Mounting And Fixturing; Operational Verification Check - Agilent Technologies 5517B Operation And Service Manual

2-32. Mounting and Fixturing

2-33. Heat Flow Considerations. The laser tuning technique of the HP 5517B/C/D requires efficient heat exchange
with the ambient. Heat flow is primarily through the base of the laser head assembly to the surrounding
environment. An external heat sink is not required but free air circulation around the laser head will ensure good
performance.
2-34 In cases where vertical mounting of the HP 5517B/C/D is desired, care should be taken to minimize laser beam
disturbances due to air turbulence caused by the HP 5517B/C heat exchange. It is most important to prevent
differential effects which can occur due to turbulence in the beam path between a polarizing beam splitter and a
retroreflector or plane mirror Differential turbulence causes fluctuations in the optical path length difference that is
being measured. Both differential and common mode turbulence can cause fluctuations in alignment by bending the
light beam Common mode turbulence is turbulence that is present in the beam path between the HP 5517B/C and a
polarizing beam splitter. In either case some amount of noise can be present in the interferometer measurement due
to turbulence.
2-35 If interferometer components (optics) are mounted very close to the HP 5517B/C such that the operating
temperature of the optics are affected, it is recommended that alignment and operation of the interferometer be
performed after the HP 5517B/C has been running for a sufficient period of time to allow thermal equilibrium to be
established, in well ventilated installations, one hour of running time should be sufficient When enclosures are used
and the ambient temperature is changed by several degrees (Celsius) by the HP 5517B/C. thermal equilibrium is not
established as quickly and the laser should be run for a longer period of time
2-36 Mounting. Mount the laser head by means of the three slotted tabs that extend outward from the bottom edges
Figure 2-9
of the unit (refer to
surface in any fashion that will not transmit stresses to the main enclosure and, consequently, to the laser tube or
printed-circuit assemblies. If necessary, the tabs can be removed and the unit mounted on a flat surface with 4 mm
machine screws; use the same tapped holes that are used to secure the tabs, ensuring that the mounting method
does not stress the base casting and that the screws do not penetrate the base casting more than 7 mm
2-37 Beam Alignment. Rotate the turret at the front of the laser head so that the beam exits through the large
aperture DO NOT STARE DIRECTLY INTO THE BEAM APERTURE Presence of the red laser beam can be
verified by placing a piece of paper in the beam path and observing the beam reflection on the paper
a. a Aligning the optical components is easiest if all legs of the total beam path are in the orthogonal coordinate
system of the machine; i.e., all beam paths should be parallel to two planes and perpendicular to the third
(For specific procedures, see the HP 5527A Designers Guide or the HP Laser and Optics User's Guide )
b. You should align the laser tube to the coordinate system before any optics are installed in the beam path.
First, autoreflect the laser beam off a plane mirror referenced to the machine's orthogonal coordinate
system, then pitch, yaw, and translate the laser head until the beam is suitably positioned with respect to
the mounting holes for the optics and is parallel to the measurement paths. Shimming the feet may be
necessary.
c. c.The optical components of the laser transducer system must now be aligned so that the laser beam strikes
the photodetector of the receiver (HP Model 10780B,C/F). Refer to the HP 10780B,C/F Receiver
documentation and applicable laser transducer system manuals (HP Laser and Optics User's Manual) for
further alignment information.
2-38 Pointing Stability. The angle at which the laser beam exits the HP 5517B/C can change from turn-on through
the time when the HP 5517B/C/D and its surroundings reach thermal equilibrium
2-39. The HP 5517B/C/D should not be exposed to ambient temperature changes greater than ±5° Celsius during
operation to keep pointing stability variations to a minimum during interferometer measurements.

2-40. OPERATIONAL VERIFICATION CHECK

2-41. Refer to Section IV, Performance Tests.
for exact locations and dimensions). The mounting tabs may be secured to the work