740nm Bandpass Filter

740nm light is in the near-infrared spectrum, offering good penetration through certain materials and minimal interference from visible light.

  • Application 1: In biomedical applications, it can be used in pulse oximeters to isolate 740nm light for measuring oxygen saturation in blood by penetrating tissue while minimizing ambient light noise.
  • Application 2: In spectral analysis equipment, the filter enables precise detection of substances that absorb or reflect strongly at 740nm, such as specific chemicals in environmental monitoring or agricultural quality control.
  • Application 3: For night vision or surveillance systems, the filter blocks unwanted wavelengths, allowing devices to capture clear 740nm near-infrared imagery in low-light conditions without visible light interference.
  • US8255040B2 - Micro vein enhancer

    US8255040B2 - Micro vein enhancer

    Context:This patent describes a "Micro vein enhancer," a handheld medical imaging device used to locate veins beneath a patient's skin. The device simultaneously projects two lasers: a visible red laser (638nm) to display the map on the skin's surface, and a near-infrared laser (740nm) to penetrate the tissue and detect the veins.

    Usage of Filter: The 740nm bandpass filter (or a selective photodiode assembly functioning as such) is placed in the optical return path, directly in front of the device's photodetector (PD).

    Function: The filter's function is to block the high-intensity 638nm visible light used for projection, as well as ambient room light, while selectively passing only the 740nm infrared light that has reflected off the patient's tissue.

    Result: This allows the device to clearly "see" the hemoglobin in the blood (which absorbs 740nm light) without interference from the display laser. The system then processes this high-contrast signal to project a real-time, accurate map of the veins directly back onto the patient's skin, assisting clinicians in venipuncture.

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