Facsimile and static presentation processing – Facsimile – Picture signal generator
Reexamination Certificate
1998-05-01
2001-06-26
Lee, Cheukfan (Department: 2722)
Facsimile and static presentation processing
Facsimile
Picture signal generator
C358S480000, C358S482000
Reexamination Certificate
active
06252682
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a document sensing device for an electrophotographic copier, printer, facsimile apparatus or similar image forming apparatus and, more particularly, to a document sensing device capable of reading the position and/or the size of a document with improved accuracy.
A copier, for example, has a function of automatically reading a document laid on its glass platen and selecting a sheet of the same size as the document. For this purpose, the copier includes a document sensing device for sensing the size of a document. The document sensing device has been proposed in various forms in the past. Japanese Patent Laid-Open Publication No. 7-77746, for example, teaches a document position sensor using a hologram disk and an LED (Light Emitting Diode). To reduce the influence of noise and enhance accurate reading, the document position sensor forms a beam spot of substantial size on a document. Light issuing from the LED is restricted and then incident to the hologram disk and diffracted for scanning a document. However, the problem with this scheme is that the wavelength of the light issuing from the LED spreads over a certain width. As a result, the hologram disk whose diffraction angle is noticeably dependent on wavelength causes the scanning beam to spread. This lowers the sensing accuracy of the device although reducing the influence of noise ascribable to dust and stains on a document.
An LED customarily included in the document sensing device has an emission area as broad as 0.3 mm×0.3 mm. Therefore, when light issuing from the LED is incident to a document via lenses and mirrors and then reflected toward a photodiode (PD), or photoelectric transducer, the beam width increases and therefore requires the PD to have a broad light-sensitive area. Consequently, much disturbing light is also incident to the PD and lowers the S/N (Signal-to-Noise) ratio.
Moreover, a copier or similar image forming apparatus including the document sensing device is usually operated in a room illuminated by, e.g., fluorescent lamps. In this condition, it is likely that the document sensing device fails to sense a document accurately due to disturbing light ascribable to the lamps.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 5-58511 and 6-242391.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a document sensing device capable of enhance accurate document sensing without increasing the cost.
It is another object of the present invention to provide a document sensing device capable of reducing the number of parts and therefore the cost.
It is still another object of the present invention to provide a document sensing device capable of sensing a document stably without being influenced by disturbing light ascribable to fluorescent lamps or similar illuminators.
In accordance with the present invention, a document sensing device includes a light source implemented by LED. A shaping element shapes light issuing from the light source to thereby form a narrow beam. A scanning section steers the beam with a rotating or a vibrating reflection member to thereby cause the beam to scan a document. An optical isolator separates light reflected from the document and returning an illumination path on an optical path. A condenser condenses the light separated by the optical isolator. A photoelectric transducer transforms the light condensed by the condenser to a corresponding electric signal. Au edge sensing device senses, based on the electric signal and the timing for scanning the document, the edges of the document to thereby determine the size and position of the document.
Also, in accordance with the present invention, a document sensing device includes a transparent glass platen to be loaded with a document, a cover plate openably covering the document laid on the glass platen, a scanning section for causing a Light beam to sequentially scan the underside of the cover plate and then the document, a light receiving portion for outputting, in response to light reflected from the document, a signal corresponding to the length of an incidence path, and a signal processing circuit for electrically processing the signal output from the light receiving portion to thereby binarize the signal The light receiving portion has a photosensor having at least four light-sensitive regions arranged symmetrically with respect to the center of the photosensor, a condenser adjoining the front of the photosensor on the optical axis of the photosensor for condensing incident light to a single point, and either a cylindrical lens or an optical wedge. The signal processing circuit includes at least one circuit for determining that signals derived from at least two symmetrical ones of the light-sensitive regions of the photosensor are different in strength.
Further, in accordance with the present invention, a document sensing device includes a light emitting portion for emitting light, and a light receiving portion for receiving a reflection from a document illuminated by the light issuing from the light emitting portion. The light receiving portion includes a condenser for condensing the reflection, a cylindrical lens to which light output from the condenser is incident, and a light receiving device for receiving light output from the cylindrical lens. The light receiving device has at least four light-sensitive regions so divided by lines as to be symmetrical with respect to the center of the light receiving device. The lines are perpendicular or parallel to a direction in which the light scans the document.
REFERENCES:
patent: 4778272 (1988-10-01), Asakura
patent: 4899227 (1990-02-01), Yamada
patent: 5214294 (1993-05-01), Toyofuku
patent: 5289262 (1994-02-01), McConnell
patent: 5321273 (1994-06-01), Kamiyama et al.
patent: 5479274 (1995-12-01), Baba et al.
patent: 5729024 (1998-03-01), Baba et al.
patent: 5818062 (1998-10-01), Baba et al.
patent: 8-179442 (1996-07-01), None
Abstract of European patent appln. No. 98-107943.7 filed Apr. 30, 1998.
Aoki Sumiaki
Baba Nobuyuki
Kudo Koichi
Dickstein , Shapiro, Morin & Oshinsky, LLP
Lee Cheukfan
Ricoh & Company, Ltd.
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