Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2000-04-14
2002-12-31
Kim, Robert H. (Department: 2882)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S208100, C358S504000
Reexamination Certificate
active
06501087
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present inventions relate to an image reading apparatus for controlling the storage time of the reading means for banknote (bank bill) identification for each of the multiple wavelength light sources in an image reading apparatus using a multiple wavelength light source, and to a control method for the image reading apparatus.
2. Description of the Related Art
The prior art includes a banknote identification apparatus using an accumulation time control circuit as taught in Japanese Patent Publication (kokoku) No.8-12709. This banknote identification apparatus has a light emitting means for emitting two colors (two wavelengths) of light, a detection circuit for detecting the emission ratio of light from the light emitting means, and four photodetection circuits for detecting light reflected from the banknote. The absolute light quantity is controlled to a constant level and photodetection from the banknote is corrected based on the emission ratio of the two wavelengths of light to identify the banknote.
A problem with the above-noted conventional apparatus is that the banknote cannot be identified with good precision because of variation not only in the light quantity at the light emitting side, but also introduced by the photodetection elements and photodetection signal processing circuit. This is because the photodetector receives the two wavelengths to be detected mixed together, uses a filter to separate the wavelengths at the photodetection side, and instead of being a photodetector that receives reflected light from the actual medium, the photodetector corrects the actual detected light quantity using the detected light quantity of another photodetector.
The technology of a banknote identification apparatus such as described above typically uses light sources of multiple different wavelengths to read transmitted or reflected light as a means of detecting wrinkles and subtle soiling in the watermark of worn or soiled banknote. A problem in this case is that the sensitivity of the photodetection sensor varies according to the wavelength of the light source, and error based on the sensitivity difference results. Furthermore, depending upon whether the banknote being identified is over the sensor or not, the detected light quantity differs significantly when the detecting light passed through the banknote, and high gain is therefore required when reading the banknote. It is also necessary to switch the gain level, and error in conjunction with the degree of amplification occurs.
SUMMARY OF THE INVENTION
The present invention was conceived to resolve the above-mentioned problems. An object of the present invention is to provide an image reading apparatus using a multiple wavelength light source, and a control method therefor, whereby image reading operation (including the line sensor scanning operation and variations in the sensor system) can be always the same regardless of variations and differences between image readers, the control circuit can be simplified, and complicated processes such as setting various software process parameters for absorbing differences between the image readers can be avoided. A further object of the present invention is to eliminate error occurring in conjunction with sensitivity differences if the sensitivity of the photodetection sensor differs according to the wavelength of the light source.
The present invention relates to an image reading apparatus using a multiple wavelength light source and achieves the above noted object of the present invention by disposing a line shaped, a two-wavelength transmitting LED array and a line shaped light emitting/photodetecting part comprising a photodetector array and a two-wavelength reflecting LED array disposed in opposition such that a scanned medium passes between the two-wavelength transmitting LED array and light emitting/photodetecting part, said two-wavelength transmitting LED array and two-wavelength reflecting LED array emitting light of different wavelengths; an accumulation time control circuit disposed in a signal processing circuit of the photodetector array; and a control means for controlling light emission by the two-wavelength transmitting LED array and two-wavelength reflecting LED array, controlling scanning by the photodetectors, and controlling the accumulation time control circuit; wherein variations in wavelength detection sensitivity and light quantity with different read media are adjusted by means of the accumulation time of the accumulation time control circuit.
The above object is further achieved by disposing a line shaped, a two-wavelength transmitting LED array and a line shaped light emitting/photodetecting part comprising a photodetector array and a two-wavelength reflecting LED array disposed in opposition such that a read medium passes between the two-wavelength transmitting LED array and light emitting/photodetecting part, and a signal processing circuit for controlling an accumulation time of the photodetector array when the two-wavelength transmitting LED array and two-wavelength reflecting LED array emit light of different wavelengths.
In addition, the present invention relates to a control method for an image reading apparatus having a line shaped, a two-wavelength transmitting LED array and a line shaped light emitting/photodetecting part comprising a photodetector array and a two-wavelength reflecting LED array disposed in opposition such that a read medium passes between the two-wavelength transmitting LED array and light emitting/photodetecting part, and a signal processing circuit for controlling an accumulation time of the photodetector array when the two-wavelength transmitting LED array and two-wavelength reflecting LED array emit light of different wavelengths, and achieves the above object: by determining an accumulation time when there is no read medium after an automatic adjustment for correcting a rank indicative of the light emission efficiency class of the two-wavelength transmitting LED array, placing a white reference medium in the medium path, automatically adjusting a rank indicative of the light emission efficiency class of the two-wavelength reflecting LED array, determining the transmission/reflection accumulation time when a read medium is present is, and calculating a correction coefficient; by setting an accumulation time when there is no read medium and turning off the two-wavelength transmitting LED array and two-wavelength reflecting LED array to determine a dark output correction level when there is no read medium present, determining a dark output correction level, then turning on the two-wavelength transmitting LED array and two-wavelength reflecting LED array to determine a light emitting level, setting an accumulation time when there is a read medium present and turning off the two-wavelength transmitting LED array and two-wavelength reflecting LED array to determine a dark output correction level when a scanned medium is present, and determining a dark-output correction level and calculating a correction coefficient.
REFERENCES:
patent: 4319137 (1982-03-01), Nakamura et al.
patent: 4769532 (1988-09-01), Kawakami
patent: 6050387 (2000-04-01), Iwaki
patent: 6188080 (2001-02-01), Voser et al.
patent: 0 537 513 (1993-04-01), None
patent: 8-12709 (1996-02-01), None
Patent Abstract: Publication No. 06084041, published on Mar. 25, 1994; Application No. 04255659.
Patent Abstract: Publication No. 11086073, published on Mar. 30, 1999; Application No. 09245683.
Hayashi Masaaki
Koretsune Hideyuki
Glory Ltd.
Kim Robert H.
Ladas & Parry
Song Hoon K.
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