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Optical Analog to Digital Converter

IP.com Disclosure Number: IPCOM000088013D
Original Publication Date: 1977-Apr-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 3 page(s) / 51K

Publishing Venue

IBM

Related People

Callahan, RW: AUTHOR

Abstract

This analog-to-digital converter is capable of operating at very high speeds and is useful in a wide variety of applications. It provides one basic design which is easily adjusted to accommodate many different sampling rates and many different sizes of incremental amplitude changes It further includes a multiplexing feature for converting multiple analog signals in a concurrent manner.

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Optical Analog to Digital Converter

This analog-to-digital converter is capable of operating at very high speeds and is useful in a wide variety of applications. It provides one basic design which is easily adjusted to accommodate many different sampling rates and many different sizes of incremental amplitude changes It further includes a multiplexing feature for converting multiple analog signals in a concurrent manner.

The figure shows a representative embodiment of this novel converter Sensors A, B and C are sampled by means of gated AND circuits 10-13. This gating is controlled by a ring counter 14, which is driven by a variable frequency oscillator or clock 15. Control bus 16 enables the sampling rate to be dynamically varied. Sensor A represents a more critical sensor which must be sampled more frequently and, for this reason, is shown as being sampled by both AND circuit 10 and AND circuit 12.

The outputs of AND circuits 10-13 are connected to OR circuit 17 which drives a light-emitting transistor 18. The light output intensity of transistor 18 varies in a reasonably linear manner relative to the input signal level. The light output of the transistor 18 is uniformly distributed by means of an optical lens 19 over an array of light detectors represented by photo-sensitive diodes 21-27. Each of these light detector diodes 21-227is adjusted to sense a different calibrated intensity of light. The circuit of diode 21 is adjusted to detect the lowermost intensity, and the circuit of diode 27 is adjusted to detect the highermost intensity for the light intensity range of interest for the particular application at hand.

Amplifiers 31-37 are connected to the photodetector diodes 21-27, respectively. The outputs of the lower level amplifiers 31-36 are connected to the first inputs of AND circuits 41-46, respectively. Each of the second inputs of AND circuits 41-46 is connected, by way of one of the NOT circuits 51-56, respectively, to the output of the amplifier at the next higher level. This enables the output of each of amplifiers 32-37 to degate the output of the amplifier at the next lower level. For example, amplifier 37, if turned on by diode 27, will degate or block the output of the next lower amplifier...