Telescope Optical Alignment Using Internal Diffraction Wavefront Sensing
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Solution Overview
Problem
Existing telescopes face alignment drift due to temperature variations, gravity changes, wind buffeting, and acoustic vibrations, leading to degraded image quality over time, and current alignment methods are inefficient or require additional hardware that increases telescope length.
Innovation Solution
An optical alignment system using a diffraction pattern on an optical element within the telescope to measure wavefront errors with an internal light source, allowing continuous alignment and correction of optical elements without the need for external mirrors or doubling the telescope length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light source and metrology system are placed at the centre of curvature of the primary mirror, then alignment information about the primary mirror can be obtained, but the length of the telescope is doubled
Solution Approach 1:
The patent extracts the alignment measurement function from the traditional centre-of-curvature configuration and relocates it to the focal plane. By using a light source and wavefront sensor at the focal plane instead of at the centre of curvature, the system obtains primary mirror alignment information without requiring the extended path length, thus resolving the contradiction between measurement precision and telescope length.
Solution Approach 2:
The patent transitions from a one-dimensional alignment measurement approach (along the optical axis at centre of curvature) to a two-dimensional approach by utilizing the focal plane geometry. The wavefront sensor measures alignment information in the focal plane where light from the primary mirror converges, enabling compact measurement without extending the telescope length.
2Measurement precision
If a flat test mirror is placed ahead of the telescope to measure wavefront errors, then only telescope wavefront errors can be measured, but the telescope cannot be used to view distant objects while the mirror is in place
Solution Approach 1:
The patent implements self-service alignment measurement by using the telescope's own optical system to measure its own wavefront errors. The light source is positioned at the focal plane and the wavefront sensor detects errors in the returned light path, allowing the telescope to self-diagnose alignment issues without requiring external test mirrors that would block its observational function.
Solution Approach 2:
The patent makes the telescope's optical system multi-functional by enabling it to perform both observation and self-alignment measurement simultaneously. The focal plane location serves dual purposes: receiving light from distant objects for observation and housing the light source and wavefront sensor for alignment measurement, thus eliminating the need to choose between these functions.
3Device complexity
If passive techniques are used to deal with alignment variations, then the telescope structure can be simpler, but alignment drift over time cannot be continuously corrected
Solution Approach 1:
The patent implements feedback control for alignment stability by continuously measuring wavefront errors with the wavefront sensor and using this information to adjust the primary mirror's position or shape. This closed-loop feedback system compensates for alignment drift caused by temperature variations, gravity changes, and vibrations, maintaining reliable alignment without requiring overly complex passive stabilization structures.
Solution Approach 2:
The patent transitions from static passive alignment techniques to dynamic active alignment control. The system continuously monitors and adjusts the primary mirror's alignment state in real-time, enabling the telescope to adapt to changing environmental conditions and maintain optimal performance without relying solely on rigid, complex passive structural constraints.
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
Enables continuous and rapid correction of optical element positioning, facilitating lightweight structures, self-alignment after deployment, and maintaining high image quality by decoupling observation and alignment processes.
Implementation Method 1
A light source is able to send light into the optics of the telescope. One of the optical surfaces of the telescope is configured to diffract light from the light source
Data Source
AI summary
A telescope including an optical alignment system. The telescope has a light collecting aperture, an imaging region for an imaging sensor, and comprises a plurality of optical elements between the light collecting aperture and the imaging region. The optical alignment system comprises a diffraction pattern on a surface of one of the optical elements, a light source to illuminate the diffraction pattern, and a metrology system to receive diffracted light from the light source after diffraction by the diffraction pattern. The metrology system is configured to characterize a wavefront of the diffracted light for determining an optical alignment of the telescope.