Abstract: A method of manufacturing a hexagonal Group-III nitride semiconductor plate crystal using a crystal cutting wire. where the hexagonal semiconductor crystal has one principal face on one side and another principal face on an opposite side, and the hexagonal semiconductor crystal is cut by causing the crystal cutting wire to move so as to (i) divide the one principal face and the another principal face and (ii) satisfy conditions of Expressions (A) and (B): 25°<??90°??Expression (A); and ?=90°±5°??Expression (B) where ? represents an angle formed by a c axis of the hexagonal Group-III nitride semiconductor crystal and a normal line of a crystal face cut out by the wire, and ? represents an angle formed by a reference axis, which is obtained by perpendicularly projecting the c axis of the hexagonal Group-III nitride semiconductor crystal to the crystal face cut out by the wire, and a cutting direction.

Abstract: A method of manufacturing a hexagonal Group-III nitride semiconductor plate crystal using a crystal cutting wire. where the hexagonal semiconductor crystal has one principal face on one side and another principal face on an opposite side, and the hexagonal semiconductor crystal is cut by causing the crystal cutting wire to move so as to (i) divide the one principal face and the another principal face and (ii) satisfy conditions of Expressions (A) and (B): 25°<??90°??Expression (A); and ?=90°±5°??Expression (B) where ? represents an angle formed by a c axis of the hexagonal Group-III nitride semiconductor crystal and a normal line of a crystal face cut out by the wire, and ? represents an angle formed by a reference axis, which is obtained by perpendicularly projecting the c axis of the hexagonal Group-III nitride semiconductor crystal to the crystal face cut out by the wire, and a cutting direction.

Abstract: A plate crystal cut from a gallium nitride crystal with a crystal cutting wire, where the plate crystal has a principal face of (20?21), and a magnitude of warpage of the plate crystal is 1.0 ?m/mm or less in a line along the perpendicular projection of the c axis on the principal face passing through the center of the principal face.

Abstract: A method of efficiently manufacturing a hexagonal semiconductor plate crystal with small warpage is provided. The method of manufacturing a hexagonal semiconductor plate crystal is a method of manufacturing a hexagonal semiconductor plate crystal by cutting a hexagonal semiconductor crystal using a crystal cutting wire, wherein the hexagonal semiconductor crystal is cut by causing the crystal cutting wire to move relative to the hexagonal semiconductor crystal so as to satisfy the conditions of 25°<??90° and ?=90°±5° where ? represents an angle formed by the c axis of the hexagonal semiconductor crystal and the normal line of the crystal face cut out by the wire and ? represents an angle formed by a reference axis, which is obtained by perpendicularly projecting the c axis of the hexagonal semiconductor crystal to the crystal face cut out by the wire, and a cutting direction.

Abstract: An improved soft focus optical filter is provided and comprises a plurality of effective filter areas on a transparent substrate. The filter areas are designed specifically to modify the modulation transfer function of the filter so that a selective soft focus effect is achieved only for transmitted green light.

Abstract: An optical adaptor is provided to permit objective lenses designated for a certain image format to be used on optical devices having a smaller image format. Thus, 35 mm single lens reflex camera lenses can be mounted on a cinematographic camera and a T.V. camera. The optical adaptor includes a pair of mounts for attachment respectively to the objective lens and to the optical device. Mounted within the adaptor housing is a positive refractive lens system capable of shortening the focal length and increasing the aperture ratio of the objective lens system. The lens system satisfies the condition that the magnification, .beta., is equal to or less than 1 and the refractive power of a negative element lens .PSI..sub.1 to that of a positive element lens, .PSI..sub.2, in the lens system, satisfies the following;(4/.beta.)-4.5.ltoreq..vertline..PSI..sub.2 /.PSI..sub.1 .vertline..ltoreq.(4/.beta.

Abstract: A variable soft focus lens system particularly adapted for photography is disclosed. The lens system incorporates two lens groups, a first object side lens group having an image side, rearmost surface convex to the image side, and a second, image side lens group having an object side, foremost surface concave to the object side. An airspace separating the first and second lens group has a meniscus shape concave to the object side. A good quality soft tone image having undersirable aberrations well within tolerable limits, is attained by shifting at least the second lens group along the optical axis relative to the first lens group whereby the airspace separating the two lens groups and a spherical aberration of the entire lens system is varied. An image does not lose proper focus while the spherical aberration of the system is varied. The second lens group has a refractive power within specified limits in relation to the refractive power of the entire lens system.

Abstract: An optical low pass filter adapted for use in a single or double tube color television camera provided with an optical system including a color encoding filter for obtaining color or chrominance signals having the spatial frequency in a particular band. The low pass filter serves to cut off the high spatial frequency components of the image or luminance signals to eliminate the crosstalk between the chrominance and luminance signals. The low pass filter according to the present invention is a phase grating filter having the triangular-wave cross-sectional configuration, of which height is in a range given by a mathematical description.

Abstract: A variable soft focus lens system particularly adapted for photography is provided. The soft focus lens system includes at least two lens groups defining a meniscus shaped air space there between. The relative width of the air space can be variable by movement of one of the lens groups relative to the other. This movement can introduce a controlled amount of spherical aberration to provide within certain parameters a soft focus image with an acceptable Petzval sum and flatness of the image plane. Various embodiments of the present invention within the inventive parameters can be utilized and include both stationary and variable soft focus lens system.

Abstract: 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.

Abstract: An optical image pickup system for reducing spurious color signals generated in an image pickup system including a stripe-shaped color separation or color encoding filter, wherein a double refraction plate and a diffraction grating spatial frequency filter are arranged serially in an optical path to maintain a high resolution power in the luminance band and at the same time present a sufficient reduction of the spurious color signal.

Abstract: A two dimensional optical phase grating filter is provided that is capable of limiting the transmittance of spacial frequency signals in one or more scan directions. The two dimensional grating of the present invention can be utilized as an optical low pass filter to improve image resolution in a color video system. In the color video system, the two dimensional grating filter could be designed to optically complement a dichroic stripe filter to prevent the introduction of spurious signals by any interference of luminance and chrominance signals. The design parameters of the present invention provide an improved cut-off characteristic with grating widths larger than one-half of the filter period. The two dimensional phase grating filter of the present invention can also be utilized in other optical systems, such as an automatic focusing system, where it is desired to pass only a certain spacial frequency as a monitored signal for the automatic adjustment of the focus of the optical system.

Abstract: 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.

Abstract: A diaphragm device in which a plurality of diaphragm blades are arranged in partly overlapping relation to one another. This diaphragm device provides a diaphragm aperture of a substantially elongated circle having its length extending in a specific direction, when stopped down beyond a given diaphragm aperture. More particularly, the diaphragm aperture is defined by a pair of arcs which oppose each other in a direction perpendicular to the specific direction passing through the center of the aperture and another pair of arcs which are disposed on the opposite sides in the aforesaid specific direction, while the distance of either one of the pair of arcs to the center of the aperture is shorter than the distance of either of the other pair of arcs to the center of the aperture. These pairs of arcs define portions of the inner peripheral edges of the diaphragm blades.

Abstract: A double layered optical low pass filter is provided for use in a color video system for monitoring an object scene. The optical filter is designed to optically complement a dichroic stripe filter to prevent the introduction of spurious signals by any interference between luminance and chrominance signals, while at the same time providing a transmittance of high spatial frequency luminance signal to permit an improved image resolution. The optical low pass filter includes a first phase retarding filter layer designed to provide a first spatial frequency response across the visual spectrum and a second phase retarding filter layer designed to provide a second spatial frequency response across the visual spectrum.