Patent ID: 7465916

Claim:
An optical detection sensor comprising: a light source, a first optical fiber guiding exit light emitted from the light source, a second and a third optical fiber receiving reflection light produced in such a way that the exit light is incident upon an object to be measured and thus reflected therefrom, the object being disposed a relative distance away from an end portion of the first optical fiber; a first and a second detection element receiving the reflection light that is guided through the second and the third optical fiber, thereby to convert the reflection light into an electric signal; and an arithmetic processing means computing a displacement quantity of the object to be measured on the basis of a ratio of the electric signals obtained through the conversion in the first and the second detection element; wherein the first optical fiber is disposed so that an angle between a longitudinal direction thereof and a normal line to an incident surface of the object to be measured becomes θ; wherein the second and the third optical fiber are disposed so as to be in parallel with each other and so that an angle between a longitudinal direction of the second and the third optical fiber and the normal line becomes θ; wherein the first optical fiber is disposed symmetrically with the second and the third optical fiber with respect to the normal line; and wherein the first to the third optical fiber have a dNA/dλ of 4×10 −5 or less with respect to a wavelength of the light source.