Variable Gain Integrator for 3D Active Imaging Time of Flight
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Solution Overview
Problem
Current 3D active imaging systems face limitations in simultaneous measurement of reflected flux and time of flight, often requiring high energy consumption, complex circuit designs, and limited temporal resolution, making them unsuitable for real-time and stealth applications.
Innovation Solution
A device with a variable gain integrator and a comparator in series, where the amplification gain is higher before exceeding a threshold voltage and lower after, allowing for accurate time of flight measurement without additional energy consumption or complex amplifiers, and enabling multimode imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple laser pulses and time windows are used to achieve high resolution in 3D slicing imaging, then measurement precision is improved, but loss of time increases due to the large number of pulses required for image reconstitution
Solution Approach 1:
The patent uses periodic laser pulsing combined with gated detection, where each pulse triggers a corresponding time window for detection. This periodic action allows the system to accumulate depth information over multiple pulses while maintaining real-time imaging capability through synchronized detection gates.
Solution Approach 2:
The system performs preliminary time calibration and depth mapping before actual imaging, storing reference information about flight times at different depths. This preliminary action allows subsequent images to be reconstructed more quickly by comparing against pre-established depth references rather than calculating each pixel from scratch.
2Measurement precision
If the number of laser pulses is increased to achieve high resolution, then measurement precision is improved, but device complexity increases due to the need for precise timing control of multiple pulses and windows
Solution Approach 1:
The patent combines the laser source, timing control, and detection gating into a synchronized system where a single trigger signal coordinates all components. This merging reduces complexity by eliminating the need for separate control systems for each pulse and window, as they are all governed by a unified timing mechanism.
Solution Approach 2:
The system incorporates feedback mechanisms where detected signal strength and timing information are fed back to adjust subsequent pulse timing and window positioning. This feedback loop automatically optimizes the timing parameters based on actual scene characteristics, reducing the need for manual calibration and simplifying control.
3Measurement precision
If conventional time-of-flight measurement by multiple sampling is used, then measurement precision is improved, but use of energy increases due to high sampling frequency requirements
Solution Approach 1:
Instead of continuous high-frequency sampling, the patent uses periodic sampling synchronized with laser pulse emission. The detection is activated only during specific time windows corresponding to each pulse, allowing the system to achieve accurate time-of-flight measurements while keeping the detector inactive most of the time, thus reducing energy consumption.
Solution Approach 2:
The system performs sampling at just the necessary moments when laser pulses are emitted and reflected light is expected to return, rather than continuously sampling at maximum frequency. This partial sampling approach provides sufficient measurement precision for the application while dramatically reducing the energy burden of constant high-speed sampling.
4Measurement precision
If conventional time-of-flight measurement by multiple sampling is used, then measurement precision is improved, but loss of time increases due to the need to store and process a large number of samples
Solution Approach 1:
The patent extracts only the most relevant information from each sampling cycle—specifically, the maximum signal amplitude and its corresponding time stamp—rather than storing and processing all raw samples. This extraction of essential data points maintains temporal resolution while minimizing the data volume that requires storage and processing, thereby reducing time loss.
Solution Approach 2:
The system performs full high-resolution sampling during the measurement phase to ensure temporal accuracy, but then processes only a reduced subset of this data (maximum amplitude points) for final image reconstruction. This partial processing approach achieves the necessary temporal resolution without the computational burden of processing every sampled point.
5Adaptability or versatility
If systems implement both passive 2D imaging and active 3D imaging modes, then adaptability is improved, but device complexity increases due to the need for multiple detection circuits
Solution Approach 1:
The patent designs the detection circuit to perform multiple functions: in passive mode, it integrates all incoming light signals for 2D imaging; in active mode, it performs time-gated detection for 3D imaging. The same photodetector and readout circuitry serve both purposes by adjusting the timing gates and integration windows, eliminating the need for separate dedicated circuits for each mode.
Solution Approach 2:
The system dynamically reconfigures the detection circuit parameters (integration time, gate timing, window duration) based on the selected operating mode. This dynamic adjustment allows a single static circuit architecture to adapt its behavior for different imaging modes, providing versatility without requiring multiple fixed circuits.
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 solution enables simultaneous measurement of reflected flux and time of flight with reduced energy consumption and simplified circuit design, improving temporal resolution and suitability for real-time and stealth applications.
Implementation Method 1
a photodiode capable of receiving incident radiation and to produce, as a function thereof, a current
Implementation Method 2
an integrator connected to the output of the amplifier and capable of integrating loads produced by the photodiode
Data Source
Figure 1~3
Figure 4~7
Figure 8
AI summary
The invention relates to a device comprising a photosensitive element (42) producing an electric charge in accordance with the radiation (44) incident thereon and a charge integrator (46, 48, 50) connected to the photosensitive element (42) and converting the charge to a voltage. According to the invention, the device includes a comparator (52), capable of comparing the voltage delivered by the integrator (46, 48, 50) with a threshold voltage, and a memory unit (56) for storing the instant when the voltage delivered by the integrator exceeds the threshold voltage.