Extended correlated double sampling for charge transfer devices

A system for correcting for threshold and leaking current non-uniformities in a charge transfer device having a plurality of successive stages through which a charge packet representative of an input voltage sample is propagated at a prescribed shift cycle rate, comprising:

• means for supplying selectively a reference level sample and at least one associated input signal sample, in succession and at the rate of said shift cycle,
• means responsive to said successively supplied reference level and input signal samples for injecting corresponding charge packets into a stage of said charge transfer device, each such charge packet injection occurring during an injection interval of said shift cycle of said device,
• means for propagating said charge packets corresponding to said reference level and signal samples through successive stages of said device at said shift cycle rate of said device,
• means associated with a successive stage displaced from said at least one injection input stage of said device for sampling the potential at said associated successive stage occurring as a result of propagation of each such charge packet through said associated successive stage, to produce an output sample in successive said shift cycles corresponding to said reference level sample and to said at least one input signal sample,
• means selectively responsive to said output samples, in timed relation to propagation of reference level and signal charge packets through said associated successive stage, for storing a value indicative of the reference level output sample, and for determining the difference between the stored reference level value and the value of the successive, said signal output sample, and providing the resulting difference value, for each said output signal sample, as the output signal of said device, corrected for non-uniformities of thresholds and leakage currents and for bias errors of the above said means.

A signal enhancement system employing a charge transfer device having a succession of stages, plural charge injector means associated with alternate ones of said succession of stages for injection of charge packets thereinto, means for advancing charge packets through said successive stages at a predetermined rate, and means for sampling a serial output from the last of the successive stages at said rate, comprising:

• selective sampling and supply means including:
• means for providing an input signal to be enhanced,
• means for providing a reference level,
• means for selecting a sample of said reference level and a sample of said signal to be enhanced in an alternating sequence, at said rate, and supplying said signal and reference level samples in said prescribed sequence in successive shift cycle intervals to the first and each successive charge injector associated with said charge transfer device, whereby the charge packets in the prescribed sequence and corresponding to said signal and reference level samples progress as a related pair through said successive stages of said charge transfer device, each thereof receiving additively a charge packet injection at each said successive injector of the corresponding said signal and reference level samples,
• said output means sampling the voltage level induced by said summed charge packets and producing corresponding summed output samples in the said prescribed sequence representing respectively the summation values of the signal and reference level samples for each said related pair of samples of said signal to be enhanced and said reference level, at the said rate, and
• analog circuit means for storing a value corresponding to the said reference level summed output sample and comparing said stored value with the input signal summed output sample of the said related pair of input signal and reference level samples, to determine the difference therebetween, and supplying the said difference as the output signal of said charge transfer device, said output signal being enhanced in amplitude relative to said input signal.

A system for correction of errors in the output signals from a charge transfer device having a plurality of successive stages through which charge packets respectively corresponding to analog signal samples injected into said device are propagated at a preselected shift cycle rate, and including a serial input charge injector and plural parallel output sampling circuits associated with respectively corresponding, plural stages of said charge transfer device, each sampling a potential in its associated stage within a given said shift cycle corresponding to the charge packet then propagating through said stage, comprising:

• a source of an input signal and of a reference level signal,
• means for selectively and sequentially sampling said reference level and input signals in a prescribed sequence and at said shift cycle rate,
• means responsive to said sequence of reference and signal samples for injecting corresponding charge packets into said charge transfer device at at least a preselected input stage thereof and during at least preselected ones of said shift cycles,
• each of said sampling means being operable at said shift cycle rate and during at least a sequence of said shift cycles in which charge packets corresponding to a given prescribed sequence of reference level and input signal samples are propagated through said associated stage, to produce output samples indicative of the output potential of said stage induced by propagation of the said corresponding sequence of charge packets propagating therethrough and corresponding to said reference level and signal samples of said given, prescribed sequence,
• analog circuit means for selectively responding to the reference and signal output samples of said prescribed sequence for determining the difference in value of each said output signal sample relative to said reference level sample of said sequence, and producing an output signal indicative of that difference as the output signal from the said sampling means.

