Facsimile and static presentation processing – Natural color facsimile – Scanning
Reexamination Certificate
2000-05-26
2004-10-05
Lee, Cheukfan (Department: 2622)
Facsimile and static presentation processing
Natural color facsimile
Scanning
C358S513000, C358S514000
Reexamination Certificate
active
06801345
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a color image sensor which is movable relative to a document at least in a secondary scanning direction for reading an image on the document. It also relates to an image reading apparatus incorporating such a color image sensor.
BACKGROUND ART
Among prior-art color image sensors, a serial type color image sensor is known which comprises wiring boards
51
,
57
, an array of light emitting diodes
52
, a prism
53
, lenses
54
,
56
, a mirror
55
, a semiconductor sensor
58
, and a flexible cables
59
,
60
, as shown in FIG.
31
. The light emitting diode array
52
comprises two green light emitting diodes
52
G, two blue light emitting diodes
52
B, and one red light emitting diode
52
R, as shown in FIG.
32
.
In such a prior-art serial type color image sensor, the red, the green and the blue light emitting diodes
52
R,
52
G,
52
B of the light emitting diode array
52
are selectively turned on in succession to emit light. The light is collected by the prism
53
to irradiate an image read surface
65
. The light reflected on the image read surface
65
is reduced by the lens
54
, and changes its direction at the mirror
55
to be directed to the lens
56
. The light is further reduced by the lens to be incident on a light receiving surface of the semiconductor sensor
58
. The semiconductor sensor
58
outputs a signal corresponding to the received amount of light to the outside via the wiring board
57
, the flexible cable
60
, and a non-illustrated connector. Signals for driving the light emitting diode array
52
is fed from the outside via the connector, the flexible cable
60
, the wiring board
57
and the flexible cable
59
. The semiconductor sensor
58
is supplied with electric power and various control signals from the outside via the connector, the flexible cable
60
and the wiring board
57
.
With such a prior-art serial type color image sensor, it is impossible to reliably collect light from the light emitting diode array
52
onto the image read surface
65
, because the prism
53
is not satisfactorily configured on sufficient study. Further, since the red, the green and the blue light emitting diodes
52
R,
52
G,
52
B are repetitively turned on in succession to read an image, the reading speed is low. Moreover, banding is likely to occur due to the temperature characteristics of the red light emitting diode
52
R. Furthermore, in such a reduction type optical system, the lenses
54
,
56
may cause image distortion, which also leads to banding. Highly accurate assembly is needed to solve this problem. Further, because of the complicated structure incorporating a large number of parts, there is a problem that the cost for the parts and assembly becomes unfavorably high.
On the other hand, among prior-art color image sensors, a contact type color image sensor is also known which includes an elongate transparent light guide member. Light from a light source enters the light guide member at an end surface thereof and is guided toward a read surface.
However, in such a prior-art contact type color image sensor, it is difficult to guide light from the light source to the read surface efficiently and evenly. To enhance the light-collecting efficiency and uniformity, a light guide member having a more complicated shape is necessary, and the assembly needs to be performed with high accuracy, which increases the parts cost.
DISCLOSURE OF THE INVENTION
The present invention, which has been conceived under the circumstances described above, has as an object to provide a color image sensor and an image reading apparatus which are capable of guiding light from the light source to a read surface efficiently and evenly. Another object of the present invention is to provide a serial type color image sensor and an image reading apparatus which are capable of providing a high reading speed, reducing banding, and reducing the manufacturing cost.
In accordance with a first aspect of the present invention, there is provided a color image sensor movable relative to a document at least in a secondary scanning direction for reading an image on the document comprising: a white light emitting diode for emitting white light; a generally sector-shaped prism having a shorter edge surface facing a white light emitting surface of the white light emitting diode, a longer edge surface facing a read surface of the document, a front and a rear surfaces spaced from each other in the thickness direction of the prism, the front and rear surfaces being so curved as to collect white light emitted from the white light emitting diode onto the read surface of the document; a semiconductor color sensor including a plurality of red light receiving elements, a plurality of blue light receiving elements and a plurality of green light receiving elements for receiving light reflected on the read surface and for simultaneously outputting red, blue and green image signals; and a lens means for forming a non-magnified erect image on the light receiving elements of the semiconductor color sensor in accordance with light reflected on the read surface.
According to a preferred embodiment, a single white light emitting diode, a single prism and a single semiconductor color sensor are provided, and the color image sensor is movable relative to the document both in a primary scanning direction and the secondary scanning direction for reading the image on the document.
Preferably, the lens means may comprise a rod lens array.
Preferably, the lens means may comprise a pair of convex lens arrays disposed in series in an optical axis direction.
Preferably, the white light emitting diode and the semiconductor color sensor may be mounted on a common wiring board.
Preferably, the color image sensor may further comprise a housing for accommodating the prism and the lens means, wherein the housing has a pair of first counterpart surfaces which face edge surfaces of the wiring board, respectively, and a pair of second counterpart surfaces which face edge surfaces of the white light emitting diode, respectively. A total spacing between the second counterpart surfaces of the housing and the edge surfaces of the white light emitting diode may be set smaller than a total spacing between the first counterpart surfaces of the housing and the edge surfaces of the wiring board. The white light emitting diode may be positionally limited by the second counterpart surfaces, thereby positioning the wiring board.
Preferably, the color image sensor may further comprise a transparent cover member provided between the read surface and each of the prism and the lens means, wherein the cover member may be integrally formed on the prism.
Preferably, the red light receiving elements, the blue light receiving elements and the green light receiving elements of the semiconductor color sensor may be respectively arranged at a predetermined pitch in a row extending in a primary scanning direction. The rows of red, blue and green light receiving elements may be spaced from each other at a predetermined pitch in the secondary scanning direction.
Preferably, the pitch between the rows of red, blue and green light receiving elements in the secondary scanning direction is twice the pitch between the light receiving elements of a same color in the primary scanning direction.
According to a second aspect of the present invention, there is provided an image reading apparatus incorporating the above-described color image sensor, wherein the red light receiving elements, the blue light receiving elements and the green light receiving elements of the semiconductor color sensor are respectively arranged at a first pitch in a row extending in the primary scanning direction, the rows of red, blue and green light receiving elements are spaced from each other at a predetermined pitch in the secondary scanning direction; the image reading apparatus comprising: a secondary scanning direction driving section for reciprocally moving the document and the color image sensor relative to each other at a second pi
Lee Cheukfan
Rohm & Co., Ltd.
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