JPH11170602A - Optical write apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a wait time for switching of a pixel density and enable high-speed writing of image data. SOLUTION: In an optical write apparatus in which light beams emitted from a light source 10 are scanned on a photosensitive body 26 in a manner to vary a pixel density in accordance with a pixel density indication signal from outside, thereby forming images, the apparatus includes a first light beam deflection means 16 deflecting the light beams in a main scan direction on the photosensitive body, a second light beam deflection means 14 deflecting light beams which is set in an optical path from the light source to the photosensitive body, and a control means 30 controlling driving of the second light beam deflection means so that a scan line position of light beams can be changed for every line in a sub scan direction in accordance with a designated pixel density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image by scanning a light beam emitted from a light source on a photoreceptor so as to change the pixel density in accordance with an externally specified pixel density signal. The present invention relates to an optical writing device used in a computer.

[0002]

2. Description of the Related Art Conventionally, in an optical writing device used in an image forming apparatus such as a laser printer, a copying machine, a facsimile machine, etc., since the pixel density is fixed at a constant value, images of various pixel densities are formed. There was a problem that you can not. In order to solve this problem,
Japanese Patent Application No. 114371 proposes a technique for switching the pixel density by providing a pixel density switching means for switching the pixel density according to a pixel density command from the outside. This pixel density switching is performed by the configuration shown in FIG. As shown in FIG. 1, the optical writing apparatus irradiates a laser beam emitted from a light emitting device 100 composed of a semiconductor laser such as a laser diode and a monitor sensor to a rotary polygon mirror 104 via a diaphragm 102, and Polygon mirror 10
The laser beam is turned into a writing beam by the rotation of the laser beam 4, and the writing beam is incident on the photosensitive member 108 as a writing surface via the Fθ lens 106, thereby forming an electrostatic latent image corresponding to the written image on the photosensitive member 108. Form. The aperture device 102 is driven by an aperture motor 130 via a driver 128 under the control of an aperture diameter control circuit 126, and its aperture diameter is controlled.

A write control circuit 110 outputs a video signal VIDEO to a modulation circuit 118 in response to write data WDATA or the like sent from a host, and performs synchronization as a write start position in the main scanning direction for write control. A pixel synchronization clock WCLK, a line gate signal LGATE indicating an effective image area in the main scanning direction, and a frame gate signal FGA indicating an effective image area in the sub-scanning direction based on a detection signal from a synchronization detection sensor for detecting a position.
TE, line synchronization signal L as write start synchronization signal
SYNC, an erase signal ERASE as a laser light setting signal outside the writing area, etc. are generated and output, and the frequency of the pixel synchronization clock WCLOK and the line gate signal LGATE corresponding to the pixel density commanded by the image density command signal from the host. It controls the number of pixels and the number of pixels of the frame gate signal FGATE, and further outputs frequency division ratio information D11 as aperture control data, frequency division ratio information D12 as light output data, and a reference clock REFM. The write control circuit 110 has a crystal oscillator 112 for generating a reference clock having a frequency Fxt.

The light power control circuit 114 detects frequency division ratio information from the write control circuit 110, a pixel density command signal from the host, and detection from a monitor sensor such as a photodiode provided inside the light emitting device 100 and receiving a laser beam. An optical output signal is provided to the modulation circuit 118 via the driver 116 according to the signal. The modulation circuit 118 supplies a current corresponding to the optical output signal from the optical power control circuit 114 to the semiconductor laser of the light emitting device 100 and the write control circuit 11
The semiconductor laser of the light emitting device 100 is turned on / off in accordance with the video signal VIDEO from 0, and the light emitting device 100 emits a laser beam corresponding to the written image.

[0005] A PLL control circuit 120 receives a reference clock REFM from the write control circuit 110, a pixel density command from the host, and a feedback signal from a polygon motor 124 for driving the rotating polygon mirror 104 via a driver 122. The pixel density is switched by driving and controlling the polygon motor 124 to rotate the rotary polygon mirror 104.

[0006]

However, in the above-described conventional pixel density switching method, a control circuit for controlling the rotation of the rotary polygon mirror in order to variably control the rotation speed of the rotary polygon mirror for each pixel density is provided. There is a problem that it becomes complicated and expensive.

