JP4419406B2 - Optical scanning device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical scanning device, and more particularly to an optical scanning device using a laser diode having a plurality of light emitting points and capable of outputting a plurality of light beams as a light source.
[0002]
[Prior art]
Conventionally, in an optical scanning device using a light beam of one light source (hereinafter abbreviated as “Single Beam”), scanning is generally performed by deflecting a light beam by a polygon mirror that rotates at high speed by rotational driving of a driving means such as a scanner motor. While irradiating the photosensitive material. In such an optical scanning device, the resolution is switched without degrading the processing capability by switching the rotation speed of the scanner motor in accordance with the resolution. Such a laser diode (hereinafter abbreviated as LD) that outputs a single beam is called a single beam LD.
[0003]
On the other hand, when the speed of the scanner motor is increased, there is a problem of noise and temperature rise, and the recent demand for higher speed and higher resolution cannot be met by the increased speed of the scanner motor. For this reason, a method of irradiating a plurality of light beams simultaneously in one scanning period has been proposed. The LD capable of outputting a plurality of light beams simultaneously includes a plurality of LD chips, and a plurality of light beams (hereinafter abbreviated as “Multi Beam”) can be output by turning on the plurality of LD chips. . An LD capable of lighting a plurality of LD chips is referred to as a multi-beam LD. However, when the resolution is switched using the multi-beam LD, the arrangement interval of the LD chips is constant, so that the desired resolution cannot be obtained only by changing the rotation speed of the scanner motor. In order to solve this problem, it has become necessary to switch the number of light beams to be irradiated to multiple / single.
[0004]
For this reason, in an optical scanning device using a multi-beam LD as a light source, the number of laser emission sources to be used is switched when the scanning density is switched (see Patent Document 1). Thus, by switching a plurality of laser emission sources according to the scanning density, the number of rotations of the polygon mirror can be suppressed to 10,000 rotations or less, for example. Therefore, the cost of the polygon mirror and the scanner motor can be prevented and the size can be reduced.
[0005]
By the way, generally, the required light amount of the photosensitive material per unit time is determined by the product of the process speed and the scan length. Since the scan length is not significantly changed if the photosensitive material is the same, the conventional Single BarmLD does not require a large change in the amount of light if the process speed does not change even if the resolution changes.
[0006]
However, when a multi-beam LD having N LDs is used and the resolution is switched by switching between Multi / Single lighting, the single lighting requires N times as much light as Multi lighting. In a general LD current driving element (hereinafter, abbreviated as LD DRIVER; LDD), a light amount variable range is determined, and there is no light amount variable range corresponding to both Multi / Single lighting. If the amount of light is not a corresponding amount, it is necessary to adjust the irradiation time until the required amount of light is reached, which hinders the speeding up of processing.
[0007]
As a technique for this purpose, conventionally, when switching the scanning density, there is a technique for switching the light amount variable range together with the number of laser sources to be used in synchronization with the scanning density switching signal (see Patent Document 2). Specifically, the light amount variable range is switched by switching the detection sensitivity of the light amount adjusting means for monitoring the output light amount of the LD.
[0008]
[Patent Document 1]
JP-A-1-299042
[Patent Document 2]
JP 10-213771 A
[0009]
[Problems to be solved by the invention]
However, in the conventional technique, it is necessary to provide a switching means for switching the light amount variable range, and there is a problem that the number of lines for supplying a switching signal is increased and the circuit configuration becomes complicated.
[0010]
The present invention has been made to solve the above problems, and an object of the present invention is to provide an optical scanning device capable of changing the light amount variable range of a light source capable of outputting a plurality of light beams with a simple configuration.
[0011]
[Means for Solving the Problems]
  In order to achieve the above object, an optical scanning device according to claim 1 is provided with a plurality of light emitting points and capable of outputting a plurality of light beams, and scanning the light beam output from the laser diodes. Scanning optical system,One light emitting point is provided for each of the plurality of light emitting points.Detecting means for detecting the output light quantity of the light source, and based on the detected light quantity by the detecting meansMultiple light emitting points eachDriving means for controlling the amount of light and lighting the laser diode;When the necessary light amount per light emitting point is less than the controllable light amount lower limit value, any one of the plurality of light emitting points is turned on, and the detected light amount is the first light amount equal to or greater than the lower limit value. After performing the light amount control of the one light emitting point so that the light emitting point is turned on, the light emitting points other than the one light emitting point are turned on in the state where the one light emitting point is turned on with the light amount after the light amount control. The light amount control of the light emitting points other than the one light emitting point is executed so that the detected light amount becomes the second light amount larger than the first light amount, and the light amount after the light amount control of the light emitting points other than the one light emitting point is performed. Control means for controlling the operation of the driving means so as to execute the light amount control of the one light emitting point so that the detected light amount becomes a third light amount equal to or larger than the lower limit value in a state where the light is turned on. I have.
[0012]
  In the above optical scanning device, as described in claim 2, there are a plurality of light emitting points other than the one light emitting point, and the control means emits light points other than the one light emitting point. Are sequentially turned on, and the light amount control of each light emitting point other than the one light emitting point is executed so that the detected light amount becomes the second light amount, and all the light emitting points other than the one light emitting point are respectively set. The one light emitting point is turned on with the light amount after the light amount control being turned on, and the light amount control of the one light emitting point is executed so that the detected light amount becomes a third light amount equal to or greater than the lower limit value. It is characterized by.
[0013]
  In the above optical scanning device, as described in claim 3,A correction unit that corrects the detection sensitivity of the detection unit according to a light emission point that is a light amount control target is further provided, and the control unit sets the correction amount by the correction unitThe light amount control of the light emission point of the light amount control target is executed so that the corresponding light emission amount is obtained.It is characterized by that.
[0014]
  In the above optical scanning device, as described in claim 4, the control unit is required for each light emitting point in accordance with a resolution switching signal indicating resolution switching indicating resolution switching. The amount of light is set.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Next, an example of an embodiment according to the present invention will be described in detail with reference to the drawings.
[0020]
[First embodiment]
FIG. 1 shows an optical scanning device 100 according to a first embodiment of the present invention. The optical scanning device 100 is mounted on an image forming apparatus including a cylindrical photosensitive member 10 that rotates in a direction indicated by an arrow A at a predetermined speed. The optical scanning device 100 scans a light beam in the axial direction of the photosensitive member 10 and moves on the photosensitive member 10. To form an electrostatic latent image. An image forming apparatus equipped with the optical scanning device 100 has a resolution switching function. In the following, an example in which the image resolution can be switched between 600 dpi and 1200 dpi will be described.
