Facsimile and static presentation processing – Facsimile – Picture signal generator
Patent
1998-06-25
2000-12-26
Lee, Cheukfan
Facsimile and static presentation processing
Facsimile
Picture signal generator
358483, 358474, H04N 104
Patent
active
06166832&
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a contact-type image sensor used in a facsimile machine, image scanner, photocopying machine and so on.
PRIOR ART
Contact-type image sensors are commonly used for reading characters, symbols and other forms of information recorded on a medium such as paper. An image sensor typically comprises an array of light emitting elements as a light source, and an array of light receiving elements. The light emitting element is typically a light emitting diode (LED) whereas the light receiving element is typically a CCD. In operation, light from the light emitting element array is directed to the information medium. The light reflected by the medium is sensed by the light receiving element array so that the image (information) on the object medium can be detected by photoelectric conversion.
Conventionally, a contact-type image sensor of the above type has an arrangement shown in FIG. 9 for example.
Specifically, a contact-type image sensor represented by the numeral code 10 has a substrate 12 provided on a bottom portion of a case 11. The substrate 12 has an array of image sensor tips 12 corresponding to a reading width. The case 11 has an upper surface attached with a transparent cover glass 14. Between the cover glass 14 and the image sensor chip array 13, and aligned with a predetermined reading line L, there is disposed a rod lens array 15 fitted to a support groove 18 formed in the case 11. The rod lens array 15 is known as the selfoc lens array, by which an image on the reading line L is projected as an erected isometric image on the image sensor chip array 13.
The case 11 also includes an inclined substrate 17. The inclined substrate 17 has a plurality of LED chips 16 as a light source from which light is cast to an object D obliquely through the cover glass 14. The object D is moved by a platen P for example while contacted to the cover glass 14.
According to the above contact-type image sensor 10, the LED chips as the light source should be mounted on the inclined substrate 17 instead of the substrate 12 at the bottom so that the object D can be lighted as efficiently as possible. For this reason, the two substrates 12, 17 must be mounted individually, which complicates assembling of the image sensor 10. Using two kinds of substrates 12, 17 increases the number of parts, makes an arrangement more complex, and hence increases cost.
Theoretically, it is possible to eliminate the inclined substrate 17, and mount the LED chips 16 on the bottom substrate 12 together with the image sensor chip array 13. Such an arrangement is not practical, however, because only a very small portion of the light from the LED chips 16 can reach the object D.
Further, with the above arrangement of the image sensor 10, the LED chips 16 are disposed at a higher position than are the image sensor chips 13, being closer to the object D. As a result, the light from each of the LED cannot adequately disperse widthwise (i.e. in the longitudinal directions of the image sensor chip array 13) before reaching the object D. Thus, if a distance between adjacent pair of LED chips 16 is large, quantity of light often becomes uneven widthwise of the object D. This problem may be solved by increasing the number of LED chips 16, disposing the LED chips closer to each other. However, this solution creates a new problem of increased cost due to the increased number of LED chips 16.
DISCLOSURE OF THE INVENTION
It is therefore an object of the present invention to provide a contact-type image sensor having a simple construction for easy assembly.
Another object of the present invention is to provide a contact-type image sensor in which quantity of light does not easily become uneven in the directions of scanning even with a small number of light sources.
According to a first aspect of the present invention, there is provided a contact-type image sensor comprising a common substrate provided with a plurality of light receiving elements and a light source, and a light guide for directing the light fr
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patent: 5434682 (1995-07-01), Imamura et al.
patent: 5579114 (1996-11-01), Imamura
patent: 5780840 (1998-07-01), Lee et al.
patent: 5859421 (1999-01-01), Onishi et al.
patent: 5949062 (1999-09-01), Matsumoto
Bednarek Michael D.
Lee Cheukfan
Pittman Shaw
Rohm & Co., Ltd.
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