An apochromat uses multiple glass elements with different dispersion properties to eliminate chromatic aberration across a broad spectrum. Unlike simpler lenses that only correct two colors, it aligns red, green, and blue light precisely while also controlling spherical aberration. This makes it the standard for broadband laser applications and high-end color imaging where focal shifts would ruin the output.
If you pump the supercontinuum through that standard achromat, the blue edge will focus millimeters away from the red, so buy an apochromat.
Also heard as
- APO
Do not mix it up with
- Achromat: An achromat corrects two wavelengths and leaves some residual color error, whereas an apochromat corrects three wavelengths for a much sharper broad-spectrum focus.
Related terms
Achromat
An optical assembly designed to minimize chromatic aberration.
Chromatic dispersion
The change of refractive index with wavelength, which separates colors in prisms and spreads pulses in time.
Spherical aberration
An optical defect where light rays passing through the edge of a lens focus at a different point than central rays.