JP2005125632A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which is low-cost and can carry out a quantity of light control of each laser beam by an appropriate timing by reducing the number of laser beam detecting means (BD sensors). <P>SOLUTION: The image forming apparatus which deflects and scans two of a first and a second laser beams by one rotary polygon mirror is configured so that a timing of a first and a second laser quantity of light control parts for controlling a quantity of light of the first and the second laser beams is controlled by a first and a second timing control parts 402 and 403, respectively on the basis of the BD sensor 401 which is present on a scanning path of the first laser beams and generates a BD signal to be a reference of an image writing timing of the first laser beams when the laser beams are inputted, and the BD signal detected by the BD sensor 401. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that scans two laser beams with a single rotating polygon mirror, and more particularly to timing control of a laser light quantity control unit.

  2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic method, a laser beam modulated by an image signal is reflected by a scanner having a rotating polygon mirror (hereinafter sometimes abbreviated as a polygon mirror or polygon) and is reflected on a photosensitive member. Image formation is performed by scanning. A drum-shaped photosensitive member is often used and is called a photosensitive drum. When this method is applied to a color laser printer, a color image is formed by overlaying a plurality of images of different colors (for example, four colors of yellow (Y), magenta (M), cyan (C), and black (BK)). It is formed on a medium. Configurations for achieving this superposition technique include the following.

  As one configuration, the first color image signal is scanned on the photosensitive drum to create a latent image, and a developer is attached for visualization, transferred to recording paper, and then the photosensitive drum is cleaned, and again The second color image signal is scanned on the same photosensitive drum to form a latent image, and the same process as the first is performed. However, the developer of the second color is used. The same process is repeated for the third color image signal and the fourth color image signal. In this way, one image is recorded by superimposing images developed multiple times on the same recording paper.

  In the second configuration, the same number of photosensitive drums are provided for a plurality of image signals, and a latent image is created on the photosensitive drum corresponding to each color image signal, and each of the different colors is provided. Visualization development is performed with a developer, and then sequentially transferred onto recording paper. In this case, one laser beam generating unit, one scanner, one BD (Beam Detect) sensor for detecting the image writing timing of the laser beam generating unit, and one photosensitive drum are prepared for one image signal. Therefore, when there are a plurality of image signals to be superimposed, the same number of laser beam generating means, scanners, photosensitive drums and BD sensors as the image signals are required.

  The first configuration performs a series of charging-exposure-development-transfer-cleaning electrophotographic processes on the first color image signal, and then performs the same process again on the second color image signal. Both the third color image signal and the fourth color image signal must be performed in time series. Therefore, there is a problem that the printing time for one sheet is very long.

  The second configuration has an advantage that printing can be performed in a short time compared to the first configuration. However, as described above, the laser beam generating means, the scanner, the photosensitive drum, and the BD sensor must be prepared in the same number as the number of the respective color image signals, which causes a problem that the apparatus becomes large and expensive.

  In either configuration, since the images of the respective colors are superimposed, so-called color misregistration, which occurs when the image positions of the respective colors are not aligned, is likely to occur. In particular, the latter configuration forms a color image using different scanners and photosensitive drums, and thus has a problem that registration for each color is difficult to match. Therefore, registration for each color is performed. For example, a resist detection pattern image is formed on an intermediate transfer belt (abbreviated as ITB) or an electrostatic transfer belt (abbreviated as ETB) and read by a resist detection sensor. Means for performing correction by feeding back to an image writing position or the like is used.

  The resist detection sensor reads a resist detection image pattern formed on the ITB or ETB with a light source and reads the reflected light with a light reception sensor, and the time of the signal of the light reception sensor when the resist detection pattern passes Electrical processing is performed by using a typical intensity change as positional deviation information.

