Abstract: An image display apparatus mounted in a head up display apparatus includes: an image display element that outputs display light; a diffusing member that receives the display light at a light receiving surface and outputs the display light as diffused light from a light output surface; and a light deflecting means that deflects the display light output from the image display element, provided between the image display element and the diffusing member. An image display surface of the image display element and the light output surface of the diffusing member are parallel, and the image display element, the diffusing member, and the light deflecting means are arranged in a state such that a line normal to the light output surface of the diffusing member is inclined with respect to the optical axis of the display light after being deflected by the light deflecting means.

Abstract: An optical signal-to-noise ratio (OSNR) measuring device includes a processor, wherein the processor executes a process. The process includes: converting an optical signal to an electrical signal; first acquiring a signal intensity from the electrical signal; second acquiring a noise intensity of a predetermined frequency band from the electrical signal; performing a digital conversion on the noise intensity; and computing an OSNR of the optical signal based on the signal intensity and the converted noise intensity. The predetermined frequency band is a frequency band including a folding noise that occurs when the digital conversion is performed.

Abstract: An objective lens for endoscopes includes, in order from the object side: a front group; an aperture stop; and a positive rear group. The front group includes, in order from the object side, a negative first lens, in which the absolute value of the radius of curvature of the surface toward the image side is less than that of the surface toward the object side, and at least one plane parallel plate. The rear group includes, in order from the object side, a positive second lens, and a cemented lens formed by a positive third lens and a negative fourth lens. The coupling surface of the cemented lens is convex toward the image side. Conditional Formulae (1) through (3) concerning the plane parallel plates within the front group, the focal length of the first lens, the radius of curvature of the coupling surface of the cemented lens, etc., are satisfied.

Abstract: An objective lens for endoscopes is constituted essentially by, in order from the object side: a negative first lens having a concave surface toward the image side; a first cemented lens, formed by cementing a second lens and a third lens having refractive powers with signs opposite each other, provided in this order from the object side, together; a stop; a positive fourth lens having a convex surface toward the image side; and a second cemented lens, formed by cementing a positive fifth lens and a negative sixth lens, provided in this order from the object side, together, in which the coupling surface is convex toward the image side. Focusing from an object at a most distant point to an object at a most proximal point is performed by moving only the second cemented lens. A predetermined conditional formula is satisfied.

Abstract: An endoscope objective lens consists essentially of, in order from the object side, a negative first lens group, a stop, and a positive second lens group. At least one of the first lens group and the second lens includes only one cemented lens which is formed by a positive lens and a negative lens cemented together. The entire system includes a positive single lens. The endoscope objective lens satisfies given condition expressions relating to the focal length of the entire system, the center thickness of the positive single lens, the center thickness of the cemented lens, the distance from the most object-side lens surface to the stop, and the distance from the stop to the most image-side lens surface.

Abstract: Disclosed is a head-up display capable of achieving reduction in size while securing an optical path length from an image display element to an image reflecting surface. In a head-up display, a reflection optical system has at least three or more mirrors including an l-th mirror, an m-th mirror, and an n-th mirror sequentially in this order from the image display element side along a light beam emitted from the image display element D, the n-th mirror has a refractive power and is arranged closest to the image reflecting surface side among all mirrors, the light beam emitted from the image display element D is reflected from the l-th mirror, the m-th mirror, and the n-th mirror in this order, the light beam emitted from the n-th mirror passes between the l-th mirror and the m-th mirror and reaches the image reflecting surface, and predetermined conditional expressions are further satisfied.

Abstract: An objective lens for endoscopes includes, in order from the object side: a front group; an aperture stop; and a positive rear group. The front group includes, in order from the object side, a negative first lens, in which the absolute value of the radius of curvature of the surface toward the image side is less than that of the surface toward the object side, and at least one plane parallel plate. The rear group includes, in order from the object side, a positive second lens, and a cemented lens formed by a positive third lens and a negative fourth lens. The coupling surface of the cemented lens is convex toward the image side. Conditional Formulae (1) through (3) concerning the plane parallel plates within the front group, the focal length of the first lens, the radius of curvature of the coupling surface of the cemented lens, etc., are satisfied.

Abstract: The objective lens for an endoscope substantially consists of a first lens group having a negative refractive power, a stop, and a second lens group having a positive refractive power in this order from the object side. The first lens group consists of a single negative lens. The second lens group consists of two or fewer lenses. When the focal length of the first lens group is f1 and the focal length of the entire system is f, conditional expression (1): ?0.9<f1/f<0 is satisfied.

Abstract: An endoscopic objective lens consists of a negative first lens group, a stop, and a positive second lens group, disposed in order from the object side. The first lens group is composed of a cemented lens formed of a first lens and a second lens with a concave surface on the image side cemented in order from the object side. The second lens group is composed of a positive single third lens and a cemented lens formed of a fourth lens and a fifth lens, either of which being a positive lens and the other being a negative lens, and having a positive refractive power, disposed in order from the object side. The endoscopic objective lens satisfies given conditional expressions related to Abbe numbers of the first and second lenses and radii of curvature of the image side and object side surfaces of the second lens.

Abstract: An objective lens for endoscopes is constituted essentially by, in order from the object side: a negative first lens having a concave surface toward the image side; a first cemented lens, formed by cementing a second lens and a third lens having refractive powers with signs opposite each other, provided in this order from the object side, together; a stop; a positive fourth lens having a convex surface toward the image side; and a second cemented lens, formed by cementing a positive fifth lens and a negative sixth lens, provided in this order from the object side, together, in which the coupling surface is convex toward the image side. Focusing from an object at a most distant point to an object at a most proximal point is performed by moving only the second cemented lens. A predetermined conditional formula is satisfied.

