Microlens arrays are now widely used in a variety of astronomical instrumen
ts that require high performance. This paper describes the applications of
microlenses in astronomical spectroscopy and discusses the necessary perfor
mance requirements. A variety of optical tests, including high dynamic rang
e point-spread function measurements and determination of encircled energy,
were developed to characterize the performance of a variety of lenslet arr
ays. Results are presented that indicate the best types of lenslet array fo
r use for astronomical spectroscopy.