  Usually, the printing time of the laser printer is shortened by increasing the rotation speed of the scanner. A conventional scanner rotation speed of a laser printer is usually a high speed rotation of 20000 rpm or more. Furthermore, the mirror used in the scanner is a polygon mirror, a polygon mirror, and the error in deflection angle causes position fluctuations on the photosensitive drum due to the optical path length of the laser beam. It is necessary that the amount of vibration is small, and that vibration due to high-speed rotation is small. Therefore, the motor becomes large in order to obtain a stable high-speed rotation of the polygon mirror, and the mirror manufacturing process is required for the scanner manufacturing process because it is necessary to limit the tilting error on each mirror surface. For this reason, the yield of manufacture is bad and it has become very expensive.

  An apparatus having a plurality of scanners as described above becomes large and expensive.

In order to reduce the cost, a common scanner is used for a plurality of colors (see, for example, Patent Document 1 below). Further, the scanner is used in common, and one of the plurality of light sources is used as one light source. A device in which a BD sensor is provided only for such a device has been proposed (for example, see Patent Document 2 below). To briefly describe Patent Document 2, a plurality of light sources are configured to simultaneously scan the photoreceptor by different surfaces of the polygon, and other light sources other than the light source provided with the BD sensor are polygon rotational phase differences ( Since the angle difference is known in advance, it can be estimated from the BD signal of the light source provided with the BD sensor.
Japanese Patent Publication No. 4-51829 JP-A-4-313776

  Normally, the light amount control for detecting the light amount of the laser diode and setting it to an appropriate light amount is performed every time each surface of the polygon is scanned. The light amount control is performed at a timing when the laser beam scans an area other than a so-called image area on the image carrier. In order to generate the timing signal, light detection means (hereinafter referred to as a BD sensor) is provided on the scanning path of the laser beam. Then, the light quantity control timing signal is generated based on a signal for detecting a laser beam scanning timing by scanning a laser beam on the BD sensor.

  However, as shown in FIG. 1, two laser beams are simultaneously scanned by one polygon, and a BD sensor is disposed only on one laser beam, and BD detection of the other laser beam is performed by a BD signal of a laser having a BD sensor. If the configuration is to detect from the above, there is a problem that the timing for performing the light amount control of the laser beam not provided with the BD sensor on the scanning path is not known.

  The present invention has been made under such circumstances, and the number of laser beam detecting means (BD sensors) can be reduced, and the light quantity control of each laser beam can be performed at an appropriate timing at low cost. It is an object of the present invention to provide a forming apparatus.

  In order to solve the above problems, in the present invention, the image forming apparatus is configured as described in the following (1) to (3).

(1) The first and second laser beam generating means, the first and second image carriers, and the first and second laser beams generated by the first and second laser beam generating means are simultaneously used. One rotary polygon mirror that deflects and scans the respective surfaces of the first and second image carriers, and the first laser beam when the laser beam is input, on the scanning path of the first laser beam. Laser beam detecting means for generating a BD signal that serves as a reference for image writing timing, and first and second laser light quantity control means for controlling the light quantity of the first and second laser beams, In the image forming apparatus configured to deflect and scan the second laser beam by different surfaces of the rotary polygon mirror,
An image forming apparatus comprising first and second timing control means for generating timing signals of the first and second laser light quantity control means based on BD signals detected by the laser beam detection means.

(2) Simultaneously combining the first and second laser beam generating means, the first and second image carriers, and the first and second laser beams generated by the first and second laser beam generating means. One rotary polygon mirror that deflects and scans the respective surfaces of the first and second image carriers, and the first laser beam when the laser beam is input, on the scanning path of the first laser beam. Laser beam detecting means for generating a BD signal that serves as a reference for image writing timing, and first and second laser light quantity control means for controlling the light quantity of the first and second laser beams, In the image forming apparatus configured to deflect and scan the second laser beam by different surfaces of the rotary polygon mirror,
Based on the BD signal detected by the laser beam detecting means, a pseudo BD signal generating means for generating a pseudo BD signal serving as a reference of the image writing timing of the second laser beam;
First timing control means for generating a timing signal of the first laser light quantity control means based on a BD signal detected by the laser beam detection means;
Second timing control means for generating a timing signal of the second laser light quantity control means based on the pseudo BD signal generated by the pseudo BD signal generation means;
An image forming apparatus.

