Time-of-flight Distance Sensor Noise Subtraction
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Solution Overview
Problem
Existing time-of-flight distance measurement devices face accuracy issues due to background noise and have a low frame rate when noise fluctuates rapidly, making precise distance measurement challenging.
Innovation Solution
A distance measurement device using a time-of-flight method with a light source unit, sensor unit, and processing unit, where the sensor unit includes two accumulation regions and transfer electrodes to differentiate between signal and noise charges, allowing for precise distance calculation without reducing frame rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If noise subtraction is performed using two frame periods, then measurement precision is improved, but productivity deteriorates due to low frame rate
Solution Approach 1:
The sensor unit is divided into multiple photosensitive regions, each independently generating charges. This segmentation allows parallel processing of multiple signal channels within a single frame period, enabling noise subtraction without sacrificing frame rate.
Solution Approach 2:
The invention uses periodic modulation of the light source and synchronous detection within each frame period. By modulating the light source at a specific frequency and detecting signals synchronously, the system can perform multiple measurements and noise subtractions within a single frame period, maintaining high frame rate while improving precision.
2Measurement precision
If additional accumulation regions are added for noise measurement, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The photosensitive regions serve multiple functions: they generate signal charges during light emission periods and simultaneously generate noise charges during non-emission periods. This multi-functionality eliminates the need for separate noise accumulation regions, reducing device complexity while maintaining noise removal capability.
Solution Approach 2:
The system uses its own photosensitive regions to generate both signal and noise charges independently. By utilizing the inherent capability of the photosensitive regions to generate charges from background light, the system performs self-service noise measurement without requiring additional dedicated noise accumulation components.
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 high-precision distance measurement even with rapidly fluctuating background noise, maintaining frame rate without the need for additional noise accumulation regions, thus simplifying the sensor configuration and improving space resolution.
Implementation Method 1
A time-of-flight (TOF) method for measuring a distance from an object to a distance sensor by emitting a pulsed light from a light source and receiving reflected light from the object using the distance sensor
Implementation Method 2
acquires, from a distance sensor, a signal having a value corresponding to an amount of charges generated by a photodiode of the distance sensor
Data Source
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AI summary
In a distance measurement device of an embodiment, a light source emits modulation light in a first charge transfer cycle, and emission of the modulation light of the light source is stopped in a second charge transfer cycle. In each of the first and second charge transfer cycles, the charges generated in a photosensitive region are distributed to a first accumulation region and a second accumulation region. A first value is obtained by subtracting, from a value of twice a first readout value corresponding to the amount of accumulated charges of the first accumulation region immediately after the first charge transfer cycle, a first readout value corresponding to an amount of accumulated charges of the first accumulation region immediately after a second charge transfer cycle which is immediately before the first charge transfer cycle and a readout value corresponding to an amount of accumulated charges immediately after a next second charge transfer cycle of the first charge transfer cycle. A second value is obtained by performing a similar process on the second accumulation region. A distance is calculated based on the first value and the second value.