Shape measuring method and shape measuring apparatus
| Title: | Shape measuring method and shape measuring apparatus |
|---|---|
| Patent Number: | 8,681,341 |
| Publication Date: | March 25, 2014 |
| Appl. No: | 13/208692 |
| Application Filed: | August 12, 2011 |
| Abstract: | A shape measuring method includes guiding light emitted from a light source to an object to be measured and a reference surface, combining light reflected from the object to be measured with light reflected from the reference surface, and taking a distribution image of an interference light intensity corresponding to each measurement position of the object to be measured, while changing an optical path length difference between a first optical path length and a second optical path length over a whole scanning zone, sequentially storing distribution images of the interference light intensity in the whole scanning zone, and obtaining an interference light intensity string at each measurement position based on the stored distribution images of the interference light intensity, and obtaining a position in an optical axis direction at each measurement position of the object to be measured from a peak position of the interference light intensity string. |
| Inventors: | Goto, Tomonori (Sapporo, JP); Miyakura, Jyota (Kawasaki, JP); Asano, Hidemitsu (Kawasaki, JP); Saeki, Takeshi (Kawasaki, JP) |
| Assignees: | Mitutoyo Corporation (Kawasaki, JP) |
| Claim: | 1. A shape measuring method comprising: a first step of guiding light emitted from a light source having a broadband spectrum to an object to be measured and a reference surface, combining light reflected from the object to be measured with light reflected from the reference surface, and taking a distribution image of an interference light intensity corresponding to each measurement position of a measurement surface of the object to be measured, the interference light intensity changing in accordance with an optical path length difference between a first optical path length from the light source to the object to be measured, and a second optical path length from the light source to the reference plate; a second step of, while changing the optical path length difference between the first optical path length and the second optical path length over a whole scanning zone, sequentially storing distribution images of the interference light intensity of only a plurality of measurement zones which are partly set in the whole scanning zone; and a third step of obtaining an interference light intensity string which indicates a change of the interference light intensity due to a change of the optical path length difference at each measurement position based on the stored distribution images of the interference light intensity of the measurement zones, obtaining a peak position of the interference light intensity string in the whole scanning zone from the interference light intensity string, and obtaining a position in an optical axis direction at each measurement position of the object to be measured from the peak position. |
| Claim: | 2. The shape measuring method according to claim 1 , wherein, in the third step, an amplitude of each measurement zone at each measurement position is calculated from the interference light intensity string of each measurement zone at each measurement position, a curve is applied to the calculated amplitude of each measurement zone at each measurement position, and a peak position of the curve is obtained as the peak position of the interference light intensity string in the whole scanning zone at each measurement position. |
| Claim: | 3. The shape measuring method according to claim 1 , wherein, in the third step, a provisional peak position and a phase of a specific wavelength are calculated from the interference light intensity string of each measurement zone at each measurement position, and the peak position is calculated from the provisional peak position, a position of the measurement zone in the whole scanning zone, the specific wavelength and the calculated phase. |
| Claim: | 4. The shape measuring method according to claim 1 , wherein the position of the measurement zone in the whole scanning zone is made different depending on the measurement position. |
| Claim: | 5. The shape measuring method according to claim 1 , wherein an imaging region of the object to be measured is divided into a plurality of small regions, in the first step, a small region which is to be imaged is switched depending on a position in a scanning direction in the whole scanning zone, and, in the second step, a zone in which the small region is imaged in the first step is set as the measurement zone. |
| Claim: | 6. A shape measuring apparatus comprising: a light source having a broadband spectrum; an optical system configured to guide light emitted from the light source to an object to be measured and a reference surface, to combine light reflected from the object to be measured with light reflected from the reference surface, and to produce a distribution image of an interference light intensity corresponding to each measurement position of a measurement surface of the object to be measured, the interference light intensity changing in accordance with an optical path length difference between a first optical path length from the light source to the object to be measured, and a second optical path length from the light source to the reference plate; an imaging unit configured to image the distribution image of the interference light intensity output from the optical system; an optical path length changing unit configured to change the optical path length difference between the first optical path length and the second optical path length over a whole scanning zone; an image storing unit configured to sequentially store distribution images of the interference light intensity of only a plurality of measurement zones which are partly set in the whole scanning zone; and a calculating unit configured to obtain an interference light intensity string that indicates a change of the interference light intensity due to a change of the optical path length difference at each measurement position based on the distribution images of the interference light intensity stored in the image storing unit, obtain a peak position from the interference light intensity string, and to obtain a position in an optical axis direction at each measurement position of the object to be measured from the peak position. |
