An optical configuration for measuring a difference in refractive index
between a first sample and a second sample comprises partitioned first and
second optical interfaces symmetrically illuminated by an illumination
beam to provide first and second partial beams defined by the refractive
index of the first and second samples, respectively. A linear scanned
array is aligned in a meridional plane of the optical configuration for
detection purposes, and an optical multiplexor is provided upstream of the
linear scanned array for receiving the first and second partial beams and
defining first and second optical channels carrying optical signal
information corresponding to the first and second partial beams. The
optical multiplexor switches between optical channels, such that the
linear scanned array detects either the first or second optical channel at
a given time. Thus, differential measurements are possible using a single
linear array. Embodiments for critical angle and surface plasmon resonance
refractive index measurements are disclosed. The disclosure also relates
to methods for measuring a difference in refractive index between a first
sample and a second sample in accordance with the described optical
configuration embodiments.