[0021]
As shown in FIG. 1, the optical scanning device 100 includes a semiconductor laser 102 as a light source. The semiconductor laser 102 is a so-called multilaser diode having two LD chips LD1 and LD2 (see FIG. 2) as light emitting points (hereinafter, the semiconductor laser is referred to as a multilaser diode). Output is possible. That is, the optical scanning device 100 according to the present embodiment can simultaneously scan two light beams output from the multi-laser diode 102. Note that these two light beams are illustrated in an overlapping manner because they are arranged in the front-rear direction in FIG.
[0022]
Specifically, the LD chips LD1 and LD2 are configured such that when two light beams output from each of the LD chips LD1 and LD2 are scanned onto the photoconductor 10 by a scanning optical system of the optical scanning device 100 described later, The center positions are spaced apart by 21 μm, which is a distance corresponding to an interval of 1200 dpi, so as to be shifted in the sub-scanning direction (direction of arrow A which is the rotation direction of the photoconductor 10) perpendicular to the scanning direction of the light beam. Yes. In other words, the optical scanning device 100 can simultaneously scan the photosensitive member 10 by shifting two light beams by 21 μm in the sub-scanning direction.
[0023]
In addition, the multi-laser diode 102 is provided with a light receiving element PD (see FIG. 2) that detects a part of the light beam output from the multi-laser diode 102 (for example, a light beam output rearward) as detection means. Yes. The light receiving element PD outputs a current proportional to the detected light amount, that is, the output light amount of the multi-laser diode 102 by photoelectric conversion. The output light quantity of the multi-laser diode 102 can be grasped from the output of the light receiving element PD.
[0024]
In addition, the optical scanning device 100 includes the following scanning optical system configured to include a polygon mirror 108 as a deflecting unit. That is, the collimator lens 104 and the cylinder lens 106 are sequentially arranged on the downstream side in the traveling direction of the light beam emitted from the multi-laser diode 102. The collimator lens 104 converts the light beam emitted from the multi-laser diode 102 from a diffused beam to a parallel beam. The light beam converted into parallel rays by the collimator lens 104 is incident on the polygon mirror 108 via the cylinder lens 106.
[0025]
The polygon mirror 108 is formed in a regular polygonal shape (a regular octagon in this embodiment) having a plurality of reflecting surfaces 108A on its side surface, and the light beam is converged on the reflecting surface 108A by the cylinder lens 106. It is designed to be incident. The cylinder lens 106 also has a role of correcting surface tilt of each reflecting surface 108A.
[0026]
The polygon mirror 108 is rotated at a constant speed in the direction of arrow B about the rotation shaft 108B by the rotational drive of the scanner motor 110 (see FIG. 2). By this rotation, the incident angle of the light beam on each reflecting surface 108A is continuously changed and deflected. Accordingly, the photoconductor 10 is irradiated with a light beam by scanning in the axial direction of the photoconductor 10 (arrow C direction).
[0027]
In the traveling direction of the light beam reflected by the polygon mirror 108, an fθ lens 112 composed of a first lens 112A and a second lens 112B is sequentially arranged. The light beam reflected by the polygon mirror 108 passes through the fθ lens 112 and is irradiated onto the photoconductor 10. At this time, the fθ lens 112 makes the scanning speed when irradiating the photoconductor 10 with the light beam uniform, and the imaging point is formed on the peripheral surface of the photoconductor 10. With such a scanning optical system, the optical scanning device 100 can form an image of the light beam emitted from the multi-laser diode 102 on the photosensitive member and scan it at a constant speed.
[0028]
The image forming apparatus on which the optical scanning device 100 is mounted generally includes a charging device, a developing device, a transfer device, a fixing device, and the like together with the photoconductor 10, and the photoconductor 10 that is uniformly charged by the charging device is exposed to light. The scanning device 100 irradiates the light beam while performing main scanning as described above, and performs sub-scanning by rotating the photoconductor 10 in the direction of arrow A to form an electrostatic latent image on the photoconductor 10. Then, the formed electrostatic latent image is developed by a developing device, the developed toner image is transferred to an image recording medium such as paper by a transfer device, subjected to fixing processing by a fixing device, and then removed from the image forming device. Discharge. Thereby, an image recording medium on which an image is recorded can be obtained.
[0029]
Further, in the optical scanning device 100, a mirror 114 is disposed between the fθ lens 112 and the photoconductor 10, at a position corresponding to the head portion of the scanning locus V of the light beam on the photoconductor 10. Further, a light beam position detector 116 for detecting light by a photo detector or the like is disposed as a scanning timing detection means at a position substantially equivalent to the photosensitive member 10 in the reflection direction of the mirror 114. That is, the light beam at the head of the scanning locus among the light beams that scan the photoconductor 10 is reflected by the mirror 114 and guided to the light beam position detector 116. As a result, each time the light beam output from the multi-laser diode 102 scans the photosensitive member 10 in the axial direction, the leading light beam to be irradiated on the photosensitive member 10 is incident on the light beam position detector 116. Will be.
[0030]
The light beam position detector 116 outputs a signal (SOS signal) indicating the scanning start timing for each scanning of the light beam to the photoconductor 10 by the light scanning device 100 by detecting the incident light, and the incident light beam. The amount of light is also detected.
[0031]
Next, the configuration of the electric system for driving the optical scanning device 100 will be described with reference to FIG.
[0032]
As shown in FIG. 2, the multi-laser diode 102 controls the overall operation of the optical scanning device 100 via a drive circuit (hereinafter referred to as LDD) 120 as a drive means for driving (lighting) the multi-laser diode 102. It is connected to a control circuit 122 that functions as a control means of the invention.
[0033]
The control circuit 122 is connected to the image processing device 124 and the resolution changeover switch 126. The image processing device 124 outputs image data to be formed by the image forming device to the control circuit 122. The resolution changeover switch 126 outputs to the control circuit 122 a resolution signal for executing the changeover of the resolution (600 dpi / 1200 dpi) of an image formed by predetermined scanning. The image processing device 124 and the resolution changeover switch 126 are mounted on the image processing device on which the optical scanning device 100 is mounted. When the optical scanning device 100 is mounted on the image forming device, the control circuit 122 and the image processing device 126 are processed. The device 124 and the resolution changeover switch 126 are connected.
[0034]
The control circuit 122 is also connected to the above-described light beam position detector 116 in the optical scanning apparatus 100, and the SOS signal output from the light beam position detector 116 is also input.
[0035]
The control circuit 122 generates various control signals and supplies them to the LDD 120 so that an image based on the image data is formed on the photoconductor 10 according to the image data, the resolution signal, and the SOS signal. The lighting of 102 is controlled. Specifically, the control signals supplied from the control circuit 122 to the LDD 120 include the enable signal ENB, the reference voltage Vref, the light amount control signals Pcont1, Pcont2, and the image signals DATA1, DATA2. These control signals are generally supplied to the LDD 120 in order to control the lighting of the multi-laser diode 102.
[0036]
The numbers (1, 2) at the end of the sign of the light quantity control signals Pcont1 and Pcont2 and the image signals DATA1 and DATA2 represent the corresponding LD chips LD1 and LD2. In the case where there is no particular distinction, the numerals at the end of the reference numerals are omitted.
