JP2003063064A - Multi-beam image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide in a simple and inexpensive configuration a circuit for synchronizing a plurality of image data of scanning lines adjacent in a sub- scanning direction which are needed to be synchronized to the same scanning cycle when an image processing such as an edge smoothing is carried out in an image forming device using a plurality of laser beams. SOLUTION: The circuit is constituted of an FIFO 501 which makes the image data CVD1 of the scanning lines outputted beforehand synchronized with image clock signals VCLK2 which has been synchronized with the image data CVD2 of the scanning lines outputted afterwards, serial-parallel converters 505 and 506, and register files 507 508 for temporarily storing the image data synchronized with the image clock signals VCLK2. The register files 505 and 506 are controlled by image clock signals VCLK1.

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 such as a digital copying machine or a laser printer which uses a plurality of laser beams (multi-beams).

[0002]

2. Description of the Related Art In an image forming apparatus such as a digital copying machine or a laser printer, a photoconductor such as a photoconductor drum or a photoconductor belt is moved in the sub-scanning direction by a driving means and uniformly charged by a charging means. After that, by scanning the laser beam on the photoconductor in parallel with the main scanning direction by the scanning device to write an image, an electrostatic latent image is formed on the photoconductor,
This electrostatic latent image is developed by developing means and transferred onto a transfer material such as recording paper or an intermediate transfer body.

In an image forming apparatus using one laser beam, the fact that the amount of toner (coloring material) adhered increases or decreases depending on the intensity of the laser beam is used as described in Japanese Patent Laid-Open No. 8-310057. A method for improving image quality (edge smoothing) has been proposed.

FIG. 1 is a block diagram showing an image forming apparatus using one laser beam, which is equipped with an edge smoothing circuit which is a technique for improving image quality described in Japanese Patent Laid-Open No. 8-310057. The edge smoothing circuit 103 is mounted between the controller 101 and the engine 102, and has a synchronization detection signal BD from the engine, a pixel clock signal VCLK synchronized with the synchronization detection signal BD from the controller, and an image data signal synchronized with the pixel clock signal VCLK. It receives a CVD and outputs enhanced image data to the engine.

FIG. 2 shows the edge smoothing circuit 10.
3 shows a block diagram of FIG. Edge smoothing circuit 103
Is the line memory 151 and the sample window 152.
, A logic circuit 153, and a pulse width modulation circuit (PWM) 15
4 and 4. The line memory 151 receives the image data signal CVD from the controller 101, temporarily stores the image data of a plurality of scanning lines, and passes it to the sample window 152. The sample window 152 collectively passes a pixel to be recorded (reference pixel) and image data for several pixels around the reference pixel to the logic circuit 153. The logic circuit 153 determines what kind of image the reference pixel is part of by the template matching, and passes the determination result to the PWM 154. Based on the determination result, the PWM 154 applies appropriate pulse width modulation if the reference pixel is part of the edge, and generates an enhanced image data (laser modulation) signal VDe for recording the reference pixel.

FIG. 3 is a perspective view showing the structure of an optical system of an electrophotographic recording type engine. Here, the number of laser beams is two. The two laser beams are emitted from a light source device having two semiconductor lasers or a semiconductor laser array, and are deflected and scanned by a scanning unit such as a rotating polygon mirror to perform an optical element such as an fθ lens (not shown in the figure). By irradiating the photosensitive drum 313 via the two laser beams, the two laser beams are simultaneously scanned on the photosensitive drum 313 in parallel in the main scanning direction to write an image.

FIG. 4 is a diagram showing a state in which the laser beam emitted from the light source device is applied to the photosensitive drum. The beam detector 314 arranged on the main scanning start side outside the writing area receives the first laser beam of the two laser beams to start recording, and receives the synchronization detection signal 1
(BD1) is generated. Similarly, of the two laser beams, the second laser beam for starting recording is received to generate the synchronization detection signal 2 (BD2). The synchronization detection signal 1
Pixel clock 1 (VCLK1) is generated by a pixel clock generation circuit (not shown in the figure) with reference to. Similarly, the pixel clock generation circuit generates a pixel clock 2 (VCLK2) based on the synchronization detection signal 2. A writing position is determined by these pixel clocks (VCLK1, VCLK2), and a laser beam 311 is emitted by modulating and driving the laser element of the semiconductor laser or the semiconductor laser array by an image data signal.

