A Calibration Method of Double Grating Focal Length Measuring Instrument

Abstract

The invention discloses a calibration method of a double-grating focal length measuring instrument. A grating line included angle in the double-grating interferometer is calibrated through two lenseswith known focal length design values, and the focal length error of the two lenses with known focal length design values is eliminated, so that the double-grating grid line included angle calibrationprecision and the measuring precision of the focal length measuring instrument are guaranteed. An optimized focal length measuring formula is used, and the included angle between interference fringesand a zero reference line is replaced by the difference between the included angle between the two sets of interference fringes placed in front and behind a to-be-measured element. The problem that an interference fringe zero reference line is difficult to determine is solved, and the influence of an error on the focal length measurement is eliminated.

Description

technical field [0001] The invention belongs to the field of optical precision testing, and in particular relates to a calibration method of a double grating focal length measuring instrument. Background technique [0002] At present, there are mainly traditional measurement methods and the Tabermore method for measuring the focal length of long focal length optical systems. Traditional measurement methods include magnification method, precision angle measurement method, Fourier spectrum method, etc., which are convenient and high-precision when measuring optical components with small focal lengths, but it is difficult to meet the measurement of long focal lengths due to space limitations. The Tabermore method measures the focal length, and the double grating interferometer is the key component. Before measuring the focal length of the linear Ronchi grating, the angle between the grating lines of the grating needs to be calibrated. The calibration method is complicated and t...

AI Technical Summary

Problems solved by technology

Traditional measurement methods include magnification method, precision angle measurement method, Fourier spectrum method, etc., which are convenient and high-precision when measuring optical components with small focal lengths, but it is difficult to meet the measurement of long focal lengths due to space limitations.

The Tabermore method measures the focal length, and the double-grating interferometer is the key component. The linear Ronchi grating needs to calibrate the angle between the grating lines before measuring the focal length. The calibration method is complicated and the accuracy is limited.

[0003] The existing method of calibrating the angle between grating lines needs to know the standard value of the focal length of the calibration lens. For optical elements with medium and long focal lengths above 5m, there is no effective high-precision measurement method to accurately measure the focal length value, which furthermore Severely limits the accuracy of calibration and calibration of medium and long focal length measurement systems using corresponding standard parts

In addition, the focal length measurement range of the system is relatively large. Because of the focal length error of the calibration lens itself and the existence of various measurement system errors, the existing method uses a standard lens with a specific focal length value to calibrate the system, and it is difficult to measure the entire focal length. Achieve high measurement accuracy within the measurement range

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