SPAD Detector Array with Segmented Detection Areas for Ranging Accuracy
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Solution Overview
Problem
Single photon avalanche diode (SPAD) devices face accuracy issues due to the pile-up effect when receiving strong returned light, leading to ranging inaccuracy, especially in scenarios with highly reflective objects or short distances, as the dead time prevents immediate response to subsequent photons, causing saturation and inaccurate reflectance evaluation.
Innovation Solution
A detector module with a detector array comprising pixel groups of first and second ranging pixels, each with distinct detection regions of different areas, coupled with processing units and digital processing units to generate time of flight signals and perform statistical computing, thereby improving resistance to strong light and ambient conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a pixel detector array with large effective area is used to receive returned photons, then the detection capability is improved, but the pile-up effect occurs causing ranging inaccuracy
Solution Approach 1:
The detector array is segmented into multiple pixel groups with different detection area ratios. Each pixel group contains first ranging pixels with larger detection areas and second ranging pixels with smaller detection areas, allowing differentiated response to photon intensity levels and mitigating the pile-up effect across the entire array.
Solution Approach 2:
Different regions of the detector array are assigned different detection area ratios to optimize local performance. Pixel groups with higher proportions of second ranging pixels (smaller detection area) are positioned to receive strong returned light, while pixel groups with more first ranging pixels (larger detection area) handle weaker signals, creating local optimization throughout the array.
2Reliability
If the SPAD detects strong returned light, then the detection sensitivity is improved, but the dead time causes the SPAD to be unable to react immediately to subsequent photons
Solution Approach 1:
The pixel detector array is divided into multiple pixel groups with different detection area ratios, allowing parallel processing of detection tasks. While some pixel groups process strong signals that trigger dead time, other pixel groups continue detecting weaker signals, effectively reducing the overall dead time impact on measurement accuracy.
Solution Approach 2:
The system uses pixel groups with smaller detection areas (second ranging pixels) that can process signals more quickly with shorter dead times, providing partial detection capability that compensates for the excessive dead time in pixel groups with larger detection areas during strong light conditions.
3Quantity of substance
If the pixel sensor array receives photons with higher intensity, then the detection capability is improved, but the histogram pile-up causes the detection time to be less than the actual one
Solution Approach 1:
The detector array is segmented into pixel groups with different detection area ratios, creating multiple detection channels with different response characteristics. This segmentation allows the system to resolve the histogram pile-up effect by comparing detection times across different pixel groups, thereby recovering accurate detection time information.
Solution Approach 2:
The system uses the detection time information from pixel groups with smaller detection areas as feedback to correct the detection times from pixel groups with larger detection areas. This feedback mechanism compensates for the histogram pile-up effect and restores accurate ranging measurements.
4Quantity of substance
If a large detection area is used, then the photon collection capability is improved, but the reflectance evaluation becomes saturated due to strong returned light
Solution Approach 1:
The detector array is segmented into pixel groups with different detection area ratios, allowing the system to evaluate reflectance using multiple detection channels with different saturation characteristics. This segmentation prevents single-point saturation and enables robust reflectance measurement through aggregation of unsaturated pixel group data.
Solution Approach 2:
The system changes the detection area parameter across different pixel groups to optimize reflectance measurement. By having pixel groups with varying detection area ratios, the system can adjust the effective detection parameter to match the intensity level of returned light, preventing saturation while maintaining accurate reflectance evaluation.
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
The solution enhances measurement accuracy by mitigating the pile-up effect, providing accurate depth information and immune to sunlight and ambient light interference, allowing for precise characterization of different environmental conditions.
Implementation Method 1
Single photon avalanche diode (SPAD) may detect single photon even in low light scenarios due to its high sensitivity
Implementation Method 2
The detector array receives the returned light to generate the detection signals
Data Source
AI summary
A detector module and a ranging device are provided. The detector module includes a detector array including a plurality of pixel groups each of which has a plurality of ranging pixels. A first pixel group of the pixel groups includes a plurality of first ranging pixels each of which includes a first detection region. A second pixel group of the pixel groups includes a plurality of second ranging pixels each of which includes a second detection region. Area of the first detection region and area of the second detection region are different from each other. The ranging device provides higher accuracy due to difference area of the first detection region and the second detection region of the detector module.