JP2003034050A - Image forming device - Google Patents

Abstract

(57) Abstract: An image forming apparatus capable of improving the quality of a printed image is provided. A light source for emitting a laser beam is provided.
12; an optical modulator for modulating a laser beam based on the pixel data stored in the data storage unit 36; and a scanning unit P2, and one line of pixel data along the scanning direction is optically modulated from the data storage unit 36. Two times in a row,
It is configured to be repeatedly exposed with one line of pixel data along the main scanning direction. When one line of pixel data has pixel data lower in density than the set image density, it is sent a second time. The pixels exposed with low-density pixel data are shifted from the pixels 60 exposed with the same low-density pixel data sent for the first time by half the pixel pitch in the main scanning direction. And timing controllers 44, 45 and 46 for shifting the timing of the second transmission of the low-density pixel data.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source for emitting a laser beam, an optical modulator for modulating the laser beam based on pixel data stored in a data storage unit, The present invention relates to an image forming apparatus provided with scanning means for scanning a modulated laser beam on a photosensitive material in a main scanning direction and a sub-scanning direction orthogonal to the main scanning direction. 2. Description of the Related Art Conventionally, the above-described image forming apparatus is configured so that pixel data for one line along the main scanning direction is simply sent once from a data storage unit to an optical modulator. Was. The above-mentioned conventional image forming apparatus is configured so that pixel data for one line along the main scanning direction is simply sent once from a data storage unit to an optical modulator. However, there were the following problems. That is, for pixel data having a high image density (hereinafter referred to as "density"), as shown in FIG.
Since the photosensitive material reacts greatly to increase the size of the pixel 60a, a portion where pixels 60a and 60b adjacent to each other in the sub-scanning direction interfere with each other is likely to be a blurred image. Further, for pixel data having a low density,
As shown in FIG. 7, the reaction of the photosensitive material is small and the pixel 60
a, 60b become smaller, so that adjacent pixels 60a, 60b,
A gap is generated between 60b, and an unnatural image having a large graininess is likely to occur. The present invention has been made in view of the above circumstances, and has as its object to provide an image forming apparatus capable of improving the quality of a printed image. [0007] The structure, operation and effect of the invention according to claim 1 are as follows. [Structure] In the image forming apparatus described at the beginning, pixel data for one line along the main scanning direction is sent twice from the data storage unit to the optical modulator in the main scanning direction. Is configured to be repeatedly exposed with pixel data for one line along the line. If the pixel data for one line includes pixel data having a density lower than the set image density, the low density The pixels exposed with the pixel data of the first scan are shifted from the pixels exposed with the same low-density pixel data sent at the first time by a half pitch of the pixel pitch in the main scanning direction. A timing control unit for shifting the timing of the second transmission of the low-density pixel data is provided. [A] [B] One line of pixel data along the main scanning direction is sent twice from the data storage unit to the optical modulator, and is repeated with one line of pixel data along the main scanning direction. Since the exposure is performed, as shown in FIG. 3, one of the lines of the pixels 60a for one line and the line of the pixels 60b for another line formed by the image forming apparatus having the conventional configuration are disposed on one side. A column of pixels 60c for one line is further formed. [B] Since the energy of the laser beam is larger on the side corresponding to the center of the pixel (see FIG. 6), the energy of the laser beam is different from that of the row of the pixel 60a for one line formed by the conventional image forming apparatus. The central portion of the laser beam having a high energy is applied to the blurred pixel portion between the line of the pixel 60b for one line and the pixel, whereby the pixel can be sharpened. [C] In the above case, if pixel data of one line contains pixel data having a density lower than the set image density, the pixel exposed with the low density pixel data sent for the second time is The timing control unit controls the low-density pixel data so that the pixels exposed with the same low-density pixel data sent for the first time are shifted by half a pixel pitch in the main scanning direction. 4, the timing of the second feed is shifted, so as shown in FIG. 4, even if the image has a low density, the pixels 60a, 60a,
The gap between 60b and 60c can be reduced and dispersed. [D] According to the above [a], [b] and [c], blurring is reduced in a high-density image, a sharp image can be obtained, and graininess in a low-density image is small. Natural images can be obtained. [Effects] Therefore, the above operations [A] to [D]
As a result, an image forming apparatus capable of improving the quality of a printed image can be provided. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of a laser exposure apparatus 100 (an example of an image forming apparatus). <Structure of Laser Exposure Apparatus> As shown in FIG. 1, the laser exposure apparatus 100 is roughly provided with a laser light source section P1 and a laser scanning section P2. The laser light source unit P1 includes an R light laser diode 10 functioning as a red laser light source and a G light laser diode pumped solid laser (hereinafter, referred to as a green laser light source).
Abbreviated as LD pumped solid laser. ) 11 and a B-light LD pumped solid-state laser 12 functioning as a blue laser light source
And an R photoacoustic optical element that modulates the R laser beam output from the R optical laser diode 10 (corresponding to an optical modulator, and the acoustooptical element is hereinafter abbreviated as AOM).
And G light AOM14 for modulating the G laser beam, and B
B light AOM15 for modulating the light laser beam and each AO
An R light AOM driver 16, a G light AOM driver 17, and a B light AOM driver 18 for driving the M13, M14, M15, respectively are provided. An R light laser diode 10, G light, B light LD pumped solid state lasers 11, 12 and each AOM 13, 1
Condensing lenses 19, 20, 2 are provided in the optical path between
1, the diameter of the beam incident on each of the AOMs 13, 14, 15 is reduced. The modulation speed can be increased by narrowing the beam diameter. The structure of the B-light AOM 15 will be briefly described. An acousto-optic medium 15a for producing an acousto-optic effect, a piezoelectric element 15b for outputting ultrasonic waves by a high-frequency signal input from a B-light AOM driver 18, 15a
