Plane Mirror - HP 5501A Operating And Service Manual

The minimum power at the receiver must be four microwatts, and the guaranteed minimum
power out of the laser is 120 microwatts, so the minimum allowable transmission factor is
(4/120)2 = 0.0011. Some typical transmission factors for transducer optical modules are a s
follows (these are worst-case numbers, which must be used for loss computation):
33% Beam Splitter 33% Side
33% Beam Splitter 67% Side
50% Beam Splitter each Side
Linear Interferometer7
Retroreflector
Retroref lector
Single-Beam Interferometer7
Beam Bender
Plane Mirror Interferometer*
Beam Splitter
Plane Mirror Converter
?This refers to the beam splitter only. The attached retroreflectors must be considered as a
separate component (see example below).
*The plane mirror interferometer is listed as 10706A. This, however, consists of a 10581A,
10702A7, and two 10703A's. The transmission factor for this device would therefore be
(1.00)
X
(0.80)
X
(0.80)
X
(0.85)
=
0.54.
As an example, consider a typical installation with three axes (see Figure 2-32). Assume linear
interferometers on each axis, good optical alignment, and comparable path lengths. Assume
that the three axes have the following components:
Axis A : 10700A (33%), 10707A, 10702A, 10703A (2)
Axis B:
10700A (67%), 10701A, 10702A, 10703A (2)
Axis C: 10700A (67%), 10701A, 10702A, 10703A (2)
The transmission factors are, for each axis:
Axis A:
(0.08)
X
(1.00)
X
(1.00)
X
(0.80)
X
(0.80)
=
0.0512
Axis B: (0.38)
X
(0.19)
X
(1.00)
X
(0.80)
X
(0.80) = 0.0462
Axis C: (0.38)
X
(0.19)
X
(1.00)
X
(0.80)
X
(0.80)
=
0.0462
Here,
B
and C are worst-case (net product is smallest) but still have a transmission factor 42 times
greater than 0.0011. Therefore, these axes can operate with an additional transmission factor
caused by dirt, misalignment, etc., of up to 1/42 = 0.024. (Note that the worst-case numbers
for the beam splitters take into account the power division along each measurement axis.)