Optical: systems and elements – Lens
Reexamination Certificate
1999-09-23
2001-09-04
Epps, Georgia (Department: 2873)
Optical: systems and elements
Lens
C359S754000, C359S757000
Reexamination Certificate
active
06285507
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is based on application No. H10-274659 filed in Japan on Sep. 29, 1998, the entire content of which is hereby incorporated by reference.
FIELD OF THE INVENTION
The present invention relates to a color image reading lens system (hereafter also referred to simply as “a lens system”), and, in one aspect, to a color image reading lens system, such as that which produces a reduced image of an original image, that is suitable for use in a color image reading apparatus, such as a digital copier, an image scanner, or an image reader.
BACKGROUND OF THE INVENTION
Conventionally-known color image reading apparatuses are mostly of the type that reads an original image by forming a reduced image thereof on an image sensor (for example, a Charge-Coupled Device (CCD)) through a focusing lens system. Such a color image reading apparatus typically employs a color image reading lens system composed of five or six lens elements that offers magnifications ranging from −¼× to −{fraction (1/10)}×. Moreover, color image reading apparatuses proposed in Japanese Published Patent Application No. H7-121047, Japanese Laid-open Patent Application No. H4-73711, and others are designed to perform color separation by means of a diffraction grating. Some commercially-available digital copiers are provided with a color-separating image reading optical system composed of seven lens elements and a reflection-type diffraction grating.
However, in the conventional color image reading apparatuses described above, a diffraction grating is employed merely as a color-separating element, and no arrangement has ever been known that takes advantage of the light-diffracting ability of a diffraction grating to correct aberrations.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a compact high-performance color image reading lens system in which chromatic and other aberrations are corrected properly by the light-diffracting ability of a diffraction grating.
To achieve the above object, according to one aspect of the present invention, an optical system for focusing an original image on an image sensor is provided with an optical element that is disposed at the image-sensor-side end of the optical system and which has a positive optical power as a whole, wherein at least one surface of the optical element has a positive optical power of diffraction.
According to another aspect of the present invention, an optical system for focusing an original image on an image sensor is provided with a first optical element and a second optical element. The first optical element is disposed at the image-sensor-side end of the optical system and has a positive optical power as a whole, wherein at least one surface of the first optical element has a positive optical power of diffraction. The second optical element is disposed on the original-image side of the first optical element and has a positive optical power as a whole, wherein at least one surface of the second optical element has a positive optical power of diffraction.
REFERENCES:
patent: 4435041 (1984-03-01), Torok et al.
patent: 5187358 (1993-02-01), Setani
patent: 6016229 (2000-01-01), Suzuki
patent: 6040943 (2000-03-01), Schaub
patent: 6122104 (2000-09-01), Nakai
patent: 4-73711 (1992-03-01), None
patent: 7-121047 (1995-12-01), None
Epps Georgia
Minolta Co. , Ltd.
Sidley Austin Brown & Wood
Thompson Tim
LandOfFree
Color image reading lens system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Color image reading lens system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Color image reading lens system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2455471