To detect an object accurately with low-intensity light.SOLUTION: An optical device includes: a light source unit which irradiates an object with light； a light-emission driving unit which drives the light source unit to emit light with a predetermined light-emitting period； a position detection unit which outputs detection signals in accordance with the light reflected from the object； and an extraction signal output unit which outputs extraction signals extracted from the detection signals, with a period corresponding to the light-emitting period, by use of reference signals with a period corresponding to the light-emitting period.SELECTED DRAWING: Figure 4【課題】光強度が小さい光で対象物を高精度に検出すること。【解決手段】開示の技術の一態様に係る光学装置は、対象物に光を照射する光源部と、前記光源部を所定の発光周期で発光駆動させる発光駆動部と、照射された光の前記対象物からの反射光に応じた検出信号を出力する位置検出部と、前記発光周期に対応する周期の参照信号を用いて、前記検出信号から抽出された前記発光周期に対応する周期の抽出信号を出力する抽出信号出力部と、を有する。【選択図】図４
