Abstract: A terrestrial refractometer comprising a gastight enclosure of substantially invariant transverse section and having a linearly movable endwall which varies in position in accordance with ambient temperature and pressure, the enclosure containing a fixed mass of a gas which at least approximates to an ideal gas; sensing means responsive to the linear position of the endwall; and compensating means arranged to apply a compensating factor which is proportional to the linear movement by the endwall from its position under conditions of standard temperature and pressure.

Abstract: Light from a laser, converted into pulses by a chopper, is trained upon an end of an optical fiber--whose refractive-index profile is to be determined--through a first polarizer, a beam splitter, a focusing objective and a 90.degree. phase shifter, the space between the objective and the fiber end being occupied by a fluid whose refractive index is close to that of the fiber. Light reflected from the fiber end, having passed twice through the phase shifter, has a plane of polarization orthogonal to that of the incident light and is passed by a second polarizer, to which it is directed by the beam splitter, onto a photodiode feeding a calculator that also receives a reference signal from another photodiode to which part of the polarized laser pulses are directly reflected by the beam splitter. Spurious reflections from the objective surface, which do not pass through the phase shifter, retain the original polarization and are rejected by the second polarizer.

Abstract: To facilitate determination of the refractive-index profile of an optical fiber by the near-field technique, the fiber to be examined is inserted into a body of transparent liquid held by surface tension in a surrounding capillary tube also made of light-transmissive material. The tube, which is axially coextensive with the inserted fiber, has a refractive index less than the minimum index of the fiber core and cladding whereas the liquid has a refractive index exceeding the maximum index of the fiber core.

Abstract: Method and apparatus for determining the refractive index of an optical film over a wide spectral range is described that involves measuring the changing radiant reflectance (or transmittance) of the film at various wavelengths as it is being deposited upon a substrate, as for example by vacuum deposition process. By determining the values of the extreme limits, an envelope of the peak reflectance can be developed from which the film's index of refraction is obtained over the entire spectral range that is situated between the two extreme wavelength channels.

Abstract: A terrestrial refractometer comprises a gastight enclosure containing a fixed mass of a gas which at least approximates to an ideal gas, at least a part of the enclosure being movable in response to changes in the volume of the gas in accordance with changes in ambient temperature and pressure; constraining means for constraining said movable part so as to maintain the gas at a constant volume; and sensing means for providing a signal related to the force applied to the movable part by the constraining means.

Abstract: An apparatus for analyzing the deleterious characteristics of optically transparent bodies, including distortion, multiple imaging and birefringence. A beam of light is projected along an optical axis onto a beam splitter. The reflected segment passes through the transparent body and is then reflected back along nearly the same path toward the beam splitter by a retro-reflective screen lying at the image plane of the beam. The portion of the reflected beam passing directly through the beam splitter is detected by an optical sensor in substantial orientation with the axis of the beam reaching it. Distortions and multiple imaging are detected by shape changes and images, respectively, in a pattern of opaque areas superimposed on the originating beam. Birefringence is analyzed by polarizing the originating beam and observing the color pattern and intensity reaching the sensor.

Abstract: The method comprises measuring the heat transfer between a specimen of the substance in condensed phase and an ambient gas. The heat transfer is detected by measurement of the amplitude of the angular movement of a pencil of light which is directed substantially parallel to the surface of the specimen subjected to energization variable in time, and which passes through an area located close to said surface. The device comprises a specimen support and a monochromator.

Abstract: A visual acuity device measures the visual acuity of a patient's eye by directing a pulsating beam of light on the eye and detecting the resulting reflection. A primary pattern having a pattern formed by transparent and non-transparent portions is positioned in the optical path of the pulsating beam of light. A fixed pair of analyzer or secondary pattern is positioned in the optical path of the beam of light reflected from the patient'eye. One of these analyzer or secondary patterns has a pattern which substantially corresponds to the pattern of the primary fixation pattern and the other has a pattern which is the negative mirror image of the pattern of the first analyzer or secondary pattern. The beam of light reflected from the patient's eye is divided by a beam splitter so that each of the analyzer patterns receives the reflected image of the primary pattern from the patient's eye.

Abstract: An apparatus for detecting the angular deviation from an axis imparted to a ray when passing through a transparent medium, for resolving the angular deviation into its components, and for generating electrical signals accurately representing the magnitudes of such components. A laser beam is projected along an optical axis through the medium and focussed by a displacement compensation lens. The beam is divided into channels with a beam splitter, each channel being incident upon a transmission diffraction grating. Each grating, characterized by fine parallel lines of substantially random size and spacing, generates a fan-shaped region of luminous energy. At a distance equal to the focal length of the lens, the fan-shaped regions cross detector arrays aligned parallel to the grating lines. A change in the angular deviation proportionally translates the crossing point along the detector array.

Abstract: A method of optically measuring the concentration of carriers in a doped region of a semiconductor wafer includes the step of selectively introducing conductivity modifiers into both the wafer and a test substrate simultaneously to form respectively the doped region in the wafer and a diffraction grating pattern in the substrate including periodically-spaced doped strips. The diffraction grating pattern is exposed to a beam of monochromatic light, and the intensity of one of the diffracted beams is measured, whereby the magnitude thereof is a measure of the carrier concentration in the doped region.

