Photodetector, photosensing position detector, coordinate input device, coordinate input/output apparatus, and photodetection method
First Claim
Patent Images
1. A photodetector comprising:
- photoreceiving means for receiving a light beam that blinks a plurality of times per detection period and for converting the received light beam into an output signal; and
signal processing and controlling means for controlling the photoreceiving means so that the output signal, that is output in response to the received light beam per blinking cycle of the light beam, increases in strength as a blinking cycle count, increases in each detection period.
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Abstract
A photodetector includes a photoreceiving unit which receives a light beam that blinks a plurality of times per detection period and coverts the received light beam into an output signal. A signal processing and control unit controls the photoreceiving unit so that the output signal increases in strength as a blinking cycle count increases in each detection period.
49 Citations
18 Claims
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1. A photodetector comprising:
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photoreceiving means for receiving a light beam that blinks a plurality of times per detection period and for converting the received light beam into an output signal; and
signal processing and controlling means for controlling the photoreceiving means so that the output signal, that is output in response to the received light beam per blinking cycle of the light beam, increases in strength as a blinking cycle count, increases in each detection period. - View Dependent Claims (2, 3, 4, 5, 6)
wherein the signal processing and controlling means controls the photoreceiving means in response to a difference between a duration of time during which a lighting time of the blinking light beam overlaps the first electronic shutter time duration and a duration of time during which the lighting time of the blinking light beam overlaps the second electronic shutter time duration. -
3. A photodetector according to claim 1, wherein the signal processing and controlling means reduces a deviation between the lighting time in the blinking cycle and the first electronic shutter time duration as the blinking cycle count increases in each detection period.
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4. A photodetector according to claim 1, the signal processing and controlling means comprises control means which stops a signal addition and enlarging process in the signal processing and controlling means when a maximum value of a stored quantity of the output signal reaches a predetermined value.
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5. A photodetector according to claim 1, wherein the photoreceiving means and the signal processing and controlling means are formed of a ring CCD.
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6. A photodetector according to claim 2, wherein the frequency of the electronic shutter is switched to a same frequency as a frequency of the blinking light beam at a point at which a center of the lighting time of a blinking cycle coincides with a center of the first electronic shutter time duration.
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7. A photosensing position detector comprising:
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a line sensor, formed of pixels arranged in a line, for receiving a light beam that blinks a plurality of times per detection period;
signal processing and controlling means which controls the line sensor so that an output signal of the line sensor in response to the received light beam per blinking cycle of the light beam increases in strength as a blinking cycle count increases in each detection period; and
determining means which determines, as a photosensing position, a position of a pixel that results in a maximum value of the output signals. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16)
wherein the output signal is formed based on a difference between a charge that is photoelectrically converted and then stored throughout a duration of time during which a lighting time of the blinking light beam overlaps the first electronic shutter time duration and a charge that is stored photoelectrically converted and then stored throughout a duration of time during which the lighting time of the blinking light beam overlaps the second electronic shutter time duration. -
9. A photosensing position detector according to claim 8, wherein the signal processing and controlling means reduces a deviation between the lighting time in the blinking cycle and the first electronic shutter time duration as the blinking cycle count increases in each detection period.
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10. A photosensing position detection period to sensing position detector according to claim 7, the signal processing and controlling means comprises control means which stops a signal addition and storage process in the signal processing and controlling means when a maximum value of a stored quantity of the output signal reaches a predetermined value.
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11. A photosensing position detector according to claim 8, wherein the line sensor and the signal processing and controlling means are formed of a ring CCD.
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12. A photosensing position detector according to claim 8, wherein a frequency of the electronic shutter is set so that the lighting time in the blinking period equals the first electronic shutter time duration at a blinking cycle counter that falls within a range not more than a maximum number of blinking counts and not less than half the maximum number of blinking counts in each detection period.
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13. A photosensing position detector according to claim 8, wherein a difference between an overlapping duration of time of the lighting time for the first blinking cycle and the first electronic shutter time duration and an overlapping duration of time of the lighting time for the first blinking cycle and the second electronic shutter time duration is one-tenth the lighting time.
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14. A photosensing position detector according to claim 8, wherein the frequency of the electronic shutter is switched to a same frequency as the frequency of the blinking light beam at a point at which a center of the lighting time of the blinking cycle coincides with a center of the first electronic shutter time duration.
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15. A coordinate input device comprising a photosensing position detector according to one of claims 7 through 14, wherein the photosensing position detector detects a position of a light source that blinks, and converts the position of the light source into coordinates.
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16. A coordinate input/output apparatus comprising the coordinate input device according to claim 15 and a display device for displaying the coordinates of the light source.
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17. A control method of controlling a photodetector, comprising:
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a photosensing step of converting a light beam that blinks a plurality of times per detection period into an output signal, and a signal processing and controlling step of controlling the photosensing step so that the output signal in response to the received light beam per blinking cycle of the light beam increases in strength as a blinking cycle count increases in each detection period.
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18. A control method of controlling a photosensing position detector, comprising:
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a signal processing and controlling step which controls an output signal from a line sensor, formed of pixels arranged in a line, for receiving a light beam that blinks a plurality of times per detection period, so that the output signal in response to the received light beam per blinking cycle of the light beam increases in strength as a blinking cycle count increases in each detection period, and a determining step which determines, as a photosensing position, a position of a pixel that results in a maximum value of the output signal.
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Specification