Abstract: An endoscope objective lens consists essentially of, in order from the object side, a negative first lens group, a stop, and a positive second lens group. At least one of the first lens group and the second lens includes only one cemented lens which is formed by a positive lens and a negative lens cemented together. The entire system includes a positive single lens. The endoscope objective lens satisfies given condition expressions relating to the focal length of the entire system, the center thickness of the positive single lens, the center thickness of the cemented lens, the distance from the most object-side lens surface to the stop, and the distance from the stop to the most image-side lens surface.

Abstract: The imaging lens substantially consists of a negative first lens group in which a biconvex lens, a cemented lens, a plurality of lenses including a positive lens and a negative lens are arranged; a positive second lens group including a cemented lens; a negative third lens group in which a single lens forming a meniscus lens with a convex surface toward the object side or a plurality of lenses constituted in such a manner that the absolute value of the radius of curvature of a lens surface disposed on the most image side is smaller than the absolute value of the radius of curvature of a lens surface disposed on the most object side; and a positive fourth lens group including a positive lens in this order from the object side. This imaging lens is configured in such a manner that conditional expression (1) is satisfied: 0.7<|f3|/f<4.0.

Abstract: An objective optical system includes: a negative first lens group; an aperture stop; and a positive second lens group, provided in this order from an object side. The first lens group includes a first lens, which is a negative single lens, and a cemented lens formed by cementing a positive lens and a negative lens together, provided in this order from the object side. The second lens group includes a fourth lens, which is a positive single lens, and a cemented lens formed by cementing a positive lens and a negative lens together, provided in this order from the object side. The objective optical system satisfies Conditional Formula (1): f1/f<1.1, wherein f1 is the focal length of the lens provided most toward the object side, and f is the focal length of the entire lens system.

Abstract: An endoscopic objective lens consists of a negative first lens group, a stop, and a positive second lens group, disposed in order from the object side. The first lens group is composed of a cemented lens formed of a first lens and a second lens with a concave surface on the image side cemented in order from the object side. The second lens group is composed of a positive single third lens and a cemented lens formed of a fourth lens and a fifth lens, either of which being a positive lens and the other being a negative lens, and having a positive refractive power, disposed in order from the object side. The endoscopic objective lens satisfies given conditional expressions related to Abbe numbers of the first and second lenses and radii of curvature of the image side and object side surfaces of the second lens.

Abstract: An optical level control apparatus includes an input port, an output port, an optical device to assume a state of outputting light inputted to the input port from the output port and a state of not outputting the light inputted to the input port from the output port; a detector to detect an intensity of the light inputted to the input port, and a control unit to detect an input of an optical burst signal to the input port on the basis of a result of detecting the intensity of the light and to control the optical device so that the signal, in which to eliminate a field extending up to an elapse of a period of first time equal to or shorter than laser ON time period of the signal from a head of the signal with its input being detected, is output from the output port.

Abstract: An optical amplification apparatus includes a front-stage semiconductor optical amplifier which amplifies an input light and a rear-stage semiconductor optical amplifier which amplifies an amplified light outputted from the front-stage semiconductor optical amplifier. The front-stage semiconductor optical amplifier exercises auto level control of an output light by exercising variable control of driving current which flows according to applied voltage higher than light emitting threshold voltage of an internal optical amplification element. The rear-stage semiconductor optical amplifier performs gate switching of a transmitted light by exercising switching control of driving current. By doing so, distortion of a waveform is controlled and optical communication quality can be improved.

Abstract: The objective lens for an endoscope substantially consists of a first lens group having a negative refractive power, a stop, and a second lens group having a positive refractive power in this order from the object side. The first lens group consists of a single negative lens. The second lens group consists of two or fewer lenses. When the focal length of the first lens group is f1 and the focal length of the entire system is f, conditional expression (1): ?0.9<f1/f<0 is satisfied.

Abstract: A level control circuit that generates output signal for level control includes: a control information storage that stores control information corresponding to a signal level, a control information circuit that outputs the output signal for level control corresponding to the signal level of a first input signal based on the control information stored in the control information storage; and an information update circuit that updates the control information of the control information storage according to the signal level of a second input signal.

Abstract: An objective optical system includes: a first lens group having a negative power; an aperture stop; and a second lens group having a positive power, provided in this order from an object side. The first lens group includes a first lens, which is a negative single lens, and a cemented lens formed by a positive lens and a negative lens, provided in this order from the object side. The second lens group includes a fourth lens, which is a positive single lens, and a cemented lens formed by a positive lens and a negative lens, provided in this order from the object side. The objective optical system simultaneously satisfies Conditional Formulae (1) ?1.5<f123/f<?0.5 and (2) 1.8<f456/f<2.1, wherein f is the focal length of the entire system, f123 is the combined focal system of the first lens group, and f456 is the combined focal length of the second lens group.

Abstract: The angle of view of an objective optical system is widened, while suppressing generation of lateral chromatic aberration. An objective optical system includes: a first lens group having a negative power; an aperture stop; and a second lens group having a positive power, in this order from an object side. The first lens group includes a negative single first lens, and a cemented lens formed by cementing a positive lens and a negative lens together, provided in this order from the object side. The second lens group includes a positive single fourth lens, and a cemented lens formed by cementing a positive lens and a negative lens together, provided in this order from the object side. The objective optical system satisfies Conditional Formula (1): 15.0<?d(RN)<18.6, wherein ?d(RN) is the Abbe's number of the negative lens in the cemented lens within the second lens group with respect to the d line.