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The ITL200 is an infinity-corrected tube lens designed for use with Plan Fluorite Visible Imaging Objectives, specifically our line of Nikon objectives. The tube lens has an effective focal length of 200 mm and is ideal for applications such as imaging onto a CCD camera. The lens features an apochromatic design consisting of two doublet lenses to correct lateral and axial chromatic aberration across the entire field of view in the visible range. The lens will have better overall aberration correction than a standard achromat, especially off axis. The lens also has diffraction-limited performance to field number 25 for visible wavelengths. The lens is AR coated to improve performance for visible wavelengths; please see the Specs tab for a plot of the transmission. For those interested in building their own tube lens with a focal length of 180 mm, we also carry Ø2" AR-coated achromatic doublets, specifically AC508-180-A and AC508-180-A-ML.
An objective lens creates an image of an object at infinity; put another way, the objective forms parallel bundles of light rays for each position on the object.The tube lens is designed to refocus these parallel bundles onto the active area of a detector, as illustrated in the diagram to the right. In the diagram, the blue rays originate from the object on the optical axis, while the red rays originate off-axis. Since the rays from the objective are in parallel bundles, the tube lens can be located anywhere from 70 to 170 mm from the shoulder of the objective for best results. If the lens is closer than 70 mm, the image may suffer from aberrations, and if the tube lens is further away than 170 mm, the scan lens will be overfilled.
The ITL200 tube lens can also be paired with the CLS-SL Visible Scan Lens. In this configuration, the tube lens will relay the scan plane of a laser scanning imaging system to the back aperture of the imaging objective.
The M38 x 0.5 external thread on the ITL200 can be easily converted to SM2 (2.035"-40) threading using the SM2A20 adapter, which enables the construction of an optical system consisting of a scan lens and a tube lens using Thorlabs' standard SM2 lens tube components.