Patent ID: 6995849
Filing Date: 2006-02-07
Classification: G01B

Abstract:
1. A displacement sensor comprising: a light-projection unit; a light-receiving unit having a light-shielding mask and a light-receiving element; a first light-converging arrangement which converges luminous fluxes released from said light-projection unit on a measuring object; a second light-converging arrangement which converges luminous fluxes reflected from said measuring object on said light-receiving unit; a first light-path control element which is placed in a projection-light path extending from said light-projection unit to said measuring object and in a receiving-light path extending from said measuring object to said light-receiving unit, and allows a projection-light light axis specified by said first light-converging arrangement and said light-projection unit and a receiving-light light axis specified by said second light converging arrangement and said light-receiving unit, to be coaxially arranged on the measuring object side of the first light-path control element; and a light-path length sweeping mechanism which is placed in a light path in which said projection-light light axis and said receiving-light light axis are set coaxially as well as at a position in which the luminous fluxes in said projection-light path and the luminous fluxes in said receiving-light path are set to be non-collimated, and which continuously changes a light-path length from the light-projection unit to the measuring object and a light-path length from the measuring object to the light-receiving unit, wherein: said light-shielding mask is placed in a light path from said second light-converging arrangement to said light-receiving element so that, when the position at which luminous fluxes reflected from said measuring object are converged by said second light-converging arrangement, is changed by said light-path length sweeping mechanism, the ratio at which one portion of the reflected luminous fluxes is light-shielded by said light-shielding mask is changed, said light-receiving element being allowed to receive luminous fluxes that have been transmitted through said light-shielding mask so that information with respect to a distance up to the measuring object is obtained based upon the output signal of the light-receiving element that is varied by the operation of said light-path length sweeping mechanism, and wherein the light-path length sweeping mechanism comprises: a reflection face that is placed perpendicularly to the light axis and allowed to shift along the light-axis direction that has been coaxially set; a second light-path control element which directs luminous fluxes released from said light-projection unit to said reflection face, directs luminous fluxes reflected from said reflection face to the measuring object, and also directs luminous fluxes reflected from the measuring object in the reversed direction along the same light path as the light path through which the luminous fluxes have been directed to said measuring object; a reflection-face-use light-projection unit which releases luminous fluxes to said reflection face in a direction other than the direction perpendicular to the reflection face; and a position detection element which receives luminous fluxes that are released from said reflection-face-use light-projection unit after having been reflected by said reflection face, and wherein information with respect to a distance up to the measuring object is obtained based upon an output sianal from said position-detection element and an output signal from said light-receiving unit.