Laser Trackers: Testing and Standards
Content
Laser Trackers:
Testing and Standards
Dr. Steven D. Phillips
Dimensional Metrology Program Manager
National Institute of Standards and Technology
Large Scale Metrologists
Bala Muralikrishnan
Dan Sawyer
Chris Blackburn
Bruce Borchardt
Tyler Estler
Craig Shakarji
Overview
Briefly about Laser Trackers
B89.4.19 Standard & Tests Results
VDI/VDE 2617 Draft Standard
Final Remarks
Laser Trackers:
Coordinate Measuring Machines
Using Spherical Coordinates
R
Vertical Axis
Z
z
Y
φ
x
θ y
Horizontal Axis
X
Laser Trackers:
Optics Link the Workpiece & CMM
•Allows large measurement
volumes
•Bring the tracker to the
workpiece
•Lower capital costs than
large conventional CMMs
•Factory can be reconfigured
Laser Trackers:
Type of Ranging Systems
HeNe Interferometer
• Very High Accuracy
• Do NOT break beam during measurement
• Requires cooperative target, e.g. retroreflector
Absolute Distance Measuring System
• Good Accuracy
• Can break beam & measure directly to targets
• Requires cooperative target, e.g. retroreflector
Laser Radar
• Non cooperative target OK
• Moderate accuracy
• More expensive
ASME B89.4.19 Laser Tracker Standard
Designed to Test Cooperative Target Systems
Focused on Manufacturing (Indoor) Environment
Tests Ranging and Volumetric Performance
Does not address:
– Outdoor Environments
Rain; Fog
– NonCooperative Targets:
Concrete; Wood; Dirt
– Dynamic effects
Motion in the field of view
Available At
www.ASME.org
(search on B89.4.19)
Ranging Test using 6 Calibrated Lengths
Nest a
Target Nests
Nest b
h
L1
L2
L3
L4
1D Cooperative Target Range Facility
NIST System Configuration
Carriage can accommodate
a variety of targets
Interferometer
Instrument
under test
1-D Cooperative Target Range Facility
Target retroreflector
Reference retroreflector
1-D Cooperative Target Range Facility
Range: 60 m (200 feet)
Temperature: 20 ± 0.2 ° C
Sensors:
U(T) = 0.01 °C, spaced @ 10 m
U(P) = 20 Pa
U(RH) = 1 % RH
U(L) = 5 μm + 3 × 10-7
1-D Cooperative Target Range Facility
Ranging test of an IFM tracker showing vacuum wavelength error
0 .0 2
0 .0 1
Error (mm)
0
-0 . 0 1
-0 . 0 2
1 x 10-6
-0 . 0 3
-0 . 0 4
R un #1
C o r r e c te d r u n # 1
-0 . 0 5
R un #2
C o r r e c te d r u n # 2
-0 . 0 6
-0 . 0 7
E r r o r d u e to i n c o r r e c t w a v e l e n g th
0
10
20
30
40
50
D is p la c e m e n t ( m )
Wavelength in instrument = 632.990400 nm
Calibrated wavelength (NIST) = 632.991061 nm
Difference = 0.6 × 10-3 nm
Relative length error = 0.6 × 10-3 nm / 633 nm = 1 × 10-6
60
1-D Cooperative Target Range Facility
Ranging test of an IFM tracker; passing specifications
Error (mm)
0 .0 4
0 .0 3
Run #1
Run #2
0 .0 2
Run #3
M PE
+MPE
0 .0 1
0
-0 . 0 1
-0 . 0 2
−MPE
-0 . 0 3
-0 . 0 4
0
5
10
15
20
D is p la c e m e n t ( m )
25
30
35
1-D Cooperative Target Range Facility
Ranging test of an ADM tracker passing specifications
0 .0 8
Run #1
Run #2
Run #3
MPE
0 .0 6
Error (mm)
0 .0 4
+MPE
0 .0 2
0
Significantly more
points sampled than
required by B89.4.19
-0 . 0 2
-0 . 0 4
-0 . 0 6
-0 . 0 8
−MPE
0
10
20
30
40
D is p la c e m e n t ( m )
50
60
1-D Cooperative Target Range Facility
Ranging test of an ADM tracker showing complex
range errors before compensation & small errors
