A rugged stereoscopical device for surface inspection

The paper is understood as a continuation of a series of papers on surface metrology for application in quality control of printed matter. A stereoscopic device for extremely rugged applications, especially in quality control in printing industry, is presented. The device developed is based on variable tilted delay elements, which allow the use of a single imaging sensor and robust definition of parallax shift. Variable orthogonal delay elements were already used for variation of plane of focus in surface inspection, as described in previous papers. The method can be applied for macroscopical as well as for microscopic imaging. Beside mechanical design issues, the theoretical description, geometrical-optical approaches, and the treatment of the dispersion problem are discussed. Experimental results are included.