass configuration: see FIG. 1).

The LD 36K and the LD 36Y are a rotating polygon mirror 34.
Are different in the axial direction (corresponding to the sub-scanning direction), and the laser beam K and the laser beam Y are respectively incident on the rotary polygon mirror 34 at different incident angles along the sub-scanning direction. The laser beams K and Y transmitted twice through the fθ lens 44 are incident on separate plane mirrors 46K and 46Y.

The laser beam K is applied to the plane mirror 46.
Due to K, the light is incident on a cylindrical mirror 48K disposed at a position corresponding to a position above the photosensitive drum 18K, is emitted from the cylindrical mirror 48K toward the photosensitive drum 18K, and is scanned on the peripheral surface of the photosensitive drum 18K. . Further, the laser beam Y is incident on the cylindrical mirror 48Y arranged at a position corresponding to the upper side of the photosensitive drum 18Y by the plane mirror 46Y, and is emitted from the cylindrical mirror 48Y toward the photosensitive drum 18Y. The peripheral surface of 18Y is scanned.

Incidentally, as shown in FIG.
Is entirely concealed by a lid 50. Lid 5
0, a rectangular opening 50A through which a laser beam passes is formed.
8K and 48Y are arranged on the upper surface of the lid 50 so as to straddle the opening 50A.

On the other hand, an LD 36M for emitting a laser beam for irradiating the photosensitive drum 18M is provided at an end inside the casing 32 opposite to the position where the LDs 36K and LD 36Y are disposed across the rotary polygon mirror 34. LDs 36C for emitting a laser beam for irradiating the photosensitive drum 18C are arranged near the corners.

A collimator lens 38C and a plane mirror 52 are arranged in this order on the laser beam emitting side of the LD 36C. You. A collimator lens 38M and a plane mirror 54 are sequentially arranged on the laser beam emission side of the LD 36M, and the laser beam M emitted from the LD 36M is arranged.
Is converted into a parallel light beam by the collimator lens 38M, is reflected by the plane mirror 54, and is incident on the plane mirror 52.

An fθ lens 56 is disposed between the plane mirror 52 and the rotary polygon mirror 34, and the laser beam C and the laser beam M reflected by the plane mirror 52 are separated by fθ
After passing through the lens 56 and entering the rotary polygon mirror 34 and being reflected and deflected by the rotary polygon mirror 34, the fθ lens 5
6 is transmitted.

The LD 36C and LD 36M are rotating polygon mirrors 34.
Are different from each other in the axial direction (corresponding to the sub-scanning direction), and the laser beam C and the laser beam M are respectively incident on the rotary polygon mirror 34 at different incident angles along the sub-scanning direction. The laser beams C and M transmitted twice through the fθ lens 56 are incident on separate plane mirrors 46C and 46M.

The laser beam C is applied to the plane mirror 46.
By C, the light is incident on a cylindrical mirror 48C disposed at a position corresponding to a position above the photosensitive drum 18C, is emitted from the cylindrical mirror 48C toward the photosensitive drum 18C, and is scanned on the peripheral surface of the photosensitive drum 18C. . The laser beam M is incident on a cylindrical mirror 48M disposed at a position corresponding to a position above the photosensitive drum 18M by a plane mirror 46M, and is emitted from the cylindrical mirror 48M toward the photosensitive drum 18M. It is scanned on the 18M peripheral surface.

As is clear from the above, since the laser beams K and Y and the laser beams C and M are incident on the opposite surfaces of the rotary polygon mirror 34, as shown by arrows in FIG. , Y and the laser beams C, M are scanned in opposite directions. In addition, the cylindrical mirrors 48C, 4
As shown in FIG. 3, 8M is also arranged on the upper surface of the lid 50 so as to straddle an opening 50A formed in the lid 50 of the casing 32.

In the vicinity of the bottom of the casing 32, a pickup mirror (plane mirror) 5 is provided so as to cross the scanning trajectories of the laser beams K, Y, M, and C respectively reflected by the cylindrical mirrors 48K, 48Y, 48M, 48C.
8 are arranged. The pickup mirror 58 is located near the scanning start side end (SOS: Start Of Scan) of the laser beams K and Y in the scanning locus of the laser beam, that is, the scanning end side end (EOS: End Of S) of the laser beams M and C.
can).