[0037]
The enable signal ENB is a signal that permits the operation of the LDD 120. In the present embodiment, the operation of the LDD 120 is permitted when it is at the L level, and the operation of the LDD 120 is stopped when it is at the H level.
[0038]
The LDD 120 can drive the LD chips LD1 and LD2 by supplying a drive current to the LD chips LD1 and LD2 of the multi-laser diode 102 only during a period when the operation is permitted by the enable signal ENB. The LD chips LD1 and LD2 emit light with a light amount corresponding to the supplied drive current, and thereby a light beam is output from the multi-laser diode 102. Note that the output light quantity at this time is monitored by the light receiving element PD, and a current corresponding to the output light quantity is input to the LDD 120 from the light receiving element PD.
[0039]
The LDD 120 uses a current corresponding to the output light amount input from the light receiving element PD to control the light amount (output light amount) of the light beam output from each of the light emitting chips LD1 and LD2 of the multi-laser diode 102. A control circuit 130 is provided.
[0040]
Specifically, the light amount control circuit 130 converts the output from the light receiving element PD into a current voltage and amplifies it to generate a monitor voltage. The generated monitor voltage is compared with the reference voltage Vref supplied from the control circuit 122, and the drive current value supplied to the LD chips LD1 and LD2 is adjusted so that the two coincide with each other. Control. Accordingly, the control circuit 122 can change the output light amount by changing the value of the reference voltage Vref as long as it is within the light amount variable range of the LDD 120.
[0041]
The light quantity control signal Pcont is a signal for causing the LDD 120 to start the light quantity control of the LD chips LD1 and LD2 by the light quantity control circuit 130. When the light quantity control signal Pcont1 is at the active level (L level in this embodiment), the LDD 120 turns on the LD chip LD1 to control the light quantity of the LD chip LD1, and the light quantity control signal Pcont2 is at the active level (this embodiment). In the embodiment, the light intensity of the LD chip LD2 is controlled by turning on the LD chip LD2.
[0042]
Here, as shown in FIG. 2, the multi-laser diode 102 generally includes only one light receiving element PD, and the LDD 120 cannot control the light quantity of the LD chip LD1 and the LD chip LD2 simultaneously. For this reason, the control circuit 122 supplies different light quantity control signals Pcont1 and Pcont2 between the LD chip LD1 and the LD chip LD2, and controls the light quantity control timing so that the LD chips LD1 and LD2 are not simultaneously controlled. Yes.
[0043]
The image signal DATA is a signal for turning on and off the LD chips LD1 and LD2 based on the image data input from the image processing device 124. When the image signal DATA1 is at an active level (H level in the present embodiment), the LDD 120 supplies the LD chip LD1 with a drive current having a value adjusted by the light amount control so that the LD chip LD1 has a light amount after the light amount control. Make it emit light. In addition, when the image signal DATA2 is at an active level (H level in the present embodiment), the LDD 120 supplies a drive current having a value adjusted by light amount control to the LD chip LD2, and the LD chip LD2 is subjected to the above light amount control. The light is emitted with the amount of light. The image signals DATA1 and DATA2 are effective when the light quantity control signals Pcont1 and Pcont2 of the corresponding LD chips LD1 and LD2 are at the non-active level (H level in the present embodiment).
[0044]
As shown in FIG. 3A, the control circuit 122 outputs the light amount control signals Pcont1 and Pcont2 and the image signals DATA1 and DATA2 after a predetermined time elapses from the input of the SOS signal. The lighting timing by the signal is shifted. That is, in the control circuit 122, in synchronization with the SOS signal, the light quantity control start timing of the LD chips LD1 and LD2, and the image writing timing to the photoconductor 10 by the output of the light beam based on the image data from the LD chips LD1 and LD2. Is controlling. As a result, the light quantity of the LD chip at the timing when the light beam scans the non-image forming area 202 outside the image forming area 200 in which an image is written on the photoconductor 10 by lighting based on image data within one scanning period of the light beam. Control is performed (see FIG. 3B).
[0045]
Here, in the optical scanning device 100 according to the present embodiment, the resolution signal is input from the resolution changeover switch 126 as described above. When the resolution is changed by a predetermined operation of the resolution changeover switch 126, after the changeover. A resolution signal indicating the resolution is input to the control circuit 122. The control circuit 122 selects either the single mode with one output beam or the multi mode with two output beams according to the resolution indicated by the input resolution signal, and switches the mode. It is like that.
[0046]
When the single mode is selected, the control circuit 122 generates the image signal DATA1 based on the input image data and supplies it to the multi-laser diode 102 in synchronization with the SOS signal. As a result, in the optical scanning device 100, only the LD chip LD1 (or LD chip LD2) of the multi-laser diode 102 is turned on based on the image data, and one output from the LD chip LD1 (or LD chip LD2) is output. The photosensitive member 10 is scanned and exposed by the output beam, and an image is written on the photosensitive member 10 for each scanning line. Thus, the scanning interval when there is one output beam is 42 μm corresponding to 600 dpi.
[0047]
When the Multi mode is selected, the control circuit 122 generates the image signal DATA1 and the image signal DATA2 alternately for each scanning line based on the input image data, and the generated image signal DATA1 and image signal DATA2 are used as the SOS signal. Synchronously supplied to the multi-laser diode 102. Thereby, in the optical scanning device 100, the LD chip LD1 and the LD chip LD2 of the multi-laser diode 102 are turned on based on the image data of the scanning lines adjacent to each other, and the two output from the LD chip LD1 and LD chip LD2 are output. The photosensitive member 10 is scanned and exposed by the output beam, and an image is written on the photosensitive member 10 by two scanning lines for each scan. Thus, the scanning interval when there are two output beams is 21 μm corresponding to 1200 dpi.
[0048]
That is, the resolution of the image written on the photoconductor 10 can be switched by selecting the Single mode when the resolution indicated by the resolution signal is 600 and selecting the Multi mode when the resolution signal is 1200 dpi.
[0049]
Further, as shown in FIG. 2, a scanner motor 110 is also connected to the control circuit 122. The control circuit 122 controls the driving of the scanner motor 110, that is, the rotation of the polygon mirror 108 and the rotation speed thereof.
[0050]
Next, the operation of the present embodiment will be described. First, an outline of the optical scanning device 100 will be described.
[0051]
In the optical scanning device 100, the scanner motor 110 is driven to rotate the polygon mirror 108 at a constant speed at a predetermined speed. When the polygon mirror 108 is rotated at a constant speed, the enable signal ENB is set to L level by the control circuit 122, and the driving of the LDD 120 is permitted. As a result, the multi-laser diode 102 (LD chips LD1, LD2) can be turned on. The multi-laser diode 102 is turned on so that the light beam is incident on the light beam position detector 116. As a result, an SOS signal is obtained for each scan of the light beam.
