A direct type backlight unit includes a metal housing having a base, at least one metal supporting pin and a buffer element. A spectrum corresponding to an unknown sample is perturbed in various ways, and each perturbed spectrum is compared with the spectrum of a known or reference substance. The handle assembly is sized and configured to receive the first clip assembly or the second clip assembly. The trocar and safety guide may then be disposed, the sharp end of the trocar remaining safely covered by the receiver.