Further, since it is necessary to switch the rotation speed of the rotary polygon mirror for each set pixel density, it is necessary to have a time period from the start of switching the pixel density to the stabilization of the rotation speed of the rotary polygon mirror. Become. Therefore, it is good to print with the same pixel density.However, in the case of a multifunction machine in which a laser printer and a facsimile are integrated, the pixel density to be printed is different. Then, there is a problem that the printing time is noticeably delayed.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and when image data is written at different pixel densities, the image data can be written at high speed without the need for a waiting time for switching pixel densities. It is an object of the present invention to provide an optical writing device capable of performing the following.

[0009]

In order to achieve the above object, according to the first aspect of the present invention, a light beam emitted from a light source is changed in pixel density according to a pixel density designation signal from the outside. A light beam deflecting unit for deflecting the light beam in a main scanning direction on the photosensitive member, and an optical path from the light source to the photosensitive member. A second light beam deflecting means provided inside the light source for deflecting the light beam in the sub-scanning direction, and setting the scanning line position of the light beam to 1 according to the pixel density specified by the pixel density specifying signal for specifying the pixel density. And control means for driving and controlling the light beam deflecting means so as to be changeable in the sub-scanning direction for each line.

In the optical writing apparatus having the above-mentioned structure, the control means can change the scanning line position of the light beam in the sub-scanning direction line by line in accordance with the pixel density specified by the pixel density specifying signal for specifying the pixel density. A second light beam deflecting means provided in an optical path from the light source to the photoreceptor, and drives the second light beam deflecting means in the sub-scanning direction based on a control signal from the control means. To deflect.

According to the first aspect of the present invention, when the pixel density is switched, the light beam is scanned in accordance with the pixel density without changing the rotation speed of the rotary polygon mirror for scanning the light beam on the photosensitive member. Is controlled so that the scanning line position can be changed in the sub-scanning direction for each line, so that when writing image data with different pixel densities, time for switching pixel densities is not required, and image data can be written at high speed. Can be written to.

According to a second aspect of the present invention, in the optical writing apparatus according to the first aspect, the range in which the pixel density can be switched is equal to or less than the maximum pixel density of the optical writing apparatus.

According to a third aspect of the present invention, in the optical writing apparatus according to the second aspect, when the relationship of pixel density × 2 ≦ maximum pixel density is satisfied, the interval between write positions of overwritten data is set in the sub-scanning direction. And the same write data is overwritten twice.

According to the third aspect of the invention, the interval between the writing positions of the image data to be overwritten is narrowed in the sub-scanning direction to perform the writing, so that the effect obtained by the first aspect of the invention is obtained. In addition, the edge portion of the line to be scanned can be made smoother than the usual overwriting of image data.

[0015]

Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration of the optical writing device according to the first embodiment of the present invention. In FIG. 1, the optical writing device is configured to include a laser diode, a monitoring photodiode, and the like.
4 is provided. The collimator lens 1 is located on the side of the light source 10 where the laser beam 24 is emitted.
2. An electro-optic deflector utilizing the electro-optic effect (hereinafter referred to as E
Recorded as OD. And 14, a polygon mirror (rotating polygon mirror) 16 as a first light beam deflecting means of the present invention is arranged in order. The EOD 14 corresponds to a second light beam deflecting unit of the present invention.

The rotation axis of the polygon mirror 16 is connected to the rotation axis of a polygon mirror motor 28, and the polygon mirror motor 28 is connected to a main controller 30 for controlling the operation of the entire optical writing device. The polygon mirror motor 28 rotates the polygon mirror 16 according to a motor drive signal input from the main control unit 30. With the rotation of the polygon mirror 16, the laser beam 24 incident on the polygon mirror 16 is deflected along a predetermined direction (main scanning direction). In FIG. 1, the laser beam 24 emitted from the light source 10 is drawn as a straight line up to a plane mirror 20, which will be described later. However, in actuality, the laser beam 24 is reflected in a predetermined direction by the polygon mirror 16 as described above. The body 26 is scanned in the main scanning direction.

The main control unit 30 includes a microcomputer 40 (see FIG. 2) and the like, and the main control unit 30 corresponds to the control means of the present invention.

On the other hand, the EOD 14 is constituted by forming an opposing electrode (or a comb-shaped electrode) on an optical member composed of an electro-optical member represented by LiTaO ₃ or the like.
Is arranged so that the laser beam 24 emitted from the optical member enters the optical member. When a voltage is not applied to the electrode, the EOD 14 transmits the laser beam 24 incident on the optical member as it is, but when a voltage is applied to the electrode, the EOD 14 converts the incident laser beam 24 by an electro-optic effect. The photosensitive member 26 is deflected in the sub-scanning direction by a deflection amount corresponding to the magnitude of the voltage applied to the electrode, and is emitted.