[0052]
In the optical scanning device 100, in detail, in accordance with the resolution signal from the resolution changeover switch 126, when the resolution signal indicates 600 dpi, the single mode with one output beam is selected and 1200 dpi is indicated. If it is, the Multi mode with two output beams is selected.
[0053]
Then, in the optical scanning device 100, in synchronization with the SOS signal, the single mode is set so that the light amount corresponds to the reference voltage Vref at the timing when the light beam scans the non-image forming region 202 in one scanning period. When selected, the light quantity control signal Pcont1 is set to L level to execute light quantity control of the LD chip LD1, and when the Multi mode is selected, the light quantity control signals Pcont1 and Pcont2 are set to L level to execute light quantity control of the LD chips LD1 and LD2. .
[0054]
However, when the Multi mode is selected, the light quantity control of the LD chips LD1 and LD2 cannot be performed simultaneously because the multi-laser diode 102 has only one light receiving element PD. Therefore, as shown in FIG. 3A, the light quantity control of the LD chips LD1 and LD2 is performed by shifting the timing at which the light quantity control signals Pcont1 and Pcont2 are set to the L level. FIG. 3 shows an example in which the light amount control is performed in the order of the LD chip LD2 and the LD chip LD1. FIG. 3 also uses the light beam output from the lit LD chip LD1 for light quantity control to obtain the SOS signal.
[0055]
Then, after the light amount control is completed, when the single mode is selected, the image signal DATA1 of each scanning line is generated based on the image data input from the image processing device 124, and is output to the LDD 120 in synchronization with the SOS signal. In the LDD 120, the LD chip LD1 of the multi-laser diode 102 is turned on based on the input image signal DATA1. Accordingly, the LD chip LD1 is turned on based on the image data, and one light beam modulated based on the image data is output from the multi-laser diode 102.
[0056]
On the other hand, when the Multi mode is selected, the image signal DATA1 and the image signal DATA2 are alternately generated for each scanning line based on the image data input from the image processing device 124, and output to the LDD 120 in synchronization with the SOS signal. . In the LDD 120, the LD chips LD1 and LD2 of the multi-laser diode 102 are turned on based on the input image signals DATA1 and DATA2, respectively. As a result, the LD chips LD1 and LD2 are turned on based on image data of scanning lines adjacent to each other, and two light beams modulated based on the image data are output from the multi-laser diode 102.
[0057]
The output beam from the multi-laser diode 102 is irradiated while scanning the photoconductor 10 via the scanning optical system of the optical scanning device 100. As a result, the photosensitive member 10 is scanned and exposed by the light beam modulated based on the image data, and the photosensitive member 10 is scanned one scanning line at a time when the single mode is selected and two scanning lines when the multi mode is selected. An image is written (an electrostatic latent image is formed).
[0058]
As described above, the optical scanning device 100 performs lighting based on image data after performing light amount control for each scanning line. As a result, it is possible to scan and expose the photoconductor 10 with a light beam having a stable amount of light and write an image.
[0059]
Here, when the resolution is switched to one (Single) when the resolution is 600 dpi and to two (Multi) when the resolution is 1200 dpi, the required light amount of the photoreceptor and the LDD The relationship of the light quantity variable range is shown in FIG. Note that FIG. 4 shows the required amount of light required by the photoconductor for image formation of 3 to 10 nj / mm.²This is an example of the case.
[0060]
As shown in FIG. 4, when the resolution is switched by switching between single / multi modes, an image is formed with two light beams at 1200 dpi. Therefore, the necessary light amount per light beam, that is, per LD chip. The required light quantity may be ½ of 600 dpi formed by one light beam. Specifically, in the case of 600 dpi, 3 to 10 nj / mm²It is sufficient to set the reference voltage Vref corresponding to the light quantity within the range of the light beam and control the light quantity of the light beam, but in the case of 1200 dpi, it is 1.5 to 5 nj / mm, which is half of that.²It is necessary to set the light quantity of each light beam by setting the reference voltage Vref corresponding to the light quantity within the range of.
[0061]
Here, the light quantity variable range of the LDD 120 is 3 to 10 nj / mm.²If the range (controllable range) of the reference voltage Vref corresponding to this light quantity range is 0.6 to 2.0 V, the reference voltage Vref is less than 0.6 V at 1200 dpi, that is, 3 nj / mm.²If it is less than this, the amount of light cannot be controlled.
[0062]
For reference, in the prior art, when the Multi mode is selected, the sensitivity of the light receiving element PD is increased (for example, doubled) to expand the variable light amount range to the low light amount region side. As a result, as shown in FIG. 10, even if the amount of light is less than 0.6V, the monitor voltage can be made 0.6V or more, and the output amount of light from the LD chips LD1 and LD2 is less than 0.6V. 3nj / mm²The light intensity was controlled to less than FIG. 10 shows a monitor voltage (A) obtained by monitoring the amount of light output from the multi-laser diode 102 by the light receiving element PD, and when the light beam during one scanning period is scanning the non-image forming area. The timing chart (B) of the control signal output from the control circuit 122 is shown.
[0063]
On the other hand, in the optical scanning device of this embodiment, when the resolution is 1200 dpi, that is, when the Multi mode is selected, the light amount control of the multi-laser diode 102 is performed as shown in FIG. FIG. 5 shows a monitor voltage (A) obtained by monitoring the amount of light output from the multi-laser diode 102 by the light receiving element PD, and when the light beam during one scanning period is scanning the non-image forming area. The timing chart (B) of the control signal output from the control circuit 122 is shown. As described above, in the Multi mode, the output light amount from each LD chip needs to be ½ of the necessary light amount required to form an image on the photoconductor 10, and FIG. The lower limit value of the amount of light that can be controlled by the LDD 120 is the required amount of light of the photoconductor 10, and the reference voltage corresponding to the amount of light is Vref0 (= 0.6 V). In the following description, specific reference voltage values are shown in parentheses.
[0064]
That is, as shown in FIG. 5, when the Multi mode is selected, first, the reference voltage Vref is set to Vref0 corresponding to the lower limit value of the amount of light that can be controlled by the LDD 120. That is, Vref = Vref0 (= 0.6V) is set. With the reference voltage Vref set in this way, the light quantity control signal Pcont1 is changed from H level to L level after a predetermined timing has elapsed from the SOS signal (not shown in FIG. 5). Note that the set value of the reference voltage Vref at this time may be a value within 0.6 to 2.0 V corresponding to the light amount range controllable by the LDD 120.
[0065]
Thereby, the lighting of the LD chip LD1 is started from the fall of the light amount control signal Pcont1, the output light amount is monitored by the light receiving element PD, and the monitor voltage substantially coincides with the reference voltage Vref = Vref0 (= 0.6V). As described above, the output light amount of the LD chip LD1 is controlled (this light amount control is referred to as initial light amount control) (period T1). The light amount corresponding to Vref0, which is the control value of this initial light amount control, corresponds to the first light amount of the present invention.
