Video/Audio Photon "Noise" Converters

In this area helpful hints and circuits will be given for interfaces to go between the optical receiver and a video or audio system. With these interfaces, the detected photons can be viewed as "snow" on a video monitor or heard through an audio system. These simple interfaces are good for keeping an "eye" and/or an "ear" on the arriving photon stream, independent of any computer monitoring of the signal.

To convert the narrow output pulses produced by a photon-counter discriminator into an audible signal, the short TTL or ECL logic pulses are stretched by means of a NE555/556 timer chip.

These circuits are temporary while this page is being designed.

The design for circuits to convert wideband PMT or APD signals into an audible signal will be given bellow.  Human hearing provides a pretty sensitive way to spot non-white signals within the white-noise "hiss".

The circuit below is as simple as it gets.  It is for use with analog wideband, direct-detection PMT and APD type optical receivers.  It cuts off frequencies in the quantum noise above the audio range to prevent high-frequencies entering the audio amplifiers.

Circuit 1: Passive low-pass filter for use with analog wideband PMT and APD optical receivers

The circuit below stretches the narrow pulses produced by photon-counters so that sufficient energy falls within the audio band.

Circuit 2: NE555 timer circuit for use with photon-counters

Circuit diagrams and simulations produce by:
Electronics Workbench V 5.1

See also ScreenCam Pulsed Beacon Demo