Method for measuring wavefront aberration of simplified system of terminal optical component

Abstract

According to an inverse Hartmann wavefront detection principle, the invention provides a wavefront aberration measurement method for a simplified system of a terminal optical component. According to the method, a wavefront aberration measurement system is formed by a camera and a display, phase shift stripes are displayed on the display to serve as a structured light source, the camera collects stripe patterns modulated and emitted by a to-be-measured system, phase information is obtained based on a phase shift algorithm, and then coordinates of the display are obtained; and the coordinates of the emergent surface of the to-be-measured system are obtained through ray tracing in combination with system calibration parameters, and finally the slope of the actual emergent ray of the to-be-measured optical system can be obtained, so that the wavefront aberration is obtained. The device has the advantages of simple structure, low detection cost, high precision and high resolution.

Description

Technical Field

[0001] This invention relates to a simplified device for wavefront aberration measurement based on transmission-phase measurement deflectometry, particularly for coaxial optical systems that include combined transparent elements such as frequency doubling crystals. Background Technology

[0002] As a key component of inertial confinement fusion devices, the terminal optical assembly primarily functions to achieve laser transmission and frequency conversion. In this system, KDP crystals are widely used due to their excellent nonlinear optical properties and large-aperture growth capabilities. However, even ideal crystals are affected by their own properties and external influences, and lens fabrication itself introduces aberrations, leading to distortion and aberrations in the final emitted wavefront. Wavefront aberration is a crucial indicator of the rationality of optical system design, providing rich feedback information for the design and fabrication of optical systems. This is especially important for large, complex optical systems like the terminal optical assembly, where component design and alignment issues can cause system malfunctions. Currently, the main wavefront aberration measurement methods are interferometry, such as the Twyman-Green interferometer and the Fizeau interferometer. Interferometers typically offer high accuracy, but are limited by the accuracy of the reference surface, laser wavelength, and sensor spectral sensitivity. Their low flexibility makes them unsuitable for online or in-situ measurements, thus restricting their in-situ applications. Secondly, methods based on wavefront slope measurement, such as Hartmann detection and Shack-Hartmann wavefront sensors, have limitations. The former has limited resolution, while the latter's accuracy is constrained by the microlens array process, resulting in a low dynamic range. Other methods include Moiré deflection and star point testing. Moiré deflection has strong anti-interference capabilities, but its accuracy is affected by grating quality, while star point testing is affected by light source quality and environmental factors. Lai et al. used transmission phase measurement deflection to measure lens wavefront aberrations; Yu et al. proposed using transmission phase measurement deflection for imaging lens wavefront aberration measurement; Xu et al. also proposed using transmission phase measurement deflection to measure wavefront aberrations in industrial glass tubes to obtain wavefront aberrations caused by processing errors in transmission elements; Xu and Fan et al. used transmission phase measurement deflection to achieve high-precision wavefront detection of freeform spectacle lenses to determine whether they meet production requirements; Zhang et al. used transmission phase measurement deflection to obtain full-field information of gradient refractive index lenses, providing guidance for lens manufacturing. Summary of the Invention

[0003] In view of the above problems, this invention proposes a simplified wavefront aberration measurement method for terminal optical components based on transmission deflection. This method utilizes a camera and a display to form a wavefront aberration measurement system. Phase-shifted fringes are displayed on the display as a structured light source. The camera acquires the fringe pattern modulated and emitted by the system under test. The phase information is then obtained based on the phase-shifting algorithm, leading to the display coordinates. An experimental model is established in a computer using system calibration parameters. Ray tracing is used to obtain the coordinates of the system's output surface, ultimately yielding the slope of the actual emitted light from the optical system under test, and thus the wavefront aberration. This method has the advantages of simple device, low detection cost, high accuracy, and high resolution.

