Optically driven deformable mirrors may eventually supplant electrically driven deformable mirrors in some adaptive-optics and active-optics applications. Traditionally, the mirror facets in electrically driven deformable mirrors are actuated, variously, by means of piezoelectric, electrostrictive, microelectromechanical, liquid-crystal, or thermal devices. At least one such device must be dedicated to each facet, and there must be at least one wire carrying a control or drive signal to the device. If a deformable mirror comprises many (e.g., thousands) of facets, then wiring becomes a major problem for design, and the problem is compounded in cases of piezoelectric or other actuators for which high drive voltages are required. In contrast, in optically driven mirrors, the wiring problem is eliminated.

Figure 1. Light From a Laser Diode impinges on an absorber in a Golay cell, heating the gas in the cell. A mirror on the diaphragm is displaced by the resulting expansion of the gas.
The basic principle of actuation of an optically driven deformable mirror is to use a laser beam to actuate a material. For example, a laser beam can be used to heat a material to make the material thermally expand to displace a mirror facet. In an experiment to demonstrate this principle, the actuator was a Golay cell (see Figure 1) having a diameter of ≈6 mm and a length of ≈10 mm. The beam from a laser diode was aimed at an absorber in the cell, thereby heating the gas in the cell. A mirror mounted on a 12.5-μm-thick polyethylene terephthalate diaphragm at one end of the cell became displaced as the gas expanded against the diaphragm. In one representative pair of experiments at a laser beam power of 0.23 W, the beam was mechanically chopped at frequencies of 1 and 5 Hz. The mirror exhibited corresponding oscillating displacements having amplitudes of 373 and 83 μm, respectively.

Figure 2. This Experimental Optically Driven Deformable Mirror is essentially a side-by-side array of devices like the Golay-cell/mirror unit of Figure 1.
Figure 2 depicts a simple experimental deformable mirror comprising a 5×5 square array of Golay cells with square mirror facets mounted on their membranes. A typical practical deformable mirror would likely include a much larger array (e.g., 100×100). In the contemplated use of such an array, two computer-controlled single-axis mirrors would be used to raster-scan a laser beam across the array, and the raster scan would be synchronized with an amplitude modulation to control the amount of heat delivered to each cell and thereby to control the displacement of each facet.

This work was done by Hamid Hemmati and William Farr of Caltech for NASA’s Jet Propulsion Laboratory.

In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:

Innovative Technology Assets Management
JPL
Mail Stop 202-233
4800 Oak Grove Drive
Pasadena, CA 91109-8099
(818) 354-2240
E-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Refer to NPO-42724.

Topics:
Architecture Electrical systems Exteriors High voltage systems Lasers Mirrors Optics Photonics Sensors and actuators Wiring
This Brief includes a Technical Support Package (TSP).
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Optically Driven Deformable Mirrors

(reference NPO-42724) is currently available for download from the TSP library.

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Photonics Tech Briefs Magazine

This article first appeared in the October, 2006 issue of Photonics Tech Briefs Magazine (Vol. 30 No. 10).

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Overview

The document is a Technical Support Package from NASA's Jet Propulsion Laboratory (JPL) concerning "Optically Driven Deformable Mirrors," identified by NTR Number 42724. It is part of NASA Tech Briefs, which disseminate information on aerospace-related innovations with potential wider applications in technology, science, and commerce.

Optically driven deformable mirrors are advanced optical devices that can change their shape in response to light. This capability allows for precise control of light waves, which is crucial in various applications, including adaptive optics, astronomy, and imaging systems. The technology aims to enhance the performance of optical systems by correcting distortions in real-time, thereby improving image quality and resolution.

The document emphasizes the importance of this technology within the framework of NASA's Commercial Technology Program, which seeks to promote the commercialization of aerospace innovations. By making such technologies available, NASA aims to foster partnerships and collaborations that can lead to further advancements and applications in various fields.

Additionally, the Technical Support Package provides information on how to access further resources related to research and technology in this area through the NASA Scientific and Technical Information (STI) Program Office. The STI Program Office serves as a repository for a wide range of publications and technical documents, offering support to those interested in aerospace technologies.

The document also includes a disclaimer stating that the United States Government and its representatives do not assume liability for the use of the information contained within it, nor do they guarantee that such use will be free from privately owned rights. It clarifies that any mention of trade names or manufacturers is for identification purposes only and does not imply official endorsement by NASA.

In summary, this Technical Support Package serves as a comprehensive overview of the optically driven deformable mirrors technology, highlighting its significance, potential applications, and the resources available for further exploration in the field. It reflects NASA's commitment to advancing aerospace technology and facilitating its transition into commercial use.