An Optical Sensor for Measuring the Position and Slanting Direction of Flat Surfaces

• Published in: Sensors (Basel, Switzerland) Vol. 16; no. 7; p. 1061
• Main Authors: Chen, Yu-Ta, Huang, Yen-Sheng, Liu, Chien-Sheng
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 09-07-2016; MDPI
• Subjects: Accuracy; autocollimator; autofocus; Automation; Computer programs; Computer simulation; Flat surfaces; Inspection; Laser beams; Lasers; Light spots; Manufacturing; Mathematical models; Matrix methods; Measurement techniques; Optical benches; Optical design; Photoelectricity; Position measurement; Position sensing; Production costs; Ray tracing; Semiconductors; Sensors; Series expansion; Silicon wafers; Taylor series; Taiwan; autocollimator; autofocus; flat surfaces
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s16071061

Automated optical inspection is a very important technique. For this reason, this study proposes an optical non-contact slanting surface measuring system. The essential features of the measurement system are obtained through simulations using the optical design software Zemax. The actual propagation of laser beams within the measurement system is traced by using a homogeneous transformation matrix (HTM), the skew-ray tracing method, and a first-order Taylor series expansion. Additionally, a complete mathematical model that describes the variations in light spots on photoelectric sensors and the corresponding changes in the sample orientation and distance was established. Finally, a laboratory prototype system was constructed on an optical bench to verify experimentally the proposed system. This measurement system can simultaneously detect the slanting angles (x, z) in the x and z directions of the sample and the distance (y) between the biconvex lens and the flat sample surface.