A system for correction of errors in the output signals from a charge transfer device having a plurality of successive stages through which charge packets respectively corresponding to analog signal samples injected into said device are propagated at a preselected shift cycle rate and including an input stage into which successive charge packets are injected at said preselected shift cycle rate, comprising:

• a source of an input signal and of a reference level signal,
• means for selectively sampling said reference level and input signal in alternating sequence, at said rate,
• means responding to said alternating sequence of reference and signal samples for injecting corresponding charge packets into said charge transfer device at said input stage thereof and at said rate, whereby successive charge packets propagating through said successive stages of said charge transfer device are related in a pair of sequential reference level and input signal charge packets,
• plural sampling means associated with respective, alternate ones of said successive stages of said charge transfer device, each thereof operable at said rate for sampling the potential of the associated stage induced therein by propagation of a charge packet therethrough and producing output samples indicative of the said potential and in the said sequence of a related pair of reference level output sample and a signal output sample,
• analog circuit means responsive to said sequential reference level and signal output samples of each said related pair to store a value corresponding to said reference level sample and, in the successive cycle, to compare the value of the related signal output sample of the pair and determine the difference therebetween and to supply the said difference value as the output signal from the said sampling means.

A system for enhancement of sensor output signals, comprising:

• a sensor including a plurality of columns of sensor elements, each column including plural sensor elements,
• plural columns of charge transfer devices corresponding to said columns of sensor elements and including a plurality of successive stages related as pairs, said plurality of successive stage pairs respectively corresponding to said plurality of sensor elements of each said column,
• a charge injector associated with the first stage of each successive pair of stages and associated with a corresponding sensor element of the corresponding column of said sensor array,
• means for providing a reference level,
• means for alternately sampling said reference level and the output from a sensor element, for all of said sensor elements, for supply to the respectively corresponding said injectors at the said cyclic rate, said injectors injecting successive charge packets corresponding to said reference level and said sensor output signals in successive shift cycles of said charge transfer devices,
• means associated with each of said column charge transfer devices for sampling, at said shift cycle rate, an output potential at an output stage of each thereof, produced by propagation of a charge packet to said output stage, and producing an output sample indicative of said output potential, said output samples including, in sequence, alternate reference level and associated sensor signal output samples, and
• analog circuit means for storing a value corresponding to said reference level output samples and comparing the said stored value with the said sensor signal output samples to determine the difference therebetween and to provide said difference as an output signal from said system.

A method of signal enhancement employing a charge transfer device having a succession of stages, plural charge injector means associated with alternate ones of said succession of stages for injection of charge packets thereinto, means for advancing charge packets through said successive stages at a predetermined rate, and means for sampling a serial output from the last of the successive stages at said rate, including the steps of:

• providing an input signal to be enhanced,
• providing a reference level,
• selecting a sample of said reference level and a sample of said signal to be enhanced in an alternating sequence, at said rate, and supplying said signal and reference level samples in said prescribed sequence in successive shift cycle intervals to the first and each successive charge injector associated with said charge transfer device, whereby the charge packets in the prescribed sequence and corresponding to said signal and reference level samples progress as a related pair through said successive stages of said charge transfer device, each thereof receiving additively a charge packet injection at each said successive injector of the corresponding said signal and reference level samples, and
• sampling the voltage level induced by said summed charge packets and producing corresponding summed output samples in the said prescribed sequence representing respectively the summation values of the signal and reference level samples for each said related pair of samples of said signal to be enhanced and said reference level, at the said rate, and
• storing a value corresponding to the said reference level summed output sample and comparing said stored value with the signal summed output sample of the said related pair of input signal and reference level samples, to determine the difference therebetween, and supplying the said difference as the output signal of said charge transfer device, said output signal being enhanced in amplitude relative to said input signal.