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When wavefront is reflected by a surface, the information of the surface profile is carried by the reflected wavefront. Measure the wavefront can extract the profile information. There are different kinds of pre-defined surface profile with various dimensions. While the size of particular wavefront sensor is fixed, the measurement range is limited. The design of optical system to bridge the work piece and wavefront sensor is critical. This paper presents a platform for the guidance of optical system design. The parameters of commercial available optical components are input to the platforms and the propagation of reflected wavefront is simulated. The relationship of part profile and the measurement wavefront is provided. The discussion is focused on the 2f+2f system for surface flatness measurement. The measurement of aspherical surface is also presented. Shack-Hartmann wavefront sensor (SHWS) is selected due to its simple structure, insensitivity to vibration etc, which is suitable for in-line application. Optical system is designed with the guidance of simulation platform. The experimental results shows the 2f+2f system is compatible to misalignments, can be used to monitor the deformations of parts. The measurement of aspherical surface is also presented with the comparison of simulation results.

In this study, the interaction performance of three light sources, namely white light, laser diode and He-Ne laser, with two wave-front sensing systems was investigated experimentally using different sensing distances and sampling apertures (two hole-apertures for a Hartmann system and a spatial-light-modulator lenslet-array for a digital Shack-Hartmann system). It was found that the white light source was the best for the Hartmann system, while the He-Ne laser was the most suitable light source for the digital Shack-Hartmann system. Geometrical accuracy of a hole-array aperture and the sensing distance are important to generate stable wave fronts.

Since its emergence in the early 1970s, Shack-Hartmann Wavefront Sensing technology has been investigated and explored world-widely by the researchers and engineers. However, there are few papers or reports to study the system performance and key factors to affect the performance of a Shack-Hartmann Wavefront Sensor (SHWS), in this paper, through experimental study of the system stability of a SHWS, it is found that the image sensor and detector, normally a CCD, should be placed exactly at the focal plane of the lenslet array, otherwise it will bring in significant wavefront measurement error. In order to improve the system performance, a special lenslet array with long focal range is designed, and it is functioned by a spatial light modulator for sampling wavefront in a SHWS. Diffractive lenses with long focal length range can provide pseudo-nondiffracting beams, and a long range of focusing plane. The performances and effects of the modified SHWS with such a special lenslet array generated by a programmable SLM, are investigated, and the experimental results show that the system stability and measurement repeatability are not sensitive to the sensing distance, and can keep at a good level in a long range.