Showing papers on "Diffraction grating published in 1968"

Three-dimensional light beam scanner utilizing tandemly arranged diffraction gratings

Abstract: A light beam scanning apparatus including a rotatable disc having a plurality of focusing elements disposed in an annular or spiral pattern such that an impinging light beam is intercepted in succession by each of the focusing elements and deflected along a plurality of adjacent lines thereby providing, in accordance with the characteristics of the focusing elements, either a two-dimensional scan pattern oriented respectively transverse or parallel to the direction of the focused light or alternatively a three-dimensional scan pattern encompassing the areas of the orthogonal two-dimensional patterns.

Holographic focusing diffraction gratings for spectroscopes and method of making same

Abstract: A method making a focusing diffraction grating including casting a diverging beam of coherent light on a photographic plate, casting a convergent beam of coherent light on the same plate so that the beams interfere with each other on the light-sensitive plane of the plate, and then developing the plate. A holographic focusing diffraction grating having a plurality of curved, spaced grating lines on the face of the grating, the lines having specific curves and spacing relating to specific predetermined wavelengths of light for diffracting specific wavelengths of light at predetermined angles. A spectroscope, spectrograph, or spectrometer having a holographic focusing diffraction grating.

Laser-beam modulation using grating diffraction effects

Abstract: An optical-diffraction modulator, using an electro-optic crystal excited by a periodic array of metallic conductors, is described. The operation of the device is in some ways similar to that of an acoustoelectric modulator; it differs from it in that it has a bandwidth, potentially very wide, which extends from d.c. It may therefore find application as a baseband modulator.

Coma Correction in Czerny–Turner Spectrographs

Abstract: Coma in Czerny–Turner spectrographs is compensated at more than one angle of diffraction if the grating angle is sufficiently great. Coma and spherical aberration are calculated for a specific case.

Formation of Carrier Frequency Holograms with an On-axis Reference Beam.

Abstract: In this method, a transmission grating is placed in front of the photographic plate. The hologram is formed in four exposures. After each exposure, the grating is translated by a quarter of its spatial period and the phase of the reference beam is shifted by 90°. An analysis shows that such a hologram is equivalent to one formed with an off-axis reference beam. Experimentally, holograms with carrier frequencies as high as 94 lines/mm gave good reconstructions. The new method should be advantageous when holograms are to be formed with sources of short coherence length or through phase distorting media.

Apparatus and method for producing multiple images

Abstract: Multiple images of a photolithography mask are produced, for simultaneously exposing a plurality of regions of a photoresist coating on a semiconductor substrate, by directing monochromatic light through the mask, collimating the light, and transmitting it through a first diffraction grating with vertical rulings and a second diffraction grating with horizontal rulings. The diffraction gratings each divide the light into a plurality of diffraction orders each containing the image to be recorded; and each of these images is imaged on the photoresist coating.

Multiply Diffracted Light in the Czerny-Turner Spectrometer

Abstract: At certain small angles of the grating, any in-plane spectrometer will pass stray light that has been returned by the reflecting optics for a second diffraction. Paths of this source of stray light and its structure have been calculated and confirmed experimentally.

Laser diffraction grating coupling mirror

Abstract: A diffracting mirror having a shallow surface modulation pattern in the form of a grating is used in a laser cavity partly to sustain resonance by specular reflection and partly to divert power into an external beam by diffraction. Diffractive coupling permits the external beam to emerge without passing through the mirror, thereby avoiding certain limitations of the present art. Various embodiments provide for single or multiple external beams, for collimated or convergent beams, and for modulated beams.

Efficient, high resolution, phase diffraction gratings

Abstract: Experiments on the sodium D lines and an 0.82‐A separated doublet in the iron spectrum have shown that holographically recorded dichromated gelatin diffraction gratings have resolving powers within 90% of theory. The diffraction gratings are of excellent optical quality, have background scatter less than 10−4 of the signal, are ghost free and have greater than 90% first‐order diffraction efficiency. Blazing is accomplished by rotating the grating to the incident angle which satisfies the Bragg condition for the blaze wavelength. The 3‐μ‐thick transmission gratings can be employed from 0.25 μ to at least 15 μ, with gelatin absorption interfering only at 2.6–4.0 μ and 5.8–8.5 μ.

Complex data processing system employing incoherent optics

Abstract: An optical system for processing analog information in the form of complex data without a requirement for coherent optics, wherein discrete pieces of data having magnitude and phase components are multiplied together in a parallel operation. Information to be processed is entered in the form of diffraction gratings upon a pair of spaced apart writing media, normally in a column-row arrangement of distinct resolution elements. Magnitude information is contained in the transmissivity of the resolution elements and phase information in the spatial frequency of the gratings. Processing of resolution element pairs is optically performed by imaging spatially filtered light from resolution elements of the first medium upon corresponding elements of the second medium by means of a telecentric lens arrangement, spatially filtered light from the second medium being detected to provide the processed information.

