TOF Distance Sensing with Sub-Pixel Noise Reference Extraction
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Solution Overview
Problem
Existing distance measuring methods using the Time-Of-Flight (TOF) scheme face challenges in improving measurement accuracy without requiring periods where light cannot be emitted and without increasing the size of the apparatus by adding separate light receiving units for noise measurement.
Innovation Solution
A distance measuring apparatus with multiple light emitting and receiving elements, where each receiving element includes sub-elements for signal and environmental light measurement, allowing for the calculation of a reference value from environmental light measurements to determine the time of flight of signal light with high accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light receiving unit for noise measurement is arranged in parallel with the light receiving unit for TOF measurement, then the accuracy of distance measurement is improved, but the apparatus becomes large in size
Solution Approach 1:
The patent combines the noise measurement function and TOF measurement function into a single light receiving unit. The light receiving unit includes multiple pixels that can be selectively used for environmental light measurement or TOF measurement, eliminating the need for separate parallel units and reducing apparatus size while maintaining measurement accuracy
Solution Approach 2:
The light receiving unit is designed to perform multiple functions: it can measure environmental light (noise) and measure TOF of signal light using the same hardware structure. By making the light receiving unit universal, the patent avoids increasing apparatus size while still enabling accurate noise subtraction for improved distance measurement
2Measurement precision
If the light source unit does not radiate light for noise measurement, then the accuracy of distance measurement is improved, but the frame rate for distance measurement decreases
Solution Approach 1:
The patent implements periodic switching between noise measurement mode and TOF measurement mode within the same light receiving unit. During specific time periods, certain pixels measure environmental light while others measure TOF, allowing continuous operation at high frame rates while still obtaining noise data for accuracy improvement
Solution Approach 2:
The patent performs noise measurement in advance or concurrently with TOF measurement by utilizing pixels that are not currently used for TOF measurement. This preliminary noise data is then used to subtract from the TOF measurement results, improving accuracy without requiring the light source to stop and without reducing frame rate
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
Enhances the accuracy of distance measurement by effectively distinguishing and removing noise components, thereby improving the precision of distance calculations.
Implementation Method 1
a plurality of light emitting elements; a plurality of light receiving elements... determine, as a time of flight of signal light for distance measurement, a time from light emission by any light emitting element among the plurality of light emitting elements to reception of reflected light
Implementation Method 2
each light receiving element in the plurality of light receiving elements includes a plurality of sub-light receiving elements... obtain a reference value from a measurement result of times of flights that are measured using detected signals of first sub-light receiving elements
Data Source
AI summary
A distance measuring apparatus with light emitting elements and light receiving elements determines, as a time of flight of signal light for distance measurement, a time from light emission by any light emitting element to reception of reflected light of emitted signal light by any light receiving element. A first light receiving element receives the reflected light by a subject and environmental light. Each light receiving element includes sub-light receiving elements. The apparatus obtains a reference value from a measurement result of times of flight that are measured using detected signals of first sub-light receiving elements, and determines a time of flight of signal light for distance measurement related to the subject with use of the reference value and a measurement result of times of flight that are measured using detected signals of second sub-light receiving elements.