As shown in FIG. 3, the lid 5 of the casing 32
An opening 50B is formed in the aperture 0 to allow each laser beam incident on and reflected by the pickup mirror 58 to pass therethrough. A sensor substrate 60 is disposed at a position where the laser beam that has passed through the opening 50B can be received. Have been. The sensor substrate 60 is mounted on the upper surface of the lid 50 via a bracket 62.

The laser beams K, Y, M and C scan across the sensor substrate 60 as shown by a dashed line in FIG. 4, for example. A main scanning position detection sensor 64 and a sub-scanning position detection sensor 66 are arranged on the sensor substrate 60 along the scanning trajectory of each laser beam.

The main scanning position detection sensor 64 determines the level of the output signal when the laser beam passes through the light receiving portion (the rectangular portion shown in FIG. 4) formed on the sensor chip and when the laser beam does not pass. Are optical sensors that output different signals.

The main scanning position detection sensor 64 determines the level of the output signal when the laser beam passes through the light receiving portion (the rectangular portion shown in FIG. 4) formed on the sensor chip and when the laser beam does not pass. Are optical sensors that output different signals.

FIG. 5 shows a configuration of a control system of the color image forming apparatus 10. As shown in FIG. 5, the color image forming apparatus 10 includes a clock 70, a horizontal synchronization circuit 71,
Main scanning position detection sensor 64, image writing timing generation circuit 72, main scanning operation circuit 73, sub-scanning operation circuit 7
4. A sub-scanning position detection sensor (PSD SNR) 66, a semiconductor laser 36, an M / C control circuit 77, and an image processing circuit 78 are provided. Further, the image writing timing generation circuit 72 includes a line start signal generation circuit 79,
A page start signal generation circuit 80 and an AND circuit 81 are provided.

The image processing circuit 78 has a function of processing a print command sent from a personal computer or the like.
The C control circuit 50 has a function of controlling the operation of the M / C (machine).

The clock synchronized with the main scanning position detection signal by the horizontal synchronization circuit 71 is sent to the image processing circuit 78 and the image writing timing generation circuit 72. As a result, synchronization with the image signal is achieved, and control is performed so that the timing of the image of each color is not disturbed.

The color misregistration in the main scanning direction is measured by the main scanning position detection sensor 64. The main scanning calculation circuit 73 calculates a color misregistration correction value from the measured value and outputs it to the line start signal generation circuit 79. The start timing of the line start signal is controlled based on this value.

The color shift in the sub-scanning direction is measured by the sub-scanning position detecting sensor 66. The sub-scanning operation circuit 74 calculates a color misregistration correction value from the measured value and outputs it to the page start signal generation circuit 80. The start timing of the page start signal is controlled based on this value.

The line start signal generation circuit 79 generates a line start signal based on the operation value output from the main scanning operation circuit 73 and outputs the signal to the AND circuit 81. The page start signal generating circuit 80 generates a page start signal based on the operation value output from the sub-scanning operation circuit 74 and outputs the page start signal to the AND circuit 81.

In the AND circuit 81, the logical product of the line start signal and the page start signal is obtained, and the image write signal 8
It becomes 2 and is sent to the image processing circuit 78 in synchronization with the horizontal synchronization signal. An image of each color is formed based on the image writing signal 82.

FIG. 6 is a circuit diagram showing a basic configuration of the light amount control unit 83 included in the M / C control circuit 77.

The light amount control unit 83 includes a CPU 84, a D / A converter 85, an LD drive circuit 86, a semiconductor laser 36,
An FET 87 and an AND circuit 88 are provided. In addition,
The LD drive circuit 86 and the semiconductor laser 36 are provided on an LD circuit board 89.

The CPU 84 controls the M / C portion of the color image forming apparatus 10, and includes an A / D converter (not shown) for converting an external analog signal into a digital signal.

The D / A converter 85 is connected to the ports P1, P3, P5, P7 of the CPU 84. The data supplied from these ports is for adjusting the output light amount of each LD 36 corresponding to each color of Y, M, C, and K. The data is converted into an analog signal by the D / A converter 85, and the LD drive circuit 86.

