| 摘要 |
PURPOSE:To obtain fixed stylus force by detecting the sensitivity of a cantilever every time stylus force is applied, estimating the magnitude of magnetic field necessary to obtain prescribed stylus force, and controlling the amount of current of a stylus force coil so as to obtain the estimated magnitude of magnetic field. CONSTITUTION:A low pass filter 15 connected to the output of a D-A converter 14 consists of an integrating circuit. DC voltage corresponding to a digital numerical value is applied to transistors 1, 5 by count up down command signals c, d, and a magnetic field corresponding to the DC voltage value is applied to a magnet 9. An arithmetic unit 18 outputs a count up command signal (c) when stylus force is to be increased, and outputs a count down signal (d) when decreasing stylus force. Accordingly, when the stylus is at a point (a), the count down command signal (d) is inputted to make the value of an internal digital signal zero. When the stylus 11 is brought to a point (b) by the count up command signal (c), a signal (f) goes to high level, and a value to be outputted next is calculated from the value of the count up command signal (c) and stylus force coefficient data (g) corresponding to the value, and outputted. Accordingly, practically usable nearly accurate stylus force value can be obtained even when many conditions are superposed. |
