Studies on digital holography for aspheric surface measurement
Digital holography is fast becoming a generalized technique for 3D precision measurement. By numerical reconstruction and propagation of a digital hologram, the optical field from an object and thus the amplitude and phase can be quantitatively reconstructed. The quantitative phase allows determinat...
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| Format: | Thesis |
| Language: | English |
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2017
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| Online Access: | http://hdl.handle.net/10356/72582 |
| _version_ | 1826114756022370304 |
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| author | Wang, Zhaomin |
| author2 | Anand Krishna Asundi |
| author_facet | Anand Krishna Asundi Wang, Zhaomin |
| author_sort | Wang, Zhaomin |
| collection | NTU |
| description | Digital holography is fast becoming a generalized technique for 3D precision measurement. By numerical reconstruction and propagation of a digital hologram, the optical field from an object and thus the amplitude and phase can be quantitatively reconstructed. The quantitative phase allows determination of the surface topography of the object with nanometer sensitivity. Aspheric lenses are being increasingly used in optical system due to savings in costs and components. However, an aspheric is a complex surface designed using non-linear equations and hence fabrication is as best as can be measured. Various approaches primarily using null interferometry have been proposed and used with limited success and slow speeds. In this thesis, measurement and characterization of the aspheric lens with digital holography is studied. An adaptive optical element is introduced in the digital holography setup to measure aspheric lenses with different Numerical Aperture (NA). To measure the high gradient surface on the aspheric lens, a Dual-Wavelength Digital Holography (DWDH) with four phase unwrapping methods is proposed and demonstrated. For high resolution and large Field Of View (FOV), a novel synthetic aperture digital holography with first order spectrum based registration is suggested and analyzed. Finally, to characterize aspheric lenses, a linear simplified expression is applied to aspheric surface fitting, and a modified Zernike polynomials fitting method is proposed to evaluate the wavefront of the aspheric lens. |
| first_indexed | 2024-10-01T03:44:20Z |
| format | Thesis |
| id | ntu-10356/72582 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2024-10-01T03:44:20Z |
| publishDate | 2017 |
| record_format | dspace |
| spelling | ntu-10356/725822023-03-11T18:06:08Z Studies on digital holography for aspheric surface measurement Wang, Zhaomin Anand Krishna Asundi School of Mechanical and Aerospace Engineering DRNTU::Engineering::Mechanical engineering Digital holography is fast becoming a generalized technique for 3D precision measurement. By numerical reconstruction and propagation of a digital hologram, the optical field from an object and thus the amplitude and phase can be quantitatively reconstructed. The quantitative phase allows determination of the surface topography of the object with nanometer sensitivity. Aspheric lenses are being increasingly used in optical system due to savings in costs and components. However, an aspheric is a complex surface designed using non-linear equations and hence fabrication is as best as can be measured. Various approaches primarily using null interferometry have been proposed and used with limited success and slow speeds. In this thesis, measurement and characterization of the aspheric lens with digital holography is studied. An adaptive optical element is introduced in the digital holography setup to measure aspheric lenses with different Numerical Aperture (NA). To measure the high gradient surface on the aspheric lens, a Dual-Wavelength Digital Holography (DWDH) with four phase unwrapping methods is proposed and demonstrated. For high resolution and large Field Of View (FOV), a novel synthetic aperture digital holography with first order spectrum based registration is suggested and analyzed. Finally, to characterize aspheric lenses, a linear simplified expression is applied to aspheric surface fitting, and a modified Zernike polynomials fitting method is proposed to evaluate the wavefront of the aspheric lens. Doctor of Philosophy (MAE) 2017-08-29T06:32:06Z 2017-08-29T06:32:06Z 2017 Thesis Wang, Z. (2017). Studies on digital holography for aspheric surface measurement. Doctoral thesis, Nanyang Technological University, Singapore. http://hdl.handle.net/10356/72582 10.32657/10356/72582 en 149 p. application/pdf |
| spellingShingle | DRNTU::Engineering::Mechanical engineering Wang, Zhaomin Studies on digital holography for aspheric surface measurement |
| title | Studies on digital holography for aspheric surface measurement |
| title_full | Studies on digital holography for aspheric surface measurement |
| title_fullStr | Studies on digital holography for aspheric surface measurement |
| title_full_unstemmed | Studies on digital holography for aspheric surface measurement |
| title_short | Studies on digital holography for aspheric surface measurement |
| title_sort | studies on digital holography for aspheric surface measurement |
| topic | DRNTU::Engineering::Mechanical engineering |
| url | http://hdl.handle.net/10356/72582 |
| work_keys_str_mv | AT wangzhaomin studiesondigitalholographyforasphericsurfacemeasurement |