The electrodes of the EOD 14 are connected to the main control unit 30, and a beam position control signal described later is input from the main control unit 30. A voltage corresponding to the input beam position control signal is applied to the electrodes of the EOD 14, and the amount of deflection of the laser beam 24 input to the optical member is controlled by the main control unit 30.

In this embodiment, when a voltage corresponding to the beam position control signal is not applied to the electrode of the EOD 14, the laser beam 24 is in the direction of the solid line in FIG. 1 (normal direction). When a voltage (positive polarity voltage) according to the beam position control signal is applied to the electrode of the EOD 14, the laser beam 24 according to the value of the applied voltage.
Are deflected in the sub-scanning direction indicated by the broken line. When a voltage having a negative polarity is applied to the electrode of the EOD 14, the laser beam 24 is applied in the opposite direction to the case where a voltage having a positive polarity is applied.
Is deflected.

In this embodiment, when the beam position control signal is at a low level (0 V), no voltage is applied to the electrodes of the EOD 14, and when the beam position control signal is output, the EOD 14 is output in accordance with the output signal. A voltage is applied to the electrodes of FIG.

On the reflection side of the laser beam 24 on the polygon mirror 16, an Fθ lens 18 and a plane mirror 20
Are arranged in order. Further, a cylinder mirror 22 is disposed on the plane mirror 20 on the reflection side of the laser beam 24, and a photosensitive member 26 is disposed on the cylinder mirror 22 on the reflection side of the laser beam 24.

The laser beam 24 deflected by the polygon mirror 16 is transmitted through the Fθ lens 18, reflected by the plane mirror 20 and the cylinder mirror 22, and scans the photosensitive member 26.

The main controller 30 is further connected to a synchronization detector 32 composed of an optical sensor or the like.
The main control unit 30 outputs a horizontal synchronization signal to the main control unit 30 by detecting the scanning start position of the laser beam 24 that scans upward. In the present embodiment, the horizontal synchronization signal is at a high level when the laser beam 24 is not incident on the synchronization detector 32, and is at a low level when the laser beam 24 is incident.

Further, the light source 10 is connected to the main control unit 30, and the main control unit 30 controls the emission of the laser beam 24 from the light source 10.

FIG. 2 shows a configuration of a light quantity control circuit 50 for controlling the light quantity of the laser diode 10A included in the main control section 30.

An input terminal of a digital / analog converter (hereinafter, referred to as DAC) 52 of the light amount control circuit 50 is connected to an output terminal of the microcomputer 40.
The DAC 52 converts a digital signal input from the microcomputer 40 into an analog signal. DAC52
Is connected to a constant current source 54 to which a power supply voltage Vcc is applied. The constant current source 54 sets and outputs a current value flowing through a laser diode 10A, which will be described later, based on the analog signal input from the DAC 52.

The output terminal of the constant current source 54 is connected to the image forming signal 7.
0 is connected to the current switching circuit 60 input from the microcomputer 40 and the current switching circuit 6
0 is connected to the laser diode 10 in the light source 10.
A is connected to the anode terminal. The current switching circuit 60 supplies the current input from the constant current source 54 to the laser diode 10A based on the image forming signal 70. The image forming signal 70 is a signal generated by the microcomputer 40 based on the image data of the image to be formed.
Is turned on, a laser beam 24 for forming an image on the photoconductor 26 can be obtained. In the present embodiment, the laser diode 10A is turned on when the image forming signal 70 is at a low level, and is turned off when the image forming signal 70 is at a high level.

The cathode terminal of the laser diode 10A is connected to the anode terminal of the photodiode 10B inside the light source 10, and the laser diode 10A
A connection line between the photodiode and the photodiode 10B is connected to a ground terminal. The photodiode 10B detects the amount of the laser beam when the laser diode 10A is turned on, and outputs a current corresponding to the amount of the laser beam.

The cathode of the photodiode 10B is connected to the input terminal of the differential amplifier 58, and the output terminal of the differential amplifier 58 is connected to the input terminal of the linear amplifier 56. The differential amplifier 58 allows the photodiode 10B
Is converted into a voltage, and the voltage is amplified by the linear amplifier 56.

