Abstract: A measurement signal generating circuit for a linear scale capable of increasing an Signal-to-Noise (S/N) ratio, wherein S stands for Corona signal strength, and N for noise strength ratio of a signal for measurement of a linear scale. A photo detector or a low-pass filter for removing noise entering the measurement signal generating circuit is arranged rearwardly of each of an A phase signal generating circuit and a B phase signal generating circuit. Such construction permits a noise component at a different phase as well as that at the same phase to be effectively removed during synthesis of the measurement signal, to thereby reduce an error in measuring by the linear scale.

Abstract: A measurement signal generating circuit for a linear scale capable of increasing an S/N ratio of a signal for measurement of a linear scale. A photo detector or a low-pass filter for removing noise entering the measurement signal generating circuit is arranged rearwardly of each of an A phase signal generating circuit and a B phase signal generating circuit. Such construction permits a noise component at a different phase as well as that at the same phase to be effectively removed during synthesis of the measurement signal, to thereby reduce an error in measuring by the linear scale.

Abstract: An interpolation circuit for a measuring device capable of increasing a resolution and providing a velocity proportional output. Both sin .theta. signal and cos .theta. signal outputted from a sensor is fed to a balanced modulation adding circuit, resulting in providing a sin(.omega.t-.theta.) signal, which is then shaped into a pulse wave in a waveform shaping circuit. Then, a higher harmonic component is extracted by a BPF and then mixed with cos n.omega.t and sin n.omega.t signals in mixers, so that cos n.theta. and sin n.theta. signals are taken out of LPFs, respectively. The signals are subject to interpolation in a voltage comparison interpolation circuit of which the number of dividing is m, resulting in providing an interpolation circuit of which the whole number of dividing is m.multidot.n. Interpolation output A-phase and B-phase thereof each are a velocity proportional output.