Coating And Uniformity Of The Large Diameter To Curvature Ratio Lens

The large diameter to curvature ratio lens is an optical lens with a ratio of diameter to curvature greater than 1.1.The large diameter to curvature ratio lens can be used to achieve large field of view imaging.Due to the large curvature of the surface of the large diameter to curvature ratio lens and the existence of special convex or concave surfaces,it is very difficult to deposit a continuous and uniform optical film on the surface of the large diameter to curvature ratio lens,which restricts the application of the large diameter to curvature ratio lens.Using planetary fixtures can effectively improve the phenomenon of uneven film thickness.In this paper,systematic theoretical and experimental studies have been carried out on the film thickness distribution of the planar three-level planetary fixture,the thickness distribution of the facial mask on the surface of the large diameter to curvature ratio lens,and the preparation of the wide-band antireflection coating for the large diameter to curvature ratio lens.The main research work and achievements are as follows:（1）Based on the theory of cosine distribution of evaporation sources,a mathematical model of theoretical film thickness distribution for the planar three-stage planetary fixture was established.The film thickness distribution of a 1.8m film plating machine equipped with the planar three-stage planetary fixture was simulated and analyzed,and the simulation model was validated through a single layer film experiment.The simulation analysis results show that,under the premise of a certain characteristic parameter of the evaporation source and the geometric configuration of the vacuum chamber,the inclination angle of the planar three-stage planetary fixture is the main factor affecting the film thickness uniformity of the planar three-stage planetary fixture.When the inclination angle of the fixture is 64°,the theoretical film thickness distribution of the planar three-stage planetary fixture is the most uniform.The experimental results of a single layer film show that the actual film thickness distribution of the planar three-stage planetary fixture agrees well with the simulation analysis results,verifying the correctness of the simulation model.（2）By using the planar three-stage planetary fixture,Si O₂ and Ti O₂ single layer films were prepared on two optical plastic lenses with different diameter to curvature ratio.The spectral curves of the single layer films were measured using a confocal reflectance meter.The effects of rotational speed of the annular crucible and the inclination angle of planar three-stage planetary fixture on the film thickness uniformity of the large diameter to curvature ratio lens were studied.The experimental results show that the rotational speed of the annular crucible does not significantly affect the film thickness uniformity of the large diameter to curvature ratio lens,and the inclination angle of the planetary clamp is the main factor affecting the film thickness uniformity of the large diameter to curvature ratio lens.When the inclination angle of planar three-stage planetary fixture is within the range of 61°to64°,the film thickness uniformity of optical plastic lenses with two different diameter to curvature ratio is good.（3）By using electron beam thermal evaporation technology and the planar three-stage planetary fixture,a broadband antireflection film was prepared on two optical plastic lenses with different diameter to curvature ratio with different inclination angles of the planar three-stage planetary fixture.The confocal reflectance measurement instrument and contact optical profilometer were used to detect the spectral curve and surface shape changes of the sample.The test results show that a broadband antireflection film with an average reflectivity of no more than 0.8%and in the range of 420～880nm was successfully prepared on two optical plastic lenses with different diameter to curvature ratio,and the spectral curve deviation at different positions on the surface of different lenses and the same lens did not exceed 10nm;For two optical plastic lenses with different diameter to curvature ratio,coating can cause surface morphology changes.