Method and apparatus for measuring profile of three-dimensional object

• US 4,794,262 A
• Filed: 11/25/1986
• Issued: 12/27/1988
• Est. Priority Date: 12/03/1985
• Status: Expired due to Term

• Current Assignee: Yukio Sato
• Original Assignee: CADIX, Inc., Kazuo Araki, Yukio Sato
• Inventors: Sato, Yukio, Araki, Kazuo
• Primary Examiner(s): Westin, Edward P.
• Application Number:
  US06/934,834
• Time in Patent Office: 763 Days
• Field of Search: 250/560, 356/376, 356/377, 356/1, 358/107, 364/559
• US Class Current: 250/559.22
• CPC Class Codes: G01B 11/2518 Projection by scanning of the object

Abstract

A method of measuring the profile of a three-dimensional object including the steps of scanning the surface of the object to be measured with a slit-ray, forming an optical image of the surface of the object on an imaging plane of a nonscanning type two-dimensional image sensor which is composed of a plurality of mutually independent photosensors, measuring each time interval between a time when the slit-ray passes a predetermined point and a time when reflected rays are received by any of each of the plurality of mutually independent photosensors, storing each of the time intervals measured in separate memory means with a one to one correspondence between the position of each of the plurality of photosensors and each of the plurality of separate memory means and determining the profile from the time interval stored.

Claims

1. A method of measuring the profile of three-dimensional object comprising the steps of:

scanning the surface of an object to be measured with a measuring slit-ray;

forming an optical image of the surface of said object by means of said measuring slit-ray on an imaging plane of a non-scanning type two-dimensional image sensor which is composed of a plurality of mutually independent arrayed photosensors;

measuring each time interval between a first time when said slit-ray passes a predetermined point and a second time when reflected rays from said slit-ray scanning said object are received by any of each of said plurality of mutually independent arrayed photosensors;

storing each of said time intervals measured in predetermined ones of a plurality of separate memory means with a one to one correspondence between the position of each of said plurality of photosensors and each of said predetermined ones of said plurality of separate memory means; and

determining the profile from the time intervals stored in each of said predetermined ones of a plurality of separate memory means.

2. A method according to claim 1, wherein said measuring slit-ray strokes over said surface of said object to be measured at a constant angular velocity.

3. A method according to claim 1, wherein said object is scanned by said slit-ray by projecting a slit-ray from a laser source onto a constantly rotating polygonal mirror.

4. A method according to claim 3, wherein said time interval is measured by sensing when said slit-ray passes a predetermined point using a photosensor to generate a pulse, beginning counting a series of clock pulses with a counter means when said pulse is generated and determining a count in said counter when said reflected rays are received by any one of each of said plurality of photosensors.

5. A method according to claims 1, 2, 3 or 4 wherein said surface of said object to be measured is stroked over by at least two slit-ray beams which are radiated from different positions for scanning at different timings so as to reduce an unmeasurable area of a surface of said object to be measured which has a projection or recess.

6. An apparatus for measuring the profile of three-dimensional object comprising:

a means for scanning a surface of an object to be measured with a measuring slit-ray;

a non-scanning type two-dimensional image sensor which is composed of a plurality of mutually independent arrayed photosensors and which form an imaging plane onto which an optical image on the surface of said object is formed by reflected rays from said slit-ray scanning of said object;

means for measuring each time interval between a first time when said slit-ray passes a predetermined point and a second time when reflected rays from said slit-ray scanning said object are received by any of each of said plurality of mutually independent arrayed photosensors;

storing means for storing each of said time intervals measured in predetermined ones of a plurality of separate memory means with a one to one correspondence between the position of each of said plurality of photosensors and each of said predetermined ones of said plurality of separate memory means; and

a means for determining the profile of the object from the time intervals stored in each of said predetermined ones of a plurality of separate memory means.

7. An apparatus according to claim 6, wherein the group of said photosensors is composed of a group of M×

N picture element photosensors which is divided into sub-groups of picture element photosensors in accordance with the address of the row of said photosensors, and each of said sub-groups is selectively energized by a multiplexer to fetch a signal with one scanning of said slit-ray, this process being repeated M times.

8. An apparatus according to claim 6, wherein said slit-ray is scanned over the surface of said object at a constant angular velocity.

9. An apparatus according to claim 6, wherein said scanning means comprises a constantly rotating polygonal mirror and a laser source for projecting a slit-ray onto said constantly rotating polygonal mirror.

10. An apparatus according to claim 9, wherein said measuring means comprises a photosensor through which said slit-ray passes as it scans said object to generate a pulse, a source of clock pulses, a counting means for counting a series of clock pulses from said clock pulse generating means when said pulse is generated by said photosensor and a means for determining the count in said counter when said reflected rays are received by any of each of said plura1ity of photosensors.

11. An apparatus according to any of claims 6, 8, 9 and 10, further comprising at least two scanning means at different positions for scanning said object with two different slit-ray beams at two different timings so as to reduce an unmeasured area of a surface of said object to be measured.

12. An apparatus according to any of claims 6, 7, 8, 9, or 10 wherein said imaging plane and said photosensors are connected by optical fibers.

13. An apparatus according to claim 11, wherein said imaging plane and said photosensors are connected by optical fibers.