Optical heart rate earphone

An optical heart rate earphone, comprising:

• a front housing having a case body, and a hollow barrel-shaped sound tube extended frontward from a front of the case body, at least one portion of the sound tube forming at least one light transmission gap penetrating a front edge of the sound tube;
• a circuit board assembly including a fastening element, a circuit board, a loudspeaker and at least one optical sensor, a middle of the fastening element opening a tuning hole penetrating therethrough along a front-to-rear direction, the circuit board including a fastening frame, an assembling portion, and a connecting portion connected between the fastening frame and the assembling portion, the fastening element being received in the fastening frame, the fastening element together with the fastening frame being assembled in the sound tube, the loudspeaker being assembled to the assembling portion of the circuit board and facing to the tuning hole, the at least one optical sensor being fastened to an outer surface of the fastening frame and corresponding to the at least one light transmission gap;
• a rear housing assembled to a rear end of the front housing;
• and
• a light pipe having a circular base, the base opening a sound hole corresponding to the tuning hole, at least one portion of a periphery of the base protruding rearward to form at least one transmittance slice corresponding to the at least one light transmission gap, the light pipe being assembled to the sound tube, the at least one transmittance slice being wedged in the at least one light transmission gap;
• wherein the light pipe and the sound tube are capable of being together inserted into an ear canal for measuring heart rates.