Shape measuring device

• US 6,075,605 A
• Filed: 09/08/1998
• Issued: 06/13/2000
• Est. Priority Date: 09/09/1997
• Status: Expired due to Term

• Current Assignee: CKD Corporation, Kabushiki Kaisha Nextar
• Original Assignee: CKD Corporation, Kabushiki Kaisha Nextar
• Inventors: Shibata, Susumu, Okuda, Manabu, Futamura, Ikuo
• Primary Examiner(s): Pham, Hoa Q.
• Application Number:
  US09/149,138
• Time in Patent Office: 644 Days
• Field of Search: 356/375, 356/376, 356/374, 250/559.19, 250/559.22, 250/559.23, 250/559.24, 250/237 G, 382/203, 382/286, 348/132, 348/92
• US Class Current: 356/608
• CPC Class Codes: G01B 11/2518 Projection by scanning of the object

Abstract

A shape measuring device includes a light source for generating slit light beam and a polygon mirror for scanning the light beam and illuminating an object to be measured. The device further includes space-coding light beam controlling means, phase-shifting light beam controlling means, and a CCD camera which picks up an optical image of an object to be measured obtained by illumination of the light beam. The space-coding light beam controlling means controls light beam whose distribution of integrated illumination has a stripe patter in accordance with a predetermined code and the phase-shifting light beam controlling means controls light beam whose distribution of integrated illumination has a sine-wave like pattern. The distribution of integrated illumination intensity is possessed by the light beam illuminating within a time period for picking up one frame. With the picked up image information, space-coding shape operating means calculates a rough shape of the object to be measured, phase-shifting shape operating means calculates a precise shape of the object be measured, and then shape combining/operating means combines and calculates the shape of the object to be measured. Because the device combines a rough shape measured with wide range and a precise shape measured with high resolving power, the device can measure shape with wide dynamic range and with high resolution power.

Claims

1. A shape measuring device comprising:

light beam illuminating means for illuminating an object to be measured with a first set of light beams each having distribution of integrated illumination intensity of a stripe pattern in accordance with a predetermined code and with a second set of light beams having distribution of integrated illumination intensity of sine-wave like patterns in random order, said distributions of integrated illumination intensity being possessed, respectively, by the first and second sets of light beams illuminating within a time period for picking up one field or one frame;

pickup means for picking up, by an integrating pickup member, an optical image formed on a surface of said object to be measured by said light beams; and

image information operating means for calculating a shape of said object to be measured by operating image information of a plurality of fields or a plurality of frames outputted from said pickup means,

wherein said image information operating means calculates the shape of said object to be measured from space-coded image information and phase-shifted image information, said space-coded image information is obtained by illuminating said object to be measured with said first set of light beams in accordance with said predetermined codes thereof, and said phase-shifted image information is obtained by illuminating said object to be measured with the sine-wave like pattern of said second set of light beams.

2. The shape measuring device according to claim 1, wherein, assuming that 0<

J≦

1 where J is a numerical value, said first set of light beams and said second set of light beams have such a relationship that a subspace to which one space code number is given by said first set of light beams coincides with the subspace illuminated with J cycle of said sine-wave like patterns of said second set of light beams.

3. The shape measuring device according to claim 2, wherein said J is set to 1.

4. The shape measuring device according to claim 3, wherein, assuming that one of four types of sine-wave like patterns is expressed as IS₀ =cos θ

, the relationship between phases of said sine-wave like patterns and subspaces given space code numbers by said first set of light beams is selected so that borders between said subspaces are located at positions of ↓

=0, 2π

, 4π

, . . . .

5. The shape measuring device according to claim 2, wherein said J is set to 1/2.

6. The shape measuring device according to claim 5, wherein, assuming that one of four types of sine-wave like patterns is expressed as IS₀ =cos θ

, the relationship between the phases of said sine-wave like patterns and subspaces given space code numbers by said first set of light beams is selected so that the borders between said subspaces are located at the positions of θ

=-π

/2, π

/2, 3π

/2, . . . .

