Coordinate input apparatus and method, and storage medium

• US 6,229,601 B1
• Filed: 01/25/1999
• Issued: 05/08/2001
• Est. Priority Date: 01/30/1998
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Hasegawa, Masahide
• Primary Examiner(s): Buczinski, Stephen C.
• Application Number:
  US09/236,351
• Time in Patent Office: 834 Days
• Field of Search: 341/5, 356/141.2, 356/141.5, 356/400, 356/375
• US Class Current: 356/141.5
• CPC Class Codes: G06F 3/0386 for light pen
• CPC Class Codes: G06F 3/0425 using a single imaging device like a video camera for tracking the absolute position of a single or a plurality of objects with respect to an imaged reference surface, e.g. video camera imaging a display or a projection screen, a table or a wall surface, on which a computer generated image is displayed or projected tracking a projected light spot to determine a position on a display surface G06F3/0386

Abstract

This invention provides a high-resolving-power, compact, lightweight, low-cost coordinate input apparatus which suppresses the influence of disturbance light. Signals in light emission and non-light emission states of a light spot flashed by a designation unit in a predetermined cycle are detected by sensors of a coordinate detection unit, and separately integrated by an integration means to obtain a difference signal. The difference signal is input to a coordinate arithmetic means and digitized at a data width of n bits or more to perform coordinate calculation, thereby outputting a coordinate value having a resolving power about the nth power of 2 of the number of sensor pixels.

Claims

1. A coordinate input apparatus which irradiates a predetermined position on a coordinate input screen with light from a designation unit to form a light spot, and detects the light spot by a coordinate detection unit to generate a coordinate output signal corresponding to the predetermined position on the coordinate input screen, comprising:

light emitting control means, arranged in the designation unit, for flashing the light spot in a predetermined cycle;

integration means arranged in the coordinate detection unit and constituted by a sensor array prepared by aligning in a line a plurality of photoelectric conversion sensors for detecting the light spot, and a ring-like charge transfer portion for separately integrating signals in light emission and non-light emission states output in synchronism with the predetermined cycle of the light spot from the sensor array;

image sensing means arranged in the coordinate detection unit and having difference means for obtaining a difference signal from the signals in light emission and non-light emission states; and

coordinate arithmetic means for digitizing the difference signal between light emission and non-light emission states output from said image sensing means at a data width not less than n bits to perform coordinate calculation, thereby calculating a coordinate value having a resolving power substantially the nth power of 2 of the number of pixels of the sensor array.

2. An apparatus according to claim 1, wherein the coordinate detection unit further comprises:

detection means for detecting high-frequency flashing by the light spot; and

control means for controlling a timing of integrating operation by said integration means using the high-frequency signal detected by said detection means.

3. An apparatus according to either one of claims 1 and 2, wherein said image sensing means further comprises skim means for removing a predetermined number of electrical charges from transferred electrical charges.

4. An apparatus according to claim 3, wherein said coordinate arithmetic means further comprises integration control means for detecting that a peak level in the difference signal exceeds a predetermined value, thereby stopping integrating operation of said integration means.

5. An apparatus according to claim 4, wherein a width of an image of the light spot formed on said image sensing means is adjusted to be larger a width of a pixel of the photoelectric conversion sensor.

6. A coordinate input method comprising:

the light emission control step of irradiating a predetermined position on a coordinate input screen with light from a designation unit to form a light spot, and flashing the light spot in a predetermined cycle;

the detection step of detecting the light spot by a sensor array prepared by aligning a plurality of photoelectric conversion sensors in a line;

the integration step of separately integrating signals in light emission and non-light emission states output in synchronism with the predetermined cycle of the light spot from the sensor array by integration means formed from a ring-like charge transfer portion;

the difference step of obtaining a difference signal from the signals in light emission and non-light emission states which are integrated in the integration step;

the coordinate value arithmetic step of digitizing the difference signal at a data width not less than n bits to perform coordinate calculation, thereby calculating a coordinate value having a resolving power substantially the nth power of 2 of the number of pixels of the sensor array; and

the output step of outputting the coordinate value calculated in the coordinate value arithmetic step as a coordinate output signal corresponding to the predetermined position on the coordinate input screen.

