US 5,293,042 AGranted

Servo circuit of scanning probe microscope

AssigneeOlympus Optical Co., Ltd.

InventorHirofumi Miyamoto

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Abstract

An integrator for integrating a deviation signal and generating an integral control signal includes an operational amplifier for receiving a deviation signal through a first resistor, a capacitor connected between an inverting input terminal and an output terminal of the operational amplifier, and a series circuit constituted of a diode and a second resistor connected in parallel to the first resistor. If a probe and a sample approach each other and the deviation signal becomes is 0.7 V or more, charges are accumulated in the capacitor through the diode and second resistor as well as the first resistor. Thus, the voltage of the integral control signal is suddenly changed to the negative to separate the probe and sample from each other. If the probe and sample are separated from each other, the deviation signal becomes negative, and the charges are removed from the capacitor through the first resistor. The voltage of the integral control signal is thus changed to the positive to allow the probe and sample to approach each other. Since the diode prevents the charges from being removed through the second resistor, the change of the integral control signal to the positive is gentler than that of the integral control signal to the negative.

Claims23

Dependent claims

A servo circuit of a scanning probe microscope for outputting a three-dimensional image in response to a scanning output signal generated when a probe relatively scans a surface of a sample in a direction parallel thereto, said servo circuit keeping a distance between the probe and the sample constant when the probe scans the surface of the sample, and comprising:

moving means for relatively moving the probe in a direction perpendicular to the surface of the sample;
deviation detecting means for detecting a deviation from a reference value of the scanning output signal and generating a deviation signal;
control means for:
receiving the deviation signal from said deviation detecting means,
generating a drive signal corresponding to the deviation signal and possessing a predetermined response characteristic to the deviation signal, and
supplying the drive signal to said moving means, thereby moving the probe;
and
servo characteristic changing means for:
receiving the deviation signal from said deviation detecting means,
detecting an excess of a value of the deviation signal over a predetermined value, and
changing the predetermined response characteristic to the deviation signal, possessed by the drive signal generated from said control means, in response to the excess being detected, to a faster response characteristic.

8 more elements

Dependencies are inferred from the claim text.