JPS61269561A - Laser printer - Google Patents

Abstract

PURPOSE:To reduce number of components by providing horizontal synchronization detecting means by a number less than plural electrostatic latent image forming means and detecting a scanning start point of each laser beam of the electrostatic latent image forming means based on a detection signal from the horizontal synchronization detecting means. CONSTITUTION:Laser scanning from a laser scanner unit to a photosensitive body 301 is conducted by using laser beams (a, b) from laser diodes 314, 315. A photodetection element 200 is provided to detect the horizontal synchronization of the beams (a, b). A horizontal synchronizing detection signal S1 of the element 200 is fed to a terminal S of an FF 201 and a Q output of the FF 201 is inputted to a terminal R of a counter 202 as a line start signal S2. An output S3 of an oscillator 203 is inputted to a clock terminal of the counter 202 and an output signal S4 is fed as a video clock. Laser scan is controlled based on the signals S2, S4. Thus, the horizontal synchronization of the beams (a, b) is detected by the element 200 only so as to decrease number of components and to improve the assembling performance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention 1] The present invention relates to a laser printer that prints in multiple colors or in multiple types.

[Technical Background of the Invention and Problems Therewith] This type of laser printer includes an electrostatic latent image forming means that scans a laser beam to form an electrostatic latent image on a photoreceptor; A plurality of sets of developing means for developing the photoreceptor are arranged around the photoreceptor to print in multiple colors or in multiple types.

By the way, in this type of device, since it is necessary to detect the scanning start point for each laser beam of each electrostatic latent image forming means, the laser beam is detected outside the image forming area of the photoreceptor and the horizontal synchronization signal is generated. Horizontal synchronization detection means is provided to output the horizontal synchronization detection means.

In a laser printer that prints in multiple colors and types, a horizontal synchronization detection means is provided for each electrostatic latent image forming means.

However, arranging a plurality of horizontal synchronization detection means in this way not only increases the number of parts, but also requires a great deal of effort and time to adjust the position of each horizontal synchronization detection means.
It is difficult to assemble.

[Object of the Invention] The present invention has been made in view of the above circumstances, and although a plurality of electrostatic latent image forming means are provided around the photoconductor in order to perform multicolor or multitype printing, It is an object of the present invention to provide a laser printer that can reduce the number of parts and improve ease of assembly without disposing synchronization detection means for each electrostatic latent image detection means.

[Summary of the Invention] The summary of the present invention for achieving the above object is to provide a charging means for charging a photoreceptor, and an electrostatic latent image for forming an electrostatic latent image on the photoreceptor by scanning a laser beam. A laser that has an image forming means and a developing means for developing an electrostatic latent image, and performs multicolor or multi-type printing by arranging a plurality of sets of the electrostatic latent image forming means and the developing means around a photoreceptor. In the printer, horizontal synchronization detection means for detecting the scanning start point of the laser beam are arranged in a smaller number than the plurality of electrostatic latent image forming means, and the horizontal synchronization detection means for detecting the scanning start point of the plurality of electrostatic latent image forming means are arranged to detect the scanning start point of each laser beam of the plurality of electrostatic latent image forming means. The present invention is characterized in that the point is detected based on a horizontal synchronization detection signal from the horizontal synchronization detection means.

Examples of the invention] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

This embodiment relates to a two-color laser printer equipped with an automatic document feeder.

FIG. 1 shows the appearance of the apparatus of this embodiment, which includes an automatic document feeder (hereinafter abbreviated as ADF) 1, a scanner unit 110, which will be described later. A printer main body 100 consisting of a laser print unit (hereinafter abbreviated as LBP unit) 300;
It is composed of a control unit 400.

The AI)F 1 is comprised of a document cover 2 incorporating a document conveyance section 30, a document supply section 3, and a document 1-ray 4. The document cover 2 is rotatable in the direction of the arrow shown in the figure by operating the handle portion 2A, so that the document can be placed directly on the exposure glass when the automatic document feed function is not used. . Further, on the top surface of this document cover 2, there is a scanner unit 1 which will be described later.
A liquid crystal display (
5 (hereinafter abbreviated as LCD) and a first operation panel 6 for inputting information for image editing are arranged.

The printer main body 100 includes a second operation panel 101 on the top side for inputting print information, and -
An upper cassette 321 and a lower cassette 322 for feeding paper are removably arranged on one side, and a paper discharge tray 344 is provided on the other side.

In this embodiment, the ADF1. Printer main body 10
0 and the control unit 400 are integrally configured,
Since we do not use a method in which each component is connected as an independent unit using cables, image buses, etc., the installation space for each component is minimized, and side panels etc. can be used in common, making the device lightweight. It is possible to achieve a reduction in cost and cost.

Here, we will discuss the second main control block of the device of this embodiment.
This will be briefly explained with reference to the drawings. In Figure 2, the CPU
Reference numeral 401 controls the laser printer, and this CPU path line includes an LCD interface 407.401 as an interface for the various units. Serial interface 408. A scanner interface 409 and an LBP interface 410 are connected to each other. Further, the LCD interface 407. Scanner interface 409 and LBP
The interface 410 is connected to the first color image data bus line and the second color image data bus line, respectively. Further, a first color page memory 403 and a first color page memory address controller 404 are provided for image processing of the first color image data outputted via the scanner interface 409. For processing, a second color page memory 405, a second color page memo, and a rear address controller 406 are provided. Then, when image editing information is input from the first operation panel 6, the first . The second color page memory address controller 404,406 is connected to the first color page memory address controller 404,406. Second
Reading and writing of image data in color page memories 403 and 405 are controlled to perform various image editing operations.

Next, details of each of the above parts will be explained. 1 First of all,
Details of the ADFI will be explained with reference to FIGS. 3, 4 (A), and (B).

In FIG. 3, the original document supplying section 3 of the ADF1 is composed of a document placing table 10 and a separation feeding section 15. As shown in FIG.

As shown in FIG. 4(A), the document mounting table 10 has document guides 11 and 11 that are movable according to the width of various documents (eg, A5, B5, B4 size, etc.). The document guides 11.11 each have a rack 12.12 inside the document table 10. In addition, the document placement table 1
A pinion 13 is rotatably mounted on the center line l- in the width direction of the document placed on the paper. This pinion 13 is adapted to mesh with both said racks 12.12. Therefore, when one document guide 11 is moved to match the width of the document, the other document guide 11
The document guides 11 also move by the same distance, and both document guides 11 always move symmetrically with respect to the center line 1-.

Further, a bent portion 12A is formed on one side of one of the racks 12 by being bent downward, and the moving path of this bent portion 12A includes various types of movement as shown in FIGS. 4(A) and 4(B). A plurality of switches 14A are provided at positions corresponding to the document width.

A document width detection switch 14 is provided, which is formed by disposing 14B... Then, the plurality of switches 14A,
14F3. From the combination of ON and OFF states of...
The width of the original placed on the original placing table 10 is detected.

The separating and feeding unit 15 sequentially separates and feeds the originals stacked on the original document mounting table 10 one by one. A document presence/absence detection switch 16 is provided in the separating and feeding section 15, which comes into contact with the upper surface of the stacked documents and is displaced according to the number of documents. Further, there are provided a stopper 17 that comes into contact with the lower surface of the document and presses the document upward, and a feed roller 18 that is disposed opposite to the stopper 17 and that frictionally sends out the uppermost layer of the document. The separation feeder 0-519, which is composed of a pair of rollers, separates the plurality of documents fed between the pair of O-rollers and feeds them one by one. The document fed by the separation feeding roller 19 is sent out with the feeding timing controlled by the registration roller 20. In addition, registration roller 20
A document detection switch 21 is provided at the rear stage, and this document detection switch 21 counts the number of documents passing by and detects the quality of the document being passed. Therefore, the document width detection switch 14 and the document detection switch 21 automatically detect the vertical and horizontal sizes of the document.

The document transport section 30 built into the document cover 2 includes:
It is composed of an endless belt that moves over the exposure glass 111 and rollers that drive it, and conveys the original separated and fed from the separation and feeding section 15 along the exposure glass 111 to a predetermined original stopping position. It is. The separating and feeding unit 15 and the document transport unit 30 transport -1 sheets of the document onto the exposure glass 111 for one turn, and after the exposure is completed, the document is transferred in synchronization with the processing timing in the printer main body 100. is ejected and conveyed to the document tray 4, and at the same time, the next document is driven to be conveyed.

Further, on the upper surface of the document cover 2, the LCD 5 and the first operation panel 6 are provided.

By providing the LCD 5, which is an example of a display device that displays images read by the scanner unit 110, it is possible to check whether the image to be copied is accurately read after reading the image and before starting copying the image. can be visually recognized, and unnecessary copying operations can be prevented. Therefore, it is possible to check whether the image is tilted or whether the document reading area (described later) has been specified correctly before copying. It is possible to significantly reduce wasted paper consumption compared to conventional paper. Incidentally, such a display device is not limited to l-CF)5, and various display methods can be adopted. Further, if it is arranged on the upper surface of the document cover 2 as in this embodiment, the operator can easily see the screen of the LCD 5 and confirm the read image. In this way, when disposed on the upper surface of the document cover 2, a flat type disc press is preferable, and in addition to the LCD 5, an LED display, a plasma display, or the like may be adopted.

