Photodetection Circuit Using Dual-Resolution Timing Codes
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Solution Overview
Problem
Current photodetection devices face challenges in reducing circuit area while maintaining effective distance measurement capabilities, particularly in Time of Flight (ToF) methods, which require complex histogram generation and timing code processing.
Innovation Solution
The proposed solution involves a photodetection system with a light-receiving element, conversion circuit, and histogram generation circuit that generate multiple timing codes with different temporal resolutions, allowing for the creation of first and second histograms, thereby reducing circuit area while expanding distance measurement range and increasing temporal resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple timing codes with different temporal resolutions are generated to expand distance measurement range and increase temporal resolution, then measurement precision and adaptability are improved, but device complexity increases
Solution Approach 1:
The measurement period is segmented into multiple sub-periods with different temporal resolutions. A first timing code operates at a first temporal resolution during a first sub-period, while a second timing code operates at a second temporal resolution during a second sub-period. This segmentation allows the system to achieve both high precision for nearby objects and extended range for distant objects without requiring a single complex high-resolution timing circuit for the entire measurement range.
2Measurement precision
If multiple histograms are generated to process detection timing data with different temporal resolutions, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The histogram generation circuit is designed to perform multiple functions by generating both a first histogram from the first timing code and a second histogram from the second timing code. This multi-functional histogram circuit processes detection timing data at different temporal resolutions, enabling the system to accurately measure distances across varying ranges using a single unified histogram generation component rather than requiring separate dedicated circuits for each resolution level.
3Measurement precision
If the TDC operates with high temporal resolution to generate accurate timing codes, then measurement precision is improved, but circuit area increases
Solution Approach 1:
The system dynamically switches between different temporal resolutions based on the measurement requirements. During a first sub-period, the timing code operates at a first temporal resolution suitable for measuring shorter distances, and during a second sub-period, it operates at a second temporal resolution for measuring longer distances. This dynamic adjustment allows the TDC circuit to maintain high measurement precision when needed while reducing its operational complexity and area requirements during periods when lower resolution suffices.
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 a more compact photodetection device with enhanced distance measurement capabilities, allowing for wider range and higher temporal resolution without increasing circuit size, by using multiple timing codes and histograms to distinguish between different detection timing periods.
Implementation Method 1
a light-receiving element configured to detect a light pulse
Data Source
AI summary
A photodetection device of the present disclosure includes a light-receiving element, a conversion circuit, and a histogram generation circuit. The light-receiving element is configured to detect a light pulse. The conversion circuit is configured to: generate a first code that sequentially changes during a first period having a first time length in a frame period and that circulates multiple times in units of the first period; generate a second code that sequentially changes during a second period having a second time length in the frame period and that circulates multiple times in units of the second period; generate a first timing code by sampling the first code in accordance with a detection timing of the light pulse; and generate a second timing code by sampling the second code in accordance with the detection timing. The histogram generation circuit is configured to generate a first histogram related to the first timing code and generate a second histogram related to the second timing code.