[0066]
After the initial light amount control, the light amount control signal Pcont1 is returned to the H level, and the value of the reference voltage Vref is increased by Vrefα corresponding to 1/2 of the required light amount of the photosensitive member. Specifically, in this example, since the required light amount of the photosensitive member is a light amount corresponding to Vref0, Vrefα = (Vref0) / 2 (= 0.3V), and Vref = Vref0 + Vrefα (= 0.9V) is set. The Note that Vrefα can be set to any value as long as it is ½ or more of the lower limit value of the light quantity controllable by the LDD 120 and less than the lower limit value.
[0067]
After switching the reference voltage Vref in this way, the image signal DATA1 is set to H level and the light quantity control signal Pcont2 is set to L level. As a result, the LD chip LD1 is turned on with the light quantity after the initial light quantity control described above from the rising edge of the image signal DATA1, and the lighting of the LD chip LD2 is started from the falling edge of the light quantity control signal Pcont2, and the monitor voltage is set to the reference voltage. The output light amount of the LD chip LD2 is controlled (this light amount control is referred to as light amount control of the LD chip LD2) so as to substantially match Vref = Vref0 + Vrefα (period T2). Note that a light amount corresponding to Vref0 + Vrefα, which is a control value of the light amount control of the LD chip LD2, corresponds to the second light amount of the present invention.
[0068]
In the light amount control of the LD chip LD2, the output light amount of the LD chip LD1 and the output light amount of the LD chip LD2 are added and monitored by the light receiving element PD, and the light amount after the initial control, that is, Vref0 is equivalent to the LD chip LD1. Since the amount of light emitted from the LD chip LD2 is controlled so that the monitor voltage substantially matches the reference voltage Vref = Vref0 + Vrefα, the amount of light output from the LD chip LD2 corresponds to the amount of light equivalent to Vrefα. Can be adjusted to a light amount corresponding to ½ of the required light amount.
[0069]
In the above-described initial light amount control, the light amount of the LD chip LD1 is controlled with the set value of the reference voltage Vref being Vref0 in order to maximize the controllable light amount range in the light amount control of the LD chip LD2. .
[0070]
After the light amount control of the LD chip LD2, the image signal DATA1 is returned to the L level, the light amount control signal Pcont2 is returned to the H level, and the reference voltage Vref is switched to a voltage value corresponding to the required light amount of the photoconductor 10. In the example of FIG. 5, the lower limit value Vref0 (= 0.6V) of the setting value that can be controlled by the LDD 120 is used as the required light amount of the photoconductor 10, so the value of the reference voltage Vref is returned to Vref0. That is, Vref = Vref0 is set.
[0071]
After switching the reference voltage Vref in this way, the image signal DATA2 is set to H level and the light quantity control signal Pcont1 is set to L level. Thereby, the LD chip LD2 is turned on with the light amount after the light amount control of the LD chip LD2 from the rising edge of the image signal DATA2, and the lighting of the LD chip LD1 is started from the falling edge of the light amount control signal Pcont1. Is controlled so that the output voltage of the LD chip LD1 substantially coincides with the reference voltage Vref = Vref0 (this light amount control is referred to as light amount control of the LD chip LD1) (period T3).
[0072]
The reason why Vref = Vref0 is set when the light amount of the LD chip LD1 is controlled is that the required light amount of the photoreceptor is Vref0, and the light amount corresponding to Vref0 which is the control value of the light amount control of the LD chip LD1 is the present invention. This corresponds to the third light quantity.
[0073]
In this light quantity control of the LD chip LD1, the output light quantity of the LD chip LD1 and the output light quantity of the LD chip LD2 are added together and monitored by the light receiving element PD. From the LD chip LD2, the light quantity after the light quantity control of the LD chip LD2, That is, since a light amount corresponding to Vrefα = (Vref0) / 2 (= 0.3 V) is output, by controlling the light amount of the LD chip LD1 so that the monitor voltage substantially matches the reference voltage Vref = Vref0, The output light amount of the LD chip LD1 can be adjusted to a light amount corresponding to Vref−Vrefα = (Vref0) / 2 (= 0.3V), that is, a light amount corresponding to ½ of the required light amount of the photoconductor.
[0074]
After the light quantity control of the LD chip LD1, the image signal DATA2 is returned to the L level and the light quantity control signal Pcont1 is returned to the H level. Thereafter, although not shown in FIG. 5, when a predetermined timing elapses from the SOS signal, the image signals DATA1 and DATA2 are supplied to the LDD 120, and the LD chips LD1 and LD2 are turned on based on the image signal. As a result, the LD chip LD1 is the light quantity after the light quantity control of the LD chip LD1, and the LD chip LD2 is the light quantity after the light quantity control of the LD chip LD2, that is, both are half the required light quantity of the photoconductor 10 and the image signal. It is turned on based on DATA1 and DATA2.
[0075]
As described above, by controlling the light amount of the multi-laser diode 102 when the Multi mode is selected, the output light amount of the LD chips LD1 and LD2 is desired to be smaller than the lower limit value Vref0 (= 0.6V) of the set value that can be controlled by the LDD 120. (In the above example, it can be controlled to be 1/2 of the required light amount of the photosensitive member 10). In other words, a conventional control signal (reference voltage Vref, light amount) supplied to the LDD 120 in order to control the lighting of the multi-laser diode 102 in the optical scanning device 100, without providing a switching means for switching the light amount variable range in the LDD 120. The light quantity variable range of the LDD 120 can be widened only by controlling the signal values and output timing of the control signals Pcont1, Pcont2, and the image signals DATA1, DATA2).
[0076]
In the above, an optical scanning device that uses a multi-laser diode (so-called Dual LD) having two LD chips as light emitting points as a light source, selects the Multi mode at the time of high resolution, and simultaneously scans with two light beams. Although 100 has been described as an example, the present invention is not limited to the light emitting point and the number of light beams at the time of simultaneous scanning.
[0077]
[Modification]
Next, as a modification of the first embodiment, a multi-laser diode including four LD chips is used as a light source, and at the time of high resolution, the Multi mode is selected and simultaneous scanning with four light beams is performed. Will be described. In the following description, the same members as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted below.
[0078]
In the optical scanning device 100 in this case, as shown in FIG. 6, the multi-laser diode 102 includes four LD chips of LD chips LD1, LD2, LD chip LD3, and LD chip LD4. The difference from the first embodiment is that light amount control signals Pcont1 to Pcont4 for controlling the light amount of the LD chips LD1 to LD4 and image signals DATA1 to DATA4 for lighting based on image data are supplied. The numbers (1-4) at the end of the sign of each signal indicate the corresponding LD.
