Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
2002-06-28
2004-09-14
Mouttet, Blaise (Department: 2853)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S249000, C377S039000
Reexamination Certificate
active
06791596
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for image forming, and more particularly to a method and apparatus for image forming that is capable of effectively generating pixel clock pulses without using an extremely high frequency clock pulse.
2. Discussion of the Background
FIG. 1
illustrates a typical structure of a background electrophotographic image forming apparatus such as a digital copying apparatus. The background image forming apparatus of
FIG. 1
includes a semiconductor laser unit
1
, a polygon mirror
2
, a scanning lens system
3
, a photosensitive member
4
, a photo-detector
5
, an image process unit
6
, a laser drive circuit
7
, a clock pulse generator
8
, and a phase sync circuit
9
.
In the background image forming apparatus of
FIG. 1
, a laser light beam emitted from the laser unit
1
is reflected in a continuous and cyclic manner by the rotating polygon mirror
2
and becomes a scanning beam. Then, the scanning beam is directed to the surface of the photosensitive member
4
with the scanning lens system
3
to form a beam spot thereon. With this beam spot, an exposure process relative to the surface of the photosensitive member
4
is performed and therefore an electrostatic latent image is generated on the surface of the photosensitive member
4
. In this process, the photo-detector
5
detects the scanning beam from line to line. The phase sync circuit
9
receives a clock pulse output from the clock pulse generator
8
and generates pixel clock pulses synchronized in phase from line to line with reference to the output from the photo-detector
5
. The phase sync circuit
9
sends the thus-generated pixel clock pulses to the image process unit
6
and the laser drive circuit
7
. In this way, the laser unit
1
controls a time period that the semiconductor laser emits laser light based on the image data generated by the image process unit
6
and the pixel clock pulses, synchronized in phase from line to line, and which is generated by the phase sync circuit
9
. Thereby, the laser unit
1
can control an electrostatic latent image to be formed on the surface of the photosensitive member
4
.
In the above-described optical scanning system, variations of distance between a deflective surface of a deflecting device such as a polygon mirror and a revolution shaft will cause the scanning beam to run on the surface of the photosensitive member at an undesired uneven scanning speed. Such an undesired uneven scanning speed will cause a jitter of an image and, as a result, an image quality is degraded. Therefore, correction for the scanning speed is needed to obtain a high image quality.
In a multiple beam optical system, a plurality of light sources may generate a plurality of laser beams with uneven oscillation wave lengths. In this case, an exposure displacement occurs particularly when the optical system does not correct a chromatic aberration of the scanning lens. Accordingly, when the beams spots generated by the laser light beams from the respective laser light sources run on the surface of the photosensitive member, the scanning widths will be different from each other. This also leads to a deterioration of an image quality and therefore the scanning widths are needed to be corrected.
For example, Japanese unexamined laid-open patent application publications, NO. 05-075199, No. 05-235446, No. 09-321376, No. 11-167081 and No. 2001-228415, describe background techniques for attempting to correct for the uneven scanning. These techniques basically are a frequency modulation method for changing a frequency of the pixel clock pulses to control a position of a light spot along the scanning line.
However, a circuit using such a frequency modulation method involves a complex control circuit for controlling pixel clock pulses and the complexness increases as the frequency modulation width becomes smaller. As a result, the circuit using the frequency modulation method cannot control the pixel clock pulses in a delicate manner.
SUMMARY OF THE INVENTION
This patent specification describes a novel pixel clock pulse generating apparatus for use in an image forming apparatus. In one example, this novel pixel clock pulse generating apparatus includes a high frequency clock pulse generator and a pixel clock pulse generator. The high frequency clock pulse generator generates relatively high frequency clock pulses. The pixel clock pulse generator receives phase data for instructing a transition time of pixel clock pulses and the relatively high frequency clock pulses generated by the high frequency clock pulse generator, and generates pixel clock pulses based on the phase data and the high frequency clock pulses.
This patent specification describes another novel pixel clock pulse generating apparatus for use in an image forming apparatus. In one example, this novel pixel clock pulse generating apparatus includes a high frequency clock pulse generator and a pixel clock pulse generator. The high frequency clock pulse generator generates relatively high frequency clock pulses. The pixel clock pulse generator receives phase data for instructing a transition time of pixel clock pulses and the relatively high frequency clock pulses generated by the high frequency clock pulse generator, and changes a frequency of pixel clock pulses based on the phase data and the high frequency clock pulses.
The transition time of pixel clock pulses may be synchronism with a transition time of the high frequency clock pulses.
In the above-mentioned pixel clock pulse generating apparatus, a frequency of the pixel clock pulses may be changed in steps of one clock cycle or a half clock cycle of the high frequency clock pulses.
This patent specification further describes another novel pixel clock pulse generating apparatus for use in an image forming apparatus. In one example, this novel pixel clock pulse generating apparatus includes a high frequency clock pulse generator, a counter, a comparator, and a controller. The high frequency clock pulse generator generates relatively high frequency clock pulses. The counter counts a number of the high frequency clock pulses generated by the high frequency clock pulse generator. The comparator compares the number of the high frequency clock pulses counted by the counter with phase data for instructing a transition time of pixel clock pulses. The controller performs a transition of a pixel clock pulse based on a result of comparison performed by the comparator.
The above-mentioned pixel clock pulse generating apparatus may further include a decoder for decoding the phase data and sending decoded data to the comparator.
The above-mentioned pixel clock pulse generating apparatus may further include a phase data memory for storing a plurality of phase data and sending the plurality of phase data in synchronism with the pixel clock pulses to the comparator.
The above-mentioned pixel clock pulse generating apparatus may further include a phase data memory and a decoder. The phase data memory stores a plurality of phase data and outputs the plurality of phase data in synchronism with the pixel clock pulses. The decoder receives the plurality of phase data output by the phase data memory, decodes the plurality of phase data, and sends the decoded phase data to the comparator.
The above-mentioned pixel clock pulse generating apparatus may further include a phase data memory and a synthesizer. The phase data memory stores a plurality of first phase data and outputs the plurality of phase data in synchronism with the pixel clock pulses. The synthesizer receives the plurality of first phase data output by the phase data memory and second phase data, synthesizes the plurality of first phase data and the second phase data, and sends synthesized phase data to the comparator.
The above-mentioned pixel clock pulse generating apparatus may further include a phase data memory, a synthesizer, and a decoder. The phase data memory stores a plurality of first phase data and outputs the plurality of phase
Ema Hidetoshi
Ishida Masaaki
Itabashi Akihisa
Nihei Yasuhiro
Mouttet Blaise
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
LandOfFree
Method and apparatus for image forming capable of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for image forming capable of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for image forming capable of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3232959