For many applications, such as holography, spatial intensity variations in the laser beam are unacceptable. Using these precision pinholes in conjuction with precision positioning and focusing equipment such as our KT310 Spatial Filter System creates a "noise" filter, effectively stripping variations in intensity out of a Gaussian beam. Please see the Tutorial tab for more information on spatial filters.

If you do not see what you need in our stocked offerings below, it is possible to special order precision pinholes that are fabricated from different substrate materials, have different pinhole sizes, incorporate multiple holes in one foil, or provide different pinhole configurations. Customized pinhole housings are also available. Please contact technical support to discuss your specific needs.

Principles of Spatial Filters

Figure 1 - Spatial Filter System

The input Gaussian beam has added to it spatially varying intensity "noise." When a beam is focused by an aspheric lens, the input beam is transformed into a central Gaussian spot (on the optical axis) and side fringes, which represent the unwanted "noise" (see Figure 2  below). The radial position of the side fringes is proportional to the spatial frequency of the "noise".

Figure 2

By centering a pinhole on a central Gaussian spot, the "clean" portion of the beam can pass while the "noise" fringes are blocked (see Figure 3  below).

Figure 3

The diffraction-limited spot size at the 99% contour is given by:

where λ = wavelength, ƒ=focal length and r = input beam 1/e² radius.

A pinhole that is approximately 30% larger than the diffraction-limited spot size should be chosen to allow the focused Gaussian spot to pass while blocking the "noise" fringes that are shifted off axis. If the pinhole is too small, the beam will be clipped, but if it is too large, additional noise will get through the pinhole.

For more information on creating a spatial filter system for your application, please see the Tutorial  tab on the Spatial Filters Systems page.