ToF Distance Sensor Dynamic Range Expansion via Segmented Charge Accumulation
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Solution Overview
Problem
Existing distance measuring devices using time-of-flight methods face limitations in expanding the dynamic range of reflected light intensity, leading to saturation at high intensities and signal shortage at low intensities.
Innovation Solution
A distance measuring device with a light source unit, sensor unit, and processing unit that emits modulated light and controls charge transfer cycles to accumulate charges, increasing emission periods per charge transfer cycle, and using multiple accumulating regions with phase-reversed transfer periods to expand the dynamic range without altering the frame period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of emission periods per charge transfer cycle is increased, then the dynamic range of reflected light intensity is expanded, but the frame period must be extended
Solution Approach 1:
The sensor unit is divided into multiple accumulating regions (first accumulating region and second accumulating region) that operate in parallel with phase-reversed charge transfer cycles. This segmentation allows the system to process multiple emission periods simultaneously without extending the overall frame period, thereby expanding the dynamic range while maintaining the original timing constraints.
Solution Approach 2:
The patent employs periodic charge transfer cycles with phase reversal between different accumulating regions. By alternating the charge transfer timing between the first and second accumulating regions, the system can accommodate multiple emission periods within each frame period, effectively increasing the dynamic range without extending the frame duration.
2Reliability
If the accumulating region capacity is increased to handle high light intensity, then saturation is prevented, but the device complexity increases
Solution Approach 1:
Instead of using a single large-capacity accumulating region, the patent divides the accumulation function across multiple smaller accumulating regions that operate in parallel. Each region handles a portion of the total light intensity, preventing saturation in any single region while avoiding the complexity of designing and managing one extremely large capacity region.
Solution Approach 2:
The patent implements dynamic control of charge transfer timing through phase-reversed cycles between different accumulating regions. This dynamic switching allows the system to adaptively distribute the accumulation load based on light intensity conditions, preventing saturation while maintaining a relatively simple sensor structure.
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 measures distances across a wider range of reflected light intensities, preventing saturation at high intensities and minimizing signal shortage at low intensities, thereby enhancing measurement accuracy and dynamic range.
Implementation Method 1
a photosensitive region configured to generate a charge in accordance with incident light
Data Source
AI summary
The processing unit causes a light source unit to emit modulated light in one or more emission periods in a plurality of charge transfer cycles within a frame period from connection of an accumulating region to a reset potential to next connection of the accumulating region to the reset potential by controlling a reset switch, and increases the number of emission periods per charge transfer cycle within one frame period. The processing unit obtains, from a sensor unit, a plurality of read values corresponding to a charge amount accumulated in the accumulating region at an alternate point with the plurality of charge transfer cycles, in each of a plurality of read cycles corresponding to each of the plurality of charge transfer cycles. The processing unit calculates the distance based on the plurality of obtained read values.