Der-Chin Chen

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.

The off-axis parabolic mirror optical axis adjustment based on cyclic shearing interferometer

In this paper we demonstrate a new technique in which we use the portable alignment device of an off-axis parabolic mirror optical axis adjustment, the cyclic shearing interferometer and the CCD camera to rapidly and accurately align the optical axis of an off-axis parabolic (OAP) mirror. In this method the optical axis of an OAP mirror is made parallel to the “five incident parallel laser beams” in the plane of incidence, by checking direction of these five reflected laser beams and changing the height and orientation of the OAP mirror. The cyclic interferometer is referred to as the layout where two beams travel in same directions, encountering exactly the same components until they emerge to form interference pattern. The cyclic shearing interferometer uses to examine the parallel of five incident parallel laser beams. This fast aligning method for finding the optical axis of an OAP mirror can measure the Slant Focal Length deviation to an accuracy of 0.3 %.

Portable Brain Wave Refractometer

In this paper we demonstrate a new technique in which we use the Portable Brain Wave Refractometer (PBWR) to rapidly and accurately measure the error of refraction of eye. The aim of this study is to evaluate PBWR as a minimally invasive method of measuring the attention, meditation levels and the error of refraction of myoptic vision. Two psychologically-based tests were conducted to assess the suitability of the brain wave device to measure and categorize a users level of attention and meditation. The two states of brain wave represent the normal or abnormal visions. The electroencephalography (EEG) lies in the mobile recording and real time feedback of emotional and cognitive states. This fast testing method for correcting the error of refraction of myopic vision can get the visual acuity (V.A.) to 0.8-1.2.

A new alignment device for the optical axes of porro prism binocular

In this paper we demonstrate a new alignment device in which we use the five parallel laser beams each set to rapidly and accurately align their corresponding optical axis of porro prism binocular (PPB). At all interpupillary distances (IPD), this technique assures parallelized right and left optics axis of PPB. In this method the left and right optical axis of a PPB are made parallel to each central beam of two “five parallel laser beams alignment devices” in the plane of incidence. And above process is assured by examining the direction of these five transmitted laser beams that transmitted through PPB in the way that the height and orientation of the PPB are fine tuned. The parallelism of the left and right optical axis of the PPB was measured by laser rangefinder. This novel method is used to obtain the parallelism of left and right optical axis of PPB in a maximum tolerance of three arc minute.