JPH11287963A - Multibeam writing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the service lines of all light emitting elements for multi- laser-beam exposure and to eliminate variance of the lives. SOLUTION: The multibeam printer equipped with plural light emitting elements LD1 to LD4, drivers LDD1 to LDD4 which drive the elements to emit lights, a scanner which performs main scanning with beams B1 to B4 while giving positional differences to sub scanning on a photosensitive body, a sensor 11 which detects beam lights outside the light exposure main scanning width, and a generator 11 which generates a synchronizing signal DP prescribing the write start position of main scanning (x) according to the detection signal is equipped with means 12 and 13 for generating turn-on signals for generating beam lights to be detected by the sensor 11, output means SW1 and OR1 to OR4 which supply the turn-on signals to one of the drivers LDD1 to LDD4 selectively, and a means MPU which switches the drivers supplying the turn-on signal in time series.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-beam writing apparatus for exposing a photoreceptor surface with a plurality of beam lights. This is used for a laser printer, for example.

[0002]

2. Description of the Related Art In a scanner, a plurality of laser beams which are substantially at the same position in the main scanning direction x and are separated by a predetermined distance in the sub-scanning direction y are main-scanned, and a main scanning starting point which is out of the main scanning width on the surface of the photosensitive member. A multi-beam writing device that generates a synchronization detection signal when a sensor provided on the side laser beam path detects a light beam, and determines a writing start position of each laser beam in the main scanning direction based on the synchronization detection signal. Conventionally, all of the beams are turned on,
All beams are detected by the sensor, and a falling point at which the sensor changes from beam detection to non-beam detection, that is, a point at which all beams have passed through the sensor has been used as a reference point.

[0003]

Therefore, the total lighting time of all the laser light emitting elements is long, and the life of the laser light emitting elements is short. For example, four laser light emitting elements LD1 to LD4
In the case of simultaneously performing line exposure of four lines separated in the sub-scanning direction (four lines of main scanning), as shown in FIG.
The two laser light emitting elements LD1 are turned on for synchronization at the sensor scanning timing on the main scanning start side, the sensor detects this, and generates a synchronization signal DP at the point where the sensor switches from detection to non-detection. Starting from this synchronization signal DP, the image exposure start timing is determined and the four laser light emitting elements LD
By exposing the surface of the photoreceptor by modulating the light emission of LD1 to LD4 with four sets of image data, laser light emitting elements LD2 to L
The life of D3 is extended.

By limiting the lighting time for synchronization of the laser light emitting element LD1 to a minimum, the lighting extension time of the laser light emitting element LD1 is also shortened. However, the life of the laser light emitting element LD1 is short because it is always turned on for synchronization. .

The first object of the present invention is to shorten the lighting time of all the light emitting elements and extend the life of the light emitting elements, to make the lighting time of all the light emitting elements uniform, and to reduce the variation in the life of each light emitting element. The second purpose is to eliminate it.

[0006]

(1) The present invention provides a plurality of light sources (LD1 to LD4) and a driver (LDD1) for energizing each light source.
~ LDD4), a plurality of light beams from the plurality of light sources (B1 ~ B
4) a scanner (2-9) that scans the surface of the photoconductor in the main scanning direction x with a positional difference in the sub-scanning direction y on the surface of the photoconductor (7);
A sensor (11) for detecting a light beam outside the main scanning width with respect to the photoconductor surface, and generating a synchronization signal (DP) for defining a writing start position in the main scanning direction x according to the light beam detection signal of the sensor; Means for generating a lighting signal for generating a beam light detected by said sensor (11) in a multi-beam writing apparatus comprising a synchronization signal generator (11).
(12, 13), output means (SW1, OR1 to OR4) for selectively applying the lighting signal to one of the drivers (LDD1 to LDD4), and output means (SW1, OR1 to OR4). Means (MPU) for switching a driver for giving a lighting signal in time series.

