Time of Flight Ranging with Fluorescent Wavelength Separation
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Solution Overview
Problem
Conventional time of flight (TOF) sensors face accuracy issues due to interference from ambient light and struggle with objects made of certain materials, such as black plastic, which complicates reliable light reflection and detection.
Innovation Solution
The method involves projecting light of a first wavelength onto an object and receiving both reflected and emitted light of different wavelengths, using a processor to determine the phase difference between the two to calculate the distance, with the light being deviated by optical elements like prisms or diffraction gratings to separate and detect the wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional TOF sensors use single wavelength light for ranging, then the system is simple to operate, but measurement precision deteriorates due to interference from ambient light and difficulty in detecting reflected light from certain materials
Solution Approach 1:
The patent segments the light detection into multiple wavelength channels by using a diffraction grating to spatially separate reflected light (first wavelength) from emitted light (second wavelength). This allows independent measurement of each wavelength component, improving distance measurement accuracy by enabling the system to distinguish between different light sources and filter out ambient light interference.
Solution Approach 2:
The patent adds the wavelength dimension to the traditional time-of-flight measurement. By measuring phase differences at multiple wavelengths and combining this with time-of-flight data, the system creates a multi-dimensional measurement approach that improves precision while maintaining operational simplicity through integrated processing.
2Measurement precision
If conventional TOF sensors measure only reflected light, then the device complexity is low, but measurement precision deteriorates when measuring objects with difficult-to-detect surfaces such as black plastic
Solution Approach 1:
The patent employs fluorescent materials that change color (wavelength) when illuminated. The illumination source emits light at a first wavelength that excites the fluorescent material, which then emits light at a second wavelength. This wavelength transformation enables detection on challenging surfaces like black plastic, as the emitted light has different properties than the reflected light, improving contrast and detectability.
Solution Approach 2:
The fluorescent material acts as an intermediary between the illumination source and the sensor. Instead of directly detecting reflected light from the object surface, the system uses the fluorescent material to convert the illumination wavelength to a different wavelength, which is then easier to detect and measure, thereby improving measurement precision on difficult surfaces.
3Reliability
If conventional TOF sensors use single wavelength measurement, then the device complexity is low, but reliability deteriorates due to interference from ambient light and inability to factor out noise
Solution Approach 1:
The patent segments the optical signal into multiple wavelength components using a diffraction grating, separating the reflected light signal from the emitted fluorescent light signal. This spatial segmentation allows the sensor to independently measure each wavelength channel, enabling the system to identify and filter out ambient light interference and noise, thereby improving measurement reliability.
Solution Approach 2:
The system uses the phase difference measurement between reflected and emitted light at multiple wavelengths as feedback to improve reliability. By comparing phase measurements across different wavelengths and using this information to validate and correct distance measurements, the system can factor out noise and maintain reliable operation under varying ambient light conditions.
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 enhances the accuracy of distance measurement and object parameter determination by filtering out noise and improving detection on challenging surfaces, enabling more precise ranging and dimensioning.
Implementation Method 1
the first wavelength is an excitation wavelength of a fluorophore and the second wavelength is an emission wavelength of the fluorophore
Implementation Method 2
the prism deviates the reflected light at a first angle based on the first wavelength, and receiving, at a first sensor position of the one or more sensors after the prism deviates the reflected light at the first angle, the reflected light
Implementation Method 3
By carefully timing the phase shift of the arriving reflected light waves, an algorithm is applied to estimate a distance between the sensor and the reflecting surface
Data Source
AI summary
Imaging devices, systems, and methods for determining a distance to an object using light projected from an illumination device are provided. An example method includes: projecting, from an illumination source of the illumination device, projected light having a first wavelength; receiving, at one or more sensors of the illumination device, reflected light having the first wavelength; receiving, at the one or more sensors of the illumination device, emitted light having a second wavelength; determining, by one or more processors, a phase difference between the reflected light and the emitted light; and determining, by the one or more processors, the distance to the object based at least on the phase difference between the reflected light and the emitted light.