CN-121559740-B - Double-focus optical system optimization method based on fundamental mode Gaussian beam

CN121559740BCN 121559740 BCN121559740 BCN 121559740BCN-121559740-B

Abstract

The invention relates to the technical field of optical system design and optimization, and discloses a double-focus optical system optimization method based on a fundamental mode Gaussian beam. The method comprises the steps of constructing a light field transmission model based on a generalized Huygens-Fresnel diffraction principle, and calculating to obtain the emergent field and the on-axis light intensity distribution after passing through a bifocal system. And identifying a main maximum point of the light intensity, calculating the offset between the main maximum point and the geometric focus, forming a criterion for occurrence of a quantized focal switching phenomenon, and further analyzing the stability of the focus. On the basis, the optical beam cutoff parameter and the Fresnel number are subjected to joint iterative optimization, the system parameters are adjusted until the stability meets a preset threshold value, and finally an optimized system configuration scheme is output. The method can effectively predict and inhibit focus position jump caused by physical optical effect in the design stage, and improve the reliability and stability of the bifocal system in actual work.

Inventors

LI MAO
LI CUI
YANG JIHUA
Pu Yanyu
ZENG XIN
WEN JIE

Assignees

中国测试技术研究院

Dates

Publication Date: 20260508
Application Date: 20260120

Claims (9)

