The design and fabrication of dielectric grating structures with high diffraction efficiency used in reflection or transmission is described. By forming a multilayer structure of alternating index dielectric materials and placing a grating structure on top of the multilayer, a diffraction grating of adjustable efficiency, and variable optical bandwidth can be obtained. Diffraction efficiency into the first order in reflection varying between 1 and 98 percent has been achieved by controlling the design of the multilayer and the depth, shape, and material comprising the grooves of the grating structure. Methods for fabricating these gratings without the use of ion etching techniques are described.

Multilayer dielectric diffraction gratings

A selectively absorptive, mulitlayer wire-grid polarizer for polarizing incident light includes a stack of thin film layers disposed over a substrate, including a wire-grid array of elongated metal elements having a period less than half the wavelength of the light One of the layers can include a thin film layer with a refractive index greater than a refractive index of the substrate One of the thin film layers can include a dielectric array of non-metal elements One of the layers includes a material that is optically absorptive to the incident light

Selectively absorptive wire-grid polarizer

An optical low pass filter for use in an imaging device including an objective lens and a solid state image sensor forming a plurality of picture elements thereon, which filter comprises a diffraction grating disposed between the objective lens and the solid state image sensor The diffraction grating is of a type which the periodicity of an image of the diffraction grating projected onto the solid state image sensor by the objective lens is selected to be twice or 1/n of the periodicity of the picture element, wherein n represents an integer The applicable imaging device may be of a type comprising an objective lens, a solid state image sensor forming a plurality of picture elements thereon, and a color filter array disposed on the solid state image snesor and including a plurality of sets of different color filter elements, or of a type comprising a single tube type color imaging device having an evacuated glass envelope, an objective lens and a color filter array including a plurality of sets of different color filter elements

Optical low-pass filter

Aliasing in detected image samples is substantially reduced by a spatial low-pass prefilter employing a diffusing surface variably spaced from an imager and situated in the path of projected image light to cause greater blurring in lower resolution regions of the imager than in higher resolution regions thereof, such that the cutoff spatial frequency varies continually in accordance with the variable resolution of the system

Spatial prefilter for variable-resolution sampled imaging systems

A reflection repressed wire-grid polarizer (10a-e) for polarizing incident visible or infrared light (12) and selectively repressing a reflected polarization includes at least three layers (18a-d) disposed on a substrate (14). A polarizing wire-grid layer (18a) has an array of parallel metal wires (22) with a period less than half the wavelength of the incident light. A reflection-repressing layer or grid (18c) includes an inorganic and non-dielectric material which is optically absorptive of visible or infrared light, A dielectric layer or grid (18b, 18d) includes an inorganic and dielectric material.

Reflection-repressed wire-grid polarizer

A combination optical low pass filter adapted for use in a single or double tube color television camera is provided with a phase retarding pattern on a transparent substrate. The pattern includes optical elements having a transmissivity which varies with the wavelength of light passing there through so that the optical low pass filter functions as both a phase diffraction and an amplitude diffraction filter. Medium indexed filler material can further supplement the pattern to eliminate any light scattering.

Combination optical low pass filter capable of phase and amplitude modulation

A color encoding video system such as a single or double tube color television camera has an optical grating low pass filter positioned in a plane substantially adjacent the focal plane of the image pickup tube. A separate and interchangeable image forming objective optical system can be mounted on the body of the camera for focusing an object scene on the photosensitive element of the pickup tube. The filter grating pattern can be stripes or lenticular lenses and has a spatial frequency along the scanning direction limited to a value not greater than the highest spatial frequency available for detection of the luminous signals whereby optical imaging problems are prevented regardless of the aperture opening of the objective optical system.

Color encoding video system with optical low pass filter

PURPOSE:To cut off the space frequency of the grid shadow by making larger the space frequency of grid itself of phase grid type optical low-pass filter than the maximum frequency of luminance signal.

Yukio Okano

Papers

Combination optical low pass filter capable of phase and amplitude modulation

Color encoding video system with optical low pass filter

Optical system of uniitube type color tv camera using optical lowwpass filter