Optical: systems and elements – Mirror – Plural mirrors or reflecting surfaces
Reexamination Certificate
2000-07-07
2003-11-18
Sikder, Mohammad (Department: 2622)
Optical: systems and elements
Mirror
Plural mirrors or reflecting surfaces
C359S858000, C359S859000, C359S861000
Reexamination Certificate
active
06648483
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an optical system for a scanner. More particularly, the present invention relates to a concave mirror optical system for a scanner.
2. Description of Related Art
Rapid progress in multi-media technologies has lead to great advances in image-processing devices. In a few years time, the black-and-white palm-top scanners has developed into full-color high-resolution scanner system that can display fine detail with added realism.
In general, scanning systems can be roughly divided into the reflective type and the transparent type. In the reflective scanning system, a document (made of non-transparent material) is placed on a transparent glass panel. Light transmitting through the transparent glass panel impinges upon the document. The light is reflected by the document into an optical system before delivering to an optical sensor such as a charge couple device (CCD) or a contact image sensor (CIS) to form a scan image. In the transparent scanning system, a document (made of transparent material such as a film negative or projector slide) is also placed on a transparent glass panel. However, light form a light source penetrates the document after passing through the transparent glass panel to form a scan image at the optical sensor.
FIG. 1
is a schematic cross-sectional view showing a conventional scanning system. To scan a non-transparent document
40
on a transparent glass panel
20
, the reflective scanning system is activated. A light source
38
on a sense carrier
30
aims a beam of light at the transparent glass panel
20
. The beam of light is reflected back by the document
40
and is channeled through a slit
34
into the sense carrier
30
. An optical system
36
(details not shown) inside the sense carrier
30
picks up the reflected light and transmits the light to an optical sensor
32
(a CCD or a CIS). Inside the optical sensor
32
, data encoded in the light beam is transformed into image data. Hence, an image line is scanned. As the sense carrier
30
moves forward along the transparent glass panel
20
, different swath of image comes into view. Each swath is captured by sequentially until image data of the entire document is captured. When the scanning system operates in the reflective mode, a light source carrier
10
above the glass panel
20
is stationary.
To scan a transparent document
40
, the transparent scanning system is activated. A light source
12
inside the light source carrier
10
produces a beam of light through a slit
14
and aims at the document
40
on the transparent panel
20
. After passing through the document
40
, the beam of light is channel through the slit
34
into the optical system
36
(detail not shown) of the sense carrier
30
. The light passes from the optical system
36
into the optical sensor
32
where data encoded in the light beam is converted to a line of image data. Hence, an image line is scanned. As the light source carrier
10
, and the sense carrier
30
moves forward along the transparent glass panel
20
, different swath of image comes into view. Each swath is captured sequentially until image data of the entire document is captured. When the scanning system operates in the transparent mode, the light source
38
on the sense carrier
30
does not emit any light.
FIG. 2
is a sketch of the optical system inside a conventional scanner. As shown in
FIG. 2
, the purpose of an optical system
136
is to capture light image produced by the document
40
and relay the light image to the optical sensor
132
. The optical system
136
includes at least a reflecting mirror
137
and a lens assembly
138
. The reflecting mirror
137
is used to change light travel direction while the lens assembly
138
is used for focusing the light onto the optical sensor
132
.
In a conventional scanner, a reflecting mirror
137
and a lens assembly
138
are generally used inside the optical system
136
. Hence, the optical system is structurally complicated and difficult to assembly, thereby increasing the production cost. Moreover, the lens assembly
138
may produce chromatic dispersion that may affect the image quality.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a concave mirror in the optical system of a scanner such that the concave mirror replaces the lens assembly in the conventional optical system.
A second object of this invention is to provide a concave mirror in the optical system of a scanner such that chromatic dispersion by the lens assembly of a conventional scanner is eliminated. In addition, simple material is used to form the concave mirror so that production cost is greatly reduced. Moreover, different magnifications can be obtained due to a difference in focusing power of the concave mirror along XY axis direction.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a concave mirror optical system for a scanner. Light is beamed to the first surface of a first concave mirror. The light is reflected from the first concave mirror to the first surface of a second concave mirror. The light is reflected again from the second concave mirror to the first surface of a second concave mirror. Light reflected from the second concave mirror is focused to a focus point. The receiving end of an optical sensor is positioned at the focus point so that the batch of light reflected from the second concave mirror is received.
This invention also provides a method of compensating the distorted image produced by a scanner. First, an image to be calibrated is provided. The difference in distance between a pixel on the image and a pixel on the actual image is computed. The values for calibrating pixel differences are stored. According to the stored pixel differences, the pixels in a distorted image are calibrated and the resulting image data after pixel correction are placed in memory.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 4572659 (1986-02-01), Omata
patent: 5071240 (1991-12-01), Ichihara et al.
patent: 5815310 (1998-09-01), Williamson
patent: 6231199 (2001-05-01), Li
patent: 6426506 (2002-07-01), Hudyma
patent: 6577443 (2003-06-01), Dinger et al.
J. C. Patents
Sikder Mohammad
Umax Data Systems Inc.
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