Projector calibration method based on optical coaxial camera

Abstract

This paper presents a novel method to accurately calibrate a DLP projector by using an optical coaxial camera to capture the needed images. A plate beam splitter is used to make imaging axis of the CCD camera and projecting axis of the DLP projector coaxial, so the DLP projector can be treated as a true inverse camera. A plate having discrete markers on the surface will be designed and manufactured to calibrate the DLP projector. By projecting vertical and horizontal sinusoidal fringe patterns on the plate surface from the projector, the absolute phase of each marker's center can be obtained. The corresponding projector pixel coordinate of each marker is determined from the obtained absolute phase. The internal and external parameters of the DLP projector are calibrated by the corresponding point pair between the projector coordinate and the world coordinate of discrete markers. Experimental results show that the proposed method accurately obtains the parameters of the DLP projector. One advantage of the method is the calibrated internal and external parameters have high accuracy because of uncalibrating the camera. The other is the optical coaxes geometry gives a true inverse camera, so the calibrated parameters are more accurate than that of crossed-optical-axes, especially the principal points and the radial distortion coefficients of the projector lens.

An Accurate Projector Calibration Method Based on Polynomial Distortion Representation

“… Uncorrected straight line: Pixel column 17 (Pixel columns are 1–768 from left to right). Corrected line by model-based method as shown in Reference [ 8 ]: Like the distortion correction of a photograph, the distortion correction of a projector can be achieved by rearranging the pixels on the projector’s object plane with the method based on conventional distortion representation. The ideal line (goal of the correction) on the image plane is the pixel column 17 in the linear (pinhole) model.…”

“…By using a calibration plate with small ring markers on the surface and combined with the phase-calculation algorithm, the corresponding distortion of each projector pixel is able to be calculated independently. [ 8 , 9 ] However, conventional distortion representation is still applied. Some methods which operate on the entire camera-projector systems apply a joint calibration procedure.…”