7. The shape measuring device according to claim 2, wherein said subspace, to which said one space code number is given and which is illuminated with said light beam of said J cycle of said sine-wave like pattern, is adapted to have an equal central angle of a generally fan-shaped cross section.

8. The shape measuring device according to claim 2, wherein a height from a reference plane perpendicular to an optical axis of said integrating pickup member to a center of illumination of said light beam is equal to the height from said reference plane to a principal point of an objective lens of said integrating pickup member, and

said subspace, to which said one space code number is given and which is illuminated with said light beam of said J cycle of said sine-wave like pattern, is adapted to have an equal width on said reference plane belonging to said subspace.

9. The shape measuring device according to claim 8, wherein said image information operating means includes:

means for operating an amount of space code number shift for calculating the amount of space code number shift for each pixel from space-coded image information and a reference space code number, said space-coded image information being obtained by illuminating said object to be measured with said first set of light beams, said reference space code number being observed by the pixels during illuminating said reference plane with said first set of light beams in the absence of said object to be measured;

means for operating an amount of phase shift for calculating the amount of phase shift for each pixel from phase-shifted image information and a reference phase, said phase-shifted image information being obtained by illuminating said object to be measured with said second set of light beams, said reference phase being observed by the pixels during illuminating said reference plane with said second set of light beams in the absence of said object to be measured; and

shape operating means for calculating the shape of said object to be measured from said amount of space code number shift and said amount of phase shift.

10. The shape measuring device according to claim 9, wherein said shape operating means includes means for operating an amount of combined phase shift/a shape, for calculating the shape of said object to be measured from the amount of combined phase shift obtained by combining, for each pixel, said amount of space code number shift and said amount of phase shift.

11. The shape measuring device according to claim 9, wherein said shape operating means includes:

means for operating an amount of space code number shift/a rough shape, for calculating the rough shape of said object to be measured from said amount of space code number shift;

means for operating an amount of phase shift/a precise shape, for calculating the precise shape of said object to be measured from said amount of phase shift; and

phase combining means for calculating the shape of said object to be measured by combining said rough shape and said precise shape.

12. The shape measuring device according to claim 2, wherein said image information operating means includes:

rough phase operating means for calculating, for each pixel, a rough phase equivalent to the phase of said second set of light beams of said sine-wave like pattern from said space-coded image information;

precise phase operating means for calculating a precise phase for each pixel from said phase-shifted image information;

combined phase operating means for calculating a combined phase for each pixel by combining, for each pixel, said rough phase and said precise phase; and

combined phase/shape operating means for calculating the shape of said object to be measured from said combined phase.

13. The shape measuring device according to claim 2, wherein said image information operating means includes:

space-coding shape operating means for calculating the rough shape of said object to be measured from said space coded image information obtained by illuminating said object to be measured with said first set of light beams;

phase-shifting shape operating means for calculating the precise shape of said object to be measured from said phase-shifted image information obtained by illuminating said object to be measured with said second set of light beams; and

shape combining/operating means for combining the rough shape calculated by said space-coding shape operating means and the precise shape calculated by said phase-shifting shape operating means and for calculating the shape of said object to be measured.

14. The shape measuring device according to claim 1, wherein said light beam illuminating means includes:

a light source for generating a single-slit light beam;

single-slit light beam scanning means for illuminating the surface of said object to be measured with said single-slit light beam and for deflecting/scanning said single-slit light beam;

space-coding light beam controlling means for controlling said single-slit light beam so that the integrated illumination intensity of said single-slit light beam illuminating within the time period for picking up one field or one frame is distributed like a stripe in accordance with a predetermined code; and

phase-shifting light beam controlling means for controlling said single-slit light beam so that the integrated illumination intensity of said single-slit light beam illuminating within the time period for picking up one field or one frame is distributed like a sine wave.

15. The shape measuring device according to claim 14, wherein said phase-shifting light beam controlling means controls how long said single-slit light beam is switched on while scanning a subarea on said reference plane and thereby adjusts the integrated illumination intensity in the subarea.

