Facsimile and static presentation processing – Facsimile – Picture signal generator
Reexamination Certificate
1999-04-26
2003-01-14
Lee, Cheukfan (Department: 2622)
Facsimile and static presentation processing
Facsimile
Picture signal generator
C358S497000
Reexamination Certificate
active
06507416
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an adjustable chassis for a scanner and particularly to an adjustable chassis with variable brightness for a charge coupled device to obtain an optimum image brightness to enhance scanning quality.
2. Description of the Prior Art
Scanner is a widely used peripheral device for a computer to capture and process document images.
FIG. 1
shows a conventional scanner
1
which includes a chassis
12
for this purpose.
FIG. 2
illustrates the detailed structure of the chassis in use. A document
2
is placed on a transparent document board
14
which is located above the chassis
12
. The chassis
12
includes a light source
121
, a reflection means
123
, a lens
125
and a Charge Coupled Device (CCD)
127
.
The light source
121
includes a lamp tube
1212
located in a curve-shaped chamber of a lamp holder
1214
for emitting light through a slot opening for scanning use. The length of the lamp tube
1212
is about the same of the width of the document board
14
.
The reflection means
123
is to direct the image light of the document
2
to the lens
125
. It generally includes at least one reflection mirror
1231
.
The lens
125
is a condensing lens which receives image light from the reflection means
123
and forms a real image at its focal point.
The CCD
127
is located at the focal point of the lens
125
to receive and convert the image light to digital signals for a computer (not shown in the figures) to process.
It is generally known that the scanning quality of the scanner is highly depends on the brightness of the image light of the document
2
projecting upon the CCD
127
. Brightness of the image light may be divided from 0 to 255 separated degrees with 0 represents least brightness and 255 represents most brightness. In general, brightness between 235 and 240 degree may result in best scanning quality. A chart in
FIG. 2
shows relationship of document
2
brightness against the position of the document
2
. The optimum brightness (i.e., between 235 and 240 degrees) may be obtained at a document displacement of about 5.5 mm.
However the chassis
12
usually has error more than 5.5 mm because of manufacturing problems and limitations. As a result, a conventional scanner rarely can provide the optimum brightness for the scanning document
2
, and thus result in not desirable scanning quality.
The causes of this deficiency includes the following:
a. The quality of the lamp tube
1212
is not stable or consistent. The power rate of each lamp tube
1212
has different error when produced. The brightness which the document
2
receives from the lamp tube
1212
is thus also different.
b. The light projection angle of the lamp tube
1212
against the document
2
is different. Small projection angle produces greater brightness while large projection angle produces weaker brightness. Every scanner has slightly different projection angle due to human factor when assembling the light source
121
in the scanner
1
. As a result, the brightness of the document
2
received is also different.
c. The reflection mirror
1231
has different reflecting angle resulting from human factor during assembly. This will also result in various brightness of image light reflecting by the reflection mirror
1231
.
In order to resolve the brightness variance problem set forth above, there is a design as shown in
FIG. 3
, which includes a dimmer
322
in the light source
321
. The dimmer
322
has a PLC (program logical circuit) to change the voltage of the light source
321
so that the brightness of the light source
321
may be changed from too high (such as the broken line C) or too low (such as the solid line A) to a desirable degree (dash line B). The addition of the dimmer
322
increases product complexity and cost. Furthermore it addresses only one of the factors mentioned above. Its effectiveness is thus not satisfactory.
SUMMARY OF THE INVENTION
In view of aforesaid disadvantages, it is therefore an object of this invention to provide a brightness adjustable chassis that includes a light source, a reflection means, a lens, a charge coupled device and a reflection mirror adjuster. While the construction of the chassis is largely like the conventional one set forth above, the reflection mirror adjuster may change the reflection angle of the reflection mirror so that the charge coupled device may received better brightness of light image to achieve better scanning quality.
It is another object of this invention to provide a brightness adjustable chassis that includes a light source, a reflection means, a lens, a charge coupled device and a lamp holder adjuster. The lamp holder adjuster may change the light projection angle of the light source upon the scanning document to obtain a desirable brightness for better scanning quality.
It is a further object of this invention to provide a brightness adjustable chassis that includes a light source, a reflection means, a lens, a charge coupled device and a light source adjuster. The light source adjuster may change the distance between the light source and the scanning document so that an optimum brightness may be obtained on the light image of the document for achieving better scanning quality.
REFERENCES:
patent: 3574469 (1971-04-01), Emerson
patent: 6147343 (2000-11-01), Christensen
patent: 6233063 (2001-05-01), Bernasconi et al.
Lee Cheukfan
Umax Data Systems Inc.
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