[0008]

The edge smoothing means in the conventional image forming apparatus uses one laser beam, and no consideration is given to adaptation to the image forming apparatus using a plurality of laser beams. . In particular, the signal processing for edge smoothing is performed by determining what edge the reference pixel is located in relation to the peripheral image of the reference pixel, but the image on the adjacent scanning line is different from that of another laser beam. In the image forming apparatus which records in parallel with each other, the conventional edge smoothing means cannot be simply diverted.

In an image forming apparatus using a plurality of laser beams, image data of adjacent scanning lines in the sub-scanning direction is
It is output in the same scanning cycle and a different scanning cycle. In order to perform image processing such as edge smoothing in an image forming apparatus using a plurality of laser beams, it is necessary to synchronize image data of adjacent scanning lines in the sub-scanning direction with the same scanning cycle. As a method of synchronizing image data of different scanning cycles, a first-in first-out memory (abbreviated as FIFO) that can independently control a write cycle and a read cycle is generally used.

The method of synchronizing the image data of the scanning lines adjacent to each other in the sub-scanning direction with the same scanning period for the edge smoothing is the image data of the scanning line which starts scanning first among the two scanning lines. , And stores it in the first FIFO. Next, the image data of the scanning line that starts scanning second from the two scanning lines is acquired and stored in the second FIFO. When the image data stored in the first FIFO and the second FIFO is output in synchronization with the scanning position of the laser beam of the two laser beams which starts recording first,
The image data of one scanning line is synchronized with the scanning line of the two scanning lines which starts scanning first. However, since the scan line that starts scanning second from the two scan lines starts scanning after the scan line that starts scanning first, one scan from the first FIFO and the second FIFO. It is necessary to read it with a delay.

When the image data of the scanning lines adjacent in the sub-scanning direction are synchronized with each other in the same scanning cycle by this method, the image data of the scanning line which starts scanning first among the two scanning lines is one scanning line. Since it is delayed by a cycle, the FIFO for storing the image data needs to be able to acquire and store all the image data of the scanning line. Therefore, the number of laser beams is large and A
In an image forming apparatus capable of printing two or more four sizes arranged side by side in the scanning direction, the circuit scale of the FIFO for synchronizing the image data becomes large and expensive.

An object of the present invention is to use in image processing such as edge smoothing for smoothing an inclined portion of a contour in an image forming apparatus for recording a plurality of scanning lines in parallel by using a plurality of laser beams. It is to provide an image data synchronizing means.

Further, the present invention is to provide the image data synchronizing means with a small size and a low price while suppressing an increase in circuit scale.

[0014]

The above object is to provide a control circuit for generating a plurality of laser modulation signals for controlling a plurality of laser beams on the basis of image data of a plurality of scanning lines. In the image forming apparatus that records a plurality of scanning lines in parallel by the laser beam of, the control circuit acquires and stores image data of the plurality of scanning lines, and finally, among the plurality of laser beams, First memory means for outputting in synchronization with a scanning position of one laser beam for starting recording, and for synchronizing with a scanning position of one laser beam for starting recording first among the plurality of laser beams And an image data synchronization circuit having a second memory means for acquiring and storing image data output from the first memory means.

In order to synchronize the image data of the scanning lines adjacent to each other in the sub-scanning direction with the same scanning cycle, the image data of the plurality of scanning lines acquired and stored in the first memory means are converted into a plurality of image data. The laser beam is output in synchronization with the scanning position of one of the laser beams that finally starts recording.
Next, in the second memory means, the image data output by the first memory means is acquired in synchronization with the scanning position of the first laser beam of the plurality of laser beams which first starts recording. And store.

As described above, acquiring and storing the image data of a plurality of scanning lines in synchronization with the scanning position of one laser beam which finally starts the recording among the plurality of laser beams means that the image data is stored. The capacity of the FIFO that stores data is small. Further, it is not necessary to synchronize the image data of the scanning line that starts recording last among the plurality of laser beams, and a D-type flip-flop (D-ff) can be used instead of the FIFO. If the capacity of the FIFO that stores the image data is small and if D-ff is used instead of the FIFO,
These circuits are used for image processing ICs such as edge smoothing.
It can be provided in a small size and at a low price by reducing the increase in circuit scale.