16. The shape measuring device according to claim 14, wherein said single-slit light beam scanning means allows said single-slit light beam to perform plural scans within the time period for picking up one field or one frame, and

said phase-shifting light beam controlling means controls how many times said single-slit light beam is switched on while scanning the subarea on said reference plane,

whereby the integrated illumination intensity in the subarea is adjusted.

17. The shape measuring device according to claim 16, wherein said single-slit light beam scanning means deflects/scans said slit light beam by a rotary polygon mirror.

18. The shape measuring device according to claim 14, wherein said single-slit light beam scanning means allows said single-slit light beam to perform plural scans during the time period for picking up one field or one frame, and

said phase-shifting light beam controlling means controls how long and how many times said single-slit light beam is switched on while scanning the subarea on said reference plane,

whereby the integrated illumination intensity in the subarea is adjusted.

19. The shape measuring device according to claim 18, wherein said single-slit light beam scanning means deflects/scans said single-slit light beam by the rotary polygon mirror.

20. The shape measuring device according to claim 14, wherein said phase-shifting light beam controlling means controls said single-slit light beam so that said single-slit light beam has the distribution of integrated illumination intensity in which the phases of said sine wave differ by 1/4 cycle in each field or each frame, and

said phase-shifting shape operating means calculates the precise shape of said object to be measured by the use of said phase-shifted image information of at least four fields or four frames differing from one another in the phases of said sine wave.

21. A shape measuring device comprising:

a light source for generating a single-slit light beam;

single-slit light beam scanning means for illuminating the surface of said object to be measured with said single-slit light beam and for deflecting/scanning said single-slit light beam;

phase-shifting light beam controlling means for controlling said single-slit light beam so that the integrated illumination intensity of said single-slit light beam illuminating within the time period for picking up one-field or one frame is distributed like a sine wave;

pickup means for picking up, by the integrating pickup member, the optical image formed on the surface of said object to be measured by said single-slit light beam; and

phase-shifting shape operating means for calculating the shape of said object to be measured from phase-shifted image information obtained by illuminating said object to be measured with a set of said single-slit light beam controlled by said phase-shifting light beam controlling means.

22. The shape measuring device according to claim 21, wherein the height from the reference plane perpendicular to the optical axis of said integrating pickup member to the center of illumination of said single-slit light beam is equal to the height from said reference plane to the principal point of the objective lens of said integrating pickup member, and

said phase-shifting light beam controlling means controls said single-slit light beam so that the distribution of integrated illumination intensity of said single-slit light beam illuminating said reference plane has a sine-wave like pattern of a constant wavelength on said reference plane.

23. The shape measuring device according to claim 21, wherein said phase-shifting light beam controlling means controls said single-slit light beam so that said single-slit light beam has the distribution of integrated illumination intensity in which the phases of said sine wave differ by 1/4 cycle in each field or each frame, and

said phase-shifting shape operating means calculates the shape of said object to be measured by the use of said phase-shifted image information of at least four fields or four frames differing from one another in the phases of said sine wave.

24. The shape measuring device according to claim 21, wherein said phase-shifting light beam controlling means controls how long said single-slit light beam is switched on while scanning the subarea on said reference plane and thereby adjusts the integrated illumination intensity in the subarea.

25. The shape measuring device according to claim 21, wherein said single-slit light beam scanning means allows said single-slit light beam to perform plural scans within the time period for picking up one field or one frame, and

said phase-shifting light beam controlling means controls how many times said single-slit light beam is switched on while scanning the subarea on said reference plane,

whereby the integrated illumination intensity in the subarea is adjusted.

26. The shape measuring device according to claim 21, wherein said single-slit light beam scanning means allows said single-slit light beam to perform plural scans during the time period for picking up one field or one frame, and

said phase-shifting light beam controlling means adjusts how long and how many times said single-slit light beam is switched on while scanning the subarea on said reference plane,

whereby the integrated illumination intensity in the subarea is adjusted.