Next, the scanner unit 110 in the printer main body 100 will be explained with reference to FIGS. 3, 5, and 6. The scanner unit 110 performs exposure scanning on the original on the exposure glass 111 and inputs reflected light from the original into the photoelectric conversion section 120 . That is, as shown in FIG. 3, the exposure light source 112 and the first mirror 113 are attached to the first carriage 116, and the second mirror 114 and the third mirror 115 are attached to the second
It is attached to a carriage 117 and is capable of reciprocating along a guide shaft 118 in the direction of the arrow in the figure. Then, the reflected light from the original that is irradiated by the light source 112 and scanned over the entire exposed area of the original is focused by a lens 119 and enters a CCD (charge coupled device) 121 of a photoelectric conversion unit 120, and is converted into image data. It is set to be converted.

Here, the control block of this scanner unit 110 will be explained with reference to FIG. The scanner unit CPU 130 is in charge of controlling the scanner unit 110, and the program memory 131 connected to its pass line stores the execution procedure in the scanner unit 110. The carriage drive control section 132 drives and controls a stepping motor and the like to drive the first. second carriage 1
16 and 117, and its speed is variable according to the enlargement/reduction mode signal from the scanner CPU 130. This first. Second carriage 116
．． By making the moving speed of the scanner 117 variable, the density in the feeding direction (sub-scanning direction) of the document can be made variable, allowing the image to be enlarged or reduced. The light source control unit 133 drives the exposure light source 112 to emit light throughout the document reading. The ADF control unit 134 drives and controls the ADFI, and also controls the document width detection switch 1.
4 and the output of the document detection switch 21, the document size is transmitted to the CPU 130, which is used to select the document reading area. Furthermore, when no original remains based on the output of the original presence/absence detection switch 16, the scanner operation is terminated.

The binarization processing control unit 135 outputs a timing signal necessary for reading data to the front light distribution electric conversion unit 120,
It also binarizes the digital data of 6 bits per dot output from the charging conversion section 120.

The binarized image data is sent to the scanner interface 409 via the main control unit interface 136, and the first. It will be transmitted to the second color image data bus. The photoelectric conversion unit 120 includes the CCD 121, an amplifier 122 that amplifies the output thereof,
It is comprised of an A/-13=D converter 123 that performs analog-to-digital conversion. Then, the first to third mirrors 113.11 are irradiated with the light m112.
The light reflected by 4.115 enters the CCD 121 through the lens 119, and the charges accumulated in the CCD 121 are amplified by the amplifier 122 and converted into digital data by the A/D converter 123. The output of the A/D converter 123 is, for example, 6 hits/dot. Furthermore, in this photoelectric conversion unit 120, the density in the sub-scanning direction is variable depending on the enlargement and reduction modes;
The speed of the clock corresponding to each driver 1- is constant, and the density in the main scanning direction (corresponding to the width direction of the document) is also constant (for example, 16 lines/jl1m).

Note that enlargement and reduction of the image in the main scanning direction will be described later. Further, main timing signals during a document reading operation in this scanner unit 110 are shown in FIG. In the same figure, rHSYNO,1 is a synchronization signal for each line in the sub-scanning direction, and rl)ATJ represents data, which is binarized during reading with 8 data buses, for example. Data is output in 8-bit units. rsTBOJ is the strobe signal of the above “r)AT”, and rVsYNO
J indicates that the sub-scanning direction is in the document reading area.

Next, the LBP unit 300 will be explained. In FIG. 3, reference numeral 301 is a photoreceptor for recording information with a laser beam, and around this photoreceptor 301, first chargers 302. First developer 303. Second charger 30
4. Second developer 305. A static elimination lamp 306 and a transfer charge v307 to increase the peeling efficiency. A peeling charger 308, a cleaning device 309, etc. are arranged.

Further, 310 is a laser scanner unit for scanning, modulating, and recording two laser beams a and b on the photoreceptor 301. The laser beam a emitted from the laser scanner unit 310 is reflected by a first reflecting mirror 311 and is directed from almost directly above the photoreceptor 301 to the first charger 302 and the first developer 303. The photoreceptor 301'' is irradiated with the photoreceptor 301'' by the first exposure section 350 between the two areas. On the other hand, the laser beam b is
．． The light is reflected by the third reflecting mirrors 312 and 323, and is irradiated onto the photoreceptor 301 at the exposure section 351 of FF12 between the second charger 304 and the second developer 305. There is.

The Ray If scanner unit 310 has a first . Second laser diode 314.315
And this first one. Second laser diode 314.315
The laser beams a and bi emitted from the laser beams are each made into parallel beams] remeter lenses 316 and 317;
A prism 318 that bends at right angles so that the optical path of the laser beam a becomes parallel to the laser beam b, and a polygon mirror 3 that scans the laser beams Aa and b, respectively.
19, and this polygon mirror 319 as shown in FIG.
The f/θ lens 320 is arranged at the rear stage of the lens.

Then, when the laser drive circuit (not shown) operates 4, the first . Turn on the emission of laser beams a and b from the second laser diodes 314 and 315.

OFF and the amount of light are controlled, and these laser beams a and b are transmitted through collimator lenses 316, 317 and prism 3.
18 to one side of the polygon mirror 319,
Here, it is scanned in the main scanning direction. After that, the laser beams a and b pass through the f/θ lens 320 to the first
reflection mirror 311 or the second. Third reflective mirror 312
．． 313 and exposes the surface of the photoreceptor 301 to form an electrostatic latent image. This electrostatic latent image includes the first image. Second
Developers 303 and 305 supply carriers of different colors to develop images (details of this operation will be described later), and the upper cassette 321 or the lower cassette 3
This image is transferred onto paper -F fed from paper 22.

Here, the arrangement of the exposure section with respect to the photoreceptor 301 will be explained. Since the device of this embodiment is a two-color laser printer, there are first and second laser printers in two locations. A second exposure section 350, 351 is provided. Then, there is an inversion θ between the direction of beam incidence on the first exposure section 350 on the photoconductor 301 and the direction of beam incidence on the second exposure section 351 on the photoconductor 301 (see FIG. 3). is at an acute angle. Second
exposure sections 350 and 351 are arranged. The reason for this arrangement is as follows. That is, since various parts must be arranged around the photoreceptor 301 as described above, the first. When the second exposure parts 350 and 351 are placed far apart (when the beam intersection angle θ is an obtuse angle)
, the space for arranging other members becomes narrower. For this reason, it is necessary to increase the drum diameter of the photoreceptor 301 to secure space, resulting in an increase in the size of the apparatus. Therefore, in order to effectively utilize the space around the photoreceptor 301, the arrangement as in this embodiment is preferable. Furthermore, by arranging it in this way, the first. Second developer 303.30
5 can be configured to have substantially the same shape, and costs can be reduced by using common parts. In addition, in order to develop the second color, it is necessary to perform recharging with the second charger 304 after the development with the first developer 303, but this recharging is performed as soon as possible after the first color development. is preferable. Therefore, the arrangement of the exposure section according to this embodiment is advantageous in that recharging can be carried out more efficiently.

Furthermore, since it is necessary to make the optical path lengths of the laser beams a and b the same, the first. By arranging the second exposure sections close to each other, it becomes easy to design such optical path lengths to be the same. Also, the data of the first color is exposed,
When printing second color data in the vicinity of the developed area, it is necessary to wait for the first color data exposed area on the photoreceptor 301 to rotate to the second exposed area, and the time during this period is The deviation Δt is determined by the angle θ and the angular velocity ω[deo/5e
cl, Δ becomes -θ/ω (secl). Therefore, in order to reduce the time difference Δt, it is advantageous to reduce θ.

Next, this first. It is preferable that the second exposure portions 350 and 351 be provided in the upper half circumferential region of the photoreceptor 301, as shown in FIG. 8(A). The reason for this is that the transfer charger 307, which is placed at a position facing the exposure section, can be placed below the photoreceptor 301. In this way, the paper onto which the image is transferred can be transported using its own weight, and the structure of the transport mechanism can be simplified.

If the exposure section is arranged in the upper half of the photoreceptor 301, the transfer jersey 11 etc. will be arranged in the upper half of the photoreceptor 301, and in this case, the paper will not be conveyed while being held between belts, etc. Must be. However, such a configuration is very difficult and also complicated, which is undesirable. Next, by arranging the exposure section in the upper half of the photoreceptor 301, the first reflecting mirror 3
The mirror surface of No. 11 can face downward. Therefore, dust etc. will not adhere to the mirror surface due to its own weight. It is also advantageous in this respect, since dust adhesion to the mirror surface has a great effect on image quality. If the exposure section is arranged in the upper half of the photoconductor 301, the mirror surface of the reflection mirror 352 must face upward as shown in FIG. 8(B). This is not desirable as it becomes complicated.

Next, a paper feeding system and a paper ejection system will be explained with reference to FIG.

The upper set 321 includes an upper paper feed roller 323 for taking out sheets one by one from the cassette, and detects when no paper is left in the cassette. It has an L-stage no-stage switch 324 and a first-F stage cassette size detection switch 325 that detects the paper size of the upper stage cassette 321. Similarly, the lower cassette 322 also has a lower paper feed roller 326. A lower paper out switch 327 and a lower cassette size detection switch 328 are provided. Furthermore, above the upper cassette 321, there is provided a manual feed guide 330 into which paper can be inserted manually, a manual feed switch 331 detects the paper inserted from this manual feed guide 330, and a paper whose insertion is confirmed by this switch is provided. A manual feed roller 332 for conveying the paper is arranged.

This upper cassette 321. Registration rollers 340 are arranged at the forward end of the conveyance path for sheets fed from the lower cassette 322 or the manual feed guide 330. The registration roller 340 synchronizes the image developed on the photoreceptor 301 with the paper, and sends the paper to the transfer charger 307. This transcription charger V-jar 30
The paper on which the image has been transferred in step 7 is discharged forward by the suction belt 341 via the peeling mill charger 308, and further, after the image is fixed by heat and pressure in the fixing device 342, the paper is discharged. The sheet is conveyed to the sheet discharge tray 344 by rollers 343.