| Claim: | 7. The shape measuring apparatus according to claim 6 , wherein the calculating unit is configured to calculate an amplitude of each measurement zone at each measurement position from the interference light intensity string of each measurement zone at each measurement position, to apply a curve to the calculated amplitude of each measurement zone at each measurement position, and to obtain a peak position of the curve as the peak position of the interference light intensity string in the whole scanning zone at each measurement position. |
| Claim: | 8. The shape measuring apparatus according to claim 6 , wherein the calculating unit is configured to calculate a provisional peak position and a phase of a specific wavelength from the interference light intensity string of each measurement zone at each measurement position, and to calculate the peak position from the provisional peak position, a position of the measurement zone in the whole scanning zone, the specific wavelength and the calculated phase. |
| Claim: | 9. The shape measuring apparatus according to claim 6 , wherein an imaging region of the object to be measured which is to be imaged by the imaging unit is divided into a plurality of small regions, the imaging unit is configured to perform an imaging operation while switching a small region which is to be imaged, depending on a position in a scanning direction in the whole scanning zone, and the storing unit is configured to set a zone in which the small region is imaged by the imaging unit, as the measurement zone. |
| Claim: | 10. The shape measuring method according to claim 1 , wherein the distribution image of the interference light intensity is taken at only the plurality of measurement zones which are partly set in the whole scanning zone. |
| Claim: | 11. The shape measuring method according to claim 10 , wherein distribution images of interference light intensity of the whole scanning zone are not taken; and distribution images of interference light intensity of the whole scanning zone are not stored. |
| Claim: | 12. The shape measuring method according to claim 1 , wherein the interference light intensity string is calculated by using three or more interference light intensities at each measurement zone. |
| Claim: | 13. The shape measuring apparatus according to claim 6 , wherein the imaging unit is configured to image the distribution image of the interference light intensity output from the optical system at only the plurality of measurement zones which are partly set in the whole scanning zone. |
| Claim: | 14. The shape measuring apparatus according to claim 13 , wherein the imaging unit is not configured to image distribution images of interference light intensity output over the whole scanning zone; and the image storing unit is not configured to store distribution images of interference light intensity of the whole scanning zone. |
| Claim: | 15. The shape measuring apparatus according to claim 6 , wherein the calculating unit is configured to use three or more interference light intensities at each measurement zone to obtain the interference light intensity string. |
| Claim: | 16. The shape measuring method according to claim 1 , wherein the sequentially storing distribution images of the interference light intensity of only the plurality of measurement zones which are partly set in the whole scanning zone comprises sequentially storing distribution images of the interference light intensity at three or more measurement positions within each of the plurality of measurement zones which are partly set in the whole scanning zone, the plurality of measurement zones being set at spaced intervals from one another. |
| Claim: | 17. The shape measuring apparatus according to claim 6 , wherein the image storing unit is configured to sequentially store distribution images of the interference light intensity at three or more measurement positions within each of the plurality of measurement zones which are partly set in the whole scanning zone, the plurality of measurement zones being set at spaced intervals from one another. |
| Current U.S. Class: | 356/511 |
| Patent References Cited: | 5953124 September 1999 Deck 6501553 December 2002 Ogawa et al. 7119907 October 2006 Ge 7595891 September 2009 Tang 2002/0149781 October 2002 Harasaki et al. 2005/0078319 April 2005 De Groot 2007/0008551 January 2007 Tang 2009/0096980 April 2009 De Groot 2009/0109444 April 2009 Wan 2011/0098971 April 2011 Goto et al. 09-318329 December 1997 2006-068217 June 2006 |
| Assistant Examiner: | Hansen, Jonathan |
| Primary Examiner: | Chowdhury, Tarifur |
| Attorney, Agent or Firm: | Rankin, Hill & Clark LLP |
| Accession Number: | edspgr.08681341 |
| Database: | USPTO Patent Grants |
| Language: | English |
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