Time-of-Flight Distance Sensor Using Multi-Pulse Segmentation
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Solution Overview
Problem
Conventional distance image sensors using time-of-flight methods face a trade-off between increasing the distance measurement range and enhancing distance resolution, as increasing the modulation frequency of light is required for both, but this leads to conflicting requirements for pulse width, where wider pulses are needed for range and narrower pulses for resolution.
Innovation Solution
A distance image sensor and method that utilize multiple radiation pulses with different shift amounts and imaging windows to measure time-of-flight at various timings, generating element image signals that combine distance information across different ranges without increasing pulse width, thereby maintaining resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the pulse width of light is increased to increase the distance measurement range, then the measurable distance range is extended, but the distance resolution deteriorates
Solution Approach 1:
The patent divides the distance measurement process into multiple segments by using multiple imaging timings (1st to n-th imaging timings). Each imaging timing captures distance information for a specific range, and the processing unit combines these segmented measurements to achieve both extended range and maintained resolution. This segmentation allows the system to measure different distance ranges without requiring a single wide pulse that would degrade resolution.
Solution Approach 2:
The patent transitions from a single-dimensional measurement approach (single pulse width) to a multi-dimensional approach by introducing multiple imaging timings and combining distance information from different time points. This dimensional expansion in the time domain allows simultaneous achievement of extended measurement range and preserved distance resolution.
2Measurement precision
If the modulation frequency of light is increased to enhance distance resolution, then the distance resolution is improved, but the distance measurement range is reduced
Solution Approach 1:
The patent segments the measurement task across multiple imaging timings, where each timing is optimized for specific distance ranges. This allows the system to maintain high modulation frequency for resolution in each segment while collectively covering a broader distance range through combination of multiple segments.
Solution Approach 2:
The patent employs periodic imaging operations at multiple timings (1st to n-th imaging timings) to capture distance information. This periodic action across different time points enables the system to maintain high frequency modulation for resolution while extending the effective measurement range through temporal diversification.
3Measurement precision
If the pulse width of light is decreased to enhance distance resolution, then the distance resolution is improved, but the distance measurement range is reduced
Solution Approach 1:
The patent segments the distance measurement into multiple timing intervals, allowing narrow pulses to be used at each segment for high resolution while the combination of multiple segments extends the overall measurement range. Each segment captures a portion of the total range with high precision.
Solution Approach 2:
The patent adds the time dimension by performing measurements at multiple imaging timings, transforming a single narrow pulse measurement into a multi-temporal measurement sequence. This dimensional change allows narrow pulses to achieve high resolution while the temporal extension covers broader distance ranges.
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
Enables increased distance measurement range without reducing distance resolution by using multiple shifted pulses and imaging windows to gather distance information across a wide range, ensuring accurate distance measurement.
Implementation Method 1
a detection element for sensing incident radiation to generate electric charge
Implementation Method 2
measuring time-of-flight of light... generates 1st to n-th element image signals corresponding respectively to 1st to n-th times-of-flight
Data Source
AI summary
A distance image sensor capable of enlarging the distance measurement range without reducing the distance resolution is provided. A radiation source 13 provides first to fifth pulse trains PT1 to PT5 which are irradiated to the object as radiation pulses in the first to fifth frames arranged in order on a time axis. In each of the frames, imaging times TPU1 to TPU5 are prescribed at points of predetermined time ΔTPD from the start point of each frame, also the pulses PT1 to PT5 are shifted respectively by shift amounts different from each other from the start point of the first to fifth frames. A pixel array 23 generates element image signals SE1 to SE5 each of which has distance information of an object in distance ranges different from each other using imaging windows A and B in each of five frames. A processing unit 17 generates an image signal SIMAGE by combining the element image signals. Since five times-of-flight measurement are used, the width of the radiation pulse does not have to be increased to obtain distance information of the object in a wide distance range, and the distance resolution is not reduced.