Next, the two-color printing operation by LBP 300 will be explained.

The process of the two-color power laser printer is to form a two-color toner image on the photoreceptor 301 during one rotation of the photoreceptor 301 and transfer this to paper (plain paper). That is, the third
As shown in the figure, charging and developing devices are arranged around the J photoconductor 301, and after forming a two-color toner image on the photoconductor 301, the transfer charge t307 transfers two toner images onto the paper.
The color toner images are transferred at once, and the toner images are fixed by a fixing device 342 to complete two-color printing.

On the other hand, untransferred toner on the photoreceptor 301 is collected by a cleaning device @309, and after cleaning the photoreceptor 301, the next print cycle is started.

In this embodiment, in order to obtain a two-color printed image by rotating the position of the photoreceptor 301, a non-contact developing method is adopted. This is because in a contact development method such as the conventional magnetic brush edge method, the first toner image initially formed on the photoreceptor 301 as shown in FIG. 9(A) is like second
9 (C).
) as shown in 1st. The second toner intersects with the photoconductor 3.
Sometimes it adhered to 01. Furthermore, as shown in FIG. 10, the first toner that is transported while adhering to the photoreceptor 301 sometimes gets mixed into the second developing device 305, resulting in a significant deterioration of image quality.

In addition, as a non-contact development method, there is a method that uses a magnetic component developer, but since it contains black magnetic powder, highly saturated color toner is not affected, making it unsuitable for multicolor printing. be.

Therefore, in this embodiment, a two-component developer is used in which an iron powder carrier and a non-magnetic developer are mixed using a magnetic brush. That is, as shown in FIG. 11, a two-component developer 355 is stirred by a mixer 356 and a magnetic brush roll 357 to be triboelectrically charged. Then, the two-component developer 355 is attracted to the magnetic brush roll 357 due to the magnetism of the iron powder carrier and is conveyed by rotation. The two-component developer 355 forming a magnetic brush is regulated to an appropriate layer thickness by a doctor blade 358, and is rubbed against a non-magnetic developing roll 359. By applying a DC bias voltage 360 between the magnetic brush roll 357 and the developing roll 359, only the non-magnetic toner 355A in the two-component developer 355 is electrostatically separated into the developing roll 359. This developing roll 359
The photoreceptor 3 is adjusted by a gap adjustment ring (not shown).
(') Appropriate gap between 1 (e.g. 200 μm)
is held. Also, since the non-magnetic toner 355 Δ is positively charged due to friction with the iron powder carrier, the non-magnetic toner 355 Δ is transported by the developing roller 359.
A is projected onto the electrostatic latent image pattern whose potential is attenuated on the photoreceptor 301, and development is performed. Note that the two-component developer 355 that has been rubbed by the developing roll 359 is scraped off by a scraper 361 and is used for another development. Further, the toner density of the two-component developer 355 is detected by a toner level sensor (not shown), and based on this detection, toner is replenished from a toner hopper (not shown) to maintain a constant toner density. ing.

Next, Figure 12 (A) shows how to prevent color mixing during multicolor printing.
-(D) and FIGS. 13(A)-(D). FIGS. 12(A) to 12(D) are schematic illustrations showing the occurrence of color mixture. The photoreceptor 301 is uniformly charged (Fig. 12 (
A) After performing the first exposure, the surface potential of the exposed area is attenuated to Vs, the first toner is attached thereto, and the first development is performed (as shown in FIG. 12(B)). After that, when the second exposure is performed, this exposed portion is also attenuated to the surface potential Vs (
(Illustrated in FIG. 12(C)). If the second development is performed in this state, the second toner will develop the 1v11 light area in addition to the second exposure area, resulting in a mixed color (as shown in FIG. 12(O)). This development occurs because the potential of the first exposed portion is lower than the development start potential during the second development.

In order to solve this color mixing problem, it is necessary to restore the surface potential of the first favorite part to the surface potential before exposure. At this time, it is necessary to prevent the surface potential of the unexposed area from changing. In order to satisfy these contradictory factors, in this embodiment, a corona discharge charge V that superimposes alternating current and direct current voltages is used as the second charger 304.

Figure 13 shows the color mixing prevention process using this charger (
Explanation will be given with reference to A) to (D).

(1) The photoreceptor 301 is uniformly positively charged with the first charger 302 (see FIG. 13 (A>)).

('2J The 11th light is emitted by the laser beam a from the first laser diode 314, and the surface type 4CI
First toner is attached to the exposed area of V s 1 and first development is performed (see FIG. 13(B)).

(3) Recharging is performed with the second charger 304, and the surface potential of the first exposed area is set to approximately the same potential as the surface potential of the unexposed area.
2 (see Figure 13 (C)).

(4) Second exposure is performed with the laser beam b from the second laser diode 315, second toner is attached to this second exposed area, and second development is performed (see FIG. 13(D)).
. At this time, since the surface potential of the first exposed portion is higher than the development start voltage during the second development, the above-mentioned color mixture does not occur.

Next, details of laser scanning in the laser scanning unit 310 will be explained. FIG. 14 is a schematic perspective view illustrating laser scanning of the photoreceptor 301 from the laser scanner unit 310. It should be noted that each member shown in the same figure is given the same reference numeral as in FIG. 3 or FIG. 7, and detailed explanation thereof will be omitted. In this laser scanning, there are two problems that greatly affect image quality. That is, the laser beam a from the first laser diode 314
The starting point of the scanning amount in the main scanning direction on the photoreceptor 301 is set to 81.
．． The scanning end point is set to Fl, and the second laser diode 31
The starting point of scanning by laser beam b from 4 is 82. If the scanning end point is [2 and J, there is a problem shown in FIG. 15 (A>, (B).
2 are not on the same line and produce a difference d. This is the first. Second laser diode 314.31
This occurs when the laser beams a and b from 5 are not parallel before entering the polygon mirror 319.

On the other hand, FIG. 15(B) shows the first. Second laser beam 31
4.315, the scanning length of laser beams a and b in the main scanning direction is 11. This shows that it is different from Je2. This is the laser beam a after passing through the f/θ lens 320.
, b exist when there is a difference in exposure level until the photoreceptor 301 is exposed.

This embodiment is configured as follows in order to solve the above two problems.

First, the input/output relationship between the LBP unit 300 and the IBP interface 410 is shown in FIG.
This will be explained with reference to FIG. Signals between the LBP unit 300 and the LBP interface 410 are broadly classified into control signals and image-related signals.

As a control signal, the LBP interface 4
There is a command signal such as a print command to the LBP unit 300 from 10, and the LBP unit 300
For the P interface 410, there is a status signal such as a print ready signal indicating the state of this LBP unit.

As shown in FIG. 17, image-related signals from the 1-BP unit 300 to the LBP interface 410 include a video clock signal for the main scanning direction and a horizontal synchronization signal for the sub-scanning direction. are emitted in correspondence with the respective printing areas, and the first . a second video clock signal; a first video clock signal; This is the second horizontal synchronization signal. Further, the LBP interface 410 is connected to the first. a second video clock signal; a first video clock signal; Based on the second horizontal synchronization signal, the first . A second video data signal is output.

As the LRP unit 3000 control system block,
Said 1st. The second video signal and the first . Second
The first horizontal synchronizing signal is generated, and the first horizontal synchronizing signal is generated. It has a print control section 370 (details will be described later) that drives the first and second laser diodes 314 and 315 based on the second video A data signal. This print control section 370 is
It is connected to the I10 port 372 of the microcomputer 371. The microcomputer 371 stores the I10 port 372, which is connected to input/output devices such as various sensors and motors necessary for printing operations, in addition to the print control unit 370, and an operation program for the I-B Pconibutton 300. ROM374 and RAM3 for storing data
75, a timer 376 that generates a clock, and a scanner CPU 373 that controls these parts.

Next, an example of the printing control section 370 will be explained with reference to the block diagram shown in FIG. 18 and the timing chart shown in FIG. 19. FIG. 18 shows that one photodetector 200 detects the scanning start point of the laser beams a and b, and the two laser beams a and b are applied to the photoreceptor 3, which is one of the problems mentioned above.
This circuit corrects the positional deviation of the scan start position 11fEt and E2 toward 01.

In FIG. 18, the photodetecting element 200 detects a laser beam a.
The output horizontal synchronization detection signal S1 is connected to the set terminal of the flip 70 knob 201. Q of this flip-flop 201
The output is a line start signal 82 from the quaternary counter 20.
Input to reset terminal R of No.2. Further, an oscillation output S3 (which is a 1/4 clock corresponding to a 1/4 dot) of an oscillator (O20) 203 is input to the 0 terminal of the quaternary counter 202. The clock signal S4, which is the Q output of the quaternary counter 202, is used as a video clock, and is the same as the horizontal synchronization detection signal 81.
It is synchronized with the oscillation output S3 and is output with an accuracy of one clock (corresponding to one dot) obtained by dividing the frequency of the oscillation output S3 by four.

On the other hand, the line start signal S2, which is the Q output of the flip 70 tube 201, is sent to the counters 204, 205A, 20
Input to reset terminal R of 6A, and also input to quaternary counter 2.
The output of 02 or the D-tuk signal @S4 is the counter 205.
It is designed to be input to the clock terminal Op of B, 206B. The counter 204 is a monostable timer, and the counters 205A and 206A are presettable programmable counters. The output Ss of the counter 204 is a sample timer that is periodically generated in response to the horizontal synchronization detection signal S1 in order to detect the horizontal synchronization position and to generate sample pulses for the optical stability circuit of the laser. It's a signal. In addition, the counter 2
05A is a counter for setting a horizontal left margin, and the counter 206A is a counter for setting a horizontal right margin.