If the CPU 84 has a built-in D / A converter, the external D / A converter 85 can be omitted.

Next, the configuration of the LD circuit board 89 will be described with reference to FIG. 7 using a circuit configuration for one beam.

As shown in FIG. 7, a D / A converter (D
The input terminal of the AC 85 is connected to the output terminal of the CPU 84. The D / A converter 85 converts a digital signal input from the CPU 84 into an analog signal. D / A
An output terminal of the converter 84 is connected to a constant current source 91 to which a predetermined power supply voltage is applied. The constant current source 91 is D
Based on the analog signal input from the / A converter 84, a current value to be supplied to the LD 36 described later is set and output.

The output terminal of the constant current source 91 is connected to the current switching circuit 93, and the output terminal of the current switching circuit 93 is connected to the anode terminal of the laser diode 36A of the LD 36. In addition, the current switching circuit 9
3 is also connected to a CPU 84 from which an image forming signal 94 is input.

The current switching circuit 93 includes a constant current source 9
The current input from 1 is supplied to the laser diode 36A based on the image forming signal 94. Image forming signal 94
Is a CPU 84 based on image data of an image to be formed.
By using this signal to turn on the laser diode 36A, a light beam for forming an image on the photoconductor 18 can be obtained.

In this embodiment, the laser diode 36A is turned on when the image forming signal 94 is at a low level, and the light emitting element 36A is turned off when the image forming signal 94 is at a high level. The cathode terminal of the laser diode 36A is connected to the anode terminal of the photodiode 36 inside the LD 36, and the laser diode 36A and the photodiode 36B
Are connected to the ground terminal.

The photodiode 36B detects the amount of the laser beam when the laser diode 36A is turned on, and outputs a current corresponding to the amount of the laser beam. The cathode of the photodiode 36B is connected to the input terminal of the differential amplifier 95, and the output terminal of the differential amplifier 95 is connected to the input terminal of the linear amplifier 96.

The differential amplifier 95 is connected to the photodiode 36
The current input from B is converted into a voltage, and the voltage is output to the linear amplifier 96. The linear amplifier 96 amplifies the voltage input from the differential amplifier 95.

The output terminal of the linear amplifier 96 is connected to the FET 87
Is connected to the input terminal of the CPU 84 via the. CPU
By outputting the timing signal to the gate terminal of the FET 84, the output of the linear amplifier 96 can be sampled and held, and the monitor output signal 97 can be captured at an arbitrary timing. For example, the light amount of the laser diode can be monitored and adjusted in synchronization with the beam position detection signal without continuously lighting the laser diode on the photoreceptor 18 including the image area and the non-image area.

Constant current source 91, current switching circuit 9
3. LD including differential amplifier 95 and linear amplifier 96
As the drive circuit 86, a one-chip laser drive IC (general-purpose IC) can be used.

As shown in FIG. 6, the CPU 84
The APC-START signal, P-CONT signal, and PAGE SYNC signal are input.

The APC-START signal is a timing signal,
After the operation of the M / C starts and the scanner motor reaches a steady rotation, the APC-START signal becomes Ready and the light quantity adjustment of the LD 36 is started. Therefore, for safety reasons, the LD 36 is not turned on until the scanner motor reaches steady rotation.

The P-CONT signal is a signal necessary for generating a beam main scanning position detection signal in the laser printer. When the laser beam scans on the photoreceptor 18, the P-CONT signal is output from the end of scanning of each line. This is a signal for turning on the LD 36 until scanning of the next line is started.

That is, the P-CONT signal is for a predetermined period TRUE (low level: see also FIG. 9) for generating the beam main scanning position detection signal, and the LD 36 is lit during this TRUE period. Then, when the beam main scanning position detection signal is not detected within this period, the LD 36 is turned on for a certain period until the beam main scanning position detection signal is detected, and when the beam main scanning position detection signal is not detected within this period. Causes an error in the beam main scanning position detection signal. Therefore, during this period, the LD 36 is continuously lit regardless of the image area and the non-image area. When the beam main scanning position detection signal error occurs, the M / C control circuit 77 turns off the LD 36 and stops the printing operation.

The P-CONT signal becomes FALSE (high level: see also FIG. 9) at a predetermined timing after detecting the beam main scanning position detection signal. Thus, the lighting of the LD 36 for detecting the beam main scanning position detection signal ends.

