Illumination – Light fiber – rod – or pipe – Light emitting diode
Reexamination Certificate
2002-05-09
2004-09-07
Husar, Stephen (Department: 2875)
Illumination
Light fiber, rod, or pipe
Light emitting diode
C362S035000, C362S026000, C362S027000, C362S560000, C362S243000, C362S245000, C362S328000, C362S800000
Reexamination Certificate
active
06786626
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a linear light source device for image reading, such as a scanner, facsimile machine, multi-function office machine, and copy machine.
BACKGROUND OF THE INVENTION
The image reading device such as a scanner, facsimile machine, multi-function office machine, and copy machine etc. needs a linear light source to illuminate the targets. The method utilizes light emitting devices combined with a light-guided bar to guide the light into a linear light beam, thus illuminating the targets for image reading.
The current technology of the linear light source device for image reading are as follows: (1) utilize a cold cathode ray tube (CRT) for the linear light source
110
as shown in
FIG. 1
; (2) utilize a light-emitting diode (LED) array for the linear light source
120
as shown in
FIG. 2
; (3) utilize an LED array plus a prismatic lens for the linear light source
130
as shown in
FIG. 3
; (4) utilize a prismatic light-guided bar for the linear light source
140
as shown in
FIG. 4
; (5) utilize a prismatic light-guided bar plus housing for the linear light source
150
as shown in FIG.
5
A and
FIG. 5B
; (6) utilize a light-guided bar for the linear light source
160
,
170
,
180
, and
190
by a structure formed of the intersection of a prismatic column plane and an oblique plane as shown in
FIG. 6
,
FIG. 7
,
FIG. 8A
,
FIG. 8B
,
FIG. 9A
, and FIG.
9
B.
The above-mentioned linear light source
110
shown in
FIG. 1
is composed of a cold CRT
112
and a transfer circuit
114
. The luminescence of the cold CRT
112
is the same as that of the fluorescent tube (hot CRT) except that it is suitable for small tube diameters since it has the merits of being simple in structure and having a compact electrode. But this technology needs to have a transfer circuit provided, the overall size is relatively large, and as the cold CRT
112
is a cylindrical type of luminaire, the rate of light energy utilization is low and it is unable to generate light with different wave lengths. Besides, it is fragile and has a short service life.
As shown in
FIG. 2
, several LEDs
124
, such as forty pieces, are mounted on a substrate
122
. The rate of light energy utilization is low since the space angle of the radiation can be greater than a half of a space. Moreover, since spaces existed between the LEDs, and since it is inconsistent in luminous intensity, the light uniformity is poor. Further, since many LEDs
124
are required, the cost is high.
As shown in
FIG. 3
, many LEDs
124
, such as forty pieces, are mounted on a substrate
122
. A prismatic lens
132
is also provided. In contrast with
FIG. 2
, although the addition of this prismatic lens
132
improves the rate of light energy utilization and light beam uniformity, the rate of light energy utilization is still low. Besides, it has the disadvantage of being high in cost.
Another conventional technology is shown in FIG.
4
. The light is transmitted by the use of a prismatic light-guided bar
142
whose cross-section can be a circle, a rectangle, a triangle, an ellipse, or an irregular shape etc. The incident light
200
having an incident angle greater than the critical angle is transmitted into the light-guided bar
142
by total reflection without a loss in radiant flux, then goes through the light-guided bar
142
and exits out through the light-exiting plane to become exiting light beam
202
. Light falling on the stripe
144
and having an incident angle smaller than the critical angle, refracts from the stripes
144
of the surface to become out-refracting light
204
. In the meantime, in contrast with the surface with stripes, the light also falls on the smooth surface. Light beams having an incident angle smaller than the critical angle also refract from the smooth surface to become out-refracting light
206
. Since the light-guided bar
142
is merely a simple prismatic column and the surface stripes
144
are in simple belt-shape, the light uniformity is poor.
Another technology is shown in FIG.
5
A and
FIG. 5B. A
linear light source
150
is composed of a light-guided bar
152
, a light source assembly
300
, and a housing
158
. The cross-section of the light-guided bar
152
consisting of the prismatic column is a pentagon by cutting a corner of a rectangle or a polygon by cutting two or more corners of a rectangle. The plane formed by cutting an angle is a light-exiting plane
154
. The side surfaces other than the two neighboring side surfaces between the light-guided bar
152
and the light-exiting plane
154
are coated with reflective layers
156
(see FIG.
5
B). A housing
158
is provided, separated by a thin air layer, between the light-exiting plane
154
and at least a plane other than an end plane of the two end planes provided by a light source assembly
300
. This kind of technology increases the size of the device and the cost since the housing
158
is required. The device is apt to generate a light beam having an incident angle smaller than the critical angle. Moreover, the light beam reflected from the plane of the light-guided bar
152
allows only a portion to be reflected from the inner wall surface of the housing
158
and is then refracted back again into the light-guided bar
152
, thereby, the rate of light energy utilization is not high. Further, since the device depends merely on the reflective layers
156
to adjust the output radiant flux distribution, the uniformity is inadequate.
Another technology is shown in FIG.
6
and FIG.
7
. As shown in
FIG. 6
, a linear light source
160
is composed of a light-guided bar
162
and a light source assembly
300
. The cross-section of the light-guided bar
162
, constituted by the intersection of a prismatic column and an oblique plane, is a rectangle. Surface stripe
165
and reflective layers
166
are provided on an oblique surface
164
on the oblique plane, and the light-exiting plane is opposite to the oblique surface
164
.
In
FIG. 7
, the linear light source
170
is composed of a light-guided bar
172
and two-end light source assemblies
300
. As shown in
FIG. 7
, the light-guided bar
172
is constituted by the intersection of a prismatic column and an oblique plane. The cross-section of the prismatic column is a rectangle and the oblique plane has two oblique surfaces
174
. A light-exiting plane
178
is provided opposite to the oblique surfaces
174
. The remaining setups are the same as those in FIG.
6
. Since the cross-sections of the light-guided bars
162
and
172
are rectangles, light beams having incident angles smaller than the critical angle are easily generated. As a result, there is a loss of radiant flux, and the rate of light energy utilization is poor. Besides, since the device depends on the linear variation of oblique planes
164
, and
174
as well as the adjustment of the output radiant flux distribution, the light beam uniformity is poor.
In
FIGS. 8A and 8B
, a linear light source
180
is composed of a light-guided bar
182
and light source assemblies
300
positioned at both ends. The light-guided bar
182
is constituted by the intersection of a prismatic column and an oblique plane. The cross-section of the prismatic column is an irregular shape (see FIG.
8
B). The oblique planes are constituted by two pairs of two oblique surfaces
184
, of the light-guided bar
182
, inclined in opposite directions. The light-exiting planes
186
are other prismatic column planes of non-cylindrical planes. The surface stripes
188
are on the opposite side of the light-exiting plane
186
. Since the cross-section of the light-guided bar
182
is an irregular shape, light beams having incident angles smaller than the critical angle are easily generated. As a result, there is a loss of radiant flux, and the rate of light energy utilization is not high. Further, since the device depends on the linear-varied oblique surface
184
to adjust the output radiant flux distribution, the uniformity is inadequate.
In
FIGS. 9A and 9B
, a linear light source
190
is composed of
Pang Ming Jen
Wu Rong Yaw
Husar Stephen
Payne Sharon
Pixon Technologies Corp.
Rosenberg , Klein & Lee
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