Showing papers in "Applied Optics in 1970"
TL;DR: It is shown that moiré contour patterns provide a useful and flexible means of contouring surfaces.
Abstract: For a number of years, observations have been made of contour-like patterns created by the moire interference of a grid with its shadow cast onto a surface. The conditions under which these patterns correspond to planar contours are derived, and systems to generate these contours are suggested. It is shown that moire contour patterns provide a useful and flexible means of contouring surfaces. Experimental results are presented.
499 citations
359 citations
TL;DR: The results reveal that a Nd: YAG rod under pumped light becomes a positive lens with two focal lengths, and the temperature dependent variation of the refractive index constitutes the major contribution of the thermal lensing.
Abstract: Theoretical and experimental results are reported on the thermal lensing effect caused by the radial thermal gradient present in optically pumped Nd:YAG laser rods. The presented theory is in agreement with the experimental observations. The results reveal that a Nd: YAG rod under pumped light becomes a positive lens with two focal lengths. The temperature dependent variation of the refractive index constitutes the major contribution of the thermal lensing. The stress dependent variation of the refractive index modifies the focal length about 20%. The effect of end-face curvature caused by an elongation of the rod is less than 6%.
305 citations
TL;DR: A technique to determine a real nonnegative function representing the transmittance of a synthesized hologram is described, which uses the positions of the samples in the synthesizer to record the phase information of a complex wavefront.
Abstract: A technique to determine a real nonnegative function representing the transmittance of a synthesized hologram is described. The technique uses the positions of the samples in the synthesized hologram to record the phase information of a complex wavefront. Synthesized holograms are displayed on a flying spot scanner and recorded on film. The transmittance of the synthesized hologram is quantized into 256 levels because of a hardware limitation of the scanner.
298 citations
TL;DR: This work reports here on the use of a phase mask which imparts a phase shift of 180 degrees to half the data spots chosen at random and shows that the intensity in the Fourier transform plane is now proportional to the intensity of the Fouriers of one single data spot.
Abstract: In a holographic page-oriented memory the information is stored in an array of holograms. It is advantageous to record the Fourier transform of the original data mask because the minimum space bandwidth is then required and the information about any one data bit is spread over the hologram plane. In the Fourier transform plane most of the light is concentrated in an array of bright “spikes” because the data mask consists of an array of equidistant data spots. Some means is needed to distribute the light more evenly. We report here on the use of a phase mask which imparts a phase shift of 180° to half the data spots chosen at random. An analysis shows that the intensity in the Fourier transform plane is now proportional to the intensity of the Fourier transform of one single data spot.
225 citations
TL;DR: The elements of the Mueller matrix for polydisperse systems of irregular, randomly oriented particles have been measured in absolute terms as a function of scattering angle for two wavelengths and compared to the matrix elements that were calculated for assemblies of spherical particles that fit the same particle size distribution function and have the same (real) refractive index.
Abstract: The elements of the Mueller matrix for polydisperse systems of irregular, randomly oriented particles have been measured in absolute terms as a function of scattering angle for two wavelengths. These results have been compared to the matrix elements that were calculated for assemblies of spherical particles that fit the same particle size distribution function and have the same (real) refractive index.
213 citations
TL;DR: A general equivalence relation is given, by means of which one can obtain the design parameters for a single-ended unstable resonator of the type usually employed in practical lasers from the calculated or tabulated values for an equivalent symmetric or double-ended stable resonator.
Abstract: The eigenvalues for all the significant low-order resonant modes of an unstable optical resonator with circular mirrors are computed using an eigenvalue method called the Prony method. A general equivalence relation is also given, by means of which one can obtain the design parameters for a single-ended unstable resonator of the type usually employed in practical lasers, from the calculated or tabulated values for an equivalent symmetric or double-ended unstable resonator.
203 citations
TL;DR: Cotton plants were grown hydroponically with controlled environment, growth chamber grown true leaves of cotton plants were tagged on the day they became macroscopically visible, and predictions from the generalized theory include a measure of the water, air, and plant pigments in a leaf.
