PURPOSE: To provide high precision sine and cosine waves by continuously connecting No.1 and No.2 integrating circuits which emit sine and cosine wave, installing an inverting means to invert the output of No.2 circuit and give it to the No.1 circuit, and by performing feedback in which a specific computation is applied to the inverting means from the No.1 and No.2 circuits.

CONSTITUTION: No.1 and No.2 integrating circuits 21, 22 generate since and cosine waves and emit in the form of image drawing signals, and an inverting means 23 inverts the output signal of the No.2 integrating circuit 22 and gives it to the No.1 integrating circuit 21. A calculating means calculates square sum of the sine and cosine waves from the No.1 and No.2 integrating circuits, and the difference of the output signal or its root from the reference signal is calculated, and this difference is fed back to the inverting means 23. That is the circuitries 21W23 are additionally equipped with feedback circuits 24W26 in order to prevent the amplitude from becoming smaller by and by due to damping caused by transmission delay of signals and/or leak current of the integrating circuits 21, 22. Thereby a circle pattern with highly precise radius corresponding to the reference signal vref can be drawn with an electron microscope.