One feature of the present invention is that, in an image forming apparatus for recording a plurality of scanning lines in parallel by using a plurality of laser beams, a plurality of scanning lines within a predetermined adjacent range are arranged in parallel. In order to perform image processing on the image data for controlling the plurality of laser beams to be recorded, the plurality of laser beams are synchronized with the scanning position of one laser beam which is the last to start recording. The purpose is to acquire image data of scanning lines.

However, in the image forming apparatus using a plurality of laser beams, the angle θ with respect to the main scanning direction is set so that the lights of the two laser beams 311 do not interfere with each other as shown in FIGS. May be placed diagonally to hold. Therefore, the distance (d) in the main scanning direction between the two laser beams changes due to physical factors such as an assembly error and thermal expansion due to individual differences of the image forming apparatus itself, and the synchronization detection signals BD1 and BD2 are generated. Synchronized pixel clock signal VCLK
The phase difference between 1 and VCLK2 may fluctuate. If the phase difference between the pixel clock signals VCLK1 and VCLK2 fluctuates, image data synchronized with the pixel clock signal VCLK1 will be set up between the clock terminal and the input signal when trying to latch it in D-ff or FIFO at the timing of the image clock VCLK2. There are times when the time (t _s) and hold time (t _h) does not satisfy the specification, part of the image data is sometimes disappear.

In order to solve this inconvenience, two lasers are used in order to absorb the phase difference between the image clocks VCLK1 and VCLK2 caused by physical factors such as assembly error due to individual difference of the image forming apparatus itself and thermal expansion. The image data of all the scanning lines acquired in synchronization with the scanning position of the laser beam that finally starts recording in the beam is converted into parallel data by the serial-parallel converter. Next, the image data of all scanning lines converted into parallel data is stored in a register file in synchronization with the scanning position of the laser beam of the two laser beams which starts recording first. Data is converted into serial data by a parallel-serial converter.

Although the serial image data changes every image clock, if the image data is converted into parallel data, the image data can be fixed during the image clock for the number of bits of the parallel data. By sequentially transferring the parallel data to the register file and the parallel-serial converter, even if the phase difference between the image clocks VCLK1 and VCLK2 changes, the data can be surely synchronized without disappearing.

The second feature of the present invention is to convert the image data of a plurality of scanning lines into parallel data.

Another feature of the present invention is that image data of a plurality of scanning lines converted into parallel data having different phases are
It is to synchronize by using two-stage D-ff.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to FIGS.

FIG. 5 is a block diagram of an image forming apparatus using a plurality of laser beams and equipped with an edge smoothing circuit of an image quality improving method using one embodiment of the present invention. Here, the number of laser beams is 2
Book it. The edge smoothing circuit 303 is mounted between the controller 301 and the engine 302,
Pixel clock signals (VCLK1, VCLK2) and pixel clock signals (VC) synchronized with the synchronization detection signals (BD1, BD2) from the engine and the synchronization detection signals (BD1, BD2) from the controller
Image data signal (CVD1, CVD) synchronized with LK1, VCLK2)
2), and outputs the enhanced image data (laser modulation) signals (Vde1, VD2e) to the engine.
The engine controls blinking of two laser beams according to the image data signals VD1e to VD2e to record a plurality of scanning lines in parallel.

FIG. 6 shows the edge smoothing circuit 30.
3 shows a block diagram of FIG. Edge smoothing circuit 303
Is an image data synchronization circuit 351, a FIFO 352, sample windows 353 and 354, and a logic circuit 355.
And 358, and pulse width modulation circuit (PWM) 357 and 3
And 58.

The image data synchronizing circuit 351 receives image data signals (CVD1, CVD2) which are image data of two scanning lines from the controller 301 and temporarily stores image data of a plurality of scanning lines. Image data signal CVD1 of the first scanning line of the two scanning lines
The image data stored in the image data synchronization circuit 351 corresponding to the above is synchronized with the synchronization detection signal BD1 and passed directly to the sample window 353. Image data signal CVD of the scan line that starts the second scan of the two scan lines
The image data corresponding to 2 is temporarily stored in the FIFO 352, synchronized with the synchronization detection signal BD2, and passed to the sample window 354. Sample windows 353 and 354
Passes the pixels to be recorded (reference pixels) and the image data for several pixels around the reference pixels to the logic circuits 355 and 356, respectively. Logic circuits 355 and 35
Reference numeral 6 determines by template matching what part of the image the reference pixel is, and passes the determination results to the PWMs 357 and 358, respectively. PWM 357 and 358
Based on the determination result, if the reference pixel is a part of the edge, appropriate pulse width modulation is applied to generate enhanced image data (laser modulation) signals VD1e and VD2e for recording the reference pixel, respectively. .

