SETI [ASTRO] Imaging The Universe With 3-D Holographic Gratings


Larry Klaes (lklaes@bbn.com)
Wed, 02 Jun 1999 14:38:31 -0400


>X-Authentication-Warning: brickbat12.mindspring.com: majordom set sender to owner-astro using -f >Date: Tue, 1 Jun 1999 14:37:41 GMT >From: Ron Baalke <BAALKE@kelvin.jpl.nasa.gov> >To: astro@lists.mindspring.com >Subject: [ASTRO] Imaging The Universe With 3-D Holographic Gratings >Sender: owner-astro@brickbat12.mindspring.com >Reply-To: Ron Baalke <BAALKE@kelvin.jpl.nasa.gov> > >National Optical Astronomy Observatory >Tucson, Arizona > >EMBARGOED FOR RELEASE: 9:20 a.m. CDT, May 31, 1999 > >RELEASE NO: NOAO 99-06 > >IMAGING THE UNIVERSE WITH 3-D HOLOGRAPHIC GRATINGS > >Dr. Samuel Barden, astronomer at the National Science Foundation's National >Optical Astronomy Observatories in Tucson, Arizona, has partnered with Mr. >Willis Colburn and Mr. James Arns at Kaiser Optical Systems, Inc. (KOSI), >Ann Arbor, Michigan for the development of large format spectroscopic >gratings using holographic technology for astronomical applications funded >by the National Science Foundation through the Advanced Technologies >and Instrumentation Program in the division of Astronomy. These new >technology gratings can provide information at multiple regions of the >spectrum simultaneously, with higher efficiency, less cost, and greater >durability than the conventional grating technology that astronomers >have relied on for over a hundred years. > >Holograms have become commonplace on credit cards and in Hollywood >special effects. KOSI has developed a manufacturing process to produce >high quality scientific gratings based on recent holographic technology >that has not previously been in wide use for gratings. The NOAO and KOSI >development work takes this existing technology to the next level in >developing devices to disperse light from astronomical objects with >performance superior to classical, surface ruled gratings. The efforts >to produce high quality, large format "Volume-Phase Holographic Gratings" >for the demanding astronomical applications support the development of >other grating applications for telecommunications, manufacturing process >control, and other areas utilizing this technology. > >Astronomical holographic gratings are made by exposing a gelatin material >to a laser light source, swelling the gelatin with water, and then rapidly >drying it in a bath of alcohol. Areas of gelatin collapse to a density that is >characteristic of the intensity of light they were exposed to, resulting in >a gelatin structure that is not uniform throughout. These differences in >density are responsible for the light diffracting properties of the grating. >The joint NOAO and KOSI work produces highly tuned gratings optimized >for astronomical applications. When properly sealed from exposure to any >moisture or humidity, the grating materials can have optimum performance >over at least 20 years. > >Future efforts will include upgrading the facilities at KOSI to make larger >format gratings. Classical surface gratings are limited to sizes of about >8 by 16 inches. VPH grating technology should be capable of producing >gratings as large as 15 by 30 inches and possibly up to 40 inches in size. > >The exciting potential of these gratings has already spawned numerous >spectrograph concepts being considered by several observatories world >wide. The National Optical Astronomy Observatories are exploring a >spectrograph concept which would utilize these gratings for the >simultaneous observation of thousands of objects over the full imaged >field of their 4-meter telescopes. The SOAR consortium, of which NOAO >is a member, is implementing VPH grating technology into its set of >spectrographs. The Anglo-Australian Observatory is currently designing >a spectrograph to replace its decades old spectrograph. The European >Southern Observatory has also recently acquired a VPH grating for >implementation into a spectrograph on the VLT. > >Image Caption: [http://www.noao.edu/outreach/press/images/9905.tif] > >Light from the burning candle falls on the Volume-Phase Holographic >Grating in this image taken with a 35-mm camera. The candlelight >is spread into its component colors. This particular grating actually >contains two gratings in a single element, something that is impossible >to do with classical gratings. Note that there are two spectra visible >in the image. A slight tilt between the two gratings allows the two >spectra to be imaged separately onto the detector of the spectrograph. >This technology allows for the simultaneous observation of different >wavelength regions at higher efficiency, less cost, and greater >durability than conventional grating technology. > >For more information, contact these astronomers at the National Optical >Astronomy Observatories, Tucson, Arizona: > >Suzanne H. Jacoby >NOAO Press Officer >(520) 318-8364 >email: sjacoby@noao.edu > >Dr. Samuel Barden >NOAO Scientist >(520) 318-8263 >email: sbarden@noao.edu > >EDITORS: High resolution versions of the images are available via the >internet at http://www.noao.edu/outreach/press/ > >The National Optical Astronomy Observatories is operated by the >Association of Universities for Research in Astronomy, Inc. under >cooperative agreement with the National Science Foundation. > >



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