after compensation
Ranging System Test on ADM #2-2
0.400
Error, mm
0.300
Before Cal
0.200
After Cal
0.100
0.000
0
5
10
15
Length, m
20
25
Volumetric System Tests:
Check Optical-Mechanical Alignments
Volumetric System Tests
Vertical Positions
Horizontal Positions
Standing axis
Target stands
b
Standing axis
a
A
A
Target nests
a
b
h
h
D
D
Volumetric System Tests
Right Diagonal Position
Left Diagonal Position
45 degrees
0.7A
a
a
0.7A
0.7A
45 degrees
Standing axis
A
Target nests
Standing axis
A
0.7A
b
Target nests
h
D
h
D
b
Large Scale Volumetric Test Facility
B89.4.19 Volumetric System Tests
(Horizontal Tests)
Back to back target SMRs
Laser
Interferometer
B89.4.19 Volumetric System Tests
(Horizontal Tests – Physical Artifact)
B89.4.19 Volumetric System Tests
(Diagonal Tests)
B89.4.19 Volumetric System Tests
Volumetric test of an ADM, passing MPE specifications
Volumetric Performance Test on ADM #6
All readings in ADM mode unless otherw ise indicated
0.15
Horizontal
Vertical
Right Diagonal
Left Diagonal
User
0.10
0.05
90
18 0
270 0
9 0 18 0 2 7 0 0
90
18 0
270
0
9 0 18 0 2 7 0 0
90
18 0
270
0
9 0 18 0 2 7 0 0
90
18 0
270
0
9 0 18 0 2 7 0
1st reading
2nd reading
3rd reading
0.00
+MPE
-MPE
-0.05
1m
3m
-0.10
-0.15
3m
6m
3m
6m
3m
6m
6m
3m
5m
Error, mm
0
B89.4.19 Volumetric System Tests
Volumetric test of an IFM tracker, failing MPE specifications
Horizontal
3m
0.3
6m
Vertical
3m
6m
Right Diagonal Left Diagonal
3m
6m
3m
6m
0 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270
1st reading
2nd reading
3rd reading
MPE
E rro r (m m )
0.2
0.1
0
1m
-0.1
-0.2
-0.3
3m
3m
3m
6m
6m
3m
6m
6m
B89.4.19 Volumetric System Tests
Simulated and actual errors for the volumetric test
Beam Tilt (X)
Error
Beam Tilt (Y)
H or
3m
0
90
H or
6m
180
270 0
90
V er
3m
180
270
0
90
V er
6m
180
270 0
0.4
90
RD
3m
180
270
0
90
RD
6m
180
270 0
90
LD
3m
180
270 0
90
Horizontal Angle
Encoder
Eccentricity (X)
Horizontal Angle
Encoder
Eccentricity (Y)
LD
6m
180
270 0 90
180
270
M e a s u re d e rro rs
S im u la t e d e rro rs
Error (mm)
0.2
0
-0 . 2
-0 . 4
(
0
5H o r
H or
3m
0
90
10
V er
3m
6m
180
270 0
90
180
270
0
90
180
V er
6m
270 0
90
15
180
20
R D
3m
270
0
90
180
270 0
2 5L D
R D
6m
90
30
3m
180
270
0
90
35
L D
6m
180
270
0
90
180
270
B89.4.19 Two Face Test
B89.4.19 Two Face Tests
Error (mm)
Two face test of an ADM tracker, passing MPE specifications
1st reading
2nd reading
3rd reading
MPE
0.1
0.05
0
Low
0
90 180 270
Mid
0
90 180 270
High
0
D minimum
90 180 270
Low
0
90 180 270
Mid
0
90 180 270
3m
High
0
90 180 270
Low
0
90 180 270
Mid
0
90 180 270
6m
High
0
90 180 270
B89.4.19 Two Face Tests
Two face test of an ADM tracker, failing MPE specifications
0.5
1st reading
2nd reading
3rd reading
MPE
Error (mm)
0.4
0.3
0.2
0.1
0
Low
0
90 180 270
Mid
0
90 180 270
High
0
D minimum
90 180 270
Low
0
90 180 270
Mid
0
90 180 270
3m
High
0
90 180 270
Low
0
90 180 270
Mid
0
90 180 270
6m
High
0
90 180 270
B89.4.19 Two Face Tests
Simulated and actual errors for the two face test
Error
Horizontal angle
encoder
eccentricity (X)
Horizontal angle
encoder
eccentricity (Y)
Low
0
90 180 270
Mid
0
90 180 270
High
0
90 180 270
Low
0
90 180 270
D minimum
Mid
0
90 180 270
High
0
90 180 270
Low
0
3m