[0004] The technical solution adopted in this invention is a simplified wavefront aberration measurement method for terminal optical components based on transmission deflection. Based on the inverse Hartmann wavefront detection principle, this invention examines the main factors of wavefront distortion in the system (KDP crystal and focusing lens, hereinafter referred to as the system under test) and establishes a transmission deflection wavefront aberration measurement system. Starting from the principle of inverse Hartmann wavefront detection, the camera is considered as a point light source, and the light rays are assumed to originate from the center of the entrance pupil of the camera lens, be deflected by the optical system under test, and reach the display. By combining ray tracing and phase-shifting algorithms to calibrate system parameters, the coordinates of the system's exit surface and the corresponding display coordinates are obtained, thereby completing the calculation of the slope of the emitted light rays from the optical system. Integrating the slope yields the wavefront aberration of the optical system under test. The specific steps of this method are as follows:

[0005] Step 1: Coaxial adjustment of camera and monitor

[0006] Using a high-precision electrically controlled displacement stage equipped with a point light source microscope for coaxial adjustment, the monitor's orientation was first adjusted to align with the world coordinate system. First, the surfaces coincide; second, a custom aperture stop is installed in front of the camera, and a point light source microscope is used to adjust the position of the aperture stop and the camera's orientation to ensure that the camera's optical axis and the display are coaxial in the world coordinate system.

[0007] Step 2: Obtaining the direction of the incident light from the system

[0008] The monitor displays a phase-shifted fringe pattern. Without introducing the system under test, a camera captures an image of the fringe on the monitor, and the monitor coordinates under no-load conditions are calculated using a phase-shift algorithm. The direction of incident light when the camera is considered a point light source is calculated based on the total working distance of the system. :

[0009] (1)

[0010] in, They are respectively The direction cosine of the direction.

[0011] Step 3: Obtaining the coordinates of the exit surface and the display of the system under test

[0012] An experimental model was established in a computer based on the calibration parameters of the system under test and the experimental setup. Ray tracing was performed according to the vector refraction law and the direction of the incident ray to obtain the coordinates of the exit surface after being introduced into the system under test. , At this point, a stripe image is captured by the camera and modulated by the system. The display coordinates in this state are then calculated using a phase-shifting algorithm. Then the wavefront aberration of the optical system can be expressed as:

[0013] (2)

[0014] In the formula The refractive index is the object-space refractive index. They are the actual light and the ideal light, respectively. The angle in the direction. Then, the Zernike polynomial is used to integrate the slope data obtained from the line-of-sight calibration using the pattern method; similarly, the system's e-wavefront aberration can be obtained. . Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the system device of the present invention;

[0016] Figure 2 This is the phase-shifted fringe pattern displayed on the monitor in this invention. Detailed Implementation

[0017] To make the objectives and solutions of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and examples. It should be noted that the following embodiments are only for further illustration and should not be construed as limiting the scope of protection of this invention. Any non-essential improvements and adjustments made to this invention by those skilled in the art based on the above description are still within the scope of protection of this invention.

[0018] This invention provides a simplified wavefront aberration measurement method for terminal optical components based on transmission deflection. The basic components include a CCD camera 1, a system under test 2, a display 3, and a computer for control and data processing. The method utilizes the display 3 to show, for example... Figure 2The phase-shifted fringes shown serve as a structured light source. Camera 1 acquires the fringe pattern modulated and emitted by the system under test (SUT2). Phase information is then obtained based on the phase-shifting algorithm, leading to the display coordinates. An experimental model is built in a computer using system calibration parameters. Ray tracing is used to obtain the coordinates of the output surface of SUT2, ultimately yielding the slope of the actual emitted light from SUT2, and thus the wavefront aberration. The specific implementation process is as follows:

[0019] Step 1: Coaxial adjustment of camera and monitor

[0020] Using a high-precision electrically controlled displacement stage equipped with a point light source microscope for coaxial adjustment, the orientation of display 3 was first adjusted to align with the world coordinate system. First, the surfaces coincide; second, a custom aperture stop is installed in front of camera 1, and a point light source microscope is used to adjust the position of the aperture stop and the orientation of camera 1 to ensure that camera 1 and display 3 are coaxial in the world coordinate system.

