An Unconventional Chopper For Infrared Applications

Stanley M. Reich; Henry L. Brill

doi:10.1117/12.955861

9 November 1977 An Unconventional Chopper For Infrared Applications

Stanley M. Reich, Henry L. Brill

Proceedings Volume 0124, Modern Utilization of Infrared Technology III; (1977) https://doi.org/10.1117/12.955861
Event: 21st Annual Technical Symposium, 1977, San Diego, United States

Abstract

This paper describes an unusual tuning fork chopper in the development of which several significant advances were made. The specific application was in an infrared radiation experimental package on a deep space (interplanetary) 'vehicle. However similar devices can be applied generally in other optical systems, wherever it is desired to modulate incoming radiation while sequentially directing the beam to two or more instruments. Radiation need not be in the infrared portion of the spectrum but can be any wavelength capable of being reflected by a mirror. The basic requirement for the infrared package was a device which could modulate the incoming radiation by chopping a direct path to one instrument and provide a reflected path of image quality to a second instrument. The tuning fork device described hereafter accomplishes this dual function. It is basically a tuning fork chopper which, in addition to the usual modulating function, also serves as a beam splitter. In place of the usual blackened vanes this chopper carries a pair of vanes which have a high quality mirror surface. Because the radiation level would often be very low it was essential that very precise control of the aperture be maintained and that heat input to the vanes be avoided. Also, reactive forces to the experiments' optical bench had to be minimized and the device's magnetic field shielded. The unit described herein is basically similar to Bulova's proprietary Type L40 tuning fork choppers with modifications to meet the optical requirements and operation in a deep space environment. It was made for Texas Instrument Corporation for incorporation in an infrared interferometer-spectrometer package in the Mariner space vehicle for the Jupiter/Saturn/Uranus mission. The paper is devoted primarily to the problems peculiar to the application and to the solutions which enabled the unit to meet the unusually rigorous demands of both the performance parameters and the environment.

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Stanley M. Reich and Henry L. Brill "An Unconventional Chopper For Infrared Applications", Proc. SPIE 0124, Modern Utilization of Infrared Technology III, (9 November 1977); https://doi.org/10.1117/12.955861

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KEYWORDS

Infrared radiation

Mirrors

Electronics

Infrared technology

Beryllium

Optical alignment

Optical benches

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