| 摘要 |
Detection circuitry is described in which the range and signal to noise ratios are improved. The circuitry includes a plurality of light emitting diodes (12, 14, 16, 18) connected in series and a plurality of photodiodes (22, 24, 26, 28). Each photodiode (22) has its own separate detection circuit (42, 62) which is AC decoupled by capacitors (52). Summing means (70) are connected to sum the outputs of the detection circuits and the resultant signal is fed to an output device (10). The magnitude of the output signal is increased by a factor equal to the product of the number of light emitting diodes (12, 14, 16, 18) and the number of photodiodes (22, 24, 26, 28), over the situation where only one diode of each type is used. |
