A novel equipment for spy quantitative testing is presented in this paper. A light beam from a semiconductor laser diode converges into a line-shape by a cylindrical lens

projected onto the inner surface in a parallel direction with the pipe axis

and the information to be detected can be got from the deformed line. A special compact reflected-refracted prism group is designed for small pipes

ensuring that the line-shape light beam can be projected and then the deformed line can be imaged by a CCD camera. The image is captured into a computer by a 512×512 pixels image card for further processing

but without losing or changing any useful geometrical feature. The parameters such as pitch and depth can be measured on the monitor screen aided by the computer. The pipe diameter can also be measured by moving the stage along the pipe radius until the opposite inner surface is exactly illuminated and focused by the CCD objective lens. The experiment results show that the accuracy of ±17μm of pitch measurement

±12μm of diameter measurement has been achieved

and it has a good future to application in industry.