[0079]
In such an optical scanning device 100, when the Multi mode is selected, light amount control may be performed as shown in FIG. In the Multi mode, it is necessary to control the output light amount of each LD to ¼ the light amount in the Single mode. In the following, the lower limit value of the set value that allows the LDD 120 to control the required light amount of the photoconductor A case where Vref0 (= 0.6 V) is described.
[0080]
As shown in FIG. 7, when the Multi mode is selected, first, the reference voltage Vref is set to the lower limit value Vref0 (= 0.6V) of the set value that can control the amount of light by the LDD 120, and then predetermined from the SOS signal (not shown in FIG. 7). After the timing elapses, the light amount control signal Pcont1 is changed from H level to L level.
[0081]
As a result, the LD chip LD1 is turned on from the fall of the light amount control signal Pcont1, the output light amount is monitored by the light receiving element PD, and the LD chip is set so that the monitor voltage substantially matches the reference voltage Vref, that is, Vref0. The output light amount of the LD 1 is controlled (this light amount control is referred to as initial light amount control) (period T1).
[0082]
After the initial light amount control, the light amount control signal Pcont1 is returned to the H level, and the value of the reference voltage Vref is increased by Vrefβ corresponding to the set light amount of each LD. That is, Vref = Vref0 + Vrefβ is set. When the required light amount of the photosensitive member is set to the lower limit value Vref0 (= 0.6V) of the set value that can be controlled by the LDD 120, in the Multi mode, as described above, each LD has a light amount that is 1/4 of that in the Single mode. Therefore, Vrefβ = (Vref0) / 4 (= 0.15V).
[0083]
After switching the reference voltage Vref in this way, the image signal DATA1 is set to H level and the light quantity control signal Pcont2 is set to L level. As a result, the LD chip LD1 is turned on with the light quantity after the initial light quantity control described above from the rising edge of the image signal DATA1, and the lighting of the LD chip LD2 is started from the falling edge of the light quantity control signal Pcont2, and the monitor voltage is set to the reference voltage. The output light amount of the LD chip LD2 is controlled (this light amount control is referred to as light amount control of the LD chip LD2) so as to substantially match Vref = Vref0 + Vrefβ (period T21).
[0084]
In the light amount control of the LD chip LD2, the output light amount of the LD chip LD1 and the output light amount of the LD chip LD2 are added and monitored by the light receiving element PD, and the light amount after the initial control, that is, Vref0 is equivalent to the LD chip LD1. Since the light amount of the LD chip LD2 is controlled so that the monitor voltage substantially matches the reference voltage Vref = Vref0 + Vrefβ, the output light amount of the LD chip LD2 is equivalent to the light amount corresponding to Vrefβ, that is, the photoconductor. Can be adjusted to a light amount corresponding to ¼ of the required light amount.
[0085]
After the light amount control of the LD chip LD2, the image signal DATA1 is returned to the L level and the light amount control signal Pcont2 is returned to the H level. Further, the value of the reference voltage Vref is not switched, and the value as it is, that is, the setting of Vref = Vref0 + Vrefβ is maintained.
[0086]
Then, the image signal DATA1 is set to the H level, and the light amount control signal Pcont3 is set to the L level. As a result, as in the case of the light quantity control of the LD chip LD2, the LD chip LD1 is lit with the light quantity after the initial light quantity control described above from the rise of the image signal DATA1, and the LD chip from the fall of the light quantity control signal Pcont3. The lighting of the LD3 is started, and the output light amount of the LD chip LD2 is controlled so that the monitor voltage substantially matches the reference voltage Vref = Vref0 + Vrefβ (this light amount control is referred to as light amount control of the LD chip LD3) (period T22). .
[0087]
By the light amount control of the LD chip LD3, the monitor voltage substantially matches the reference voltage Vref = Vref0 + Vrefβ in a state where the light amount after the initial control is output from the LD chip LD1 as in the light amount control of the LD chip LD2. In addition, since the light quantity of the LD chip LD3 is controlled, the output light quantity of the LD chip LD3 can be adjusted to the light quantity corresponding to Vrefβ, that is, the light quantity corresponding to ¼ of the required light quantity of the photoconductor.
[0088]
After the light quantity control of the LD chip LD3, the image signal DATA1 is returned to the L level and the light quantity control signal Pcont3 is returned to the H level. Further, the value of the reference voltage Vref is not switched, and the value as it is, that is, the setting of Vref = Vref0 + Vrefβ is maintained.
[0089]
Then, the image signal DATA1 is set to H level, and the light amount control signal Pcont4 is set to L level. As a result, as in the case of the light quantity control of the LD chip LD2, the LD chip LD1 is similarly turned on with the light quantity after the initial light quantity control from the rise of the image signal DATA1, and the LD chip from the fall of the light quantity control signal Pcont4. The lighting of the LD 4 is started, and the output light amount of the LD chip LD4 is controlled so that the monitor voltage substantially matches the reference voltage Vref = Vref0 + Vrefβ (this light amount control is referred to as LD chip LD4 light amount control) (period T23).
[0090]
With this LD chip LD4 light amount control, the monitor voltage is substantially equal to the reference voltage Vref = Vref0 + Vrefβ in a state where the light amount after the initial control is output from the LD chip LD1 as in the light amount control of the LD chip LD2. Since the light amount of the LD chip LD4 is controlled, the output light amount of the LD chip LD3 can be adjusted to the light amount corresponding to Vrefβ, that is, the light amount corresponding to ¼ of the required light amount of the photoconductor.
[0091]
After the light quantity control of the LD chip LD4, the image signal DATA1 is returned to the L level, the light quantity control signal Pcont4 is returned to the H level, and the value of the reference voltage Vref is switched to Vref0, which is the required light quantity of the photosensitive member. That is, Vref = Vref0 (= 0.6V) is set.
[0092]
Then, the image signals DATA2, DATA3, and DATA4 are set to the H level, and the light amount control signal Pcont1 is set to the L level.
[0093]
As a result, the LD chips LD2, LD3, and LD4 are turned on with the light amounts after the respective light amount controls described above from the rise of the image signals DATA2, DATA3, and DATA4, and the LD chip LD1 is turned on from the fall of the light amount control signal Pcont1. Is started, and the output light amount of the LD chip LD1 is controlled so that the monitor voltage substantially coincides with the reference voltage Vref = Vref0 (this light amount control is referred to as light amount control of the LD chip LD1) (period T3).
[0094]
In this light amount control of the LD chip LD1, the output light amounts of the LD chips LD1 to LD4 are added and monitored by the light receiving element PD, and the light amounts after the respective light amount control from the LD chips LD2, LD3, and LD4, that is, Vrefβ = (Vref0 ) / 4 (= 0.15V) is output, so by controlling the light intensity of the LD chip LD1 so that the monitor voltage substantially matches the reference voltage Vref = Vref0 (= 0.6V). The output light amount of the LD chip LD1 can be adjusted to a light amount corresponding to Vref−3Vrefβ = (Vref0) / 4 (= 0.15V), that is, a light amount corresponding to ¼ of the required light amount of the photoconductor.
