Comparison of beam homogenizers for use in a refractive laser surgical system

Abstract

Consistent spatial distribution of ultraviolet energy from pulse to pulse is a key element for successful refractive surgical results. Tissue ablation is a nonlinear process; however, a uniform intensity profile is a desirable characteristic in an adjustable imaging-aperture system. At the same time, it is necessary to minimize energy loss as the beam passes though the aperture. Using these parameters, the spatial integration performance of two refractive lenslet arrays ─ one with square elements and the other with hexagonal elements ─ was compared. A breadboard optical system was constructed to evaluate each lenslet array, and data were collected with a beam intensity profiler. Transmission of both arrays was measured by collecting through-focus beamlet propagation at various distances. The transmission measurements were scaled to compensate for the difference in beamlet overlap diameter resulting from the unequal size of the lenslet elements. The transmission of the lenslet arrays was nearly equivalent, but the square lenslet array provided a more uniform intensity profile. No benefit was seen in fitting a hexagon instead of a square onto the circular iris.Consistent spatial distribution of ultraviolet energy from pulse to pulse is a key element for successful refractive surgical results. Tissue ablation is a nonlinear process; however, a uniform intensity profile is a desirable characteristic in an adjustable imaging-aperture system. At the same time, it is necessary to minimize energy loss as the beam passes though the aperture. Using these parameters, the spatial integration performance of two refractive lenslet arrays ─ one with square elements and the other with hexagonal elements ─ was compared. A breadboard optical system was constructed to evaluate each lenslet array, and data were collected with a beam intensity profiler. Transmission of both arrays was measured by collecting through-focus beamlet propagation at various distances. The transmission measurements were scaled to compensate for the difference in beamlet overlap diameter resulting from the unequal size of the lenslet elements. The transmission of the lenslet arrays was nearly equivalent,...