Abstract: Cotton plants were grown hydroponically with controlled environment. Third, growth chamber grown true leaves of cotton plants were tagged on the day they became macroscopically visible. Beginning 3.0 days after tagging, five leaf harvests representing maturity dates were made at successive 2- or 3-day intervals. Measurements with a spectrophotometer made on the leaves showed that the largest increase in reflectance, about 5%, and decrease in transmittance, about 8%, occurred between average values for after-tagging-ages of 3.5 days and 8.0 days over the 0.75–1.35-μ wavelength interval. Between after-tagging-ages of 3.5 days and 8.0 days, leaves expanded approximately fivefold, numbers of intercellular spaces approximately doubled, and thicknesses increased 14%. The theory of diffuse reflectance and transmittance of a compact leaf of equivalent water thickness (EWT) specified by D is generalized to include also the noncompact leaf characterized by many intercellular air spaces, can be regarded as a pile of N compact layers separated by infinitesimal air spaces. The void area index (VAI) of a noncompact leaf is given by N − 1, where N is not necessarily an integer. Predictions from the generalized theory include a measure of the water, air, and plant pigments in a leaf. An effective dispersion curve associated with the leaf surfaces is also obtained. A derived parameter D/N largely determines the reflectance and transmittance of a typical leaf over the 1.40–2.50-μ spectral range. A cotton leaf is highly compact when it first unfolds. At this point D/N ~ 180 μ. This value is essentially the leaf thickness. Intercellular air spaces develop rapidly during the next few days, and D/N decreases in value to about 130 μ. Subsequently, the leaf cells increase in size with no substantial further increase in the number of intercellular air spaces. This final growth phase is characterized by a slight increase in D/N to a maximum value of about 140 μ. Maximum reflectance of the leaf corresponds to a minimum value of D/N. The parameter D/N is highly correlated with the amount of intercellular air spaces in a leaf.
164 citations
160 citations
IBM1
TL;DR: A method for evaluating characteristics of the scattered radiation emerging from a plane parallel atmosphere containing large spherical particles is described and some results are presented to show that this method can be used to obtain reliable numerical values in a reasonable amount of computer time.
Abstract: A method for evaluating characteristics of the scattered radiation emerging from a plane parallel atmosphere containing large spherical particles is described. In this method, the normalized phase function for scattering is represented as a Fourier series whose maximum required number of terms depends upon the zenith angles of the directions of incident and of scattered radiation. Some results are presented to show that this method can be used to obtain reliable numerical values in a reasonable amount of computer time.
159 citations
TL;DR: From diffraction theory, an expression is derived for the radius of a gaussian beam, in an output plane of a single lens, on-axis optical system, as a function of input waist radius, lens focal length, input waist to lens spacing, and lens to output plane spacing.
Abstract: From diffraction theory, an expression is derived for the radius of a gaussian beam, in an output plane of a single lens, on-axis optical system, as a function of input waist radius, lens focal length, input waist to lens spacing, and lens to output plane spacing. Several special cases are discussed and plots of the important cases are included. The choice of the plots, and their scaling, was made on the basis of providing useful information to those people involved with typical problems in laser scanning systems, such as the location and size of the focused spot. The derivation includes a discussion of truncation effects.
TL;DR: An iterative solution is developed for the temperature and absorbing gas profiles of an atmosphere from spectral and angular measurements of atmospheric radiance, novel in that there is no limiting assumption made about the analytical form of the profile imposed by the number of radiance observations available.
Abstract: An iterative solution is developed for the temperature and absorbing gas profiles of an atmosphere from spectral and angular measurements of atmospheric radiance. This iterative solution is novel in that there is no limiting assumption made about the analytical form of the profile imposed by the number of radiance observations available. The solution is demonstrated through the determination of temperature and water vapor profiles of the earth's atmosphere from Nimbus III and Nimbus IV Satellite InfraRed Spectrometer (SIRS) observations. The solutions are compared with conventional rawinsonde and rocket-sonde observations. The results indicate that this solution can be used effectively to specify the general meteorological characteristics of an atmosphere from satellite or ground-based radiometric observations.
TL;DR: A digital computer and automatic plotter have been used to produce a series of perspective views of a computer-stored three-dimensional object which is slightly rotated for each view to produce an extremely high quality hologram which can be viewed in high ambient light conditions.
Abstract: A digital computer and automatic plotter have been used to produce a series of perspective views of a computer-stored three-dimensional object which is slightly rotated for each view. All of these views are combined together optically to produce a final hologram which can be viewed in high ambient light conditions. The reconstructed image appears three dimensional since each eye looks through a different holographic strip corresponding to a different view of the three-dimensional object. The net result is a technique requiring only seconds of computer time and some possibly automated optical manipulations to produce extremely high quality holograms of computer-stored three-dimensional objects.