And an ultrasonic absorber 15c that absorbs the ultrasonic wave that has passed through. The blue laser beam incident on the B light AOM 15 is diffracted in accordance with the frequency and amplitude of the high frequency signal from the B light AOM driver 18, and the B light AOM 1
5 output a plurality of diffracted blue laser beams. A B light shielding plate 2 is provided on the lower side of the optical path of the B light AOM 15.
4 are provided so as to pass only the first-order diffracted light having the highest intensity among the diffracted lights. As described above, the high frequency signal corresponding to the image data is generated by the B light AOM driver 18 and the high frequency signal is converted to the B light AOM1.
5, the blue laser beam can be subjected to light modulation corresponding to the image data. The above points are the same for the other AOMs 13 and 14, and the R light shielding plate 22 and the G light shielding plate 23 are provided similarly to the B light shielding plate 24. The laser light source P1 is provided with a synthesizing means C for synthesizing each laser beam. The synthesizing unit C includes a first mirror 25, a second mirror 26, and a third mirror 27 arranged in this order from the upper side of the optical path. <Structure of Laser Scanning Unit> The synthesized laser beam is scanned by a laser scanning unit (corresponding to scanning means) P2. The laser scanning unit P2 includes a correction mirror 30
, A polygon mirror 31, an fθ lens 32, a mirror 33 for controlling a scanning start position, and an optical sensor 34 for detecting a laser beam reflected from the mirror 33. The polygon mirror 31 is a polygon driver 3
The laser beam is driven and controlled by rotating the laser beam 5 in the clockwise direction in FIG.
The main scanning is performed on the image to expose and form an image. Also, if the polygon mirror 31 is tilted, the quality of the image is degraded.
A correction mirror 30 is provided to correct this. The fθ lens 32 corrects the laser beam deflected at a constant angular velocity by the polygon mirror 31 so that the laser beam becomes uniform on the photographic paper 1. Thereby, the distortion is corrected. The feeding mechanism for the printing paper 1 includes a driving roller 40 and a pressure roller 41 for holding the printing paper 1, a pulse motor 42 for driving the driving roller 40, and a motor driver 43. With the above structure, the laser beam in the laser scanning section P2 is main-scanned while the printing paper 1 cut to the print size is conveyed in the sub-scanning direction. The image is printed on the photographic paper 1 and exposed. The printing paper 1 which has been printed and exposed is subjected to development processing and drying processing, and is discharged out of the apparatus. <Control Block Diagram> FIG. 2 is a control block diagram. The scanner device S is a device for reading an image on the negative film 2, and includes a reading light source 3, an imaging lens 4, a CCD sensor 5, and a negative film transport roller 6.
And The read image data is transferred to and stored in the image data storage unit 36 of the laser exposure apparatus 100. As the image data stored in the image data storage section 36, data stored in the digital camera 7, the floppy (registered trademark) disk 8, and the CD-ROM 9 may be taken. System controller 37 as control unit
Controls the operation of each part of the laser exposure apparatus 100, and FIG. 2 shows main functions. The image data stored in the image data storage unit 36 is
The signals are sent to the drivers 16, 17, and 18, and signals for modulating the laser beam are generated. The laser driver 38 drives each of the laser light sources 10, 11, and 12. The correction mirror driver 39 drives the correction mirror 30 in synchronization with the rotation of the polygon mirror 31, and corrects the surface tilt.
Further, the system controller 37 controls the main scanning start position based on a signal from the optical sensor 34. The above control system will be described in more detail. Under the control of the image data storage unit 36 by the system controller 37, pixel data for one line along the main scanning direction (a group of the pixel data is image data). Each AOM driver 16, 1 is stored in the image data storage unit 36.
It is configured to be sent twice following 7 and 18 and to be repeatedly exposed with pixel data for one line along the main scanning direction. By this control, as shown in FIG. 3, between the column of pixels 60a for one line and the column of pixels 60b for another line formed by the conventional image forming apparatus. , And a column of pixels 60c for one line is further formed. In this case, the energy of the laser beam is larger on the side corresponding to the center of the pixel (see FIG. 6).
A blurred pixel portion between a row of pixels 60a for one line and a row of pixels 60b for another line formed by an image forming apparatus having a conventional configuration has a central portion of a high-energy laser beam. Has been irradiated. This allows
Pixels can be sharpened, and blurring is reduced in a high-density image, and a sharp image can be obtained. When the density discriminating section 55 provided in the system controller 37 discriminates that there is pixel data having a density lower than the set image density in the one line of pixel data, as shown in FIG. The pixel 60c exposed with the low-density pixel data sent for the second time is half the pixel pitch in the main scanning direction with respect to the pixel 60a exposed with the same low-density pixel data sent for the first time. The transfer timing control units 44, 45,
46 shifts the timing of the second sending of the low-density pixel data. The system controller 37 controls the image data storage unit 36 so that pixel data is sent from the image data storage unit 36 to each of the AOM drivers 16, 17, and 18 when a pulse from the reference pulse generator 56 rises. However, the transfer timing control units 44, 45, 46
When the density determining unit 55 determines that there is low-density pixel data as described above, each AOM
Pixel data is sent to the drivers 16, 17, and 18. With this control, as shown in FIG. 4, the gap between the pixels 60a, 60b and 60c adjacent to each other in the main scanning direction and the sub-scanning direction is reduced even in the case of a low-density image.
In addition, it can be dispersed, and a natural image with less graininess can be obtained in a low-density image. FIG. 5 shows an image portion A having a high image density and an image portion B having a low image density. At the boundary between the pixels of the image portion A having a high image density and the pixel of the image portion B having a low image density, at least one of the pixels 60c adjacent to each other spreads to the other pixel side, and the gap between the two pixels is filled. <Another Embodiment> The optical modulator may be other than the AOM. The laser light source may be other than the above.

