Range Imaging Device Dynamic Integration Time Control
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Solution Overview
Problem
Time-of-flight range imaging devices face challenges in accurately measuring distances due to charge saturation in charge storage units, especially when dealing with varying object reflectances and distances, which affects measurement accuracy and can lead to eye-safety violations from prolonged laser exposure.
Innovation Solution
The device employs a light source that emits pulses to a measurement space, a light-receiving unit with pixel circuits and charge storage units, and a measurement control unit that calculates a thinning time based on integrated charge and incident light intensity to determine the appropriate integration time and measurement zone, preventing charge saturation and ensuring eye-safety standards are met.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If integration time is increased to improve measurement accuracy for distant objects, then measurement precision is improved, but charge saturation occurs in charge storage units
Solution Approach 1:
The patent implements dynamic integration time adjustment where the integration time is varied based on the measured distance to the object. For distant objects, a longer integration time is used to accumulate sufficient charge, while for nearby objects, a shorter integration time prevents charge saturation. This dynamic adaptation resolves the contradiction between needing long integration times for accuracy and avoiding saturation.
Solution Approach 2:
The system changes the integration time parameter according to the object distance. By calculating the distance first and then selecting an appropriate integration time based on that distance, the system optimizes the integration parameter to prevent saturation while ensuring sufficient signal accumulation for accurate measurement.
2Measurement precision
If light pulse emission is prolonged to improve measurement accuracy, then measurement precision is improved, but eye-safety standards are violated
Solution Approach 1:
The system dynamically adjusts the light pulse emission duration based on the object distance. For distant objects where longer exposure is needed for accuracy, the system extends the emission time, while for nearby objects it reduces emission time to stay within eye-safety limits. This dynamic control resolves the contradiction between measurement accuracy and safety compliance.
Solution Approach 2:
The emission time parameter is changed according to the object distance. By selecting appropriate emission durations based on calculated distance, the system ensures sufficient light accumulation for accurate measurement while maintaining compliance with eye-safety standards through parameter optimization.
3Measurement precision
If integration time is extended to capture sufficient charge for distant objects, then measurement precision is improved, but measurement time increases
Solution Approach 1:
The system uses dynamic integration time selection based on distance classification. Objects are categorized into different distance ranges, and each range has an optimized integration time assigned. This prevents unnecessary long integration times for close objects while ensuring sufficient integration for distant objects, thus reducing overall measurement time while maintaining accuracy where needed.
Solution Approach 2:
The integration time parameter is optimized for different distance ranges. By changing the integration time parameter according to the object's distance category, the system achieves measurement accuracy for distant objects while minimizing measurement time for closer objects, thereby reducing overall time loss.
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 enhances measurement accuracy by preventing charge saturation and ensures compliance with eye-safety standards by dynamically adjusting integration times based on the intensity of incident light and object reflectance, effectively managing the emission of light pulses to maintain accurate distance measurements.
Implementation Method 1
a photoelectric conversion element that generates charge according to incident light
Data Source
AI summary
A range imaging device includes a light-receiving unit including at least one pixel circuit including a photoelectric conversion element that generates charge in response to incident light, N (N≥3) charge storage units that integrate charge in a frame cycle, and transfer transistors, and a pixel drive circuit that causes the transfer transistors to distribute charge to the charge storage units with integration timing synchronizing with light pulses, a light source unit that emits light pulses; a range image processing unit that calculates a distance to an object based on integrated charges, and a measurement control unit that calculates a thinning time of not integrating charge, according to integrated charge in the charge storage units, the distance, and intensity of the incident light. The measurement control unit controls integration of charge with a thinning time set in a measurement zone corresponding to the distance from the light-receiving unit.