In Free Gyroscopic Stabilized Seekers, the Primary Minor has the multiple functions of a magnetic rotor, the primary rotating mass and the primary reflector for the optical train. The introduction of rare-earth magnet...
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ISBN:
(纸本)0819437387
In Free Gyroscopic Stabilized Seekers, the Primary Minor has the multiple functions of a magnetic rotor, the primary rotating mass and the primary reflector for the optical train. The introduction of rare-earth magnetic alloys to this class of seeker has provided increased flexibility in materials selection, opto-mechanical design and cost of manufacture. Along with superior magnetic properties, the rare-earth alloy Neodymium-Iron-Boron (NdFeB) comes with the undesirable properties of anisotropic CTE, high susceptibility to corrosion and manufacturing challenges. This paper discusses the opto-mechanical design, structural and optical modeling and analysis of a primary mirror assembly utilizing an NdFeB insert with centrifugal, linear acceleration and thermal loading as well as the optical test results, qualification testing of long-term figure stability and validation of the mechanical/magnetic/opticaldesign model.
Eyepieces are a part of visual optical systems. Because of their wide field of view and long eye-relief, it is difficult to further improve the existing eyepieces using all-refractive surfaces. Since diffractive eleme...
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ISBN:
(纸本)0819437387
Eyepieces are a part of visual optical systems. Because of their wide field of view and long eye-relief, it is difficult to further improve the existing eyepieces using all-refractive surfaces. Since diffractive elements demonstrate unique characteristics: negative dispersion and non-field curvature, the eyepiece design can be improved by using refractive-diffractive hybrid surfaces. In this paper, several design examples using refractive-diffractive hybrid surfaces to design moderate field of view (FOv) eyepieces were studied. Firstly, a design example using a diffractive surface to replace the negative piece in the cement doublet of a conventional Kellner type eyepiece is presented. Then a design example is given by employing two diffractive elements to replace the negative elements used in the conventional symmetrical eyepiece. For the above examples the eyepiece aberration correction techniques were also analyzed.
作者:
Huegele, vBNASA
George C Marshall Space Flight Ctr SOMTC Huntsville AL 35812 USA
A segmented array of mirrors was designed for a solar concentrator test stand at MSFC for firing solar thermal propulsion engines. The 144 mirrors each have a spherical surface to approximate a parabolic concentrator ...
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ISBN:
(纸本)0819437387
A segmented array of mirrors was designed for a solar concentrator test stand at MSFC for firing solar thermal propulsion engines. The 144 mirrors each have a spherical surface to approximate a parabolic concentrator when combined into the entire 17-foot diameter array. The mirror segments are aluminum hexagons that had the surface diamond turned and quartz coated. The array focuses sunlight reflected from a heliostat to a 4 inch diameter spot containing 8 kilowatts of power at the 15 foot focal point. The derivation of the surface figure for the respective mirror elements is shown. The alignment process of the array is discussed and test results of the system's performance are given.
Different wavefront description possibilities are today available to the opticaldesigner, usually in the form of polynomial fitting (Seidel, Zernike, monomials...). This kind of representations have the general drawb...
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ISBN:
(纸本)0819437387
Different wavefront description possibilities are today available to the opticaldesigner, usually in the form of polynomial fitting (Seidel, Zernike, monomials...). This kind of representations have the general drawback of being based merely in the geometrical shape of the wavefront considered, calculated as a distribution of optical path differences, without taking into account the energetic distribution present in the wavefront. As a consequence, optimization of optical systems is carried on based only on geometrical criterions, while applications tend to rely more on energetic properties of the wavefront (detection on CCD arrays or photodiodes, image formation, etc). In this paper we are proposing a new type of wavefront descriptor which includes its energetic distribution. The description is based on classical ray tracing procedures, in such a way that in each surface normal to the axis of the optical system, information on the position (z,y) and director cosines (w,v) of the ray are known, together with the energy flux assigned to each ray (F). This allows obtaining the energetic distribution in any plane in the optical system together with the classical wavefront description based in OPD calculations, allowing to obtain complementary wavefront information. This complementary wavefront description has been applied to some simple optical systems (a large diameter cemented achromatic doublet, and a Cooke's triplet) showing how even in these very simple case the differences in the energetic distribution and the geometrical shape at the exit pupil plane are relevant. Such a fact is demonstrated by least-squares fitting of the surfaces to a monomial representation, allowing the determination of the different primary aberration coefficients. Finally, differences in the geometrical PSF and the energetic distribution calculated are plotted to show they may achieve maximum deviations of up to 11% of the PSF value for the doublet, and 25% for the triplet. In addition, t
A strategy for optimizing both the on-axis and the off-axis performance of coherently (directly) coupled visual instruments is presented. The strategy draws on the recently published body of data regarding the influen...
