Time of Flight Sensor Dynamic Mode Switching for Resolution and Power
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Solution Overview
Problem
Time of flight sensing methods face challenges in achieving high signal-to-noise ratios for distant objects while maintaining resolution, as combining pixels reduces depth map resolution and requires repeated light pulses, depleting battery power in handheld devices.
Innovation Solution
A method where groups of photo-detectors operate in different modes based on measured times of flight, switching between combining outputs for distant objects and processing individual outputs for close objects, allowing parallel capture of high and low resolution data without the need for multiple depth maps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pixels are combined to form macropixels to improve signal-to-noise ratio for distant objects, then signal-to-noise ratio is improved, but depth map resolution is reduced
Solution Approach 1:
The patent dynamically switches between two operational modes for different groups of photo-detectors based on real-time conditions: combining outputs (macropixel mode) when signal-to-noise ratio is insufficient, and processing individually (high resolution mode) when signal is adequate. This dynamic adaptation resolves the contradiction by allowing the system to optimize between resolution and signal quality depending on the specific measurement context.
2Measurement precision
If two full depth maps are obtained (one low resolution and one high resolution) to address resolution loss, then depth map quality is improved, but power consumption increases due to multiple light source operations
Solution Approach 1:
The patent applies local quality by allowing different groups of photo-detectors to operate in different modes simultaneously within the same sensor array. Some groups combine outputs for distant objects requiring higher signal-to-noise ratio, while other groups process individually for close objects where resolution is paramount. This eliminates the need to capture two complete depth maps, thereby reducing power consumption while maintaining overall depth map quality.
3Measurement precision
If multiple light pulses are emitted to capture both low and high resolution depth maps, then depth map completeness is improved, but battery life is reduced
Solution Approach 1:
The patent segments the photo-detector array into multiple groups that can be independently configured to operate in different modes. This segmentation allows the system to process different spatial regions with different requirements simultaneously using a single light pulse, eliminating the need for multiple sequential pulses and thereby preserving battery life while maintaining depth map completeness.
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 conserves power by avoiding the need for multiple light pulses, enabling high resolution for close objects and low resolution for distant objects while maintaining acceptable signal-to-noise ratios, thus extending battery life in handheld devices.
Implementation Method 1
light reflected back towards the sensor from an object is detected
Implementation Method 2
The distance between the sensor and the object is determined based upon the elapsed time between emission of the pulse of light and detection of the pulse of light by the sensor
Implementation Method 3
The pixels may for example be single photon avalanche photodiodes (or some other form of photo-detector)
Data Source
AI summary
A method of time of flight sensing. The method comprises using an emitter to emit pulses of radiation and using an array of photo-detectors to detect radiation reflected from an object. For a given group of photo-detectors of the array, the method determines based upon measured times of flight of the radiation, whether to use a first mode of operation in which outputs from individual photo-detectors of the group are combined together or to use a second mode of operation in which outputs from individual photo-detectors are processed separately. The array of photo-detectors comprises a plurality of groups of photo-detectors. One or more groups of photo-detectors operate in the first mode whilst in parallel one or more groups of photo-detectors operate in the second mode.