1. A method for optimizing a bifocal optical system based on a fundamental mode gaussian beam, the method comprising: acquiring a system parameter set of a bifocal optical system, and constructing an initial light field model for describing the transmission of a fundamental mode Gaussian beam through the bifocal optical system based on a generalized Huygens-Fresnel diffraction integral formula; Inputting the system parameter set and the beam parameters of the fundamental mode Gaussian beam into the initial light field model for transmission calculation to obtain an emergent field distribution function of the beam after passing through the bifocal optical system; Calculating the light intensity distribution of the fundamental mode Gaussian beam on a transmission axis based on the emergent field distribution function, and generating on-axis light intensity distribution data; Performing light intensity main maximum position detection processing on the on-axis light intensity distribution data, and identifying at least two main light intensity maximum points and corresponding focal positions thereof; calculating a criterion of occurrence of a focus switching phenomenon according to the offset of the focus position and the geometric focus position, and generating a focus stability analysis result; based on the focus stability analysis result, carrying out joint optimization adjustment on the light beam cutoff parameters and the light beam Fresnel number in the system parameter set to generate an optimized system parameter set; inputting the optimized system parameter set into the generalized Huygens-Fresnel diffraction integral formula for iterative calculation until the focus stability analysis result meets a preset focus stability threshold condition, and generating a final optimized bifocal optical system configuration scheme; The step of generating an optimized system parameter set by performing joint optimization adjustment on the beam cutoff parameter and the beam fresnel number in the system parameter set based on the focus stability analysis result, includes: when the focus stability analysis result is in a focus unstable state, reading a light beam cutoff parameter critical value and a light beam Fresnel number critical value which cause a focus switching phenomenon; taking the light beam cutoff parameter critical value and the light beam Fresnel number critical value as references, respectively carrying out step adjustment along the increasing direction and the decreasing direction in a parameter space to generate a plurality of groups of light beam cutoff parameter candidate values and light beam Fresnel number candidate values; combining each group of the beam cutoff parameter candidate values with the beam Fresnel number candidate values, and replacing corresponding parameters in the original system parameter set to form a plurality of candidate system parameter sets; substituting each candidate system parameter set into the generalized Huygens-Fresnel diffraction integral formula to perform focus stability verification calculation; Screening the candidate system parameter set which enables the focus stability analysis result to be converted into a stable state, and taking the candidate system parameter set as the optimized system parameter set.
2. The method for optimizing a bifocal optical system based on a fundamental mode gaussian beam according to claim 1, wherein the acquiring a system parameter set of the bifocal optical system constructs an initial light field model for describing transmission of the fundamental mode gaussian beam through the bifocal optical system based on a generalized huygens-fresnel diffraction integral formula, comprising: The system parameter set comprises the Fresnel half-wave band number of the Fresnel zone plate, the focal length of the thin lens and the light beam cutoff parameter of the optical system; Acquiring the beam waist radius and the beam wavelength of the fundamental mode Gaussian beam, and constructing an initial light field expression of the fundamental mode Gaussian beam; performing product operation on the complex amplitude transmittance function of the Fresnel zone plate and the phase transformation function of the thin lens to generate a complex transmittance function of the bifocal optical system; Multiplying the initial light field expression of the fundamental mode Gaussian beam with the composite transmittance function to obtain a modulated light field expression at the incidence plane of the bifocal optical system; Substituting the modulated light field expression into a generalized Huygens-Fresnel diffraction integral formula to obtain an emergent field integral expression of the light beam at any observation plane behind the bifocal optical system, and taking the emergent field integral expression as the initial light field model.
3. The method of optimizing a bifocal optical system based on a fundamental mode gaussian beam according to claim 1, wherein said calculating an on-axis light intensity distribution of the fundamental mode gaussian beam based on the exit field distribution function, generating on-axis light intensity distribution data, comprises: Limiting the position coordinates of the observation plane of the emergent field distribution function on a transmission shaft to obtain a simplified emergent field function at an on-shaft observation point; Calculating the product of the simplified emergent field function and the complex conjugate function thereof to obtain light intensity values at each point on the axis, and generating an initial on-axis light intensity distribution sequence; normalizing the initial on-axis light intensity distribution sequence to enable the maximum value of the light intensity to be a reference value, and generating normalized on-axis light intensity distribution data; and carrying out high-density sampling on the normalized on-axis light intensity distribution data along the transmission axis direction to generate continuous on-axis light intensity distribution data.
4. The method for optimizing a bifocal optical system based on a gaussian beam according to claim 1, wherein said performing a light intensity main maximum position detection process on the on-axis light intensity distribution data identifies at least two main light intensity maximum points and their corresponding focal positions, comprises: obtaining a first derivative of the on-axis light intensity distribution data to obtain a light intensity change rate sequence; identifying zero crossing points from positive to negative in the light intensity change rate sequence to obtain a potential light intensity extreme point set; calculating a light intensity value corresponding to each position in the potential light intensity extreme point position set, and screening out a light intensity extreme point with the light intensity value exceeding a preset main maximum threshold value as a candidate main maximum point; Performing local peak verification processing on the candidate main maximum points, screening out points with the highest light intensity values in a preset neighborhood range, and determining the points as the light intensity main maximum points; and reading the corresponding coordinates of the light intensity main maximum point on a transmission shaft as the focus position.
5. The method for optimizing a bifocal optical system based on a fundamental mode gaussian beam according to claim 1, wherein said calculating a criterion for occurrence of a focal switching phenomenon according to an offset between the focal position and a geometric focal position, generating a focal stability analysis result, comprises: Obtaining geometrical focus position coordinates from the system parameter set; Calculating the absolute distance between each focus position and the geometric focus position coordinate as a focus offset; judging whether any focus offset exceeds a preset focus switch threshold distance; if the focus stability analysis result is the same as the focus stability analysis result, judging that the focus switch phenomenon occurs in the bifocal optical system, and marking the unstable focus state and the focus position of the occurrence focus switch in the focus stability analysis result; if not, marking the focus stable state in the focus stability analysis result.
6. The method for optimizing a bifocal optical system based on a fundamental mode gaussian beam according to claim 5, further comprising performing correction processing based on a criterion of occurrence of fresnel half-wave band number focus switching phenomenon, comprising: judging the parity of the Fresnel half-wave band number in the system parameter set; If the number of the Fresnel half-wave bands is even, adjusting the Jiao Kaiguan threshold distance to be a preset even half-wave band threshold distance; If the number of the Fresnel half-wave bands is an odd number, adjusting the Jiao Kaiguan threshold distance to be a preset odd number half-wave band threshold distance, and setting a light intensity value weight factor at a geometric focus; and recalculating the focus stability analysis result based on the Jiao Kaiguan threshold distance and the light intensity value weight factor after adjustment.
7. The method of optimizing a basic-mode gaussian beam-based bifocal optical system according to claim 6, wherein said substituting each of said candidate system parameter sets into said generalized huyghen-fresnel diffraction integral formula for focus stability verification calculation comprises: updating system parameters in the generalized Huygens-Fresnel diffraction integral formula by using the candidate system parameter set; Recalculating an emergent field distribution function of the fundamental mode Gaussian beam after passing through the bifocal optical system based on the updated generalized Huygens-Fresnel diffraction integral formula; generating new on-axis light intensity distribution data based on the recalculated exit field distribution function; Performing light intensity main maximum position detection processing on the new on-axis light intensity distribution data to obtain a new focus position; And judging whether the new focus position meets a focus stability condition, wherein the focus stability condition is that the offset of all focus positions and geometric focus positions is smaller than a preset focus stability tolerance threshold.
8. The method for optimizing a bifocal optical system based on a fundamental mode gaussian beam according to claim 1, wherein the step of inputting the optimized system parameter set into the generalized huyghen-fresnel diffraction integral formula to perform iterative computation until the focus stability analysis result meets a preset focus stability threshold condition, and generating a final optimized bifocal optical system configuration scheme includes: taking the optimized system parameter set as the system parameter input of the current iteration, and calculating to obtain the focus stability analysis result of the current iteration; judging whether the maximum focus offset in the focus stability analysis result of the current iteration is smaller than the focus stability threshold condition or not; If the parameter set is smaller than the preset threshold value, determining the optimized system parameter set of the current iteration as the final optimized bifocal optical system configuration scheme; if the number of the beam cutoff parameters and the number of the beam Fresnel in the optimized system parameter set are not smaller than the number of the beam Fresnel in the optimized system parameter set, fine tuning is carried out according to the focus stability analysis result of the current iteration, and the optimized system parameter set of a new iteration is generated; and repeating the iterative optimization step until the focus stability threshold condition is met or the preset maximum iterative times are reached.
9. A method for optimizing a bifocal optical system based on a fundamental mode gaussian beam, the method comprising: acquiring a system parameter set of a bifocal optical system and beam parameters of a fundamental mode Gaussian beam; An initial light field model is built based on a generalized Huygens-Fresnel diffraction integral formula, and an emergent field distribution function of a light beam after passing through the system is calculated; Calculating light intensity distribution on a transmission shaft according to the emergent field distribution function, and identifying a focus position corresponding to a light intensity main maximum point; Analyzing the deviation of the focus position and the geometric focus position, judging the focus switching phenomenon and generating a focus stability analysis result; and based on the analysis result of the focal stability, carrying out joint optimization adjustment on the light beam cutoff parameters and the light beam Fresnel number in the system parameter set, and carrying out iterative calculation through the generalized Huygens-Fresnel diffraction integral formula until the focal stability meets a preset threshold value, so as to generate a final optimized bifocal optical system configuration scheme.

