An optical evaluation technique is described that is suitable for determining the positions and magnitudes of reflection sites within miniature optical assemblies. This method utilizes the coherence effects exhibited by a broadband optical source and is referred to as optical coherence-domain reflectometry. Background theory is given, and experimental results have demonstrated a resolution of 10 μm with an optical dynamic range of more than 100 dB.

Optical coherence-domain reflectometry: a new optical evaluation technique

A fiber optic sensor for determining the thickness of a transparent plate (1–2.5 mm) is described based on a fiber optic displacement sensor. The sensor characteristics are found to vary with the change in the thickness of a plate. A theoretical model is proposed and validated with experimental results. The behavior of the sensor is evaluated and analyzed in terms of the numerical aperture and diameter of the fiber.

Determination of the thickness of a transparent plate using a reflective fiber optic displacement sensor

We present a method for dynamically measuring the refractive index distribution in a large range based on the combination of digital holographic interferometry and total internal reflection. A series of holograms, carrying the index information of mixed liquids adhered on a total reflection prism surface, are recorded with CCD during the diffusion process. Phase shift differences of the reflected light are reconstructed exploiting the principle of double-exposure holographic interferometry. According to the relationship between the reflection phase shift difference and the liquid index, two dimensional index distributions can be directly figured out, assuming that the index of air near the prism surface is constant. The proposed method can also be applied to measure the index of solid media and monitor the index variation during some chemical reaction processes.

Dynamical measurement of refractive index distribution using digital holographic interferometry based on total internal reflection

A non-invasive measurement method for transparent objects using digital holographic interferometry based on iterative least-squares phase unwrapping is presented. Holograms are captured and processed by digital method. The phase reconstructed from holograms is wrapped. Continual and real phase is obtained by phase unwrapping. In this paper iterative unwrapping of phase difference is combined with least-squares unwrapping to eliminate errors. The relations between the phase variation of object wave and the thickness deformation and stress of transparent object are given. A polymethyl methacrylate (PMMA) specimen with a hole under uniform tensile force is tested by this method. The experimental results are in accordance with the theoretical ones. That means the method is correct.

Non-invasive Mechanical Measurement for Transparent Objects by Digital Holographic Interferometry Based on Iterative Least-Squares Phase Unwrapping

Near-Membrane Refractometry Using Supercritical Angle Fluorescence.

https://ir.nctu.edu.tw:443/bitstream/11536/27459/1/000186298700015.pdf

Improved technique for measuring refractive index and thickness of a transparent plate

https://ir.nctu.edu.tw:443/bitstream/11536/11482/1/000242269000004.pdf

A method for measuring two-dimensional refractive index distribution with the total internal reflection of p-polarized light and the phase-shifting interferometry

An area scan digital camera is used to record the full-field heterodyne interference signals, and the processes to derive the associated phases from the data of the recorded frames under a convenient condition are described. By calculating the possible errors under several different cases, an optimal condition to get better results is proposed.

https://ir.nctu.edu.tw:443/bitstream/11536/10151/1/000251549300028.pdf

Optimal condition for full-field heterodyne interferometry

Based on Fresnel equations and the phase-shifting interferometry, an alternative method for measuring the two-dimensional refractive index distribution of a material is presented. A linearly polarized light passes through a quarter wave-plate and is incident on the tested material. The reflected light propagates through an analyzer, and then the interference signal can be obtained. The special equations to estimate the phase of the interferometric signal can be derived by using Fresnel equations. Next, the associated two-dimensional phase distribution is measured by the four-step phase-shifting interferometry. Then, the measured data are substituted into the special equations derived previously, and the two-dimensional refractive index distribution of the tested material can be obtained. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

https://ir.nctu.edu.tw:443/bitstream/11536/30486/1/000256862500004.pdf

A method for measuring two‐dimensional refractive index distribution by using Fresnel equations and phase‐shifting interferometry

A collimated heterodyne light enters a modified Linnik micro- scope, and the full-field interference signals are taken by a fast CMOS camera. The sampling intensities recorded at each pixel are fitted to derive a sinusoidal signal, and its phase can be obtained. Next, the 2-D phase unwrapping technique is applied to derive the 2-D phase distribu- tion. Then, Ingelstam's formula is used to calculate the height distribu- tion. Last, the height distribution is filtered with the Gaussian filter, the roughness topography and its average roughness can be obtained and its validity is demonstrated. © 2008 Society of Photo-Optical Instrumentation

https://ir.nctu.edu.tw:443/bitstream/11536/8077/1/000263304100019.pdf

Zhi-Cheng Jian

Papers

Improved technique for measuring refractive index and thickness of a transparent plate

A method for measuring two-dimensional refractive index distribution with the total internal reflection of p-polarized light and the phase-shifting interferometry

Optimal condition for full-field heterodyne interferometry

A method for measuring two‐dimensional refractive index distribution by using Fresnel equations and phase‐shifting interferometry

Nano-roughness measurements with a modified Linnik microscope and the uses of full-field heterodyne interferometry