Apparatus to register the quantity of sebum secreted by a skin

Claim 1

Apparatus for registering the quantity of sebum secreted from a region of the skin of a living subject onto a translucent element comprising, a luminous flux emitter for directing luminous flux through a translucent element disposed in front of a reflecting surface, the translucent element being a plate having a ground surface, a receiver on the same side of the translucent element as said flux emitter for receiving the luminous flux transmitted and reflected through the translucent element by virtue of the transparency of said element, said flux emitter being modulated at a fixed frequency, and said receiver only measuring the flux received which has the frequency of modulation of the emitter, the emitter of the luminous flux comprising an electroluminescent diode, and the luminous flux receiver comprising a phototransistor, storage means for storing the value of an output voltage from the receiver resulting from a measurement of a reference specimen, said storage means comprising a digital storage unit having a register and an analog output, means for subtracting said stored value of voltage from a later output voltage of the receiver resulting from a measurement of a translucent element having sebum deposited thereon, and means for registering the value of the difference between said voltages, the storage unit including a double analog/digital and digital/analog converter with binary memory, which has an input for receiving a measuring voltage and an output for producing a reference voltage corresponding to its stored binary value, and manually operable means to reset said storage unit and to enable said unit to store a binary value corresponding to a new measuring voltage received.