Differential confocal-low coherent interference combination refractivity and thickness measurement method and apparatus

Abstract

The invention belongs to the technical field of optical precision measurement and relates to a measurement method for the combined refractive index and thickness of differential confocal aspect and low coherence interference and a device. The method first determines the positions of a measuring objective and a reference part corresponding to the front surface position and back surface position of a measured sample respectively through differential confocal and focus principle and low coherence interference principle, and then measures the displacement distance Delta z of the measuring objective and the displacement distance Delta l of the reference part, and the displacement distances are substituted into a formula to calculate the refractive index and thickness of the measured sample. The invention first proposes the use of the characteristic that a differential confocal response curve corresponds to the focus of a micro objective in zero crossing for realizing precise focus and extends the differential confocal micro principle to the refractive index and thickness measurement field, forming the differential confocal thickness measuring principle. By integrating the differential confocal and focus principle and low coherence interference technology, the invention has the advantages of high measurement precision and strong capability of resisting ambient interference and can be applied to the detection of the refractive index and thickness of a sample.

Description

technical field [0001] The invention belongs to the technical field of optical precision measurement and can be used for high-precision measurement of group refractive index, phase refractive index and geometric thickness of optical plates and thin films. technical background [0002] Refractive index and geometric thickness are very important basic physical parameters of optical devices. They reflect a lot of information about optical devices, and are also related to other parameters of optical devices (such as photothermal coefficient). Precise and independent measurement of refractive index of optical devices and geometric thickness are very difficult. As the basic parameters of optical devices, the independent precise measurement of refractive index and geometric thickness has always been a difficult point in the field of optical measurement. The main factors are: the measurement of refractive index is often associated with thickness measurement, and the measurement requ...

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Problems solved by technology

[0007] The purpose of the present invention is to solve the problem of high-precision measurement of the refractive index and geometric thickness of optical plates and films, and proposes a method that uses the characteristics of the target position corresponding to the focus of the microscope when the differential confocal response curve crosses zero and the contrast of low coherent interference fringes The maximum value corresponds to the characteristics of the optical path such as the reference optical path and the measurement optical path to achieve accurate measurement, which significantly improves the measurement accuracy of the geometric thickness and refractive index of the sample

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