In addition, the output S6 of the counter 205A is output to the inverter 207.
A is input to one input terminal of the AND gate 208A, and the output S7 of the AND gate 206A is input to the AND gate 208A.
It is designed to be input to the other terminal of t-208A. Then, the output S8 of the AND gate 209A, which combines the output of the AND gate 208A and the output S4 of the quaternary counter 202, is outputted to the LBP interface 410 as the first video signal. It has become.

Further, an AND gate 210A is provided which handles the output of the AND gate 208A and the first video data signal by two people. The output of this AND gate 210A,
The output of the OR gate 212A which combines the output S5 of the counter 204 with the signal via the inverter 211 is provided as the loser drive signal S8.

Then, this first loser drive signal S8 is transmitted to the first laser diode 3 via the first loser drive circuit 213A.
14 to emit light.

On the other hand, the drive control system for performing the second pack centering includes the counters 205A, 206A and the inverter 20F shown in FIG.
, the AND gates 208A, 209A, 21OA, the OR gate 212A, and the loser drive circuit 213A have the same configuration with the suffix "A" replaced by the suffix [B[. The counters 205B and 206B are each programmable, and the output S of the counter 205B is
The left margin in the horizontal direction is set by so, and the right margin in the horizontal direction is set by the output S++ of the counter 206B. Also, a second video clock signal 812 and a second video drive signal S+3
, the counter 204 . Signals 86, S of counter 205B and counter 206B
+o, Su.

Note that the counters 205A and 206A, the inverter 207A, and the AND gates 208A and 209A for outputting the first video clock OFF signal S8 are referred to as a first video clock generation circuit 420. Also, the second video link @S
The counters 205B and 206B for outputting 12
, inverter 207B, AND gate 208B, 209
Let B be the second video clock generation circuit 421.

In this way, in this embodiment, two types of laser beams a
, b can be achieved with one photodetector element 200. Conventionally, there are two types of laser beams a,
Since the horizontal synchronization detection of b is performed using two independent photodetecting elements, the number of parts increases and position adjustment of the two photodetecting elements takes time and is complicated. Therefore, according to this embodiment, the cost of the device can be reduced by reducing the number of parts, and the ease of assembly can be improved without requiring complicated adjustment work.

In addition, as shown in FIG. 10(A), laser beams a and b
If a deviation d occurs at the scanning start point S1.82 of the first. This can also be easily corrected by the second video clock generation circuits 420 and 421. That is, by varying the preset 1 value of either the counter 205A that sets the horizontal left margin of the first color laser beam a or the counter 205B that sets the left margin of the second color laser beam b, This deviation d can be eliminated by delaying the scanning start point E1 of the first color laser beam a or by advancing the scanning start point F2 of the second color laser beam a. Therefore, polygon mirror 3
This deviation d can be easily corrected without the need for complicated optical adjustments to make the laser beams a and b into accurate parallel beams before entering the laser beam 19.
correction becomes possible.

Next, the first section regarding the sub-scanning direction. The configuration for outputting the second horizontal synchronization signal SI7.820 will be briefly described with reference to the block diagram shown in FIG. 18 and the timing chart shown in FIG. 20. First horizontal synchronization signal S l? A counter 215A has a configuration that outputs .

216A, inverter 217A, AND gate 218A
, 219A are provided. Similarly, as a configuration for outputting the second horizontal synchronization signal 820, the counter 215F3.2
16B, inverter 217F3. AND GATE 218B
, 219B are provided.

Here, to explain the output of the first horizontal synchronization signal S17, the counters 215A and 216A are programmable counters that can be preset, and the counter 215A and 216A are programmable counters that can be preset.
A sets the top margin, and counter 216A sets the bottom margin. The page top signal 8 S +a is input to the gate terminals G of the counters 215A and 216A, and the line start signal S2, which is the output of the Philips block 201, is input to the clock terminal Cp. The subsequent operation can produce the first horizontal synchronizing signal SIT in the same manner as the production of the first video clock signal S8. The same applies to the creation of the second horizontal synchronization signal S+o.

Next, another configuration example of the printing control circuit 370 that can also correct the mismatch in scanning length shown in FIG. 10(B) will be described with reference to FIGS. 21 to 23. FIG. 21 is a block diagram showing another example of the configuration of the print control circuit 370. The block shown in this figure is different from the block shown in FIG. 18 in that a quaternary counter 220 and a selector 230 are added. It is. Then, the quaternary counter 202
The first clock signal S4 is generated with an accuracy of one clock, whereas the newly added quaternary counter 2 is generated with an accuracy of one clock.
20 is the second clock that is synchronously stretched by 1/4 clock.
The clock signal Sa' is generated, and by using this lock signal, the number of bald clocks is reduced in total, and the beam having a short scanning length is apparently lengthened. The selector 100 is the first. Second clock signal Q
S4.84' is input, and the second clock signal 84' is selected and output for a beam with a short scanning length.

In this embodiment, the scanning length correcting means 242 that corrects the scanning length of the beam in this manner corrects the scanning length of the beam in accordance with the scanning length of the beam. Second clock signal S4. Reference clock generation circuit 234 that outputs Sa' as a reference clock
And, this Mr#ri lock is the first one. It is composed of a selector 230 that selects and outputs to the second video clock generation circuits 240 and 241.

Here, before &! in the scanning length correction means 242. The details of the quaternary counters 202 and 222 and the selector 230 will be explained with reference to FIGS. 22 and 23. In FIG. 22, 221 is a presettable N-ary counter;
The oscillation output S3 of the oscillator 203 is counted after the horizontal synchronization detection signal 81 is output by the photodetection element 220, and the preset value of the N-ary counter 221 can be arbitrarily set by, for example, a dip switch 222 shown in the figure. It is now possible to do so. A shift register 223, a NAND game)-224, a NOR gate 225, and an inverter 226 are gate circuits that provide a predetermined operation to the N-ary counter 221. The oscillation output S3 is inputted to the zero terminal Cp of the shift register 223, and the line start signal 82 is inputted to the reset terminal R, and the Qo and Q1 outputs are inputted to the Nantes gate 224. The Q2 output is the CI of the previous VN counter 221.

Input to CE terminal. In addition, the output of the NOR game 1-224 and the output of the inverter 226 are the same as the NAND gate 225.
The output of this Nant gate 225 is input to the 1-1) terminal of the N-ary counter 221. Incidentally, the inverter 226 is connected to the C of the N-ary counter 221.
Carry is input from the O terminal. Here, as shown in FIG. 23, the line star signal S2 is the reset terminal R of the register 223 and
After inputting the oscillation output S3 to the register 223. When input to the clock terminal Cp of the N-ary counter 221, the NOR gate 2250 output SKI and the Q2 output Szz of the register 221
is input to this N-ary counter 221 as a signal shown in the figure, and a carry output 823 is generated at the Go terminal of this N-ary counter 221. Then, this 4-way output Sza is inverted via the inverter 226 to one J of the JK type flip 70 tube (hereinafter abbreviated as JK-F-F) 227 and 228 that constitutes a quaternary counter.
The terminal is designed to be input to J of K・F-F227. Note that the J terminal of the other JK-F-F 228 is always at a high level. Here, this JK
-F-F227.228 performs a toggle operation at the rising edge of the clock input when both terminals J and J are at high level.
, the previous state is maintained when both terminals are at low level. And this JK-F-F227, 22
Since the line start signal S2 is input to the reset terminal R of JK-F-8, JK-F-F227 and 228 start operating in synchronization with the input of this line start signal S2. The frequency of the oscillation output S3, which is the clock input of F227, is divided by four. and,
When both terminals J and J of the JK-F-F227 are at low level (when a carry of the N-ary counter 221 occurs), the toggle operation is performed for one clock of the oscillation output S3 (corresponding to 1/4 dot). will be interrupted. As a result, as shown in Fig. 23, when the pulse interval during normal operation is set to "1", the output of the JK-toe F228 in the subsequent stage becomes rll/4J when a carry occurs, and is extended by 1/4 clock. It will be.

On the other hand, the counter 202 has two JK-F-F202
A, 202B, its J.

Since the terminal is always at a high level, its Q output is a clock whose frequency is precisely divided by four as shown in FIG.

A selector 230 inputting the outputs of both quaternary counters 202 and 220 is connected to AND gates 231 and 234 inputting the outputs of the quaternary counter 220 and the quaternary counter 2.
It has AND gates 232 and 233 which input the output of 02. The other input of the AND gates 231 and 233 receives a high level when the switch 235 is "open", and receives a low level when the switch 235 is "closed". On the other hand, the other input of the AND gates 232 and 234 receives a low level due to the action of the inverter 236 when the switch 235 is opened, and receives a high level when the switch 235 is closed. It looks like this. Further, an OR gate 237 for inputting the outputs of the AND gates 231 and 232, and an OR gate 238 for inputting the outputs of the AND gates 233 and 234 are provided.

= 42 − Therefore, when the switch 235 is set to “open 1”,
The OR gate 237 outputs the second clock signal j3 S a ' which is the output of the quaternary counter 220, and the OR gate 238 outputs the first clock signal j3 S a ' which is the output of the quaternary counter 202.
The clock signal S4 will be output. In addition, when the switch 235 is set to [closed J], the OR gate 23
7 outputs the first clock signal S4, and the OR gate 238 outputs the second clock signal S4'. If the second clock signal 84' is used as a video clock for a laser beam with a short scanning length by switching the switch 235, the scanning length on the photoreceptor 301 can be increased.

