Patent ID: 8422020
Filing Date: 2013-04-16
Classification: G01B,G01J

Abstract:
1. A variable spectroscopic element comprising: a pair of optical substrates arranged to face each other with a space between; first to fourth capacitive sensors each of which has a pair of electrodes arranged on mutually facing surfaces of the pair of optical substrates for detecting an intersurface distance between the mutually facing surfaces of the pair of optical substrates at each position where the pair of electrodes are arranged; and first to fourth actuators each of which moves at least one of the pair of optical substrates relative to the other optical substrate for changing the intersurface distance between the mutually facing surfaces of the pair of optical substrates; wherein the first capacitive sensor and the third capacitive sensor are arranged at positions that form symmetry with respect to an axis determined by a line that links respective gravity centers of the mutually facing surfaces of the pair of optical substrates; wherein the second capacitive sensor and the fourth capacitive sensor are arranged at positions that form symmetry with respect to the axis determined by the line that links the respective gravity centers of the mutually facing surfaces of the pair of optical substrates; wherein the first to fourth actuators are arranged, respectively, on lines that extend from the gravity centers of the mutually facing surfaces of the pair of optical substrates toward respective centers of the first to fourth capacitive sensors; and wherein the variable spectroscopic element is provided with a control section that calculates, from signals by the first to fourth capacitive sensors, a distance between the respective gravity centers of the mutually facing surfaces of the pair of optical substrates, calculates, from a signal by the first capacitive sensor and a signal by the third capacitive sensor, a first angle formed by a plane perpendicular to the line that links the respective gravity centers and one of the mutually facing surfaces of moving one of the optical substrates, calculates, from a signal by the second capacitive sensor and a signal by the fourth capacitive sensor, a second angle formed by a plane perpendicular to the line that links the respective gravity centers and the one of the mutually facing surface of the moving one of the optical substrates, drives the first actuator and the third actuator on a basis of the distance between the gravity centers and the first angle, drives the second actuator and the fourth actuator on a basis of the distance between the gravity centers and the second angle, carries out a feedback control with respect to the distance between the gravity centers, the first angle and the second angle, and carries out a feed forward control with respect to at least one of the distance between the gravity centers, the first angle and the second angle.