| Bidirectional transmission distribution functions can be used to characterize the transmission characteristics of random surfaces of optical media,and have important application values in the fields of optical system design and processing,computer modeling and rendering.At present,the measuring devices of bidirectional transmission distribution function mostly use the moving mechanism to measure the sample by rotating scanning,and the measuring speed is too slow to realize the synchronous measurement of multi-angle transmission characteristics.To this end,the research on the measurement method of transmission characteristics of optical media random surface is carried out,the overall architecture of the bidirectional transmission distribution function measurement optical system is constructed,the illumination optical system and the optical field measurement optical system are designed,the off-axis correction algorithm and the background noise elimination method are studied,and the multi-angle synchronous measurement of transmission characteristics of optical media random surface is realized.Based on the measurement principle of bidirectional transmission distribution function,an overall design scheme of a bidirectional transmission distribution function measurement optical system is proposed,and the illumination optical system is optimized.The simulation results show that the illumination optical system has an irradiation uniformity of 98.49%and an outgoing beam divergence angle of ±0.833° within 40 mm of the irradiation surface.The measurement principle of the hemispherical dome is analyzed,and the characteristics and dimensions of the hemispherical dome coating are determined.The mathematical model of an aspheric mirror catadioptric panoramic imaging optical system is established,and the catadioptric panoramic imaging optical system is optimized and designed.The scattering angle measurement range and angular resolution of the catadioptric panoramic imaging optical system are simulated and analyzed.The results show that the minimum resolution is 2° within the range of 0° to 50° elevation angle,and the minimum resolution is20° within the range of 0° to 360° azimuth angle.The spatial position relationship and light field intensity calibration methods were studied,and the spatial relationship model of feature points of the optical field measurement system was constructed.The light field intensity calibration process was developed,and the light field energy correction matrix was obtained.The simulation verified the correctness of the off axis correction algorithm.The results showed that after the spatial position calibration,the feature points were approximately rotationally symmetric around the center of the image plane;after the calibration of light field intensity,the maximum error of light field measurement is 2.67%,achieving off axis correction of the optical system for light field measurement.The background noise elimination method is studied,the noise light field distribution matrix at the image plane of the refractive relay system is derived,and the light field distribution matrix of the sample is solved.The simulation verifies the correctness of the background noise elimination method.The results show that the sample light field distribution obtained by the optical field measurement system conforms to the distribution characteristics of the Lambert light field.A bidirectional transmission distribution function measurement device was built and the main indicators of the lighting optical system were measured.The results showed that the spectral range of the lighting optical system covered 380 nm to 780 nm.At a working distance of 200 mm,when the effective irradiation surface aperture was 40 mm,the uniformity was 96.5%.The accuracy of the bidirectional transmission distribution function measurement optical system has been verified using opal glass.The results show that the maximum relative error of the bidirectional transmission distribution function measurement optical system at 0° to 50° scattering angle is 4.79%,and the maximum average relative error of the circumferential measurement is-2.83%.This proves the feasibility of the measurement method for the transmission characteristics of optical media random surfaces. |
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