TL;DR: In an ordinary varifocal or zoom lens system one or more lenses are moved back and forth along the optical axis, but lateral movements can also cause a zoom effect.
Abstract: In an ordinary varifocal or zoom lens system one or more lenses are moved back and forth along the optical axis. But lateral movements can also cause a zoom effect. The refractive or diffractive elements to be moved are no longer rotationally symmetrical. The elements can be made out of transparent material or as a grating with curved lines or as a special version of a kinoform. The zoom systems with lateral motion are very compact.
TL;DR: In a far infrared molecular laser the traditional pierced output mirror has been replaced by an infrared interference filter, consisting of two metal mesh reflector grids, which allows convenient optimization of the coupling conditions of a laser for maximum power output.
Abstract: In a far infrared molecular laser the traditional pierced output mirror has been replaced by an infrared interference filter, consisting of two metal mesh reflector grids. By adjusting the spacing between the two parallel grids, the reflectance of the filter can be varied. Theory and experiment of this variable reflector are presented. It allows convenient optimization of the coupling conditions of a laser for maximum power output. In contrast to hole coupling, the interference filter provides uniform coupling over the entire cross section of the reflector. This reduces the diffraction losses and improves the angular distribution of the output beam. The variable reflector has also been used to determine the linear gain of the laser.
TL;DR: Results of digital image processing techniques developed at JPL have been applied to images from a wide range of disciplines and the system considerations involved in adequately and efficiently doing image processing are discussed briefly.
Abstract: The extreme flexibility of the digital method of image processing makes a wide variety of linear and nonlinear processes possible. The digital image processing techniques developed at JPL have been applied to images from a wide range of disciplines. Results of this processing for picture generation, intensity and geometric manipulation, spatial frequency operations, and image analysis are shown. The system considerations involved in adequately and efficiently doing image processing are discussed briefly.
TL;DR: It is shown that the effects of the variable characteristic of the resist can be alleviated by monitoring diffraction efficiency during development by reducing exposure times and increasing the signal-to-noise ratio of the image.
Abstract: A technique is described for recording holograms and forming diffraction gratings in Shipley AZ1350 photoresist using the 4579-A output from an argon laser. A pre-exposure technique is described that not only reduces exposure times but increases the signal-to-noise ratio of the image. It is also shown that the effects of the variable characteristic of the resist can be alleviated by monitoring diffraction efficiency during development.
TL;DR: The doppler frequency shift produced in the various diffraction orders of a rotating radial diffraction grating allows such a device to be used as an optical modulator.
Abstract: The doppler frequency shift produced in the various diffraction orders of a rotating radial diffraction grating allows such a device to be used as an optical modulator. The theory and performance of such devices is presented.
TL;DR: No one refractive index distribution can be "ideal" for both meridional and skew rays, and the optimal index distribution varies with the ratio of rod length to radius and the relative aperture and is intermediate between the helically ideal and the meridionally ideal distributions.
Abstract: Cylindrical transparent media whose refractive index decreases with increasing cylinder radius have been investigated in connection with coherent light propagation in gas waveguides. Recently, graded index glass rods (trade named SELFOC rods) have been used as imaging devices. We report here on a geometrical optical study of graded index systems used for relaying images at unit magnification. We have found that two index distributions previously studied result in large image aberrations when the presence of skew rays is taken into account. We have derived an index distribution which is “ideal” for helical skew rays. Using ray tracing methods we have examined image aberrations for various index distributions and for various rod geometries. We find that (1) no one refractive index distribution can be “ideal” for both meridional and skew rays, (2) image resolution is generally low, reaching about 1000 spots per field, and (3) the optimal index distribution varies with the ratio of rod length to radius and the relative aperture and is intermediate between the helically ideal and the meridionally ideal distributions.
TL;DR: The velocity of gas flow has been remotely measured using a technique which involves the coherent detection of scattered laser radiation from small particles suspended in the fluid utilizing the doppler effect, and measurements of wind velocity have shown the considerable promise of the atmospheric system.
