VCSEL Laser Projector Sunlight Rejection for Outdoor Depth Cameras
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Solution Overview
Problem
Active stereo depth cameras face challenges in outdoor operations due to sunlight interference, which causes a low signal-to-noise ratio and washes out the projected intensity pattern, especially when external sources of illumination interfere with the system's operation.
Innovation Solution
The method involves modulating the projection during a portion of the frame period at a modulation frequency that meets eye safety thresholds, switching the wavelength to 940 nm to reduce sunlight interference, and synchronizing exposure times with the projector pulses to enhance sunlight rejection, using a VCSEL laser projector with quantum film sensors for efficient sunlight rejection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the projector emits light in the wavelength range affected by sunlight, then the projected pattern can be detected by the sensor, but sunlight interference causes a low signal-to-noise ratio and washes out the projected pattern
Solution Approach 1:
The patent changes the wavelength parameter of the projected light from conventional 850nm to 940nm. This parameter change allows the system to operate in a wavelength range where sunlight has lower intensity, thereby reducing sunlight interference and improving the signal-to-noise ratio for depth measurement in outdoor environments
2Measurement precision
If the projector increases light intensity to overcome sunlight interference, then the projected pattern becomes more detectable, but eye safety thresholds may be exceeded
Solution Approach 1:
The patent implements periodic pulsed projection at 940nm wavelength with specific duty cycles. By using periodic action instead of continuous high-intensity illumination, the system achieves sufficient pattern detection capability while keeping the average power below eye safety thresholds, thus resolving the contradiction between detection capability and eye safety
Solution Approach 2:
The patent changes the wavelength parameter to 940nm where quantum film sensors have high sensitivity. This allows the use of lower light intensities to achieve the same detection performance, thereby maintaining eye safety while overcoming sunlight interference
3Reliability
If the camera uses conventional wavelength (850nm) for active stereo depth measurement, then the system can operate effectively, but sunlight at this wavelength saturates the sensor and washes out the projected pattern
Solution Approach 1:
The patent changes the operating wavelength from 850nm to 940nm. At 940nm, quantum film sensors maintain high sensitivity while sunlight intensity is significantly lower. This parameter change enables reliable depth measurement capability in outdoor conditions without sensor saturation from sunlight
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 significantly improves the signal-to-noise ratio and pattern detection efficiency, allowing the system to operate effectively outdoors by reducing sunlight interference and maintaining eye safety standards.
Implementation Method 1
using a VCSEL laser projector
Implementation Method 2
quantum film sensors for efficient sunlight rejection
Data Source
AI summary
Techniques related to a method and system of adaptable exposure control and light projection for cameras are described herein.