(3) Simultaneously combining the first and second laser beam generating means, the first and second image carriers, and the first and second laser beams generated by the first and second laser beam generating means. One rotary polygon mirror that deflects and scans the respective surfaces of the first and second image carriers, and the first laser beam when the laser beam is input, on the scanning path of the first laser beam. Laser beam detecting means for generating a BD signal that serves as a reference for image writing timing, and first and second laser light quantity control means for controlling the light quantity of the first and second laser beams, In the image forming apparatus configured to deflect and scan the second laser beam by different surfaces of the rotary polygon mirror,
An image forming apparatus comprising timing control means for generating timing signals of the first and second laser light quantity control means based on a BD signal detected by the laser beam detection means.

  According to the present invention, it is possible to provide an image forming apparatus that can reduce the number of laser beam detecting means (BD sensors), can control the light amount of each laser beam at an appropriate timing, and at a low cost.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  FIG. 2 is a block diagram illustrating the configuration of the “color laser printer” according to the first embodiment. In FIG. 2, 201 is a color laser printer of this embodiment, and 202 is a host computer.

  This embodiment is an example of a four-drum type color laser printer, and four-color image formation is performed to form a color image in which images of four colors (yellow Y, magenta M, cyan C, and black BK) are superimposed. Department.

  The image forming unit includes toner cartridges 207 to 210 having a photosensitive drum as an image carrier and scanner units 205 and 206 having laser diodes for generating a laser beam as a light source for image exposure. Among these, the toner cartridge has one for each of the four colors. However, the scanner unit is characterized by two common ones for yellow and magenta and one common for cyan and black. This scanner unit will be described in detail later.

  When the image data from the host computer 202 is received, the video controller 203 in the laser printer 201 develops the image data into bitmap data and generates a video signal for image formation. The video controller 203 and the engine controller 204 perform serial communication to transmit and receive information. The video signal is transmitted to the engine controller 204. The engine controller 204 drives laser diodes (not shown) in the scanner units 205 and 206 in accordance with the video signal, and photosensitive drums (not shown) in the toner cartridges 207 to 210. An image is formed on each of them. The photosensitive drum is in contact with the intermediate transfer belt ITB 211, and images formed on the photosensitive drums of the respective colors are transferred onto the ITB 211 and sequentially superimposed to form a color image. The image forming process will be described in detail later.

  There is also a registration detection sensor 212 that monitors the registration position of the image on the ITB 211.

  FIG. 3 is a sectional view showing the structure of the color laser printer. The same components as those in FIG. 2 are denoted by the same reference numerals. The video controller and engine controller described in FIG. 2 are not shown.

  Reference numerals 301 to 304 denote photosensitive drums, each of which is used to form a black image 301, 302 cyan, 303 magenta, and 304 yellow.

  FIG. 1 is a diagram showing details of the scanner units 205 and 206 in FIG. For convenience, the configuration of the scanner unit 205 will be described. Since 206 has the same configuration as 205, description thereof will be omitted. In FIG. 1, reference numerals 101 and 102 denote laser diodes, which are driven and controlled by a control signal from an engine controller (not shown). For convenience, 101 is referred to as LD1, and 102 is referred to as LD2. Reference numeral 103 denotes a polygon mirror, which is rotated at a constant speed in the direction of the arrow in the drawing by a scanner motor (not shown), and scans while reflecting the beams from the laser diode LD1 and the laser diode LD2. In this embodiment, the beam from the laser diode LD1 is irradiated to the polygon mirror 103 simultaneously from the right side of the drawing, and the beam from the laser diode LD2 is simultaneously irradiated from the left side of the drawing.

