Device and method for detecting change of reflected light

Abstract

The invention provides a device and method for detecting the change of reflected light, and the method comprises the steps: transmitting an incident light beam with a first polarization state, and carrying out the field intensity segmentation of the incident light beam with the first polarization state, so as to form first field intensity distribution; collimating and converging the incident light beam with the first polarization state and the first field intensity distribution to irradiate to the surface of an object so as to form a reflected light beam with the first polarization state and the second field intensity distribution; receiving the reflected light beam with the first polarization state and the second field intensity distribution in the view field range, and collimating the reflected light beam to form a reflected light beam with the first polarization state and the third field intensity distribution; after the reflected light beam with the first polarization state and the third field intensity distribution is adjusted to the second polarization state, carrying out field intensity segmentation on the reflected light beam with the second polarization state and the third field intensity distribution to form a reflected light beam with the second polarization state and the fourth field intensity distribution; analyzing the change information of the reflected light beam with the second polarization state and the fourth field intensity distribution in the time interval, and analyzing the change information of the reflected light beam with the fourth field intensity distribution in the time interval on the basis of realizing the separation of the incident light beam and the emergent light beam of the detection light by utilizing different polarization states. Therefore, the signal change formed by the light intensity change and the imaging position deviation after analysis is enhanced, and the signal-to-noise ratio of the detector is improved.

Description

technical field [0001] The invention belongs to an acousto-optic measuring system and is mainly used for measuring metal films and dielectric films. Specifically, it relates to a device and method for detecting changes in reflected light. Background technique [0002] At present, the principle of acousto-optic measurement in the prior art is as follows: a short-pulse laser is irradiated on the surface of a film sample, and the film sample absorbs photons to generate thermoelastic deformation, forming a deformation zone on the surface; thermoelastic deformation generates photoacoustic signals that propagate on the solid surface and inside; The longitudinal sound wave propagates to the interface (the junction of the substrate or the film and the film) to generate the first echo signal; the first echo signal reaches the upper surface, causing the deformation to change further; the echo signal rebounds after hitting the upper surface, After the rebound hits the interface, a seco...

AI Technical Summary

Problems solved by technology

[0005] However, in the above-mentioned technical solution, there are the following problems: the first problem is that the position adjustment accuracy of the first reflector 6c of the applied optical system is extremely high, and its stability is also extremely high. Assuming the role of splitting the field of view of the light spot, the requirements for the collimation and stability of the optical path are relatively high, and the assembly of the optical path is relatively difficult; the second aspect is reflected in the complexity of the optical path, which requires the assembly of the first reflector 6c and The second reflector 6d, and in order to meet the requirement that the incident light within a certain angle can be effectively reflected and refracted, the parallel collimation and field of view interlacing between the two also need to be precisely adjusted and designed. At the same time, it is necessary to detect the outgoing light. Two detectors, the increase in the use of optical components will also lead to an increase in cost; the third aspect is reflected in the detection accuracy, due to the use of light splitting for the optical path, the transmission and reflection light is further lost, and the incident angle of the reflection detection light due to the deformation zone The change rate of spot energy decomposition caused by the deviation is more difficult to detect, so the detection signal-to-noise ratio is low, about one in a million, and the requirements for the divergence angle of the detection beam waist are extremely high

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