Incremental printing of symbolic information – Electric marking apparatus or processes – Electrostatic
Reexamination Certificate
1998-12-21
2001-02-13
Le, N. (Department: 2861)
Incremental printing of symbolic information
Electric marking apparatus or processes
Electrostatic
C347S237000
Reexamination Certificate
active
06188420
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to image forming apparatuses such as electrophotographic copying machines. Specifically, the present invention relates to an image forming apparatus including an array of photosensitive members that independently form a cyan image, a magenta image, a yellow image, and a black image, and thus form a color image as a result of a combination of these primary images.
2. Description of the Related Art
A known laser image forming apparatus for forming a color image has four arrays of electrophotographic photosensitive members and corresponding laser light sources as image exposure means. Oscillation of four laser light sources is controlled based on cyan, magenta, yellow and black image signals from an image to form four electrostatic latent images on the corresponding electrophotographic photosensitive members. These electrostatic latent images are developed and recombined to form the color image.
Laser beams from four laser light sources must be scanned so that four scanning beams are synchronized in the main and sub directions and thus cyan, magenta, yellow and black images are precisely recombined to form a color image free from color offset. It is, however, difficult to synchronize scanning of the four laser beams in the main and sub directions.
Another type of known color image forming apparatus has four electrophotographic photosensitive members and four LED light sources for forming cyan, magenta, yellow and black electrostatic latent images, in place of the laser light sources. In this apparatus, four scanning beams are relatively readily synchronized. On the other hand, a plurality of expensive LED chips are rearranged into four LED arrays in the apparatus (each LED array is referred to as a combined LED device), resulting in increased production costs of the apparatus. Since individual LED chips have different light emission characteristics, exposition by a combined LED device differs in the main scanning direction. Thus, image reproducibility is unsatisfactory in the main scanning direction.
In the color electrophotographic-copying machine, a combined LED device must be arranged for each of four electrophotographic photosensitive members. Since four combined LED devices also have different light emission characteristics as described above, it is even more difficult to precisely reproduce the original image.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an image forming apparatus, such as an electrophotographic copying machine, using combined LED devices as an exposure unit free from irregular light emission characteristics in the main scanning direction.
It is another object of the present invention to provide an image forming apparatus using combined LED devices that show significantly high luminance.
It is still another object of the present invention to provide an image forming apparatus in which driving lines and driving chips in a printer head are significantly decreased.
It is a further object of the present invention to provide an image forming apparatus having a significantly high process speed of electrophotographic copying.
A first aspect of the present invention is an image forming apparatus comprising a photosensitive member and an exposure means. The exposure means comprises a light-emitting device array including a plurality of light-emitting devices arranged in the main scanning direction to the moving direction of the photosensitive member; a switching device array including a plurality of switching devices connected to the light-emitting devices, said switching device array being divided into a plurality of groups; a first line group for connecting commonly to first terminals of switching devices of each of the groups; a second line group for connecting commonly to second terminals of switching devices of each of the groups; and a circuit for performing simultaneous light emission of said light-emitting device array to expose the photosensitive member.
A second aspect of the present invention is an image forming apparatus comprising a photosensitive member and an exposure means. The exposure means comprises a light-emitting device array including a plurality of light-emitting devices arranged in the main scanning direction to the moving direction of the photosensitive member; a switching device array including a plurality of switching devices connected to the light-emitting devices, the switching device array being divided into a plurality of groups; a first line group for connecting commonly to first terminals of switching devices of each of the groups a second line group for connecting commonly to second terminals of switching devices of each of the groups; and sample-and-hold circuits each being connected to each of the switching devices for performing simultaneously light emission of the light-emitting device array by simultaneous discharging of the charge held in the sample-and-hold circuits to expose the photosensitive member.
A third aspect of the present invention is an image forming apparatus comprising a photosensitive member and an exposure means. The exposure means comprises a light-emitting device array including a plurality of light-emitting devices arranged in the main scanning direction to the moving direction of the photosensitive member; a switching device array including a plurality of switching devices connected to the light-emitting devices, the switching device array being divided into a plurality of groups; a first line group for connecting commonly to first terminals of switching devices of each of the groups; a second line group for connecting commonly to second terminals of switching devices of each of the groups; and a plurality of light-emitting device array blocks having circuits for performing simultaneous light emission of the light-emitting device array; and a driving means for performing simultaneous light emission of one light-emitting device array block and for operating sequentially the plurality of light-emitting device array blocks.
Preferably, the light-emitting device has an organic light-emitting layer.
Preferably, photosensitive member is an electrophotographic photosensitive member. The electrophotographic photosensitive member may be an organic electrophotographic photosensitive member. Alternatively, electrophotographic photosensitive member may be an inorganic electrophotographic photosensitive member. Preferably, the inorganic electrophotographic photosensitive member comprises amorphous silicon.
The switching devices are preferably thin film transistors, wherein the first terminal is a gate terminal and the second terminal is a source terminal.
Preferably, the switching device array is formed into one chip.
The one-chip light-emitting device contributes to cost reduction of the light-emitting array section in an image forming apparatus and high color reproducibility in the main scanning direction. One-chip light-emitting device arrays made of a single substrate show substantially equal light-emitting characteristics and thus do not require calibration between these light-emitting device arrays.
The light-emitting device has significantly high luminance; hence the process speed of an electrophotographic copying machine using the light-emitting device is significantly increased. Further, the number of the driver ICs and the number of the wiring lines in the printer head are significantly decreased. Accordingly, the color copying machine can be produced with reduced material and production costs.
REFERENCES:
patent: 4265991 (1981-05-01), Hirai et al.
patent: 4356429 (1982-10-01), Tang
patent: 4539507 (1985-09-01), Van Slyke et al.
patent: 4720432 (1988-01-01), Van Slyke et al.
patent: 4769292 (1988-09-01), Tang et al.
patent: 4885211 (1989-12-01), Tang et al.
patent: 4950950 (1990-08-01), Perry et al.
patent: 5047687 (1991-09-01), Van Slyke
patent: 5059861 (1991-10-01), Littman et al.
patent: 5059862 (1991-10-01), Van Slyke et al.
patent: 5061617 (1991-10-01), Maskasky
patent: 5073
Koumura Noboru
Kuribayashi Masaki
Mashimo Seiji
Nagase Yukio
Narita Izumi
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Le N.
Nguyen Lamson D.
LandOfFree
Image forming apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image forming apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image forming apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2605259