  Reference numeral 106 denotes an optical sensor (corresponding to the laser beam detecting means in the claims) which is on the scanning path of the beam from the laser diode LD1 and generates a signal when the laser beam is incident, and is called a BD (BeamDetect) sensor. This BD sensor is only on the scanning path of the laser diode LD1, and does not exist on the scanning path of the other laser diode LD2.

  The laser beam emitted from the laser diode LD1 is scanned while being reflected by the polygon mirror 103, further reflected by the folding mirror 104, and scanned on the photosensitive drum 302 from right to left.

  In practice, the laser beam passes through various lenses (not shown) for focusing on the photosensitive drum or for converting the laser beam from diffused light to parallel light. However, the description is omitted this time.

  The laser diode LD1 generates a laser beam modulated by a video signal generated by a video controller (not shown) and scans the photosensitive drum 302. On the other hand, the photosensitive drum 302 is rotated in the direction of the arrow shown in FIG. 1 at a constant speed by a drum motor (not shown). The surface of the photosensitive drum 302 is uniformly charged by the charging roller 306 shown in FIG. 3, and the surface is scanned with a laser beam modulated by a video signal generated by a video controller. An electrostatic latent image is formed. The electrostatic latent image is visualized as a toner image by the developing device 310 of FIG.

  Usually, the video controller transmits a video signal to the engine controller a predetermined time after detecting the output signal of the BD sensor. By doing so, the image writing position by the laser beam on the photosensitive drum always coincides. On the other hand, the laser diode LD2 also forms an electrostatic latent image on the photosensitive drum 301 in the same manner as the laser diode LD1.

  Since the BD signal does not exist on the scanning path of the laser diode 102, the laser diode is simulated in a timing that corrects the surface division error of each surface of the polygon with reference to the BD signal of the laser diode LD1. The BD signal of LD2 is generated. Hereinafter, the BD signal of the laser diode LD2 is referred to as a pseudo BD signal, and the circuit for generating the BD signal of the laser diode LD2 is referred to as a pseudo BD signal generator.

  In this manner, a cyan (C) color image by the laser diode LD1 is formed on the photosensitive drum 302, and a black (BK) color image by the laser diode LD2 is formed on the photosensitive drum 301.

  The scanner unit 205 in FIG. 3 has been described above. The scanner unit 206 is exactly the same as 205. That is, magenta (M) and yellow (Y) color images are formed on the photosensitive drum 303 and the photosensitive drum 304, respectively.

  Each color image is transferred (primary transfer) so as to be sequentially superimposed on the ITB 211 conveyed at a constant speed. That is, first, a yellow (Y) image is transferred to the ITB, and then transferred onto magenta (M), cyan (C), and black (BK) in this order to form a color image.

  The color image formed on the ITB 211 is conveyed by the ITB 211. On the other hand, the sheet in the cassette 314 is picked up by the pick-up roller 316 at the position of the transfer roller 318 so that the timing exactly matches the image on the ITB 211. The color image is pressed by the transfer roller 318 and transferred from the ITB 211 to the sheet (secondary transfer). The sheet on which the image has been transferred is fixed by the fixing device 313 by heat and pressure, and is then discharged to the upper portion of the printer and the paper discharge tray 317.

  The above is a series of image forming processes.

  Next, laser light amount control according to the first embodiment will be described with reference to the block diagram of FIG. 4 and the timing chart of FIG. FIG. 4 is a block diagram illustrating a configuration of a timing control unit of an APC (laser light amount control unit) in the first embodiment. Based on the output signal of the BD sensor 401 of the laser diode LD1, the LD1APC timing control unit 402 generates a light amount control timing signal of the laser beam 1. Similarly, the LD2 APC timing control unit 403 generates a light amount control timing signal of the laser beam 2 based on the output signal of the BD sensor 401 of the laser diode LD1.