The output terminal of the linear amplifier 56 is connected to the input terminal of the microcomputer 40. The constant current source 54, the current switching circuit 60, the differential amplifier 58, and the part 80 of the linear amplifier 56 may be a one-chip laser drive IC (general-purpose IC).

Next, the operation of the optical writing device according to the first embodiment when switching the pixel density will be described with reference to FIGS. FIG. 3A shows that the pixel density is 600 s.
FIG. 3B shows the trajectory of a scanning line for each line when printing is performed as pi (spot / inch).
Indicates the trajectory of the scanning line for each line when printing at a pixel density of 480 spi, in comparison with the trajectory of the scanning line when the pixel density is 600 spi. FIG. 3 (A)
Indicates a state in which image data D1 to D5 are written by scanning lines L1 to L5 at a pixel density of 600 spi.

On the other hand, since the rotating polygon mirror 16 and the photosensitive member 26 are rotating at the same speed as in the case where the pixel density is 600 spi, the position of the laser beam 24 for scanning the photosensitive member 26 in the sub-scanning direction must be changed. If the pixel density is 600
spi, but with a pixel density of 600 spi,
In order to print at a pixel density of 80 spi, 600 s
It is possible to perform printing using only four lines out of five lines printed with pi. That is, according to the present embodiment, as shown in FIG.
480sp when printing at the pixel density of
The first line scanning at the pixel density of i is 600 sp.
The image data D1 is written at the same scanning line position (on the scanning line L1 ') as the first scanning line L1 of i, and 480 spi
The scanning of the second line when scanning at a pixel density of
1/3 of the second scanning line L2 at 00 spi
The image data D2 is written by scanning over the scanning line L2 'whose scanning line position is shifted to the lower side of the line.

Next, when scanning at a pixel density of 480 spi, 3
In the scanning of the line, the image data D3 is written by scanning on a scanning line L3 ′ whose scanning line position is shifted downward by ／ line from the scanning line L3 of the third line when the pixel density is 600 spi.

Further, when scanning at a pixel density of 480 spi,
The scanning of the line is performed without writing image data to the fourth scanning line L4 (scanning line L4 ′) when the pixel density is 600 spi, and the scanning at the pixel density of 480 spi is performed.
The scanning of the line scans the fifth scanning line L5 (scanning line L5 ′) when the pixel density is 600 spi, and writes the image data D4. By repeating the writing operation for the scanning lines L1 'to L5' in this manner, it is possible to switch the pixel density in the sub-scanning direction.

The pixel density in the main scanning direction can be dealt with by changing the lighting time of the laser diode 10A, so that the description will not be made particularly in this embodiment.

Next, a specific operation when switching the pixel density shown in FIG. 3 in the optical writing device according to the first embodiment will be described with reference to FIG. In the figure, when scanning is performed at a pixel density of 600 spi, a horizontal synchronization signal HSYNC output from the synchronization detector 32 to the main control unit 30 is used.
Output image data D1, D2,.
Printing is performed for each scanning line at a scanning line interval set according to 0 spi (FIGS. 5A and 5B). At this time, since the position of each scanning line does not need to be changed,
The beam position control signal BP output to the OD 14 remains at the low level (0 V) (FIG. 5C).

On the other hand, when the pixel density is switched from 600 spi to 480 spi, as described above, the image data D1 to D3 are output from the first line to the third line in synchronization with the horizontal synchronizing signal HSYNC.
The output of the image data is controlled so that the image data D4 is output on the fifth line without outputting the image data on the fourth line, and the pixel density is changed to 480 spi because the interval between the scanning lines remains at 600 spi. Figure 3
(B) Beams of levels V1 and V2 (V2 = V1) necessary to move the second scanning line to 1/3 line and the third scanning line to 2/3 line on the lower side. The main control unit 30 synchronizes the position control signal BP with the horizontal synchronization signal HSYNC output from the synchronization detector to output the EOD14 from the main control unit 30.
The scanning line position of the laser beam 24 is changed in the sub-scanning direction according to the signal level of the beam position control signal BP.

As described above, by controlling the amount of movement of the laser beam 24 in the sub-scanning direction for each scanning line, the rotation speed of the polygon mirror 16 is not changed when the pixel density is set to 600 spi. The pixel density can be switched to 480 spi.

