Showing papers on "Transmittance published in 1975"

Modulation contrast microscope.

Abstract: A new microscope imaging system, modulation contrast, has been devised that reveals phase gradients; the image intensity is proportional to the first derivative of the optical density in the object. The modulator, a special filter, is placed in the Fourier plane, a plane conjugate with a slit aperture. The image of the slit aperture is registered within a gray region of the modulator; on one side of the gray region is a region of low transmittance and on the other side, a region of maximum transmittance. The modulator processes opposite gradients to produce opposite intensities, creating an optical shadowing effect. The dark region may be outside the optical system when the gray region is offset to the edge of the Fourier plane, to achieve maximum resolution. Modulation contrast is directional and capable of optical sectioning, revealing details without obscuring effects of structures above and below the plane of focus. The imaging theory of microscope optics has been extended to include effects of phase gradients. Phase gradients distribute the zero order across the Fourier plane. Intensity of the gradient's image is controlled by the zero order of the gradient diffraction pattern.

Ripple-free dichroic mirrors

Abstract: A dichroic mirror is made up of alternating layers of a material having a high index of refraction and a material having a low index of refraction arranged in a stack on one surface of a substrate. The dichroic mirror is effective to separate light in the visible spectrum range, incident thereupon, into two components, one of which is transmitted and the other of which is reflected. Each of the first, second and last layers in the stack, counting outwardly from the substrate, is controlled to an optical thickness deviated from an odd number of quarter-wavelengths of a design wavelength in air, to effect a uniform distribution of transmittance coefficients over the transmitted components.

Coated optical guides for spectrophotometry of chemical reactions

Abstract: A NEED exists for a method of detecting small amounts of chemicals in air and other gases, and in solutions, simply, and with a high degree of sensitivity. We have developed a new technique based on the concept of using waveguide phenomena in combination with chemical reactions. This technique is applicable to a wide variety of chemical reactions, including biochemical systems, provided that they cause a change in light transmittance by virtue of a change in colour, refractive index, or light scattering. Both real-time and cumulative measurements are possible.

Hot‐Working of Aluminum Oxide: II, Optical Properties

Abstract: Polycrystalline Al2O3 fabricated into plates or shapes by hot-working techniques exhibits high in-line transmittance from 0.4 to 5.5 μm. Examination of the product by an inverse pole figure technique demonstrated a strong {0001} texture normal to the pressing direction for both equiaxed and textured microstructures. The crystallographic texture was attributed to the dominance of basal slip in deformation. A comparison of transmissivity in the 2 principal directions of a forged plate strongly suggested that a reduction of birefringence resulting from the crystallographic texture was partially responsible for the high transmissivity. The absorption coefficient at 4.5 μm was 0.15 mm-1, ∼ that for sintered Al2O3 and 5 times that for sapphire

Detector for deep well logging

Abstract: A substantial improvement in the useful life and efficiency of a deep-well scintillation detector is achieved by a unique construction wherein the steel cylinder enclosing the sodium iodide scintillation crystal is provided with a tapered recess to receive a glass window which has a high transmittance at the critical wavelength and, for glass, a high coefficient of thermal expansion. A special high-temperature epoxy adhesive composition is employed to form a relatively thick sealing annulus, which keeps the glass window in the tapered recess and compensates for the differences in coefficients of expansion between the container and glass so as to maintain a hermetic seal as the unit is subjected to a wide range of temperatures.

Monopulse optical receiver system

Abstract: A monopulse optical receiving system is comprised of a plurality of optical sensors for receiving an incident light pulse at angles of incidence within a field of view, and providing in response thereto an output voltage signal whose magnitude is a function of the incident angle, at least two of the sensors being relatively disposed so that a portion of the field of view of one of them overlaps with a portion of the field of view of another one of them to provide an overlapping field of view within which the two sensors provide complementary transmittance gradients, the two sensors further providing mutually complementary voltage signals in response to light incidence within the overlapping field of view, the system further comprising a processing unit which calculates both an immediate coarse angle value for the incident light pulse and a fine angle describing the precise incident angle relative to the coarse angle value.