The light amount control unit 83 detects the light amount of each LD 36 at the same time as the lighting timing and adjusts the light amount for each scanning line.
To prevent the light amount from decreasing. Then, the M / C control circuit 77 synchronizes based on the main scanning position detection signal, and outputs a serial video signal for each color to the LD 36 after a predetermined time.

Note that the TRUE period of the P-CONT signal is a region other than the start end to the end end of the photosensitive drum 18 in one scan line region, and the line scanned by the rotary polygon mirror is shifted from the photosensitive drum region. It is an area (non-image area) that is deviated and scanned.

The PAGE SYNC signal indicates whether or not it is between print papers at the time of printing in the laser printer, and has different timings according to the size of the paper to be printed. This PAGE SYNC
When the signal is TRUE, it means that there is a sheet interval.

Next, the light amount adjustment control will be described as the operation of the present embodiment.

First, when the scanner motor rotates in a steady state and the APC-START signal becomes TRUE, light quantity adjustment is started based on the rising edge of the APC-START signal.

Then, the CPU 84 sets the ports P1, P3,
Data output from P5 and P7 to each D / A converter 85 is initialized.

Next, the CPU 84 sets only the port P1 to the low level so that the drive current flows through the laser diode 36A (hereinafter, this state is referred to as "laser ON", and the state in which the drive current does not flow through the laser diode is referred to as "laser ON"). Laser off).

Then, the value of the D / A converter 85 is increased from the laser ON state, and the drive current of the laser diode 36A is increased. At first, since the drive current of the laser diode 36A is lower than the threshold current value of the laser diode 36A, the laser diode 36A does not emit light even when the laser is on, but when the drive current exceeds the threshold current value, the laser diode 36A Start emitting light.
At this time, the FET 87 is in the ON state, and is ready to monitor the increase or decrease in the amount of light of the laser diode 36A.

The CPU 84 counts up the output data value of the port P1 with respect to the D / A converter 85 until the output value of the monitor output signal 97 output from the linear amplifier 96 reaches a desired value. 86
The input voltage of the constant current source 91 is increased.

This operation will be described with reference to the timing chart shown in FIG. First, among the laser diodes 36A for each of the colors Y, M, C, and K, only the laser diode 36A for K is continuously turned on to start adjusting the light amount.
When the monitor signal-K value shown in FIG. 8B rises and reaches a desired value, the first-stage light amount adjustment ends.

When the light amount adjustment of the K laser diode 36A is completed and the desired light amount value is reached, the beam position of the K laser diode 36A in the main scanning direction is detected as shown in FIG. The beam main scanning position detection signal -K is output, and the K laser diode 36A is turned on only in the non-image area (the period when the P-CONT signal is at a low level) at the timing synchronized with the beam main scanning position detection signal -K. Then, the control of the light amount is started, and the operation for stabilizing the light amount of the K laser diode 36A is always started.

Next, the Y, M, and C laser diodes 36A other than K are turned on at a timing synchronized with the beam main scanning position detection signal -K to adjust the light amount only in the non-image area. When the light amount adjustment is completed, the light amount adjustment of the laser diode 36A becomes Ready, and printing of an image is started.

In the present embodiment, the light amount adjustment of the Y, M, and C laser diodes 36A is performed simultaneously.
In order to reduce the load on U84, the light amount of the laser diode 36A may be adjusted in the order of Y, M, and C. However, in this case, the time required for light amount adjustment becomes long.

The laser diode 36 is actually used in the non-image area.
As shown in FIG. 9, the timing for turning on A is outside the image area (IMAGE AREA) and Y,
This is a range in which beam main scanning position detection signals for detecting the beam positions of the M, C, and K laser diodes 36A in the main scanning direction are output. The light amount adjustment is performed in this range. Although this range is a short period outside the image area, the light amount can be stabilized by repeating the light amount adjustment several times.

Although this is not directly related to the present invention, it is to correct the color misregistration in the main scanning direction when the color image is formed by superimposing the images of the respective colors by using the beam main scanning position detection signals of the respective colors. The laser diode 36A is turned on within the range shown in FIG.

