Autocollimator Wavefront Correction for Angle Measurement
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Solution Overview
Problem
Traditional photoelectric autocollimators face challenges in achieving high-resolution, high-accuracy, and high-stability angle measurements due to limitations in their optical systems, sensors, and susceptibility to environmental disturbances, particularly in long-distance and complex environments.
Innovation Solution
A two-dimensional photoelectric autocollimation method and device that incorporates wavefront measurement and correction using a deformable mirror, polarization beam splitters, and a telephoto objective lens group to compensate for aberrations and external disturbances, enhancing the measurement accuracy and stability by improving the imaging quality and spot positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single-lens optical system is used, then the device complexity is low, but the manufacturing precision and measurement precision are insufficient due to large aberration and spot positioning errors
Solution Approach 1:
The single lens is divided into multiple lens elements (first convex lens, concave lens, second convex lens) arranged in a specific sequence. This segmentation allows each lens element to contribute to correcting specific types of optical aberrations, achieving superior image quality and spot positioning accuracy compared to a single-lens system.
Solution Approach 2:
The patent uses a composite optical system combining different types of lenses (convex and concave) with specific focal lengths and aperture ratios. This composite structure leverages the complementary properties of different lens types to correct various aberrations while maintaining a compact form factor.
2Reliability
If a traditional laser light source is used, then the ease of operation is simple, but the stability is poor due to beam parallel drift and angular drift
Solution Approach 1:
The patent introduces a feedback mechanism where the wavefront sensor continuously monitors the reference beam for drift, and the deformable mirror adjusts in real-time to compensate for detected deviations. This closed-loop feedback system maintains beam stability despite environmental disturbances, achieving sub-microradian measurement accuracy.
Solution Approach 2:
The deformable mirror acts as an intermediary between the unstable laser source and the measurement system. It dynamically adjusts its surface shape to correct beam drift and distortion, transforming the unstable input beam into a stable, well-collimated output beam suitable for precise autocollimation measurements.
3Measurement precision
If no wavefront correction is applied, then the device complexity is low, but the measurement precision is limited by air disturbances and external interference in long-distance measurements
Solution Approach 1:
The wavefront sensor and deformable mirror serve as intermediary components that actively compensate for disturbances in the optical path. The wavefront sensor measures distortions caused by air turbulence and external interference, while the deformable mirror corrects these distortions, enabling precise measurements over long distances despite environmental challenges.
Solution Approach 2:
The patent replaces passive mechanical stabilization methods with active optical correction using a deformable mirror. Instead of mechanically isolating the system from vibrations and disturbances, it uses real-time wavefront sensing and optical phase correction to compensate for environmental effects, achieving higher precision with better adaptability.
4Measurement precision
If the focal length of the collimating lens is increased to improve resolution, then the measurement precision improves, but the device complexity and volume increase
Solution Approach 1:
Instead of using a single long-focal-length lens, the patent segments the optical system into multiple lens elements with shorter individual focal lengths arranged in a telephoto configuration. This achieves an effective long focal length (high angle resolution) while keeping the physical size of individual components manageable and the overall system more compact.
Solution Approach 2:
The patent uses a telephoto lens group configuration that extends the optical path length in one dimension while maintaining a compact form factor in other dimensions. By folding the light path and using a specific arrangement of convex and concave lenses, it achieves high angular resolution without proportionally increasing the device volume.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method achieves nano-radian order angle resolution and sub-microradian order accuracy, effectively resisting environmental interference and improving the autocollimator's ability to perform precise angle measurements in challenging conditions.
Implementation Method 1
A photoelectric autocollimator is based on the principle of optical autocollimation
Implementation Method 2
A beam emitted from the laser light source 1 is collimated by the convex lens 41 into a parallel beam which enters a reflecting surface of a measured object 5. The beam reflected from the reflecting surface of the measured object 5 converges via the convex lens 41
Implementation Method 3
the beam reflected from the reflecting surface of the measured object 5 converges via the convex lens 41, and the image sensor 3 collects spot information
Implementation Method 4
the image sensor 3 collects spot information. Angle information of the measured object 5 can be calculated by using the spot position information
Data Source
AI summary
The disclosure belongs to the technical field of precision test and measurement, and provides a two-dimensional photoelectric autocollimation method and device based on wavefront measurement and correction. According to the disclosure, a link of wavefront measurement and correction of a reference light path is added to a traditional autocollimator measuring method. By using wavefront distortion information of the reference light path in the instrument and driving a deformable mirror to compensate for phase distortion of a beam, the link realizes measurement and control on aberration of the optical system of the autocollimator and improves the imaging quality and spot positioning accuracy of the optical system, thereby improving the angle measurement accuracy of the autocollimator. At the same time, by introducing the link, the autocollimator has the ability to resist interference from the external environment, so that the resolution and stability of angle measurement of the autocollimator are further improved. The method makes the traditional autocollimator have a nano-radian order (5×10−9 rad, that is 0.001″) angle resolution and a sub-microradian order (10−7 rad, that is 0.02″) angle measurement accuracy. The disclosure has the technical advantage of realizing angle measurement with high resolution, high accuracy and high stability under the same conditions, and has the abilities to resist environmental disturbances and compensate for errors caused by the disturbances.