7. A method according to claim 6, further comprising:

the detection step of detecting high-frequency flashing by the light spot; and

the control step of controlling a timing of integrating operation in the integration step using the high-frequency signal detected in the detection step.

8. A method according to either one of claims 6 and 7, wherein the integration step further comprises the skim step of removing a predetermined number of electrical charges from transferred electrical charges.

9. A method according to claim 8, further comprising the integration control step of detecting that a peak level in the difference signal exceeds a predetermined value, thereby stopping integrating operation in the integration step.

10. A method according to claim 9, wherein a width of an image of the light spot formed on the sensor array is adjusted to be larger a width of a pixel of the photoelectric conversion sensor.

11. A computer-readable storage medium which stores a program comprising:

a light emission control code for irradiating a predetermined position on a coordinate input screen with light from a designation unit to form a light spot, and flashing the light spot in a predetermined cycle;

a detection code for detecting the light spot by a sensor array prepared by aligning a plurality of photoelectric conversion sensors in a line;

an integration code for separately integrating signals in light emission and non-light emission states output in synchronism with the predetermined cycle of the light spot from the sensor array by integration means formed from a ring-like charge transfer portion;

a difference code for obtaining a difference signal from the signals in light emission and non-light emission states which are integrated by the integration code;

a coordinate value arithmetic code for digitizing the difference signal at a data width not less than n bits to perform coordinate calculation, thereby calculating a coordinate value having a resolving power substantially the nth power of 2 of the number of pixels of the sensor array; and

an output code for outputting the coordinate value calculated by the coordinate value arithmetic code as a coordinate output signal corresponding to the predetermined position on the coordinate input screen.

12. A coordinate input apparatus which detects a light source of a designation unit by a coordinate detection unit to generate a coordinate output signal corresponding to a predetermined position on a coordinate input screen, comprising:

light emitting control means, arranged in the designation unit, for flashing the light source in a predetermined cycle;

integration means, arranged in the coordinate detection unit, for separately integrating signals in light emission and non-light emission states output in synchronism with the predetermined cycle of the light source from a sensor array prepared a plurality of photoelectric conversion sensors for detecting the light source;

image sensing means arranged in the coordinate detection unit and having difference means for obtaining a difference signal from the signals in light emission and non-light emission states; and

coordinate arithmetic means for digitizing the difference signal between light emission and non-light emission states output from said image sensing means to perform calculation, thereby calculating a coordinate value having a resolving power higher than a number of pixels of the sensor array,

wherein said integration means is comprised of a ring-like charge transfer portion.

13. An apparatus according to claim 12, wherein said plurality of the photoelectric conversion sensors of the sensor array are aligned in a line.

14. An apparatus according to claim 12, wherein said coordinate arithmetic means digitizes the difference signal between light emission and non-light emission states output from said image sensing means at a data width not less than n bits to perform coordinate calculation, thereby calculating a coordinate value having a resolving power substantially the nth power of 2 of the number of pixels of the sensor array.

15. A coordinate input method which detects a light source of a designation unit by a coordinate detection unit to generate a coordinate output signal corresponding to a predetermined position on a coordinate input screen, comprising the steps of:

light emitting control step, arranged in the designation unit, for flashing the light source in a predetermined cycle;

integration step, arranged in the coordinate detection unit, for separately integrating signals in light emission and non-light emission states output in synchronism with the predetermined cycle of the light source from a sensor array prepared a plurality of photoelectric conversion sensors for detecting the light source;

image sensing step arranged in the coordinate detection unit and having a difference step for obtaining a difference signal from the signals in light emission and non-light emission states; and

coordinate arithmetic step for digitizing the difference signal between light emission and non-light emission states output from said image sensing step to perform calculation, thereby calculating a coordinate value having a resolving power higher than a number of pixels of the sensor array,

wherein said integration step is comprised of a ring-like charge transfer portion.

16. A method according to claim 15, wherein said plurality of the photoelectric conversion sensors of the sensor array are aligned in a line.

17. A method according to claim 15, wherein said coordinate arithmetic step digitizes the difference signal between light emission and non-light emission states output from said image sensing step at a data width not less than n bits to perform coordinate calculation, thereby calculating a coordinate value having a resolving power substantially the nth power of 2 of the number of pixels of the sensor array.