As a result, with respect to the photosensitive members 18 other than K, scanning on the photosensitive member 18 is not required, and
Can be adjusted without deteriorating the light intensity.

[Second Embodiment] Next, a second embodiment of the present invention will be described.

First, when the power is turned on, the K laser diode 36A is first turned on continuously to adjust the light amount, and the light amount is adjusted in the non-image area at a timing synchronized with the beam main scanning position detection signal -K. I do.

Up to this point, it is the same as the first embodiment,
In the second embodiment, the drive current value at the time of starting the light amount adjustment of the Y, M, and C laser diodes 36A is set based on the drive current values of the K laser diode 36A that are first lit continuously and the light amount is adjusted. Then, the light amount control of the Y, M, and C laser diodes 36A is started from the set value. For this reason, the light amount adjustment time for the Y, M, and C laser diodes 36A is shortened, and the time from when the M / C is activated to when the first printout is performed can be shortened.

This will be described with reference to FIG. 10 showing the drive current of the laser diode 36A and the light amount adjustment time.

FIG. 10 shows the relationship between the drive current of the laser diode 36A and the amount of light and the time required for adjusting the amount of light. FIG. 10A shows a case where the reference light source (for example, the K laser diode 36A) is continuously turned on to adjust the light amount. FIG. 10B shows a light source other than the reference light source as described in the first embodiment. When the light amount is adjusted by turning on (for example, the Y, M, and C laser diodes 36A) in the non-image area, FIG. 10C illustrates the case where the driving current value of the reference light source is used as described in the present embodiment. 2 shows a case where the drive current value at the time of starting the light amount adjustment of the light sources other than the reference light source is set and the light amount is adjusted in the non-image area.

The upper part of each figure shows the relationship between the drive current of the laser diode 36A and the amount of light, and the lower part shows the light amount adjustment time required for the laser diode 36A to obtain a desired amount of light. FIG.

Here, the light amount adjustment time is the shortest when the light amount is adjusted by continuous lighting as shown in FIG. 10A. In this case, as described in the prior art, the light amount adjustment time is short. Since the light beam is sometimes irradiated on the photoconductor 18, the photoconductor 18 is deteriorated, and the life is shortened.

Further, as shown in FIG. 10B, when the light amount is adjusted in the non-image area, the light amount adjustment of the parts other than the K laser diode 36A is started from 0 mA, respectively. In some cases, light amount adjustment is performed using the image area, and it takes time to adjust the light amount.

However, as described in the present embodiment, the K laser diode 3 that is first lit continuously and light quantity is adjusted.
6A drive current value, Y, M, C laser diode 3
When the drive current value of each of the 6A is set and the light amount adjustment is started from the set value, it is not necessary to perform the light amount adjustment from 0 mA as shown in FIG. It can be greatly reduced.

Although there are some individual differences in the laser diode 36A, the electrical characteristics are almost the same.
With reference to the drive current of 6 A, a value that does not exceed the target light amount set value (for example, a drive current value that is equal to or more than a predetermined threshold value and equal to or less than the target light amount set value) is set as the current value of the drive current start position. I just need.

Actually, a predetermined value is calculated from the output value of the port P1 of the CPU 84, and the other ports P3, P
5, by outputting from P7, it is possible to start the light amount adjustment start current of the Y, M, and C laser diodes 36A from a predetermined value.

Further, if the laser diode for adjusting the light amount by turning on the light continuously at the beginning such as when the power is turned on is fixed, the photosensitive member 18 corresponding to the laser diode for adjusting the light amount in the non-image area without being turned on continuously is fixed. In comparison, the deterioration of the photoconductor 18 corresponding to the laser diode 36A that continuously lights up and adjusts the light amount is more likely to progress.

Therefore, the laser diode 36A to be continuously turned on first may be determined at random using, for example, a random number. As a result, it is possible to prevent the deterioration of only a specific photoconductor.

The laser diode 36A may be continuously turned on in a predetermined order. That is, the laser diodes 36A are continuously lit in a predetermined order so that the same laser diode 36A is not continuously lit every time. As a result, it is possible to prevent the deterioration of the specific photoconductor 18 from progressing. For this, as shown in the present embodiment, a main scanning position detection sensor 66 for detecting the position of the light beam for scanning on the photoreceptor 18 in the main scanning direction is required for each light beam.

