Angular Field Of View Research Articles

Deviation from the Lambert-Beer Law in the Transmittance of a Light Beam Through Diffusing Media: Experimental Results

Abstract Attenuation measurements of an He-Ne laser beam in suspensions of polystyrene latex spheres are presented. Measurements were performed with a transmissometer having a receiver with a variable field of view (FOV) in a lenspinhole geometry. Attenuation measurements taken with different fields of view for any fixed optical depth, enabled us to separate the scattered received power P s and the beam-attenuated power P 0 from the total received power P. In this way the true value τ of the optical depth was obtained from P 0 and compared with the apparent optical depth τA obtained from P. Thus the error ∊ = (τ − τA)/τ due to the contribution of scattered received power in attenuation measurements was investigated. Many measurements were taken in order to see how τA and ∊ vary with the optical depth, with the size of the diffusing spheres and with geometric arrangement (radius and angular FOV of the receiver, distance between scattering cell and receiver).

The optics of comparative ophthalmoscopy

One factor peculiar to the practice of comparative ophthalmoscopy is the very large variation in ocular size of the animals examined, a factor which is ignored in current textbook treatments of the subject. We have computed values of lateral magnification, axial magnification, angular field of view and linear field of view for 19 species of terrestrial vertebrates. The dimensional value of a 1 diopter change in direct ophthalmoscopic focus was also determined. The anterior focal length of the eye in air and the vitreal refractive index were the intrinsic optical parameters of the animal's eye necessary for these calculations. Where these values were not available from the literature, the vitreal refractive index was assumed to be 1.336 and the anterior focal length was estimated as two-thirds of the axial length using a regression equation we derived from data in the literature. The angular field of view in ophthalmoscopy was shown to be invariant in the emmetropic eye and equal to the angular subtense of the ophthalmoscopic beam. The lateral field of view and retinal depth corresponding to a 1 diopter change in direct opthalmoscopic focus varied directly with the anterior focal length of the eye. The remaining parameters of lateral and axial magnification varied inversely with the anterior focal length of the animal's eyes. These findings provide a basis for evaluating the relative size and significance of ophthalmoscopically viewed features in terrestrial vertebrate eyes.

Design and fabrication of efficient diffraction transmission gratings on step-index optical waveguides

High-efficiency and low loss constant periodicity gratings have been fabricated and evaluated on single-mode planar optical wave guides. The most important parameters that will affect the lens performance are the coupling coefficient and the Q (or ρ) factor. The coupling coefficient has been found to be given by Kc = Δneff/(λ0/2). Investigation of the Δneff value has shown that for small groove heights larger Δneff can be obtained for CeO2 deposited grooves than for etched grooves. In grating structures where Q and ρ factors are high, the effect of the higher orders of diffraction is negligible, and there is a good agreement between the experimentally measured characteristics and the prediction from the coupled mode theory. However, minor variations in the fabrication processes (e.g., Δn ≃ 0.02) may cause the diffraction efficiency to vary as much as 15%, while the angular field of view does not seem to be affected by process variations.

Application of the conservation of etendue theorem for 2-D subdomains of the phase space in nonimaging concentrators

The conservation of etendue for general 2-D bundles of rays (not necessarily coplanar) is examined (a 2-D bundle of rays is that whose rays are distinguishable by giving each one two parameters). This is one of the integral invariants of Poincare and it is directly related to the Lagrange invariant. The application of this theorem to selected 2-D bundles of rays crossing an arbitrary cylindrical concentrator gives us a relationship between the maximum geometrical concentration of a cylindrical concentrator and the angular field of view which is more restrictive than the general one (i.e., the relationship is valid for an arbitrary concentrator) when the collector is surrounded by a refractive medium.

A perturbation and iterative perturbation analysis of linearly chirped grating lenses of medium Q in dielectric waveguides

A perturbation and iterative perturbation analysis of linearly chirped quasi-periodic structures of medium Q factor in planar dielectric waveguides has been formulated. This analysis can be used to calculate the diffraction efficiency and the angular field of view of a given linearly chirped grating structure, for a specific incident beam including the effect of higher orders of diffractions. The numerical example of a F = 10 , f = 10 m.m, \Lambda_{\min} = 2.06, \Lambda_{\max} = 4.25 and grating groove length = 15 μm is presented.

Optical Design For A Visual Locomotive Simulator

This article describes the optical system for the visual locomotive simulator at the Canadian National Transportation Training Centre, Gimli, Manitoba. The projection system incorporates an aspheric reflector which expands the angular field of view presented to it from the projection lens by a factor of approximately 20 before the image is focused onto a spherical screen. The picture presented to the student has a horizontal and vertical field of view of 63° and 26° respectively. The large Petzval curvature and astigmatism introduced by the aspheric mirror is compensated for in the design of the projection lens.