Abstract: The velocity of gas flow has been remotely measured using a technique which involves the coherent detection of scattered laser radiation from small particles suspended in the fluid utilizing the doppler effect. Suitable instrumentation for the study of wind tunnel type and atmospheric flows are described. Mainly for reasons of spatial resolution, a function of the laser wavelength, the wind tunnel system utilizes an argon laser operating at 0.5 micro. The relaxed spatial resolution requirement of atmospheric applications allows the use of a carbon dioxide laser, which has superior performance at a wavelength of 10.6 micro, a deduction made from signal-to-noise ratio considerations. Theoretical design considerations are given which consider Mie scattering predictions, two-phase flow effects, photomixing fundamentals, laser selection, spatial resolution, and spectral broadening effects. Preliminary experimental investigations using the instrumentation are detailed. The velocity profile of the flow field generated by a 1.27-cm diam subsonic jet was investigated, and the result compared favorably with a hot wire investigation conducted in the same jet. Measurements of wind velocity at a range of 50 m have also shown the considerable promise of the atmospheric system.
TL;DR: Study of a design for a large infrared telescope, consisting of six independent optical systems, shows that it is possible to control the optical path differences and phases such that aperture synthesis can be achieved.
Abstract: Study of a design for a large infrared telescope, consisting of six independent optical systems shows that it is possible to control the optical path differences and phases such that aperture synthesis can be achieved. A thin compensating prism in each optical path can compensate simultaneously the path errors for all objects in the field of view of the telescope. Design parameters for a 5.6-m system are given.
TL;DR: Experimental verification of the application of the integrating sphere or cavity to the measurement of the absorption coefficient (cm(-1)) of a material introduced into the cavity is described showing agreement with direct transmittance measurements to within +/-10%.
Abstract: This paper describes the application of the integrating sphere or cavity to the measurement of the absorption coefficient (cm−1) of a material introduced into the cavity. The absorption coefficient is determined by measuring the decrease in the radiation density within the integrating cavity caused by insertion of the sample. This method has the virtue of being independent of the scattering within the material sample, the reflectivity of the material surface, and the geometry of the sample. The method is particularly attractive for materials with small absorption coefficients. Experimental verification of the method is described showing agreement with direct transmittance measurements to within ±10%.
TL;DR: A remote sensing facility consisting of lidar and acoustic echo-sounding instruments probing the same volume of the atmosphere can measure many of the meteorologically significant parameters necessary to increase the understanding of the structure and dynamics of the clear lower atmosphere, and provide the spatial and temporal density of measurements necessary for weather forecasting.
Abstract: The considerable utility of ultrasensitive microwave radar in atmospheric studies can now be augmented by lidar and acoustic echo-sounding techniques. The current and potential capabilities, and limitations, of these methods of remote atmospheric probing are discussed and the techniques are compared. From this analysis the conclusion emerges that a remote sensing facility consisting of these instruments probing the same volume of the atmosphere can measure many of the meteorologically significant parameters necessary to increase our understanding of the structure and dynamics of the clear lower atmosphere, and provide the spatial and temporal density of measurements necessary for weather forecasting.
TL;DR: The experimental results of the model demonstrated that thermoplastic holograms can be organized into an array on a single glass plate with adequate thermal isolation, and the number of recording-erasure cycles of a thermoplastics hologram can be well over 100.
Abstract: A method of using a thermoplastic hologram array for a write–read–erase in situ optical memory is proposed. A model of the proposed memory consisting of an array of 3 × 3 holograms was constructed. The experimental results of the model demonstrated that (1) thermoplastic holograms can be organized into an array on a single glass plate with adequate thermal isolation, (2) the number of recording–erasure cycles of a thermoplastic hologram can be well over 100, and (3) because of the absence of Bragg diffraction from thermoplastic holograms, the input and the output planes of the memory can be conveniently separated without any imaging lens and mechanical movement. Photographs of some images obtained from one hologram of the model array are shown.
TL;DR: The complex interactions of quality of sources with hue, value, and chroma of object and background colors on aesthetic responses to colors help to account for the conflicting statements often found in the literature regarding color harmony.