[0007] In order to facilitate understanding, the symbols of the corresponding elements or the corresponding items of the embodiment shown in the drawings and described later are added in the parentheses for reference.

[0010] According to this, since only one light source is selectively turned on for synchronization detection, the lighting time of the plurality of light sources as a whole is shortened. In addition, instead of always turning on only one specific light source for synchronization detection, the light source to be turned on for synchronization detection is switched, so that the lighting times of all light sources are uniformed and the variation in the life of each light source is reduced. .

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (2) The switching means (MPU)
The driver for applying the lighting signal is sequentially switched for each page of the image formed on the photosensitive member surface. Since the light sources that are turned on for synchronization detection are switched in units of pages for image formation, the effect of uniformity is high, and there is no variation in the life of each light source.

[0010] (3) The switching means (MPU) sequentially switches the driver for supplying the lighting signal for each image forming job specified by the switching means. For example, when the start of image formation for page a and each b sheets is instructed, a series of image formation for page a and each b sheets is one job. Even in this case, the effect of the uniformization is high, and there is no variation in the life of each light source.

(4) The switching means (MPU) is provided for each day,
The driver that gives the lighting signal is sequentially switched. Also in this case, the effect of the uniformization is high, and there is no variation in the life of each light source.

(5) The means (12, 1) for generating the lighting signal
3) is a pulse generated in synchronization with the main scanning of the scanner.
(WCLK) and counting means (12) initialized by a synchronization signal (DP), and comparing means for generating a lighting signal when count data of the counting means (12) matches a set value. (13) is included.

(6) Each of the output means (SW1, OR1 to OR4) outputs a lighting signal and an image data to each of the drivers.
A plurality of gate means (OR1 to OR4) for providing data, and a gate means (OR1) designated by a switching means (MPU) to a lighting signal generated by the lighting signal generating means (12, 13). ~ OR4)
And a switch means (SW1) for supplying to the

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0015]

FIG. 1 shows a scanner section according to an embodiment of the present invention. A light emitting diode array (hereinafter referred to as an LD array) 1 emits four laser beams. These four laser beams are narrowed by a collimating lens 2, an aperture 8 and a cylindrical lens 3. A laser beam having a diameter and a cross section shaped into a predetermined shape is irradiated onto the polygon mirror-4. Since the polygon mirror 4 is continuously rotating at a constant speed, the laser beam hitting the pongon mirror 4 is reflected toward the mirror 9 but moves repeatedly in the main scanning direction x.

The laser beam reflected by the pongon mirror 4 is reflected by the mirror 9 through the fθ lens 5 and the surface tilt correcting lens 6, and hits the photoreceptor surface on the photoreceptor drum 7. In the LD array 1, four light emitting sources (micro holes for regulating emitted light) LD1 to LD4 (FIG. 4) are distributed in the z direction. Four laser beam irradiation trajectories having a position difference in the sub-scanning direction y are drawn.

FIG. 2 shows the appearance of the LD array 1. L
The heterodyne junction surface 1a of the D array 1 has four lasers.
The diodes are formed, and the laser light generated by the laser diodes passes through micro holes (not shown) of a mask provided on the surface of the LD array and becomes laser beams B1 and B2. FIGS. 1 and 2 show 2
Although a laser beam of four lasers is shown, four lasers are actually used.
The beam is generated from the LD array 1 and irradiated on the photosensitive drum 7. If the number of laser beams is two or more, simultaneous exposure of a plurality of lines is possible. In this specification, "multi-beam" means two or more beams.

Referring again to FIG. When there is a laser beam outside the required main scanning width on the photosensitive drum 7 and at the start end of the main scanning x, there is a synchronous mirror 10 at a position where the laser beam is received. Receives light. FIG. 3 shows a front view in which the synchronization mirror 10 and the synchronization detection sensor 11 are seen through from the back side of the mirror 9 shown in FIG.
(A) shows two laser beams B1 and B2 in which the LD array 1 has two laser beams.
(B) shows a case where four laser beams B1 to B4 of this embodiment are generated. The synchronous detection sensor 11 is a synchronous mirror of four laser beams B1 to B4.
10 reflected light is received.

