To detect evenness of a contact state of a probe tip face with a biological surface, and thereby improve measurement accuracy arising from unevenness of the contact state.SOLUTION: A light projecting/receiving system 10 is an optical biological information measurement-purpose light projecting/receiving system that comprises, on a tip surface (AS) abutted on a biological body surface (BS) at the time of measuring, a light emission unit (2q) emitting measurement light (LW) to a biological body (9) and a light reception unit (3pB) receiving the measurement light returned from the biological body, and measures information on the biological body on the basis of light detection via the light reception unit. The light reception unit and/or the light emission unit are/is provided with a plurality of independent systems, and light reception units (p1, p2 and p3) of the mutually different systems and/or the light emission unit thereof have/has different distribution in accordance with an angle centering around a center axis of the light emission unit in a case of the light reception unit, and different distribution in accordance with an angle centering the center axis of the light reception unit in a case of the light emission unit. Evenness of a contact state of the tip surface with the biological body surface is detectable on the basis of a light detection value of each of the plurality of systems.SELECTED DRAWING: Figure 2【課題】プローブ先端面の生体面への接触状態の均一性を検知し、それにより、接触状態の不均一に起因する測定精度の悪化を改善する。【解決手段】投受光系１０は、生体（９）へ測定光（ＬＷ）を出射する出射する発光部（２ｑ）と、生体から戻ってきた測定光を受光する受光部（３ｐＢ）とを、測定時に生体面（ＢＳ）に当接される先端面（ＡＳ）に備え、受光部を介した光検出に基づき生体の情報を測定する光学的生体情報測定用の投受光系である。受光部又は／及び発光部は、独立した複数系統が設けられ、互いに異なる系統の受光部（ｐ１、ｐ２、ｐ３）又は／及び発光部は、受光部であれば発光部の中心軸回りの角度に応じた分布、発光部であれば受光部の中心軸回りの角度に応じた分布が異なる。複数系統によるそれぞれの光検出値に基づき、先端面の生体面への接触状態の均一性を検知可能にする。【選択図】図２
