| 摘要 |
PURPOSE:To raise a read resolution of an optical scale by counting a 1/4 split pulse at the time of a high speed, executing an analog split by setting a square root of a square sum of a sine wave which is 90 deg. out-of-phase, as a reference voltage, and executing an interpolation, at the time of a low speed. CONSTITUTION:An out-of-phase interference light is photodetected from an optical scale which moves in accordance with a physical quantity, and a sine signal, and a cosine signal which is 90 deg. out-of-phase from said signal are outputted from amplifiers 21, 22, respectively, and converted to pulses by comparators 23, 24. These pulses are applied, a direction discriminator 25 generates a pulse of a resolution of 1/8 of a scale pitch whose synchronization to a moving direction signal is split to 1/4, and a high resolution pulse is counted by a counter 26, and outputted as it is at the time of moving at a high speed. On the other hand, at the time of a low speed, a signal having a good sensitivity of sine or cosine passing through a switching circuit 34 is brought to analog split by a distortionless DC reference voltage by a square root of a square sum of sine and cosine signals by square operators 27, 28, a square root circuit 33, etc., A/D-converted, and a counting value of the counter 26 is interpolated. According to them, a read resolution of an optical scale is raised. |
