Showing papers on "Diffraction grating published in 1971"

Poly(methyl methacrylate) dye laser with internal diffraction grating resonator

Abstract: We describe a compact monochromatic (0.1 A) dye laser, which consists of a pair of Bragg phase gratings photodielectrically induced inside a bulk sample of poly (methyl methacrylate), PMMA, doped with rhodamine 6G. The laser frequency can be selected by choice of grating period from the usual broad (∼200 A) emission spectrum of the dye.

A Simple lnterferometric Method of Beam Collimation

Abstract: There are two common methods of determining the degree of collimation: auto collimation and shearing interferometry. The simplest method is the auto collimation technique, but it only indicates collimation by comparing the size of the source with its image. On the other hand the spacing of the fringes in shearing interferometry is a direct measure of the degree of collimation. Recently, Langenbeck derived a method that used

Recording of a continuous tone focused image on a diffraction grating

Abstract: A RECORDING MEDIUM BLANK IS EMPLOYED COMPRISING A SUBSTRATE HAVING A DIFFRACTION GRATING, COMPOSED OF A PLURALITY OF SPACED LINE RIDGES, ON A SURFACE THEREOF, TOGETHER WITH A PHOTORESIST DISPOSED ON THIS SURFACE WHICH FILLS THE SPACES BETWEEN ADJACENT LINE RIDGES. THIS PROVIDES A SUBSTANTIALLY SMOOTH EXTERIOR SURFACE OF THE PHOTORESIST WHICH IS SITUATED IN PROXIMITY WITH THE RESPECTIVE TOPS OF THE LINE RIDGES MAKING UP THE DIFFRACTION GRATING. BY EXPOSING SUCH A RECORDING BLANK TO A FOCUSED IMAGE OF ANY COMPLEX OBJECT AND THEN DEVELOPING THE PHOTORESIST, A DIFFRACTION GRATING WITH A MODULATED EFFICIENCY IS FORMED, CONSTITUTING A SYNTHETIC FOCUSED IMAGE HOLOGRAM; WHICH DISPLAYS THE ORIGINAL FOCUSED IMAGE WHEN PROPERLY VIEWED. A STAMPING MASTER, WHICH CAN BE PREPARED FROM THIS MODULATED GRATING RECORD, IS USEFUL IN EMBOSSING REPLICATIONS ON THERMOPLASTIC MATERIAL, SUCH AS VINYL FOR INSTANCE.

Moire Fringe Multiplication with a Nonsymmetrical Doubly Blazed Reference Grating

Abstract: A fine reference grating and coarse specimen grating in series are illuminated so that two dominant diffraction sequences take symmetrical paths in the intergrating space. In this optimum configuration, observation is on or near the axis of symmetry. Moire sensitivity is that of the reference grating and independent of the specimen grating. The contour map described by moire fringes depicts in-plane displacements uniquely, being insensitive to thickness and taper of gap between gratings. Moire fringes are nearly perfect two-beam interference fringes of superb contrast. Existing gratings blazed for single-order dominance can be used under conditions that produce the required double-order dominance. In experimental evaluations, coarse gratings of 200 rulings/cm were mated with various reference gratings up to 12,000 rulings/cm for fringe multiplications by factors up to 60.

Polarization properties of a grating spectrograph.

Abstract: The 13.7-m Czerny-Turner spectrograph at the McMath solar telescope is evaluated with regard to polarization properties. Let I‖ = the transmissivity of the spectrograph for incident light linear polarized parallel to the entrance slit and I⊥ = transmissivity for light polarized perpendicular to the entrance slit. The ratio I‖/I⊥ was measured photoelectrically as a function of wavelength in six diffraction orders. Values of this ratio vary from 0.3 to 20. It is shown that spectrograph transmission as a function of polarization may cause large photometric and radiometric errors. This fact is not unique to this particular instrument. Two mechanisms appear to contribute to the polarizance of the grating. These are: (1) the Rayleigh or Wood’s anomalies in which polarizance maxima and minima occur and (2) a vector wave interaction introduced because groove dimension is nearly the same as the wavelength. For λ > groove depth it is found that the wavelength of a peak polarizance (λp) is given by λp = 0.7d cosθ, where d is the ruling separation and θ is the grating angle. Photoelectric scans of the solar spectrum were made across several of the Wood’s anomalies to obtain their profiles.

Numerical Method for the Analysis of Diffraction Gratings

Abstract: A general numerical technique for analyzing diffraction gratings of arbitrary groove shape as electromagnetic boundary-value problems is suggested. The method yields the induced surface current, from which the energies in various radiating orders can be conveniently obtained. Computed results are compared to the theoretical as well as the experimental results available in the literature. The accuracy and versatility of the technique are demonstrated together with its economy and convenience.

Method for optical detection and/or measurement of movement of a diffraction grating

Abstract: A method for optical detection and/or measurement of movement of a diffraction grating which is characterized in that the vertical movement of the diffraction grating in respect to a standard parallel beam is detected based on variation in interference fringes produced by diffracted waves from the grating moving in the standard parallel beams.

