Why Choose an Achromatic Cylinder Lens?
Achromatic Cylinder Lenses offer several performance advantages versus traditional cylinder lenses, including superior reduction of spherical and chromatic aberration at the image plane. When used with a LED source, Achromatic Cylinder Lenses are ideal for line generation. Although LEDs are commonly thought to be monochromatic illumination sources, typical LEDs have a FWHM spectral bandwidth of approximately 30nm.
Table 1 compares the line widths of a focused 520nm LED through a variety of achromatic cylinder lenses, and through their standard cylinder lens equivalents. The decreased line width yields higher resolution, increased signal-to-noise, and superior throughput for LED-based scanning devices.
|Table 1: Line widths through 12.5mm diameter cylinder lenses of various focal lengths|
|Focal Length||Achromatic Cylinder Lens||Cylinder Lens|
|75mm||Diffraction Limited (8μm)||45μm|
|100mm||Diffraction Limited (10μm)||34μm|
Figure 1 illustrates the effect of spherical aberration through the PCX cylinder lens. The reduction of chromatic aberration by the achromatic cylinder lens is an added benefit but, in this instance, the greatly reduced spherical aberration results in a much thinner line.