Wen-Hong Wu

Novel Image Polarization Method for Measurement of Lens Decentration

Tilt and decenter errors in lenses are usually caused by lens manufacturing processes: either injection or glass molding. This paper presents an image polarization method for measuring tilting and decentering of lenses. We placed a sample lens between two linear polarizers and passed either a focused or a divergent polarized beam through a half-wave or a full-wave plate. If any error were present in the shape of the lens, patterns and colors shown in the image of polarization would be altered. Finally, the degree of error in the shape of the lens can be computed using image processing software.

The design and fabrication of telecentric lens with large field of view

In ultra-precision (distortion < 0.5 %) vision inspection system, the accuracy of measurement depends on sharpness and ndistortion of image. The telecentric lens provides distortion-free and constant magnification (within depth of field) nimage, so it has become an indispensable key module in the amount of visual measuring system. The article presents a ndesign and development of telecentric lens module for the wide range of vision inspection system (field-of-view > 100 nmm). Based on the concept of equivalent design in optical tolerances, the lens module can be designed readily into a ntelecentric system, which consists of five spherical lenses and a glass molded aspheric lens. In order to correct image ndistortion, an aspheric lens would be added to the telecentric system. The experiment shows that the distortion can be nreduced from 1.5 % to 0.34 % and the depth of field (DOF) is also improved up to 28.3 mm.

A polarization image method for lens decentration measurement

the tilt and decenter error of lens is usually induced by lens manufacturing process, injection molding or glass molding. The paper presents a polarization image method for measuring the tilt and decenter of lens. At first, to put the lens under test between two linear polarizers, and then a focused or divergent polarized beam will pass through a half-wave plate, once the lens has a shape error, the polarization image pattern and color will be change. Finally, the lens shape error can be computed by image processing.

The development of automatic optometry instrument based on the ANSI/ISEA Z87.1 standard

In the past, the optometry instrument calibrated in diopter and astigmatism were usually performed by using human eyes. However, the larger uncertainty of measurement will be induced while observing the measuring patterns using human eyes. Therefore, based on the ANSI/ISEA Z87.1-2010 standard, this study presents the development of automatic optometry system, which comprises of the machine vision, image analysis and processing, and automatic focus technique without human operation. In addition, the astigmatism measurement can be well completed in the electric moving stage. The experimental results show the automatic optometry system has the high accuracy and good repeatability.

Development of telescope emulator system

The telescope emulator system comprises the binocular, gyroscope, encoder modular, mobile display, image processing module and computer, which is applied to stargazing, bird-watching teaching, big game player, military shooting, tower-view simulation and outdoor virtual reality, etc. Based on the orientation sensing of gyroscope by two gyroscopes and one encoder module and the message feedback to computer, the system can show the super large image in near-eyes display. Then the super large image will be segmented and distortion-corrected by the image processing module. Furthermore, the images shown on the micro-display module are projected into the eyes of observer by the near-eye system and telescope system. Finally, the image processing result will be shown on the mobile display. This paper presents the design and simulation of the telescope emulator.

A study on a portable fluorescence imaging system

The fluorescent reaction is that an organism or dye, excited by UV light (200-405 nm), emits a specific frequency of light; the light is usually a visible or near infrared light (405-900 nm). During the UV light irradiation, the photosensitive agent will be induced to start the photochemical reaction. In addition, the fluorescence image can be used for fluorescence diagnosis and then photodynamic therapy can be given to dental diseases and skin cancer, which has become a useful tool to provide scientific evidence in many biomedical researches. However, most of the methods on acquiring fluorescence biology traces are still stay in primitive stage, catching by naked eyes and researchers subjective judgment. This article presents a portable camera to obtain the fluorescence image and to make up a deficit from observer competence and subjective judgment. Furthermore, the portable camera offers the 375nm UV-LED exciting light source for user to record fluorescence image and makes the recorded image become persuasive scientific evidence. In addition, when the raising the rate between signal and noise, the signal processing module will not only amplify the fluorescence signal up to 70 %, but also decrease the noise significantly from environmental light on bill and nude mouse testing.