Optical Ranging Pixel Exposure Control for Distance Data
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Solution Overview
Problem
Optical ranging systems face challenges in generating accurate distance data due to under-exposure or over-exposure of pixels, leading to insufficient or saturated charge carriers, which affects the signal-to-noise ratio and requires resource-intensive adjustments in integration time, sensitivity, and amplification, particularly in real-time applications.
Innovation Solution
The method involves initializing an optical ranging system to collect electrical charges with adjustable amplification and sensitivity, correlating exposure values to identify valid and invalid exposures, and dynamically adjusting integration time and pixel settings based on exposure ratios to optimize pixel exposure, thereby ensuring accurate distance data generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If integration time is increased to collect more light and generate more charge carriers, then the signal-to-noise ratio is improved, but the time consumption increases which is problematic for real-time applications
Solution Approach 1:
The patent implements dynamic adjustment of integration time based on scene conditions. The system automatically selects between short integration time mode (for real-time performance) and long integration time mode (for high signal-to-noise ratio) based on the number of photons detected, allowing optimal balance between speed and precision for different operating conditions
Solution Approach 2:
The system changes the integration time parameter dynamically based on detected light levels. When insufficient photons are detected, the integration time is extended to improve signal-to-noise ratio. When sufficient photons are detected, the integration time is reduced to enable real-time operation, thus adapting the parameter to current operational needs
2Measurement precision
If pixel sensitivity is increased to collect more light, then the signal-to-noise ratio is improved, but the pixels may become over-exposed and saturate, losing the ability to generate accurate distance data
Solution Approach 1:
The patent implements dynamic adjustment of pixel sensitivity based on incident light levels. The system monitors the number of photons detected and automatically adjusts sensitivity downward when light levels are high to prevent saturation, and upward when light levels are low to improve signal-to-noise ratio, thus maintaining reliable operation across varying conditions
Solution Approach 2:
The system uses feedback from photon detection to control pixel sensitivity. The number of photons detected serves as feedback that triggers automatic adjustment of sensitivity parameters, creating a closed-loop control system that prevents over-exposure while maximizing signal collection in low-light conditions
3Measurement precision
If amplification is increased to generate more charge carriers from incident light, then the signal-to-noise ratio is improved, but the pixels may become over-exposed and saturate
Solution Approach 1:
The patent implements dynamic adjustment of amplification based on incident light levels and detected photon counts. The system reduces amplification when light levels are high to prevent saturation, and increases amplification when light levels are low to improve signal-to-noise ratio, thus maintaining reliable distance measurement across varying illumination conditions
Solution Approach 2:
The system changes the amplification parameter dynamically based on operational conditions. By monitoring photon detection levels, the system automatically adjusts amplification to keep the signal within the optimal range for accurate measurement, preventing both under-exposure and over-exposure scenarios
4Measurement precision
If the dynamic range of pixels is adjusted to accommodate varying light conditions, then adequate exposure can be achieved, but the adjustment process consumes significant resources and is time-consuming
Solution Approach 1:
The patent implements dynamic adjustment of pixel integration time based on the number of photons detected during the integration period. The system automatically extends integration time when insufficient photons are detected and reduces it when sufficient photons are detected, enabling real-time adaptation without resource-intensive manual adjustments
Solution Approach 2:
The system performs self-adjustment of integration time parameters based on autonomous monitoring of photon detection levels. The pixels themselves provide the information needed to trigger parameter adjustments, eliminating the need for external control or resource-intensive calibration processes while maintaining adequate exposure
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 rapid and accurate generation of distance data in real-time or near real-time by optimizing integration times and pixel settings, reducing resource consumption and improving data quality by ensuring pixels are adequately exposed.
Implementation Method 1
The pixels can be operable to collect incident light and can generate distance data. The pixels can be, for example, time-of-flight pixels. Generally, the pixels, including associated circuity, can collect incident light and generate electrical charge carriers
Implementation Method 2
The pixels can be, for example, time-of-flight pixels
Data Source
AI summary
A distance acquisition method comprising: initializing an optical ranging system, the optical ranging system including a plurality of pixels operable to covert incident light to electrical charges; collecting electrical charges with the plurality of exposed pixels over an integration time, each pixel collecting electrical charges with an amplification and a sensitivity; correlating the electrical charges collected in each pixel to an exposure value for each pixel, the exposure value corresponding to being adequately exposed, over-exposed, or under-exposed; identifying each exposure value for each pixel as being either valid or invalid, wherein a valid exposure value corresponds to an adequately exposed pixel and an invalid exposure value corresponds to an over-exposed or under-exposed pixel; totalling the number of valid exposure value pixels; totalling the number invalid exposure value pixels; determining an exposure ratio, the ratio being the number of pixels with valid exposure values divided by the number of pixels with invalid exposure values; totalling the number of over-exposed pixels; totalling the number of under-exposed pixels; determining an invalid exposure ratio, the invalid exposure ratio being the number of over-exposed pixels divided by the number of under-exposed pixels; and determining an average valid exposure value, the average valid exposure value being the average of the valid exposure values. The method additionally comprises: using the exposure ratio, the invalid exposure ratio and the average valid exposure to optimise the integration time; using the exposure value for each pixel to optimise the amplification and sensitivity for each pixel; and determining distance data from electrical charges collected from at least one of the plurality of pixels.