[0021] Step 2: Obtaining the direction of the incident light from the system

[0022] The phase-shifted fringe pattern is displayed on monitor 3. Without introducing the system under test, the fringe image of the monitor is captured by camera 1, and the monitor coordinates under no-load conditions are calculated using a phase-shifting algorithm. The direction of the incident light ray when camera 1 is regarded as a point light source is calculated based on the total working distance of the system. :

[0023] (1)

[0024] in, They are respectively The direction cosine of the direction.

[0025] Step 3: Obtaining the coordinates of the exit surface and the display of the system under test

[0026] An experimental model was established in a computer based on the calibration parameters of the system under test and the experimental setup. Ray tracing was performed according to the vector refraction law and the direction of the incident ray to obtain the coordinates of the exit surface after being introduced into the system under test. , At this time, the stripe image captured by camera 1 and modulated by the system after being introduced into the system under test 2 is used to calculate the coordinates of display 3 in this state. Then the wavefront aberration of the o-ray of the optical system 2 under test can be expressed as:

[0027] (2)

[0028] In the formula The refractive index is the object-space refractive index. They are the actual light and the ideal light, respectively. The angle in the direction. Then, the Zernike polynomial is used to integrate the slope data obtained from the line-of-sight calibration using the pattern method. Similarly, the wavefront aberration of the e-ray of the system under test can be obtained. .

Claims

1. A simplified wavefront aberration measurement method for terminal optical components, comprising a camera, a display, a system under test (SUT), an electrically controlled displacement stage with a microscope equipped with a point light source, an optical platform, and a computer for control and data processing. The method utilizes a camera and a display to form a wavefront aberration measurement system. Phase-shifted fringes are displayed on the display. The camera acquires the fringe pattern modulated and emitted by the SUT. Phase information is obtained based on a phase-shift algorithm, leading to the display coordinates. An experimental model is established in the computer using system calibration parameters. Ray tracing is used to obtain the coordinates of the system's output surface, ultimately yielding the slope of the actual emitted rays from the optical system and thus the wavefront aberration. The specific steps are as follows: Step 1: Coaxial adjustment of camera and monitor Using a high-precision electrically controlled displacement stage equipped with a point light source microscope for coaxial adjustment, the monitor's orientation was first adjusted to align with the world coordinate system. First, the surfaces coincide; second, a custom aperture stop is installed in front of the camera, and a point light source microscope is used to adjust the position of the aperture stop and the camera's orientation to ensure that the camera's optical axis and the display are coaxial in the world coordinate system. Step 2: Obtaining the direction of the incident light from the system The monitor displays a phase-shifted fringe pattern. Without introducing the system under test, a camera captures an image of the fringe pattern on the monitor. The monitor coordinates under no-load conditions are then calculated using a phase-shift algorithm. The direction of incident light when the camera is considered a point light source is calculated based on the total working distance of the system. : (1) in, They are respectively The direction cosine; Step 3: Obtaining the coordinates of the exit surface and the display of the system under test An experimental model was established in a computer based on the calibration parameters of the system under test and the experimental setup. Ray tracing was performed according to the vector refraction law and the direction of the incident ray to obtain the coordinates of the exit surface after being introduced into the system under test. , At this point, a stripe image is captured by the camera and modulated by the system after being introduced into the system under test. The display coordinates in this state are then calculated using a phase-shifting algorithm. Then the wavefront aberration of the optical system can be expressed as: (2) In the formula The refractive index is the object-space refractive index. They are the actual light and the ideal light, respectively. The angle in the direction; then the Zernike polynomial is used to integrate the slope data obtained from the line-of-sight calibration using the pattern method, and similarly, the wavefront aberration of the system's e-ray can also be obtained. .

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