Abstract: A droplet sensor includes an optical cover having a curved surface that forms a part of a spheroid, a protective film that covers the curved surface of the optical cover, a light source provided at a first focal point of an ellipse facing the curved surface, and a photodetector provided at a second focal point of the ellipse. The refractive index of the protective film is greater than the refractive index of a liquid to be detected. A sensing region is determined by a range of an incident angle at which a light beam emitted from the light source and incident onto the curved surface is totally reflected at the interface between the protective film and a gas, and is not totally reflected at the interface between the protective film and the liquid to be detected.

Abstract: A droplet sensor includes: an optical cover having an ellipsoid surface that is a portion of a spheroid; a light source disposed at or in proximity to a first focal point of the ellipsoid surface; and a light detector disposed at or in proximity to a second focal point of the ellipsoid surface, wherein the ellipsoid surface is an effective detection area configured to reflect light emitted from the light source toward the light detector, and an amount of light reflected by the effective detection area changes in accordance with adhesion of droplets on the ellipsoid surface, and wherein the optical cover has a curved surface that is tangentially connected to an outside of the effective detection area and having a curvature greater than a curvature of the ellipsoid surface.

Abstract: A droplet sensor includes an optical cover that forms part of a spheroid, a major axis of the spheroid being a vertical axis, a light emitting/receiving device disposed at a position offset from a first focal point of the spheroid along the major axis, and a reflector disposed in vicinity of a second focal point of the spheroid. The optical cover has an effective detection area between the light emitting/receiving device and the reflector. The effective detection area satisfies a total internal reflection condition at an interface with a gas, and does not satisfy the total internal reflection condition at an interface with a liquid. The reflector reflects, towards a light receiving surface of the light emitting/receiving device, light totally reflected by the effective detection area, or reflects, towards the effective detection area, light directly incident on the reflector from the light emitting/receiving device.

Abstract: A droplet sensor includes an optical cover having a curved surface that forms a part of a spheroid, a protective film that covers the curved surface of the optical cover, a light source provided at a first focal point of an ellipse facing the curved surface, and a photodetector provided at a second focal point of the ellipse. The refractive index of the protective film is greater than the refractive index of a liquid to be detected. A sensing region is determined by a range of an incident angle at which a light beam emitted from the light source and incident onto the curved surface is totally reflected at the interface between the protective film and a gas, and is not totally reflected at the interface between the protective film and the liquid to be detected.

Abstract: A droplet sensor includes an optical cover having an ellipsoid surface that is a portion of a spheroid, a light source disposed at or in proximity to a first focal point of the ellipsoid surface, and a light detector disposed at or in proximity to a second focal point of the ellipsoid surface. The ellipsoid surface includes an effective detection area configured to reflect light emitted by the light source toward the light detector, and an amount of light reflected by the effective detection area changes in accordance with adhesion of droplets on the ellipsoid surface. The optical cover includes a space having a hemispherical surface, the space being centered at the second focal point. The hemispherical surface includes a transmission scattering surface on a region that receives the light reflected by the effective detection area.

Abstract: A droplet sensor has an optical cover with a curved surface that forms a part of a spheroid, a light source positioned at a first focal point of an ellipse, the first focal point facing the curved surface, and a photodetector positioned at a second focal point of the ellipse. The ellipse has an eccentricity determined such that the curved surface has an effective detection area that satisfies conditions for total internal reflection at an interface with a gas and that does not satisfy the conditions for total internal reflection at an interface with a liquid.

Abstract: A droplet sensor has an optical cover with a curved surface that forms a part of a spheroid, a light source positioned at a first focal point of an ellipse, the first focal point facing the curved surface, and a photodetector positioned at a second focal point of the ellipse. The ellipse has an eccentricity determined such that the curved surface has an effective detection area that satisfies conditions for total internal reflection at an interface with a gas and that does not satisfy the conditions for total internal reflection at an interface with a liquid.

Abstract: A droplet sensor includes: an optical cover having an ellipsoid surface that is a portion of a spheroid; a light source disposed at or in proximity to a first focal point of the ellipsoid surface; and a light detector disposed at or in proximity to a second focal point of the ellipsoid surface, wherein the ellipsoid surface is an effective detection area configured to reflect light emitted from the light source toward the light detector, and an amount of light reflected by the effective detection area changes in accordance with adhesion of droplets on the ellipsoid surface, and wherein the optical cover has a curved surface that is tangentially connected to an outside of the effective detection area and having a curvature greater than a curvature of the ellipsoid surface.

Abstract: A droplet sensor includes an optical cover having an ellipsoid surface that is a portion of a spheroid, a light source disposed at or in proximity to a first focal point of the ellipsoid surface, and a light detector disposed at or in proximity to a second focal point of the ellipsoid surface. The ellipsoid surface includes an effective detection area configured to reflect light emitted by the light source toward the light detector, and an amount of light reflected by the effective detection area changes in accordance with adhesion of droplets on the ellipsoid surface. The optical cover includes a space having a hemispherical surface, the space being centered at the second focal point. The hemispherical surface includes a transmission scattering surface on a region that receives the light reflected by the effective detection area.

Abstract: A droplet sensor includes an optical cover having an elliptical surface forming a portion of a spheroid, a light source arranged at or in a vicinity of a first focal point of the elliptical surface, and a photodetector arranged at or in a vicinity of a second focal point of the elliptical surface. The elliptical surface includes an effective detection area configured to reflect light emitted from the light source towards the photodetector. An amount of light reflected from the effective detection area changes according to adhesion of a droplet on the effective detection area of the elliptical surface. The optical cover includes a hollow portion that is provided in a region inside the optical cover, and outside optical paths of the light emitted from the light source and reflected from the effective detection area toward the photodetector.

Abstract: A droplet sensor includes an optical cover having an elliptical surface forming a portion of a spheroid, a light source arranged at or in a vicinity of a first focal point of the elliptical surface, and a photodetector arranged at or in a vicinity of a second focal point of the elliptical surface. The elliptical surface includes an effective detection area configured to reflect light emitted from the light source towards the photodetector. An amount of light reflected from the effective detection area changes according to adhesion of a droplet on the effective detection area of the elliptical surface. The optical cover includes a hollow portion that is provided in a region inside the optical cover, and outside optical paths of the light emitted from the light source and reflected from the effective detection area toward the photodetector.

Abstract: A droplet sensor includes an optical cover that forms part of a spheroid, a major axis of the spheroid being a vertical axis, a light emitting/receiving device disposed at a position offset from a first focal point of the spheroid along the major axis, and a reflector disposed in vicinity of a second focal point of the spheroid. The optical cover has an effective detection area between the light emitting/receiving device and the reflector. The effective detection area satisfies a total internal reflection condition at an interface with a gas, and does not satisfy the total internal reflection condition at an interface with a liquid. The reflector reflects, towards a light receiving surface of the light emitting/receiving device, light totally reflected by the effective detection area, or reflects, towards the effective detection area, light directly incident on the reflector from the light emitting/receiving device.

Abstract: An optical disc apparatus, which executes tracking control for an objective lens by generating a push-pull signal, includes a determination unit which detects symmetry of the push-pull signal and determines whether balance of signal characteristics of the push-pull signal is good, a lens shift amount detection unit which detects, in a case where the determination unit determines that the balance of the signal characteristics of the push-pull signal is not good, a lens shift amount of the objective lens in such a manner as to improve the balance of the signal characteristics, a memory unit which stores the lens shift amount that is detected by the lens shift amount detection unit, and an addition unit which constantly applies the lens shift amount, which is stored in the memory unit, to a tracking actuator which shifts the objective lens.