Analog-to-digital converter for seismic exploration using delta modulation

Claim 1

A seismic exploration system comprising: means for imparting seismic energy to the earth; means for detecting return of said seismic energy after reflection within the earth, said means for detecting comprising means for supplying an analog electronic signal as input to analog-to-digital converter means; analog-to-digital converter means for converting said input analog signal to a digital signal for convenience in signal transmission and storage, said analog-to-digital converter means comprising: means for generating a series of predicted analog signal values: means for comparing said series of predicted values to a series of instantaneous values of said input analog signal; means for outputtting a series of single digital bits each indicative of whether one of the predicted analog values is greater or lesser than the corresponding instantaneous value; means for updating said predicted value based on said series of digital bits; means for integrating said input analog signal prior to being supplied to said means for comparison; means for amplitude limiting the input analog signal prior to supply of said signal to said means for integrating said input analog signal; and low pass filter means and subsampling means connected to said means for outputting a series of digital bits for outputting a digital word representative of the instantaneous value of said analog input signal at selected sampling times, said series of single digital bits being applied to said integrator means prior to said low pass filter means and subsampling means.