Influence of incident angle on distance detection accuracy of point laser probe with charge-coupled device: prediction and calibration

Point laser probes (PLPs) with charge-coupled device (CCD) are widely used in industry engineering. However, the distance detection accuracy is significantly affected by incident angle, which limits the application in free-form surface measurement. To analyze the influence of incident angle, a reference distance is first determined under normal incidence. Then the detection errors are estimated by the relative differences of non-zero incident angles from the reference. Based on laser ray tracking strategy and superposition principle, an intensity spot is formed on the detector plane. The image deviation is assessed using a robust subpixel algorithm. Therefore the distance detection error can be numerically predicted. As a comparison, a precision calibration system is set up, which is composed of CCD-PLP, data card, human manual interface, pulse controller, step motor driver, and calibration device. A calibration procedure was programmed on the upper PC. Thus data sampling, angle control, and error assessment can be achieved. A series of prediction and calibration tests covering angle range from -55 deg to 55 deg were conducted on a five-axis machining center. The results indicate that the trend of calibration was quite coincident with that predicted. The distance detection error has an approximate linear function of incident angle. (C) 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). [DOI: 10.1117/1.OE.51.8.083606]