We describe a new method of testing optical surfaces having a very large radius of curvature. The method combines a Fizeau interferometer with a set of specially designed zoom lenses. The zoom lenses make the test setup compact, convenient and flexible in testing optical surfaces having a very large radius of curvature. We review the design of the zoom lenses used for this purpose, and describe their performance, showing that reasonably good reference beams can be provided by these lenses to test optical surfaces having a large and variable range of radii.
We developed a method of extending the depth of field of a microscope objective specifically used in an imaging system designed for small particle tracking. We extended the depth of field by inserting a quartic phase plate near the aperture stop plane of an objective. An optimum quartic phase plate was designed for a conventional 100X/0.8 microscope objective, and the simulation results predicated that the depth of field of the new objective could be increased more than twofold in comparison with an objective having no such phase plate.
We present a novel method of increasing the focal depth of an optical system that can be used in a star tracker. The method is based on a special phase plate that is placed in the vicinity of the aperture stop of an optical system to produce the required spot size over a large focal depth. Phase retardation was applied to a lens system having a focal length of 30 mm, an F-number of 2, a working wavelength range of 0.5~0.75 μm and a view angle of 20 degrees. The performance of a lens having a suitable quartic phase was analyzed, and it was shown that the focal depth of such a lens system can be extended more than threefold as compared to a system having no phase plate.
We present a simple and effective method of reducing the background noise of a full-field optical coherence tomography system that improves the image quality of the system. The system is based on a modified Michelson interferometer providing such new features as a tilted cubic beam-splitter and a spatial filter incorporated in the back focal plane of an imaging lens. The new arrangement reduces background noise significantly. The effects of the tilted beam-splitter and spatial filter on the optical image are also studied, and experimental results are provided.
In this paper we present a normalized method of deriving a phase pupil function to extend the focal depth of imaging systems specially used for small object tracking. The method is based on the concept that the intensity distribution in the vicinity of the focal plane can be controlled and redistributed by means of a phase pupil function. This phase pupil function allows the peak intensity of a point-spread function (PSF) of the imaging system to remain relatively uniform, and the profile of the PSF to be approximately fitted to a Gaussian function in an extended range of the focal depth. A rotational symmetric aspheric phase plate has been designed and fabricated. The imaging system incorporating this pupil plate has extended the focal depth more than twofold compared with a conventional imaging system. Theoretical analyses and experimental results are also presented in support of this method.