Collimator Scanning for Large Optical Instrument Wavefront Measurement
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Solution Overview
Problem
Existing methods for controlling and measuring the optical quality of large optical instruments, such as space telescopes, are either expensive due to the need for high-quality collimators or require complex opto-mechanical arrangements, making it difficult to ensure the optical performance of these instruments before launch.
Innovation Solution
An optical control bench with a collimator of smaller diameter than the instrument, integrated in a mobile support for translation, scans the entire pupil by moving to different positions, allowing for the reconstruction of the wavefront error map and modulation transfer function without the need for large collimators or complex arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a collimator with large pupil diameter is used to measure the optical quality of large optical instruments, then the measurement can be performed directly without scanning, but the manufacturing cost and complexity increase significantly
Solution Approach 1:
The patent divides the measurement process into multiple segments by using a collimator with smaller pupil diameter that scans across different zones of the instrument's pupil. Instead of requiring one large collimator to cover the entire pupil at once, the system uses multiple smaller measurement zones that are sequentially scanned, thereby reducing the manufacturing complexity and cost of the collimator while maintaining comprehensive measurement capability.
2Device complexity
If the instrument becomes its own collimator by placing an optical source at the focus, then no external collimator is needed, but complex opto-mechanical arrangements are required to add the optical source and separate beams
Solution Approach 1:
The patent introduces an external collimator as an intermediary device that simplifies the measurement setup. Instead of requiring the instrument itself to serve as the collimator (which would demand complex modifications to the instrument's structure), the external collimator performs the collimation function, allowing the instrument to be measured without complex opto-mechanical rearrangements. The collimator acts as a mediator between the light source and the instrument under test.
3Ease of manufacture
If a collimator with small pupil diameter is used, then the manufacturing cost decreases, but the measurement requires scanning the entire pupil which increases measurement time
Solution Approach 1:
The patent employs dynamic scanning motion to move the collimator across different positions corresponding to various zones of the instrument's pupil. This dynamic approach allows the small collimator to systematically cover the entire pupil area through controlled translation, enabling comprehensive measurement while maintaining the cost advantages of using a smaller, easier-to-manufacture collimator. The scanning mechanism transforms the limitation of small collimator size into an acceptable trade-off by automating the coverage process.
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
This solution enables comprehensive optical control of large instruments by reconstructing the wavefront error and modulation transfer function, ensuring high optical quality without the expense or complexity of traditional methods, while minimizing vibration issues and maintaining the advantages of large pupils.
Implementation Method 1
a collimator equipped with an emission source adapted to said instrument, the collimator and the instrument being arranged so that an image of said source is formed on the photo-detection surface of the housing
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention pertains generally to the field of optical control benches for large-size optical instruments (3). The control bench of the invention includes a collimator (4) having a pupil with a diameter lower than that of the instrument. The cost and the complexity of the control bench can thus be reduced. The collimator is mounted on a movement in translation means (44). For each position of the collimator, the method comprises measuring the wave surface WFEk of the sub-pupil SPk of the corresponding instrument at said position. Based on the different measures obtained, the method comprises deriving the global wave area of the instrument. The different measures and analysis are substantially based on phase-restitution and local wave-surface resetting algorithms.