Acta Photonica Sinica

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Measurement of Homogeneity of Optical Glass with Parallel Surfaces Using Low Coherence Light Sources

  

  • Received:2007-07-03 Revised:2007-09-18 Online:2008-12-25 Published:2008-12-25

Abstract: In order to solve the problem that the traditional interferometric absolute method can not test the homogeneity of optical glass and crystal with parallel surfaces,a low coherence light source was used on the Twyman-Green interferometer.Both the front and the rear surface of the tested sample were placed close to the zero-OPD position by adjusting the optical path of the reference arm.The lights reflected from the two surfaces were not interfering with the reference light simultaneously.So the lights reflected either from the front surface or from the rear surface could be distinguished.The interferograms were processed with the virtual grating phase-shifting Moire fringe method.By inputting the data of the acquired phase into the formula of the absolute method,the homogeneity of the sample could be calculated.The thickness and caliber of the tested sample are 13mm and 75mm respectively.The measurement result indicates that the accuracy is within 2.6×10-6,the peak-to-valley value is Δnpv=6.06×10-6,and the rms is Δnrms=8.96×10-7.

Key words: Measurement and metrology, Homogeneity, Low coherence light, Virtual grating phase-shifting Moire fringe method

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