FIG. 4 shows that the synchronization detection sensor 11
1 shows an electric circuit for generating P. When any one of the four laser beams B1 to B4 hits the photodiode of the synchronization detection sensor 11, the detection circuit in the sensor 11 generates a synchronization detection signal DP. The main scanning counter 12 is supplied with a main scanning synchronization clock WCLK generated based on a speed synchronization pulse of a phase synchronization motor driver that rotationally drives a motor that rotationally drives the polygon mirror-4. Is the scan synchronization clock WC
Count LK. When the count value reaches a set value corresponding to the main scanning repetition pitch, the output of the comparator 13 rises from low (L) to high (H), and the changeover switch SW1 is turned on.
Through one of the OR gates OR1 to OR4 (for example, O
R1). Thereby, the one ore gate (O)
The output of R1) becomes H, and the LD driver (LDD1) turns on one laser diode (LD1) of the LD array 1. When the main scanning enters the detection area of the synchronization detection sensor 11, the synchronization detection sensor 11 generates an H-level synchronization detection signal DP, and when exiting the detection area and heading for the main scanning area (on the photoconductor), synchronization detection is performed. The signal DP returns to L. At this fall, the main scanning counter 12 and the comparator 13 are reset (initialized), and the main scanning counter 12 starts counting up from the initial value (0) again, and the output of the comparator 13 (lighting signal). Returns to L (non-lighting instruction).

When the polygon mirror-4 is driven to rotate at a constant speed and the image exposure time comes, a microcomputer MPU for controlling the output (exposure) of image data is LD1.
ＬＤLD4 One of the image signals is set to the lighting instruction level H, and waits for the generation of the synchronization detection signal DP (high level H). Thus, the first reset of the main scanning counter 12 is performed at the timing when the synchronization detection signal DP is generated, and thereafter, the lighting signal is generated at one main scanning pitch by the operation of the counter 12 and the comparator 13 described above. Occur.

The synchronization detection signal DP is supplied to a microcomputer MPU for controlling the output (exposure) of image data. The MPU receives the image data from the falling point of the synchronization detection signal DP from H to L. Data output timing is determined, and four lines of image data are simultaneously output to OR gates OR1 to OR4. In this embodiment, the MPU switches the input / output connection of the switch SW1 immediately before starting image output for one page. The switching order is to step down from SW1-1 to SW1-4 sequentially.
Return to W1-1.

FIG. 5 shows a process of switching the laser diode for emitting light for synchronization detection in a page unit of the MPU. The MPU executes this processing before writing each page, and selects LD1, 1, 5,..., 1 + 4n, when writing a page (SW1-1 is closed) 2, 6,..., 2 + 4n, and when writing a page, LD2. Selection (close SW1-2) 3, 7, ..., 3 + 4n, select LD3 when writing page (close SW1-3) 4, 8, ..., 4 + 4n, select LD4 when writing page (select SW1-4) Closed)

FIG. 6 shows a laser diode LD shown in FIG.
1 shows the light emission timing of LD4. The first page is LD
1 emits light for synchronization detection, and LD2
The laser diode that emits light for synchronization detection is switched for each page.

In this example, the switching is performed on a page basis, but it is also effective to switch this on a job basis or on a date basis. Here, a job is an MPU that executes one or several pages of image formation of one or two pages each designated by an operator or a host computer when an execution instruction is given. Means a series of image data output processing, that is, one set of image formation.

