2001 Fiscal Year Final Research Report Summary
Area expansion for aspherical shape measurement with phase-detection wavelength-scanning interferometry
| Project/Area Number |
12650259
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Intelligent mechanics/Mechanical systems
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| Research Institution | RIKEN (The Institute of Physical and Chemical Reseach) |
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Principal Investigator |
KATO Jun-ichi RIKEN, Opt. Eng. Lab., Senior Research Scientist, 光工学研究室, 先任研究員 (70177450)
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| Project Period (FY) |
2000 – 2001
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| Keywords | Optical profilometry / Waveiength-Scanning Interferometry / Phase-shifting Technique / Sub-Nyquist Interferometry / Digital Holography / Aperture-Synthetic Interferometry |
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| Research Abstract |
We investigated the new possibilities of the phase-detection wavelength-scanning interferometry (PWSI) with the concept of the sub-Nyquist interferometry, in which an external-cavity tunable laser diode and a PZT-mirror were used as the light source and the phase-shifter. With the present method, the profile measurements of various engineering surfaces including steps higher than the half-wavelength and specular aspheric forms are realized. Accuracy of this method has proved to be better than 50 nm with 8 nm of wavelength-excursion by experiments because the error sources of the PWSI, especially the influence of back-reflections by optics including the cover glass of the CCD chip, was successfully suppressed. Because this technique is based on pixel by pixel detection, the height measurement can also be conducted under the sub-Nyquist condition of fringe density, in which fringes spacing is less than a pitch of CCD pixel. The measurable area for aspherical surfaces can be extended more than twice by this feature, and it was shown that the complex shapes including the steps and aspherical form, such as the Fresnel lens, can be easily measured by the simulation researches. This technique is now extended to the multiple-aperture synthetic interferometry for profile evaluations of large optics. The present technique is also applied to the profilometry using the phase-shifting digital holography in which the phase-slope due to the wavelength-change is detected on the digitally reconstructed object surfaces, which might lead to more simplified and accurate shape measurement techniques.
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Research Products
(6 results)