Abstract: This application describes a nondestructive method for determining the refractive index profile of optical fibers and fiber preforms by measuring the density distribution of the light that is focused by the fiber/preform core acting as the lens. The fiber/preform is immersed in an index matching medium and illuminated by means of a collimated light beam directed at right angles to the fiber/preform axis. The density distribution of the light focused by the fiber/preform core is then measured along a direction normal to the fiber/preform axis at a distance L from the axis that is less than the focal length of the fiber/preform. The index profile is determined from these measurements by two numerical integrations.

Abstract: An objective eye examination apparatus generates rotating pencil rays of infrared light and focuses one of them on the eye pupil via an adjustable wedge reflector 55, 57 for varying the effective length of the optical axis. Light reflected back by the retina and returned into the optical system is passed through an image rotator 41 onto a quadrant photocell 43. The wedge reflector is adjusted until the differential outputs from the photocell reach a desired value, whereby the necessary reflector adjustment is indicative of refractive power. Unfocusable fogging light is also introduced into the eye via a dichroic mirror 39, and a further photocell 35 is disposed to receive light reflected back from the cornea only when the eye is properly positioned and open.

Abstract: Apparatus and method employing line-of-sight wave propagation for measurement of various quantities such as velocity and refractivity structure of a transmission medium at selected locations remote from the measuring device.

Abstract: A detector used in apparatus for measuring variations in the composition of a liquid includes a cell utilizing the Christiansen effect on light transmitted by the liquid flowing through the cell filled with particulate matter. The liquid and the particulate matter have indices of refraction that are substantially equal to one another at a specific wavelength. Variations of the transmitted light can determine changes of the refractive index of the liquid.Differences in the intensity of light transmitted through a sample cell and a reference device can be determined.

Abstract: An auto-refractometer according to this invention comprises a light beam source for producing a measuring ray wherein beams from a pair of invisible infrared ray emission diodes are alternately flickered, and real images of the beams are converged on respective sides of ridges at the output side of a V-shape coincidence prism at positions close to the ray axis thereby reducing the horizontal distance between the beams. A measuring optical system includes a transmitting collimater which projects said measuring ray passing through a vertical slit to permit focusing of a slit image on the retina. A receiving collimator collects beams reflected from the cornea and the retina, and by a semi-transparent mirror, and directs them via a reflection mirror to an interference bar which interferes with the beam from the cornea. A split prism divides the beam received from the retina, and a pair of elements photo-electrically convert the divided beam into electrical outputs.

Abstract: A measuring device includes means for producing an image of a transmitting iffraction grating, means for shifting the image by an amount related to the quantity to be measured, and a receiving diffraction grating for measuring the shift of the image. Each diffraction grating includes a plurality of tracks of increasing pitch, each track of the transmitting grating having a corresponding track on the receiving grating. The device may form a refractometer.

Abstract: An apparatus for measuring the index of refraction of a specimen includes a stage plate having a small exposure opening behind which are located a point source infra-red light emitting diode and a photoresistor. A first lens focusses the LED point source along a first optical axis at the exposure opening on the plane of the specimen receiving face of the stage plate defining a sensing area and a second lens focusses the image on the sensing area along a second optical axis onto the photoresistor. The optical axes form equal angles to the perpendicular to the exposure plane at the center of the sensing area. The light emitting diode and the photoresistor are connected through a common normally open switch to a battery.

Abstract: Apparatus and method for detecting the refractive index and rate of fluid flowing through an elongated flow cell, having applications in liquid chromatography. The cell may be of circular cross section and has an input window in one end, an exit window in the other, and a longitudinal side wall. A light source directs divergent light through the entrance window, longitudinally through the cell, to pass through the exit window and be sensed by a photoelectric detector outside the exit window. In a first embodiment, heat transmission apparatus connected to the cell establishes a constant temperature gradient in the cell. This temperature gradient, preferably, has a component perpendicular to the longitudinal dimension of the cell and extending toward the center of the cell. This causes the density of the fluid in the cell to vary as an increasing function of its distance from the walls. The index of refraction of the fluid thus, in this embodiment, increases with distance from the cell walls.

Abstract: An optical testing apparatus for use in non-destructive testing of optical omponents to evaluate their operational requirements. The optical component to be tested is mounted on a fixture that allows its accurate alignment and rotation so the entire surface area of the optical component can be scanned in discrete areas. A laser light source is positioned to illuminate the optical component with coherent light beams or rays. An aperture positioned in the light beam permits adjustment of the diameter of the light beam impinging on the optical component to be evaluated. Whenever an imperfection is present in the optical component a portion of the light rays illuminating the imperfection will be disarranged or scattered. Both the non-scattered and scattered light rays are gathered by means of pyroelectric detectors and their outputs are compared for obtaining an electrical signal that is proportional to the intensity of the scattered light caused by the imperfection.

Abstract: Device and process for testing the optical transfer function of a lens system which comprise employing as the object or target the laterally moving-fringe pattern produced by convergence of two monochromatic coherent-radiation beams of equal size and intensity and slightly different frequency. A second fringe pattern may be employed as the reference standard. Both the target and reference patterns can be varied simultaneously in spatial frequency or fringe period. The system and process can test both modulation transfer function and phase transfer function accurately at any monochromatic wavelength produced by an available coherent-radiation source to which the test lens system is transparent, e.g., ultraviolet or shorter, visible, and infrared or longer. When polarized monochromatic radiation is used, the invention can also be employed to determine the polarization characteristics of the lens.