JPH0872299A - Image forming apparatus - Google Patents

Abstract

PURPOSE: To stably vary the depth of the potential of a latent image without altering data width and without using amplitude modulation by providing switch means for switching first means for guiding the laser lights from a plurality of laser light sources at the same point of an image carrying surface, and second means for guiding it to the different points on the same carrying surface. CONSTITUTION: An optical beam emitted from a semiconductor laser 31 is formed to substantially parallel beams by a collimator lens 35 and a diaphragm 32, and incident to a rotary polygon mirror 33 in a predetermined beam diameter. The mirror 33 is rotated at an equal angular velocity in a direction of an arrow, and the reflecting direction of the incident beam is continuously varied, and reflected as a polarized beam. The polarized beam is condensed by an f-θlens 34. The lens 34 corrects the distortion to prove timing linearity of scanning. The beam is scanned at an equal speed in a direction of an arrow on a photosensitive element 11 as image carrier. The data written on the member 11 is controlled according to the laser 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly, it guides light-modulated laser light emitted from a laser light source to an image bearing surface such as a photoconductor or an electrostatic recording medium, on which surface Further, the present invention relates to an image forming apparatus such as a copying machine, a laser beam printer, or a facsimile, which forms image information including an electrostatic latent image.

[0002]

2. Description of the Related Art As shown in FIG. 4, a conventional image forming apparatus uses a laser chip composed of one laser and one PD sensor. A laser chip emits light according to image data to form a latent image on an image bearing surface of a photoconductor, an electrostatic recording medium, or the like to form an image.
Further, the gradation is controlled by controlling the density by performing the PWM modulation on the image data.

[0003]

However, when PWM modulation is used, the width of the data also changes in order to change the depth of the potential of the latent image formed on the image bearing surface of the photoconductor or the electrostatic recording medium. There was a technical problem that it was necessary to make it possible. A method of changing the depth of the potential of the latent image by applying AM modulation to the laser light is also considered, but it is technically difficult to obtain a stable potential with this method, so it is possible to accurately express the gradation. There wasn't. Therefore, an object of the present invention is to provide an image forming apparatus capable of solving such a technical problem.

[0004]

In order to achieve such an object, the invention described in claim 1 is an image forming apparatus for guiding a laser beam onto an image bearing surface to form image information. A plurality of laser light sources for emitting the laser beam,
First image guiding means for guiding each of the laser beams emitted from the plurality of laser light sources to the same point on the image bearing surface, and each of the laser beams emitted from the plurality of laser light sources. Second light guide to different points on the support surface
And a switching means for switching between the first light guiding means and the second light guiding means.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the first light guide means causes the image data to be transferred to the image bearing surface by each of the plurality of laser light sources. Converting means for converting the plurality of image data to be scanned upward; a first image clock for determining a transfer rate for transferring the plurality of image data converted by the converting means to each of the plurality of laser light sources; A first scanning clock that determines a scanning speed for scanning the laser beam emitted from the laser light source on the image bearing surface, and the second light guide means outputs image data to the plurality of lasers. A second image clock that determines a transfer speed for transferring to each of the light sources, and a second scan that determines a scanning speed for scanning the laser beam emitted from the plurality of laser light sources on the image bearing surface. And a lock, said switching means,
An image clock switching unit that switches between the first image clock and the second image clock, and a scanning clock switching unit that switches between the first scanning clock and the second scanning clock. .

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, which of the first light guide means and the second light guide means is used as the switching means. In accordance with the above, there is provided means for changing the moving speed of the image bearing surface and the light emission amount of the laser light.

[0007]

According to the first aspect of the invention, in the image forming apparatus for guiding the plurality of laser beams emitted from the plurality of laser light sources onto the image bearing surface to form the image information, the input from the user. According to the above, each of the laser beams emitted from the plurality of laser light sources is guided to the same point or different points on the image bearing surface.

According to the second aspect of the present invention, when a plurality of laser beams emitted from a plurality of laser light sources are guided to the same point on the image bearing surface, the image data has a plurality of laser light sources. It is converted into a plurality of image data scanned by each. Further, depending on whether to guide a plurality of laser beams to the same point or different points on the image bearing surface,
The frequency of the image clock that determines the transfer speed for transferring the image data to the laser light source and the frequency of the scan clock that determines the scanning speed for scanning the laser beam emitted from the laser light source on the image bearing surface are switched.

According to the third aspect of the present invention, the moving speed of the image bearing surface and the moving speed of the image bearing surface are changed depending on whether the plurality of laser beams are guided to the same point or different points on the image bearing surface. The amount of laser light emitted changes.

