Incremental printing of symbolic information – Light or beam marking apparatus or processes – Scan of light
Reexamination Certificate
2000-03-09
2001-06-05
Le, N. (Department: 2861)
Incremental printing of symbolic information
Light or beam marking apparatus or processes
Scan of light
C347S234000
Reexamination Certificate
active
06243126
ABSTRACT:
BACKGROUND OF THE INVENTION
An image forming apparatus such as an electronic copying machine, facsimile, or printer forms an electrostatic latent image on the surface of a photosensitive drum serving as an image carrier by scanning that surface. The apparatus visualizes the electrostatic latent image with a developer mix (toner), and transfers the image onto a sheet.
A laser beam emitted by a laser diode strikes a galvanomirror, and is reflected by it to strike a polygon mirror. The laser beam having struck the polygon mirror strikes the polygon mirror, and is reflected by it to scan the surface of the photosensitive drum axially along the photosensitive drum as the polygon mirror pivots. Axial scanning of the photosensitive drum is called main scanning. This main scanning is repetitively executed with rotation of the photosensitive drum. The moving direction (direction perpendicular to the main scanning direction) of each main scanning repeated on the photosensitive drum is called a subscanning direction.
The laser beam position in the subscanning direction is important in forming a high-quality image, and can be adjusted by the galvanomirror. However, the laser beam position in the sub-scanning direction, which has been adjusted once, may vary owing to vibrations and the like.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide an image forming apparatus with high reliability that can always automatically adjust the laser beam position to an optimal position in a direction perpendicular to a scanning direction, thereby always forming a high-quality image with fine finish, and a method of controlling the apparatus.
According to the present invention, an image forming apparatus for scanning an image carrier with a laser beam emitted by a semiconductor laser, comprises
an adjuster for adjusting a position of the laser beam in a direction perpendicular to the scanning direction,
an optical unit for focusing onto one point part of the laser beam immediately before it scans the image carrier,
a photoelectric converter arranged at a position where the laser beam is brought to a focus by the optical unit, and
control means for controlling the adjuster in accordance with an output from the photoelectric converter.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFERENCES:
patent: 4870632 (1989-09-01), Shiono et al.
patent: 5396477 (1995-03-01), Matsumoto et al.
patent: 5883385 (1999-03-01), Takahashi et al.
patent: 5929891 (1999-07-01), Komiya et al.
patent: 5-66354 (1993-03-01), None
Foley & Lardner
Le N.
Pham Hai C.
Toshiba Tec Kabushiki Kaisha
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