Optical waveguides – Noncyclindrical or nonplanar shaped waveguide
Reexamination Certificate
1998-03-04
2002-02-26
Lee, John D. (Department: 2874)
Optical waveguides
Noncyclindrical or nonplanar shaped waveguide
C362S558000, C385S031000, C385S901000
Reexamination Certificate
active
06351594
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a linear beam irradiator for irradiating the surface of an original sheet in the main scanning direction on an optical image reader, for example.
BACKGROUND OF THE INVENTION
A conventional linear beam irradiator is explained by taking an optical image reader as example for the sake of convenience.
In recent years, an optical image reader came to be widely used as for a reading unit for a facsimile, scanner, barcode reader, etc., and LED array realized by disposing LED chips in linear shape is used as original irradiating means of this kind of equipment.
FIG. 14
shows a structural drawing of a conventional optical image reader. In
FIG. 14
, the original sheet
51
(hereinafter referred to “original
51
”) is irradiated by a LED array
52
used as original irradiating means, and the light reflected on this original
51
is converged by a rod lens array
53
, and input in a photoelectric converting element array
54
, to be converted into an electric signal.
Here, the distance from the photoelectric converting element array
54
to the original
51
is usually 10 mm or so, and the respective rod lenses constituting the rod lens array
53
have a columnar shape of 0.6 &phgr;mm or so.
FIG. 15
indicates the construction of a conventional LED array, which is constructed by arranging a plural number of LED chips
62
linearly on a printed circuit board
61
forming the conductive layer of a circuit. Usually, 24 to 32 pieces of LED chip
62
are disposed on one printed circuit board. One piece of LED chip
62
has a length of about 2 mm, and the respective LED chips
62
are arranged at intervals of 5 mm or so.
Moreover, the Japanese patent laid-open publication No. 6-180009 discloses an original irradiating means of a construction realized by disposing a light source at both ends or at an end of a light conductor, to transmit the light from the light source through said light conductor. With this construction, it becomes possible to form a light diffusing area such as chopping wave surface, for example, on one side face in the longitudinal direction of the light conductor, so as to irradiate a concentrated linear beam from the other side face in the longitudinal direction.
By the way, while a original irradiating means works all right if only a linear light beam is obtained in the scanning direction, said construction using LED array has a defect of lowering the irradiation efficiency because the LED chips
62
also diffuse light in the subscanning direction respectively. Moreover, since the LED chips are provided at prescribed intervals, this not only produces deviation of illuminance on the surface of the original, requiring processing such as correction of shading, etc. but also deteriorates the image reading performance of the image reader itself even with such processing. Furthermore, in order to keep the deviations of illuminance on the surface of the original to a minimum, it is necessary to keep a certain distance between the original
51
and the LED array
52
, which would require a larger number of LED chips, expand the size of the unit itself and increase cost.
In addition, this interface of the chopping wave which is disclosed in the Japanese patent laid-open publication No. 6-180009 is covered with air of an index of refraction lower than that of the light conductor. Therefore, the light irradiated on said interface of the chopping wave among the light transmitting through the light conductor is totally reflected inside the light conductor to eventually go out from the other side face. However, since the entire light doesn't necesarily reflect back to the inside of the light conductor so a portion of light leaks to outside the light conductor, deteriorating the transmission efficiency.
The object of the present invention is to provide a linear beam irradiator capable of controlling deviation of illuminance on the surface of the original, without reducing the irradiation efficiency of the LED array. Another object is to provide a small-sized linear beam irradiator with shortened distance between the light irradiating surface and the original. Still another object is to provide a linear beam irradiator capable of drastically improving the transmission efficiency of light and sharply reducing the number of LED chips. Yet another object is to provide a low-cost linear beam irradiator.
SUMMARY OF THE INVENTION
To achieve said objects, the present invention adopts the following means: First, the present invention presupposes a linear beam irradiator comprising a light conductor
1
having light permeability, a light refraction & reflection area
2
provided on one side face in the longitudinal direction of said light conductor
1
and a light source on the surface at both ends of said light conductor
1
. By this construction, the light emitted from said light source gets into the light conductor
1
, is refracted or reflected in said light refraction & reflection area
2
, and goes out in the form of linear beam from the other side face in the longitudinal direction opposing said light refraction & reflection area
2
.
In said linear beam irradiator, the present invention is constructed by comprising said light refraction & reflection area
2
composed of a large number of interface of the chopping wave, and a diffusing surface
8
provided in a way to cover the light refraction & reflection area
2
. By this construction, the light which entered in the parts other than said light refraction & reflection area
2
of the light conductor
1
, is transmitted through the light conductor
1
while repeating total reflection on the inner face of this light conductor
1
, to eventually enter the light refraction & reflection area
2
and go out in the form of linear beam from the outgoing surface. At that time, since the light refraction & reflection area
2
is composed of a large number of interfaces of chopping wave, the light which entered the light refraction & reflection area
2
is reflected downward and goes out from the outgoing surface, thus going out efficiently. Moreover, even in the case where the light which entered said light refraction & reflection area
2
is transmitted through this light refraction & reflection area
2
, it is reflected back to the inside of the light conductor
1
by the diffusing surface
8
formed on the light refraction & reflection area
2
, and can form a linear beam efficiently.
If said diffusing surface
8
is disposed across a space (air layer, for example) not optically matching with said light refraction & reflection area
2
, the amount of light directly entering said diffusing surface
8
decreases and the efficiency improves.
The shape of said light conductor
1
is decided in such a way that the sectional area gradually diminishes from both ends toward the center. In this case, a light source is disposed at both ends of said light conductor
1
. Moreover, the shape of said light conductor
1
may also be decided in such a way that the sectional area gradually diminishes from one end toward the other. In that case, a light source will be disposed at an end of said light conductor
1
, and a light terminal
38
will be provided at the other end as construction.
The other side face in the longitudinal direction irradiating the light of said light conductor
1
must be a plane perpendicular to both end faces of said light conductor
1
. Thus the surface irradiated with light such as original paralles the other side face (light irradiating surface).
The sectional shape of said light conductor
1
can be circular, elliptical, etc. In the case where a light conductor
1
with an elliptical sectional shape is used, the light refraction & reflection area
2
is preferably disposed on the focal point on one side of the ellipsis. Moreover, said light conductor
1
may also have a sectional shape formed by combining
2
circles of different diameters. In that case, the circle with larger diameter will be furnished with the light transmitting function, while the circle with smaller
Murata Takahiko
Nakamura Tetsuro
Tanaka Eiichiro
Lee John D.
Matsushita Electric - Industrial Co., Ltd.
McDermott & Will & Emery
LandOfFree
Linear beam irradiator having a varying cross-sectional size does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Linear beam irradiator having a varying cross-sectional size, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Linear beam irradiator having a varying cross-sectional size will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2983002