Information record utilizing diffraction grating and methods of recording and reproducing the information thereof

Abstract: In a system for recording and reproducing picture information, a record medium utilizing diffraction gratings modulated in accordance with the picture information which, upon reproduction effected by directing light therethrough, the zero-order diffracted light is modulated in accordance with the picture information. The picture information-representing diffraction grating is initially recorded on a master from which release prints may be made on inexpensive sheet plastic material, for example, by mechanical embossing techniques.

Two-wavelength holographic interferometry for transparent media using a diffraction grating.

Abstract: A new technique of two-wavelength nondiffuse holographic interferometry is demonstrated that is capable of producing interferograms of transparent media with high or low sensitivity. Incorporating an arrangement similar to Bryngdahl’s longitudinally reversed shearing interferometer, the technique works by superposing the reconstructed true and/or conjugate images of two transmission image holograms of the test medium recorded at different wavelengths. Extensions of the technique allow one to record interferograms sensitive only to the optical dispersion of the test medium and to generate light beams with phase distributions equal to the sum or difference of the phases of the original object beams.

Optical diffraction grating scanning device

Abstract: An optical scanning device comprises a source of monochromatic light and diffraction gratings on a spherical concave surface for producing a number of light-spots having a diameter of between 0.1 and 100 microns. The concave surface is rotated so that the light-spots describe a single circle intersecting, along the scanning line, a surface to be explored.

Diffraction grating with two diffracting surfaces

Abstract: A spectral dispersion reflective grating comprises a vacuum deposited metal film with straight, parallel grooves. The film is of a thickness such that it is opaque and both its surfaces are substantially identical. The film is supported on a glassy blank or frame which permits light to be transmitted to, and reflectively diffracted from, either or both of the film surfaces. Elements on the support detachably engage a grating in the mount for use of either grooved film surface or for simultaneous use in a double monochromator. The support elements define a plane parallel to the film plane insuring that in reversible or scanning use both film surfaces will maintain a desired relation in a scanning or reversible spectrometric system. When the two film surfaces are on a single glassy blank or contained between light transmissive glassy blanks of different refractive indices, different blaze wavelengths appear outside the blanks at each side of the grating without changing the spectral dispersion.

Theory of Certain Diffraction Gratings Produced by the Holographic Method

Abstract: It is now well known that a system of interference fringes photographed on a photographic plate has very interesting properties when used as a diffraction grating. This paper considers two cases. One is when the photographic plate is a plane surface; the aberration properties of this are worked out as a function of wavelength. There are three positions for which the spherical aberration is zero. Of these, one is of little interest as this is simply zero-order position. Another case considered was that of a photographic plate in the form of a concave spherical surface. In this case, there are three positions at which the spherical aberration is zero. The nature of variation of spherical aberration between these zero-aberration positions is presented in the form of curves computed from the theory of these gratings.

Holographic grating formation in photopolymers—Polymethylmethacrylate

Abstract: Polymethylmethacrylate has been sensitized to 4880 A light and used as a holographic recording medium. The polymer is sensitized with a material which may itsel be degraded by exposure to ultraviolet light. The new process is, therefore, both self-developing and fixable without chemical processing. Holographic diffraction gratings written into this material have diffracting efficiencies as high as 70 percent. Various parameters such as angular selectivity, film thickness, variation of diffracting efficiency with writing angle etc., have been studied. The spontaneously produced diffracted intensity is so high that efficient interference between first and zero ordes is observed during the writing process.

A method for directly determining surface strain fields using diffraction gratings: Method proposed by author is based on a spatial filtering process carried out on the diffraction pattern generated by a grating applied to the specimen surface

Abstract: This paper describes a new method for determining the strain distribution at the surface of solid bodies. The method is purely optical; it uses the diffraction phenomena generated by a copy of a grating that is applied to the specimen. A suitable mask performs filtering of the diffraction pattern; the image that is reconstructed from this filtered pattern shows light and dark areas; it is shown that the boundary line of those areas is the locus of points exhibiting the same value of strain, measured along a certain direction.The magnitude of the strain can be easily calculated; it can be adjusted by a simple translation of the filter. A theoretical description of the system and some experimental results are presented.

Control of Acoustic Surface Waves with Photoconductive CdS Film

Abstract: Optical patterns imaged on photoconductive CdS films have been used to generate, detect, attenuate, and reflect acoustic surface waves on a 100‐MHz LiNbO3 delay line. Optically induced acoustic attenuation on the order of 1 dB/wavelength has been measured. A 180° reflection coefficient of approximately −7 dB has been observed from an optical grating, and 90° (right angle) reflect on has also been observed with a different optical grating. A transducer using an optical pattern (rather than evaporated interdigital electrodes) has been constructed with a one‐way conversion efficiency of −20 dB.