90 180 270
Mid
0
90 180 270
High
0
90 180 270
6m
Error (mm)
0.5
Measured errors
Simulated errors
0.4
0.3
0.2
0.1
0
0
5
10
15
20
25
30
35
(Kz)
VDI / VDE Tracker Draft
Use a measurement volume ≈ 3 x 6 x 10 m with
multiple calibrated lengths created via distances
between fixed mounts
Evaluate the
observed errors
against the
manufacture's
MPE specification
VDI / VDE Tracker Draft
Projecting the lengths onto a wall and moving the
tracker makes the set up easier
VDI / VDE Tracker Draft
“Probe Test” to check the SMR size and form
Similar to the ISO CMM probe test
25 measurement points on a
calibrated test sphere:
Report: Size and Form error
Final Thoughts On Laser Trackers
Large Measurement Volumes; range > 30 m
– Very Low Cost Compared to Large CMMs
Portable, Bring the Tracker to the Workpiece
– Allows Factory Floor to be Easily Reconfigured
ADM Systems Yield Direct Measurements
– No Issue with Beam Breakage or “Walkout”
Final Thoughts On Laser Trackers
Standardized Tracker Tests Allow
– For manufacturers to specify performance
– For users to test performance
– Detection of most tracker errors
– Test results that are metrologically traceable
(e.g., per ASME B89.7.5)
ISO Working Draft for Trackers
–
–
–
–
Combines B89 & VDI work
Improves sensitivity to errors
Includes SMR probe test
Includes workpiece CTE compensation test
Laser Trackers:
Testing and Standards
Q&A
Disclaimer:
Data on commercial products are only provided for the sake of describing
experimental results. NIST does not endorse or recommend any
commercial products or imply that this equipment is the best for any
particular application.
[email protected]
Testing and Standards
Dr. Steven D. Phillips
Dimensional Metrology Program Manager
National Institute of Standards and Technology
Large Scale Metrologists
Bala Muralikrishnan
Dan Sawyer
Chris Blackburn
Bruce Borchardt
Tyler Estler
Craig Shakarji
Overview
Briefly about Laser Trackers
B89.4.19 Standard & Tests Results
VDI/VDE 2617 Draft Standard
Final Remarks
Laser Trackers:
Coordinate Measuring Machines
Using Spherical Coordinates
R
Vertical Axis
Z
z
Y
φ
x
θ y
Horizontal Axis
X
Laser Trackers:
Optics Link the Workpiece & CMM
•Allows large measurement
volumes
•Bring the tracker to the
workpiece
•Lower capital costs than
large conventional CMMs
•Factory can be reconfigured
Laser Trackers:
Type of Ranging Systems
HeNe Interferometer
• Very High Accuracy
• Do NOT break beam during measurement
• Requires cooperative target, e.g. retroreflector
Absolute Distance Measuring System
• Good Accuracy
• Can break beam & measure directly to targets
• Requires cooperative target, e.g. retroreflector
Laser Radar
• Non cooperative target OK
• Moderate accuracy
• More expensive
ASME B89.4.19 Laser Tracker Standard
Designed to Test Cooperative Target Systems
Focused on Manufacturing (Indoor) Environment
Tests Ranging and Volumetric Performance
Does not address:
– Outdoor Environments
Rain; Fog
– NonCooperative Targets:
Concrete; Wood; Dirt
– Dynamic effects
Motion in the field of view
Available At
www.ASME.org
(search on B89.4.19)
Ranging Test using 6 Calibrated Lengths
Nest a
Target Nests
Nest b
h
L1
L2
L3
L4
1D Cooperative Target Range Facility
NIST System Configuration
