Apparatus for measuring at least one optical or physiological parameter in human tissue, comprising - at least one light source configured to emit at least one measurement wavelength within the NIR-range from 640 to 1350 nm, - at least one detector configured to detect said at least one measurement wavelength, and - an electronic unit configured - to measure a measurement light quantity resulting from an emission of said at least one measurement wavelength into said tissue, based on electrical signals read-out from said at least one detector , for computing said at least one parameter, and - to compute said at least one optical or physiological parameter from said measurement light quantity, - wherein said apparatus features an optical contact detector configured to detect a detection wavelength, which lies outside of the NIR-range from 640 to 1350 nm and is thus different from said at least one measurement wavelength, - wherein the at least one light source , the at least one detector and the optical contact detector are arranged on a contact area of the apparatus , in particular on a lower side of a bendable sensor head of the apparatus , and - wherein said contact area is configured to be brought into contact with a skin during a measurement, - wherein said electronic unit is configured to measure a detection light quantity based on electrical signals outputted by said optical contact detector and to detect a direct skin contact of the contact area based on the measured detection light quantity, characterized in that - said optical contact detector features an optical filter configured to transmit said detection wavelength and to block said at least one measurement wavelength. - at least one light source configured to emit at least one measurement wavelength within the NIR-range from 640 to 1350 nm, - at least one detector configured to detect said at least one measurement wavelength, and - an electronic unit configured - to measure a measurement light quantity resulting from an emission of said at least one measurement wavelength into said tissue, based on electrical signals read-out from said at least one detector , for computing said at least one parameter, and - to compute said at least one optical or physiological parameter from said measurement light quantity, - to measure a measurement light quantity resulting from an emission of said at least one measurement wavelength into said tissue, based on electrical signals read-out from said at least one detector , for computing said at least one parameter, and - to compute said at least one optical or physiological parameter from said measurement light quantity, - wherein said apparatus features an optical contact detector configured to detect a detection wavelength, which lies outside of the NIR-range from 640 to 1350 nm and is thus different from said at least one measurement wavelength, - wherein the at least one light source , the at least one detector and the optical contact detector are arranged on a contact area of the apparatus , in particular on a lower side of a bendable sensor head of the apparatus , and - wherein said contact area is configured to be brought into contact with a skin during a measurement, - wherein said electronic unit is configured to measure a detection light quantity based on electrical signals outputted by said optical contact detector and to detect a direct skin contact of the contact area based on the measured detection light quantity, - said optical contact detector features an optical filter configured to transmit said detection wavelength and to block said at least one measurement wavelength. <EOS>