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ISBN:
(纸本)0819437387
A strategy for optimizing both the on-axis and the off-axis performance of coherently (directly) coupled visual instruments is presented. The strategy draws on the recently published body of data regarding the influence of various individual Seidel aberration and aberration combinations on subjective contrast sensitivity and resolution tasks, as well as studies on the correlation between subjective image quality and objective instrumental figures of merit. An MTF-based metric allows both optimization and tolerancing to be performed in a coherent manner that is based on experimental results of the effects of aberrations.
In this paper, we present an opticaldesign of a near-infrared (at FeI 15648.5 Angstrom) birefringent filter system which is used to obtain the chromatic images of the sun and measure the solar magnetic field at the B...
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ISBN:
(纸本)0819437387
In this paper, we present an opticaldesign of a near-infrared (at FeI 15648.5 Angstrom) birefringent filter system which is used to obtain the chromatic images of the sun and measure the solar magnetic field at the Big Bear Solar Observatory (BBSO). This system consists of a prefilter, a liquid crystal analyzer, a wavelength-tunable birefringent filter and a Fabry-Perot Etalon. This system is expected to achieve a clean narrow pass band (1/8 Angstrom). It can also be tuned across the spectral line to obtain line profiles of two-dimensional fields of view. During the design of the tunable near-IR birefringent filter and the test of its components, we found the value of birefringence index mu (n(e) - n(o)) of calcite at spectral range near 15648.5 Angstrom is very different from the value in literature(1). Because the birefringence index is important for the design of birefringent optical components, the birefringence index of calcite and its thermal coefficient are measured. Some test results of the four pairs of calcite prate used in the birefringent filter are presented.
The Tropospheric Emission Spectrometer (TES) is one of the instruments slated to fly on the EOS Aura satellite in 2003. TES is a Fourier transform spectrometer designed to measure the concentration of various troposph...
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ISBN:
(纸本)0819437387
The Tropospheric Emission Spectrometer (TES) is one of the instruments slated to fly on the EOS Aura satellite in 2003. TES is a Fourier transform spectrometer designed to measure the concentration of various tropospheric chemical species. The Focal Plane Opto-Mechanical Assemblies (FPOMAs) are situated at the end of the TES optical train and are comprised of cryogenic telescopes, reimaging optics, and focal planes. We present the cryogenic opticaldesign of the FPOMA units and discuss optimization parameters and predicted performance. We present measured performance data and compare it with the predicted performance.
New panoramic and immersive digital imaging developments have generated increased interest in high performance fisheye camera lenses suitable for 35 mm single lens reflex (SLR) cameras. Special concerns for such appli...
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ISBN:
(纸本)0819437387
New panoramic and immersive digital imaging developments have generated increased interest in high performance fisheye camera lenses suitable for 35 mm single lens reflex (SLR) cameras. Special concerns for such applications are the uniformity of illumination and radial image mapping. Because two hemispherical images are digitally stitched together to form a complete 360-degree x 180-degree image, the performance of the lens at the 90 degree (preferably more than 90 degree) edge of the fisheye image is just as important as the center of the image. Lateral color, high order distortion (edge compression) and severe drop-off of illumination at the full field become obvious image defects and cause seams in the immersive image. Fisheye lens designs have widely varying relative illumination and distortion across the hemispherical field of view of the lens. After describing the contributing factors to relative illumination, we survey a collection of fisheye designs and compare their illumination performance, radial mapping and lateral color. A new method of measuring relative illumination and radial mapping in the laboratory is described and results on commercially available fish-eye lenses are presented.
Low-cost CCD-based cameras offer several cost and performance advantages for remote sensing applications. The optomechanical design of such cameras is inherently simple because zoom, gain and yaw corrections can be pe...
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ISBN:
(纸本)0819437387
Low-cost CCD-based cameras offer several cost and performance advantages for remote sensing applications. The optomechanical design of such cameras is inherently simple because zoom, gain and yaw corrections can be performed electronically, thereby, requiring no moving parts or mechanisms. This paper presents the optomechanical design and the results of structural and thermal analyses for a low-cost camera consisting of only three major parts: lens, electronics and camera housing. This camera uses a wide field of view lens with a fast f-number to acquire high-resolution images under various day and night time illumination scenarios. Passive athermal design of the lens maintains a high value of the MTF over a temperature range of 110 degreesC. Selection of the materials and adhesives used in this camera is dictated by a lifetime requirement of over 30 years under adverse environmental conditions. Structural and thermal modeling results confirm the survivability and performance of this camera under various shock, vibration and thermal loads.
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