Method and apparatus for multiplexed oversampled analog to digital modulation

An imager responsive to an energy pattern incident on a focal plane for producing a bit stream representative thereof, said imager comprising:

• an array of energy sensitive elements disposed on said focal plane for producing m analog signals;
• M storage elements, each capable of storing an analog value;
• N bit A/D converter means, responsive to an applied analog value, for producing a bit stream output representative thereof;
• multiplexing means for periodically applying a residue analog value from each of said m storage elements to said A/D converter means, each residue analog value associated with a different one of said m analog signals;
• N bit D/A converter means, responsive to said A/D converter means bit stream output, for producing quantized values each coarsely representative of a residue analog value applied to said A/D converter means;
• means for summing each of said m analog signals and its associated residue analog value and differencing the quantized value associated therewith to form a new residue analog value;
• and
• demultiplexing means for storing each new residue analog value in one of said m storage elements.

An imager responsive to an energy pattern incident on a focal plane for producing an output bit stream representative of said pattern, said imager comprising:

• an array of m energy collection elements, each capable of producing an analog signal related to the amount of energy incident thereon;
• means mounting each of said m energy collection elements for collecting energy from a different area of said focal plane;
• means for storing m analog residues, each associated with a different one of said collection elements;
• A/D converter means sequentially responsive to said m analog residues for producing an output stream comprised of bits, each related to one of said analog residues;
• D/A converter means responsive to said output stream bits for respectively producing analog quantized estimates, each related to one of said analog residues;
• and
• processing means for periodically modifying the stored value of each analog residue as a function of the analog signal produced by the associated collection element and the analog quantized estimate produced by said D/A converter means.

A method for producing a bit stream output representative of an array of m analog inputs, said method comprising the steps of:

• providing m storage elements, each capable of storing an analog value;
• providing an N bit A/D converter, responsive to an applied analog value, for producing a bit stream output representative thereof;
• applying, periodically, a residue analog value from each of said m storage elements to said A/D converter means, each residue analog value associated with a different one of said m analog inputs;
• providing an N bit D/A converter, responsive to said A/D converter bit stream output, for producing quantized values each coarsely representative of a residue analog value applied to said A/D converter;
• summing each of said m analog inputs and its associated residue analog value and differencing the quantized value associated therewith to form a new residue analog value;
• and
• storing each new residue analog value in one of said m storage elements.

A method for producing an output bit stream representative of an energy pattern incident on a focal plane, comprising the steps of:

• providing an array of m energy collection elements, each capable of producing an analog signal related to the amount of energy incident thereon;
• mounting each of said m energy collection elements for collecting energy from a different area of said focal plane;
• storing m analog residues, each associated with a different one of said collection elements;
• performing analog-to-digital conversion sequentially of said m analog residues to produce an output stream comprised of bits, each related to one of said analog residues;
• performing digital-to-analog conversion of said output stream bits to respectively produce analog quantized estimates, each related to one of said analog residues;
• and
• modifying, periodically, the stored value of each analog residue as a function of the analog signal produced by the associated collection element and the analog quantized estimate produced by said digital-to-analog conversion.

A method for producing a bit stream output representative of an energy pattern incident on a focal plane, comprising the steps of:

• disposing an array of energy sensitive elements on said focal plane for producing m analog signals;
• providing m storage elements, each capable of storing an analog value;
• providing an N bit A/D converter, responsive to an applied analog value, for producing a bit stream output representative thereof;
• applying, periodically, a residue analog value from each of said m storage elements to said A/D converter means, each residue analog value associated with a different one of said m analog signals;
• providing an N bit D/A converter, responsive to said A/D converter bit stream output, for producing quantized values each coarsely representative of a residue analog value applied to said A/D converter;
• summing each of said m analog signals and its associated residue analog value and differencing the quantized value associated therewith to form a new residue analog value;
• and
• storing each new residue analog value in one of said m storage elements.