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Title: Focus control system for stretched-membrane mirror module

Abstract

A focus control system dynamically sets and controls the focal length of a reflective membrane supported between a perimeter frame. A rear membrane is also supported between the perimeter frame rearward and spaced apart from a back side of the reflective membrane. The space between the membranes defines a plenum space into which a mass of gas at a first pressure is inserted. The pressure differential between the first pressure and an external pressure, such as the atmospheric pressure, causes the reflective membrane to assume a first curvature relative to a reference plane associated with the perimeter frame. This curvature defines the focal length of the reflective membrane. The focal length is dynamically controlled by changing the volume of the plenum space, thereby changing the first pressure. The system can be used to change or maintain the pressure differential and hence the front membrane curvature. The plenum volume is changed by pushing or pulling on a central section of the rear membrane using a suitable actuator. Sensing means continuously sense the location of the reflective membrane relative to the reference plane. This sensed position is compared to a reference position, and a resulting error signal, comprising the difference between themore » sensed position and reference position, drives the actuator in a direction to minimize the difference. A vent value compensates for temperature changes or leaks in the closed volume by allowing the pressure differential to be adjusted as required to center the working range of the actuator about the desired focal length.« less

Inventors:
 [1];  [2]
  1. Solana Beach, CA
  2. San Diego, CA
Issue Date:
Research Org.:
AT & T CORP
OSTI Identifier:
867825
Patent Number(s):
5016998
Assignee:
Science Applications International Corporation (San Diego, CA)
DOE Contract Number:  
AC04-76DP00789
Resource Type:
Patent
Country of Publication:
United States
Language:
English
Subject:
focus; control; stretched-membrane; mirror; module; dynamically; sets; controls; focal; length; reflective; membrane; supported; perimeter; frame; rear; rearward; spaced; apart; space; membranes; defines; plenum; mass; gas; pressure; inserted; differential; external; atmospheric; causes; assume; curvature; relative; reference; plane; associated; controlled; changing; volume; change; maintain; hence; front; changed; pushing; pulling; central; section; suitable; actuator; sensing; means; continuously; sense; location; sensed; position; compared; resulting; error; signal; comprising; difference; drives; direction; minimize; value; compensates; temperature; changes; leaks; closed; allowing; adjusted; required; center; range; desired; reference plane; temperature change; temperature changes; focal length; central section; spaced apart; pressure differential; atmospheric pressure; error signal; reference position; mirror module; sensing means; closed volume; perimeter frame; external pressure; focus control; /359/

Citation Formats

Butler, Barry L, and Beninga, Kelly J. Focus control system for stretched-membrane mirror module. United States: N. p., 1991. Web.
Butler, Barry L, & Beninga, Kelly J. Focus control system for stretched-membrane mirror module. United States.
Butler, Barry L, and Beninga, Kelly J. Tue . "Focus control system for stretched-membrane mirror module". United States. https://www.osti.gov/servlets/purl/867825.
@article{osti_867825,
title = {Focus control system for stretched-membrane mirror module},
author = {Butler, Barry L and Beninga, Kelly J},
abstractNote = {A focus control system dynamically sets and controls the focal length of a reflective membrane supported between a perimeter frame. A rear membrane is also supported between the perimeter frame rearward and spaced apart from a back side of the reflective membrane. The space between the membranes defines a plenum space into which a mass of gas at a first pressure is inserted. The pressure differential between the first pressure and an external pressure, such as the atmospheric pressure, causes the reflective membrane to assume a first curvature relative to a reference plane associated with the perimeter frame. This curvature defines the focal length of the reflective membrane. The focal length is dynamically controlled by changing the volume of the plenum space, thereby changing the first pressure. The system can be used to change or maintain the pressure differential and hence the front membrane curvature. The plenum volume is changed by pushing or pulling on a central section of the rear membrane using a suitable actuator. Sensing means continuously sense the location of the reflective membrane relative to the reference plane. This sensed position is compared to a reference position, and a resulting error signal, comprising the difference between the sensed position and reference position, drives the actuator in a direction to minimize the difference. A vent value compensates for temperature changes or leaks in the closed volume by allowing the pressure differential to be adjusted as required to center the working range of the actuator about the desired focal length.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1991},
month = {1}
}

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