Carriage can accommodate
a variety of targets
Interferometer
Instrument
under test
1-D Cooperative Target Range Facility
Target retroreflector
Reference retroreflector
1-D Cooperative Target Range Facility
Range: 60 m (200 feet)
Temperature: 20 ± 0.2 ° C
Sensors:
U(T) = 0.01 °C, spaced @ 10 m
U(P) = 20 Pa
U(RH) = 1 % RH
U(L) = 5 μm + 3 × 10-7
1-D Cooperative Target Range Facility
Ranging test of an IFM tracker showing vacuum wavelength error
0 .0 2
0 .0 1
Error (mm)
0
-0 . 0 1
-0 . 0 2
1 x 10-6
-0 . 0 3
-0 . 0 4
R un #1
C o r r e c te d r u n # 1
-0 . 0 5
R un #2
C o r r e c te d r u n # 2
-0 . 0 6
-0 . 0 7
E r r o r d u e to i n c o r r e c t w a v e l e n g th
0
10
20
30
40
50
D is p la c e m e n t ( m )
Wavelength in instrument = 632.990400 nm
Calibrated wavelength (NIST) = 632.991061 nm
Difference = 0.6 × 10-3 nm
Relative length error = 0.6 × 10-3 nm / 633 nm = 1 × 10-6
60
1-D Cooperative Target Range Facility
Ranging test of an IFM tracker; passing specifications
Error (mm)
0 .0 4
0 .0 3
Run #1
Run #2
0 .0 2
Run #3
M PE
+MPE
0 .0 1
0
-0 . 0 1
-0 . 0 2
−MPE
-0 . 0 3
-0 . 0 4
0
5
10
15
20
D is p la c e m e n t ( m )
25
30
35
1-D Cooperative Target Range Facility
Ranging test of an ADM tracker passing specifications
0 .0 8
Run #1
Run #2
Run #3
MPE
0 .0 6
Error (mm)
0 .0 4
+MPE
0 .0 2
0
Significantly more
points sampled than
required by B89.4.19
-0 . 0 2
-0 . 0 4
-0 . 0 6
-0 . 0 8
−MPE
0
10
20
30
40
D is p la c e m e n t ( m )
50
60
1-D Cooperative Target Range Facility
Ranging test of an ADM tracker showing complex
range errors before compensation & small errors
after compensation
Ranging System Test on ADM #2-2
0.400
Error, mm
0.300
Before Cal
0.200
After Cal
0.100
0.000
0
5
10
15
Length, m
20
25
Volumetric System Tests:
Check Optical-Mechanical Alignments
Volumetric System Tests
Vertical Positions
Horizontal Positions
Standing axis
Target stands
b
Standing axis
a
A
A
Target nests
a
b
h
h
D
D
Volumetric System Tests
Right Diagonal Position
Left Diagonal Position
45 degrees
0.7A
a
a
0.7A
0.7A
45 degrees
Standing axis
A
Target nests
Standing axis
A
0.7A
b
Target nests
h
D
h
D
b
Large Scale Volumetric Test Facility
B89.4.19 Volumetric System Tests
(Horizontal Tests)
Back to back target SMRs
Laser
Interferometer
B89.4.19 Volumetric System Tests
(Horizontal Tests – Physical Artifact)
B89.4.19 Volumetric System Tests
(Diagonal Tests)
B89.4.19 Volumetric System Tests
Volumetric test of an ADM, passing MPE specifications
Volumetric Performance Test on ADM #6
All readings in ADM mode unless otherw ise indicated
0.15
Horizontal
Vertical
Right Diagonal
Left Diagonal
User
0.10
0.05
90
18 0
270 0
9 0 18 0 2 7 0 0
90
18 0
270
0
9 0 18 0 2 7 0 0
90
18 0
270
0
9 0 18 0 2 7 0 0
90
18 0
270
0
9 0 18 0 2 7 0
1st reading
2nd reading
3rd reading
0.00
+MPE
-MPE
-0.05
1m
3m
-0.10
-0.15
3m
6m
3m
6m
3m
6m
6m
3m
5m
Error, mm
0
B89.4.19 Volumetric System Tests
Volumetric test of an IFM tracker, failing MPE specifications
Horizontal
3m
0.3
6m
Vertical
3m
6m
Right Diagonal Left Diagonal
3m
6m
3m
6m
0 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270 0 90 180 270
1st reading
2nd reading
3rd reading
MPE
E rro r (m m )
0.2
0.1
0
1m
-0.1
-0.2
-0.3
3m
3m
3m
6m
6m
3m
6m
6m
