Applications Guide
Modline 5
149
Viewing at furnace exit
Figure 88: Solving Common Reflection Problems
8.9
Use of Mirrors
In rare situations it may be difficult, if not impossible, to position the Sensor for a direct view of the
desired target surface. You may then find it necessary to view the target indirectly by means of a mirror.
Mirror material, surface area and alignment are critical in this application. In all cases the mirror must
be a first surfaced (front surfaced) mirror, and ideally it should be a perfect reflector at the operating
wavelength of the Sensor.
A first surfaced, flat, aluminized or gold mirror may be used for all Sensor Series except Series 5R. This
type of mirror is readily available from optical supply houses. For 5R Sensors, the mirror must be a front
surfaced, gold coated mirror. (Aluminum coated mirrors show a small coloring effect in the Series 5R
spectrum, causing the instrument to read low. This low reading error may be corrected by the E-Slope
adjustment, but a gold mirror is preferred.).
Sensor Lens
Workpiece
Furnace Roof
Cooled Shield
Problem: Sensor Lens ″sees″ reflections of furnace
roof or wall.
Solution 1: Change viewing angle.
Sensor Lens
Solution 2: Install shield to block reflection.
Sensor Lens
Sensor Lens
Workpiece
Furnace
Problem: Sensor Lens ″sees″ reflections from hot
of furnace roof.
Solution: View through sight tube with tip spaced close to
surface of workpiece.
Sight Tube
Sensor Lens
Cautions: 1. I.D. of sight tube must be wider than Cone of Vision along entire length. (See Section
2. Sight tube walls may radiate infrared if furnace atmosphere is very hot. May require cooled sight tube. Consult
IRCON for recommendations.
Viewing through furnace roof or wall
