A method for real-time measurement of mueller matrix spectra

Abstract

The invention discloses a system for measuring the spectrum of Mueller matrix in real time. instrument, Wollaston prism, spectrometer group. The invention also discloses a method for real-time measurement of Mueller matrix spectrum. Fourier transform, channel filtering and inverse Fourier transform are performed on the spectral intensity obtained by the spectrometer to restore the Stokes vector S emitted from the surface of the tested sample. The spectrum of 16 Mueller matrix elements can be recovered by performing Fourier transform, channel filtering and inverse Fourier transform on the Stokes parameters. The invention avoids channel crosstalk, has high measurement accuracy and strong operability.

Description

technical field [0001] The invention belongs to the technical field of polarization spectrum measurement, relates to a system for real-time measurement of Mueller matrix spectrum, and also relates to a method for real-time measurement of Mueller matrix spectrum. Background technique [0002] The Mueller matrix can completely describe the polarization response properties of an object to light. By obtaining the Mueller matrix spectrum of the measured sample, many optical characteristics of the measured sample can be obtained, such as depolarization effect, surface etching anisotropy and cross-section asymmetry . As a new type of optical detection method, Mueller matrix spectral measurement technology has broad application prospects in the fields of integrated circuit manufacturing, flat panel display, biomedical diagnosis and so on. At present, only a few scientific research institutions in the world carry out relevant research work. In particular, the instrument for real-ti...

AI Technical Summary

Problems solved by technology

At present, only a few scientific research institutions in the world carry out relevant research work

In particular, the instruments for real-time acquisition of Mueller matrix spectra are still in the stage of principle exploration and experimental verification, and their technical means are not yet mature.

[0003] At present, there are mainly two types of conventional Mueller matrix spectral measurement methods in the world: one is carried out in time order, and the compensator of the polarizer arm and the polarizer arm is set at a certain rate ratio 5ω:mω (ω is the base of the coaxial motor. Frequency, m is a non-zero integer and not equal to 5 or 10) Rotation produces different time modulation frequencies, and obtaining all 16 Mueller matrix elements of the sample through Fourier transform demodulation requires detector readings N=4m+21 times to ensure The complete waveform analysis is completed within one optical period T=π / ω, and the time spent is t=N×t 0 (t 0 is the readout time of the detector), the longer measurement time is not suitable for the situation where the measured Mueller matrix changes rapidly with time, and the two moving parts in the system increase the probability of system error

The other is to modulate all 16 elements of the measured Mueller matrix to 37 different frequency channels through frequency modulation, and use channel filtering and Fourier transform demodulation to obtain the spectrum of all 16 elements of the Mueller matrix. Since there are no moving parts in the system, static real-time measurement can be realized (the measurement time is determined by the detector readout time), but when the measured Mueller matrix has sharp characteristic peaks, there will be serious channel crosstalk, which will affect the measurement accuracy and precision , and the spectral resolution of the restored Mueller matrix is ​​much smaller than that of the spectrometer, so it is only suitable for the case where the measured Mueller matrix changes slowly with wavelength

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