  The operations of the LD1APC timing control unit 402 and the LD2APC timing control unit 403 will be described with reference to the timing chart of FIG. S1 is a timing chart of the laser diode LD1. S501 is a BD signal of the laser diode LD1 and an output signal of the BD sensor 401. S502 represents an image area, and the photosensitive body 302 is exposed by blinking the laser diode LD1 according to video data while scanning the photosensitive body with the laser beam of the laser diode LD1. S503 is the timing when the laser light amount control of the laser diode LD1 is performed. As shown in the timing chart, the laser light amount control of the laser diode LD1 needs to be performed outside the image area. This is because when the laser light quantity control is performed, the laser is continuously turned on, and thus the photoconductor is exposed when the photoconductor is scanned during this period. The timing S503 for controlling the laser light quantity of the laser diode LD1 can be made by counting the counter for a predetermined period T1 with reference to the falling edge of the BD signal S501 of the laser diode LD1. Further, an appropriate timing signal can be generated by counting the period during which the laser light amount control is performed with the same counter. S2 is a timing chart of the laser diode LD2. S504 is a pseudo BD signal. S505 represents an image area of the laser diode LD2, and is an area in which the photoconductor 301 is exposed by blinking the laser diode LD2 according to video data while scanning the photoconductor 301 with the laser beam of the laser diode LD2. S506 is the timing for controlling the laser light quantity of the laser diode LD2. As shown in the timing chart, the laser light amount control of the laser diode LD2 needs to be performed outside the image area. This is because when the laser light quantity control is performed, the laser is continuously turned on, and thus the photoconductor is exposed when the photoconductor is scanned during this period. The timing S506 for controlling the laser light quantity of the laser diode LD2 can be made by counting only a predetermined period T2 with reference to the falling edge of the BD signal S501 of the laser diode LD1. Further, an appropriate timing signal can be generated by counting the period during which the laser light amount control is performed with the same counter. As described above, the laser light amount control of the laser diode without the BD sensor can be performed at an appropriate timing.

  In this embodiment, a four-sided polygon has been described. However, it is not limited to four-sided polygons. In this embodiment, an image forming apparatus that includes an ITB and forms an image has been described. However, the present invention is also applicable to an ETB image forming apparatus.

  Next, laser light quantity control of the “color laser printer” according to the second embodiment will be described with reference to the block diagram of FIG. 6 and the timing chart of FIG. Since the overall hardware configuration of the present embodiment is the same as that of the first embodiment, the description of the first embodiment is cited and the description thereof is omitted here.

  FIG. 6 is a block diagram showing the configuration of the timing control unit of APC in this embodiment. Based on the output signal of the BD sensor 401 of the laser diode LD1, the LD1APC timing control unit 402 generates a laser light amount control timing signal of the laser beam 1. In this embodiment, the LD2 APC timing control unit 403 generates a laser light amount control timing signal of the laser beam 2 with reference to the pseudo BD signal generation unit 404.

