Depth Camera Infrared Filtering for Sunlight Interference
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Solution Overview
Problem
Existing depth camera systems face difficulties in generating accurate depth images in outdoor sunlight environments due to the interference of infrared light with wavelengths between 800 nm to 900 nm, which affects the sensitivity of silicon-based image sensors.
Innovation Solution
A depth image generating apparatus that band-pass filters infrared light of a first wavelength band (e.g., 1300 nm) and modulates it to a second wavelength band (e.g., 800 nm) for improved sensing efficiency, allowing for accurate depth image generation using existing silicon-based sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an infrared light with wavelength band of 800 nm to 900 nm is used for depth imaging, then the sensing efficiency of silicon-based image sensors is improved, but the depth image acquisition becomes difficult in outdoor sunlight environment due to interference
Solution Approach 1:
The patent extracts and removes the harmful infrared wavelength components (800-900 nm) from the sunlight that reach the sensor, while allowing the desired modulated infrared signal to pass through. This is achieved by placing a band rejection filter in the optical path that specifically blocks the sunlight's infrared band that causes interference, thereby separating the harmful radiation from the useful signal path.
Solution Approach 2:
The patent introduces an intermediary modulation scheme where the infrared LED modulates the emitted light at a specific frequency, and a corresponding bandpass filter with notch filter selectively passes only the modulated signal frequencies while blocking the unmodulated sunlight infrared components. This intermediary frequency-domain filtering acts as a mediator between the strong sunlight background and the weak depth signal.
2Object-affected harmful factors
If an infrared light with wavelength band greater than 900 nm is used, then the sunlight interference is reduced, but the sensor sensitivity deteriorates
Solution Approach 1:
The patent changes the wavelength parameter of the emitted infrared light from the conventional 800-900 nm range to a longer wavelength band greater than 900 nm. This parameter change reduces the overlap with sunlight infrared components while remaining within the detectable range of modified silicon-based sensors, thereby simultaneously reducing sunlight interference and maintaining sensor sensitivity.
3Object-affected harmful factors
If a band rejection filter is used to block sunlight infrared, then the sunlight interference is reduced, but the filter complexity and cost increase
Solution Approach 1:
The patent merges multiple filtering functions into a single integrated optical filter component. The band rejection filter is designed to simultaneously block multiple harmful wavelength bands (800-900 nm and other sunlight infrared components) while passing the desired longer wavelength infrared signal, combining what would otherwise require multiple separate filters into one compact element.
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 the generation of accurate depth images in both indoor and outdoor sunlight environments without the need for separate sensors, leveraging the existing silicon-based image sensor technology.
Implementation Method 1
a filtering unit to band pass filter an infrared light of a first wavelength band among infrared lights received from an object
Implementation Method 2
a modulation unit to modulate the infrared light of the first wavelength band to an infrared light of a second wavelength band
Implementation Method 3
a sensing unit to generate an electrical signal by sensing the modulated infrared light of the second wavelength band
Data Source
AI summary
Provided is a depth image generating apparatus. The depth image generating apparatus may include a filtering unit, a modulation unit, and a sensing unit. The filtering unit may band pass filter an infrared light of a first wavelength band among infrared lights received from an object. The modulation unit may modulate the infrared light of the first wavelength band to an infrared light of a second wavelength band. The sensing unit may generate an electrical signal by sensing the modulated infrared light of the second wavelength band.