[0095]
After the light quantity control of the LD chip LD1, the image signals DATA2, DATA3, and DATA4 are returned to the L level, and the light quantity control signal Pcont1 is returned to the H level. Thereafter, although not shown in FIG. The image signals DATA1 to DATA4 generated based on the above are supplied to the LDD 120, and the LD chips LD1 to LD4 are turned on based on the image signal. As a result, the LD chips LD1 to LD4 are turned on based on the image signals DATA1 to 4 with the respective light amounts after the light amount control, that is, the light amounts that are ¼ of the necessary light amounts of the photoreceptors 10, respectively.
[0096]
By performing the light amount control of the multi-laser diode 102 in this way, the output light amount of the LD chips LD1 to LD4 can be set to a desired light amount smaller than the lower limit value Vref0 (= 0.6V) of the set value that can be controlled by the LDD 120. In the example, it can be controlled to 1/4 of the required light quantity of the photoconductor 10.
[0097]
In the above, as an example, a case where a multi-beam array having four light emission points is used and the number of light beams simultaneously scanned when the Multi mode is selected is four, but the number of light emission points is three, or The same control may be performed when there are five or more. That is, in the case where N light emitting points LD chips LD1 to LDN (N is an integer of 3 or more) are provided and simultaneous scanning is performed with N light beams, the light amount control of the LD chip LD2 described above is equivalent. If the control is repeatedly executed for the LD chips LD3 to LDN and the light quantity control of the LD chip LD1 is performed after the light quantity control of the LD chips LD2 to LDN is completed, the LD chips LD1 to LDN are respectively required for the photoconductor 10. It is possible to control the light amount corresponding to 1 / N of the light amount.
[0098]
That is, regardless of the number of LD chips provided in the multi-laser diode, the LDD 120 can be expanded in the light amount variable range without including a switching means for switching the light amount variable range in the LDD 120.
[0099]
[Second Embodiment]
By the way, in the first embodiment, the case where the light receiving element PD has the same sensitivity to the output beam from any LD chip has been described, but actually, the light receiving sensitivity of the light receiving element PD for each LD chip. There are variations.
[0100]
In the second embodiment, a case will be described in which the variation in the light receiving sensitivity is corrected and the light amount control is performed. In the following, for simplicity of explanation, a case where a multi-laser diode having two LD chips as light emitting points (so-called Dual LD) is used as a light source will be described as an example, but the number of light emitting points is 2 Any number may be used as long as there are two or more.
[0101]
As shown in FIG. 8, the optical scanning device 100 according to the second embodiment corrects the light receiving sensitivity of the light receiving element PD in accordance with the LD chip that is a light amount control target in the light amount control circuit 130 as a correction unit. A sensitivity correction circuit 132 is provided, and the reference voltage Vref output from the control circuit 122 is also corrected in accordance with the sensitivity correction by the sensitivity correction circuit 132, which is different from the first embodiment. Note that the correction amount of the reference voltage Vref is stored in advance in the control circuit 122 although illustration is omitted.
[0102]
The sensitivity correction method of the light receiving element PD by the sensitivity correction circuit 132 is not particularly limited, and when a light beam having the same light amount is incident on the light receiving element PD, the light amount that appears as the monitor voltage is the light beam of the light beam. It is only necessary to be able to adjust so as to be substantially the same regardless of the LD chip of the emission source. For example, as described above, the light amount control circuit 130 converts the output current from the light receiving element PD into a current voltage and amplifies it to generate a monitor voltage, so that the sensitivity of the light receiving element PD can be changed by changing the amplification factor at this time. It is conceivable to correct this. Further, for example, the sensitivity can be corrected by inserting / removing filters having different transmittances on the light receiving surface side of the light receiving element PD.
[0103]
Further, the LD chip subject to light quantity control can be determined by the light quantity control signal set to the active level among the light quantity control signals Pcont 1 and Pcont 2.
[0104]
In the second embodiment, when the Multi mode is selected, the light amount control may be performed as shown in FIG. In FIG. 9, the light receiving element PD has higher sensitivity to the light beam output from the LD chip LD2 than the light beam output from the LD chip LD1 (the sensitivity of the light receiving element PD is LD1 <LD2). An example of the case is shown. In this case, in the sensitivity correction circuit 132, when controlling the output light amount of the LD chip LD2, the sensitivity of the light receiving element PD is switched to be lower than when controlling the output light amount of the LD chip LD1. In the following, a case where the required light amount of the photosensitive member is set to the lower limit value Vref0 (= 0.6 V) of the set value that can be controlled by the LDD 120 will be described as an example.
[0105]
That is, as shown in FIG. 9, when the Multi mode is selected, first, as in the first embodiment, the light amount control signal Pcont1 is set to the H level with the reference voltage Vref = Vref0 (= 0.6V). To L level to control the initial light quantity of the LD chip LD1 (period T1).
[0106]
After the initial light quantity control, the light quantity control signal Pcont1 is returned to the H level, the value of the reference voltage Vref is switched, the image signal DATA1 is set to the H level, the light quantity control signal Pcont2 is set to the L level, and the LD chip LD1 is set. The light quantity control of the LD chip LD2 is performed while lighting with the light quantity after the initial light quantity control (period T2).
[0107]
At this time, since the sensitivity of the light receiving element PD is switched to a low level for the LD chip LD2 by the sensitivity correction circuit 132, even if the LD chip LD1 is turned on with the light amount after the initial light amount control, the LD chip included in the monitor voltage The output light quantity component of LD1 becomes low (see FIG. 9A). If the ratio of the sensitivity for the LD chip LD1 and the sensitivity for the LD chip LD2 is γ: 1 (γ> 1), the output light quantity component of the LD chip LD1 included in the monitor voltage is reduced by Vref0− (Vref0) / γ. .
[0108]
For this reason, when controlling the light quantity of the LD chip LD2, in the first embodiment, the reference voltage Vref is increased by Vrefα corresponding to ½ of the required light quantity of the photosensitive member. In the second embodiment, Furthermore, it is necessary to correct the reference voltage Vref by the amount of decrease in the output light amount component of the LD chip LD1 included in the monitor voltage due to the sensitivity switching of the light receiving element PD. That is, Vref = Vref0 + Vrefα− {Vref0− (Vref0) / γ} = Vrefα + (Vref0) / γ = (Vref0) / 2 + (Vref0) / γ, and the value of the reference voltage Vref, and then the light quantity of the LD chip LD2. Control is performed.
