Abstract

An apparatus adapted for rotating a beam of radiation to obtain azimuthal and radial time averaging of the intensity distribution incident onto a workpiece is disclosed. The apparatus includes a housing adapted for rotation about a centerline axis, an entrance port and an exit port adapted for transmitting a beam of radiation through the housing, an inverter disposed within an internal passage within the housing and fixedly attached to the housing for rotation therewith includes a first mirror having a reflective surface angularly disposed to the rotation axis adapted for reflecting radiation incident thereon to a second mirror, a second mirror having a reflective surface adapted for reflecting radiation incident thereon to a third mirror having a reflective surface angularly disposed to the rotation axis adapted for passing radiation incident thereon through the exit port. Radiation passing through the housing is rotated about its propagation axis at an angular frequency twice the angular rotation rate of the housing. In one embodiment the third mirror has its centroid displaced from the centerline axis such that each ray in the rotating beam traces out an epicycloid instead of a circle thus averaging out some of the radial variations in the intensity distribution. The effect of spikes, hot spots, or the like in the intensity distribution are effectively time averaged over an interaction area on a workpiece when the rotation frequency is greater than the characteristic response time of the material of the workpiece.

Other References

• J P. Wiley, IBM Technical Disclosure Bulletin, "Constant Path Length Optical Scanner," vol. 15, No. 4, Sep. 1972, p. 1291