Second confocal measuring method and apparatus based on movable phase interfere

Abstract

The invention discloses a secondary confocal measurement method and device based on phase-shifting interference. In the device, a laser emits a linearly polarized beam, which becomes an approximate ideal plane wave after passing through a collimating beam expander group; After one-half of the wave plate, it becomes a circularly polarized beam; it is divided into two beams by the beam splitter, the first beam is transmitted by the beam splitter, reflected by the mirror, reflected by the beam splitter, and converged by the second pinhole and detected by the collecting objective lens. A point detector composed of detectors; the second beam of light is reflected by the beam splitter, converges on the measurement surface through the detection focusing objective lens and the beam splitter, is reflected on the measurement surface, passes through the detection focusing objective lens, and converges on the point detector through the collecting objective lens; the first The micro-driver is used to drive the mirror to change the phase difference between the reference light and the measurement light to realize phase-shifting interference; the initial position of the measurement point is the first confocal state. The invention also discloses a secondary confocal measurement method based on phase-shifting interference.

Description

technical field [0001] The invention belongs to the field of ultra-precision measurement, and is an ultra-precise non-contact measuring device for measuring three-dimensional microstructures, microsteps, microgroove line width, depth and surface shape in microstructured optical elements, microstructured mechanical elements, and integrated circuit elements. Fast, large-scale scanning measurement method and device. Background technique [0002] Confocal scanning measurement is one of the important technical means to measure three-dimensional microstructure, micro-step, micro-groove line width, depth and surface shape in the fields of micro-optics, micro-mechanics and micro-electronics. Its basic idea was proposed by M.Minsky in 1957 and obtained a US patent in 1961. Its basic idea is to suppress stray light by introducing a pinhole detector and generate axial tomography capabilities. The shortcomings of this technology The reason is that the measurement sensitivity of the axi...

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Problems solved by technology

Its basic idea was proposed by M.Minsky in 1957 and obtained a US patent in 1961. Its basic idea is to suppress stray light by introducing a pinhole detector and generate axial tomography capabilities. The shortcomings of this technology The reason is that the measurement sensitivity of the axial response signal is not high near the quasi-focus area of ​​the measurement surface, so it is only suitable for defocus displacement measurement

The essence of interferometry is to convert displacement changes into phase changes to achieve microstructure and micro-displacement measurement. This type of measurement technology well solves the problem of the influence of the measurement surface reflectivity and surface tilt on the measurement results. However, due to the phase measurement value solution has Periodicity, so this type of measurement method cannot be directly used for step height measurement, only relative displacement changes can be obtained, and it cannot be directly used for absolute displacement measurement

[0006] The invention provides a secondary confocal measurement method and device based on phase-shifting interference, which uses the axial tomography of the confocal detector to obtain phase information in two confocal states through two phase-shifting interferences, thereby realizing Analytical solution of defocus displacement, the purpose of the present invention is to overcome the shortcomings of traditional confocal measurement technology that is susceptible to the difference in the reflectivity of the measurement surface, the inclination of the measurement workpiece and the change of the surface profile, and the interferometric phase solution periodicity, which cannot be directly used for steps Insufficient measurement

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