| Microscope is one of the important detection tools in the field of modern medicine, the function of microscope is mainly decided by the micro-objective. An excellent biological micro-objective is not only reflects in the optimal optical aberration control, excellent processing and assembling, but also in the aspect of excellent stray light suppression. The stray light reduces the imaging contrast of microscope that then lead to the deviation of MTF, gradation and even definition. So well control of stray light is indispensable premise of obtaining the high-performance image quality. Thus, it requires that the stray light analysis must be conducted before the forming of optical system design, and must be tested after adjustment of optical processing. The development of computer-aided optical design makes it possible to do stray light simulation analysis. This paper based on the demand of the design of micro-objective stray light tester, through simulating different conditions and different surface scattering, studies the influence of the stray light as the following several aspects:(1) The design of micro-objective stray light tester. According to the theoretical basis of black spot method and the national standard, design the measuring tester to test the coefficient of micro-objective stray light. From lighting system to black-spot substrate, from objective system to image test of integrating sphere photomultiplier tubes, all have the detailed analysis of the light transmission. And on its basis to select main components and design the key parts of the connection structure, finish the overall design of micro-objective stray light tester;(2) The establishment of the physical model of measuring micro-objectives stray light based on the black spot method: According to the theory basis of stray light to analyze scattering surfaces of micro-objective and stray light path, combine with the existing objectives of optical structure and mechanical structure, establish the model of the micro-objective stray light tester which based on black spot method, and use the TracePro optical simulation software to set up the boundary conditions, including the divergence angle and intensity of light source, the BRDF of mechanical and optical surface, the transmittance of substrate with black spot(without black spot), the position and size of detector. By using NA=1.28, 98× micro-objective,respectively replaced with dark spot substrate and substrate without black spot, it can be concluded that the VGI is 13.07% and verified the feasibility of the simulation model of stray light tester;(3) The analysis of micro-objective stray light under different measurement condition. In the simulation model, exploring the influence on the VGI under different experimental parameters, such as numerical aperture of illumination, field size, defocus and black spot positions in the field. It is concluded that the VGI increases as numerical aperture and illumination field increase; For the micro-objective with 98×, NA = 1.28, four times of defocus is small value, and it’s easy to neglect the influence of defocus through focusing exactly using manual adjustment wheel; Moreover, put the edge field aside, the VGI of micro-objective decreases with the offset of black spot off center position of field, and the largest VGI is derived from the center of filed, In other words, the VGI characteristics of center field represents and reflects the maximum level of micro-objective optical system;(4) The analysis of stray light under different surfaces scattering of micro-objective. Through setting the surfaces scattering of BRDF parameters of different NA, delve into the influence of different parameters, such as optical surface roughness(2 nm, 5 nm, 10 nm, 20 nm), cleanliness levels(100, 230, 500, 230) and the mechanical structure surface black-dyeing or not, on of VGI measurement. So, the methods to reduce the VGI of micro-objective system are strictly controlling the surface roughness, guaranteeing the surface cleanliness under basic level and appropriately using similar Avian Black-S extinction materials for mechanical structure black-dyeing. |
PDF Full Text Request