Method of determination of a three-dimensional profile of an object

• US 5,416,591 A
• Filed: 06/22/1993
• Issued: 05/16/1995
• Est. Priority Date: 06/25/1992
• Status: Expired due to Fees

• Current Assignee: Asahi Matsushita Electric Works Ltd. (Panasonic Holdings Corporation)
• Original Assignee: Asahi Matsushita Electric Works Ltd. (Panasonic Holdings Corporation)
• Inventors: Nakamura, Kuninori, Yoshimura, Kazunari
• Primary Examiner(s): Hille, Rolf
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US08/079,595
• Time in Patent Office: 693 Days
• Field of Search: 356/372, 356/376, 356/380, 356/386, 356/387, 250/332, 250/334
• US Class Current: 356/608
• CPC Class Codes: G01B 11/2518 Projection by scanning of the object

Abstract

A light beam is emitted to a target point on a target, so that the reflected light beam from the target point forms an illumination spot on a array sensor. The array sensor comprises a plurality of light receiving elements. The receiving elements are divided into a plurality of repeating units consisting of the same number of the receiving elements. The receiving elements in each of the repeating units are assigned respectively to different indexes. The receiving elements having the same index are commonly coupled so as to provide a single output indicative of the same index when the reflected light beam hits any one of the receiving elements. A method for determination of a three-dimensional profile of an object includes a first step of detecting a series of reference spots on the array sensor with respect to individual points obtained by scanning the light beam on a reference surface, and defining detection ranges respectively with respect to the individual reference spots, and a second step of detecting within the detection ranges a series of object spots obtained by scanning the light beam on an object surface and analyzing a positional deviation between the object spot and the corresponding reference spot within each of the detection range to determine the three-dimensional profile of the object in accordance with thus obtained positional deviations.

Claims

1. A method of determination of a three-dimensional profile of an object with a light source for emitting a light beam onto a target surface and an array sensor spaced by a distance from said light source for receiving the reflected light beam from said target surface;

said array sensor comprising a plurality of light receiving elements arranged in a row extending in the direction of following the reflected light beam, said light receiving elements being divided into a plurality of repeating units consisting of the same number of said light receiving elements, said light receiving elements in each of said repeating units being assigned respectively to different row indexes, said light receiving elements having the same row index being commonly coupled so as to provide a single row output indicative of the same row index when the reflected light beam hits any one of the light receiving elements having the same row index;

said method comprising the following first and second steps;

said first step comprising;

1) directing a first light beam from said light source onto a first point on a reference surface so that the reflected light beam from said first point forms on said array sensor a first illumination spot;

2) detecting the row index of said light receiving element corresponding to the first illumination spot and defining thus detected row index as a reference spot;

repeating the above proceedings

     1) and

     2) with respect to individual points formed by scanning the light beam onto the reference surface to obtain on said array sensor a series of reference spots corresponding to said individual points, so that each of said reference spots is related to specific one of the row indexes of said light receiving elements;

defining within said array sensor a series of detection ranges respectively for said individual reference spots in such a manner that each of said detection ranges includes corresponding one of said reference spots and extends over a limited number of said light receiving elements, said limited number being not more than the number of said light receiving elements in said repeating unit;

said second step comprising;

3) directing said first light beam onto a second point on a surface of the object disposed on the reference surface so that the reflected light from said second point on said object surface forms on said array sensor a second illumination spot;

4) detecting the row index of said light receiving element corresponding to the second illumination spot and defining thus detected row index as a detected spot which falls within the detection range corresponding to said reference spot obtained by said first light beam;

5) analyzing a positional deviation between said detected spot within the detection range and said reference spot obtained with respect to said first light beam to determine a position of the second point of said object surface relative to the reference surface; and

repeating the above proceedings

     3),

     4) and

     5) with respect to individual points formed by scanning the light beam onto said object surface to obtain a series of positions of the individual points on said object surface relative to the reference surface for determination of the three-dimensional profile of the object surface.

3. A method as set forth in claim 1 or 2, wherein said detection range is capable of being shifted in opposite directions along the row of said array sensor depending upon a surface configuration of said object surface intended to be scanned, while keeping the corresponding reference spot in said detection range.