For example, a laser beam 11 whose normal scanning length is 200 m
The correction when one of the two is shortened by one will be explained. When the resolution is 12 lines/M, in order to correct the scan length difference of 1M, the video clock signal of the short scan length beam needs to be stretched by 12 pulses per 2400 pulses (200x12). Here, since the oscillation power S3, which is the clock input of the N-ary counter 221, is a 1/4 hide A clock,
Preset N-ary counter 221 (directly 50 counters 1-
1 ki 1 every time you do it? Just set it to a value that causes leakage. In this way, the difference in scanning length as shown in FIG. 10(B) can be corrected. Note that the preset value of the N-ary counter 221 is the scanning length of the beam.

The scanning length difference can be corrected by setting it appropriately according to the scanning length difference of the 2Bee 11 and the wI image quality.

Next, various image editing functions included in this device will be explained.

First, the above 1. An example of the second operation panel 6.101 will be described with reference to FIG. 24.

the first operation panel 6 for inputting image editing information;
is equipped with various keys as shown in FIG. The composition mode selection key 50 is a key for selecting a mode in which images of a plurality of documents sequentially supplied from the ADF 1 are composited onto one sheet of paper and output. In addition, when ADFI is not used, a mode is selected in which images of originals sequentially placed on the exposure glass 1110 are combined onto one sheet of paper and output. In addition, a first numeric keypad 56 is used as a number of originals input means for inputting the number of originals whose images are to be combined onto one sheet of paper. Incidentally, the reference numeral 57 in the figure is a sheet number display that displays the number of original sheets inputted using the first ten-key pad 56. The image extraction mode selection key 51 is a key selected when extracting not an image of the entire document but a part of the image and copying it onto paper. As a means for specifying the extraction area of the document, for example, a seat 115A provided around the LCD 5 is used to input the coordinates of the extraction area via the first numeric keypad 56. still,
By the above means, it is possible to specify an extraction area for a plurality of originals when the compositing mode is selected, and one
It is also possible to specify division of the extraction area for a sheet of original. The output position specification mode selection key 52 is -F
This key is used to select a mode for specifying the position at which a document image is formed on sheets fed from the stage cassette 321, the lower stage cassette 322, or the like. The coordinates 5A and the first numeric keypad 56 are also used as the image forming device designation means for the paper.

The image erasure mode selection key 53 is a 4-knee key selected when partially erasing an image of a document. In particular, when the compositing mode is selected, it is effective for erasing the outlines of a plurality of documents. Note that the coordinates 5A and the first numeric keypad 56 are used as means for specifying the image erasure area. The framed mode selection key 55 is a key that is selected when adding a new outline after the outline of the document has been erased by selecting the image erasing mode. The pagination mode selection key 55 is a key selected when adding pages to a sheet of paper. In this example, pagination is set to 2 as the mode.
There are several types, one of which is a board that attaches pages in the order in which the originals are input, corresponding to the images of a plurality of originals formed on one sheet of paper during the composition mode. The other mode is a mode in which pages are attached in the order in which paper is output. When selecting the former mode, after pressing the mode selection key 55,
Press the "input order" selection key 55A. When selecting the latter mode, after pressing the pagination mode selection key 55, the "output order" selection key 55B is pressed.

Next, the second operation panel 101 for inputting print information and the like will be explained. In FIG. 24, 150 is a start key for starting a copying operation, and 151 is a second numeric keypad, which is an example of sheet number input means for inputting the number of sheets on which the same original image is to be copied. This second
The number of sheets entered using the numeric keypad 151 is displayed on the sheet number display 1.
52, and a cancel key 153 for canceling the number of sheets is also installed. 154 is a cassette selection key for selecting the -F stage cassette 321;
5 is a cassette selection key for selecting the lower cassette.

Reference numeral 156 is an LCD display that displays various statuses of the printer, and indicates the standby status of the printer.

It is designed to schematically display information such as paper size information, occurrence of jams, toner replenishment, etc.

Further, 157 is an auto magnification mode selection key, and when this key is pressed, the original image is automatically enlarged or reduced based on the size of the original image and paper. Reference numeral 158 is a magnification specifying key, and by selecting a numerical value with the second numeric keypad 151 after pressing this key, a desired enlargement or reduction magnification can be set. Reference numeral 159 is a key for selecting a reduction or enlargement mode in accordance with a predetermined vRm size and paper size.

Next, a page memory address controller 0- that performs various image editing operations based on input information to the first operation panel 6 will be explained. In this embodiment, the first color is used to form two-color images.

2nd color page memory address controller 404°40
6, both of which have the same configuration. FIG. 25 is a block diagram showing an example of the first color image memory address controller 404.

This page memory address controller 0-controller controls the page memory address and read signal/write signal υII.
[This is what I do.]

First, page memory address control will be explained.

The page memory address controller shown in this example is as follows:
This is provided to use page memory more efficiently. The address of the page memory is usually determined by applying a read/write signal as a count in the main scanning direction and a horizontal synchronization signal (H8YNC) signal as a count in the sub-scanning direction. by the way,
When specifying page memory addresses using IIJIII, a good number of divisions in the main and sub-scanning directions of the page memory is 1024.2048, 4096.819.
2. ...and is a multiple of 2. However, the number of main scanning directions actually used is close to the above number (rarely), and in the case of this device, the main scanning width is approximately 5000 bits (approximately 62
5 bytes), and the sub-scanning width is approximately 7000 (approximately 875 bytes).
part-time job).

Therefore, to satisfy this address space, 8192X
An address space of 8192 bits (1024 bytes x 1024 bytes) is required, and both the memory element and the counter element are wasted.

The device of this embodiment is
(TP> An address control block consisting of a register 423, an adjustment sieve 424, a latch circuit 425, an address counter 426, and an address transceiver 427 is provided. It is a corresponding value, and the CPU
401 determines this xW and transmits the xW via the CPU bus, data transceiver 420 and
(Set TP>register 423. Also, set the read/write start address (TP) in the same way as XW
When set in the (TP) register 423, the number TP+XWxN (N is an integer) is accessed by the above address control block inputting the H8YNC signal, and the start address in the main scanning direction is accessed. There is. Also, read signal (PRI) C from the image bus
) or write signal (PWTC) to clock receiver 4.
40 to the line I control/return clock generator 437, a write/read clock synchronized with the read signal and write signal is generated, and the addresses in the main scanning direction are sequentially updated by this clock. It has become. By specifying addresses in this manner, the addresses become continuous one-dimensional numbers with almost no spaces, and the number of memory elements and counter elements can be kept to a minimum. Incidentally, when a composition mode in which a plurality of original images are formed on one sheet of paper is selected, a start address (TP) may be set at a predetermined position according to each original.

Next, a pro-game controller that controls partially reading or partially rewriting data in a page memory will be described. For this purpose, the XN register 430. XN counter 431. YN register 432 and YN counter 43
3 is provided.

XN and YN are values in the main scanning direction and sub-scanning direction that specify areas on the image memory, respectively, and these values are
01 via the command boat 421
N register 430. It is set in the YN register 432. These XN and YN values are set in the XN and YN counters 431 and 433 that count the read/write clock, and after the XN counter 431 counts the read/write clock by XN, it outputs a carry and carries out a carry in the sub-scanning direction. conduct. And XN, YN counter 431
．． When both the main 11 keys are output from 433, it means that the access range specification has been completed. At this time, based on the output of the line control/clock generator 437, the status transceiver 439 sends a
F' ND ) is output to the image bus, and all data in the access range is cleared.

In this embodiment, it is possible not only to erase specific data in the page memory, but also to write specific data. At this time, after setting TP, XN, and YN to specify the data writing position in the same manner as above,
DMA (Direct Memory Access) shown in the figure
] Write the data address and data length where the data to be written to the controller 41 is stored.
By enabling the DMA operation, this data is written onto the page memory. Note that the data to be old is stored in the program memory 40.
It is stored in 2.

In this case, the data may be a character, a symbol, or a specific pattern, such as a page code or an outline of a document.

Mask register 434. The mask counter 435 is used to invalidate a certain range of image data in the page memory, and when an address corresponding to a predetermined range is set in the mask register 434, the data in that range is forced to zero. It has become so.

Address register 436 is provided to allow CPU 401 to specify the address currently being accessed by this page memory address controller, and this address is used by data transceiver 420 . CPU
The data is transferred to the cPL 401 via the bus.

Note that the line control receiver 438 receives a line synchronization signal (NX
LIN), the bus control receiver 441 inputs a data high enable signal (1') LIENB) and an image disable signal (IMDIs) and transfers them to the line control/link generator 437. It is something.

Next, the page memory as an image memory will be explained. The first color and second color page memories 403 and 405 have a configuration as shown in FIG. 26. This page memory 403 is connected to the page memory 1 controller 404.
According to the address signal output from the J, data of 1 or 2M pie 1- can be stored. As for the memory element, the dynamic RAM of 256 bits is 6
It uses 4 pieces and has a memory space of 1~2M pie.

The bus commonly used is the image bus, which is the page memory address controller 404 . /106. Print control section 37
Image data controlled by each control signal such as 0 is transferred from this image bus to the data buffer 403A.
It is designed to be read/written via. Further, only in the above-mentioned I''MA mode (a mode for writing page codes or the outline of a document, etc.), data is inserted from the CPU bus via the data batts 7403B.

Next, the configuration of the scanner interface 409 will be explained with reference to FIGS. 28 to 30.