  The operations of the LD1APC timing control unit 402 and the LD2APC timing control unit 403 will be described with reference to the timing chart of FIG. S1 is a timing chart of the laser diode LD1. S501 is a BD signal of the laser diode LD1 and an output signal of the BD sensor 401. S502 represents an image area, which is an area in which the photoconductor is exposed by blinking the laser diode LD1 according to video data while scanning the photoconductor with the laser beam of the laser diode LD1. S503 is the timing when the laser light amount control of the laser diode LD1 is performed. As shown in the timing chart, the laser light amount control of the laser diode LD1 needs to be performed outside the image area. This is because when the laser light quantity control is performed, the laser is continuously turned on, and thus the photoconductor is exposed when the photoconductor is scanned during this period. The timing S503 for controlling the laser light quantity of the laser diode LD1 can be made by counting the counter for a predetermined period T1 with reference to the falling edge of the BD signal S501 of the laser diode LD1. Further, an appropriate timing signal can be generated by counting the period during which the laser light amount control is performed with the same counter. S2 is a timing chart of the laser diode LD2. S 504 is a pseudo BD signal generated by the pseudo BD signal generator 404. S505 represents an image area of the laser diode LD2, and is an area in which the photoconductor is exposed by blinking the laser diode LD2 according to video data while scanning the photoconductor with the laser beam of the laser diode LD2. S506 is the timing when the laser light quantity control of the laser diode LD2 is performed. As shown in the timing chart, the laser light amount control of the laser diode LD2 needs to be performed outside the image area. This is because when the laser light quantity control is performed, the laser is continuously turned on, and thus the photoconductor is exposed when the photoconductor is scanned during this period. The timing S506 for controlling the laser light amount of the laser diode LD2 can be made by counting the count for a predetermined period T2 with reference to the falling edge of the pseudo BD signal S504. Further, an appropriate timing signal can be generated by counting the period during which the laser light quantity control is performed with the same counter. As described above, the laser light amount control of the laser diode without the BD sensor can be performed at an appropriate timing.

  As described above, according to the present embodiment, the laser light amount control of the second laser beam can be performed with appropriate and highly accurate timing.

  In this embodiment, a four-sided polygon has been described. However, it is not limited to a four-sided polygon. In this embodiment, an image forming apparatus that includes an ITB and forms an image has been described. However, the present invention is also applicable to an ETB image forming apparatus.

  Next, laser light amount control of the “color laser printer” of the third embodiment will be described using the block diagram of FIG. 8 and the timing chart of FIG. Since the overall hardware configuration of the present embodiment is the same as that of the first embodiment, the description of the first embodiment is cited and the description thereof is omitted here.

  FIG. 8 is a block diagram showing the configuration of the timing control unit of APC in this embodiment. Based on the output signal of the BD sensor 401 of the laser diode LD1, the LD1APC timing control unit 401 generates a laser light amount control timing signal of the laser beam 1. In this embodiment, the laser light amount control timing of the laser beam 2 is set to the same timing as the laser light amount control timing of the laser beam 1.

  The operation of the LD1APC timing control unit 402 will be described with reference to the timing chart of FIG. S1 is a timing chart of the laser diode LD1. S501 is a BD signal of the laser diode LD1 and an output signal of the BD sensor 401. S502 represents an image area, which is an area in which the photoconductor is exposed by blinking the laser diode LD1 according to video data while scanning the photoconductor with the laser beam of the laser diode LD1. S503 is the timing when the laser light amount control of the laser diode LD1 is performed. As shown in the timing chart, the laser light amount control of the laser diode LD1 needs to be performed outside the image area. This is because when the laser light quantity control is performed, the laser is continuously turned on, and thus the photoconductor is exposed when the photoconductor is scanned during this period. The timing S503 for controlling the laser light quantity of the laser diode LD1 can be made by counting the counter for a predetermined period T1 with reference to the falling edge of the BD signal S501 of the laser diode LD1. Further, an appropriate timing signal can be generated by counting the period during which the laser light quantity control is performed with the same counter. S2 is a timing chart of the laser diode LD2. S504 is a pseudo BD signal. S505 represents an image area of the laser diode LD2, and is an area in which the photoconductor is exposed by blinking the laser diode LD2 according to video data while scanning the photoconductor with the laser beam of the laser diode LD2. S506 is the timing when the laser light quantity control of the laser diode LD2 is performed. As shown in the timing chart, the laser light amount control of the laser diode LD2 needs to be performed outside the image area. This is because when the laser light quantity control is performed, the laser is continuously turned on, and thus the photoconductor is exposed when the photoconductor is scanned during this period. The timing generated by the LD1APC timing control unit is used as it is for the timing S506 for controlling the laser light quantity of the laser diode LD2. That is, the laser light amount control of the laser diode LD1 and the laser light amount control of the laser diode LD2 are simultaneously performed. With such a configuration, it is not necessary to add a circuit for generating a laser light amount control timing signal for the laser beam 2.

