| 摘要 |
In the variable spectroscopic element, the first sensor 3 1 and the third sensor 3 3 are arranged at positions that form symmetry with respect to the axis that links gravity centers of mutually facing surfaces of the pair of optical substrates 2, and so are the second sensor 3 2 and the fourth sensor 3 4 ; the first to fourth piezoelectric elements 4 1 to 4 4 are arranged, respectively, on lines that extend from the gravity centers of the mutually facing surfaces of the pair of optical substrates 2 toward respective centers of the first to fourth sensors 3 1 to 3 4 ; and a control section is provided to calculate, from signals by the first to fourth sensors 3 1 to 3 4 , a distance x between the gravity centers of the mutually facing surfaces of the pair of optical substrates, to calculate, from a signal by the first sensor 3 1 and a signal by the third sensor 3 3 , a first angle ¸ formed by a plane perpendicular to the line that links the gravity centers and one of the mutually facing surfaces of moving one of the optical substrates, to calculate, from a signal by the second sensor 3 2 and a signal by the fourth sensor 3 4 , a second angle Æ formed by a plane perpendicular to the line that links the gravity centers and the one of the mutually facing surface of the moving one of the optical substrates, to drive the first to fourth piezoelectric elements 4 1 to 4 4 on the basis of the distance x , the angle ¸ and the angle Æ , and to carry out feedback control and feed forward control with respect to at least one of the distance x , the angle ¸ and the angle Æ . |
