HP 5528A

Model 5528A
Appendix A: Principles of Operation
The Air Sensor's humidity output is an analog vo ltage that is controlled by a three - position switch
on the side of the sensor's housing. The Measurement Di splay unit c onvert s this voltage into a
digital value thilt it us es in its V. O.l. calculation.
10757 Material Sensor
The Material Sens or 's output is an analog voltage that is c ontrolled by a temperature-sensitive
element in
Ihe sensor. The Meas ur ement Di splay unit converts this amllog voltage to a diMi t al
voltage that iI in corporates into its maTer i al expans ion calcula tion .
10766A Linear Interferometer
The Interferometer used In Distance and Velocity measurements contains a polarized beam
sp litter. This is represented by a diagonal line in Figure A-2 . The polarized beam sp li tter wilt
reflect the ft component of the laser beam and let the f2 component pas s through . The best way
to vi sualize this is to imagine that the polarized beam s plitter is a vertical picket fence that lets the
vertically polarized frequency component through, but reflec ts the hori z ontally polarized
frequency
component .
10767 A Linear Relroreflector
The Retroreflec tor is an optically ground and polished glass trihedral ( thrce -s urface) pri sm
(somctimcs ca lled a " cube corner" ). It reflec ts the la ser beam back along a lin e parallel to the
original
beam, but off s et from it by twice thc di stance at which the incoming beam is offset from
the corner apex.
10770A Angular Interferometer
The Angular Int erferometer used in Angular and Flatne ss measurements is basically a linear
Inte rf erometer with a Ream Bender located above it (sec Figure A-J).
10771A Angular Reflector
The Angular Reflec tor contains two Retroreflectors s pa ced a precisely-kno wn di stance apart.
10774A and 10775A Straightness Interferometer and Reflector
The Straightn ess Interferometer and Reflector have the same instrument number because they
are
a matched pair. They must be matchcd to have the Reflector return the two frequency
components of
the Laser beam directly back into the I nterferometer .
The
Interferomter splits the two -frequency beam from the La s er Head into its two c ornponent
parts, with eilch part leaving the Interferometer along a specific, precis ely-controlled pa th. This is
possible bec au se the Interferometer contains a Wollas ton prism. which ha s a diffe r ent index of
refraction for ea ch of the two perpendicular po larilies in the la ser beam. The Int erferometer can
be
turned , so the plane established by the two exit path s can be rotated about the in c oming laser
beam.
A·3