B89.4.19 Volumetric System Tests
Simulated and actual errors for the volumetric test
Beam Tilt (X)
Error
Beam Tilt (Y)
H or
3m
0
90
H or
6m
180
270 0
90
V er
3m
180
270
0
90
V er
6m
180
270 0
0.4
90
RD
3m
180
270
0
90
RD
6m
180
270 0
90
LD
3m
180
270 0
90
Horizontal Angle
Encoder
Eccentricity (X)
Horizontal Angle
Encoder
Eccentricity (Y)
LD
6m
180
270 0 90
180
270
M e a s u re d e rro rs
S im u la t e d e rro rs
Error (mm)
0.2
0
-0 . 2
-0 . 4
(
0
5H o r
H or
3m
0
90
10
V er
3m
6m
180
270 0
90
180
270
0
90
180
V er
6m
270 0
90
15
180
20
R D
3m
270
0
90
180
270 0
2 5L D
R D
6m
90
30
3m
180
270
0
90
35
L D
6m
180
270
0
90
180
270
B89.4.19 Two Face Test
B89.4.19 Two Face Tests
Error (mm)
Two face test of an ADM tracker, passing MPE specifications
1st reading
2nd reading
3rd reading
MPE
0.1
0.05
0
Low
0
90 180 270
Mid
0
90 180 270
High
0
D minimum
90 180 270
Low
0
90 180 270
Mid
0
90 180 270
3m
High
0
90 180 270
Low
0
90 180 270
Mid
0
90 180 270
6m
High
0
90 180 270
B89.4.19 Two Face Tests
Two face test of an ADM tracker, failing MPE specifications
0.5
1st reading
2nd reading
3rd reading
MPE
Error (mm)
0.4
0.3
0.2
0.1
0
Low
0
90 180 270
Mid
0
90 180 270
High
0
D minimum
90 180 270
Low
0
90 180 270
Mid
0
90 180 270
3m
High
0
90 180 270
Low
0
90 180 270
Mid
0
90 180 270
6m
High
0
90 180 270
B89.4.19 Two Face Tests
Simulated and actual errors for the two face test
Error
Horizontal angle
encoder
eccentricity (X)
Horizontal angle
encoder
eccentricity (Y)
Low
0
90 180 270
Mid
0
90 180 270
High
0
90 180 270
Low
0
90 180 270
D minimum
Mid
0
90 180 270
High
0
90 180 270
Low
0
3m
90 180 270
Mid
0
90 180 270
High
0
90 180 270
6m
Error (mm)
0.5
Measured errors
Simulated errors
0.4
0.3
0.2
0.1
0
0
5
10
15
20
25
30
35
(Kz)
VDI / VDE Tracker Draft
Use a measurement volume ≈ 3 x 6 x 10 m with
multiple calibrated lengths created via distances
between fixed mounts
Evaluate the
observed errors
against the
manufacture's
MPE specification
VDI / VDE Tracker Draft
Projecting the lengths onto a wall and moving the
tracker makes the set up easier
VDI / VDE Tracker Draft
“Probe Test” to check the SMR size and form
Similar to the ISO CMM probe test
25 measurement points on a
calibrated test sphere:
Report: Size and Form error
Final Thoughts On Laser Trackers
Large Measurement Volumes; range > 30 m
– Very Low Cost Compared to Large CMMs
Portable, Bring the Tracker to the Workpiece
– Allows Factory Floor to be Easily Reconfigured
ADM Systems Yield Direct Measurements
– No Issue with Beam Breakage or “Walkout”
Final Thoughts On Laser Trackers
Standardized Tracker Tests Allow
– For manufacturers to specify performance
– For users to test performance
– Detection of most tracker errors
– Test results that are metrologically traceable
(e.g., per ASME B89.7.5)
ISO Working Draft for Trackers
–
–
–
–
Combines B89 & VDI work
Improves sensitivity to errors
Includes SMR probe test
Includes workpiece CTE compensation test
Laser Trackers:
Testing and Standards
Q&A
Disclaimer:
Data on commercial products are only provided for the sake of describing
experimental results. NIST does not endorse or recommend any
commercial products or imply that this equipment is the best for any
particular application.
[email protected]
