940nm Bandpass Filter

940nm light is in the near-infrared spectrum, invisible to the human eye, with good penetration through certain materials and minimal interference from ambient visible light.

  • Application 1: In security surveillance systems, to enable night vision cameras to capture clear images in low-light conditions by isolating 940nm infrared light emitted from IR LEDs, blocking visible light and other unwanted wavelengths.
  • Application 2: In biometric devices (e.g., iris or vein recognition), to filter out ambient light and focus on the 940nm wavelength that effectively penetrates the skin surface to illuminate and capture detailed vascular or ocular patterns for accurate identification.
  • Application 3: In remote control systems or infrared data transmission devices, to ensure reliable signal reception by allowing only the 940nm bandpass light (commonly used in IR transmitters) to reach the sensor, minimizing noise from other infrared sources or environmental light.
940nm Bandpass Filter
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Center Wavelength (nm)
FWHM (nm)
Optical Density(OD)

Filter

Center Wavelength (nm)
FWHM (nm)
Optical Density(OD)
US 11,140,334 B2 - 940nm LED Flash Synchronization for DMS and OMS

US 11,140,334 B2 - 940nm LED Flash Synchronization for DMS and OMS

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.

US 10,401,956 B2 - Infrared Eye-Tracking In High Ambient Light Conditions

US 10,401,956 B2 - Infrared Eye-Tracking In High Ambient Light Conditions

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.

US 11,280,884 B2 - LiDAR Instrument and Method

US 11,280,884 B2 - LiDAR Instrument and Method

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.

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