Illumination – Light fiber – rod – or pipe – Light emitting diode
Reexamination Certificate
2000-04-10
2002-03-19
Sember, Thomas M. (Department: 2875)
Illumination
Light fiber, rod, or pipe
Light emitting diode
C362S552000, C362S231000, C362S035000, C362S800000, C358S475000, C358S484000
Reexamination Certificate
active
06357903
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an illuminator of a line type to be used in or installed into an image reading apparatus for use in, for example, a facsimile machine, a copy machine, an image scanner, etc.
2. Description of Related Art
In machines such as facsimile machines, copy machines, image scanners, etc., as a device for reading a manuscript or image, there is applied an image reading apparatus, such as an image sensor, etc. Known types of image sensors are, for example, the reduced type, the close-contact type, the full-contact type, etc. Among them, image sensors of the contact type are normally constructed with an illuminator, an optical device of an equal power for imaging or equimultiple imaging, a sensor, and so on.
The image sensor of the close-contact type, in general, has a short light path, compared to that of the image sensor of the reduced type, thereby allowing for an apparatus of small size, and rendering unnecessary any troublesome optical adjustment, therefore there is a merit or advantage to such an image sensor in that it can be installed with ease into an apparatus. For these reasons, it has come to be applied in many apparatus, in the place of the reduced type.
The illuminator installed in the image sensor of the close-contact type must illuminate the surface of the manuscript with an intensity of illumination higher than that for enabling to read or pick up of images thereon by means of the sensor(s). The area to be illuminated by the illuminator is in a line-like shape. Specifically, it is very long in a main scanning direction (i.e., a longitudinal direction), while it may be very narrow in a sub-scanning direction thereof being orthogonal to the main scanning direction thereof. For example, in the illuminator for use in an A4 size machine which is applied to the facsimile apparatus, the length in the longitudinal direction must be 216 mm or longer. A further necessary attribute of the illuminator is uniformity of illumination. Unevenness in the illumination intensity on the surface of the manuscript, particularly in the longitudinal direction, may cause error(s) in reading of the image(s), therefore it is desirable for the intensity of illumination to be as uniform or even as possible.
As such the illuminator, conventionally, there is already known an illuminator of an LED array type, in which a few or several tens (for example, 30 pieces) of the LEDs (Light Emitting Diodes) are mounted on a printed circuit board by means of wire-bonding or soldering in a line. And, in the close-contact type image sensor being installed with such the illuminator therein, the light irradiated from the illuminator is incident upon the manuscript to be read after passing through a cover glass which functions also as a support for the manuscript, and then the light reflected from the surface of the manuscript is received by photoelectric transducer elements through a rod lens array, so as to be read as the image thereof.
In such the conventional apparatus, in which a large number of LEDs are aligned, the light being actually utilized in the process of sensing an image on a manuscript is only the portion which is incident upon a narrow reading line on the manuscript to be read, but the light falling outside of this portion is not utilized. Also, there is a method in which the illuminator is brought to be as close as possible to the manuscript to be read, to make the intensity of illumination of the line of the manuscript as bright as possible, thereby to reduce the number of the LEDs necessary to be installed, however in such a case there occurs a significant lack of evenness in the intensity of illumination. Also, in the illuminator having such a structure, there occurs a lack of evenness in the amount of light in a degree varying with a pitch of mounting of the LEDs. Further, inadequate uniformity may occur in the relative brightness of the individual LEDs used due to non-uniformity in the manufacturing thereof. Accordingly, if the number of the LEDs mounted onto an illuminator is reduced, the unevenness of the intensity and distribution of light emitted upon the reading line of the manuscript to be read becomes large.
In response to the above aspect of the design and manufacture of image reading apparatus, by the same inventors of the present invention there was proposed a technology according to which the light emitting elements (i.e., the LEDs) are provided at both end portions of a transparent body in a rod-like shape, and wherein a portion of surfaces of the transparent body is formed as a light scattering surface as, for example, in Japanese Laid-Open Patent No. Hei 6-148435 (1994) and Japanese Laid-Open Patent No. Hei 7-14414 (1995).
Since the light emitting elements are provided at both end portions of the transparent body of the rod-like shape in the line illumination apparatus disclosed in those publications, it is possible to eliminate one of the provided light emitting elements. The same inventors of the present invention also proposed a line illumination apparatus wherein the light emitting element is provided only at one end portion of the rod-like transparent body as, for example, in Japanese Laid-Open Patent No. Hei 8-163320 (1996) and Japanese Laying-Open Patent No. Hei 8-172512 (1996). The line illumination apparatus disclosed in those publications can obtain a reduction of cost by arranging the light emitting element only at the one end of the rod-like transparent body, and at the same time by making the shape of the light scattering pattern which is formed on the surface of the rod-like transparent body whereby the light irradiated from the light emitting elements expands from one end, upon which the light is incident, to the other end gradually, in the area of the light scattering pattern, for the purpose of obtaining an even or uniform illumination intensity along the longitudinal direction thereof.
Previously, in Japanese Laid-Open Patent No. Hei 7-183994 (1995), there was disclosed an image reading apparatus having an illumination means, which has at least two light sources each being different in the light emitting wavelength thereof, wherein the light sources are disposed with their alignments being shifted from a normal line passing through a center of a scattering and reflection region, so that the light comes to be incident in a uniform amount upon the scattering and reflection region, in the longitudinal direction thereof.
Further, the same inventors of the present invention disclosed the following, in Japanese Laid-Open Patent No. Hei 10-126581 (1998).
Namely, in a line type illuminator being provided with a light source at one end portion, the other end portion of a light guide being a rough surface, a light scattering pattern is devised so that the incident light is consumed as the illumination light until it reaches the other (non-emitting) end portion, thereby enabling that the illumination intensity may be maintained to be high and uniform.
However, with the line type illuminator mentioned in the above, inherent problems of reading of, in particular, a color manuscript, have not been studied.
Namely, when reading the color manuscript, the light emitting elements (for example, the LEDs), each emitting light at a different wavelength (for example, wavelengths corresponding to RGB), are energized one by one, so as to detect the intensity of reflection light in the respective wavelengths by means of sensors.
Taking the minimum light source for color into a consideration, there can be considered a light source constructed with three (3) LED chips, each having a different emission wave-length. There is a need of miniaturizing the image reading apparatus. Therefore, there is also the need of miniaturizing the line type illuminator for use therein.
If applying the above-mentioned light source constructed with the three (3) LED chips, each having the different emission wave-length, in the line type illuminator which is disclosed in the above-mentioned Japanese Patent Laid-Open No. 10-1
Furusawa Satoshi
Saito Tomihisa
Merchant & Gould P.C.
Nippon Sheet Glass Co. Ltd.
Sember Thomas M.
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