  As described above, according to the present embodiment, the laser light amount control of the second laser diode can be performed at an appropriate timing with a simple configuration.

  In this embodiment, a four-sided polygon has been described. However, it is not limited to a four-sided polygon. In this embodiment, an image forming apparatus that includes an ITB and forms an image has been described. However, the present invention is also applicable to an ETB image forming apparatus.

1 is a perspective view showing a schematic configuration of a scanner unit used in Embodiment 1. FIG. Block diagram showing the configuration of the first embodiment Sectional drawing which shows the structure of Example 1 The block diagram which shows the structure of the timing control part of APC in Example 1. FIG. Timing chart showing the operation of the timing controller The block diagram which shows the structure of the timing control part of APC in Example 2. FIG. Timing chart showing the operation of the timing controller The block diagram which shows the structure of the timing control part of APC in Example 3. FIG. Timing chart showing the operation of the timing controller

Explanation of symbols

101 First laser diode 102 Second laser diode 103 Polygon mirror 106 BD sensor 205 Scanner (cyan, black)
206 Scanner (yellow, magenta)
301 Photosensitive drum (black)
302 Photosensitive drum (cyan)
303 Photosensitive drum (magenta)
304 Photosensitive drum (yellow)
402 LD1APC timing control unit 403 LD2APC timing control unit

Claims (3)

The first and second laser beam generating means, the first and second image carriers, and the first and second laser beams generated by the first and second laser beam generating means are simultaneously applied to the first and second laser beams. , One rotary polygon mirror that deflects and scans on the respective surfaces of the second image carrier, and on the scanning path of the first laser beam, when the laser beam is inputted, image writing of the first laser beam is performed. Laser beam detecting means for generating a BD signal as a timing reference, and first and second laser light quantity control means for controlling the light quantities of the first and second laser beams, In the image forming apparatus configured to deflect and scan the laser beams by different surfaces of the rotary polygon mirror,
An image comprising first and second timing control means for generating timing signals of the first and second laser light quantity control means based on the BD signal detected by the laser beam detection means, respectively. Forming equipment. The first and second laser beam generating means, the first and second image carriers, and the first and second laser beams generated by the first and second laser beam generating means are simultaneously applied to the first and second laser beams. , One rotary polygon mirror that deflects and scans on the respective surfaces of the second image carrier, and on the scanning path of the first laser beam, when the laser beam is inputted, image writing of the first laser beam is performed. Laser beam detecting means for generating a BD signal as a timing reference, and first and second laser light quantity control means for controlling the light quantities of the first and second laser beams, In the image forming apparatus configured to deflect and scan the laser beams by different surfaces of the rotary polygon mirror,
Based on the BD signal detected by the laser beam detecting means, a pseudo BD signal generating means for generating a pseudo BD signal serving as a reference of the image writing timing of the second laser beam;
First timing control means for generating a timing signal of the first laser light quantity control means based on a BD signal detected by the laser beam detection means;
Second timing control means for generating a timing signal of the second laser light quantity control means based on the pseudo BD signal generated by the pseudo BD signal generation means;
An image forming apparatus comprising: The first and second laser beam generating means, the first and second image carriers, and the first and second laser beams generated by the first and second laser beam generating means are simultaneously applied to the first and second laser beams. , One rotary polygon mirror that deflects and scans on the respective surfaces of the second image carrier, and on the scanning path of the first laser beam, when the laser beam is inputted, image writing of the first laser beam is performed. Laser beam detecting means for generating a BD signal as a timing reference, and first and second laser light quantity control means for controlling the light quantities of the first and second laser beams, In the image forming apparatus configured to deflect and scan the laser beams by different surfaces of the rotary polygon mirror,
An image forming apparatus comprising timing control means for generating timing signals of the first and second laser light quantity control means based on a BD signal detected by the laser beam detection means.

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