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XL laser system
XL-80 hardware XL-80 applications
Appendix C
Quadrature output
Quadrature output is available as a factory set option on the XL laser.
The quadrature output allows ‘raw’ interferometry signals to be supplied to custom-
designed circuitry, to allow for example, the laser to be used as a linear encoder
system. The quadrature signals are accessed via a connector on the XL laser
rear panel (see Auxiliary I/O connector pinout). Resolution is dependent on the
configuration of the DIP switches (Switch 2 off = 80 nm, on = 10 nm).
Do not use the quadrature output facility of the XL laser to provide
closed loop feedback control for a machine. The system is not
designed to be used for feedback control and injury could result if
used for this purpose.
XL-80Q may have export control restrictions in your region.
Please contact your local Renishaw subsidiary for further information.
Format
These signals are not compensated for changes in the refractive index of air.
The A, /A, B, /B, ALARMOUT and /ALARMOUT signals are provided in RS422
balanced differential line format.
Resolution
The ‘A’ QUAD ‘B’ signals are represented in diagram below.
AQuad
Pitch
Resolution
BQuad
λ/2 or λ/16
λ/8 or λ/64
Resolution of quadrature signals
The maximum quadrature resolution can be selected as λ/8 (approximately 80
nm) or λ/64 (approximately 10 nm) giving a pitch of λ/2 or λ/16 respectively.
Direction sign convention
Linear measurement optical setup
1
XL laser
2
Reference reflector
3
Linear interferometer
4
Measurement reflector
With the optics configured as shown above, the sign convention is as follows:
- For positive movement (measurement retro-reflector moving away from XL
laser) A leads B.
- For negative movement (measurement retro-reflector moving toward XL laser)
B leads A.
Update rate
The quadrature output update rate is 20 MHz.
4
3
2
1
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