Photoelectric Conversion Device With Binary-Search Exposure Control
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Solution Overview
Problem
Existing TOF rangefinders using SPADs require lengthy time scans to accurately measure distance due to the need for fine time gate timing adjustments, limiting measurement speed.
Innovation Solution
A photoelectric conversion device employs a binary search method by dividing exposure periods into multiple subframes, comparing light values, and adjusting exposure periods based on these comparisons to enhance measurement speed and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fine time gate timing adjustments are made to accurately measure distance, then measurement precision is improved, but measurement time increases
Solution Approach 1:
The measurement process is divided into multiple subframes, with each subframe containing multiple exposure periods. This segmentation allows the system to perform coarse-to-fine searches efficiently, reducing the total number of measurements needed while maintaining accuracy.
Solution Approach 2:
The system performs preliminary measurements in earlier subframes to establish a search range, then uses this information to guide subsequent measurements. This preliminary action reduces the search space for later measurements, significantly decreasing total measurement time.
2Measurement precision
If multiple exposure periods are measured to improve accuracy, then measurement precision is improved, but productivity decreases
Solution Approach 1:
The system dynamically adjusts the number of exposure periods and subframes based on measurement requirements and conditions. This dynamic adaptation allows the system to maintain high precision when needed while maximizing measurement speed when conditions permit.
Solution Approach 2:
The system uses comparison results from previous subframes to feedback and adjust measurement parameters for subsequent subframes. This feedback mechanism allows the system to reduce the number of required measurements while maintaining accuracy, thereby improving productivity.
3Measurement precision
If exposure periods are extended to capture more light signals, then measurement precision is improved, but response time increases
Solution Approach 1:
The system uses periodic pulsed light emission with corresponding periodic exposure periods. This periodic action allows for efficient signal accumulation while maintaining fast response capability, as the system can quickly switch between exposure and non-exposure states.
Solution Approach 2:
The system performs preliminary signal accumulation in extended exposure periods during earlier subframes, then uses this accumulated signal information to reduce the number of subsequent measurements needed, thereby improving response time without sacrificing precision.
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 binary search method significantly reduces the number of measurements required, speeding up distance measurement while improving accuracy and reducing lag time, especially for moving objects.
Implementation Method 1
a photoelectric conversion unit, a light value holding unit configured to hold light values based on signal charges generated during a first exposure period and a second exposure period
Data Source
AI summary
A photoelectric conversion device includes a photoelectric conversion unit, a light value holding unit that holds light values based on signal charges generated during a first exposure period and a second exposure period having at least one of start timing and end timing different from that of the first exposure period, a comparison unit that compares the light value based on the signal charge generated during the first exposure period with the light value based on the signal charge generated during the second exposure period, and a control unit that sets a third exposure period and a fourth exposure period having at least one of the start timing and end timing different from that of the third exposure period on the basis of a comparison result of the comparison unit. The third and fourth exposure periods are less than at least one of the first and second exposure periods.