Tools of the trade - Vol 18 - Thorlabs - #601

Near IR Achromatic Doublets

1

Spherical doublet lenses have been corrected for various aberrations. One way of displaying the theoretical level of correction is through plots of wavefront error and ray traces to determine spot size. In the example chart shown below on the left, a plot of wavefront at the image plane reveals information regarding aberration correction. In the example lens the wavefront error is theoretically on the order of 3/100 of a wave. This tells us that the optical path length difference (OPD) is extremely small for rays going through the center of the lens and at nearly full aperture.

In the example chart shown below on the right, a ray trace for spot size at the image plane is shown. In the near IR achromat used in the example, 706.5nm, 855nm and 1015nm, the design wavelengths, have each been traced through the lens and are represented by different colors. The circle surrounding the distribution of ray intercepts represents the diameter of the Airy disk. If the spot is within the Airy disk the performance of the lens is typically considered to be diffraction limited. Since the spot size is

drawn using geometric ray tracing, spots much smaller than the Airy disk are not achievable due to diffraction.

This type of information is available for all of our achromatic doublets on our website at www.thorlabs.com.

H 35 RC

JTE 206

RC25H-200-E

TUE TUL 15 200;

0.8550 MICRONS RT 0.0000 DEG

=ERK TO VALLEY 15 0.0307 IJRUE5.

5URFRCE : II1RGE

RC25H-200-E

TUE JUL 15 2003 UNITS EIRE MICRONS

=IELD 1

^N5 RADIUS H, H"31

3E0 RADIUS 6.915

ÌIRY DIRM 1S.2H

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