According to the present invention, when a latent image is formed on an image bearing surface of a photoconductor or an electrostatic recording medium by a plurality of lasers, it is possible to scan the laser a plurality of times at one point, and the data width can be increased. It is possible to stably change the potential depth of the latent image without changing the value and without using AM modulation.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings.

(First Embodiment) FIG. 1 is a sectional view of an image forming apparatus of the present invention according to the first embodiment. The basic operation of the image forming apparatus will be described with reference to FIG. The originals stacked on the original feeding device 1 are sequentially conveyed one by one onto the original table glass surface 2. When the document is conveyed, the lamp 3 of the scanner portion is turned on and the scanner unit 4 moves to illuminate the document. The reflected light of the original passes through the lens unit 8 via the mirrors 5, 6, 7 and then the image sensor unit 9
Is input to

The image signal input to the image sensor unit 9 is input to the exposure control unit 10 directly or after being stored in an image memory (not shown) and read again.
The latent image formed on the photosensitive band by the irradiation light is the developing device 12
Or 13 is developed. The transfer sheet is conveyed from the transfer sheet stacking section 14 or 15 at the same timing as the formation of the latent image, and the developed toner image is transferred at the transfer section 16. The transferred toner image is fixed on the transfer paper by the fixing unit 17, and then discharged from the paper output unit 18 to the outside of the apparatus.

FIG. 2 is an enlarged view of the exposure controller 10 shown in FIG. The light beam emitted from the semiconductor laser 31 is made into substantially parallel light by the collimator lens 35 and the diaphragm 32, and is incident on the rotating polygon mirror 33 with a predetermined beam diameter. The rotary polygon mirror 33 rotates at a constant angular velocity in the direction shown by the arrow in FIG. 2, and with this rotation, the reflecting direction of the incident light beam continuously changes and is reflected as a deflected beam. . The deflected beam is condensed by the f-θ lens 34. Further, the f-θ lens 34 corrects the distortion aberration that guarantees the temporal linearity of the scanning. The light beam scans the photoconductor 11 as an image carrier at a constant speed in the direction of the arrow in the figure. The writing of data on the photoconductor 11 is performed by controlling the light amount of the semiconductor laser 31.

The operating principle of the image forming apparatus of the present invention will be described with reference to FIG. Reference numerals 51, 53, and 55 are waveforms of emitted laser light, and reference numerals 52, 54, and 56 are potential waveforms of latent images formed on the photoconductor by the laser light waveforms of 51, 53, and 55. T1 and T2 indicate the light emission time of the light waveform of each laser, and Va, Vb, and Vc indicate the potential depth of the potential waveform of the latent image formed on the photoconductor. 3 (a), 3 (b)
Shows a light waveform and a potential waveform when the same point on the photoconductor is scanned once with a laser beam. Further, FIG. 3C shows an optical waveform and a potential waveform when the same point on the photoconductor is scanned twice with a laser beam. Here, there is a relationship of T1 = 2 × T2.

Comparing FIGS. 3 (a) and 3 (b), although the number of times of laser scanning is one, the width of the latent image formed on the photoconductor is longer when the light emission time is longer (a). It can be seen that the potential is wide and deep. Comparing FIGS. 3B and 3C,
Since the laser emission time is the same, the width of the latent image does not change so much, but it can be seen that the potential becomes deeper in (c) where the number of scans is larger. Comparing FIGS. 3A and 3C, FIG.
It can be seen that in (c), a latent image with a width narrower than that in FIG. 3 (a) can be obtained with the same potential as in (a). From the above experimental results, it can be seen that the depth of the potential can be changed by scanning the same point on the photoconductor a plurality of times even with a latent image of the same width.

A hardware configuration of an image forming apparatus using a multi-laser, especially a twin laser will be described with reference to FIG. 128 is a laser A in the twin laser chip, 12
Reference numeral 9 is a laser B, and 130 is a PD sensor. Laser A
The image data for causing the light to be emitted is transferred from the image data processing unit 121 to the PWM 122, is PWM-modulated, and is sent to the laser driver LDD 124. This gives laser A
Emits light. The image data for causing the laser B to emit light is transferred from the image data processing unit 121 to the PWM 123, and the PW is transmitted.
It is M-modulated and sent to the laser driver LDD 125. This causes the laser B to emit light.

The amount of light emitted from laser A and laser B is PD
It is constantly controlled by an APC (auto power control) 127 that uses the output of the sensor. An image clock 126 serves as a reference for transferring image data. Three
Reference numeral 3 is a rotary polygon mirror for scanning the laser beam on the photosensitive member, 132 is a motor controller for controlling the rotation of the rotary polygon mirror, and 133 is a clock for rotating the motor. The image data processing unit 121, the APC 127 and the motor controller 132 are the system controller 134.
Controlled by.

