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 includes at least one detector to detect target object reflected said energy and to output a detection signal used in determining time-of-flight to said target object, the method including the following steps:

• (a) for each said detector, integrating said detection signal and outputting an integration signal using a resettable integrator having dynamically variable gain;
• (b) for each said detector, comparing said integration signal against a threshold level using a comparator and outputting a comparator pulse when said integration signal exceeds said threshold level, an output of said comparator being fed-back to said detector;
• (c) each said detector, coupling a resettable logic counter to count each said comparator pulse;
• (d) reading-out as a measure of acquired said brightness data a count value from said logic counter when said logic counter attains a given count;
• and
• (e) resetting at least two of (I) said detector, (ii) said integrator, and (iii) said logic counter.

A circuit to resolve time-of flight (TOF) useable with a three-dimensional range finding system that emits energy and detects a portion of said energy reflected by a target object to determine TOF to said target object, 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 the propagated copy of emitted said energy coincides in time with the propagated copy of detected reflected said energy;
• wherein said means for determining defines a time interval at which time coincidence is determined for use in resolving said TOF.

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

• a first series-coupled group of N delay elements coupled to receive a copy of emitted said energy for propagation through said first series-coupled group, where N is an integer greater than one;
• a second series-coupled group of N delay elements coupled to receive a copy of detected reflected said energy for propagation through said second series-coupled group;
• a series-coupled group of N latch elements, each of said latch 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;
• and
• a phase discriminator coupled to receive an output from the Nth delay element in said first series-coupled group and from an Nth delay element in said second series-coupled group, said phase discriminator generating an output signal coupled to vary delay through said first series-coupled group of N delay elements;
• wherein a time interval defined within said N latch elements at which time 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 energy reflected by a target object determine TOF to the target object, 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 versions of the propagated said copy;
• and
• (c) comparing signals incrementally delayed through said first delay system with signals incrementally delayed through said second delay system to determine closest time coincidence of propagated compared said signals;
• wherein time 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 that emits energy a portion of which energy is reflected by a target object a distance Z from said IC to be detected by a photodiode detector in an array of photodiode detectors within said TOF measurement system, 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 with dynamically variable gain coupled to integrate a detection signal output by said photodiode detector;
• a comparator coupled to receive and to compare an integration signal output by said integrator against a threshold level and to output a comparator pulse when said integration signal exceeds said threshold level, an output of said comparator being fed-back to reset said photodiode detector;
• and
• a resettable logic counter coupled to count each said comparator pulse;
• means for providing a RESET signal to said resettable integrator and to said resettabie logic counter;
• wherein when said resettable logic counter attains a given count, a count value within said logic counter is read-out as an output of said circuit proportional at least in part to detected reflected said energy, and said RESET signal is provided to reset at least two of (i) said detector, (ii) said comparator, and (iii) 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 defined within said means for determining at which time coincidence is determined is used to resolve said TOF.