Spectrosorptance measuring system and method

Abstract: Apparatus and method for measuring the absolute absorptance of a relatively thin sample displaying both reflecting and transmitting characteristics. An integrating sphere is provided, and monochromatic reference and sample beams are projected into the sphere from a pair of angularly-spaced ports. Detector means are positioned at the sphere to receive illumination from the internal sphere wall, including the illumination arising from the first reflectance from that portion of the sphere directly illuminated by the sample and reference beams. The reference and sample electrical signals proceeding from the detector are equalized over the wavelength range of the instrument to establish a relatively flat baseline with the sample withdrawn from the sample beam. The sample is then repositioned within the sample beam. By virtue of the position of the detector and the thinness of the sample, the detector views the illumination of the sphere wall, but substantially excludes the first reflectance and scattered energy from the sample. The light falling on the detector due to illumination of the sphere via the sample is compared with the light falling on the detector due to illumination of the sphere by the reference beam, the ratio between the two providing a direct measure of the quantity of incident sample beam energy transmitted and reflected by said sample. By subtracting the thus determined reflectance and transmittance of the sample from unity, the absorptance of the sample may be directly indicated.

An integrated optical TE-TM mode splitter

Abstract: A hybrid technology developed for the deposition in planar waveguides of a multilayer which controls the guided optical power by interference has been tested using a TE-TM mode splitter as an example. The preparation of waveguides which exhibit good edge properties, the deposition of the multilayer and the mutual alignment of the waveguides by better than λ/5 are described. The ratio of the transmitted TE power to the reflected TM power has been measured to be 0.9±0.1, which agrees well with the 1.0 yielded by theory. Distortion due to mode conversion, TE reflectance and TM transmittance is of the order of 1%.

Methods of calculating atmospheric transmittance and radiance in the infrared

Abstract: Radiation from remotely sensed objects in the earth's environment is attenuated in its passage through the atmosphere. In the infrared region of the spectrum, this is caused, for clear-sky conditions, mainly through absorption by atmospheric molecular species, i.e., the atmospheric gases. Molecular absorption is characterized by a highly variable, more-or-less random, frequency dependence which is difficult, if not impossible, to describe analytically in detail. On the other hand, most experimental work requiring an understanding of atmospheric attenuative phenomena is accomplished with instrumental spectral resolutions that are coarse enough to smooth out much of the spectral detail in molecular line structure. Therefore, methods are described for calculating atmospheric transmittance and radiance to correspond to spectral resolutions of those instruments used in remote sensing. These methods involve either numerical integration of the exact line structure over the desired spectral interval, or the use of band models derived from artificially created line structure. Limitations of these calculations are discussed in the light of factors such as the fidelity of model atmospheres used to simulate real ones and the utility of different routines regarding computer time and accuracy. A short section covers the effect of scattering.

Light Transmittance and RF Shielding Effectiveness of a Gold Film on a Glass Substrate

Abstract: Light transmittance and the Rf shielding effectiveness of a gold film on a glass substrate is investigated. The dependence of the transmittance of visible light upon the thickness or surface resistance of a gold film on a glass substrate is determined numerically by the optical properties of the gold film and glass substrate. The Rf shielding effectiveness produced in the far field over the frequency range of 100 MHz to 30 GHz by the gold film is calculated and compared with experimental data. An optimum condition is established between the light transmittance and the shielding effectiveness. The results are applicable to any transparent glass coated with any thin metallic film.

Liquid crystal glasses

Abstract: PURPOSE: A glasses is provided in which a photoelectric element is connected with liquid crystal and a rate of light transmittance of lens is automatically changed in response to a brightness of outside light, and further when the glasses is removed from the body, a power source switch is automatically turned off. COPYRIGHT: (C)1976,JPO&Japio

Transmittance of air/SiO/SUB 2//polysilicon/SiO/SUB 2//Si structures

Abstract: Polycrystalline silicon films are presently used as the semitransparent gate electrodes in front-illuminated charge-coupled device (CCD) and charge-injection device (CID) image sensors. The transmittance of air/SiO/SUB 2//polysilicon/SiO/SUB 2//Si structures is calculated in spectral region between 0.4 and 1.0 /spl mu/. A proper choice of the thicknesses of the oxide films can substantially increase the transmittance over a narrow wavelength band or over the entire wavelength region of interest.

Effect of Collision Narrowing on Atmospheric Transmittance

Abstract: The effect of collision narrowing on inhomogeneous, long-path atmospheric transmittance is discussed. The different temperature and pressure dependence of the collision narrowing and the collision broadening contributions to the absorption line shape can result in a significant change in calculated values of both the absolute and relative transmitted intensity. Illustrative calculations are presented for a narrow-band source that is resonant with selected absorption lines of CO2 and is transmitted along a variety of atmospheric paths.