(Embodiment 2) FIG. 5 shows a second embodiment of the present invention. Compared with the image forming apparatus of the first embodiment shown in FIG.
Image clock IPCLK1 for transferring image data
51, 152, and a scanning clock M serving as a reference for the motor driver 146 that controls the rotation of the rotary polygon mirror 33.
CLK 148, 149. These clocks
It is switched by the changeover switches 147 and 150.
Image data conversion unit 142 and conversion data table 14
Reference numeral 3 converts one image data into proper data when scanning the same point on the photoconductor a plurality of times. The transfer paths of the image data are switched by the changeover switches 144 and 145. A mode in which the same point on the photosensitive member is scanned once to obtain an image is called a normal mode, and a mode in which two points are scanned to obtain an image is called a special mode.

In the normal mode, the image clock is IPCL
The scan clock is connected to M151 and MCLK148. The image data is directly transmitted from the image data processing unit 141 to the PW.
144 and 14 as forwarded to M122 and 123
The changeover switch of No. 5 is set. Laser A and laser B alternately scan the photoconductor as shown in FIG. In FIG. 6, the line marked with ◯ is the scanning locus of the A laser, and the line marked with Δ is the scanning locus of the B laser, and two lines of latent images are simultaneously formed by one scanning by one surface of the rotary polygon mirror 33. As described above, the transfer clock of image data, the scanning clock of laser scanning, and the rotation speed of the photoconductor 11 are determined. In the normal mode, a latent image can be formed on the photoconductor at twice the speed with the same image clock and scanning clock as compared with the case where a single laser beam is used.

When the special mode is selected on the control panel 154, the connection of each switch is switched under the control of the system controller 153. That is, the image clock is IPCLK152 and the scanning clock is MCL.
The image data input to the PWMs 122 and 123 at K149 is switched to the path passing through the image data conversion unit 142. Here, IPCLK152 = 2 ×
IPCLK151, MCLK149 = 2 × MCLK14
8 and the rotation speed of the photoconductor 11 does not change.
The scanning loci of the two laser beams on the photoconductor overlap as shown in FIG. By tracing the scanning locus of the A laser after the scanning locus of the B laser, the laser scans the same point on the photoconductor twice.

Since the scanning speed is doubled, the irradiation time of one pixel by one laser is halved, and the charging potential on the photosensitive member is halved. Therefore, in order to obtain the same image as the image in the normal mode in the special mode, it is necessary to guide the same data twice to the same point on the photoconductor in order to make the charging potential the same. In the conversion data table 143,
For example, when the image data in a normal mode at a certain point can be expressed as 80H with 8 bit 256 gradations, 80H and 80H are stored as converted data that can obtain the image data in the normal mode 80H when scanning is performed twice. Has been done. However, depending on the gradation of the image data and the density distribution of the surrounding image data, for example, 60H and 60
In some cases, such as H, the data in the normal mode and the data in the special mode may be different.

The image data conversion unit 142 causes the PWM1
The image data transferred to 22 and 123 are converted. By switching the image clock and the scanning clock and converting the image data, the laser can scan the same point of the photoconductor twice, and the potential depth of the latent image can be changed without changing the data width. it can.

(Third Embodiment) FIG. 8 shows the configuration of the third embodiment. Compared with the image forming apparatus of the first embodiment described with reference to FIG. 5, two process clocks MMCLK 161 and 162 for controlling the rotation of the photoconductor, and two target values 165 for APC control of the laser. 16
6 is provided. These are changeover switches 163 and 167.
Switch by. Further, in order to convert one image data into proper data when scanning the same point on the photoconductor a plurality of times, the same image data conversion process as in the first embodiment is performed.

In normal mode, the process clock is MM
The target value for CLK 161 is connected to REF 165. The image data is sent directly from the image data processing unit 141 to the PWM 12
The changeover switches 144 and 145 are set so as to be transferred to 2 and 123. As a result, the laser scans the photoconductor in the same manner as the laser scanning shown in FIG. 6 in the first embodiment.

When the special mode is selected on the control panel 154, the connection of each switch is switched by the system controller 153. That is, the process clock is MMCLK 162, and the target value for APC control is R
The image data input to the PWMs 122 and 123 in the EF 166 is routed through the image data conversion unit 142,
Each can be switched. Here, MMCLK161 =
2 × MMCLK 162. The voltage value of the REF 165 is about twice the voltage value of the REF 166, and the rotary polygon mirror 33
The rotation speed of does not change. Two laser beams overlap and scan the photoconductor as shown in FIG. By tracing the scanning locus of the B laser with the A laser, the laser scans the same point on the photosensitive member twice.

