Optical position detecting unit, optical coordinate input unit and optical position detecting method employing a pattern having a sequence of 1's and 0's

• US 5,502,568 A
• Filed: 07/28/1994
• Issued: 03/26/1996
• Est. Priority Date: 03/23/1993
• Status: Expired due to Term

• Current Assignee: Wacom Co Limited (Wacom)
• Original Assignee: Wacom Co Limited (Wacom)
• Inventors: Yoichi, Hideo, Ogawa, Yasuji
• Primary Examiner(s): Gonzalez, Frank
• Assistant Examiner(s): VIERRA EISENBERG, JASON D
• Application Number:
  US08/281,129
• Time in Patent Office: 607 Days
• Field of Search: 250/221, 250/222.1, 345/175, 345/179, 345/182-183, 356/375, 356/373
• US Class Current: 356/620
• CPC Class Codes: G01D 5/34 the beams of light being detected by photocells
• CPC Class Codes: G06F 2203/0331 Finger worn pointing device
• CPC Class Codes: G06F 3/0325 using a plurality of light emitters or reflectors or a plurality of detectors forming a reference frame from which to derive the orientation of the object, e.g. by triangulation or on the basis of reference deformation in the picked up image
• CPC Class Codes: G06F 3/0428 by sensing at the edges of the touch surface the interruption of optical paths, e.g. an illumination plane, parallel to the touch surface which may be virtual sensing beam interruptions in a planar beam grid of an optical touch-screen G06F3/0421
• CPC Class Codes: G06V 30/228 of three-dimensional handwriting, e.g. writing in the air

Abstract

An optical position detecting unit is configured by an image pickup unit for detecting the intensity of light, a pattern member disposed in the front of the image pickup unit and on a light path of the light and having a specific pattern, and a signal processing unit for extracting information with respect to the distance in the direction of a normal line of a pixel array region of the image pickup unit between a light-emitting source and the image pickup unit on the basis of signals with respect to the specific pattern projected to the pixel array. A distance between the pattern member and the pixel array of the image pickup unit is required to be known in advance in order to extract the information with respect to the distance. By using only one image pickup unit, the distance to the light-emitting source can be calculated.

Claims

1. An optical position detecting apparatus comprising:

an input unit including a two-dimensional coordinate position detecting plane;

a position pointer having a point-like light emitting section for pointing at arbitrary positions on the two-dimensional coordinate position detecting plane;

a linear image pickup sensor including plural pixels arranged in a substantially straight line to define an image pickup surface for receiving light from the point-like light-emitting section;

a pattern disposed in front of the linear image pickup sensor at a position having a known distance, L, from the image pickup surface in a path of light emitted from the point-like light-emitting section, the pattern having a specific pattern including equi-spaced "1" and "0" code elements, parts of the specific pattern respectively corresponding to light emitting positions of the position pointer, one of the parts being projected onto the linear image pickup surface by light emitted from the point-like light-emitting section, the code elements extending in a direction parallel to a direction in which the pixels extend; and

a signal processing means for processing signals detected by the linear image pickup sensor, the detected signals being derived from the pixels in response to the pixels sensing an image of the part of a specific pattern projected onto the image pickup surface so positions of the code elements included in the image are obtained from the detected signals, the detected signals being combined in the signal processing means so;

(a) a distance in the image is determined by the obtained positions of the code elements, (b) an enlargement image ratio, m, is determined as a ratio of an interval between the code elements in the specific pattern and the determined distance, and (c) a distance from the point-like light-emitting section to the linear image pickup sensor along a line normal to the image pickup surface is determined in accordance with {m/(m-1)}xL.

2. An optical position detecting apparatus according to claim 1, wherein the signal processing means derives (d) the positions of the code elements including in the image from the signals derived from the plural pixels sensing the image in response to an indication of image center of gravity, and (e) a correspondence relationship between the positions of the code elements included in the image and the positions of the code elements on a straight line by a least square calculation technique, and (f) the enlargement ratio as an indication of a slope of the straight line.

3. An optical position detecting apparatus according to claim 2, wherein the specific pattern including the plural code elements has an M-sequence characteristic, and the signal processing means determines (g) a discrete coordinate based on a digital code obtained by the signals derived from the plural pixels sensing the image, and (h) a direction of light incident on the image pickup surface based on the discrete coordinate, an intercept of the straight line, and the known distance.

