Measurement method of common optical path self-calibration film thickness and refractive index to eliminate transmitted light

Abstract

The invention discloses a transmitted-light-elimination common-optical-path self-calibration film thickness and refractive index measurement method and belongs to the optical measurement field. The method comprises the following steps of when a film to be measured is not inserted, opening a first optical switch, closing a second optical switch, driving an optical path scanning device to carry outoptical path scanning, and storing collected signals; closing the first optical switch, opening the second optical switch, driving the optical path scanning device to carry out optical path scanning,and storing the collected signals; demodulating the collected signals; if a nontransparent film thickness to be measured is measured, opening the first optical switch and the second optical switch, driving the optical path scanning device to carry out optical path scanning, carrying out optical path matching, and storing the collected signals; demodulating the collected signals and acquiring double optical paths; calculating the nontransparent film thickness to be measured; and when a transparent film thickness and a refractive index are measured, using a similar method. In the invention, themethod has many measurement functions; the influence of transmitted light can be eliminated and precision is increased; identification difficulty is reduced; optical path complexity is decreased; anda measurement speed is increased.

Description

technical field [0001] The invention belongs to the field of optical measurement, in particular to a method for measuring the thickness and refractive index of a common optical path self-calibration film that eliminates transmitted light. Background technique [0002] With the vigorous development of material science and technology, in order to meet the urgent needs of microelectronics, optoelectronics, new energy and other fields, thin films are widely used in optical engineering, mechanical engineering, communication engineering, biological engineering, aerospace engineering, chemical engineering, medical engineering and other fields. is widely used. The thickness of the film is not only one of the key parameters in film production, but also determines the application performance of the film in mechanical, electromagnetic, photoelectric and optical scenarios. Accurate measurement of film thickness has always been one of the most important links in film production and appl...

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Problems solved by technology

[0004] In 2013, the Chinese patent application No. 201310198294.9 disclosed an ultrasonic film thickness measuring instrument and its measurement method. The method transmits ultrasonic pulses incident on the surface of the oil film to resonate, and then measures the relative characteristics of the reflected pulses to the thickness of the oil film. However, this method is only suitable for the measurement of liquid models, and different models need to be established for films with different thickness ranges, which makes it difficult to demodulate

In 2014, Jia Chuanwu of Shandong University and others disclosed a system for measuring film thickness by wide-spectrum optical interferometry. , the thickness of the film to be tested can be obtained by measuring the length of the Fabry-Perot cavity before and after placing the film to be tested under the mirror. This method has a simple structure and high measurement accuracy. Under the mirror, it is easy to damage the morphology of the film surface

[0007] In 2017, the patent application number CN201710277954.0 disclosed a common optical path self-calibration film thickness measurement device and measurement method. Optical path, no need to calibrate devices, etc., but this method cannot eliminate the influence of laser transmitted light, resulting in cracking of laser interference signals and affecting thickness measurement accuracy; in 2017, a patent with application number CN201710277939.6 disclosed a polarization multiplexing Common optical path self-calibration film thickness measurement device and measurement method, this method can further eliminate the influence of transmitted light on the measurement results, but the device construction is more complicated

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