Meta-surface-based spectral confocal displacement measurement method, device thereof and storage medium

A meta-surface-based spectral confocal displacement measurement method, comprising:

• arranging a meta-surface opposite to a collimating lens, and using micro-nano structures on the meta-surface to allow different wavelengths of broadband parallel light passing through the collimating lens to have different focal lengths to obtain a focal length sequence;
• wherein a method for obtaining the focal length sequence comprises:
• acquiring a central wavelength and a corresponding central focal length value, and obtaining a phase curve according to the arrangement manner of the micro-nano structures;
• solving a focal length calculation model based on the phase curve, the coordinate in the y direction and a number of periodic spaces of the micro-nano structures in the y direction to obtain other focal length values;
• and arranging the central focal length value and the other focal length values to obtain the focal length sequence;
• wherein the focal length calculation model is:
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• where λi∈Λ, Λ=[λ1, λ2, . . . , λmid, . . . , λn-1, λn], Λ denotes wavelength sequence data, and λmid denotes the central wavelength;
• fi∈F, F=[f1, f2, . . . , fmid, . . . , fn-1, fn], F denotes the focal length sequence, and fmid denotes the central focal length value;
• φ(λmid,fmid,ra) denotes the phase curve obtained from the central wavelength and the central focal length value,
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• ra denotes a coordinate in the y direction, Amid and m denotes the number of the periodic spaces of the micro-nano structures in the y direction;
• and
• obtaining spectral signals by a spectrometer to output wavelength sequence data and light intensity sequence data when a measured object is located in the focal length sequence, calculating a peak wavelength λ0 according to the wavelength sequence data and the light intensity sequence data, and calculating the measurement result Z0 according to the peak wavelength;
• wherein an arrangement manner of the micro-nano structures is determined according to a working phase and a working focal length of the micro-nano structures and a working wavelength of the broadband parallel light;
• and the working phase of the micro-nano structures is determined according to a size of the micro-nano structures, the working wavelength of the broadband parallel light, a refractive index of air, and a refractive index of material of the micro-nano structures.