Since the main scanning position detection sensor 66 is provided corresponding to each light beam, the scanning position of the light beam in the main scanning direction can be detected after continuous lighting and light amount adjustment. As shown in FIG. 9, the light amount can be adjusted by turning on the laser diode 36A in the non-image area.

Although not shown, the operation of the laser diode 36A in the non-image area is performed by first detecting a beam main scanning position detection signal and then using a counter or the like.
ON / OFF of the P-CONT signal at such a timing as to light
F to control which laser diode 36
Even if the beam main scanning position detection signal corresponding to A is used, the laser diode 36A can be turned on in the non-image area without any problem.

Further, as shown in FIG. 11, the light quantity control device of the present invention can be applied to an image forming apparatus having one rotary polygon mirror and two laser diodes.

[0102]

As described above, according to the present invention, only the reference light source is continuously lit to adjust the light amount, and the other light sources are lit only in the non-image forming area to adjust the light amount. This has the effect of reducing the irradiation of the photoconductor with the light beam and preventing the photoconductor from deteriorating.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a color image forming apparatus (and a multiple beam scanning apparatus) according to an embodiment.

FIG. 2 is a schematic plan view of a multiple beam scanning device.

FIG. 3 is a perspective view of a multiple-beam scanning device showing a casing lid partially cut away.

FIG. 4 is a schematic plan view showing an arrangement of each sensor on a sensor substrate.

FIG. 5 is a block diagram illustrating a schematic configuration of the image forming apparatus.

FIG. 6 is a circuit diagram illustrating a schematic configuration of an LD light amount adjustment unit.

FIG. 7 is a block diagram illustrating a schematic configuration of an LD circuit board.

FIG. 8 is a timing chart showing the light amount adjustment timing when the power is turned on.

FIG. 9 is a timing chart showing an inter-line light amount adjustment timing.

FIG. 10 is a diagram illustrating a relationship between an LD drive current of an LD light amount adjustment unit and an adjustment time.

FIG. 11 is a schematic configuration diagram illustrating another example of the image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Color image forming apparatus 18 Photoreceptor 30 Multiple beam scanning device 34 Rotating polygon mirror 36 Semiconductor laser 64 Main scanning position detection sensor 66 Sub-scanning position detection sensor 72 Image writing timing generation circuit 77 M / C control circuit 78 Image processing circuit 83 Light intensity Control unit 84 CPU 88 LD drive circuit 91 Constant current source 93 Current switching circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 2C362 AA12 AA16 AA53 AA54 AA56 AA61 CB59 5C051 AA02 CA07 DB30 DE03 DE30 EA01 5C072 AA03 BA20 HA02 HA06 HA13 HB02 HB04 HB08 HB11 HB13 QA14 XA05 5C07A BB A11 DDB

Claims (4)

[Claims] A plurality of light sources; a scanning unit configured to scan light beams emitted from the plurality of light sources on a photosensitive member; and a light beam emitted from a predetermined reference light source among the plurality of light sources, A light beam detecting means for detecting a light beam in a non-image forming area of a main scanning area; a plurality of light amount detecting means for detecting light amounts of light beams emitted from the plurality of light sources; and turning on the plurality of light sources. A plurality of driving current supply means for supplying a driving current for driving the reference light source so that the reference light source is continuously turned on and the light current of the light beam emitted from the reference light source becomes a target light amount. Controlling and turning on light sources other than the reference light source in the non-image forming area in synchronization with the detection timing of the light beam detection means, and emitting light from light sources other than the reference light source. Light quantity control device comprising a control means for the light quantity of the beam respectively control the driving current of the reference light source other than the light source so that the target light amount, the. 2. The light amount according to claim 1, wherein the control unit determines a drive current value to be initially supplied to a light source other than the reference light source based on a drive current value of the reference light source. Control device. 3. The light source control device according to claim 1, wherein the control unit randomly determines the reference light source from the plurality of light sources when the light amount control device starts up or restarts. Light amount control device. 4. The control device according to claim 1, wherein the control unit determines the reference light source from the plurality of light sources in a predetermined order when the light amount control device starts up or restarts. Item 3. A light quantity control device according to Item 2.