940nm 대역 통과 필터

Context: This patent describes an in-cabin safety system for vehicles, specifically combining a Driver Monitoring System (DMS) and an Occupant Monitoring System (OMS).

Usage of Filter: The bandpass filter is used in front of the camera sensors to exclusively pass 940nm infrared light emitted by the system's synchronized LED flashes while blocking other wavelengths (like visible sunlight or 850nm light).

Function: It isolates the 940nm signal to allow the DMS and OMS to operate simultaneously without "crosstalk" or interference, and ensures the illumination remains invisible to the human eye (avoiding the "red glow" associated with 850nm).

Result: Achieves reliable, non-distracting monitoring of both the driver and passengers day and night, even when both systems are firing active illumination pulses.

Context: A Microsoft patent for eye-tracking systems in head-mounted displays (AR/VR) that need to function outdoors.

Usage of Filter: The bandpass filter is tuned to 940nm to take advantage of the atmospheric "water absorption band."

Function: Sunlight causes massive interference in the 800-850nm range, but the atmosphere absorbs distinct bands of sunlight at 940nm. The filter blocks the "noisy" solar spectrum while passing the 940nm LED light reflected from the user's eye.

Result: Enables robust eye-tracking performance in bright outdoor environments where standard sensors would otherwise be blinded by the sun.

Context: A LiDAR system designed to detect objects by emitting laser pulses and measuring their return time.

Usage of Filter: The system uses a narrow bandpass filter (<5nm bandwidth) centered exactly on the 940nm wavelength.

Function: Similar to the eye-tracking patent, this filter utilizes the "solar blind" effect. It blocks background solar radiation (which is naturally attenuated by atmospheric water vapor at this specific wavelength) while allowing the system's own 940nm laser pulses to pass through to the detector.

Result: significantly improves the Signal-to-Noise Ratio (SNR) of the LiDAR, allowing for longer detection ranges and higher accuracy even in broad daylight.