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Digital Moiré technique is adopted in partial compensation interferometer (PCI) for high-precision testing of figure error of the aspheric surfaces. The figure error of the measured aspheric is obtained by a series of calculation with the real interferogram and ideal interferograms generated by computer. The dense interference fringes at the exit pupil make it difficult to align the PCI. On the contrary, digital Moire fringes composed from real and ideal interferograms are sparse and corresponding to the figure error of the measured aspheric, making it easier to align the PCI. Generally, digital Moire technique is processed on the computer, resulting in slow processing speed and difficult display in real time. Digital Signal Processor (DSP) can be used to implement digital Moire technique and display digital Moire fringes in real time with its powerful processing capacity. In this paper, digital Moire technique is implemented on the TMS320C6455 DSP. The hardware system consists of a DSP module, a CCD camera and a monitor. Finally we experimentally obtain the digital Moire image, and further analyze how to align the PCI theoretically.

Aspheric optical components are the indispensable part of modern optics systems. With the constant development of aspheric optical fabrication technique, the systems with large aperture convex aspheric optical components are widely used in astronomy and space optics. Thus, the measurement of the figure error of the whole convex aspherical surface with high precision comes to be a challenge in the area of optical surface manufacture, and surface testing method is also very important. This paper presents a new partial compensating system by the combination of a refractive lens and a reflective mirror for testing convex aspherical surface. The refractive lens is used to compensate the aberration of the tested convex asphere partially. The reflective mirror is a spherical mirror which is coaxial to the refractive lens and reflecting the lights reflected by the tested convex asphere back to the convex asphere itself. With the long focal length and large aperture system we can realize a lighter and more compact system than the refractive partial compensating system because the spheric reflective mirror is more easily to realize and can bending the light conveniently.