Sigma LBA-710, LBA-714PC, LBA-300, LBA-712, LBA-708, LBA-500PC, LBA-700, LBA-400 manual Divergence

Hints: Use Drawn apertures and avoid Auto apertures when making Top Hat measurements. Use Percent of Peak as your beam width method. Typical Percent of Peak Clip% settings are 50%, 80%, and 90%.

Refer to the Top Hat section in Chapter 6 for additional details.

3.2.6.8Divergence

Two methods are provided for making divergence measurements of your laser beam. The preferred technique is the Focal Length method. The Focal Length method can produce a valid result anywhere in the laser beam path and only requires one measurement.

A second technique, referred to as the Far-Fieldmethod, is also provided. The Far-Fieldmethod is only valid if you are sampling your laser in the far field. It will give incorrect results if you are measuring your laser in the near-field. The Far-Field method requires you to make two sets of beam width measurements a known distance apart.

See Divergence in Chapter 6 for details regarding how these two methods are computed.

3.2.6.8.1Focal Length Divergence Measurements

The Focal Length method requires you to bring your laser beam to a focus using either a focusing lens or mirror. You must place your camera detector at the focal point of the focusing optic. One-half to one-meter focal lengths are typical, as they will keep the focused spot size large enough to be measured with a CCD camera.

Check the Divergence box and select Focal Length in the drop down edit control. Enter the Focal Length of your optical system in meters. The divergence results will be computed for both the X and Y or the Major and Minor beam widths, depending upon Elliptical being enabled.

Figure 26

The Focal Length method is most appropriate for lasers that exhibit small angular divergences. For larger divergence angles, like those seen with laser diodes, the Far-Fieldmethod is much more accurate.

Operator’s Manual 72 LBA-PC