An S / N ratio of a signal output from a detector is improved.SOLUTION: The detector (100a) comprises a substrate (10), a light emitting part (20) disposed on the substrate and emitting light, a light emitting part (20) disposed on the substrate, and disposed from the object of the emitted light A light receiving portion (31) for receiving the scattered light of the light emitting portion and a sealing portion (40) arranged on the substrate so as to cover the light emitting portion and the light receiving portion. The light receiving portion further receives internally reflected light reflected at the interface of the sealing portion of the light emitted from the light emitting portion. A reflecting film (41) is disposed on at least a part of the surface of the sealing portion.(FIG.【課題】検出器から出力される信号のS/N比を向上させる。【解決手段】検出器(100a)は、基板(10)と、該基板上に配置され、光を出射する発光部(20)と、該基板上に配置され、出射された光の対象物からの散乱光を受光する受光部(31)と、該発光部及び該受光部を覆うように、基板上に配置された封止部(40)と、を備える。受光部は、発光部から出射された光の封止部の界面で反射された内部反射光を更に受光する。封止部の表面の少なくとも一部に反射膜(41)が配置されている。【選択図】図5
