Chia-Hau Lin

Measurement method of three-dimensional profiles of small lens with gratings projection and a flexible compensation system

Research highlights? We use fringe projection grating measurement system to measure small lens. ? Flexible compensation is carried out for the non-uniform image. ? The sub-pixel technology and polynomial regression method are used for higher resolution. ? The measurement accuracy ranges is from 1 to 2 micro-meter. This study proposed a light field flexible compensation system of fringe projection grating measurement, which uses the fringe projection method to calculate the height of a work piece to be measured. A video device first generates an image without gratings for projection and then projects this image. An imaging device then captures the image and sends it back to the image processing device, so as to form an image with projection information without gratings, as well as an image with gratings. Flexible compensation is carried out for this image in an innovative method. Thus, the images with or without gratings can be clearer. In this way, more accurate 3D contour measurement and reconstructive analytical calculation can be carried out for the work piece to be measured. In the experiments, five small lenses are used for system verification. Then, the 3D contour information is measured to reconstruct the lens profile. The value curvature and focal length of the lens were obtained. This system uses the sub-pixel and polynomial regression method to measure the height of objects throughout the experiments. The measurement accuracy ranges from 1 to 2µm. This method can also provide accurate measurement data for inspection within one second. Moreover, quality verification for the lens module is more convenient.

Polar coordinate mapping method for an improved infrared eye-tracking system

In this paper a polar coordinate mapping method for an improved infrared eye-tracking system is described. In the proposed control system for an eye-tracking device, users do not need to wear any equipment. Rather they just ware an infrared light source and an infrared CCD camera to extract the eye images for the computer to analyze, record the information of the moving traces and pupil diameters, control the mouses cursor and operate many kinds of applied programs. The advantage of this system lies in solving non-contact requirement problems for which the measured system would require whole eye monitoring and a quick response. We also improve the feasibility and the safety of this eye-tracking device by using infrared rays and new coordinate mapping method.

Digital image processing for evaluating the characteristics of the microstructure of a holographic plate

Abstract A system of evaluating the microstructure of a holographic plate (for example; a light sensitive plate in dichromated gelatin (DCG) or photoresist emulsion) with economical measuring equipment is described. We observe the holographic plate with a microscope and CCD camera with a PC 586 computer. With the information from grey levels of the scanning image we obtain four film quality characteristics. We can scan the full size of the plate to obtain the macro-pattern. We can also select other magnifications of the local pattern. The apparatus has particular use in the detection of micro-particles of a microstructure.

Evaluation of defects on an optical disc master plate

This paper presents a method to analyse and detect defects on the surface of a master disc (the cause of distorted images) by applying a neural network program and micro-image technology. The method automatically, step-by-step, detects defects in the disc’s electrical signal output which drives an x–y table and provides indicative information for managing contamination in a cleanroom of a manufacturing plant.

Computer analysis and fuzzy control for fabricating a plastic HOE with an injection method

Abstract Injection is an economical method of producing plastic holographic optical elements (HOEs) in large or small quantities and of various types. A computer-analysis system is used to simulate and control the results of the manufacturing system. A computer program, based on coupled-wave theory, predicts and evaluates the diffraction efficiency of a hologram. The CAEMOLD computer simulation software assists in calculating and modifying the injection process. A fuzzy control model is used to obtain the proper operating parameters. These techniques can obtain uniform distribution and a high diffraction efficiency in the plastic HOE product from the results of the computer controller.