Digital Projector Calibration for 3-D Active Vision Systems

3-D active vision systems that project artificial structured light for coordinate measurements have been adopted in many industrial applications. With advances of electronic projection display technology, the digital projector is becoming an important component of various 3-D active vision systems. However, current projector models or structured light calibration techniques for 3-D active vision systems are limited to stripe-type structured light and the majority of them do not consider projector lens distortion. In order to overcome these limitations, a digital projector calibration method is developed to calibrate light beams projected from all pixel elements of a digital projector. Since the digital projector is fully programmable, various structured light patterns can be projected for coordinate acquisition, whose models can be obtained by interpolating parameters of light beams that synthesize the structured light patterns. With proper interpolation functions, experimental results indicate that the projector lens distortion can be successfully compensated and measurement errors are significantly reduced. When the digital projector is moved, a simple rigid body transformation calibration method is developed to rapidly obtain the transformation without re-calibrating the projector. The precision of the 3-D active vision system using the proposed digital projector calibration method and rigid body transformation calibration technique is experimentally evaluated.