In the present embodiment, the scanning time per pixel in the special mode is the same as the scanning time in the normal mode. Therefore, in order to obtain the same image as in the normal mode in the special mode, the amount of laser light emission is halved to adjust the charging potential on the photoconductor. The conversion data table 143 stores conversion data that can obtain appropriate image data when scanned twice as in the first embodiment. PWM
1, the image data transferred to PWM2 is converted into an appropriate value by the image conversion unit 142. By switching the process clock and the target value of APC control and converting the image data in this way, the laser can scan the same point on the photoconductor twice, and the latent image can be displayed without changing the data width. The depth of the potential of can be changed.

[0028]

As described above, according to the present invention, in a device using twin beams or multi-beams,
The same point on the photoreceptor can be scanned multiple times. Therefore, the potential depth on the photoconductor can be stably changed independently of the image data, and a high-quality image with improved resolution and gradation can be formed.

[Brief description of drawings]

FIG. 1 is a sectional view of an image forming apparatus of the present invention.

FIG. 2 is an optical configuration diagram in the exposure control unit of FIG.

FIG. 3 is a diagram illustrating the principle of the present invention.

FIG. 4 is a configuration diagram of an apparatus using a general multi-beam.

FIG. 5 is a configuration diagram of a first embodiment of the present invention.

FIG. 6 is an operation explanatory diagram of an apparatus using a general multi-beam.

FIG. 7 is an operation explanatory diagram of the first embodiment according to the present invention.

FIG. 8 is a configuration diagram of a second embodiment of the present invention.

FIG. 9 is a configuration diagram of a conventional device using a single beam.

[Explanation of symbols]

 1 Document Feeding Device 2 Platen Glass Surface 3 Lamp 4 Scanner Unit 5, 6, 7 Mirror 8 Lens Unit 9 Image Sensor Section 10 Exposure Control Section 11 Photoreceptor 12, 13 Developer 14, 15 Transferred Paper Loading Section 16 Transfer Part 17 Fixing part 18 Paper discharge part 31 Semiconductor laser 32 Aperture 33 Rotating polygon mirror 34 f-θ lens 35 Collimator lens 51, 53, 55 Laser light waveform 52, 54, 56 Latent image potential waveform 121 Image data processing part 122 , 123 PWM 124, 125 Laser driver 126 Image clock 127 Auto power control 128 Laser A 129 Laser B 130 PD sensor 132 Motor controller 133 Clock 134 System controller 141 Image data processing unit 142 Image data conversion unit 143 Change Data table 144, 145 over switch 146 a motor driver 148, 149 scan clock 147,150 changeover switch 151, 152 image clock 153 system controller 154 control panel 161 and 162 MMCLK 165 and 166 target values 163 and 167 change-over switch

Claims (3)

[Claims] 1. An image forming apparatus for guiding a laser beam onto an image bearing surface to form image information, and a plurality of laser light sources for emitting the laser beam, and laser beams emitted from the plurality of laser light sources. A first light guide means for guiding each of the laser beams to the same point on the image bearing surface, and a first light guide means for guiding each of the laser beams emitted from the plurality of laser light sources to different points on the image bearing surface. An image forming apparatus comprising: a second light guide unit; and a switching unit that switches between the first light guide unit and the second light guide unit. 2. The image forming apparatus according to claim 1, wherein the first light guide means scans image data on the image bearing surface by each of the plurality of laser light sources. Conversion means for converting into data, a first image clock that determines a transfer rate for transferring the plurality of image data converted by the conversion means to each of the plurality of laser light sources, and light emitted from the plurality of laser light sources A first scanning speed for scanning the image bearing surface with the laser beam;
And a second scanning clock, the second light guide means determines a transfer speed for transferring image data to each of the plurality of laser light sources, and the second light guide emits light from the plurality of laser light sources. An image clock switch that has a second scanning clock that determines a scanning speed for scanning the image bearing surface with a laser beam, and the switching unit switches between the first image clock and the second image clock. An image forming apparatus comprising: a unit and a scanning clock switching unit that switches between the first scanning clock and the second scanning clock. 3. The image forming apparatus according to claim 1, wherein the switching unit uses the first light guiding unit or the second light guiding unit to carry the image carrier. An image forming apparatus comprising means for changing a moving speed of a surface and an emission amount of the laser light.