Optical force sensor and apparatus using optical force sensor

Patent metadata

Field	Value
Publication number	US-2015276518-A1
Application number	US-201514670645-A
Country	US
Kind code	A1
Filing date	Mar 27, 2015
Priority date	Apr 1, 2014
Publication date	Oct 1, 2015
Grant date	—

Abstract

The optical force sensor includes a base member, a displaceable member, an elastic member disposed between the base and displaceable members and a displacement detector optically detecting a displacement of the displaceable member caused by an external force. The displacement detector causes first and second light fluxes to form interference fringes on a first light-receiving element. The first light flux from a light source is internally reflected at a gap-side surface of a light-transmissive member. The second light flux from the light source is transmitted through the light-transmissive member, reflected by a reflective surface provided to the displaceable member and again transmitted through the light-transmissive member. The displacement detector outputs, from the first light-receiving element, a signal corresponding to a variation in intensity distribution of the interference fringes.

First claim

What is claimed is:

1 . An optical force sensor comprising:
a base member; a displaceable member, the displaceable member and the base member being mutually separated in a first direction; an elastic member disposed between the base member and the displaceable member; and a displacement detector configured to optically detect a displacement of the displaceable member with respect to the base member, the displacement being caused by an external force, wherein the displacement detector includes: a light source provided to one member of the base member and the displaceable member; a reflective surface provided to another member of the base member and the displaceable member; a light-transmissive member disposed between the light source and the reflective surface and having a gap with the reflective surface; and a first light-receiving element provided to the one member, and wherein the displacement detector is configured: (a) to cause a first light flux and a second light flux to form interference fringes on the first light-receiving element, the first light flux exiting from the light source and being internally reflected at a gap-side surface of the light-transmissive member, the second light flux exiting from the light source, being transmitted through the light-transmissive member, being reflected by the reflective surface and being again transmitted through the light-transmissive member; and (b) to output an output signal based on a variation of a first signal output from the first light-receiving element configured to detect an intensity distribution of the interference fringes, the variation being caused by a displacement of the displaceable member in the first direction.

2 . An optical force sensor according to claim 1 , further comprising a first calculator configured to calculate an external force acting in the first direction by using the output from the first light-receiving element.

3 . An optical force sensor according to claim 1 ,
wherein the displacement detector includes: a diffraction grating provided to the one member; and a second light-receiving element provided to the other member, and wherein the displacement detector is configured: (a) to cause a third light flux to form an optical image on the second light-receiving element, the third light flux exiting from the light source, being transmitted through the light-transmissive member, being reflected by the diffraction grating and being again transmitted through the light-transmissive member; and (b) to output, from the second light-receiving element, a signal corresponding to a displacement of the optical image, the displacement of the optical image being caused by a displacement of the displaceable member in a second direction orthogonal to the first direction and parallel to a light-receiving surface of the second light-receiving element.

4 . An optical force sensor according to claim 3 , wherein the second light-receiving element is disposed at a position where the second light flux hits the gap-side surface of the light-transmissive member at an incident angle larger than a critical angle, is internally reflected at the gap-side surface and then enters the second light-receiving element.

5 . An optical force sensor according to claim 3 , further comprising a second calculator configured to calculate an external force acting in the second direction by using the output from the second light-receiving element.

6 . An optical force sensor according to claim 5 , wherein the second calculator is configured to correct, by using the output from the first light-receiving element, its calculation result calculated using the output from the second light-receiving element.

7 . An optical force sensor according to claim 1 , wherein the light source is a current confinement structure LED.

8 . An optical force sensor according to claim 1 , wherein the light source and the first light-receiving element are mounted on a same substrate.

9 . An optical force sensor according to claim 3 , wherein the first and second light-receiving elements are included in a two-dimensional image sensor.

10 . An apparatus comprising:
a movable portion configured to perform an operation; an optical force sensor; and a controller configured to control the operation of the movable portion by using the optical force sensor, wherein: the optical force sensor comprises: a base member; a displaceable member configured to move integrally with the movable portion, the displaceable member and the base member being mutually separated in a first direction; an elastic member disposed between the base member and the displaceable member; and a displacement detector configured to optically detect a displacement of the displaceable member with respect to the base member, the displacement being caused by an external force, and the displacement detector includes: a light source provided to one member of the base member and the displaceable member; a reflective surface provided to another member of the base member and the displaceable member; a light-transmissive member disposed between the light source and the reflective surface and having a gap with the reflective surface; and a first light-receiving element provided to the one member, and wherein the displacement detector is configured: (a) to cause a first light flux and a second light flux to form interference fringes on the first light-receiving element, the first light flux exiting from the light source and being internally reflected at a gap-side surface of the light-transmissive member, the second light flux exiting from the light source, being transmitted through the light-transmissive member, being reflected by the reflective surface and being again transmitted through the light-transmissive member; and (b) to output an output signal based on a variation of a first signal output from the first light-receiving element configured to detect an intensity distribution of the interference fringes, the variation being caused by a displacement of the displaceable member in the first direction.

Assignees

• Canon Kk

Inventors

• Nagura Chihiro

Classifications

• G01L1/242 Primary

  the material being an optical fibre · CPC title

• G01B11/14 Primary

  for measuring distance or clearance between spaced objects or spaced apertures (G01B11/26 takes precedence; rangefinders G01C3/00) · CPC title

• G01L7/086

  with optical transmitting or indicating means · CPC title

• G01B11/161

  by interferometric means · CPC title

• G01L1/005

  by electrical means and not provided for in G01L1/06 - G01L1/22 · CPC title