Method and system to enhance dynamic range conversion useable with CMOS three-dimensional imaging
First Claim
1. A high dynamic range circuit useable with a range finding system that detects reflected energy to determine time-of-flight to a target object reflecting said energy, the circuit comprising:
- at least one detector to detect reflected said energy and to output a detection signal;
for each said detector, a resettable integrator coupled to integrate said detection signal and output an integration signal, said resettable integrator having a gain G that is dynamically variable;
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 fed-back to reset said detector; and
for each said detector, 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.
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Abstract
High dynamic range brightness information is acquired by inputting detection current to a high (adjustable) gain resettable integrator whose output V(t) is compared to a Vth threshold by a comparator whose output is counted by a reset counter as V(t)≧Vth. When a desired count is attained, data acquisition ends, the counter is read, and the entire circuit is reset. A TOF data acquisition circuit includes first and second sequences of series-coupled delay units, and a like number of latch units coupled between respective delay units. A phase discriminator compares output from each chain and feedback a signal to one of the chains and to a comparator and can equalize delay through each chain. A control voltage is coupled to the remaining chain to affect through-propagation delay time. The latch units can capture the precise time when V(t)≧Vth. Successive measurement approximation can enhance TOF resolution.
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Citations
30 Claims
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1. A high dynamic range circuit useable with a range finding system that detects reflected energy to determine time-of-flight to a target object reflecting said energy, the circuit comprising:
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at least one detector to detect reflected said energy and to output a detection signal;
for each said detector, a resettable integrator coupled to integrate said detection signal and output an integration signal, said resettable integrator having a gain G that is dynamically variable;
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 fed-back to reset said detector; and
for each said detector, 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. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. 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:
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(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. - View Dependent Claims (9, 10, 11, 13, 14, 15, 16, 17, 18, 20, 21)
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12. 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:
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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.
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19. 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:
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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.
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22. 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:
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(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. - View Dependent Claims (23, 24, 25, 26, 28, 29, 30)
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27. 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:
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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.
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Specification