471 results about "Phase mask" patented technology

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An improved opto-electronic imaging system which is adapted for use with incoherently illuminated objects, and which produces final images having a reduced imaging error content. The imaging system includes an optical assembly for forming an intermediate image of the object to be imaged, an image sensor for receiving the intermediate image and producing an intermediate image signal, and processing means for processing the intermediate image signal to produce a final image signal having a reduced imaging error content. A reduction in imaging error content is achieved, in part, by including in the optical assembly a phase mask for causing the OTF of the optical assembly to be relatively invariant over a range of working distances, and an amplitude mask having a transmittance that decreases continuously as a function of distance from the center thereof. The reduction in imaging error content is also achieved, in part, by including in the processing means an improved generalized recovery function that varies in accordance with at least the non-ideal calculated IOTF of the optical assembly under a condition of approximately optimum focus.

The present invention provides methods and devices for fabricating 3D structures and patterns of 3D structures on substrate surfaces, including symmetrical and asymmetrical patterns of 3D structures. Methods of the present invention provide a means of fabricating 3D structures having accurately selected physical dimensions, including lateral and vertical dimensions ranging from 10 s of nanometers to 1000 s of nanometers. In one aspect, methods are provided using a mask element comprising a conformable, elastomeric phase mask capable of establishing conformal contact with a radiation sensitive material undergoing photoprocessing. In another aspect, the temporal and/or spatial coherence of electromagnetic radiation using for photoprocessing is selected to fabricate complex structures having nanoscale features that do not extend entirely through the thickness of the structure fabricated.

A phase-difference sensor measures the spatially resolved difference in phase between orthogonally polarized reference and test wavefronts. The sensor is constructed as a pixelated phase-mask aligned to and imaged on a pixelated detector array. Each adjacent pixel of the phase-mask measures a predetermined relative phase shift between the orthogonally polarized reference and test beams. Thus, multiple phase-shifted interferograms can be synthesized at the same time by combining pixels with identical phase-shifts. The multiple phase-shifted interferograms can be combined to calculate standard parameters such as modulation index or average phase step. Any configuration of interferometer that produces orthogonally polarized reference and object beams may be combined with the phase-difference sensor of the invention to provide, single-shot, simultaneous phase-shifting measurements.

A method and apparatus for reducing speckle in a laser illumination system uses a despeckle device including an optical retarder providing an odd integer multiple of substantially half-wave retardation for light emitted from a coherent laser in the laser illumination system. The near half-wave optical retarder has a substantially constant retardance and a spatially varied slow axis. The spatially varied slow axis imposes a phase mask on the beam of light, which provides sub-resolution optical phase modulation to a resolution spot on the detector. The near half-wave optical retarder is actuated mechanically or electrically to vary the sub-resolution optical phase modulation within an integration time of the detector.

A method and system for encrypting multi-dimensional information utilizing digital holography is presented. A phase-shifting interferometer records the phase and amplitude information generated by a three-dimensional object at a plane located in the Fresnel diffraction region with an intensity-recording device. Encryption is performed by utilizing the Fresnel diffraction pattern of a random phase mask. Images of different perspectives of the three-dimensional object focused at different planes can be generated digital or optically with the proper key after decryption. After decryption, images of the object, focused at different planes, can be generated digitally or optically. The method allows for the reconstruction of the object with different perspectives from a single encrypted image. The method does not require sending the key exclusively through a digital communication channel. Instead, a copy of the random phase key itself can be sent to the authorized user. A method of forming an image of an object is disclosed. The method comprises forming an original hologram of the object; compressing the original hologram of the object to form a compressed hologram; decompressing the compressed hologram of the object to form a decompressed hologram; and reconstructing the object from the decompressed hologram to form a multi-dimensional image of the object.

A modified phase shifting mask is used to improve performance over traditional Zernike phase contrast imaging. The configurations can lead to an improved imaging methodology potentially with reduced artifacts and more than one order of magnitude gain in photon efficiency, in some examples. Moreover, it can be used to yield a direct representation of the sample's phase contrast information without the need for additional specialized post-acquisition image analysis. The approach can be applied to both wide-field and scanning configurations by using a phase mask including a pattern of phase elements and an illumination mask, having a pattern of holes, for example, that corresponds to a pattern of the phase mask.

The invention belongs to the fiber sensing technical field, and specifically relates to a multi-core fiber bragg grating (FBG) universal bending sensor; the multi-core fiber bragg grating (FBG) universal bending sensor is suitable for smart material and structure on-line detection and analysis, can control and monitor space structure space three dimensional positions and attitudes, and is formed by using the multi-core fiber bragg grating (FBG) as the basic sensing unit; the multi-core fiber bragg grating (FBG) universal bending sensor comprises multi-core fibers including one center fiber core, and the resting fiber cores are arranged around the center fiber core in quadrature distribution or symmetrical distribution; each fiber core in the same transverse position of the multi-core fiber uses the same phase mask slice to simultaneously expose the FBG; the central wavelengths of various Bragg gratings on the multi-core fiber are different; the multi-core fiber bragg grating (FBG) universal bending sensor can monitor various reflection wavelength changes of the multi-core FBG, thus measuring the bending amplitude and direction angles.

A device for recording a refractive index pattern in a photosensitive optical fiber includes a rotary disc formed with a phase mask in a circular pattern, which is rotated by an axis. The phase mask is illuminated with laser light in a region so that a moving interference pattern is formed. The optical fiber is moved along a path in synchronism with the moving interference pattern so that the pattern becomes recorded in the fiber. The pattern can be formed continuously over long fiber lengths, e.g., of the order of one meter.

