A new type of normal incidence scanning reflectometer is designed and
constructed. In the system design, instead of using a reference reflec
tive sample or the optical path adjustment methods as in traditional d
esign, we use a fused quartz M-type prism to split the beam of inciden
ce light into two beams in a total internal reflection configuration.
The spot sizes, intensities, and spectral responses of these two light
beams, therefore, are identical. One reference beam goes directly to
the detector. Another sampling beam goes to the sample and is measured
by the same detector after beam reflection. A metal disk having three
holes is driven precisely by a stepping motor and is used to control
the reference and reflection beams as well as the background signals,
which are measured in sequence. In terms of the three signals, the abs
olute reflectivity of the sample at a certain wavelength can be determ
ined immediately using the computer. The system is controlled automati
cally by the computer with a working wavelength range from 400 to 800
nm. The incidence angle is fixed and equals about 5 deg. The details o
f the system design, optical configuration, and error reduction are gi
ven and discussed. The measured spectral results of the reflectivity f
or a few testing samples are also given, and are shown to be in good a
greement with those measured by other optical methods. The designed sy
stem, however, is simpler and can be used in many optical studies. (C)
1997 Society of Photo-Optical Instrumentation Engineers.