Description

Double-focus optical system optimization method based on fundamental mode Gaussian beam Technical Field The invention relates to the technical field of optical system design and optimization, in particular to a double-focus optical system optimization method based on a fundamental mode Gaussian beam. Background In the fields of laser applications, optical communications, precision measurements, etc., there is a need for an optical system that can produce two or more separate and stable focal points. The prior art generally designs bifocal optical systems based on geometric optical theory, by combining optical elements to achieve bifocal at predetermined positions. This method is conceptually straightforward and relatively simple to calculate, but does not take into account the physical optical transmission characteristics of the actual laser beam, in particular the fundamental mode gaussian beam. The design method based on geometric optics has the defect that the default focus position is fixed and is uniquely determined by a geometric light path, so that the fluctuation of the light beam, particularly the combined action of diffraction effect and a system diaphragm on the light beam, is ignored. In actual physical optical transmission, when a gaussian beam passes through a limited optical system, the on-axis light intensity distribution of the gaussian beam can change in a complex manner, a plurality of maximum values with similar intensities can appear, and the position of the main maximum value can generate discontinuous and sudden jump along with the tiny change of the beam parameters, namely 'Jiao Kaiguan' phenomenon. This results in deviations of the actual focal position of the system from the design value, and even unpredictable switching between two predetermined positions under different conditions, severely damaging the stability and reliability of the system output, which is a fundamental problem not solved by conventional design methods. A central challenge faced by current bifocal optical system designs is how to effectively predict and suppress focal position instability induced by physical optical effects. This requires that the design approach must go beyond the geometrical optics framework, be able to quantitatively evaluate the risk of focus jump, and be targeted optimized from the system parameter level to ensure that under actual physical beam transport conditions, the bifocal position can remain stable as intended. Disclosure of Invention The invention aims to provide a double-focus optical system optimization method based on a fundamental mode Gaussian beam, so as to solve the problems in the background art. To achieve the above object, the present invention provides a method for optimizing a bifocal optical system based on a fundamental mode gaussian beam, the method comprising: acquiring a system parameter set of a bifocal optical system, and constructing an initial light field model for describing the transmission of a fundamental mode Gaussian beam through the bifocal optical system based on a generalized Huygens-Fresnel diffraction integral formula; Inputting the initial light field model, the system parameter set and the beam parameters of the fundamental mode Gaussian beam into the initial light field model for transmission calculation to obtain an emergent field distribution function of the beam after passing through the bifocal optical system; Calculating the light intensity distribution of the fundamental mode Gaussian beam on a transmission axis based on the emergent field distribution function, and generating on-axis light intensity distribution data; Performing light intensity main maximum position detection processing on the on-axis light intensity distribution data, and identifying at least two main light intensity maximum points and corresponding focal positions thereof; calculating a criterion of occurrence of a focus switching phenomenon according to the offset of the focus position and the geometric focus position, and generating a focus stability analysis result; based on the focus stability analysis result, carrying out joint optimization adjustment on the light beam cutoff parameters and the light beam Fresnel number in the system parameter set to generate an optimized system parameter set; And inputting the optimized system parameter set into the generalized Huygens-Fresnel diffraction integral formula to perform iterative calculation until the focus stability analysis result meets a preset focus stability threshold condition, and generating a final optimized bifocal optical system configuration scheme. Preferably, the acquiring the system parameter set of the bifocal optical system constructs an initial light field model for describing the transmission of the fundamental mode gaussian beam through the bifocal optical system based on a generalized huyghen-fresnel diffraction integral formula, and the method includes: The system parameter set comprises the Fresne