Time-of-Flight Sensor Threshold Circuit Ramp Driver
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Solution Overview
Problem
Time-of-flight laser range finding systems face challenges with fixed threshold settings, which limit their ability to accurately measure distances beyond close ranges due to decreasing light intensity, and require slow software adjustments that are not feasible within the required timeframes, leading to potential noise interference.
Innovation Solution
A time-of-flight sensor threshold circuit that continuously lowers its threshold voltage during a reading, using solid-state circuit elements and a synchronizing input signal to adjust the threshold value over time, allowing for a broader range of distance measurements while maintaining accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high threshold setting is used, then close distance targets can be detected, but distant targets cannot be detected due to decreasing light intensity
Solution Approach 1:
The patent implements a dynamic threshold setting that automatically adjusts the detection threshold based on the measured distance. The system starts with a higher threshold for close targets and gradually lowers it for distant targets, enabling the single sensor to detect targets across a wide range of distances without manual intervention.
Solution Approach 2:
The system changes the detection threshold parameter dynamically during the measurement process. By adjusting the threshold level according to distance, the system adapts to the decreasing light intensity from distant targets while maintaining noise rejection for closer targets.
2Adaptability or versatility
If a low threshold setting is used, then distant targets can be detected, but noise interference increases reducing measurement accuracy
Solution Approach 1:
The dynamic threshold adjustment ensures that the threshold is only lowered when distance measurements indicate distant targets. This prevents noise interference from affecting close target measurements while enabling distant target detection when needed.
Solution Approach 2:
The threshold parameter is changed conditionally based on distance information. The system maintains a higher threshold for close targets to reject noise, and only lowers the threshold when the target distance indicates that the returned light intensity has naturally decreased.
3Adaptability or versatility
If software control is used for threshold adjustment, then threshold values can be changed, but the adjustment speed is too slow for real-time measurement
Solution Approach 1:
The patent replaces software-based threshold adjustment with a hardware-based automatic adjustment mechanism. The system uses electronic circuitry that automatically modifies the detection threshold in real-time based on distance measurements, eliminating the slow software iteration process.
Solution Approach 2:
The system performs self-adjustment of the detection threshold without external software intervention. The automatic threshold adjustment circuit continuously monitors distance measurements and autonomously modifies the threshold parameter at the appropriate speed for real-time operation.
4Measurement precision
If multiple readings are taken to achieve correct threshold setting, then accurate measurement can be obtained, but measurement time increases
Solution Approach 1:
The automatic threshold adjustment operates continuously during the measurement process, allowing the system to obtain accurate threshold settings in a single reading. The continuous adjustment eliminates the need for multiple iterative readings required by software-based methods.
Solution Approach 2:
The system performs preliminary distance estimation and uses this information to pre-adjust the detection threshold before the actual measurement is completed. This preliminary action prevents the need for subsequent threshold adjustments and additional readings.
Data Source
AI summary
A time-of-flight sensor threshold circuit outputs a threshold voltage to a time-of-flight sensor, the threshold reducing over the duration of a time-of-flight measurement, which reduction can occur continually during the measurement. The circuit is provided with an initial threshold voltage portion to set the threshold voltage corresponding to a selected maximum threshold value, a time-dependent portion, to charge and discharge over time, to or from a current control portion, a threshold voltage ramp control portion to lower the threshold value over time by charging or discharging the time-dependent portion to or from the current control portion at a selected rate, and a synchronizing portion to synchronize current flow to or from the current control portion with a synchronizing input signal synchronized with an illumination pulse from a connected illuminator.