Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
2000-01-12
2001-06-19
Phan, James (Department: 2872)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C358S475000, C358S497000, C362S217060
Reexamination Certificate
active
06249368
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a light source module for optical scanner and particuarly to a light source module that is able to provide even luminosity for enhancing scanning quality.
BACKGROUND OF THE INVENTION
Optical scanner is widely used computer peripheral device which uses a light source module to provide light source to scan a document and uses a chassis to reflect document image to a charged couple device for converting the image to digital signals for computer process.
FIG. 1
illustrates a conventional scanner
1
which includes a document, board
2
, a chassis
3
, a transmission means
4
and a charged couple device (CCD)
5
The document board
2
is a rectangular and transparent member for holding a scanning document
6
thereon. The chassis
3
is located below the document board
2
and includes a plurality of reflection mirrors
31
, a lens
32
and a light source module
7
for emitting light ray to the document
6
. Image on the document
6
then is reflected to the reflection mirrors
31
and lens
32
which forms an image on the CCD
5
for converting to digital signals. The transmission means
4
drives the chassis
3
and CCD
5
moving reciprocally below the document board
2
to perform scanning operation.
FIG. 2
shows the light source module
7
used in the conventional scanner. It is engaged with the chassis
3
and moved synchronously with the chassis
3
. The light source module
7
includes a lamp socket
71
and a lamp tube
72
. The lamp socket
71
is a trough member having a length approximately same as the chassis
3
with an elongate opening
73
pointing toward the document board
2
. The lamp tube
71
is nested in the trough and being held at two ends (not shown in the figure). The trough has circular crosssection and has a reflective sheet
74
or material covering the internal surface. Light ray from the lamp tube
72
may emit directly to the document board
2
through the opening
73
and may also reflect from the reflective sheet
74
and project to the document board
2
to augment light luminosity on the document board
2
.
FIG. 3A
illustrates relationship between luminosity and distance of the lamp tube
72
. The lamp tube
72
may be considered as aggregation of many individual light spots. The middle portion of the lamp tube
72
has overlap light ray from the adjacent light spots and may result in greater luminosity. The two ends of the lamp tube
72
has less overlap light ray and will result in less luminosity. As a result, the photo electricity conversion in the CCD also will be affected. As shown in
FIG. 3B
, the middle portion of the CCD receives grater light intensity and will result in higher voltage while the two ends of the CCD will receive less light intensity and result in lower voltage. This phenomenon has greater impact on scanning quality. In order to remedy such problem, conventional approach is to coat or adhere a non-reflective material
75
on the reflective sheet
74
. The non-reflective material
75
is taper off at two ends so that the two ends will have greater reflective surface to compensate the smaller light emitting intensity of the lamp tube at two ends to get an evenly distributed luminosity and voltage (as shown in FIGS.
4
C and
4
D). The non-reflective material
75
may be one piece (as shown in
FIG. 4A
) or two pieces (as shown in FIG.
4
B).
However the conventional technique set forth above still has drawbacks, notably:
a. the trough for nesting the lamp tube is generally a circle or square in crosssection. It prones to produce random or mixed light emission and may result in poorer scanning quality.
b. The non-reflective material is either printed or glued on the reflective sheet. The printing method will create environmental pollution problem. The gluing method is a tedious process and costs higher.
All of these concerns have yet to be resolved.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a light source module for scanner that has an improved light gathering effect to reduce random light emission for achieving better scanning quality.
It is another object of this invention to provide a light source module that has a light shade integrally formed with the lamp socket for reducing cost and improving production efficiency.
The light source module according to this invention includes a lamp socket, a lamp tube and a light shade. The lamp socket has a parabola trough and an elongate opening pointing toward the document board. The lamp tube is held at the focal point of the parabola trough which may produce parallel reflection light rays and emitting through the opening to the document board. The random light effect thus may be reduced for getting improved scanning quality. The light shade is a curved shape member taper off at two ends to partly block the opening so that evenly distributed light emission may be obtained through the opening for achieving improved scanning quality.
REFERENCES:
patent: 3981575 (1976-09-01), Tanaka et al.
patent: 4473865 (1984-09-01), Landa
Dougherty & Troxell
Phan James
Umax Data Systems Inc.
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