QC 351 A7 no. 44 / The primary intent of this monograph is to furnish the multiband experimentalist with a convenient source of current information on aerial photo- graphic films, spectral filters, and optical -mechanical tolerances for multiband cameras. An account is given of the various types of aerial cameras emphasizing their advantages and disadvantages in multiband use. Some cameras specially assembled as multiband systems are described fully. Electro-optical and optical multiplexing techniques for multiband photography are discussed. Finally, some predictions are made concerning multiband cameras of the future. The text of this monograph was initially written for inclusion as three chapters in a "Manual of Multiband Photography" coauthored by Dr. R. N. Colwell (editor) and Dr. E. F. Yost. Because of the high cost of reproduction of the many color photographs in the other chapters, the number of copies of the first edition of the manual will be limited. This is the reason for the separate publication of this monograph. The author wishes to acknowledge with thanks the many useful discussions and data furnished by friends in government, industry, and university. In particular, he wishes to thank the Earth Resources Division at NASA Manned Spacecraft Center for their continued support of work on multiband cameras at the Optical Sciences Center.

QC 351 A7 no. 46 / Simple inverse filtering of each spectral component of a color picture can lead to serious misregistration of the restorations. This is a consequence of the nonlinearity of the photographic process, which distorts edges of objects in an unknown manner. To force three restorations that do register, we tack onto the usual term describing mean -square resemblance to the object scene the constraint of mutual resemblance among the three restorations themselves. This term is highly sensitive to phase errors (misregistrations) among its three members. The optimum three filters complying with this minimization problem are found. A simple case is examined, in order to judge the manner by which the restoring filters force a mean-square resemblance to the original object scene and, simultaneously, a mutual registration among the three restorations.

QC 351 A7 no. 47 / This second report on the analog image processing program describes some modifications made to the machine and the results of some recent experiments. The chief modifications are increasing the speed of operation, re- wiring the amplifier circuits, and introducing a new modulator. A playback intensity function generator has also been incorporated. Photographs are included to illustrate the results of an attempt to process an astronomical photograph, a simple pattern recognition experiment, and the removal of motion blur.

QC 351 A7 no. 51 / This report presents the author's basic findings on various optical systems that he studied and /or designed at the Jet Propulsion Laboratory, Pasadena, California, for the high -resolution telescope of NASA's Mariner '69 and '71 television experiments. This f/2.5 508-mm-efl system had a 2° full field. Application of Burch's plate diagram was found useful in describing the research. Design work was done using the Los Alamos Scientific Laboratory lens design program, which meant using an rms spot size radius as the design criterion. The JPL requirement was a 40% modulation transfer factor at 80 Qp /mm, taking into account diffraction effects. Particular emphasis is placed on presenting computed and actual performance of the "long" one-conic "Equi -Radii Baker" telescope, which was chosen to fly by Mars in the Mariner VI and VII spacecraft. This system had the best resolution and lightest weight of any system optimized by the author but was also the longest system. It consisted of an aspheric plate for the window plus two mirrors of equal radius, the primary being an oblate spheroid and the secondary a sphere. The aspheric plate had to have the proper sphericity to introduce enough axial color to balance the large amount of spherochromatism occurring over the required spectral bandwidth.

QC 351 A7 no. 52 / Multiband photography has been employed for several years as a tool for aerial reconnaissance. Recent experiments indicate a potential value in earth resources studies, particularly those utilizing an electro-optical image sensor. This report lists the imaging properties of an electro-optical multiband camera that uses one combined image tube /camera tube sensor to achieve high- quality imagery with maximum registration between separation images. A study was made to determine which camera tube would be the best choice for the earth resources program. The results of the study indicate the best choice is a standard vidicon with fiber optic faceplate coupled to an image intensifier with an extended red photocathode. This decision was based on lifetime, image quality, ruggedization, and cost criteria.

QC 351 A7 no. 55 / A y,Ȳ diagram analysis has been made of two -surface optical systems. The surfaces are spherical and are rotationally symmetric about the optical axis. When the systems are normalized and one of the conjugate planes is at infinity, unique relationships exist between the radii and separations of the optical systems and the y,Ȳ diagram parameters. The aberration coefficients are obtained in terms of the first-order constraints of the y,Ȳ diagram. The y,Ȳ diagram parameters of two-surface systems having zero third-order spherical aberration are represented by a one -parameter family of solutions. The pupil position may be obtained by eliminating zero third-order astigmatism. When the two two-surface systems are placed back to back, each system having zero third -order spherical aberration, a free parameter defines the relationship between the two systems.

