Piezoelectric Actuator Mirror Shape Correction
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Solution Overview
Problem
Existing devices for correcting astigmatism and radius of curvature in telescope mirrors are heavy, unreliable, and not suitable for space applications due to limited mean time between failures and high costs, while maintaining image quality is crucial for advanced optical functions.
Innovation Solution
A device with a mechanical structure comprising controllable length elements and a parallelogram configuration, using piezoelectric devices or thermal actuators, to independently control astigmatism and radius of curvature, with flexible fixings to apply radial forces and modify the mirror's shape without altering its curvature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional active control devices are used to correct astigmatism and radius of curvature, then optical correction capability is achieved, but weight increases and reliability decreases
Solution Approach 1:
The mirror is divided into multiple segments that can be independently adjusted. Each segment has its own actuators positioned at specific locations (center, intermediate, and periphery) to apply localized forces. This segmentation allows the heavy traditional control device to be replaced with lighter, distributed actuators that achieve the same correction function through coordinated movement of mirror segments.
Solution Approach 2:
The patent replaces traditional mechanical control systems with piezoelectric actuators. These piezoelectric devices convert electrical signals directly into mechanical displacement, eliminating the need for heavy mechanical linkages, motors, and gear systems. The piezoelectric effect provides precise control with minimal weight, directly resolving the contradiction between reliability and weight.
2Reliability
If traditional active control devices are used to correct astigmatism and radius of curvature, then optical correction capability is achieved, but mean time between failures decreases
Solution Approach 1:
By segmenting the control system into independent actuators positioned at strategic locations, the patent reduces the complexity of any single control unit. Each piezoelectric actuator is a simple, solid-state device with no moving parts, eliminating mechanical failure points. The segmented approach distributes the control function across multiple simple units rather than requiring one complex control mechanism.
Solution Approach 2:
The substitution of piezoelectric actuators for traditional mechanical control systems eliminates gears, motors, and linkages that are prone to wear and failure. Piezoelectric devices are solid-state with no moving parts, dramatically increasing mean time between failures while reducing the overall mechanical complexity of the system.
3Weight of moving object
If device weight is reduced for space applications, then space compatibility improves, but correction precision may deteriorate
Solution Approach 1:
The patent applies local quality by positioning actuators at specific locations (center, intermediate, and periphery zones) rather than distributing them uniformly. Each actuator applies force to a specific region of the mirror, allowing localized correction of optical aberrations. This targeted approach maintains high correction precision while using fewer, lighter actuators compared to a uniform distribution scheme.
Solution Approach 2:
Piezoelectric actuators provide sub-micrometer precision in displacement control, enabling highly accurate mirror shape correction despite their lightweight construction. The direct conversion of electrical to mechanical displacement with no mechanical play or backlash ensures that weight reduction does not compromise correction precision.
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 solution provides a lightweight, reliable, and cost-effective method for correcting optical defects in telescope mirrors, ensuring precise image quality and compatibility with extreme space environments.
Implementation Method 1
said control means being piezoelectric devices
Implementation Method 2
based on thermal actuators
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The device has a control unit (4) controlling a length of a controllable length element e.g. beam (2), where the element is connected to an optical surface (1) e.g. telescope mirror, by ends in diametrically and diagonally zones opposite and near a periphery of the optical surface. A connection between the element and the optical surface has rigid fixations joining two flexible and fixation zones along degrees of freedom. The element is made of material e.g. cesic(RTM: ceramic matrix composite material), glass, ceramic material, metallic material or composite material. The controlling unit has a cell including seven branches alternatively made of aluminum and fiber glass.