4. A method as set forth in claim 1 or 2, further utilizing a shutter for shielding said light receiving elements other than said detection range intended to receive said reflected light beam from said object surface.

5. A method as set forth in claim 1, wherein said array sensors are arranged in plural rows in such a manner as to obtain a series of illumination spots spaced along the row of each array sensor when scanning the light beam in two mutually crossing directions over the target surface.

6. A method as set forth in claim 1, wherein a plurality array sensors are arranged in rows in such a manner as to obtain a series of illumination spots which are spaced along the row and are produced in the form of a slit straddling over the adjacent rows when scanning said light beam across the target surface.

7. A method as set forth in claim 5 or 6, wherein the light receiving elements designated by the same row index but belong to the different rows of said array sensors are commonly coupled to provide a single output indicative of the same row index.

8. A method as set forth in claim 5 or 6, wherein said plural array sensors are configured such that the light receiving elements which are designated by the same row index but belong to the different array sensors are coupled separately to provide different column outputs indicative of column positions of array sensors.

9. A method as set forth in claim 5 or 6, wherein said plural array sensors are divided into plural column groups each including a limited number of said array sensors, the light receiving elements in each of said column groups being assigned to different column indexes which are common among the plural column groups, said light receiving elements having the same column index being collectively coupled to provide a single column output indicative of a column position of the array within the column group, said column index being cooperative with said row index to locate the light receiving element in row and column within one of the column groups of the array sensors.

10. A method as set forth in claim 6, further utilizing a shutter for shielding said light receiving elements other than said array sensor including said detection range intended to receive said reflected light beam from said object surface.

11. A method as set forth in claim 1 or 2, wherein said light beam is scanned onto the target surface in such a manner that a direction of said light beam on a scanned point of the target surface is in parallel with that of said light beam on the next scanned point.

2. A method of determination of a three-dimensional profile of an object with the use of a light source for emitting a light beam onto a target surface and an array sensor spaced by a distance from said light source for receiving the reflected light beam from said object surface;

said array sensor comprising a plurality of light receiving elements arranged in at least two linear arrays each extending in a row along the direction of following the reflected light beam, said linear arrays disposed in side-by-side relation such that the reflected light beam forms an illumination spot which straddle over said linear arrays;

each of said linear arrays being divided into plural repeating units consisting of the same number of said light receiving elements;

each said light receiving element forming each one of said repeating units in a first one of said linear arrays being designated by a first value which is common within each unit but is different between the different ones of said units, such that said light receiving elements in the first array designated by the same first value are collectively coupled to produce a single first output indicating said first value when sensing the light beam,

the light receiving elements in each of said repeating units forming a second one of said linear arrays being designated respectively by second values which are different from each other within said repeating unit but are common to each other between the different units, said light receiving elements designated by the same second value in said second linear array being commonly coupled so as to provide a single second output indicating said second value when any one of the light receiving elements designated by the same second value senses the light beam; and

means for providing a row index in the form of a code comprising at least a first digit of said first value indicating which one of said light receiving elements in said first array provides said first output and a second digit of said second value indicating which one of the light receiving elements in said second array provides said second output.

said method comprising the following first and second steps;

said first step comprising;

1) directing a first light beam from said light source onto a first point on a reference surface so that the reflected light beam from said first point forms on said array sensor a first illumination spot;

2) detecting the row index of said light receiving element corresponding to the first illumination spot and defining thus detected row index as a reference spot;

repeating the above proceedings

     1) and

     2) with respect to individual points formed by scanning the light beam onto the reference surface to obtain on said array sensor a series of reference spots corresponding to said individual points, so that each of said reference spots is related to specific one of the row indexes of said light receiving elements;

defining within said array sensor a series of detection ranges respectively for said individual reference spots in such a manner that each of said detection ranges includes corresponding one of said reference spots and extends over a limited number of said light receiving elements, said limited number being not more than the number of said light receiving elements in said repeating unit;

said second step comprising;

