Range Imaging Exposure Control Using Signal Variation
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Solution Overview
Problem
Existing range imaging devices struggle to accurately determine exposure times in varying lighting conditions, leading to issues such as underexposure or overexposure, which affect the reliability and precision of distance measurements.
Innovation Solution
A range imaging device that includes a light source, a light-receiving unit with charge storage units, and a range image processing unit that calculates distances based on integrated charge amounts, using a pixel driver circuit to synchronize charge distribution with light pulse emission and adjusts exposure time based on integrated signal variations to account for both reflected and ambient light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If exposure time is increased to capture more light in low-light conditions, then signal strength improves, but overexposure occurs in bright conditions leading to measurement errors
Solution Approach 1:
The patent implements dynamic exposure time adjustment by analyzing the integrated signal characteristics (mean and variance) from the current frame and adapting the exposure time for the next frame. The pixel driver circuit synchronizes charge distribution with light pulse emission timing, and the range image processing unit calculates optimal exposure time based on signal variation analysis, allowing the system to adapt to varying lighting conditions in real-time.
Solution Approach 2:
The system uses feedback from the integrated signal analysis to control exposure time. The range image processing unit calculates the mean and variance of integrated signals, identifies signals containing both reflected and ambient light components, and uses this information to adjust exposure time in subsequent frames. This closed-loop feedback mechanism ensures optimal exposure across different lighting conditions.
2Measurement precision
If exposure time is decreased to prevent overexposure in bright conditions, then measurement precision improves, but underexposure occurs in low-light conditions reducing signal strength
Solution Approach 1:
The system dynamically adjusts exposure time based on real-time signal analysis. By calculating the mean and variance of integrated signals and identifying the characteristic signature of reflected plus ambient light, the system determines the appropriate exposure time for each frame, ensuring both precision and reliability across varying lighting conditions.
Solution Approach 2:
The patent changes the exposure time parameter adaptively based on the analyzed integrated signal characteristics. The range image processing unit modifies the exposure time parameter for subsequent frames based on the mean and variance calculations from the current frame, allowing the system to optimize between precision and reliability by adjusting this key parameter in response to lighting conditions.
3Device complexity
If fixed exposure time is used to simplify control, then device complexity reduces, but exposure accuracy deteriorates in varying lighting conditions
Solution Approach 1:
The system performs self-adjustment of exposure time by analyzing its own integrated signal characteristics. The pixel driver circuit and range image processing unit work together to automatically determine optimal exposure parameters based on the mean and variance of the captured signals, eliminating the need for external manual adjustment or complex control mechanisms while maintaining high exposure accuracy.
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 device effectively controls exposure time to optimize imaging conditions, reducing underexposure and overexposure, thereby enhancing the accuracy and reliability of distance measurements in diverse lighting environments.
Implementation Method 1
a photoelectric conversion device that generates charge corresponding to incident light
Data Source
AI summary
A range imaging device includes a light source that emits light pulse to measurement space; a light-receiving unit including a pixel having a photoelectric conversion device that generates charge corresponding to incident light and charge storage units that integrates the charge, and a pixel driver circuit that distributes the charge to the storage units; and a range image processing unit that calculates distance to subject in the space. The processing unit calculates lower threshold based on degree of variation in integrated signal identified to contain, among integrated signals corresponding to the amounts of charge integrated in the storage units in current frame, signal corresponding to amount of charge originating from the light pulse reflected off the subject, and signal corresponding to amount of charge originating from ambient light, and uses the integrated signal and lower threshold to control exposure time in another frame that is temporally after the current frame.