Light spot position measuring apparatus having orthogonal cylindrical lenses

• US 5,642,164 A
• Filed: 02/21/1995
• Issued: 06/24/1997
• Est. Priority Date: 02/22/1994
• Status: Expired due to Fees

• Current Assignee: Kabushikikaisha Wacom
• Original Assignee: Kabushikikaisha Wacom
• Inventors: Ogawa, Yasuji
• Primary Examiner(s): GARBER, WENDY RAE
• Application Number:
  US08/391,128
• Time in Patent Office: 854 Days
• Field of Search: 348/335, 348/207, 356/400, 356/401, 356/375
• US Class Current: 348/335
• CPC Class Codes: G01B 11/00 Measuring arrangements characterised by the use of optical techniques

Abstract

A light spot position measuring apparatus includes a television camera for capturing an image of an object to be measured and an image processing unit. At least two cylindrical lens surfaces are provided in addition to an objective lens of the television camera so as to convert a light spot included in the object to be measured into linear images intersecting each other. The linear images are projected onto an image pickup face of the television camera which produces a corresponding image data. The image processing unit, processes the image data to extract corresponding straight lines. The unit further derives an intersection point of the straight lines and determines a position of the light spot in terms of the derived intersection point. The cylindrical lens surfaces have their cylinder axes which intersect each other. When a pair of the cylindrical lens surfaces having their cylinder axes intersecting orthogonal to each other are provided, a cross-shaped linear image is obtained. The cylindrical lens surfaces may be formed on a single lens or on separate lenses, respectively.

Claims

1. A light spot position measuring apparatus comprising:

optical conversion means for converting an incident light into a plurality of linear images intersecting each other;

image pickup means for receiving the linear images and producing corresponding image data; and

image processing means for processing the image data to derive a plurality of straight lines corresponding to the linear images and for deriving an intersection point of the straight lines to determine a position of a light spot from which the incident light emanates;

wherein said optical conversion means includes a plurality of cylindrical lens surfaces having cylinder axes intersecting each other so as to form said linear images.

2. A light spot measuring apparatus as set forth in claim 1;

wherein the plurality of cylindrical lens surfaces comprises two cylindrical lens surfaces having cylinder axes intersecting orthogonal to each other, so as to form cross-shaped linear images.

3. A light spot position measuring apparatus as set forth in claim 2;

wherein said cylindrical lens surfaces are formed on a single lens and wherein each of said cylindrical lens surfaces is divided in symmetry with respect to an optical axis of the lens.

6. A light spot position measuring apparatus according to claim 1;

wherein the optical conversion means converts incident light which emanates from a light spot included in an image of an object to be measured.

4. A light spot position measuring method comprising:

a conversion step for converting an incident light into a plurality of linear images intersecting each other using optical conversion means having a plurality of cylindrical lens surfaces having cylinder axes intersecting each other;

an image pickup step for receiving said linear images and producing corresponding image data; and

a deriving step for processing said image data to derive a plurality of intersecting straight lines corresponding to the plurality of intersecting linear images and deriving an intersection point thereof so as to determine a position of a light spot from which the incident light emanates.

5. A light spot position measuring method as set forth in claim 4;

wherein the optical conversion means used in the conversion step comprises a pair of cylindrical lens surfaces having cylinder axes intersecting orthogonal to each other so as to form cross-shaped linear images.

7. A light spot position measuring method according to claim 4;

wherein the conversion step includes converting incident light that emanates from a light spot included in an image of an object to be measured.

8. A light spot position measuring method using an optical converter which converts a light spot of an object to be measured into a plurality of linear images each extending substantially in one direction, using a two-dimensional image pick-up device which captures the linear images and produces corresponding image data, and using an image processing unit which processes the image data to derive a position of the light spot, the method comprising:

projecting the light spot onto the optical converter to convert the light spot into a plurality of linear images each extending substantially in the predetermined one-dimensional direction;

projecting the linear images onto the two-dimensional image pick-up device;

performing linear-approximation on the image data corresponding to the linear images to derive a plurality of corresponding straight lines; and

determining the position of the light spot based on a point of intersection of the straight lines.

9. A light spot position measuring method according to claim 8;

wherein the step of projecting the linear images includes the step of projecting the linear images using an optical converter having a plurality of intersecting cylindrical lens surfaces.

10. A method for determining the position of a light spot, comprising the steps of:

converting a light spot into a plurality of intersecting linear images using an optical converter;

providing an image pick-up device having a two-dimensional pixel array for receiving an image and producing corresponding image data;

setting up an orthogonal coordinate system relative to the pixel array, the coordinate system having a main axis and an auxiliary axis orthogonal thereto;

projecting the intersecting linear images onto the pixel array; and

processing the image data output by the image pick-up device in response to the projected linear image to perform linear approximation to determine a plurality of intersecting straight lines corresponding to the intersecting linear images and determining the location of the light spot by determining the point of intersection of the plural intersecting straight lines.

11. A method for determining the position of a light spot according to claim 10;

wherein the optical converter includes a plurality of intersecting cylindrical lens surfaces.

12. A method for determining the position of a light spot according to claim 10;

wherein the optical converter includes a plurality of cylindrical lenses having intersecting cylinder axes.

13. A method for determining the position of a light spot according to claim 10;

wherein the step of projecting the intersecting linear images is performed using an optical converter having symmetrically divided cylindrical lens surfaces, the cylindrical lens surfaces having cylinder axes which are orthogonal to each other.

14. An apparatus for determining the position of a light spot, comprising:

an optical converter for converting a light spot into a plurality of intersecting linear images and projecting the linear images;

an image pick-up device for receiving the projected linear images and producing corresponding image data; and

image processing means for processing the image data by performing a linear-approximation of the linear image to derive a plurality of intersecting straight lines corresponding to the intersecting linear images and for determining the location of the light spot in accordance with a point of intersection of the straight lines.