Optical sensor

Abstract

An optical sensor includes a light source, a sensing unit, a first optical fiber transmitting light from the light source to the sensing unit, second and third optical fibers transmitting the light from a reflecting surface of the sensing unit to light-receiving portions, and a calculation unit calculating physical quantities from electrical signals from the light-receiving portions. End surfaces of these fibers opposed to the reflecting surface are fixed so that the longitudinal direction thereof and the normal line of the reflecting surface form an angle θ, the second and third optical fibers are parallel to each other, and the fixing angles of the first optical fiber and the second and third optical fibers are symmetric about the normal line. These optical fibers have a single mode in the wavelength of which the optical fibers are used. A depolarizer is interposed between the light source and the first optical fiber.

1 . An optical sensor comprising:
 a light source;   a light-transmitting optical fiber transmitting light from the light source to an object;   two light-receiving optical fibers transmitting the light reflected from a reflecting surface of the object to two light-receiving portions; and   a calculation unit calculating physical quantities on the basis of a ratio of electrical signals from the light-receiving portions,   wherein three optical fibers opposed to the reflecting surface are fixed so that the longitudinal direction of the optical fibers and the normal line of the reflecting surface form an angle θ,   the light-receiving optical fibers are parallel to each other, the fixing angles of the light-transmitting optical fiber and the light-receiving optical fibers are symmetric about the normal line of the reflecting surface,   the optical fibers have a single mode in the wavelength of which the optical fibers are used, and   a taped portion in which the light-receiving fibers are coated in a bundle is provided.   
   
   
       2 . The optical sensor according to  claim 2 , wherein a taped portion in which the light-transmitting optical fiber and the light-receiving optical fibers are coated in a bundle is provided and the light-receiving optical fibers in the taped portion are adjacent to each other. 
   
   
       3 . The optical sensor according to  claim 2 , wherein a taped portion in which the light-transmitting optical fiber, the light-receiving optical fibers, and one or more dummy fibers are coated in a bundle is provided, the light-receiving optical fibers in the taped portion are fixed to be adjacent to each other, and the light-transmitting optical fiber or the one or more dummy optical fibers are disposed on both sides of the light-receiving optical fibers.