Heterodyne interferometer based on phase shift of low-frequency-difference acousto-optic frequency shifter

Abstract

The invention discloses a heterodyne interferometer based on the phase shift of a low-frequency-difference acousto-optic frequency shifter. The heterodyne interferometer based on the phase shift of the low-frequency-difference acousto-optic frequency shifter comprises a light beam adjusting unit, a low-frequency-difference phase shifting unit, a beam expanding unit, a light beam combining unit and an area array detector unit. The light beam adjusting unit is used for adjusting output lasers of a laser device into two laser beams. The low-frequency-difference phase shifting unit is used for adjusting the frequencies of the two laser beams obtained by the light beam adjusting unit to obtain two laser beams with the output difference frequency being a low difference frequency lower than 100 Hz. The beam expanding unit is used for expanding the diameters of the two laser beams output by the low-frequency-difference phase shifting unit to be equal to the size of a surface to be measured and using the expanded two laser beams as reference light and measuring light respectively. The light beam combining unit is used for enabling the measuring light returned from the surface to be measured and the reference light to be combined to generate interference. The area array detector unit is used for collecting the interference. According to the heterodyne interferometer based on the phase shift of the low-frequency-difference acousto-optic frequency shifter, heterodyne interference phase shift of the acousto-optic frequency shifter is adopted to effectively avoid that moving parts exist in the interferometer, the measurement accuracy is further improved, and the anti-interference performance is good.

Description

technical field [0001] The invention relates to the technical field of optical detection, in particular to a phase-shifting heterodyne interferometer based on a low-frequency difference acousto-optic frequency shifter. Background technique [0002] With the development of modern precision instruments, the requirements for the processing accuracy of optical surface shape are gradually improved, and the requirements for the detection accuracy of optical surface shape are also correspondingly higher and higher. 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, and it is difficult to achieve high measurement accuracy, which belongs to the simple measurement method. [0003] In practice, the high-precision surface shape detection is almost always done by...

AI Technical Summary

Problems solved by technology

[0008] However, due to the use of mechanical movement as a phase shifting method, the accuracy is still not high enough, the cost is high, and the development is difficult

Especially for the measurement of large-diameter surface shape, the accuracy of precision mechanical drive is reduced, and the measurement accuracy is also reduced

[0009] It can be seen that at present, most interferometers are phase-shifted due to mechanical drive, and the number of phase-shifting steps is small. Usually, there are disadvantages such as difficulty in achieving high precision, poor immunity to interference, small amount of information obtained, and complex high-precision calculation algorithms.

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