In an optical measurement probe of the type which incorporates a window
configuration suited to on-line process control and other applications
this invention provides an improved technique for bonding such a window to
probe body or process vessel. In general terms, the improvement arises
through the use of a compression ring around the bonding area to maintain
a consistent seal. In terms of apparatus, a hollow probe body terminates
in a distal end having a flanged portion with an inner and outer wall that
extends back into the body. The outer wall of the window is sealed against
the inner wall of the flanged portion, with compression material urged
against the outer wall of the flanged portion to pressurize the seal
between the window and the inner wall of the flanged portion. In the
preferred embodiment, the compression material is ring-shaped and exhibits
substantially the same thermal expansion coefficient as the window. In the
case where a sapphire window is used, titanium or Invar may be used for
the compression material. The window may be generally cylindrical though,
in the preferred embodiments, cork-shaped or spherical window are used.