FIG. 7 shows a process of switching the laser diode for emitting light for synchronization detection in the MPU on a job-by-job basis. The MPU executes this processing before writing each job, and selects 1, 5,..., 1 + 4n, LD1 when writing a job (SW1-1 is closed) 2, 6,..., 2 + 4n, and LD2 when writing a job. .. 3 + 4n, select LD3 when writing a job (close SW1-3) 4, 8,... 4 + 4n, select LD4 when writing a job (select SW1-4) Closed)

In another embodiment, the MPU performs the switching on a day-by-day basis. The MPU has a non-illustrated non-volatile memory and a clock (calendar clock). When the power is turned on, the date and selected data (SW) of the non-volatile memory are stored.
If the date of the clock does not match the date of the non-volatile memory with reference to data indicating which of 1-1 to SW1-4 is selected for output, the above-described step-down switching is performed. The date of the clock and the selected data after switching are updated and stored in the nonvolatile memory.

As described above, according to the present invention, all the laser diodes LD1 to LD4 are not turned on for synchronization detection every time, and the laser diodes to be turned on are averaged. The life of the diodes LD1 to LD4 can be extended.

Switching between write lines (main scanning) can be achieved by changing the synchronization detection timing with the laser diode LD1 to LD4 due to variations in the amount of light and variations in the shape (light spot shape). This method is not used because there is a risk that the writing position shifts in the main scanning direction, which differs every time.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a scanner unit according to an embodiment of the present invention.

FIG. 2 is an enlarged perspective view showing an appearance of the LD array 1 shown in FIG.

FIG. 3 shows a synchronous mirror from the back side of the mirror 9 shown in FIG. 1;
10A and 10B are enlarged front views of the LD array 1 and the synchronous detection sensor 11 seen through, and FIG.
(B) shows a case in which four BRAMs are generated.
The case where the beam B1 to B4 is generated is shown.

4 is connected to the synchronization detection sensor 11 shown in FIG.
FIG. 4 is a block diagram illustrating a circuit that generates a lighting signal for generating a synchronization signal.

FIG. 5 is a diagram of the microcomputer MPU shown in FIG.
It is a flowchart which shows the process of switching the laser diode to light for synchronization detection in page unit.

FIG. 6 shows a laser diode driver LDD shown in FIG.
Time chart showing lighting signals given to LDD1 to LDD4
It is.

FIG. 7 is a flowchart showing a process of switching a laser diode to be turned on for synchronization detection in the MPU according to the second embodiment of the present invention.

FIG. 8 is a time chart showing a lighting timing when only one specific laser diode LD1 out of four laser diodes LD1 to LD4 is turned on for synchronization detection.

[Explanation of symbols]

 1: LD array 2: Collimating lens 3: Cylindrical lens 4: Polygon mirror 5: fθ lens 6: Surface tilt correction lens 7: Photoconductor drum 8: Aperture 9: Mirror

Claims (4)

[Claims] 1. A plurality of light sources, a driver for energizing each of the light sources, and a plurality of light beams from the plurality of light sources are displaced in the sub-scanning direction y on the photoconductor surface in the main scanning direction x. , A sensor for detecting a light beam outside the main scanning width with respect to the photoreceptor surface, and a synchronizing signal for generating a synchronizing signal for defining a writing start position in the main scanning direction x according to the light beam detection signal of the sensor. A multi-beam writing apparatus comprising: a signal generator; a means for generating a lighting signal for generating a beam light detected by the sensor;
A multi-beam writing apparatus, comprising: output means for selectively supplying a lighting signal; and means for switching a driver for supplying a lighting signal through the output means in time series. 2. The multi-beam writing apparatus according to claim 1, wherein said switching means sequentially switches a driver for supplying a lighting signal for each page of an image formed on said photosensitive member surface. 3. The multi-beam writing apparatus according to claim 1, wherein said switching means sequentially switches a driver for supplying a lighting signal for each image forming job specified by said switching means. 4. The multi-beam writing apparatus according to claim 1, wherein said switching means sequentially switches a driver for supplying a lighting signal every day.