Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
2000-03-31
2001-03-13
Phan, James (Department: 2872)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S205100, C359S216100
Reexamination Certificate
active
06201627
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improvements in an optical scanning device for scanning a subject medium.
2. Description of the Related Art
In recent years, with development of digital techniques and light sources, numerous high performance printing equipment and the like have been developed, wherein a light beam modulated according to image signals scans a subject matter, such as photographic pictures and printed matter (which is hereafter referred to as a scanning subject medium), that is sensitive to light to record an image on a paper. In such a printing equipment, the utilization is made of an optical scanning device to scan a scanning subject medium. This optical scanning device is, for typical example, configured such that a laser beam from a laser diode is repeatedly reflected and deflected by a rotary polygon mirror and further directed as a scanning beam to a subject medium through an f-&thgr; lens. Because deflection of the scanning beam by the polygon mirror causes defectiveness in the evenness of velocity of straight line motion of the scanning beam along a canning line on the scanning subject medium relative to a temporal change in rotational angle &thgr; of the polygon mirror, the f-&thgr; lens is employed. In order for the optical scanning device to avoid the defectiveness in the evenness of velocity of straight line motion of the scanning beam along a scanning line and keep the velocity of straight line motion of the scanning beam. As is known from, for example, Japanese Patent Publication No. 6-95176, the f-&thgr; lenses that is installed in this type of optical scanning device comprises a plurality of lens elements.
In light of the tendency toward small and light equipment and instruments, for business use or for personal use, there is a strong demand for small and light printers and, in the nature of course, small and light optical scanning devices. It is been a matter of concern how to realize small and light printers and optical scanning devices.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a compact optical scanning device.
The foregoing object of the present invention is accomplished by providing an optical scanning device for scanning a subject medium with a light beam spot that moves along a straight line on the subject medium, which comprised a scanning optical system installed in an generally rectangular box-shaped housing and includes at least a rotary polygon mirror and an f-&thgr; lens system for continuously varying movement of the scanning beam spot relative to a regular angle of rotation of an polygon mirror so as to scan over the subject medium at an even scanning speed. The f-&thgr; lens system comprises at least first and second lens elements and a reflection mirror located between the first and second lens elements which are arranged so as to turn an optical path of the an f-&thgr; lens system at an approximately right angle between the first and second lens elements and extend along at least two adjacent walls, for example a top wall and one of vertical side walls, of the generally rectangular box-shaped housing. The f-&thgr; lens system may further comprise a second reflection mirror disposed below the second lens element so as to reflect back the scanning beam toward a scanning subject medium.
The rotary polygon mirror is located near the top wall of the generally rectangular box-shaped housing so as to have a vertical axis of rotation and is housed in a dust proof chamber which ha an open top and an opening formed in one of side walls which a scanning beam passes through. This dust proof chamber is closed by closing the open top with a top cover of the generally rectangular box-shaped housing and fitting the first lens element directly into the opening of the side all. The reflection mirror is preferably located at a top corner between the top wall and the vertical side wall so that the optical path of the f-&thgr; lens system extends along the top wall and the side wall.
According to the optical scanning device thus structured, separate arrangement of the lens elements of the f-&thgr; lens system and the folded optical path of the f-&thgr; lens system guarantees an increased freedom of laying out a plurality of optical elements of the f-&thgr; lens system and the overall compactness of the optical scanning device. Moreover, although the f-&thgr; lens system has a relatively long optical path length, the folded optical path realizes a compact layout of optical elements of the f-&thgr; lens system and its associated optical systems.
The optical scanning system may be equipped with a scanning timing control optical system which is disposed behind the second reflection mirror of the f-&thgr; lens system for detecting either a start or an end of every line scanning of the scanning beam spot so as to provide a signal for synchronized scanning. The scanning timing control optical system comprises a reflection mirror located behind the second reflection mirror so as to reflect a scanning beam reflected by the second reflection mirror back to the second reflection mirror at every moment that the polygon mirror turns and changes its active reflection surface on which the laser beam impinges from one to another, and a light sensor located in position to receive the scanning beam reflected by the reflection mirror of the scanning timing control optical system and subsequently by the second reflection mirror to provide a synchronous signal.
According to the optical scanning device equipped with the scanning timing control optical system thus structured, the utilization is made of twice reflection of the scanning beam by the second reflection mirror of the f-&thgr; lens system before receiving the scanning beam by the light sensor, which provides a folded optical path of the scanning timing control optical system and is contributory to the overall compactness of the optical scanning device.
REFERENCES:
patent: 5673136 (1997-09-01), Inoue et al.
patent: 6104523 (2000-08-01), Ang
Ohno Mitsuhiro
Ori Tetsuya
Fuji Photo Optical Co. Ltd
Phan James
Young & Thompson
LandOfFree
Optical scanning device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical scanning device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical scanning device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2451339