Position information input apparatus and method
First Claim
1. An apparatus for outputting position information corresponding to light having a cyclically varying intensity, said apparatus comprising:
- a detection device that receives the light, said detection device comprising a plurality of photoelectric conversion elements, arranged in a predetermined physical array;
difference signal generating means for generating, for each photoelectric conversion element, a difference signal corresponding to a difference between an output of the photoelectric conversion element when the light cycle is at a first point and an output of the photoelectric conversion element when the light cycle is at a second point, the first point being at a higher intensity than the second point;
threshold setting means for setting a threshold value on the basis of a level of said difference signal obtained from each photoelectric conversion element;
selection means for selecting effective photoelectric conversion elements by comparing said threshold value with the difference signal generated by said difference signal generating means; and
output means for outputting the difference signals corresponding to the selected effective photoelectric conversion elements.
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Abstract
The invention aims to provide a coordinate input apparatus having high detection reliability and high efficiency and to control the influence of ambient light using a simple structure. The apparatus detects a light spot flashing on and off in a predetermined cycle and incident at a desired position on a coordinate input screen, and includes a detection device having photoelectric conversion elements corresponding to N pixels for detecting a light spot coordinate. The difference between signals from photoelectric elements in light emission state and in light non-emission state at each N pixel is found, and the smaller of the difference signals of the m-th pixel having the maximum difference signal is set as a threshold value. Effective pixels are identified based on the threshold value, and the coordinate is calculated by using the difference data of the selected effective pixels.
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Citations
20 Claims
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1. An apparatus for outputting position information corresponding to light having a cyclically varying intensity, said apparatus comprising:
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a detection device that receives the light, said detection device comprising a plurality of photoelectric conversion elements, arranged in a predetermined physical array; difference signal generating means for generating, for each photoelectric conversion element, a difference signal corresponding to a difference between an output of the photoelectric conversion element when the light cycle is at a first point and an output of the photoelectric conversion element when the light cycle is at a second point, the first point being at a higher intensity than the second point; threshold setting means for setting a threshold value on the basis of a level of said difference signal obtained from each photoelectric conversion element; selection means for selecting effective photoelectric conversion elements by comparing said threshold value with the difference signal generated by said difference signal generating means; and output means for outputting the difference signals corresponding to the selected effective photoelectric conversion elements. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. An apparatus for outputting position information corresponding to light having a cyclically varying intensity, said apparatus comprising:
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a detection device that receives the light, said detection device comprising a plurality of photoelectric conversion elements, arranged in a predetermined physical array; difference signal generating means for generating, for each photoelectric conversion element, a difference signal corresponding to a difference between an output of the photoelectric conversion element when the light cycle is at a first point and an output of the photoelectric conversion element when the light cycle is at a second point, the first point being at a higher intensity than the second point; first threshold setting means for setting a first threshold value on the basis of a mean value of output of said difference signal obtained from each photoelectric conversion element; second threshold setting means for setting a second threshold value to either of the difference signals outputted by a photoelectric conversion element having the largest difference signal and two photoelectric conversion elements, which are equally spaced by the predetermined number of pixels from the photoelectric conversion element having the largest difference signal; selection means for selecting effective photoelectric conversion elements by comparing said first threshold value and said second threshold value with the difference signal generated by said difference signal generating means; and output means for outputting the difference signal obtained from the selected effective photoelectric conversion elements. - View Dependent Claims (15, 16)
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17. A method for controlling an apparatus for outputting position information corresponding to light having a cyclically varying intensity, comprising the step of:
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detecting by a detection device that receives the light, said detection device comprising a plurality of photoelectric conversion elements, arranged in a predetermined physical array; generating, for each photoelectric conversion element, a difference signal corresponding to a difference between an output of the photoelectric conversion element when the light cycle is at a first point and an output of the photoelectric conversion element when the light cycle is at a second point, the first point being at a higher intensity than the second point; setting a threshold value on the basis of a level of said difference signal obtained from each photoelectric conversion element; selecting effective photoelectric conversion elements by comparing said threshold value with the difference signal generated in said difference signal generating step; and outputting the difference signals corresponding to the selected effective photoelectric conversion elements.
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18. A method for controlling an apparatus for outputting position information corresponding to light having a cyclically varying intensity, comprising the step of:
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detecting by a detection device that receives the light, said detection device comprising a plurality of photoelectric conversion elements, arranged in a predetermined physical array; generating, for each photoelectric conversion element, a difference signal corresponding to a difference between an output of the photoelectric conversion element when the light cycle is at a first point and an output of the photoelectric conversion element when the light cycle is at a second point, the first point being at a higher intensity than the second point; setting a first threshold value on the basis of a mean value of output of said difference signal obtained from each photoelectric conversion element; setting a second threshold value to either one of the outputted difference signals of a photoelectric conversion element having the largest difference signal and two photoelectric conversion elements equally spaced by the predetermined number of pixels from the photoelectric conversion element having the largest difference signal; selecting effective photoelectric conversion elements by comparing said first threshold value and said second threshold value with the difference signal generated in said difference signal generating step; and outputting the difference signals obtained from the selected effective photoelectric conversion elements.
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19. A coordinate input apparatus for outputting position information corresponding to light having a cyclically varying intensity, said apparatus comprising:
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a detection device that receives the light, said detection device comprising a plurality of photoelectric conversion elements, arranged in a predetermined physical array; difference signal generating means for generating, for each photoelectric conversion element, a difference signal corresponding to a difference between an output of the photoelectric conversion element when the light cycle is at a first point and an output of the photoelectric conversion element when the light cycle is at a second point, the first point being at a higher intensity than the second point; threshold setting means for setting a threshold value on the basis of a level of said difference signal obtained from each photoelectric conversion element; selection means for selecting effective photoelectric conversion elements by comparing said threshold value with the difference signal generated by said difference signal generating means; and output means for outputting the difference signals corresponding to the selected effective photoelectric conversion elements.
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20. A coordinate input apparatus for outputting position information corresponding to light having a cyclically varying intensity, said apparatus comprising:
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a detection device that receives the light, said detection device comprising a plurality of photoelectric conversion elements, arranged in a predetermined physical array; difference signal generating means for generating, for each photoelectric conversion element, a difference signal corresponding to a difference between an output of the photoelectric conversion element when the light cycle is at a first point and an output of the photoelectric conversion element when the light cycle is at a second point, the first point being at a higher intensity than the second point; first threshold setting means for setting a first threshold value on the basis of a mean value of output of said difference signal obtained from each photoelectric conversion element; second threshold setting means for setting a second threshold value to either one of the outputted difference signals of a photoelectric conversion element having the largest difference signal and two photoelectric conversion elements equally by spaced the predetermined number of pixels from the photoelectric conversion element having the largest difference signal; selection means for selecting effective photoelectric conversion elements by comparing said first threshold value and said second threshold value with the difference signal generated by said difference signal generating means; and output means for outputting the difference signal obtained from the selected effective photoelectric conversion elements.
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Specification