Testing Off-axis Aspheric Surface By Combined-hologram

With rapid development of science and technology, the development direction ofoptical system is small, simple, lightweight and cost-effective. Off-axis aspheric sur-face has many advantages, such as simplified system structure, improved optical per-formance, and reduced the risk of manufacture, so that it has been used in more andmore optical systems. Therefore, there is very important application value in engi-neering to develop high quality off-axis aspheric surface. The measurement technolo-gy of off-axis aspheric surface in high-precision is always a frontier topic in advancedoptical manufacture; meanwhile, it also has a big challenge. For this, we choosecomputer generated hologram (CGH) as compensation and alignment element, pro-pose two detection methods, research the key technologies of them in detail, andcomplete its corresponding experiments. All of them prove the correctness of thesetwo methods.In order to test off-axis aspheric surface with small diameter and small asphericdeviation, single CGH compensation detection techniques is presented. In this tech-nology, test CGH (for measuring off-axis aspheric surface), alignment CGH (foraligning CGH and interferometer), and hologram mark (for aligning CGH andoff-axis aspheric), are all produced on one holographic substrate, forming a com-bined-hologram, which can not only achieve shape detection of off-axis aspheric sur-face, but also assist the alignment between optical elements of the detection system.The design method of every part of combined-hologram is described in detail, anddevelops its corresponding special design software based on MATLAB. With thesesoftwares, two off-axis parabolic surfaces were chosen to give their CGHs examples.With simulation in Zemax, the correctness of this technology is proved. Meanwhile, acomparison method was proposed to compare CGH fringe position between our de-sign method and simulation in Zemax.If the off-axis aspheric surface has larger diameter and larger aspheric deviation,a hybrid detection technique including refraction optical element and diffraction opti-cal element can test it within null compensation measurement. This hybrid methodremedies its respective limitation of traditional compensator and CGH, and makes itsadvantages together, so that it increases the ability of aberration compensation. It is aneffective solution to test off-axis aspheric surface. After that, it is also completed that the development of its corresponding software and the comparison with simulation inZemax.In CGH design process, B-spline is used to fit CGH phase function, which is apiecewise fitting method. It can simplify the fitting function, and improve calculationefficiency. Hologram mark is used in the two detection methods, which provides ref-erence when adjusting optical elements, make the experiments simply, and increasethe detection efficiency. In a word, it is more likely to get an accurate test results.In experiments, two off-axis parabolic surfaces were chosen, because it can betested by auto-collimation with plane mirror, a cross-validation method. For Φ50andΦ135off-axis parabolic surface, single CGH test results of them all match well withthe results got by auto-collimation. All of them prove the correctness and reliability ofsingle CGH detection technique. In the hybrid compensation method experiment withΦ135off-axis parabolic surface, its result also coincides with auto-collimation testresult. Subsequently, the error sources in experiments were analyzed separately; andits corresponding solutions were presented.My research results provide an effective method for testing off-axis asphericsurface in high precision. Even more, it lays the foundation for development of highquality off-axis aspheric surface, and has a strong engineering application.