This Suki1Sina interface 409 is CP I
Control signal from J401 to scanner unit 1
10, the status of the scanner unit 110 to the CPU 401 side, and the role of reducing and enlarging the read image data and transmitting it to the page memories 403 and 405. That is, as shown in FIG.
The address signal is converted from the PU bus to the address code converter 45.
0, input the data to the bus transceiver 458, and input various data according to the address to the basic command register 452. The status data of the scanner unit 110 written to either the command register 453 or the status bus receiver 454 or the m status receiver 455 is transferred to the bus 1 transceiver 458 . CP LJ 4 via CPLI bus
01. In this way, you can send commands to scanners 1 to 110, and
The state of the scanner unit 110 is read in 401. Also, this scanner interface 4
Among the interface signals between 09 and the scanner unit 110, data (IDAT) input/output via the path transceiver 7I57 has a bus structure, and the status signal (IsDAT) transmitted from the timing generator 451 to the scanner unit 110 has a bus structure. A T ) Et (F
17', i signal (,1(':Mr),) (7)
2) (7) It has three states depending on the signal state. That is,
It has three states: status data of the scanner unit 110, command data to the scanner 1-11-0, and image data read by the scanner 1-110. Also, the timing of sending and receiving these various data is determined by the busy signal (I) output from the unit 110.
SBSY) and the timing generating section 451J, the roll signal (IWR) W is used to perform rolls from 1 to 1. In addition, interrupt F/F459 is CP LJ
It outputs an interrupt signal @ (INTO) to 401.

The image data from the scanner unit 110 input via the path transceiver 457 is processed by the image processing section 45.
6 and enlarge the image here.

The image is subjected to reduction (processing related to the main scanning direction) and trimming (image extraction), and then sent to the image bus.

Details of this image processing section 456 will be explained with reference to FIG. 29. This image processing section 456 has two line memories 46
0,461, and these two line memories 460.4
The image is enlarged or reduced by alternately reading and writing to and from 61. Note that since it is necessary to read and write image data as serial data to and from the line memories 460 and 461, the image data that is input in parallel is processed by a parallel-to-serial converter (hereinafter referred to as a P-8 converter) 462. The image data read out from the line memories 460 and 461 is converted into serial data and converted into serial-to-parallel data (hereinafter referred to as an 8-P converter) 46.
3 to output to the converter image bus in parallel.

Then, address signals and write/read timing signals for reading and writing into the line memories 460 and 461, and the P-8 converter 462. Various blocks are provided to output timing signals for setting the conversion timing of the S-P converter 463.The write timing generation circuit 464 and the read timing generation circuit 465 output the timing signals that set the conversion timing of the S-P converter 463. It outputs two types of clocks: 8 clocks corresponding to the image data of 8 pixels 1~ and a clock obtained by extending these clocks.Then, these clocks are sent to the P-8 converter 462.S-P converter. vessel 46
3 timing signal, and timing selector 4.
It is used as the write/read timing signal via the signal line 67, and is further used for generating an address signal.

The blocks that generate the address signal include a line memory address counter parameter register 46B, a decimal run, and a register 469. Decimal address counter integer part 4
70. An integer address counter 471 and two address selectors 472, 473 are provided. The line memory address counter parameter register 468 sets the enlargement or reduction magnification to be counted for the decimal counter section 469, and sets initial values for the decimal address counter integer section 470 and the integer address counter 471. It looks like this. Decimal counter section 46
9 adds the enlargement and reduction magnifications for each clock and outputs a carry of the sum of the decimal parts. For example, in the case of 0.7 times, a carry is output up to the third clock, but no carry is output at the fourth clock. (0,7X
3=2.1.0.7X4=2.8, so there is no decimal carry). The decimal address counter integer section 470 is configured to advance the count only when a carry occurs in the decimal address counter section 469.

On the other hand, the integer address counter 471 is configured to advance the count every clock.

When data is reduced, the output of the decimal address counter integer section 470 is used as an address to store the line memory 472.
Alternatively, by writing data to 473, data is written with one missing piece of data at a time, and the read address is determined by the integer address counter 471 to generate reduced data. On the other hand, when expanding data, the integer address counter 471 writes the data as it is to the line memory 471 or 473, and the read address is determined by the decimal address counter integer part 470, so that the same data is read out one by one in succession. Enlarged data is now created. For this purpose, the decimal address counter integer part 470. Address selector 4 inputs the outputs of the integer address counters 471 and selects and outputs them to the line memories 460° 461
72.473 is provided. Note that the selection of addresses with this address selector 472 and 473 is expanded.

This is done based on the output of the reduction timing controller 474.

Here, the data reduction and expansion operations are shown in Figure 30 (A) and (
This will be explained with reference to the timing chart shown in B). FIG. 30(A) is a timing chart showing the data writing operation to the line memories 460 and 461.
Figure (B) is a timing chart showing the data read operation from the line memories 460 and 461. Data D
O8 to DO1 are made into serial data by the clock CP from the write timing generation section 464. Further, the decimal counter section 469 outputs a carry from the rise of the 0 clock CP, and has a reduction magnification such that a carry is not output at, for example, the seventh clock.

Therefore, the decimal address counter integer section 470 sequentially updates the write address only while a carry is output from the decimal counter section 469, but when the carry is not output, it does not update the write address and the data DO2 , the common address ADS for DO1
+6 will be specified. Therefore, the same address data D is stored in the line memory L.

2. As a result of continuous writing of DOl, data DO2
will be erased and data will be lost. Since this data is read out using the address of the integer address counter 471, which is updated in accordance with the Otsuk C port, as shown in FIG. Missing reduced data will be generated.

When expanding data, the integer address counter 47 is updated in response to the clock CP as shown in FIG. 30(A).
Writing to line memory 460 or 461 is performed by address 1. Therefore, data DO8 to DO1 are directly written into the line memory. Then, data is read from this line memory based on the address of the decimal address counter integer section 470.

For example, as shown in FIG. 30(B), the decimal count section 4
If 69 is the sixth clock CP and the magnification is such that no carry is output, the decimal address counter integer part 470 rotates the same address (ADS+5) twice without updating the address while this carry is not output. They are specified consecutively, and as a result, the same data is read out continuously and the data is enlarged.

In addition, the above enlargement and reduction operations will enlarge the image in the main operation direction.
In this case, the image in the sub-operation direction is enlarged or reduced by changing the scanning speed of the carriages 116 and 117, as described above. Also, when in the same-size mode, the same-size mode signal is input to the decimal count section 469, and the decimal address counter integer section 470 outputs the same address as the integer address counter 471, resulting in enlargement.

No reduction is performed.

Next, image extraction (
trimming). This trimming is performed by extracting data in the image extraction area by defining a data start position and a data end position. To set the starting position of data, connect the highest bit I~ of each write and read address to the chip select terminal of the memory element, and after that bit becomes 1, it will turn white and read will be possible. Set it up and do it. Setting the end position of data is an address.Next, image extraction (trimming) in this image data processing section 456 will be explained. This trimming is performed by extracting data in the image extraction area by defining a data start position and a data end position. To set the starting position of data, connect the most significant bit of each write and read address to the chip select terminal of the memory element, and set it so that writing and reading are possible after that bit becomes 1. conduct. The end position of the data is set by setting an address in the address comparator 475, and by this address comparator 475, a gate 476 provided after the P-8 converter 462 or a gate 476 provided before the S-P converter 463 is set. This is done by controlling the installed data selector 478. Note that this address comparator 475 operates by inputting the address of the integer address counter 471. Therefore, when the image reduction mode and cropping are performed together, the integer address counter 471 is used when reading data, so the data selector 478 that selects the read data is controlled by the address comparator 475. will be done.

On the other hand, when the image enlargement mode and cropping are performed together, the integer address counter 471 is used when data is written, so the gate 476 that selects the data to be written in advance is the address comparator 47.
5.

The above trimming operation is performed in the main scanning direction, and 1 to rimming in the sub-scanning direction is performed as follows. That is, sub-scanning direction parameter register 480, address counter 481 . Address comparator 482 and gate 48
3 is provided.

This configuration corresponds to the above-mentioned trimming block in the main scanning direction. The most significant bit of the address counter 481 is connected to the gate 483 for the horizontal synchronization signal (MH8YN) and slope signal (MSTB), and if this bit does not become 1, both signals are output to the image memory. It is designed so that it will not happen. This restricts the starting position of data in different scanning directions.

The end position of the data in the sub-scanning direction is determined by setting a value corresponding to the end position of the data in the address comparator 482. and address counter 482
When 12 or more addresses are counted by the address comparator 482, the data selector 478
control to force the data to zero. As a result, zero data is written to the page memory, and truncation in the sub-scanning direction is performed.

Next, regarding the LRP interface 410, a third
This will be explained with reference to FIG. This LBP interface 410 outputs a control signal from the CPU 401 to an L level.
In addition to informing the B P 300, the status of the L B P 300 is also transmitted to the CPU 410, and the page memory 401.4
It plays the role of transmitting the image data of 05 to the LBP 300. That is, an address signal is input from the CPU bus through the address receiver 485 and address decoder 486, data on the CPU bus or data from the LRP 300 is taken into each register according to this address signal, and the contents of each register are read by the CPU 401. to send commands to LBP300,
Read the status of 00. For each register,
Printer command register 490, printer status register 491. -] A cloak register 492 and a status register 493 are provided. Data on the CPU bus is also input via a data transceiver 487, and a print request signal (PREQ) from the LBP 300.