FIG. 7 is a timing chart showing the relationship among the synchronization detection signal, the image data signal, and the image clock signal in the image forming apparatus which scans using two laser beams. The two laser beams irradiate the beam detectors respectively, and the synchronization detection signal BD1 of the first laser beam of the two laser beams and the synchronization detection signal BD2 of the second laser beam of which the recording is started. Is generated. An image clock VCLK1 is generated by the image clock generation circuit based on the synchronization detection signal BD1 and an image clock VCLK2 is generated based on the synchronization detection signal BD2. The image data signal CVD1 is synchronized with the image clock VCLK1 and
The image data signal CVD2 is output in synchronization with the image clock VCLK2. The image clock generation circuit uses the sync detection signal BD
Image clock VCLK1 or VC based on 1 or BD2
In order to generate LK2, the image clock VCLK1 or VCLK2 is generated with a delay of ΔT. Since the two laser beams are obliquely arranged with respect to the main scanning direction as shown in FIG. 4, signals generated by the second laser beam (BD2, VC
LK2, CVD2) is generated later than the signals (BD1, VCLK1, CVD1) generated by the first laser beam.

FIG. 8 shows the relationship between the pixel (reference pixel) recorded by the laser beam and the image data for several pixels around the reference pixel. Here, it is assumed that the image processing for edge smoothing uses template matching using a 5 × 5 sample window. Image data of several pixels around the reference pixel 1 centered on the pixel (reference pixel 1) recorded first of the two laser beams, and second recorded of the two laser beams. Part of the image data is shared between the pixel (reference pixel 2) and the image data of several pixels around the reference pixel 2.

Since the image data for several pixels around the reference pixel are partially shared, the edge smoothing image processing is performed by using two laser beams at the scanning position of one of the two laser beams. It is necessary to synchronize the image data of the scan lines. The image data synchronization circuit 351 synchronizes the image data. Reference pixel 1
And the image data of several pixels around the reference pixel 1 are output to the sample window 353 to form the image data of the 5 × 5 sample window 353. Similarly, the image data of the reference pixel 2 and several pixels around the reference pixel 2 are output to the sample window 354 to form the image data of the 5 × 5 sample window 354.

FIG. 12 shows a general serial input / output FIFO.
It is a block diagram of an image data synchronization circuit configured using. The method of synchronizing the image data of the scanning lines adjacent to each other in the sub-scanning direction with the same scanning period for edge smoothing is performed by using the image data signal CVD1 of the scanning line which starts scanning first among the two scanning lines, Acquire and store in the FIFO 401. Next, the image data signal CVD2 of the scanning line that starts scanning second from the two scanning lines is acquired and stored in the FIFO 402. When the image data stored in the FIFO 401 and the FIFO 402 is output in synchronization with the scanning position of the laser beam which starts recording first among the two laser beams, the image data of the two scanning lines becomes two. That is, it is synchronized with the scanning line of the first scanning line which starts scanning. However, since the scanning line that starts scanning second from the two scanning lines starts scanning after the scanning line that starts scanning first, it is possible to read from the FIFO 401 and the FIFO 402 with a delay of one scanning cycle. is necessary.

When the image data of the scanning lines adjacent to each other in the sub-scanning direction are synchronized in the same scanning cycle by this method, the image data of the scanning line of the first scanning line of the two scanning lines is Since the scanning cycle is delayed, the FIFO for storing the image data needs to be able to acquire and store all the image data of the scanning line. Therefore, the number of laser beams is large,
In an image forming apparatus capable of printing two or more sheets of A4 size side by side in the scanning direction, the circuit scale of the FIFO for synchronizing the image data becomes large and expensive.

