• Journal of the Korean Society for Precision Engineering
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• v.25 no.8
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• pp.21-28
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• 2008

Fizeau interferometer is used for inspecting the lens surface profile accurately. This study is focused on the design and optical measuring techniques for large optical components, such as a reflection mirror for large area lithography or astronomical purpose. A tower type Fizeau interferometer is designed and set up in horizontally with a 45$^{\circ}$ fold mirror which makes easy to align the optical path of heavy interferometer system. To align the optical path, a five-axes stage for the interferometer is required. This study shows a method of the 45$^{\circ}$ fold mirror alignment by using a three-axis stage instead of adjusting the interferometer itself or measuring object. This system will be installed on the large optics polishing machine during the manufacturing process as an on-machine inspection system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1649-1657
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• 2006

Fizeau interferometer is well known optical instrument for measuring the lens profile accurately. The object of this study is focused on the design and optical measuring techniques for large optical components, such as a reflection mirror for astronomical purpose. Measuring of large optical lens, the object could not be moved as small one but the measuring instrument must be moved for the alignment, because of the geometric conditions and the accuracy of the stage. Therefore, a five axis stage is designed to align the Interferometer instead of the measuring object. This instrument will be used for an on machine measuring system in polishing machine for large optical lens.

• Proceedings of the Optical Society of Korea Conference
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• 1996.09a
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• pp.50-50
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• 1996

• Korean Journal of Optics and Photonics
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• v.12 no.4
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• pp.334-338
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• 2001

A Fizeau interferometer without beam splitter was constructed. Single-mode optical fiber was used as a spherical wave source and the face of fiber end was polished and coated to be a reflecting surface. The reflecting surface was angled so that interference fringe could be detected by CCD camera. Beam splitter in front of a spherical wave source could distort the wave front and that was one of the component error sources. With the proposed configuration there was no need to place beam splitter in the system. Improvement of phase measuring accuracy was evaluated quantitatively by comparing the result of this setup with that of a conventional Fizeau interferometer. Wave front of the angled end-face optical fiber source was also measured to verify its sphericity by PS/PDI (Phase Shifting/Point Diffraction Interferometer). The principle of this technique was presented and the experimental results and its applications were discussed. ussed.

• Journal of the Institute of Convergence Signal Processing
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• v.7 no.3
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• pp.122-129
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• 2006

We propose the Fizeau-type phase shifting interferometer(FPSI) system for the performance test of high-order aspheric lenses. The proposed system is divided into two parts : optical part and signal processing part. Those two parts are operated by a program for hardware control. We also developed an analysis program adopting the phase shifting algorithm to analyze the obtained interferograms. We can confirm that the proposed system is efficient and adequate by direct comparison with the standard criterion in Mark IV interferometric system of Zygo. The peak-to-valley and RMS values of surface errors which are used to characterize high-order aspheric lenses are 0.845 wave and 0.1871 wave, respectively. The measurement errors between the proposed system and Mark IV are less than ${\lambda}/100$ and the repeatability is also calculated at less than ${\lambda}/100$.

• Journal of the Optical Society of Korea
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• v.14 no.4
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• pp.409-414
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• 2010

This paper describes the surface form measurement of a spherical smooth surface by using single shot off-axis Fizeau interferometry. The demodulated phase map is obtained and unwrapped to remove the $2\pi$ ambiguity. The unwrapped phase map is converted to height and the 3D surface height of the surface object is reconstructed. The results extracted from the single shot off-axis geometry are compared with the results extracted from four-frame phase shifting in-line interferometry, and the results are in excellent agreement.

• Korean Journal of Optics and Photonics
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• v.34 no.1
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• pp.22-30
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• 2023

The use of segmented mirrors is one of the ways to make the primary mirror of a spaceborne satellite larger, where several small mirrors are combined into a large monolithic mirror. To align multiple segmented mirrors as one large mirror, there must be no discontinuity in the x, y-axis (tilt) and axial alignment error (piston) between adjacent mirrors. When the tilt and piston are removed, we can collect the light in one direction and get an expected clear image. Therefore, we need a precise wavefront sensor that can measure the alignment error of the segmented mirrors in nm scale. The tilt error can be easily detected by the point spread image of the segmented mirrors, while the piston error is hard to detect because of the absence of apparent features, but makes a downgraded image. In this paper we used an optical testing interferometer such as a Fizeau interferometer, which has various advantages when aligning the segmented mirror on the ground, and focused on measuring the axial displacement error of a segmented mirror as the basic research of measuring the piston errors between adjacent mirrors. First, we calculated the relationship between the axial displacement error of the segmented mirror and the surface defocus error of the interferometer and verified the calculated formula through experiments. Using the experimental results, we analyzed the measurement uncertainty and obtained the limitation of the Fizeau interferometer in detecting axial displacement errors.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1589_1590
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• 2009

본 논문에서는 구면 렌즈 검사를 위해 제작된 Fizeau형 위상 천이 간섭계(Fizeau-type Phase Shifting Interferometer : FPSI)에 비구면 해석 알고리즘을 적용한 소형 비구면 렌즈 해석 방법을 제안한다. 또한 본 논문에서 제안한 방법의 측정 결과와 기존 비구면 검사 시스템의 측정 결과를 비교하여 그 성능을 평가한다.

• Korean Journal of Optics and Photonics
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• v.16 no.1
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• pp.50-55
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• 2005

A method for measuring the wavefront error and the modulation transfer function(MTF) of large aperture optics using an unequal path interferometer is presented. A bidirectional shearing interferometer is used for collimation testing of the measurement system. A large aperture Fizeau interferometer with long optical path difference measures the wavefront error of the optics under test by using a $\Phi$ 400 mm off-axis parabolic mirror. The MTF is also measured at the wavelength of the interferometer by changing the laser light into partially incoherent light. Test results of a $\Phi$ 300 mm Cassegrain type satellite telescope made in Korea are presented.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.474-480
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• 2002

Aspheric optical lenses and mirrors are widely used in recent. It is more difficult to manufacture and measure the aspherical optics compared to conventional spherical ones. The interferometric optical test is common for the measurement of spherical optical surface. But the application of the interferometry to the measurement of aspheric surface is difficult because it needs a precise null corrector and very careful environmental conditions such as keeping constant temperature, humidity, atmospheric pressure and vibrations. To enhance productivity of optics manufacturing on-machine measurement and correction has been developed in this study. For practical applications, robustness of the measurement method to environments is more important. For the purpose an optical OMM(On-Machine Measurement) system has been developed using Shack-Hartmann test which has robustness to the environment. The wavefront has been reconstructed from the measured data using the primary aberration polynomial function by least square fitting. The measured result of the developed only system gives the maximum deviation only in 200 nm from the result measured by a commercial Fizeau interferometer Wyko 6000.