QC 351 A7 no. 56 / The 13.7 -m Czerny -Turner spectrograph at the McMath Solar Telescope is evaluated with regard to polarization and image -forming properties. The ratio of the transmissivity of the spectrograph for incident light linear polarized parallel to the slit, to the transmissivity for light polarized perpendicular to the slit is determined as a function of wavelength. Values of this ratio range from 0.3 to 20. The diffraction grating is responsible. It is shown that spectrograph transmission as a function of polarization may cause large photometric and radiometric errors. This fact is not unique to this particular instrument. Two mechanisms appear to contribute to the polarizance of the grating. These are (1) the Rayleigh or Wood's anomalies, and (2) a vector wave interaction introduced because the groove dimension is nearly the same as the wavelength. Peak polarizance Xp occurs at the Wood's anomalies, and for X > groove depth it is found that the wavelength of peak polarizance Xp is given by λp = (0.7) d cos(B) where d is the ruling separation and O the grating angle. Photoelectric scans of the solar spectrum were made across several of the Wood's anomalies to obtain their profiles.

QC 351 A7 no. 58 / The papers presented in this document were given at a technical session in conjunc- tion with the dedication of the Optical Sciences Center on January 22, 1970. Session chairman was the Honorable Harry Davis, Deputy Under Secretary of the Air Force. Mr. Davis was an appropriate choice for the chairman, as he has been active in stimulating much of the current thought and effort in this area. The concept of synthesizing a large optical aperture from a collection of smaller, related apertures has appealed to optical physicists for a long time. The difficulties of manufacturing a large telescope or other optical system using a single massive blank for the primary objective are in themselves extreme. In the case of a large astronomical telescope, even though the primary image- forming element may be monolithic, it cannot be rigid to the tolerances required. As a result, most telescopes are active in the sense that the primary mirror is supported on a mount that adjusts to differing mechanical or thermal loads. The development of large space telescopes will lead ultimately to actively controlled mirrors in the adverse environment of any useful orbit. Under such conditions, it is possible to conceive of a synthetic aperture telescope consisting of a set of reflectors, mounted on an actively controlled mechanical system, that can respond to environmental changes. In this way, proper phasing of the optical elements can be achieved for significant exposure times. In fact, some of the phasing can be done optically in the region of the image plane, which is typically much smaller than the apertures themselves. In addition to the above passive systems, active systems using laser illumination with either spatial or temporal integration can be devised and are close to realization. In effect, these would be optical radar systems, with all of the advantages of coherent detection, along with the fineness of resolution available at optical wavelengths. The state of the art in the field has not reached the engineering stage. Indeed, at present we cannot speak even of a developmental stage. However, the time is fast approaching when synthetic aperture optical systems are going to be realized in practice. Atmospheric limitations imply that the first applications will occur in space, but certainly not before the techniques are well explored on the ground, perhaps in the far infrared region where the resolution limitation of the atmosphere is not so restrictive as in the visible range. Before this happens, technological developments in several areas are required. Needed are active control and phasing of the optics, post-processing of the sampled pictures, and an over-all concept for system design. Any interested person can likely add more areas of technology that would be stretched to attain the desired goal. This meeting was organized to permit discussion of the state of the art in this area and to encourage further work in the field. Appended to this set of papers is a bibliography on the subject of optical synthetic apertures, which was prepared by Mr. R. Brian Hooker, currently a graduate student at the Optical Sciences Center. The list should be useful as a starting point for anyone who wishes to delve deeper into the subject. -R. R. Shannon

QC 351 A7 no. 62 / Multiband photography has been used for several years as a tool for aerial reconnaissance. Recent experiments indicate a potential value in earth resources studies, particularly those utilizing an electro-optical image sensor. This report summarizes the test parameters and testing philosophy of several electro-optical devices. The results of camera tube testing indicate that vidicons similar to the RCA 4589 are suitable for a multiband electro-optical camera system. Results of image tube testing indicate that careful specifying of imaging performance is necessary, and results of coupled camera tube /image tube testing indicate that improvement is necessary for coupling the fiber optics. It is recommended that the vidicon be used at rather high dark current (~100 nA) and that dark current subtraction be employed for the flight program.

QC 351 A7 no. 63 / A Jones matrix operator is derived for a liquid crystal in the cholesteric phase for light incident normal to the molecular planes. We also derive a similar operator to include the effect of absorption. It is seen that, in general, the right and left circular polarizations are not the natural eigenstates.