FIG. 9 is a block diagram of an image data synchronizing circuit using the present invention. The image data of the two scanning lines output from the controller must be synchronized in order to perform edge smoothing, but in the present invention, recording is started last (here, second) of the two laser beams. The image data of the two scanning lines are synchronized with the scanning position of the laser beam. Therefore, the FIFO4 used in FIG.
01 can be replaced with a FIFO 501 having a small capacity. Further, the FIFO 402 is a D-type flip-flop (Df
It can be replaced with the register file 502 configured in f).

Image data signal CVD1 of the scanning line of the laser beam which starts recording first of the two laser beams
Is converted into parallel data by the serial-parallel converter 505 and temporarily stored in the FIFO 501. The image data of the FIFO 501 is output in synchronization with the scanning position of the laser beam of the two laser beams that starts recording last. This means that the output of the FIFO 501 is the sync detection signal BD
2 indicates that it is synchronized with the image clock VCLK2 synchronized with 2. Similarly, the image data signal of the scanning line of the laser beam that starts recording last among the two laser beams
The CVD2 is converted into parallel data by the serial-parallel converter 506 and temporarily stored in the register file 502. The image data of the register file 502 is originally synchronized with the image clock VCLK2. The image data stored in the FIFO 501 and the register file 502 needs to be synchronized again with the scanning position of the first laser beam of the two laser beams to start recording. This means synchronization with the image clock VCLK1 synchronized with the synchronization detection signal BD1. The image data stored in the FIFO 501 and the register file 502 is temporarily stored in the register files 507 and 508 and input to the parallel-serial converters 509 and 510 for synchronization. Since the image data stored in the FIFO 501 and the register file 502 is data converted into parallel data, the data is fixed during the image clock for the number of bits of the parallel data. When the fixed image data is stored in the register files 507 and 508 and the parallel-serial converters 509 and 510 at the same image clock, the image data stored in the FIFO 501 and the register file 502 becomes the image clock VCLK.
Even if the phase with 1 changes, some data is surely stored in the line memory 360 configured by the FIFOs 511 to 514 without disappearing.

FIG. 10 is a block diagram showing the relationship among the image data synchronized by the image data synchronizing circuit according to the present invention, the FIFO 352, and the sample windows 353 and 354. The image data synchronized by the image data synchronization circuit for performing edge smoothing is stored in the line memory 360. The image data stored in this line memory is collectively output to the sample windows 353 and 354 as image data of a reference pixel and several pixels around the reference pixel. Image data signal
The image data of the reference pixel 1 that generates a laser modulation signal in the CVD 1 and several pixels around the reference pixel 1 are output to the sample window 353. Also, image data signal CVD2
The image data of the reference pixel 2 for generating the laser modulation signal and several pixels around the reference pixel 2 are temporarily stored in the FIFO 352 including the FIFOs 531 to 534 and are recorded second in the two laser beams. The laser beam is collectively output to the sample window 354 in synchronization with the scanning position of the laser beam. FIG. 11 shows a timing chart of the image data synchronization circuit 351 using the present invention. In the image forming apparatus using the two laser beams, the engine 302 irradiates the beam detector with the two laser beams to generate the synchronization detection signals BD1 and BD2. The controller 301 inputs the synchronization detection signals BD1 and BD2 from the engine 302, generates the image clocks VCLK1 and VCLK2 and the image data signals CVD1 and CVD2 synchronized with the synchronization detection signals BD1 and BD2, respectively, and sends them to the edge smoothing circuit 303. . Image data synchronization circuit 3 of edge smoothing circuit 303
The serial-parallel converter 505 converts the image data signal CVD1 into parallel data (FIFO-W-Data, here, 8 bits) 51, and stores it in the FIFO 501 when the FIFO-WE signal is “1”. Similarly, the image data signal CVD2 is converted into parallel data (Reg1-Qout, also 8 bits) by the serial / parallel converter 506 and stored in the register file 502 when the FIFO-RE signal is "1". The image data stored in the FIFO 501 is output simultaneously with the register file 502 when the FIFO-RE signal generated based on the synchronization detection signal BD2 is “1”. Image data output from FIFO 501 and register file 502 (FIFO-R-Data, Reg1-Qout)
Are stored in the register files 507 and 508 at the timing of the image clock VCLK1, respectively. Image data stored in register files 507 and 508 (Reg2
-Qout, Reg3-Qout) is converted into serial data (VD1 and VD2) by the serial-parallel converters 509 and 510, respectively, when the FIFO-WE signal generated based on the synchronization detection signal BD1 is "1". Then, it is transferred to the line memory 360 and temporarily stored.