The print ready signal (PRI) Y) etc. are sent to the receiver 489.
The print signal (PRT) and the like are output to the LBP 300 via the driver 495. In addition, this LBP interface 41
The data DAT8 to DAT1 exchanged between the transceiver 488 and the L Rl) 300 have a bus structure, and the status signals (D S, lΔ
), 1 cloak signal (1') COM), and has three states depending on the states of the two signals.・That is, 1. Rr) 300 status signals.

It has three states: a command signal to LBP'300 and an image signal to l-13P300. The timing control circuit 499, which determines one of these three states, receives the read/write signal from the bus interface 494, the command information from the command register 492, the transceiver 498, and the receiver 489.
Each second signal is output to the L 11 P 300 based on the synchronization signal etc. from the L 11 P 300 . Further, the image signal from the image bus is sent to the data receiver 496. LBP300 via data latch circuit 497 and bus transceiver 488
It is now possible to convey the information to

Next, various image editing operations performed by the apparatus of this embodiment will be explained.

<Image Composition Mode> First, an image composition mode in which a plurality of original images are composited and formed on one sheet F will be described with reference to FIG. 32. This mode is selected by pressing the composition mode selection key 50 on the first operation panel 6. When this key 50 is pressed, a plurality of documents are successively read by the scana unit 110 and sent to the photoelectric conversion unit 120.
is converted into a digital signal. When using ADFI, multiple originals are automatically fed one by one and read one by one. When not using ADFI, the original cover 2 is opened and closed for each original and the exposure glass 111 is read. A document is manually placed on top of the scanner, and each document is read one by one.

For example, the manuscripts Pz, P2 . P3, P
4 images are read one by one in the above manner. The image read in this way is transferred onto the image bus via the scanner interface 409, and in the case of monochrome copying, it is stored in the image memory under address control of the first color page memory address controller 404, which is a one-inclusive control means. It is written to the first color page memory 403. At this time, the first color page memory address controller 404
sets the top addresses TI)1 to TP4 of the image memory 4030 as shown in FIG. 32 according to each original image, and writes each image to a different address of the image memory 403.1-. Then, the contents of this image memory 403 are L
It is transferred to the print control unit 370 of the LBP controller 300 via the BP interface 410, and drives the first laser diode 314 to emit light to form an electrostatic latent image of the composite image on the photoreceptor 301. After that, the above-mentioned L R
Based on the operation of the P controller 300, four original images are formed on one sheet T as shown in FIG. Such a composition mode allows a plurality of original images to be formed on one sheet of paper in a single image forming operation, shortening copying processing time and reducing paper consumption. Note that images can be synthesized by placing multiple originals on the exposure glass 111 at once if the ADF1 is not biased, but if two or more originals cannot be placed at once, For example, this compositing mode is convenient when composing a plurality of A3'J size originals. In addition, when this composition mode is selected using the ADFI, the composition operation is performed for each document of multiple valves that are sequentially and continuously fed from the ADFI, and the document presence detection switch 16 detects that there is no document. The above-mentioned operations can be performed continuously until the machine reaches its final stage, which greatly reduces the burden on the operator.

Also, when such a composition mode is selected, it is convenient to reduce the size of multiple original images and form them on a single sheet of paper. Therefore, press the auto magnification mode selection key 1.
By using the 579 magnification designation key 158 or the magnification selection key 159, the original image can be reduced and inserted into the image memory 403 to form a composite image on a sheet of a predetermined size. Regarding image reduction, as described above, data in the main scanning direction is reduced by the image processing unit 456 of the scanner interface 409, and data in the secondary and scanning directions is reduced by varying the scanning speed of the carriages 116 and 117. .

<Image compositing mode 10/Variable number of manuscripts to be synthesized> Although the image compositing mode described above can be performed by fixing the number of manuscripts to be composited in the apparatus, it is more practical to make the number of manuscripts to be composited variable. In this embodiment, the composition mode selection key 50
When pressed, the first numeric keypad 5 as a means for inputting the number of original sheets is pressed.
By operating 6, the number of originals to be combined can be set as desired. Then, the plurality of originals specified by the first numeric keypad 56 are sequentially read and formed into one sheet of paper. Note that the first color page memory address controller 404, which is a write control means, sets the top address TP according to the specified number of originals, and stores the plurality of original images in the image memory 4.
The output and output will be specified to different addresses of 03.

<Image compositing mode - number of composite originals, variable number of output sheets> It would be more practical if the image forming operation of composing a predetermined number of originals onto one sheet of paper could be performed continuously on a plurality of output sheets. In the device of this embodiment, the second operation panel 10
1, there is a second numeric keypad 15 which is a means for inputting the number of output sheets.
1), and the number of sheets of paper to form and output a composite image is variable.

Note that the laser scanner unit 310 has an image memory 40.
3, latent images are continuously formed on a specified number of sheets for each rotation of the photoreceptor 301, and the latent images are fed from the first cassette 321 or the lower cassette 322. Copying operations are performed continuously on sheets of paper. Therefore, each document only needs to be read once.

<Image extraction area specification and image formation position specification> For example, the third
Extract the effective image D1 of the original P shown in Figure 3 and print it on the output paper T.
The operation for forming the image D2 by reducing it at a predetermined position with a magnification M will be described. The extracted image D1 of the original P is -
Corner coordinate position X1. Yl and image size A1. It is specified by Bt. Further, the image forming position of the image D2 on the output paper T is specified by the coordinates X2 and Y2 of one corner of the image P2. Therefore, as an example for specifying the above coordinates and size, for example, the information shown in FIG. 34 is displayed on the LCD 5,
It is possible to request input of numerical values corresponding to each piece of information using the cursor 5B. That is, when the first operation panel 6, the image extraction mode selection key 51, and the output position specification mode selection key 52 are selected, the above 1-C is selected under the control of the CPU 401.

5, the above display is performed. Then, by inputting information corresponding to the position of the cursor 5B via the first numeric keypad 56, the image extraction area and the image forming position can be specified. ” - Once the image extraction area is specified as described above, the scanned image is transferred to the scanner interface 4.
In the image data processing unit 456 of 09, the above-described reduction operation and trimming operation are performed together. Further, when the image forming position is specified, the image memory address controller 404, which is a write control means,
P is set to a predetermined value and written to the address of the image memory 403 corresponding to the designated image forming position. After this,
By executing an image forming operation based on the contents of the image memory 403, an image iD2 as shown in FIG. 33 can be formed on the paper T.

<Image synthesis mode + image formation position specification> In this example,
The above-mentioned designation of the image forming position can also be performed in the image composition mode.

That is, as shown in FIG. 35, the originals P1 are sequentially read.
It is possible to designate the image forming position for each of the images from P4 to rearrange the images and form them on the paper T. On this occasion,
After pressing the composition mode selection key 50, the first numeric keypad 56
Operate to set the number of originals to be combined. After that, when the image forming position designation mode selection key 52 is pressed, the third
The screen shown in FIG. 4 is displayed on the LCD 5. Note that when the image extraction mode selection key 51 is not selected, information regarding rREADJ is not displayed in FIG. 34.

Then, according to this display, the first ten-1=-56
to set the image forming position coordinates X2 for each document P1 to P4.
, Y2 may be specified. With such a designation, the page memory address controller 4, which is a write control means,
04 determines the top address of each original image in the image memory 40 according to the respective coordinates X2°Y2. As a result, as shown in FIG. 35, each image can be synthesized and formed at a position on the paper T that is different from the order in which the originals were input.

<Designation of extraction area division for a single document image> When a single document P has multiple images as shown in FIG. This is a mode of extraction and formation. At this time, press the image extraction mode selection key 51 to select r R as shown in FIG.
Display E A D J on L CDb, coordinate X1
．． Yl and size Al.

B1 is input via the first numeric keypad 56 to designate the extraction area of the image rAJ in the document P. Thereafter, for example, the image extraction mode selection key 51 is pressed again to sequentially designate the extraction areas of images rBJ and rcJ in the document P in the same manner. When division is specified in this way, the CPLI 401 transfers the scanner unit 110 to the scanner interface 40.
9, and images of the same original P are successively read by the number of divisions. Then, the page memory address controller 404, which is a write control means, trims the image according to the order specified for division for each reading operation, and writes the extracted image into the memory 403. Furthermore, the LBP unit 300 sequentially performs an image forming operation on different sheets of paper based on the contents in the image memory 403, thereby producing an extracted image [A] as shown in FIG.

rBJ and rcJ are different papers Tt and T2, respectively.
.

It can be formed on Ta. In addition to such division designation, it is also possible to designate an image forming position and/or select a reduction or enlargement mode.

<Auto magnification mode> Next, a mode in which the copy magnification of an image is automatically set based on the operation of the auto magnification mode selection key 157 provided on the second operation panel 101 will be described.

In order to automatically set the copy magnification, it is necessary to detect at least the size of the original image and the size of the output paper in advance. When using ADFl, the document width detection switch 14 and document switch 21 detect the vertical and horizontal sizes of the document. Further, when the image extraction mode is selected, the size AI of the image extraction area shown in FIG.

81 Can be detected by human power. On the other hand, the size of the output paper is detected by an upper cassette size detection switch 325 or a lower cassette size detection switch 328, which determines the types of the upper and lower cassettes 321 and 322 and detects the paper size. The CPLI 401 can detect the size of the original and output paper in advance by inputting this size information via the CPU bus. Then, when the auto magnification mode selection key 157 is pressed,
The CPU 401 can calculate the copy magnification from the size information. Then, the CPU 401 controls the scanning speed of the carriages 116 and 117 in the scanner unit 110 via the scanner interface 409 based on the copying magnification, and performs an enlargement or reduction operation in the sub-scanning direction.