Holographic readout system employing predispersion diffraction grating

Abstract: A hologram recorded with coherent wave energy of a predetermined wavelength is read out with broad-band energy by employing a predispersion diffraction grating for angularly dispersing broad-band wave energy incident thereon to provide each angular component of the output beam derived therefrom with a different angular orientation with respect to the hologram. By appropriately selecting the line spacing of the diffraction grating with respect to the period of the spatial carrier of the hologram, a hologram read out with the output beam of the grating may have the respective reconstructed images corresponding to each component wavelength positioned in substantial coincidence with each other.

New type interference selective modulation spectroscopy.

Abstract: A new method of interference spectroscopy is described. The spectral element is detected photoelectrically by taking the interference between the reflected and the diffracted beams by a modified Michelson interferometer without any computation. The spectrum is scanned by the rotation of the diffraction grating of the interferometer. Modulation of the spectral signal is carried out by the vibration of the reflecting mirror. The principle of the method and the first results are described. Source effects are also discussed.

Improving the efficiency of very low efficiency holograms by copying.

Abstract: Sometimes holograms are constructed with very high ratios of reference beam intensity to object beam intensity. This occurs when the object is dimly illuminated for safety reasons or be­ cause of available power limitations. The diffraction efficiencies of the resulting holograms are particularly low. A simple method of improving the efficiency is to make a second, or copy, holo­ gram from the first one. In the case of an intensity hologram diffraction grating formed by the interference of two plane waves, the diffraction efficiency can be written as η = (χE)/K (see Ref. 3). In this equation χ is the slope of the transmittance-exposure curve of the film, E is the exposure due to the reference beam, and K is the ratio of reference beam intensity to object beam intensity. Operation over the linear portion of the transmittance-exposure curve is assumed so that K would typically be 13.5 or greater for Kodak 649F film. A very low efficiency grating is obtained if K is much larger than this number or if the operating point is not chosen such as to maximize the term χE. A more efficient holo­ gram can be obtained from a poor original hologram by using the copying construction shown in Fig. 1. In making the copy, the resulting efficiency depends only on the new values of K, χ and E. Thus, a resulting efficiency equal to that of a good conventional hologram can be realized. For Kodak 649F, the measured value of (χE) is 0.3 when the bias transmittance is 0.5. With K = 13.5, the theoretical ef­ ficiency is 2.2%. For Agfa-Gevaert films 10E70 and 10E75, the value of (χE) is about 0.25 when the bias transmittance is 0.5. For the Agfa-Gevaert film we do not know the value of K a t which nonlinearities appear. Letting K = 13.5 gives an ef­ ficiency of 1.85%, but this might not be the best result obtain­ able. The efficiency of many types of very low efficiency holograms, in addition to gratings, can be improved by making a copy holo-

Position detection and control devices

Abstract: Apparatus for monitoring relative movement of a member, which includes an extended diffraction grating, a plurality of cooperating index gratings, at least one source of cyclically modulated radiation and photo-electric transducer means arranged so that the extended grating is mounted on the movable machine part and cyclically modulated radiation passes through the extended grating and the fixed index gratings to the photoelectric transducer means so as to produce therefrom, through the moire fringe effect, a cyclic electrical signal which is constant in phase while the member is stationary and varies in phase in accordance with movement of the member.

Fourier Transform Formulation of Optical Imaging Applied to the Grating Mounting

Abstract: The fourier transform formulation is used for the spectral image formation of a point source in a concave grating mounting (in-plane). In applying this formulation to an extended source, consideration is given to the condition of slit illumination. This formulation is applied to the Monk-Gillieson mounting, and the resolving power is discussed.

Some thoughts on the information obtained by a high resolution grating spectrometer.

Abstract: The possibility of obtaining a transfer function of a diffraction grating affected by blank and ruling errors is examined and a simple experimental procedure for an approximate determination of aberration function is described. Using this aberration function, we have obtained a wavelength-dependent transfer function in order to perform the best restoration of the grating output.

Application of phase modulation to digital data recording by means of superposed diffraction gratings.

Abstract: Optical phase modulation has been applied to a system for digital data recording based on the photography of a multiplicity of superposed interference fields. When piezoelectrically driven mirrors or electro-optic crystals are placed suitably in the interfering beams and sinusoidally excited to the proper amplitude, the corresponding fringe pattern exposure is effectively spoiled. Since the effect arises from variations in optical path or refractive index, tolerances on optical quality are relatively modest. Extinction ratios in excess of 100:1 are readily obtained.

Granulationsfreie Rekonstruktion von Hologrammen

Abstract: Described is a method for holographic reconstruction of diffusely illuminated objects which suppresses the known effect of granularity. The experimental setup is modest. It consists of a source of polychromatic light. Additionally there are inserted a simple ground glass and a diffraction grating in the reconstruction wave. Holographic reconstruction without granularity is achieved by incoherent superposition of longitudinal modes of the reconstruction wave.