Study On Some Key Techniques Of Testing Aspheric Surface By Compensation Method

Compensation null test is a very important method in testing aspheric surface with high accuracy. In this thesis, some key techniques of compensation method for testing aspheric surface are studied.First we take the mold corn of DVD optical pick-up objective lenses as an example, a design is presented for an objective lenses witch is related to the testing, a kind of structure of compensator for testing small aspheric surfaces with large NA is put forward, and a compensator for the being tested mold corn aspheric surfaces is designed, the analyses to this compensator shows we are capable of measuring the aspheric surfaces mold corn to the accuracy(RMS) of 0.05λRMS, it is enough to satisfy the testing of mold cone surface.Second, lenses compensator with high accuracy has great quality request to the homogeneity of optical glass. In this thesis, a high accuracy apparatus for testing the homogeneity of optical glass is developed, and the test result shows the measurement error is less than 1×10-6. To different condition, two new absolute homogeneity testing methods is put forward.Third, to get ideal lens compensator, sometimes we had to use surfaces with long radius of curvature. For testing this kind of surfaces with long radius of curvature,, a high accuracy method is put forward. In the method, another compensator, which is made of two different glasses with very small differential of refraction index, is used to generate long focal length. The analyses to this kind of compensator for a convex mirror of radius 22000mm and a concave mirror of radius 5600mm show the accuracy to test radius is capable of 0.1% and the accuracy to surface errors(RMS) is capable ofλ/150.In the last, we take concave cylinder mirror and its compensator(convex cylinder mirror) as an example, alignment technique of the compensator in testing is studied, through computer-aided analyzing, a method for adjusting the compensator and the being tested cylinder mirror is established, real adjustment shows this method is very valid.