| dc.description.abstract | The thesis is about the design of three different focal lenses for next generation of autopilot. The purpose is that let the autopilot could be safe and stabilized to identify environment within temperature range from -30C to 70C. The three lens specifications are as follows: Lens with short focal length - Object distance is less than 30 meters, Focal length is 3.6491 mm, F/# is 2.2, and the maximum of half-FOV(field-of-view) is 75 degree; Lens with moderate focal length- Object distance is between 30 and 70 meters, Focal length is 10.5081 mm
,F/# is 2.2,and the maximum of half-FOV(field-of-view) is 25 degree; Lens with long focal length - Object distance is between 70 and 150 meters, Focal length is 18.287 mm, F/# is 2.2,and the maximum of half-FOV(field-of-view) is 15 degree.
The advantage of the three lenses is introducing thermal compensation to optical design at temperature between -30C and 70C. It means that little focal shifts at different temperature between -30C and 70C.
Temperature variation induces refractive index change of glass. Due to thermal expansion that lens radius, thickness of optical element, air gap, and the shape of mechanics are changed. Applying the thermal coefficient of the refractive index (dn/dT) of lens, thermal expansion coefficient of the lens (α) and the thermal expansion coefficient of mount (β) to optical simulation is necessary.
Lens parameters will vary with environmental temperature. Athermal design will let effective length change coherent with thermal variation. It means that diopter and thermal variation will change simultaneously. In Athermal system, the ration between diopter and thermal variation (d/dT) should be zero. If d/dT could not be eliminated, the thermal expansion coefficient (β) of the barrel will be used for athermal compensation. The thesis is focused on eliminating athermal effect by adjusting lens diopter and material of the barrel.
Conclusion that triple-focus lens between -30C and 70C has benefits as below: MTF @110lp/mm >0.6 and the gap between tangential and radial is small than 0.1, Relative illumination>86%, Later color between short wavelength (F’-line) and long one (C’-line)<2.25μm, Optical distortion<2%, athermalization is small than 1.9110-6.
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