Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2000-08-07
2002-08-13
Allen, Stephone (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S208100, C250S234000, C250S239000
Reexamination Certificate
active
06433328
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a stray-light attenuating device. More particularly, the present invention relates to a stray-light attenuating device for a scanner.
2. Description of Related Art
Scanner is a common peripheral device in a computer system. Most platform type of scanners consists of a charge-coupled device (CCD) and a scanning drive system that commonly uses a stepping motor. In some applications, the CCD is fixed onto the scanning drive system so that a document is directly scanned. Alternatively, the CCD is fixed onto a stationary frame with light transmitted to the CCD via a set of optical lenses mounted on the scanning drive system.
In general, a CCD is able to take in a scanning line or a horizontal line of image data in each read operation. Each scanning line comprises of a plurality of pixels. Resolution of the scanning line depends on the density of CCD sensors. This type of resolution is commonly referred to as the horizontal resolution or the optical resolution. In the vertical direction, scanning is conducted through the driven CCD or driven optical lens system. Resolution is closely related to the step angle of the stepping motor and the accuracy of scanning drive system. This type of resolution is commonly referred to as the vertical resolution or the motor resolution. By conducting a vertical scanning, data from a number of horizontal lines are obtained. All line data can be subsequently combined to form a complete image.
Due to increasing demands for clearer image quality, scanners of higher resolution are always in need. In an image scanning operation, stray light is often one of the main causes of the lowering of signal power leading to poorer image resolution. Methods that can prevent the generation of stray light or remove any generated stray light is able to increase the signal-to-noise ratio and hence the quality of a scanner.
FIGS. 1 and 2
are cross-sectional side views of conventional stray-light attenuating devices in a scanner. As shown in
FIG. 1
, a plurality of stopping plates
114
is attached to the interior sidewalls of the scanner
100
. A light source
106
emits a beam of light onto a document
120
to produce a reflected light
110
. The light
110
is reflected by a reflecting mirror
108
to a lens
104
. The lens
108
focuses the reflected light
110
onto an optical sensor
102
to produce an image. The optical sensor
102
can be a charge-coupled device (CCD). Stray light
112
a
from the light source
106
is reflected by the reflecting mirror
108
to the stopping plates
114
. Stopping plates
114
is capable of dissipating stray light
112
a
, thereby serving as an isolator preventing any stray light
112
a
from passing through the lens
104
to the optical sensor
102
. However, the stopping plates
114
is rather useless for stopping the passing of stray light
112
b
through the gaps between stopping plates
114
into the lens
104
, thereby affecting image quality on the optical sensor
102
.
As shown in
FIG. 2
, an alternative method of eliminating stray light is to add a few stopping plates
214
a
~
214
c
between lens
204
and optical sensor
202
. The stopping plates
214
a
~
214
c
are attached to scanner
200
. The stopping plates are erected in such a way that the plates closer to the optical sensor
202
such as stopping plate
214
c
have a greater height than the plates further out such as stopping plate
214
a
. Although this arrangement of stopping plates is able to filter most of the stray light
212
b
, a portion of stray light
212
a
still disperses into the optical sensor
202
affecting the quality of the image.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a straylight attenuating device capable of preventing any stray light from entering charge-coupled device so that signal-to-noise ratio and hence quality of a captured image is increased.
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 straylight attenuating device for removing stray light from a scanner. The attenuating device includes a light source, a lens, a reflecting mirror, a light sensor, a front cover plate and a back cover plate. The light source provides a beam of light for illuminating a document on the scanner. Light from the light source impinges upon the document and reflects to the reflecting mirror. The reflecting mirror turns the reflected light to the lens. The lens focuses the reflected light onto the optical sensor to form an image. The optical sensor can be a charge-coupled device having at least a plurality of connecting leads, a sensing surface and a backside. The back cover plate having an opening thereon is used for covering the backside of the optical sensor. The front cover plate having a window thereon is used for covering the sensing surface of the optical sensor.
According to this invention, a front cover plate is mounted onto the sensing surface of the optical sensor. A window on the front cover plate permits only the reflected light necessary for forming the image into the optical sensor. Efficiency of removing the stray light is increased the closer the front cover plate is moved towards the optical sensor. Hence, the front cover plate is either glued to the optical sensor or fastened to the back cover plate using a set of screws for easy assembling.
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: 4644159 (1987-02-01), Miura
patent: 6097026 (2000-08-01), Tsai
Allen Stephone
J.C. Patents
Umax Data Systems Inc.
LandOfFree
Stray light attenuating 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 Stray light attenuating device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Stray light attenuating device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2887672