Two-wavelength Holographic Measurement Of Surface

In the manufacture of high-quality products and efficient production processes, precision measurement technology plays a significant role, and it is growing importance. Optical measurement technique is a non-contact measurement. It has a lot of advantages over traditional contact measurement technique, such as high accuracy, high signal to noise ratio, fast dynamic response, good linearity, large measuring range, non-contact and so on. Comparing the small differences or dislocation between two smooth surface with the interference method is familiarFor example, if the Michelson interferometer's mirrors in the arms are not completely vertical, parallel interference fringes will appear in the field .Also using Mach-Zehnder interferometer the small difference between one produced smooth sphere and another standard smooth spherical can measure. However, there are two shortcomings in these methods. First, because the comparison is conducted between the two surfaces, relative to the original surface, if the shape and position occurred minor differences, the above method could not work. Second the two surfaces being compared must be smooth.In this paper we introduce a two-wavelength holographic interferometry, and this method can overcome these two shortcomings. Because the objects of comparison are two states of the same surface,and when the surface changes occurred, fine structure of its essentially unchanged at the same local. This method don't limit the smooth surface and it applies to rough diffuse surface too. We use two-wavelength holographic to measure the surface of objects, and show the contour distribution of the surface with interference fringes. Through theoretical analysis and experimental testimony. This is a kind of method with nanometer precision.