| 摘要 |
PROBLEM TO BE SOLVED: To provide a displacement detector which can accurately detect the displacement of a cantilever even when measurements are taken over a long time or in such an environment as may change readily. SOLUTION: A sample S is placed on a piezoelectric actuator 13 provided on a base 10. A cantilever 11 is secured to the base 10 at one end and has a probe 12 at the other end. A semiconductor laser 15 which repeats turning on and off and a condensing lens 16 which collects measuring light onto the cantilever 11 are placed above the cantilever 11. The two receiving parts 17a, 17b of a two-piece photodetector 17, when the measuring light impinges on them, output currents Isa, Isb which are almost proportional to the measuring light, and when the measuring light does not impinge on them, output currents Ina, Inb proportional to noises are output. A noise eliminator circuit 18 performs the computations of Ia=Isa-Ina and Ib=Isb-Inb, and a differential circuit 19 converts the currents Ia, Ib into voltages Va, Vb and performs the computation ofΔZ=Va-Vb.
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