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A quantitative differential interference contrast (DIC) technique is proposed to measure the step height of TFT substrate, which is widely applied in display devices. Theoretical comparisons between different phase shifting techniques of DIC are given. Not only series of simulations are conducted but also the preliminary experiments of TFT dimension measurement are presented. The proposed accelerating phase shifting DIC technique might be adopted to topography measurement of optical components in industry.

A quantitative phase shifting differential interference contrast (PS-DIC) shearing interferometer is adopted to measure the profile of transparent specimen with inclined surface. The effects of the incline angle on DIC measurement accuracy were studied. The optical model of the test system was constructed and the measurement of surface with various incline angles ranging from 5° to 60° was simulated. The experiments validate the simulation model and show the feasibility of profile reconstruction of inclined structure. It is interested to find that even with an inclined angle of 15°, unwrapping technique is required to make the measurement more accurate. In addition, the measurement can be further improved by taking into account the effects of the change in shear distance on the optical path difference. This study provides useful information that should be considered for complex geometry measurement with quantitative DIC technique.

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The Differential Interference Contrast approach (DIC) which is frequently used for image enhancement to increase the contrast between transparent object and its background is adopted for the dimensional measurement of a transparent structure. With the phase difference image retrieved using the DIC technique, the phase map of the examined object can be approximated by integrating the phase difference. Experimental results show the feasibility of using the transmitted DIC for transparent object measurement. The results show that the height of a transparent structure measured using the DIC method is quite close to those measured using AFM while those measured using the white light interference method results in much larger measurement than all others. However, when a structure is no longer a simple geometry, adopting this method directly might results in wrong results. In this paper, we would like to present the work had been done, discuss the challenge ahead, and possible approach can be adopted..