[0035]

According to the present invention, in an image forming apparatus for recording a plurality of scanning lines in parallel by using a plurality of laser beams, image processing such as edge smoothing for smoothing an inclined portion of a contour. It is possible to provide an image data synchronizing means used for the. Further, according to the present invention, the image data synchronizing means can be provided in a small size and at a low price while suppressing an increase in circuit scale.

[Brief description of drawings]

FIG. 1 is a block diagram of a conventional image forming apparatus using one laser beam equipped with an edge smoothing circuit.

FIG. 2 is a block diagram of an edge smoothing circuit mounted on a conventional image forming apparatus using one laser beam.

FIG. 3 is a perspective view showing a configuration of an optical system of an electrophotographic recording type engine.

FIG. 4 is a diagram showing a state where a laser beam emitted from a light source device is applied to a photosensitive drum.

FIG. 5 is a block diagram of an image forming apparatus using a plurality of laser beams equipped with an edge smoothing circuit of an image quality improving method according to an embodiment of the present invention in the image forming apparatus.

FIG. 6 shows a block diagram of an edge smoothing circuit 303.

FIG. 7 is a timing chart showing the relationship among a synchronization detection signal, an image data signal, and an image clock signal in an image forming apparatus that scans using two laser beams.

FIG. 8 is an explanatory diagram showing a relationship between a pixel (reference pixel) recorded by a laser beam and image data of several pixels around the reference pixel.

FIG. 9 is a block diagram of an image data synchronization circuit using the present invention.

FIG. 10 is a FI of an edge smoothing circuit using the present invention.
3 is a block diagram showing an FO 352 and sample windows 353 and 354. FIG.

FIG. 11 is an image data synchronization circuit 351 using the present invention.
2 is a timing chart of.

FIG. 12 is a block diagram of an image data synchronization circuit configured using a FIFO having a large capacity.

[Explanation of symbols]

301 ... Controller, 302 ... Engine, 303 ... Edge smoothing circuit, 351 ... Image data synchronizing circuit, 352 ... FIFO, 353, 354 ... Sample window, 355, 356 ... Logic circuit, 357, 358 ... PW
M, 360 ... Line memory, 501, 511-512,
531 to 534 ... FIFO, 502, 507, 508 ... Register file, 505, 506 ... Serial-parallel converter, 509, 510 ... Parallel-serial converter.

Claims (16)

