Achromatic Doublet Optic

With the possibility of the Harsh Environment Lens system not being compatible in a vacuum environment, the other, more challenging option, is to use an achromatic doublet. There are a lot of achromatic lenses available from Edmund, giving us almost unlimited choice in optical configuration. The page on these lenses is here. Further information is available here.

Achromatic lenses have two optical components cemented together to form an achromatic doublet which is designed to correct for on-axis spherical and chromatic aberrations. The lenses from Edmund Optics are available with a single layer MgF2 coating or a broadband multi-layer coating for the visible spectrum. All dimensions are in millimetres.

The two elements composing an achromatic lens are paired together for their ability to correct the color separation (dispersion) inherent in glass. Without chromatic abberations, achromatic lenses offer the best option for polychromtic imaging.

For use with the table, the picture below illustrates the dimensions in the table:

lensdiagram.jpeg

Figure 1: The dimensions of the achromatic lenses in Edmund Optic catalogue

Likely candidates for the lens include:

Description Dia. (mm) E.F.L. (mm) Back F.L. (mm) C.T.1 (mm) C.T.2 (mm) E.T. (mm) Radius R1 (mm) Radius R2 (mm) Radius R3 (mm) Glass Type MTF Curve Stock Number Price

Table 1: Table containing dimensions for likely lenses (There are loads of lenses to choose from, I have to trawl through te list yet)

To obtain the best choice of lens, one must be selected using criteria set by the detector. It is likely that the maximum dimensions parallel to the imaging plane will be set by the detector. The lens must be wide enough to produce an image over the entire area of active pixels of the detector chip, this wuill also be a large factor affecting the length of the optical path length.

From Edmund you can obtain what is known as a Prototype kit, which basically lets you put together two achromat lenses to make an optical system. It's put together as shown:

doubleproto.jpeg

Figure 2: Housing set up available from Edmund Optics

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