  A non-invasive, in-situ calibration method for Total Internal Reflection
Microscopy (TIRM) based on optical tweezing is presented which greatly expands
the capabilities of this technique. We show that by making only simple
modifications to the basic TIRM sensing setup and procedure, a probe particle's
absolute position relative to a dielectric interface may be known with better
than 10 nm precision out to a distance greater than 1 $\mu$m from the surface.
This represents an approximate 10x improvement in error and 3x improvement in
measurement range over conventional TIRM methods. The technique's advantage is
in the direct measurement of the probe particle's scattering intensity vs.
height profile in-situ, rather than relying on calculations or inexact system
analogs for calibration. To demonstrate the improved versatility of the TIRM
method in terms of tunability, precision, and range, we show our results for
the hindered near-wall diffusion coefficient for a spherical dielectric
particle.