The invention relates to a diffraction grating-forming phase mask which can make the diffraction grating to be formed substantially free of any defect, even when foreign matters or resins, etc. sublimed from an optical fiber are deposited on the surface of the phase mask. The phase mask 21 comprises a substrate and a grating form of repetitive groove (26)-and-strip (27) pattern for forming a diffraction grating by interference fringes of diffracted light through the repetitive pattern. An optically transparent protective layer 30 is applied over the surface of the substrate with the repetitive groove (26)-and-strip (27) pattern formed thereon.

The invention relates to securing of information utilising optical imaging technologies and more specifically to phase encryption and decryption of images. An image is encrypted into a mask having a plurality of mask resolution elements (X_m, Y_m) by encoding the image using e.g. a phase mask with an encoded phase value φ (X_m, Y_m) and an encoded amplitude value a (X_m, Y_m), and by further encrypting the mask (using e.g. a spatial light modulator) by addition of an encrypting phase value φ_c (X_m, Y_m) to the encoded phase value φ (X_m, Y_m) and by multiplication of an encrypting amplitude value a_c (X_m, Y_m) with the encoded phase value a (X_m, Y_m). The method of decrypting comprises the steps of decrypting the mask by radiating electromagnetic radiation towards the mask and inserting into the path of the electromagnetic radiation a complex spatial electromagnetic radiation modulator comprising modulator resolution elements, the decrypting phase value φ_d (X_d, Y_d) and the decrypting amplitude value a_d (X_d, Y_d) respectively, of a modulator resolution element (X_d, Y_d) being substantially equal to −φ_c (X_m, Y_m) and a_c⁻¹ (X_m, Y_m).

A waveguide-mode (WM) coupler having a plurality of single-mode fibers, each optically coupled to a different respective waveguide mode of a multimode fiber. The coupling optics employed by the WM coupler are scalable and include reflective fiber-tip coatings, polarization beam splitters, phase masks, and quarter-wave plates configured to overlap and/or separate the optical beams corresponding to different waveguide modes of the multimode fiber in a manner that does not cause a significant increase in the optical insertion losses with an increase in the number of optical channels in the WM coupler.

The invention relates to a double-random-phase optical color image encryption device and method, which belong to the field of optical image processing technique. The double-random-phase optical color image encryption device comprises an optical image encryption device and an optical image decryption device. The double-random-phase optical color image encryption device has high flexibility by adopting a joint fractional Fourier transform correlator, and the encryption technique based on the joint fractional Fourier transform correlator structure has high safety even if a correct phase mask cannot decrypt the original image information if the position has a slight change due to the translation variability of the fractional Fourier transform. The decryption device can be achieved only by arranging an electronic shutter of the encryption device and using the original illumination parallel light as the light source, and does not generate the optical field distribution conjugated to the encryption process. Based on the parallel processing characteristics of an optical information processing system, the double-random-phase optical color image encryption device can achieve color image encryption and decryption by use of single wavelength. Therefore, the double-random-phase optical color image encryption device has the advantages of simple structure, simplified system, lowered cost, high safe performance, and wide application range, and is convenient in operation.

The invention discloses an all-solid digital holography imaging system capable of reducing speckle noise, and belongs to the technical field of optical diffraction imaging and digital holography. The all-solid digital holography imaging system capable of reducing the speckle noise comprises a hologram shooting light path, a spatial light modulator, a sample to be detected, an image sensor and a computer. The reference light in the hologram shooting light path is directly incident to the image sensor, the object light in the hologram shooting light path passes through the spatial light modulator and the sample to be detected and then is incident to the image sensor, both the image sensor and the spatial light modulator are connected with the computer, under the control of different phase information provided by the computer, the spatial light modulator is loaded with different random phase mask plates, every time a random phase mask plate is loaded, the image sensor is controlled to record a hologram for one time, multiple holograms are continuously and automatically obtained, and all reproductive images of the holograms are overlapped. The speckle noise of the reproductive images of the digital holography imaging system can be automatically reduced, and the all-solid digital holography imaging system capable of reducing the speckle noise can be used for imaging detection which is relatively high in requirements for instantaneity and distinguishability.

In a laser processing method for accurately forming a convexo-concave structure on the surface of a glass substrate, a periodic optical intensity distribution of a laser beam is obtained by an interference between diffracted light beams of +1 degree and −1 degree emitted from a phase mask, onto which the laser beam is irradiated, in the vicinity of the emission side of the phase mask, and a glass substrate, on which a thin film is formed, is set in the area where the periodic optical intensity distribution is provided. As a result, the thin film is evaporated or ablated depending on the periodic optical intensity, thereby a diffraction grating, which has the same period as that of the varying optical intensity, is formed on the glass substrate.

The invention discloses an asymmetric double-image encryption method based on a joint of a fourier transformation and a phase cutting. Under modulation of random phase masks, two plain texts are modulated by the joint of the fourier transformation and the phase cutting, so that symmetrical and linear characteristics of a traditional double random phase encryption method are eliminated, so that the anti-attack capability of the encryption system is greatly improved. An encryption process, a decryption process and the asymmetry of an encryption key and a decryption key are achieved, and an optical asymmetric encryption system based on the double random encryption method is established. The test shows that, compared with traditional double random encryption techniques which are easy to be attacked, the asymmetric double image encryption method can resist violent attacks, known plaintext attacks, direct public key attacks and iterative amplitude recovery algorithm attacks, so that high security is provided.