[Brief description of the drawings] FIG. 1 is a schematic view of a laser exposure apparatus. FIG. 2 shows a control system. FIG. 3 is a diagram showing a pixel; FIG. 4 is a view showing a pixel; FIG. 5 is a diagram showing a pixel; FIG. 6 is a diagram showing a conventional technique. FIG. 7 is a diagram showing a conventional technique. [Explanation of symbols] 10,11,12 Light source 13,14,15 Optical modulator 36 Data storage unit 37 Control unit 44, 45, 46 timing control unit 60 pixels P2 scanning means

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Makoto Yamashita             No. 1 at 579 Umehara, Wakayama City, Wakayama Prefecture             Ritsu Koki Co., Ltd. F term (reference) 2C362 AA22 AA28 AA31 BB28 CA08                       CA09 CA14 CB71 CB75 CB78                 5C072 AA03 BA15 HA02 HA13 HB11                       UA11 UA17                 5C074 AA02 BB17 CC22 DD06 DD16                       EE02 EE04

Claims (1)

Claims: 1. A light source for emitting a laser beam, an optical modulator for modulating the laser beam based on pixel data stored in a data storage unit, and a light source for applying the modulated laser beam to a photosensitive material. An image forming apparatus provided with scanning means for scanning in a main scanning direction and a sub-scanning direction orthogonal to the main scanning direction, wherein the pixel data for one line along the main scanning direction is The data is transmitted twice from the data storage unit to the optical modulator, and is configured to be repeatedly exposed with pixel data for one line along the main scanning direction. In the pixel data for one line, If there is pixel data having a lower density than the set image density, the pixel exposed with the low-density pixel data sent for the second time is exposed with the same low-density pixel data sent for the first time. An image forming apparatus comprising: a timing control unit that shifts the timing of the second transmission of the low-density pixel data so as to be shifted from the pixel by a half pitch of the pixel pitch in the main scanning direction.