3) directing said first light beam onto a second point on a surface of the object disposed on the reference surface so that the reflected light from said second point on said object surface forms on said array sensor a second illumination spot;

detecting the row index of said light receiving element corresponding to the second illumination spot and defining thus detected row index as a detected spot which falls within the detection range corresponding to said reference spot obtained by said first light beam;

5) analyzing a positional deviation between said detected spot within the detection range and said reference spot obtained with respect to said first light beam to determine a position of the second point of said object surface relative to the reference surface; and

repeating the above proceedings

     3),

     4) and

     5) with respect to individual points formed by scanning the light beam onto said object surface to obtain a series of positions of the individual points on said object surface relative to the reference surface for determination of the three-dimensional profile of the object surface.

12. A device for determination of a three-dimensional profile of an object, said device comprising:

a scanner for scanning a light beam across a target surface;

an array sensor spaced by a distance from said scanner for receiving the reflected light beam from said target surface through focusing lens means, said array sensor comprising a plurality of light receiving elements arranged in a row extending in the direction of following the reflected light beam, said light receiving elements being divided into a plurality of repeating units consisting of the same number of said light receiving elements, said light receiving elements in each of said repeating units being assigned respectively to different row indexes, said light receiving elements having the same row index being commonly coupled so as to provide a single row output indicative of the same row index when the reflected light beam hits any one of the light receiving elements having the same row index;

reference spot memory for storing a series of the row indexes obtained by a first step which comprises;

a1) directing a first light beam from said light source onto a first point on a reference surface so that the reflected light beam from said first point forms on said array sensor a first illumination spot;

a2) detecting the row index of said light receiving element corresponding to the first illumination spot and defining thus detected row index as a reference spot;

a3) repeating the above proceedings a1) and a2) with respect to individual points formed by scanning the light beam onto the reference surface to obtain on said array sensor a series of reference spots corresponding to said individual points, so that each of said reference spots is related to specific one of the row indexes of said light receiving elements;

detection range setting means for defining within said array sensor a series of detection ranges respectively for said individual reference spots in such a manner that each of said detection ranges includes corresponding one of said reference spots and extends over a limited number of said light receiving elements, said limited number being not more than the number of said light receiving elements in said repeating unit;

detected spot collecting means for obtaining a series of the row indexes by a second step which comprises;

b1) directing said first light beam onto a second point on a surface of the object on the reference surface so that the reflected light from said second point on said object surface forms on said array sensor a second illumination spot;

b2) detecting the row index of said light receiving element corresponding to the second illumination spot which falls within the detection range corresponding to said reference spot obtained by said first light beam; and

b3) repeating the above proceedings b1) and b2) with respect to individual points on said object surface by scanning the light beam to obtain on said array sensor a series of detection spots corresponding to said individual points, so that each of said detection spots is related to specific one of the row indexes of said light receiving elements;

analyzing means for determining a positional deviation between said detected spot and said reference spot based upon said row indexes obtained therefor within each of said detection ranges and for converting said deviation into a distance by which each of the scanned points on said object surface is spaced from said reference surface, therein providing the three-dimensional profile of the object surface.

13. A device as set forth in claim 12, wherein said array sensor is configured to have said light receiving elements elongated in a perpendicular direction to the row direction in which said light receiving elements are arranged in order to cover a wide scan range within which said illumination spot moves in said perpendicular direction.

14. A device as set forth in claim 12, wherein said focusing lens is a cylindrical lens having a convex which is curved along the direction of the array sensor in which said light receiving element are arranged.

15. A device as set forth in claim 12, further including a mirror disposed forwardly of said array sensor, and deflector means for deflecting said mirror in synchronism with the scanning of the light beam across the object surface in order to direct the reflected light beam to the array sensor while scanning the light beam across said object surface over a wide scan range.

16. A device as set forth in claim 12, wherein said focusing lens is disposed to have its optical axis perpendicular to the reference surface and wherein the number (M) of said repeating units is determined by the following equation:

space="preserve" listing-type="equation">M=m·

L/n·

R

wherein m is a magnification of the focusing lens;

L is a length of a field of view intended to be inspected;

n is the number of the light receiving elements in one unit; and

R is a pitch of the light receiving elements.