1g a dis-
Thus the
ulated by
e crossed
ne to the
n the di-
machine,
ight par-
rmation.
It can be
angle can
‘es across
' the ma-
been de-
d by the
tool and
nation of
inge pat-
the main
en tilted
| became
tudy the
1ces from
gles that
ange the
tilt of the
t to mag-
ponds to
the head
n the ref-
e for the
that only
re we ex-
ifference
made an-
came three
h hologram
uld hardly
nee of the
caused by
Fig. 8. The sandwich hologram of Fig. 7 was tilted so that the de-
formation of the knee could easily be studied. The closely spaced
fringes that were moved from the knee to the reference surface could
no longer be resolved because of the large speckles. However, the
magnitude, direction, and sign of knee tilt could be evaluated from
the tilt of the hologram.
Fig. 9. The sandwich hologram of Fig. 7 was tilted to make possible
a study of the deformation of the machine head.
other change too because during our earlier experiment
we found that the sandwich tilt needed to eliminate the
fringes on the table was uncomfortably large. By
making the separation larger between the two emulsions
of the sandwich hologram (d of Fig. 1, Ref. 5) the tilt
angle could be kept smaller. The two holograms were
placed with their emulsions outward instead of forward,
and moreover we added a third glass plate (hologram
plate with the emulsion removed) between the two
plates to provide extra separation.
Fig. 10. The load was finally increased still more so that the fringes
on the knee could not be resolved at all.
Fig. 11. After some tilt of the sandwich hologram of Fig. 10, however,
fringes appeared on the knee, and further tilt revealed its
deformation.
Figure 7 shows the result when no tilt has been in-
troduced to this new sandwich hologram. The tilt of
the knee is now so large that the fringes could not quite
be resolved. However, after a tilt of the sandwich ho-
logram during reconstruction fringes appeared on the
knee, and after some further tilt the number of fringes
crossing it was set at a minimum (Fig. 8). Now it is
possible to measure the deformation of the knee of the
milling machine in spite of this deformation being so
small that it only caused about eight of the about 125
September 1977 / Vol. 16, No. 9 / APPLIED OPTICS 2527