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LWIR Achromatic Doublets Optimized for 8 - 12 µm
f = 75 mm
f = 50 mm
Each mount includes an engraved arrow
These AR-coated, air-spaced achromatic doublet lenses provide excellent transmission in the 8 - 12 µm range (surface reflectance for each coating can be seen in the graph to the right). They incorporate two AR-coated lenses, one with a zinc selenide substrate and another with a zinc sulfide substrate. Each achromatic doublet on this page has three design wavelengths: 8 µm, 10 µm, and 12 µm. By optimizing the design for these three wavelengths, the focal shift across the 8 - 12 µm range will be minimized (see the graphs below for details), providing excellent on-axis performance.
Thorlabs' LWIR achromatic doublets are pre-mounted in engraved Ø1" outer diameter mounts, making it easy to incorporate these optics into your setup. Each engraving includes the part number, AR coating range, focal length, an arrow indicating the direction of light propagation to collimate a point source, and an infinity symbol denoting that this lens has an infinite conjugate ratio (i.e., if a diverging light source is placed one focal length away from the flat side of the lens, the light rays emerging from the curved side will be collimated).
Note: We do not recommend disassembly of these lenses, as this may affect performance.
Note: The optical coating on these lenses contains thorium tetrafluoride (ThF4) due to its superior performance in the IR. This is a radioactive material, and thus, these lenses should be handled with care. Additionally, ZnSe is a hazardous material. For your safety, please follow all proper precautions while handling any ZnSe products, including wearing gloves and thoroughly washing your hands afterward.