Advanced Baffles: knife-edged diffuse-absorptive and dual reflective baffles

Optically black baffle surfaces are essential in determining the signal-to-noise level for many opticalsystems. Requirements for new, advanced optical systems indicate that new, advanced materials orimprovements in current industrially available materials are needed. Broadband optically black berylliumbaffle surfaces have been developed and performance of black beryllium knife-edged baffle vanesdemonstrated. In this paper an overview of the requirements for baffles, optical characteristics of thedeveloped optically black beryllium baffle surfaces, and the performance of black beryllium knife-edgedbaffle assembly will be discussed.1. INTRODUCTIONBaffles1.2.3 in optical systems are internal surfaces that control or suppress stray radiation, typically usinggeometrically designed vanes and surface morphology. Optical baffle components4.56 are essentialelements of many optical systems. Baffles perform a major role in determining the signal-to-noise level ofmany optical systems; and, thus, are important in increasing the pointing accuracy of the sensor. Allinternal surfaces in optical systems that require stray light management to achieve resolution are of primaryconcern in baffle design. While a few commercially available baffle materials meet optical requirments,current industrial baffle materials do not meet survivability and endurability needs; i.e, thermal,mechanical, and chemical stability requirements. The major problem is the generation of particles from thebaffle surfaces during threat exposure, movement, and operation which degrade the image quality.The objective of the Optics MODIL7 Advanced Baffle Program is to develop and validate the integration ofemerging advanced materials and enabling manufacturing technologies that can be used to produce light-weight, broadband optical baffle systems which are survivable, endurable, handleable, cleanable,scaleable, and affordable; to demonstrate the technology with industrial participation; and to transfer thetechnology with "hands-on" experience. Commercial vendors of Lambertian diffuse-absorptive and dualreflective baffle systems for SDIO sensor systems are targeted.2. RESULTS AND DISCUSSION2. 1 Types of BafflesThere are two types of baffles; i.e., baffle components which utilize diffuse-absorptive surfaces and thosethat employ reflective surfaces for stray light control. The diffuse-absorptive baffle materials which willbe discussed are black etched beryllium-on-beryllium (Be-on-Be), chemical vapor deposited (CVD) boroncarbide-on-silicon carbide (B4C-on-SiC), plasma sprayed (PS) boron-on-Be (B-on-Be), PS B4C-on-Be,and PS Be-on-Be. The reflective baffle system concept8 developed by N. Stavroudis, LockheedMissiles and Space Systems, is under investigation by the Optics MODIL. Producibility, lightweighting,and performance are important issues for dual reflective baffles.The diffuse-absorptive surfaces use microscopic surface features or porosity to absorb, scatter, or traplight. The surfaces are most effective as optically black baffles when the features are steep-sloped with anaspect ratio 3 to 10 times the wavelength of light, the size of the features are comparable to or slightly