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

• Published in: Expert systems with applications 2011-05, Vol.38 (5), p.6232-6238
• Main Authors: Lin, Chern-Sheng, Lin, Chia-Hau, Chen, Der-Chin, Tien, Chuen-Lin, Yeh, Mau-Shiun
• Format: Article
• Language: English
• Subjects: 3D contour information; Fringe projection; Small lens
• ISSN: 0957-4174; 1873-6793
• DOI: 10.1016/j.eswa.2010.11.045

► 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.