The invention relates to a method for determining measurement parameters 7, 8, 9, 12, 14, 15, 18, 19 of a spectacle wearer from an image of the spectacle wearer provided with a spectacle frame, wherein it is determined on the image, automatically, the position of the center of each pupil by analyzing a luminance gradient in the region of each pupil, and wherein it is determined on the image, so Automatic, the positions of horizontal and vertical lines tangential to the frame, by luminance gradient analysis and extraction of the contours of the frame. The invention eliminates the need to manually acquire the image the position of various elements sought.

An optical metrology.

https://ir.nctu.edu.tw:443/bitstream/11536/23475/1/000328913800009.pdf

Transparent electrodes based on conducting polymers for display applications

Dimensional artefacts to achieve metrological traceability in advanced manufacturing

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

The absolute optical thickness of a transparent plate 6-mm thick and 10 mm in diameter was measured by the excess fraction method and a wavelength-tuning Fizeau interferometer. The optical thickness, defined by the group refractive index at the central wavelength, was measured by wavelength scanning. The optical thickness deviation, defined by the ordinary refractive index, was measured using the phase-shifting technique. Two kinds of optical thicknesses, measured by discrete Fourier analysis and the phase-shifting technique, were synthesized to obtain the optical thickness with respect to the ordinary refractive index using Sellmeier equation and least-square fitting.

Absolute optical thickness measurement of transparent plate using excess fraction method and wavelength-tuning Fizeau interferometer

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

https://ir.nctu.edu.tw:443/bitstream/11536/26282/1/000284293400005.pdf

An alternative bend-testing technique for a flexible indium tin oxide film

A linearly/circularly polarized heterodyne light beam coming from a heterodyne light source with an electro-optic modulator in turn enters a modified Twyman–Green interferometer to measure the surface plane of a GRIN lens. Two groups of periodic sinusoidal segments recorded by a fast complementary metal-oxide semiconductor camera are modified, and their associated phases are derived with the unique technique. The data are substituted into the special equations derived from the Fresnel equations, and the refractive index can be obtained. When the processes are applied to other pixels, the full-field refractive-index distribution can be obtained similarly. Its validity is demonstrated.

https://ir.nctu.edu.tw:443/bitstream/11536/26211/1/000285499500011.pdf

Alternative method for measuring the full-field refractive index of a gradient-index lens with normal incidence heterodyne interferometry.

In a modified Twyman-Green interferometer, the optical path variation is measured with the heterodyne central fringe identification technique, as the light beam is focused by a displaced microscopic objective on the front/rear surface of the test transparent plate. The optical path length variation is then measured similarly after the test plate is removed. The geometrical thickness of the test plate can be calculated under the consideration of dispersion effect. This method has a wide measurable range and a high accuracy in the measurable range.

Hung-Chih Hsieh

Papers

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

An alternative bend-testing technique for a flexible indium tin oxide film

Alternative method for measuring the full-field refractive index of a gradient-index lens with normal incidence heterodyne interferometry.

High-accuracy thickness measurement of a transparent plate with the heterodyne central fringe identification technique