In addition, if the scanning line position of the light beam is controlled in the sub-scanning direction with the pixel density set to 600 spi as shown in FIG.
i, 400 spi, and 480 spi. In the figure, for example, when the pixel density is 300 spi, “1 out of two lines of 600 spi”
“Line” means that image data is written using one of two adjacent scanning lines when the pixel density is 600 spi. The pixel density is 300 sp
In the case of i, the remark "600 spi overwriting" means that the same image data with a pixel density of 600 spi is overwritten twice to obtain a pixel density of 300 spi.

In the first embodiment, since the maximum pixel density is set to 600 spi, only the switching of the pixel density of 600 spi or less is described. However, if the maximum pixel density is set to 1200 spi, the pixel density (integer) is changed. It is possible to switch to a pixel density of 1200 spi or less within the range of ≦ maximum pixel density.

As described above, according to the optical writing apparatus according to the first embodiment of the present invention, the number of rotations of the rotary polygon mirror for scanning the photosensitive member with a light beam when switching the pixel density. Is controlled so that the scanning line position of the light beam can be changed in the sub-scanning direction line by line in accordance with the pixel density without changing the laser beam density, so that a laser printer and a facsimile apparatus are integrated. In the case where it is necessary to write image data with different pixel densities, the waiting time for switching pixel densities becomes unnecessary,
It is possible to print image data at high speed.

Next, an optical writing device according to a second embodiment of the present invention will be described with reference to FIGS.
The configuration of the optical writing device according to the second embodiment is basically the same as that of the optical writing device according to the first embodiment.

In this embodiment, the pixel density (integer) × 2 ≦
When the relationship of the maximum pixel density is satisfied, the interval of data to be overwritten is narrowed in the sub-scanning direction so that the same write data is overwritten twice.

When the pixel density after the switching falls within the range of pixel density × 2 ≦ large pixel density, for example, when the pixel density is switched from 600 spi to 300 spi, the pixel density in the first embodiment is At 600 spi, image data is output and printed every other scanning line during scanning.

In the present embodiment, the same image data is repeatedly output twice as shown in FIG.
As shown in (A), for example, the scanning line L1 (300s
pi of the scanning line L1 '. In ()), the image data D1 is written by scanning without changing the scanning line position, and then the scanning line position is moved upward on the (1/3) P diagram with the scanning line interval being P with respect to the scanning line L2. Scan line position (300 s)
pi of the scanning line L2 '. ), The image data D1 is scanned and printed so as to be overwritten. Scan lines L3, L
The same applies to No. 4.

As described above, by writing the image data by moving the laser beam 24 to about 1 / 3P to the side opposite to the first embodiment, the overwriting of the image data can be performed as shown in FIG. Compared with the method of switching the pixel density by performing the method (FIG. 7A), the edge portion of the data line to be written and scanned becomes smoother (FIG. 7B), and the print quality can be improved. Note that FIG.
7A shows an example of ordinary overwriting without controlling the scanning line position of the laser beam in the sub-scanning direction, and FIG. 7B shows the writing of write data by controlling the scanning line position of the laser beam in the sub-scanning direction. An example is shown in which overwriting is performed with a reduced interval.

Next, a specific operation when switching the pixel density shown in FIG. 6 in the optical writing device according to the second embodiment will be described with reference to FIG. In the figure, when scanning is performed at a pixel density of 600 spi, a horizontal synchronization signal HSYNC output from the synchronization detector 32 to the main control unit 30 is used.
Output image data D1, D2,.
Printing is performed for each scanning line at a scanning line interval set according to 0 spi (FIGS. 8A and 8B). At this time, since the position of each scanning line does not need to be changed,
The beam position control signal BP output to the OD 14 remains at the low level (0 V) (FIG. 8C).

On the other hand, when overwriting is performed by switching the pixel density from 600 spi to 300 spi, as described above, the image data D1 is applied to two adjacent scanning lines, for example, the first and second lines. 3rd line, 4th
The horizontal synchronization signal H such as the image data D2 on the line, the image data D3 on the fifth and sixth lines, and so on.
In synchronization with SYNC, the same image data is repeatedly output twice to an adjacent scanning line, and the position of a scanning line for scanning the same image data for the second time, specifically, FIG.
In the example of (E), the second scanning line and the fourth scanning line are set to (1 /
3) By scanning while deflecting the laser beam 24 so as to move P upward in FIG. 6B and overwriting image data, overwriting at a pixel density of 300 spi can be performed. In this case, the beam position control signal BP of level -V1 necessary to move the second and fourth scanning lines upward by (1/3) P in FIG. 6B is synchronously detected. The main controller 30 synchronizes with the horizontal synchronization signal HSYNC output from the
The scanning line position of the laser beam 24 is changed in the sub-scanning direction according to the signal level of the beam position control signal BP.

