Collection: IR Blocking Filter

Optical filters for IR blocking come in various types and play a crucial role in various applications by selectively stopping infrared (IR) radiation while allowing other wavelengths to pass through. Here's an overview:

Types of IR Blocking Filters:

    • Shortpass Filters: These filters block longer wavelengths, primarily focusing on near-infrared (NIR) and mid-infrared (MIR) wavelengths, while transmitting visible and some ultraviolet (UV) light. Common cutoff wavelengths include 780nm, 850nm, and 1000nm, depending on the specific application.

    • Longpass Filters: These filters block shorter wavelengths, mainly visible and UV light, allowing NIR and MIR radiation to pass through. Common cutoff wavelengths range from 700nm to 1200nm, depending on the desired IR transmission range.

    • Hot Mirror Filters: These are specialized filters designed to reflect NIR and MIR wavelengths while transmitting visible light. They are often used in projectors, slide scanners, and other illumination systems to prevent heat buildup and damage from IR radiation.

    • Dichroic Filters: These filters combine functionalities, reflecting specific IR wavelengths while transmitting others. They offer compact solutions for multiple functions like blocking IR and visible light simultaneously.

Wavelength Selection:

The choice of filter and its cutoff wavelength depends on your specific application and desired outcome. Here are some examples:

    • Protecting sensors: In cameras and other devices with visible or UV-sensitive detectors, shortpass filters below 780nm or 850nm are used to block harmful IR radiation that can damage the sensor.
    • Machine vision: In applications like inspecting objects for defects based on their NIR reflectance, shortpass filters around 1000nm might be used to isolate the relevant NIR information while blocking visible light.
    • Medical imaging: Certain medical imaging techniques utilize visible or UV light, and longpass filters above 700nm or 800nm can block unwanted IR radiation for clearer images.
    • Astronomy: Astronomers use specialized filters to isolate specific IR emissions from stars and other celestial objects for scientific study. Filters range from near-IR (e.g., J, H, K bands) to mid-IR (e.g., L, M, N bands).

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