Multi-passband Optical Filter for Depth Sensing Noise Reduction
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Solution Overview
Problem
Current distance sensors with RGB+IR technology face challenges in simultaneous two-dimensional and three-dimensional image acquisition due to wide infrared bandpass filters, which allow noise from visible wavelengths to interfere with invisible wavelength detection, affecting three-dimensional depth mapping accuracy.
Innovation Solution
Incorporating a bandpass filter with multiple passbands in the light receiving system, allowing separate transmission of visible and invisible light to specific photodetectors, ensuring infrared light is only received by IR detectors while visible light is captured by RGB detectors, thereby improving signal-to-noise ratio and depth sensing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a wide infrared bandpass filter is used to allow infrared light transmission, then infrared signal reception is improved, but visible light noise interferes with invisible wavelength detection, degrading measurement precision
Solution Approach 1:
The filter is divided into multiple passbands: a first passband for visible light wavelengths and a second passband for infrared wavelengths. This segmentation allows different wavelength ranges to be transmitted separately, enabling the system to isolate infrared signals from visible light noise while maintaining detection precision.
Solution Approach 2:
Different regions of the filter have different transmission properties tailored to specific wavelength ranges. The first passband is optimized for visible light transmission to RGB photodetectors, while the second passband is optimized for infrared transmission to IR photodetectors, ensuring each detector receives only its designated wavelength range without interference.
2Measurement precision
If separate filters are used for visible and invisible light, then signal-to-noise ratio is improved, but device complexity increases
Solution Approach 1:
Multiple passbands for different wavelength ranges are integrated into a single filter structure. This combined filter performs the function of multiple separate filters simultaneously, maintaining high signal-to-noise ratio by separating visible and infrared transmission pathways while avoiding the complexity of multiple discrete filter components.
Solution Approach 2:
The single filter serves multiple functions: it transmits visible light to RGB photodetectors through the first passband and transmits infrared light to IR photodetectors through the second passband. This multi-functional design eliminates the need for separate dedicated filters for each wavelength range, simplifying the overall device architecture.
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 configuration enables simultaneous and accurate two-dimensional image capture and three-dimensional depth sensing by isolating infrared and visible light pathways, enhancing the signal-to-noise ratio and reducing interference, thus improving the overall performance of distance sensors.
Implementation Method 1
a second passband of the plurality of passbands is configured to allow transmission of light having a second set of wavelengths that includes at least one wavelength that is invisible to the human eye
Implementation Method 2
a second subset of the plurality of photodetectors is configured to detect light having wavelengths that are invisible to the human eye
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
An example apparatus includes a light projecting system, a light receiving system, and a controller. The light projecting system projects beams of light of a wavelength that is invisible. The beams form a pattern on a surface when the beams are incident upon the surface. The light receiving system acquires an image of the pattern on the surface. The controller calculates a distance to the surface based on the image. The light receiving system includes a lens, an imaging sensor, and a bandpass filter. The imaging sensor includes a first subset of photodetectors sensitive to wavelengths of light that are visible and a second subset of photodetectors sensitive to the wavelength of light that is invisible. The bandpass filter includes a first passband whose range corresponds to the wavelengths of light that are visible and a second passband whose range corresponds to the wavelength of light that is invisible.