In the case where image data is written at a pixel density of 240 spi shown in FIG. 4, even when the image data is overwritten when the pixel density is 480 spi in the second embodiment, the image data after the change in the first embodiment is changed. Pixel density (4
By moving the scanning line of the pixel density (600 spi) before the pixel density switching in accordance with the pixel density (80 spi), it becomes possible by using together the technique of switching to the pixel density (480 spi).

In this embodiment, when data having different pixel densities exist in one page to be printed, for example, a character is printed at 300 spi and a photograph or the like is printed at 600 spi. It is possible to print by switching the pixel density.

According to the optical writing apparatus according to the second embodiment of the present invention, the writing is performed by narrowing the interval between the writing positions of the image data to be overwritten in the sub-scanning direction. The edge portion of the scanned line can be made smoother than the overwriting of data, and the printing quality can be improved.

[0053]

As described above, according to the first aspect of the present invention, when the pixel density is switched, the number of rotations of the rotary polygon mirror for scanning the light beam on the photoconductor is not changed. Since the scanning line position of the light beam is controlled so that it can be changed in the sub-scanning direction for each line according to the pixel density, no time is required for switching the pixel density when writing image data at different pixel densities. And the image data can be written at high speed.

According to the second and third aspects of the present invention,
Since the writing is performed by narrowing the interval between the writing positions of the data to be overwritten in the sub-scanning direction, in addition to the effect obtained by the invention according to claim 1, it is possible to perform the writing more than the overwriting of the image data normally performed. The edge of the line to be scanned can be smoothed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of an optical writing device according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a light amount control circuit that performs light amount control of a laser diode included in a main control unit in FIG. 1;

FIG. 3 is an explanatory view conceptually showing an operation when switching the pixel density of the optical writing device according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a relationship between a pixel density set at the time of pixel density switching and a scanning line at the pixel density before pixel density switching used at that time in the optical writing device according to the embodiment of the present invention.

FIG. 5 is a timing chart showing a specific operation when switching the pixel density shown in FIG. 3 in the optical writing device according to the first embodiment of the present invention.

FIG. 6 is an explanatory view conceptually showing an operation when switching the pixel density of the optical writing device according to the second embodiment of the present invention.

FIG. 7 is an explanatory diagram showing overwriting of image data of the optical writing device according to the second embodiment of the present invention in comparison with normal overwriting of image data.

FIG. 8 is a timing chart showing a specific operation when switching the pixel density shown in FIG. 6 in the optical writing device according to the second embodiment of the present invention.

FIG. 9 is a block diagram showing a configuration of a conventional optical writing device.

[Explanation of symbols]

 Reference Signs List 10 light source 14 electro-optical deflector (second light beam deflecting unit) 16 polygon mirror (first light beam deflecting unit) 26 photoconductor 28 polygon mirror motor 30 main control unit (control unit) 32 synchronization detector 40 microcomputer 50 Light control circuit

Claims (3)

[Claims] 1. An optical writing apparatus for forming an image by scanning a light beam emitted from a light source on a photoconductor so as to change a pixel density according to a pixel density designation signal from the outside, wherein: First light beam deflecting means for deflecting the light beam in the main scanning direction on the photoconductor, and second light beam deflecting means provided in an optical path from the light source to the photoconductor for deflecting the light beam in the sub-scanning direction Control means for driving and controlling the light beam deflecting means so that the scanning line position of the light beam can be changed in the sub-scanning direction line by line in accordance with a pixel density specified by a pixel density specifying signal for specifying a pixel density. An optical writing device, comprising: 2. The optical writing device according to claim 1, wherein the range in which the pixel density can be switched is equal to or less than the maximum pixel density of the optical writing device. 3. When the relationship of pixel density × 2 ≦ maximum pixel density is satisfied, the interval between write positions of overwritten data is narrowed in the sub-scanning direction, and the same write data is written twice.
3. The optical writing device according to claim 2, wherein the optical writing device performs overwriting.