[Claims] 1. A control circuit for generating a plurality of laser modulation signals for respectively controlling a plurality of laser beams based on image data of the plurality of scanning lines, the plurality of scanning lines being provided by the plurality of laser beams. In the image forming apparatus for recording in parallel, the control circuit acquires and stores image data of a plurality of scanning lines, and one laser beam that starts recording last among the plurality of laser beams. Of the first memory means for outputting in synchronization with the scanning position of the first memory means and the first memory means of the first memory means in synchronization with the scanning position of the first laser beam of the plurality of laser beams for starting the recording. An image forming apparatus comprising: an image data synchronization circuit having a second memory means for acquiring and storing image data to be output. 2. The serial-parallel converter for obtaining the image data of the plurality of scanning lines in the first memory means and converting the image data into parallel data according to the number of scanning lines according to claim 1. A characteristic image forming apparatus. 3. The serial-parallel converter according to claim 2, wherein all the scanning lines of the plurality of scanning lines in the first memory means except one scanning line which finally starts scanning. A first-in-first-out memory for acquiring and storing image data output by the laser beam, and outputting the image data in synchronization with a scanning position of one laser beam that starts recording last among the plurality of laser beams. A characteristic image forming apparatus. 4. The image data output by the serial-parallel converter for one scanning line that finally starts scanning among the plurality of scanning lines in the first memory means according to claim 2. Of the plurality of laser beams, a register file including a flip-flop having a bit number of parallel data to be acquired and stored in synchronization with a scanning position of one laser beam which finally starts recording is provided. A characteristic image forming apparatus. 5. The method according to claim 3, wherein the second memory means synchronizes with a scanning position of one laser beam of the plurality of laser beams for starting recording first. 1. An image forming apparatus comprising a register file constituted by flip-flops having a bit number of parallel data for acquiring and storing image data output from one memory means for the number of scanning lines. 6. The second memory means according to claim 5, wherein the second memory means is synchronized with a scanning position of one laser beam of the plurality of laser beams which first starts recording in the second memory means. The image forming apparatus is provided with parallel-serial converters for acquiring the image data output from the register file for the number of scanning lines and converting the image data to serial data for the number of scanning lines. 7. A control circuit for generating a plurality of laser modulation signals for respectively controlling a plurality of laser beams based on image data of the plurality of scanning lines, the plurality of scanning lines being provided by the plurality of laser beams. In the image forming apparatus for recording in parallel, the control circuit acquires and stores image data of a plurality of scanning lines, and one laser beam that starts recording last among the plurality of laser beams. Of the first memory means for outputting the image data output by the first memory means in synchronism with the scanning position The serial-parallel conversion means for converting the data into parallel data in synchronization with the position, and the image data output by the serial-parallel conversion means are described first in the plurality of laser beams. An image data synchronization circuit having a second memory means for acquiring and storing image data of a plurality of scanning lines in synchronization with a scanning position of one laser beam for starting recording. Image forming apparatus. 8. The image data according to claim 7, wherein image data of all scanning lines of the plurality of scanning lines in the first memory means except one scanning line which finally starts scanning is acquired. An image forming apparatus comprising: a first-in first-out memory for storing, and outputting in synchronization with a scanning position of one laser beam of the plurality of laser beams which finally starts recording. 9. The method according to claim 7, wherein the image data of one scanning line that starts scanning last among the plurality of scanning lines in the first memory means is acquired and stored.
An image forming apparatus comprising a plurality of flip-flops. 10. The serial-parallel means according to claim 7, wherein the serial-parallel means is synchronized with a scanning position of one laser beam of the plurality of laser beams which starts recording first among the plurality of laser beams in the second memory means. An image forming apparatus comprising: a register file including flip-flops having a bit number of parallel data for acquiring and storing output image data, the number of which corresponds to the number of scanning lines. 11. The second memory means according to claim 10, wherein the second memory means is synchronized with a scanning position of one laser beam of the plurality of laser beams which starts recording first among the plurality of laser beams in the second memory means. An image forming apparatus comprising parallel-serial converters for converting the image data output from the register file for the number of scanning lines into serial data for the number of scanning lines. 12. A control circuit for generating a plurality of laser modulation signals for respectively controlling a plurality of laser beams based on image data of the plurality of scanning lines, the plurality of scanning lines being provided by the plurality of laser beams. In the image forming apparatus that records in parallel, the control circuit simultaneously acquires and stores image data of a plurality of pixels of a plurality of scanning lines, and finally starts recording of the plurality of laser beams. First memory means for outputting in synchronism with the scanning position of one laser beam, and the first memory means in synchronism with the scanning position of one laser beam of the plurality of laser beams which first starts recording. And an image data synchronizing circuit having a second memory unit for acquiring and storing image data output from the memory unit. 13. The image data according to claim 12, wherein image data of all the scanning lines of the plurality of scanning lines in the first memory means except one scanning line which finally starts scanning is acquired. An image forming apparatus comprising: a first-in first-out memory for storing, and outputting in synchronization with a scanning position of one laser beam of the plurality of laser beams which finally starts recording. 14. The image data of one scanning line that finally starts scanning among the plurality of scanning lines in the first memory means according to claim 12, among the plurality of laser beams. In the image forming apparatus, a register file including a flip-flop having the number of bits of image data to be acquired and stored in synchronization with the scanning position of one laser beam which finally starts recording is provided. 15. The method according to claim 13 or 14, wherein the first laser beam of the plurality of laser beams in the second memory means is first synchronized with the scanning position of one laser beam to start recording. 1. An image forming apparatus comprising: a register file including flip-flops having the number of bits of image data for storing and acquiring image data output from one memory means, the number of which corresponds to the number of scanning lines. 16. The second memory means according to claim 15, wherein among the plurality of laser beams in the second memory means, the second memory means is synchronized with a scanning position of one laser beam which first starts recording. The image forming apparatus is provided with parallel-serial converters for acquiring the image data output from the register file for the number of scanning lines and converting the image data to serial data for the number of scanning lines.