Collimating lens rear surface self-calibration co-light-path interferometer based on acoustic-optical heterodyning phase shifting

Abstract

The invention discloses a collimating lens rear surface self-calibration co-light-path interferometer based on acoustic-optical heterodyning phase shifting. By means of heterodyning interference phase shifting of an acoustic-optical frequency shifter, moving parts of the interferometer are effectively avoided, measurement precision is further improved, interference prevention performance is good, research difficulty and cost can be reduced, and the interferometer is obviously superior to mechanical drive in measurement of a large-diameter surface shape; meanwhile, low-frequency difference heterodyning interference and high-speed surface area array continuous collection are achieved, obtained information is richer, accurate calculation of a phase position is facilitated, and influences of noise and other factors are overcome; additionally, point diffraction self-calibration light beams are additionally formed, and a reference mirror is calibrated in advance by means of point diffraction light during measurement. Precision requirements of the reference mirror can be reduced, measurement precision is improved and researching difficulty and cost of the interferometer are reduced.

Description

technical field [0001] The invention relates to the field of optical technology, in particular to an acousto-optic heterodyne phase-shifting self-calibrating common optical path interferometer on the rear surface of a collimating mirror. Background technique [0002] The high-end optical equipment represented by the projection exposure system of the deep ultraviolet lithography machine poses great challenges to the processing of optical components and the integration of optical systems. Interferometer is an indispensable core detection equipment for high-precision optical component processing and optical system integration, and the detection accuracy requirements are constantly improving. [0003] The optical surface shape detection methods used in traditional optical processing include Hartmann sensor method, knife edge method and contour method. These methods have different disadvantages such as non-digital subjective interpretation or contact damage to the test piece, an...

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Problems solved by technology

However, in fact, the wavelength tuning in the wavelength tuning laser is also to change the cavity length of the resonant cavity through piezoelectric machinery or changing the temperature, or to change the laser wavelength by mechanically rotating the grating, although the components that need to be driven are in the laser cavity. The weight is smaller than the reference mirror, but it is still unavoidable to reduce the precision caused by mechanical movement or temperature change, and the development of tunable lasers is difficult and costly; in addition, the number of steps that can be shifted is limited, and the information obtained is less and accurate. The degree still cannot meet the high-precision measurement requirements

[0009] In addition, some existing common optical path heterodyne interferometers require a reference mirror with extremely high surface shape accuracy as a scale, and the accuracy of the reference mirror directly determines the final measurement accuracy, and the manufacturing difficulty and cost of the reference mirror are extremely high. High, especially for large-aperture interferometers, the reference mirror directly restricts the caliber and precision of the interferometer

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