4. An optical coordinate input system comprising:

an optical position detecting apparatus including an input unit having a two-dimensional coordinate position-detecting plane, and a position pointer having a point-like light emitting section for pointing at arbitrary positions on the two-dimensional coordinate position detecting plane, said optical position detecting apparatus further comprising;

(a) a linear image pickup sensor including plural pixels arranged in a substantially straight line to define an image pickup surface for receiving light from the point-like light-emitting section;

(b) a pattern disposed in front of said linear image pickup sensor at a position of known distance, L, from the image pickup surface in a path of light emitted from the point-like emitting section, the pattern having a specific pattern including equi-spaced plural "1" and "0" code elements, parts of the specific pattern respectively corresponding to light emitting positions of the position pointer, one of the parts being projected onto the linear image pickup surface by light emitted from the point-like light-emitting section, the code elements extending in a direction parallel to a direction in which the pixels extend; and

(c) a signal processing means for processing signals detected by the linear image pickup sensor, the detected signals being derived from the pixels in response to the pixels sensing an image of the part of a specific pattern projected onto the image pickup surface so positions of the code elements included in the image are obtained from the detected signals, the detected signals being combined in the signal processing means so;

(i) positions of the code elements included in the image are determined from the detected signals, (ii) a distance in the image is determined by the obtained positions of the code elements, and (iii) an enlargement ratio, m, is determined by a ratio of the interval between the code elements in the specific pattern and the calculated distance, a distance from the point-like light-emitting section to the linear image pickup sensor along a line normal to the image pickup surface is determined in accordance with {m/(m-1)}xL.

5. An optical position detecting apparatus according to claim 4, wherein the signal processing means derives (iv) the positions of the code elements including in the image from the signals derived from the plural pixels sensing the image in response to an indication of image center of gravity, and (v) a correspondence relationship between the positions of the code elements included in the image and the positions of the code elements on a straight line by a least square calculation technique, and (vi) the enlargement ratio as an indication of a slope of the straight line.

6. An optical position detecting apparatus according to claim 5, wherein the specific pattern including the plural code elements has an M-sequence characteristic, and the signal processing means determines (vii) a discrete coordinate based on a digital code obtained by the signals derived from the plural pixels sensing the image, and (viii) a direction of light incident on the image pickup surface based on the discrete coordinate, an intercept of the straight line, and the known distance.

7. An optical coordinate input system according to claim 4, further comprising a display unit for displaying information with respect to coordinates of positions indicated by the position pointer, wherein a coordinate input surface on which the position pointer is operated is a display screen of the display unit.

8. An optical coordinate input system according to claim 4, further comprising a display unit for displaying information with respect to coordinates of positions indicated by the position pointer, the position pointer being adapted to be placed on a finger of an operator, and the display unit being adapted to display motions of the position pointer which moves with the finger.

9. An optical position detecting method comprising the steps of:

generating an image of a part of a specific pattern including plural equi-spaced "1" and "0" code elements having an M-sequence characteristic on an image pickup surface of an image pickup sensor in response to light from a point-like light-emitting means, the linear image pickup sensor being spaced from the pattern means by a known distance, L, the code elements extending parallel to a direction pixels in the image pickup surface extend;

deriving an indication of positions of the code elements included in the image of the part generated on the image pickup surface in response to the signals detected by the pixels of the image pickup sensor;

responding to the derived indications of the positions of the code elements to derive an indication of a distance included in the image;

responding to an indication of a ratio of the spacing between the code elements in the specific pattern and the determined distance to determine an enlargement ratio, m; and

responding to the determined indication of m and the known value of L to determine a distance between the point-like light-emitting means and the linear image pickup sensor along a normal line from the image pickup surface in accordance with {m/(m-1)}xL.

10. An optical position detecting method according to claim 9, further comprising the steps of:

determining the positions of the code elements included in the image from the signals derived from the plural pixels sensing the image by determining the sensed image center of gravity;

determining a correspondence relationship between the positions of the code elements included in the image and the positions of the code elements as a straight line by using a least square calculation method, and

determining the enlargement ratio from a slope of the straight line.

11. An optical position detecting method according to claim 10, further comprising the steps of:

determining a discrete coordinate based on a digital code resulting from the signals derived from the plural pixels sensing the part of the image;

determining a direction of incidence of the light on the image pickup surface based on the discrete coordinate, an intercept of the straight line, and the known distance; and

obtaining coordinate data of the positions indicated by the point-like light-emitting means based on said distance along the direction of the normal line and the direction of incidence of the light.