Diffusers in silicon-photodiode radiometers

The problems encountered when making radiometric measurements with silicon-photodiode radiometers not incorporating diffusers are discussed, with special attention given to the case where laser beams are involved. A diffuserless radiometer head design is presented which eliminates most of these problems. These problems can also be avoided by using a diffuser. A radiometer head incorporating a diffuser is described, and its properties are studied for three types of diffuser: flashed opal, type-2250 translucent Plexiglas, and a three-piece ground and etched quartz. Graphical data are given for the spatial uniformity, angular response variation, and spectral attenuation associated with radiometer heads incorporating these three types of diffuser. It is shown that, for a wide range of radiometric and photometric applications, the quartz diffuser is the most desirable, although its use results in a somewhat limited angular field of view.

Application of convergent beam electron microscopy in materials science

IntroductionWe have used a Philips EM400 electron microscope with a STEM pole- piece to carry out convergent beam electron microscopy on a wide variety of materials, including precipitates in stainless steels, metal/semiconductor contacts, metal oxide catalysts, environmental fibres, metastable phases in evaporated films, and transition metal chalcogenide layer compounds. Two features of this microscope make it particularly suitable for convergent beam work. These are its low hydrocarbon partial pressure which greatly reduces the carbon contamination of the specimen when working with a small probe (̴ 300 Ådiameter) and the very wide angular field of view in the diffraction plane (̴ 16°).Two-dimensional diffraction may be used to yield information about the projected crystal potential. In certain cases a simple relationship has been established between the form of zone axis patterns and the nature of the projected potential, Oneway of using this information is by making measurements of zone axis critical voltages and we have recently extended our measurements to a number of zone axis patterns with 6 mm symmetry having different sorts of projected potential.

Deep sea optical viewing systems: methodologies for their analyses and synthesis

Methodology is presented for the analysis and synthesis of three model deep sea submersible-mounted optical viewing systems. The radiation field of the illuminator is characterized by a phenomenological beam model. Several useful concepts are introduced: exposure field, exposure contrast field, irradiance field, signal-to-noise field, and blur. Certain key exposures and irradiances are calculated. Emphasis is placed on the specification of optimum angular field of view, optimum height off-bottom, and speed of the submersible as a function of the various optical system parameters.

Electrically Controlled Birefringence of Thin Nematic Films

This paper reports field-induced realignment of a nematic liquid crystal. A thin nematic film, which has a negative dielectric anisotropy, is initially homeotropic. Application of a threshold field parallel to the optic axis distorts the nematic ordering and increases the film's birefringence in certain light-propagation directions. Experimental results are given for threshold voltage, threshold width, optical contrast ratio, frequency response, angular field of view, electrical power consumption, and transient response. Light-valve applications are described.

Description of a Photoelectric Rotating Slit Elevation and Azimuth Sensor

The Photoelectric Rotating Slit Elevation and Azimuth Sensor (PERSEAS) measures the azimuth and elevation of the line of sight to a target reflecting or emitting radiation in the 0.4- tol.1-micro portion of the spectrum. Angular field of view is 360 degrees in azimuth and 30 degrees in elevation. Eight stationary lenses are used with rotating fiber-optics slits and silicon photodiode detectors to produce electrical pulses which are time related to target angular coordinates. Data rate is one line-of-sight measurement per 2.5 msec. Accuracy is better than 1 mrad.

Light Guide Radiation Pyrometry

A method of calculating and describing transmission characteristics of light guides is developed and applied to rods of synthetic sapphire. The total transmission is shown to be an inadequate measure of the extent to which a calibration curve relating relative signal to temperature is possible for a light guide radiation pyrometer. The angular field of view of synthetic sapphire rod is presented in terms of fractional emergent power per five degree angular increment. It is concluded that the transmission properties presented here, in combination with data for a single point, permit the simple, individual calibration of commercially available light guide radiation pyrometers.

A FAST AURORAL CAMERA

A movie camera is described which photographs an auroral display at a speed of one or more frames per second. The fast optical system and wide angular field of view are obtained with an f/0.71 objective and a spheroidal mirror. The camera has been found very useful in the study of auroral motions.

The Electro-Optic Effect in Uniaxial Crystals of the Dihydrogen Phosphate (XH_2PO_4) Type IV Angular Field of the Electro-Optic Shutter*

When voltage is applied to a basal section of uniaxial crystal of the type XH2PO4, the crystal becomes biaxial. Between crossed polarizers it can be considered, then, to act as a light valve. The angular field of view is limited by the natural retardation of the crystal. This paper discusses methods by which this natural retardation can be minimized or effectively canceled so that the retardation with no voltage is essentially zero over a large angular field. In the first method a basal section of uniaxial crystal of opposite sign is placed in series with the slab to be excited. Another technique uses two slabs of similar crystal with a 90-degree optical rotator placed between them. Both these techniques are treated theoretically and experimental measurements are given to show the resulting angular polarization pattern. This pattern is shown both for the electrically excited case and the unexcited case.

The image-distortion and other effects due to the glass-thicknesses in lens systems

This paper discusses the optical influence upon distortion of image, or departures from correct pictorial representation, caused by the considerable thicknesses of glass involved in the construction of high-class photographic lenses or projectors of large angular field of view. Specific instances of such influence, and the appropriate formulae for expressing the amount of such distortion, are given.