Further, information on the copying magnification is sent to the image data processing unit 456 of the scanner interface 409 to perform enlargement and reduction operations in the main scanning direction. In this way, an image forming operation based on the auto magnification mode is performed. Further, such auto magnification mode can also be performed in conjunction with the above-mentioned combination mode. In the composite mode, the copy magnification is automatically set for each document to be composited.

<Composite Mode Expert Original Contour Erase Mode> When forming multiple original images on one sheet of paper, the outlines of each original may be formed on the paper, resulting in an unattractive copy. . In the device of this embodiment, after pressing the image deletion mode selection key 53, the first numeric keypad 56
By specifying the contour area, the image data of this area can be forced to zero on the image memory 403. For example, as shown in FIG. 37, the outline areas of the document ■, ■
.

When erasing ■, ■, write 1, l shown in FIG.
J Gohei means page memory rate controller 4
The CPU 401 sends XN1.04 to the command boat 421. XN2. YNl, YN2 and top address TP
t~TP4, each register 423, 430.432
Set sequentially.

When all data in area (2) is to be cleared, TPt is written to each of the registers 423, 430, and 432.

XN1. The operation is started by setting YNI respectively and setting the all clear command assigned to a specific hit of the command boat 421 to [1]. The page memory address controller 404 first sends TPz to the image bus via the address transceiver 427.
It outputs the address of the image memory 403, and simultaneously sets the signal of the image bus to 1, which invalidates the data bus, and further outputs a read-in signal to the image memory 403. next,
A write signal is output while sequentially updating the address from the address transceiver 427, and this operation is performed XN times,
When repeated, the XN counter 431 outputs a carry. Then, the YN counter 433 is updated by one and the address is set to the value TPz +XW. The above operation is performed until the YN counter 433 counts YNI times, and when this value is counted, a carry is output from the YN counter 433, and the all clear operation of the area (2) is completed. The same applies to areas ■～■ 80
Uniformly TP2 to TPa, XN1, XN2. YNl.

This can be done by setting YN2. Furthermore, in the case of composite mode, the outline area of each document is
, YN, the outline of each document can be erased on the image memory 403.

<Contour Writing Mode> After erasing the outlines of the originals to be combined as described above, it is possible to newly write the outlines of each original on the image memory 403. At this time, the image deletion mode selection key 53. After specifying the contour area to be erased with the first key 56, the mode selection key 54 is pressed to select a frame as the contour insertion mode selection means. Then, following the above-described erase operation of the contour area, a new contour line is written in this area, that is, the writing position of the contour line is
01 to each register via the command boat 421.
Set P, XN, YN, and the CPU 401 is the 26th
The data address and data length where the data to be written are stored are programmed into the DMAI controller 411 shown in the figure, and the DMA operation is enabled. DM
A controller 411 uses designated image memory 403]
The frame will be set by automatically accessing the address and writing "1" in the corresponding address on the outline.

Page numbering mode> The above-described DMA controller 411 is capable of writing various data onto the image memory, and is not limited to only the outline of the document. For example, page numbers may be attached to the output paper. Numbers as page codes are stored, for example, in a lower memory of the program memory 402, and the DMA controller 411 can read this page code information from the program memory 402 and write it onto the image memory 403. There are two types of page code writing modes.

First, by pressing the page mode selection key 55 and the [input order-1 selection key 55A] on the first operation panel 6, each document in the composition mode is selected as shown in FIG. This is a mode in which a page code is attached to the position corresponding to the image forming area. The other mode is a mode in which page numbers are attached to the sheets in the output order as shown in FIG. 39 by pressing the page addition mode selection key 55 and the [Output order, 1 selection key 55B].

In the former "input order" mode, the CPU 401 can detect each top address TPI to TP4 and the size XN, YN of the page code forming area shown in FIG. Each data is stored in each register 423 of the page memory address controller 404,
430 and 432 via the command port 421, and thereafter each page code can be written onto the image memory 403 by the DMA controller 411.

Even in the latter "output order" mode, the top address TP and size X of the page code formation area are determined from the output paper size.
N, YN can be detected, these data can be set in each register 423, 430, and 432 via the command boat 421, and page codes can be assigned in the output order by the operation of the 11MA controller 411.

Note that the above-mentioned "input order" mode and "output order" mode can be used together, and furthermore, the image forming position designation mode, trimming, enlargement, and reduction mode can also be used together.

Note that the present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the paper of the present invention.

[Effects of the Invention] - As explained above, in the present invention, although a plurality of electrostatic latent image forming means are disposed around the photoreceptor in order to perform multicolor or multitype printing, the plurality of electrostatic latent image forming means are Since a common horizontal synchronization detection means is arranged for the image forming means,
It is possible to reduce the number of parts, and furthermore, assemblability is improved without requiring complicated work for adjusting the positions of a plurality of horizontal synchronization detection means as in the prior art.

[Brief explanation of drawings]

FIG. 1 is an external perspective view of an apparatus according to an embodiment of the present invention, FIG. 2 is a main control block diagram of the apparatus according to the embodiment, FIG. 3 is a schematic cross-sectional view of the apparatus according to the embodiment, and FIG. 4 (A). (B) is a partially cutaway plan view and a schematic sectional view of the document mounting table, FIG. 5 is a control block diagram of the scanner unit, and FIG. 6 is a schematic explanatory diagram illustrating the main timing signals for document reading by the scanner unit. , FIG. 7 is a schematic sectional view of a laser scanner unit, FIGS. 8(A) and 8(B) are schematic explanatory views showing an example of the arrangement of the exposure portion of a photoreceptor, and FIG. 9(A). (B) and (C) are schematic explanatory diagrams explaining the drawbacks when two-color printing is performed using the contact development method, and FIG. 10 is a schematic diagram explaining the contamination of toner when two-color printing is performed using the contact development method. figure,
FIG. 11 is a schematic cross-sectional view showing an example of a developing device using a non-contact developing method, FIGS. )～(D)
is a schematic explanatory diagram for explaining the principle of solving the occurrence of color mixture, FIG. 14 is a schematic perspective view of a laser scanner unit,
Figure 15 (A) shows the deviation of the scanning start point of the laser beam 8
Figure 15 (F3) is an explanatory diagram showing the mismatch in the scanning length of the laser beam, Figure 16 is a block diagram showing the LBP connit and the LBP interface, and Figure 17 is the LBPI knit. 18 is a block diagram showing an example of the print control section of the LBP unit, and FIG. 19 is a block diagram showing an example of the print control section of the LBP unit.
FIG. 8 is a timing chart illustrating the operation of correcting the deviation of the laser beam scanning start point in the print control unit; FIG. 20 is a timing chart illustrating the horizontal synchronization signal forming operation in the sub-scanning direction in the print control unit; FIG. 21 is a block diagram showing another example of the printing control section, FIG. 22 is a detailed block diagram of the quaternary counter and selector of the printing control section shown in FIG. 21, and FIG. 23 is a block diagram of the scanning length of the laser beam. FIG. 24 is a timing chart of the operation for correcting mismatch. A schematic explanatory diagram of the second operation panel, FIG. 25 is a block diagram of the page memory address controller, FIG. 26 is a block diagram of the DMA controller, FIG. 27 is a block diagram of the image memory, and FIG. 28 is a block diagram of the scanner interface. 29 is a detailed block diagram of the image data processing section shown in FIG. 28, and FIGS. 30(A) and 30(R) are for explaining enlargement and reduction of data in the image data processing section, respectively. FIG. 30(A) is a timing chart when writing to the line memory, FIG. 30(B) is a timing chart when reading from the line memory, and FIG.
Figure 1 is a block diagram of the LBP interface, Figure 32 is a schematic explanatory diagram explaining the image composition mode, Figure 33 is a schematic diagram showing various information for specifying image extraction and image forming position, and Figure 34 is a schematic diagram showing various information for specifying image extraction and image forming position. A schematic explanatory diagram showing an example of a display requesting information for inputting the information shown in FIG. 33, No. 35
The figure is a schematic explanatory diagram explaining the image forming position designation mode in the compositing mode, Figure 36 is a schematic diagram explaining the image extraction area division designation mode, and Figure 37 is a schematic diagram explaining the mode for erasing the outline of the document. 38 is a schematic explanatory diagram illustrating a mode in which page numbers are assigned in accordance with the input order of originals in the composition mode, and FIG. 39 is a schematic explanatory diagram illustrating a mode in which page numbers are assigned in the output order of output sheets. be. 200... Horizontal synchronization detection means, 301... Photoreceptor, 302.304... Charging means, 303.305... Developing means, 311.314, 316, 318, 319° 320...
・First electrostatic latent image forming means, 312, 313, 315,
317,319°320...Second electrostatic latent image forming means. Figure 8 (A) Hesitation 1 Tozui Inferiority≦ and (B) (C) 1st (A) (C) CB) (D) JP-A-61-2G95G1 (33) JP-A-Sho Gl -269561(37) JP-A-61-2G95G1(42) ~ CL CL TOTO) -1゜〇- TO

Claims (1)

[Claims] (1) A charging means for charging a photoreceptor, an electrostatic latent image forming means for scanning a laser beam to form an electrostatic latent image on the photoreceptor, and a developing means for developing the electrostatic latent image. In a laser printer that performs multi-color or multi-type printing by arranging a plurality of sets of electrostatic latent image forming means and developing means around a photoreceptor, a horizontal Synchronization detection means are arranged in a smaller number than the plurality of electrostatic latent image forming means, and the scanning start point of each laser beam of the plurality of electrostatic latent image forming means is determined by a horizontal synchronization detection signal from the horizontal synchronization detection means. A laser printer characterized by detection based on.