Method and system to enhance dynamic range conversion useable with CMOS three-dimensional imaging

A method to enhance dynamic range of brightness data acquired by a range finding system that emits energy and employs at least one detector to detect target object reflected said energy and to output a detection signal for use in determining time-of-flight to said target object, the method including the following steps:

• (a) providing for each said detector a resettable integrator having dynamically variable gain that is coupled to integrate said detection signal and to output an integration signal;
• (b) providing for each said detector a comparator coupled to receive and to compare said integration signal against a threshold level and to output a pulse when said integration signal exceeds said threshold level, an output of said comparator being fed-back to said detector;
• (c) for each said detector, providing a resettable logic counter coupled to count each said pulse output by said comparator;
• (d) reading out a count value from said logic counter when said logic counter attains a given count;
• and
• (e) resetting at least two of said detector, said integrator, and said logic counter.

A circuit to resolve time-of flight (TOF) useable with a three-dimensional range finding system that emits energy and detects reflected said energy to determine TOF to a target object reflecting said energy, the circuit comprising:

• first means for propagating a copy of emitted said energy;
• second means for propagating a copy of detected reflected said energy;
• and
• means for determining when in time the propagated copy of emitted said energy coincides with the propagated copy of detected reflected said energy;
• wherein a time interval within said means for determining at which coincidence is determined is used to resolve said TOF.

A circuit to resolve time-of flight (TOF) useable with a three-dimensional range finding system that emits energy and detects reflected said energy to determine TOF to a target object reflecting said energy, the circuit comprising:

• a first series-coupled group of N delay elements through which a copy of emitted said energy is propagated, where N is an integer greater than one;
• a second series-coupled group of N delay elements through which a copy of detected said energy is propagated;
• second means for propagating a copy of detected reflected said energy;
• and
• a series-coupled group of N latch elements, each of said elements having a first input coupled to an input of an associated one of said first series-coupled group of N delay elements, and having a second input coupled to an output of one of said second series-coupled group of N delay elements;
• a phase discriminator coupled to receive an output from said first and from said second series-coupled group of N delay elements, and generating an output signal therefrom that is coupled to vary delay through said first series-coupled group of N delay elements;
• wherein a time interval within said N latch elements at which coincidence is determined is used to resolve said TOF.

A method to resolve time-of flight (TOF) useable with a three-dimensional range finding system that emits energy and detects reflected said energy to determine TOF to a target object reflecting said energy, the method including the following steps:

• (a) propagating a copy of emitted said energy through a first delay system that permits observing incrementally delayed versions of the propagated said copy;
• (b) propagating a copy of detected reflected said energy through a second delay system that permits observing incrementally delayed version of the propagated said copy;
• (c) comparing signals incrementally delayed through said first delay system with signals incrementally delayed through said second delay system to determine closest coincidence of propagated said signals;
• wherein determination of closest said coincidence is used to resolve said TOF.

A CMOS-implementable integrated circuit (IC) time-of-flight (TOF) measurement system used with a generator emitting energy a portion of which is reflected by a target object a distance Z from said IC, the IC comprising:

• for each of said photodiode detectors, at least one of a first circuit and a second circuit;
• said first circuit comprising:
• a resettable integrator coupled to integrate a detection signal output by the photodiode detector, said resettable integrator having a dynamically variable gain G;
• a comparator coupled to receive and to compare an integration signal output by said integrator against a threshold level and to output a pulse when said integration signal exceeds said threshold level, an output of said comparator fed-back to reset said photodiode detector;
• and
• a resettable logic counter coupled to count each said pulse output by said comparator;
• means for providing a RESET signal to said integrator and to said logic counter;
• wherein when said resettable logic counter attains a given count, a count value within said logic counter is readout, and said RESET signal is provided to reset at least two of said detector, said comparator, and said logic counter;
• said second circuit comprising:
• first means for propagating a copy of emitted said energy;
• second means for propagating a copy of detected reflected said energy;
• and
• means for determining when in time the propagated copy of emitted said energy coincides with the propagated copy of detected reflected said energy;
• wherein a time interval within said means for determining at which coincidence is determined is used to resolve said TOF.