Abstract: We describe a capnometer for detecting a concentration of a component in a gas, wherein said gas is inhaled and/or exhaled by a patient, said capnometer comprising: an air flow region through which said gas passes to and/or from said patient's lung; a mid-IR semiconductor emitter configured to provide IR light at a wavelength in the range 3-5 ?m; a mid-IR semiconductor detector to detect said IR light; a reflector to reflect said IR light emitted by said emitter; wherein said emitter, said detector and said reflector are arranged such that said IR light emitted by said emitter passes through said air flow region via said reflector to said detector. The reflector is selected from a Fresnel reflector and a reflective diffractive optical element, such as.a Fresnel zone plate.

Abstract: An illumination apparatus for use in examining a body of living tissues, the apparatus comprising a head for contacting the body of living tissues, a light source mounted in the head for illuminating the tissues, and an annular switch disposed around the light source, the annular switch being adapted automatically to permit illumination of the light source at an examination intensity when the head contacts the body at least around an annular contact area on the head corresponding to the annular switch.