Design of zoom optical system for double laser triangular thickness measurement

According to the requirement of high precision laser thickness gauge, based on the principle of laser triangulation ranging, design a double laser triangular thickness measurement optical system . The system uses two laser triangulation probes with different wavelengths to scan the upper and lower surfaces respectively. The thickness of the object to be measured is calculated by the size of the echo signal of the reflector. Using the optical design software Zemax to design its optical system. The zoom structure is introduced to replace the fixed focus system currently used in the thickness gauge on sale, so as to adapt to different measuring objects. The system has a focal length of 15-60 mm, no special glass and aspheric surface, which greatly reduces the processing and manufacturing costs. When Nyquist frequency is 60 lp/mm, the meridian modulation transfer function curve and sagittal modulation transfer function curve of each field of view are above 0.6, close to the diffraction limit, and the imaging quality is good. Verified by experiment, the measurement resolution is 0.1 micron and the measurement accuracy is 1 micron. It can be widely used in various thickness measurements in industrial testing.