Depth Sensor Distance Calculation Using Modulated Light Duty Ratio
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Solution Overview
Problem
Conventional depth sensor methods using time of flight (TOF) create ambiguity in distance measurement due to objects at certain ranges having the same phase value for a specific modulation frequency, leading to unclear distinction between different measurement distances.
Innovation Solution
A method utilizing a modulated light signal with a specific duty ratio and demodulation signals to calculate distances beyond the maximum measurable range by setting them equal to the maximum range, employing an image processing system with a light source, depth sensor pixels, and an image signal processor to process pixel signals and remove ambiguity, using correlation functions to determine sections of measured distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional TOF method is used to calculate distance, then measurement range is extended, but ambiguity distance occurs in the measurement range
Solution Approach 1:
The patent changes the modulation frequency parameter of the light signal to resolve ambiguity distances. By using multiple modulation frequencies (first and second modulation signals with different frequencies), the system can distinguish between objects at different distances that would otherwise have the same phase value, thereby eliminating measurement ambiguity while maintaining extended measurement range.
2Measurement precision
If modulation frequency is increased to improve measurement resolution, then phase measurement precision improves, but maximum measurable distance decreases
Solution Approach 1:
The patent segments the measurement task by using multiple modulation frequencies. The first modulation signal provides coarse distance measurement over a long range, while the second modulation signal with higher frequency provides fine phase measurement for distance differentiation. This segmentation allows the system to achieve both long maximum measurable distance and high phase measurement precision simultaneously.
Solution Approach 2:
The patent adds a temporal dimension by modulating the light signal at different frequencies. Instead of relying on a single frequency's phase information, the system uses multiple frequency components to create a richer measurement space, enabling simultaneous determination of both long range and precise phase differences.
3Device complexity
If single modulation frequency is used to simplify system complexity, then device complexity is reduced, but ambiguity distance cannot be distinguished
Solution Approach 1:
The patent makes the modulation system multi-functional by using multiple modulation frequencies for different purposes. The first modulation signal handles long-range measurement, while the second modulation signal handles fine phase differentiation. This multi-functionality allows the system to distinguish ambiguity distances without significantly increasing device complexity, as both frequencies are processed through the existing photo sensor and processing circuitry.
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 approach effectively removes ambiguity in distance calculations, allowing for clear distinction between different measurement distances and reducing errors in depth imaging, enabling accurate distance determination beyond the conventional maximum measurable range.
Implementation Method 1
The depth sensor among these sensors may measure a delay time or delay phase taken until a pulse signal output from a light source is reflected and returned by an object, and calculate a depth or a distance between the depth sensor and the object. The pulse signal may be a microwave, a light wave or an ultrasonics wave.
Implementation Method 2
receiving the modulated light signal reflected by the object
Implementation Method 3
calculating a distance between the light source and the object using the reflected modulated light signal input to photo gates in conjunction with demodulation signals supplied to the photo gates
Data Source
AI summary
A method of calculating, using a depth sensor, a distance excluding an ambiguity distance including outputting a modulated light signal output from a light source to an object, receiving the modulated light signal reflected by the object, calculating a distance between the light source and the object using the reflected modulated light signal input to photo gates in conjunction with demodulation signals supplied to the photo gates, the calculating including calculating, using the modulated light signal, at least one distance farther than a maximum measurable distance, and setting the at least one distance to be equal to the maximum measurable distance may be provided. A range of the distance farther than the maximum measurable distance can be determined according to a duty ratio of the modulated light signal.