Time of Flight Camera Photon Correlation Successive Approximation
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Solution Overview
Problem
Existing 3D camera technologies face challenges in balancing performance parameters with physical size and power constraints, particularly in real-time 3D image acquisition, due to differences in power requirements for imaging near and far objects, and complexities in triangulation techniques.
Innovation Solution
A time of flight camera employs a two-phase acquisition method using photon correlation successive approximation, with longer pulses for coarse range estimation and shorter pulses for fine range acquisition, reducing signal waste and power consumption by time-gating and utilizing single-photon avalanche photodiodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If time of flight systems use longer light pulses for imaging far objects, then the imaging range is improved, but the power consumption increases and depth resolution deteriorates
Solution Approach 1:
The imaging process is segmented into two phases: a first phase using longer light pulses for coarse depth estimation over large ranges, and a second phase using shorter light pulses for fine depth estimation. This segmentation allows the system to adaptively switch between pulse durations based on the estimated depth, thereby extending imaging range while controlling power consumption by not always using the higher-power long pulse mode.
Solution Approach 2:
The system dynamically adjusts the light pulse duration based on the imaging conditions and depth estimates. The controller selectively switches between long and short pulse modes, making the pulse duration variable rather than fixed. This dynamic adaptation optimizes the balance between imaging range, depth resolution, and power consumption for different scene requirements.
2Measurement precision
If time of flight systems use shorter light pulses for fine depth resolution, then the depth resolution is improved, but the imaging range deteriorates and power consumption increases
Solution Approach 1:
The depth measurement process is divided into coarse estimation (using long pulses for large ranges) and fine estimation (using short pulses for high precision). This segmentation enables the system to achieve high depth resolution only when needed for closer objects, while maintaining extended imaging range for farther objects using the coarse estimation phase.
Solution Approach 2:
The system changes the light pulse duration parameter adaptively based on the imaging scenario. For distant objects, long pulses are used to maintain range; for closer objects requiring high precision, short pulses are used. This parameter change strategy optimizes the trade-off between imaging range and depth resolution.
3Adaptability or versatility
If multiple cameras are used for stereo triangulation, then the 3D imaging capability is improved, but the device size and processing complexity increase
Solution Approach 1:
The patent replaces the mechanical/stereo triangulation approach with a time of flight measurement system that uses temporal information (round-trip time of light) to determine depth. This substitution eliminates the need for multiple cameras and complex triangulation algorithms, reducing processing complexity while maintaining 3D imaging capability through direct time-based depth measurement.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient real-time 3D image acquisition with reduced power consumption and improved accuracy, meeting size and power constraints while maintaining high frame rates and depth resolution.
Implementation Method 1
Each pixel (e.g., first pixel 122) includes a photodetector (e.g., one or more single-photon avalanche photodiodes) to detect the image light
Implementation Method 2
Time of flight cameras typically employ a light source that directs light at an object, a sensor that detects the light that is reflected from the object, and a processing unit that calculates the distance to the objected based on the round-trip time it takes for the light to travel to and from the object
Data Source
AI summary
A time of flight camera includes a light source, a first pixel, a time-to-digital converting, and a controller. The light source is configured to emit light towards an object to be reflected back to the time of flight camera as image light. The first pixel includes a photodetector to detect the image light and to convert the image light into an electric signal. The time-to-digital converter is configured to generate timing signals representative of when the light source emits the light and when the photodetector detects the image light. The controller is coupled to the light source, the first pixel, and the time-to-digital converter. The controller includes logic that when executed causes the time of flight camera to perform operations. The operations include determining a detection window for a round-trip time of the image light based, at least in part, on the timing signals and first pulses of the light. The operations also include determining the round-trip time based, at least in part, on the timing signals and second pulses of the light detected within the detection window.