Fiber optics pulse width modulator

Abstract: An optical pulse width modulator having a spiral stack of optical fibers providing a plurality of independent channels of different length for the passage of light. A suitable light source is intensity modulated in accordance with an applied electronic signal waveform and the light directed through the stack of optical fibers. The light emerging from the fibers is correlated with a waveform pattern in an optical grating and detected photoelectrically as a width modulated signal representing the correlation function between the applied electronic signal and the optical grating.

Electromagnetic beam communication unit

Abstract: A modulation cell which has two crystals side-by-side and oppositely oriented are driven by the same electromagnetic frequency modulated signal transmitter to form in the cell two parallel but similar moving periodic electro-optic diffraction gratings. An electromagnetic signal carrier producing source, such as a laser, has its beam pass through the sides of the cell and both electro-optic diffraction gratings. The zero diffraction order of the beam after it leaves the crystal has a frequency component which corresponds to the frequency modulated signal. The modulation cell may be a liquid or gas unit, with two sets of transmitters and absorbers, or the modulation cell may contain two oppositely oriented side-by-side optical crystals having an integral electromagnetic wave guide along which the frequency modulated signal is passed to the crystal.

Apparatus for generating an approximation to a sine wave including a reading head with two spaced areas for scanning an optical grating

Abstract: The invention is concerned with a reading head for moving in relation to an optical grating for giving a position signal. The position signal may be made very nearly the true sine wave by appropriate choice of the spacing between apertures in the head in relation to the pitch of the grating and/or by appropriate shape of the apertures.

Reading head for detecting a modulated image

Abstract: This invention is a reading head having a number of photo cells for cooperating with an optical grating to give a position signal. Light for illuminating the grating is also used to illuminate a part of the cells displaced from the part where the grating image appears for setting up the cells in the position of minimum illumination.

A reflection technique for the survey of the deflection of flat plates

Abstract: An optical technique based on transparent diffraction gratings is described by which the deflection contours of deformed, nearly flat plates may be obtained to any required sensitivity between 0.00005 in. and 0.010 in. The theory of diffraction gratings in reflection arrangements is given and the optical requirements to eliminate perspective distortion are outlined. Experimental verification using diffraction gratings containing 1000 lines per inch to give a deflection sensitivity of 0.00081 in./fringe shows the method to be reliable.

Application of Diffraction Gratings to Measurement of Strain of Dental Materials

Abstract: Strains occurring on application of loads to small specimens of dental materials were determined by measuring the changes in the angle of the beams of light diffracted from gratings ruled on the specimens. The method gives a rapid response to stress and is effective over very short gauge lengths.

Optical correlation of electronic pulses

Abstract: A moving waveform density image induced in an ultrasonic light modulator by an applied electronic pulse is optically correlated with a diffraction grating formed by grooves in a transparent plate inserted in the modulator. A collimated light beam passing through the modulator transversely of both the moving waveform density image and grooved plate is optically diffracted and the diffracted light is focused by a lens upon a slit preceding a photodetector in such a manner that only a lower order of the diffracted light passes through the slit. The photodetector responds to changes in light intensity resulting from phase correlation of the density image and the grooves in the plate to provide an electrical output signal representing the correlation function. Pulses of carrier wave energy which are narrow relative to the full optical aperture of the correlator are expanded and pulses which are long relative to the full optical aperture are compressed by the device.

Diffraction grating x-ray spectrometer wherein an electron beam is scanned across a fixed x-ray emitting element

Abstract: A diffraction grating spectrometer having an X-ray tube in a fixed position, the ray-source of which is rapidly moved back and forth on a definite curve. Diffracted beams from the grating surface are focused on a slit of a fixed electronic counter and the intensities of the spectral distribution are observed or measured by a suitable means. The positions of the ray-source and the counter are the reverse of those in the previously known spectrometers.

Spurious Radiation in Littrow-Mounted Grating Monochromators

Abstract: In this note we discuss two unusual types of “scattered ” radiation that can occur in Littrowmounted grating monochromators. Here, “scattered” radiation refers to diffracted radiation that reaches the exit slit by paths other than the one for which a monochromator was designed. Such spurious radiation usually will be out of focus at the exit slit and may not be noticeable in many applications. However, its presence can lead to serious error in the measurement of the absorption coefficient of a band, since the intensity at the exit slit for a particular grating angle will be the sum of the desired intensity at the correct wavelength and the spurious intensity at another wavelength.

Rapid access data storage and retrieval system

Abstract: Superimposed angularly oriented diffraction gratings are recorded on sheets of magnetic film to provide high-density data storage on each sheet, each recorded grating representing a particular binary digit. Optical readout is accomplished by diffracting a beam of monochromatic light with the gratings on any selected sheet to produce first order diffraction images in the form of spots on an output plane according to the binary digits recorded on the sheet. The locations of the spots thus formed on the output plane are indicative of data recorded on the sheet. The sheets may be stacked to provide compact, threedimensional storage of data.

Diffraction gratings for moire-fringe strain analysis

Abstract: The experimental technique described above allows the use of gratings produced by a process which is both inexpensive and simple, while being capable of giving results with errors of 3 percent or less with reasonable care. The grids have good mechanical strength and toughness, and will therefore stand up to a certain amount of abuse. The 3,000 lines/in. gratings used do not appear to be the limit to the fineness which can usefully be employed by this technique.