[0109]
In this way, by controlling the light amount of the LD chip LD2 in a state where the reference voltage Vref value is corrected in accordance with the sensitivity switching of the light receiving element PD from the LD chip LD1 to the LD chip LD2, the LD chip LD is accurately obtained. The light quantity control of the LD 2 can be performed. Thereby, the output light amount of the LD chip LD2 is controlled to a light amount corresponding to Vrefα, that is, a light amount corresponding to ½ of the required light amount of the photoconductor.
[0110]
After the light quantity control of the LD chip LD2, the light quantity control signal Pcont2 is returned to the H level, the value of the reference voltage Vref is switched, the image signal DATA2 is set to the H level, and the light quantity control signal Pcont1 is set to the L level. The light quantity control of the LD chip LD1 is performed while the chip LD2 is lit with the light quantity after the light quantity control (period T3).
[0111]
At this time, since the sensitivity of the light receiving element PD is switched high for the LD chip LD2 by the sensitivity correction circuit 132, even if the LD chip LD2 is lit with the light amount after the light amount control, the LD chip LD2 included in the monitor voltage. The output light quantity component becomes higher (see FIG. 9A). Specifically, the output light amount component of the LD chip LD2 included in the monitor voltage is increased by γ × Vrefα−Vrefα.
[0112]
For this reason, at the time of controlling the light amount of the LD chip LD1, in the first embodiment, the reference voltage Vref is set to Vref0 corresponding to the required light amount of the photoreceptor, but in the second embodiment, the sensitivity of the light receiving element PD is further increased. It is necessary to correct the reference voltage Vref by the increase in the output light amount component of the LD chip LD2 due to the switching. That is, after the value of the reference voltage Vref is switched to Vref = Vref0 + (γ × Vrefα−Vrefα) = (Vref0) / 2 + γ × (Vref0) / 2, the light amount control of the LD chip LD1 is performed.
[0113]
As described above, the light quantity of the LD chip LD1 is controlled in a state where the reference voltage Vref value is corrected in accordance with the sensitivity switching from the LD chip LD2 to the LD chip LD1 of the light receiving element PD. The light quantity control of the LD 1 can be performed. Accordingly, the output light amount of the LD chip LD1 is controlled to a light amount corresponding to Vref0−Vrefα = Vrefα, that is, a light amount corresponding to ½ of the required light amount of the photoconductor.
[0114]
By performing the light quantity control of the multi-laser diode 102 in this way, there is a variation in the light receiving sensitivity of the light receiving element PD for each LD chip, and even when the light receiving sensitivity of the light receiving element PD is corrected according to the LD chip that is the light quantity control target. The output light amount of each LD chip is accurately set to a desired light amount (1/2 of the required light amount of the photoconductor 10 in the above example) smaller than the lower limit value Vref0 (= 0.6 V) of the set value that can be controlled by the LDD 120. Can be controlled.
[0115]
【The invention's effect】
As described above, the present invention has an excellent effect that the light amount variable range can be changed with a simple configuration in an optical scanning device using a light source capable of outputting a plurality of light beams.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an optical scanning device according to a first embodiment.
FIG. 2 is a block diagram showing a configuration of an electric system of the optical scanning device according to the first embodiment.
FIG. 3 is a timing chart (A) showing various control signals output from the control circuit and changes in the output light quantity of the LD chip, and a diagram (B) showing the relationship between the output timing of the control signals and the scanning position of the light beam. .
FIG. 4 is a graph for explaining a necessary light amount range for forming an image on a photoconductor.
FIG. 5 is a graph (A) showing a monitor light amount obtained by light amount control when a Multi mode is selected according to the first embodiment, and a timing chart (B) of a control signal.
FIG. 6 is a block diagram showing a configuration of an electric system of an optical scanning device according to a modification of the first embodiment.
7 is a graph (A) showing a monitor light quantity obtained by light quantity control when the Multi mode is selected in the optical scanning device of FIG. 6, and a timing chart (B) of control signals.
FIG. 8 is a block diagram showing a configuration of an electrical system of an optical scanning device according to a second embodiment.
FIG. 9 is a graph (A) showing a monitor light amount obtained by light amount control when the Multi mode is selected according to the second embodiment, and a timing chart (B) of a control signal.
FIG. 10 is a graph (A) showing a monitor light amount obtained by light amount control when a conventional Multi mode is selected, and a control signal timing chart (B).
[Explanation of symbols]
100 Optical scanning device
102 Semiconductor laser (multi laser diode)
108 polygon mirror
110 Scanner motor
116 Light beam position detector
122 Control circuit
124 Image processing apparatus
126 Resolution changeover switch
130 Light control circuit
132 Sensitivity correction circuit
LD1-4 LD chip
PD photo detector
DATA1-4 Image signal
Pcont1-4 Light quantity control signal
Vref reference voltage

Claims (4)

A laser diode having a plurality of light emitting points and capable of outputting a plurality of light beams;
A scanning optical system for scanning the light beam output from the laser diode;
One detecting means provided for the plurality of light emitting points to detect the output light quantity of the plurality of light emitting points ;
Drive means for controlling the light quantity of each of the plurality of light emitting points based on the light quantity detected by the detection means and driving the laser diode to light;
When the necessary light amount per light emitting point is less than the controllable light amount lower limit value, any one of the plurality of light emitting points is turned on, and the detected light amount is the first light amount equal to or greater than the lower limit value. After performing the light amount control of the one light emitting point so that the light emitting point is turned on, the light emitting points other than the one light emitting point are turned on in the state where the one light emitting point is turned on with the light amount after the light amount control. The light amount control of the light emitting points other than the one light emitting point is executed so that the detected light amount becomes the second light amount larger than the first light amount, and the light amount after the light amount control of the light emitting points other than the one light emitting point is performed. A control means for controlling the operation of the driving means so as to execute the light quantity control of the one light emitting point so that the detected light quantity becomes a third light quantity equal to or greater than the lower limit value in a state where the light is turned on .
An optical scanning device comprising: There are a plurality of light emitting points other than the one light emitting point,
  The control means sequentially turns on and turns on light emitting points other than the one light emitting point, and executes light amount control of each light emitting point other than the one light emitting point so that the detected light amount becomes the second light amount. Then, in a state where all the light emitting points other than the one light emitting point are turned on with the light amount after the light amount control, the one light emitting point is turned on, and the detected light amount becomes the third light amount equal to or greater than the lower limit value. The light scanning device according to claim 1, wherein the light amount control of the one light emitting point is executed as described above. According to the light emission point of the light quantity control target, further comprising a correction means for correcting the detection sensitivity of the detection means,
3. The optical scanning device according to claim 1, wherein the control unit performs light amount control of a light emission point of the light amount control target so that a light emission amount according to a correction amount by the correction unit.   The said control means sets the required light quantity per said light emitting point according to the resolution switching signal which shows the resolution switching which shows the switching of resolution, The any one of Claim 1 thru | or 3 characterized by the above-mentioned. Optical scanning device.

Images