Abstract: Effects of spectral energy distributions of sources and colors of backgrounds on the pleasantness of object colors were determined by having 5 men and 5 women rate 125 object colors on 25 colored backgrounds in 5 sources of illumination. In addition, foods and complexions were rated in the same sources. All main effects were found to be highly significant statistically. While lightness and chromatic contrasts of object and background were more important than quality of illuminants, the latter were very important in the case of some object and background color combinations. Differences between the sexes were highly significant in that men tended to prefer cool source, object, and background colors, women the warm colors. The best colors for backgrounds had either low chroma and high reflectance (the pastel colors), or low chroma and low reflectance. The most important single factor determining the pleasantness of color combinations was lightness contrast. Hue and chroma contrasts, while of some importance, were not as decisive as lightness contrast. Some closely related color families may be substituted for each other, e.g., 5 and 10R or 5 and 10G, while others may not be, e.g, 5 and 10GY. The complex interactions of quality of sources with hue, value, and chroma of object and background colors on aesthetic responses to colors help to account for the conflicting statements often found in the literature regarding color harmony. In spite of the complexities of the problem, some generalizations regarding color harmony were found valid and others were shown to be in need of further investigation. This study was based on 156,250 individual ratings of object colors.
TL;DR: A new interferometric device for measuring small angles or rotations with high accuracy is described, which works by counting fringes formed by the rotation of a flat-parallel plate of glass illuminated with a collimated beam from a gas laser.
Abstract: A new interferometric device for measuring small angles or rotations with high accuracy is described. This instrument works by counting fringes formed by the rotation of a flat-parallel plate of glass illuminated with a collimated beam from a gas laser. Some possible applications are given.
TL;DR: A theory of light relations in plantCanopies is presented which has potential applications in remote sensing and photosynthetic modeling of plant canopies and is compared with field measurements of light reflection and transmission in a corn crop.
Abstract: A theory of light relations in plant canopies is presented which has potential applications in remote sensing and photosynthetic modeling of plant canopies. Predictions of the model are compared with field measurements of light reflection and transmission in a corn crop. Both reflection at the top of the canopy and transmission at the bottom are predicted within 1% of the measured values. Profiles connecting these upper and lower limits are equally well approximated. Variations in the predictions with altitude angle of the sun are confirmed by the observation of several investigators.
TL;DR: Two cavity-type radiometers have been developed, based on first principles, having the capability of measuring an irradiance with an indicated error 0.3%, which indicates the degree of confidence that can be expected in measurements made with blackbody cavity radiometers.
Abstract: Two cavity-type radiometers have been developed, based on first principles, having the capability of measuring an irradiance with an indicated error 0.3%. The prerequisites for this accuracy are a measured aperture area, a measurement of electric voltages, and an effective absorptance of its blackbody cavity from 0.998 to 0.999 throughout the uv, visible, and ir spectral ranges. The first cavity-type radiometer is designed to operate only in a vacuum of <10−5 Torr and to measure intensities from 10 mW cm−1 to 300 mW cm−2. By using this radiometer in an evacuated cold chamber, an experimental determination of the Stefan-Boltzmann constant is obtained at a value that differs from the theoretical value by 0.3%, which indicates the degree of confidence that can be expected in measurements made with blackbody cavity radiometers. The second type of radiometer is designed to operate in either air or vacuum. Although its aperture opening is windowless, it is unaffected by wind. The range of intensities accurately measurable is from about 10 mW cm−2 to 800 mW cm−2; the indicated accuracy is also 0.3%.
TL;DR: The design of the instrument including the optical layout, the phase locked loop operation of the Michelson motor, and the functioning of the reference interferometer are discussed and the methods of data reduction and in-flight calibration are demonstrated on sample spectra recorded while in orbit around the earth.
Abstract: Michelson IR interferometer spectrometer /IRIS/ design calibration and performance onboard Nimbus 3 satellite, demonstrating data reduction and inflight calibration
TL;DR: The classical version of the Fresnel rhomb can be optimized to improve its performance, and several of the more recent rhomb designs have excellent characteristics.
Abstract: The most achromatic quarterwave plates appear to be rhomb-type devices. General relations are given for calculating the phase retardation of these devices and are used to determine the variation of the phase retardation with wavelength and with acceptance angle for different rhomb designs. Length-to-aperture ratio, beam deviation, surface coatings, effect of strain birefringence, and other parameters are also considered. The classical version of the Fresnel rhomb can be optimized to improve its performance, and several of the more recent rhomb designs have excellent characteristics. The choice of which type of rhomb to use depends on the requirements of the particular optical system.