Optical coating with selectable transmittance characteristics and method of making the same

Abstract: A layer of zinc oxide disposed on the surface of a substrate in thicknesses of between 500 and 10,000 Angstroms is characterized by a sharp absorption edge to substantially absorb selected wavelengths of radiation incident thereon while transmitting other selected wavelengths. The wavelength of the absorption edge is selectable as a function of temperature. A method of depositing the zinc oxide layer is also described.

Michelson interferometer with frustrated-total-internal-reflection beam splitter

Abstract: An efficient beam splitter for a Michelson interferometer can be made from a pair of prisms, using the process of frustrated total internal reflection. Although the phases and irradiances of the beams reflected and transmitted by the beam splitter depend on the polarization, the phase difference between the two interferometer beams vanishes for all polarizations and the transmittance can be made polarization insensitive by suitable design. The interferometer transmits radiant power within a wavelength band approximately two octaves wide, and rejects all other radiant power. The design, laboratory tests, and astronomical applications of an interferometer for the millimeter and submillimeter regions are discussed. An observation of the day-sky spectrum is presented.

Spectral and directional radiation characteristics of thin-film coated isothermal semitransparent plates

Abstract: An analysis is presented for prediction the effective spectral, directional radiation characteristics of an isothermal, semitransparent sheet surrounded on both sides by massive dielectrics. This sheet can be coated on one or both sides with one or more optically thin films. Such coated sheets are considered for their applicability as selective cover plates for solar collectors. Extensive computations have been performed to determine what thin film optical properties and film configurations yield the desired selectivity, i.e., high solar transmittance and at the same time high infrared reflectance. Sample results are presented to illustrate the effects of thin film real and imaginary indices of refraction on the spectral reflectance and transmittance of thin film coated glass sheets. Also, directional and polarization effects are considered for selected thin film-plate systems. Some potential candidate materials have been identified and spectral transmittances and reflectances of isothermal plates coated with thin films of these materials have been predicted.

Light Transmittance and Microwave Attenuation of a Gold-Film Coating on a Plastic Substrate

Abstract: Light transmittance and microwave attenuation of a gold-film coating on a plastic substrate is investigated. The dependence of the transmittance of visible light upon the thickness or resistivity of a gold-film coating on a plastic substrate is analyzed numerically. The microwave attenuation produced in the far field over the frequency range of 100 MHz-30 GHz by the gold film is calculated and compared with experimental data. An optimum condition is established between the light transmittance and the microwave attenuation. The results are applicable to any transparent glass coated with any thin metallic film.

High purity silica reflective heat shield development

Abstract: Measurements were made of reflectance in the vacuum ultraviolet down to 0.15 micron. Scattering coefficients (S) and absorption coefficients (K) were also measured. These coefficients express the optical properties and are used directly in a thermodynamic analysis for sizing a heat shield. The effect of the thin silica melt layer formed during entry was also studied from the standpoint of trapped radiant energy.

Optical properties of thin Au−Cr films and their application to solar energy conversion

Abstract: Opaque Au and Au−Cr films were produced by rf triode sputtering onto a glass substrate at 150°C. Cosputtering of Au and Cr films has extended the solubility limits of Cr in Au from 19 at.% Cr to 48 at.% Cr. Electron microscopy showed polycrystallinity in the entire solubility range and electron microprobe analysis confirmed compositional uniformity of films. Reflectance measurements were made in the range 0.3−15 μ. Reflectance data were analyzed by the Kramers−Kronig method to obtain the optical constants n, k, e1, and e2. Good agreement is shown with the previous single crystal data on Au−Cr (up to 19 at.% Cr). The reflectance data are used to calculate α/e ratio which is applied to the solar energy collector surfaces. Reflectance and transmittance data for very thin Au and Au−Cr films (100−400 A) are used to calculate the figures of merit for the heat mirror type solar−thermal energy collector design.

Light Transmittance and Microwave Attenuation of a Gold-Film Coating on a Plastic Substrate (Short Papers)

Abstract: Light transmittance and microwave attenuation of a gold-film coating on a plastic substrate is investigated. The dependence of the transmittance of visible light upon the thickness or resistivity of a gold-film coating on a plastic substrate is analyzed numerically. The microwave attenuation produced in the far field over the frequency range of 100 MHz-30 GHz by the gold film is calculated and compared with experimental data. An optimum condition is established between the light transmittance and the microwave attenuation. The results are applicable to any transparent glass coated with any thin metallic film.