Dr. Steven D. PhillipsDr. Steven D. PhillipsDimensional Metrology Program ManagerDimensional Metrology Program Manager

National Institute of Standards and TechnologyNational Institute of Standards and Technology

Laser Trackers: Laser Trackers: Testing and StandardsTesting and Standards

Large Scale MetrologistsLarge Scale MetrologistsBalaBala MuralikrishnanMuralikrishnan

Dan SawyerDan SawyerChris BlackburnChris BlackburnBruce BorchardtBruce Borchardt

Tyler Tyler EstlerEstlerCraig Craig ShakarjiShakarji

OverviewOverview

Briefly about Laser TrackersBriefly about Laser TrackersB89.4.19 Standard & Tests ResultsB89.4.19 Standard & Tests ResultsVDI/VDE 2617 Draft Standard VDI/VDE 2617 Draft Standard Final RemarksFinal Remarks

X

Y

Z

x

y

z

Horizontal Axis

R

φ

θ

Ver

tical

Axi

s

Laser Trackers:Laser Trackers:Coordinate Measuring Machines Coordinate Measuring Machines Using Spherical CoordinatesUsing Spherical Coordinates

Laser Trackers:Laser Trackers:Optics Link the Workpiece & CMM 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:Laser Trackers:Type of Ranging Systems Type of Ranging Systems

Laser Radar• Non cooperative target OK

• Moderate accuracy

• More expensive

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

ASME B89.4.19 Laser Tracker StandardASME B89.4.19 Laser Tracker Standard

Designed to Test Cooperative Target SystemsDesigned to Test Cooperative Target SystemsFocused on Manufacturing (Indoor) EnvironmentFocused on Manufacturing (Indoor) EnvironmentTests Ranging and Volumetric PerformanceTests Ranging and Volumetric PerformanceDoes not address:Does not address:–– Outdoor EnvironmentsOutdoor Environments

Rain; Fog Rain; Fog

–– NonCooperativeNonCooperative Targets: Targets: Concrete; Wood; DirtConcrete; Wood; Dirt

–– Dynamic effectsDynamic effectsMotion in the field of viewMotion in the field of view

Available At www.ASME.org

(search on B89.4.19)

Ranging Test using 6 Calibrated LengthsRanging Test using 6 Calibrated Lengths

L1 L2

L3 L4

Target Nests

Nest b

Nest a

h

1D Cooperative Target Range Facility1D Cooperative Target Range FacilityNIST System ConfigurationNIST System Configuration

Interferometer

Instrument under test

Carriage can accommodate a variety of targets

11--D Cooperative Target Range FacilityD Cooperative Target Range Facility

Reference retroreflector

Target retroreflector

11--D Cooperative Target Range FacilityD 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

11--D Cooperative Target Range FacilityD Cooperative Target Range FacilityRanging test of an IFM tracker showing vacuum wavelength errorRanging test of an IFM tracker showing vacuum wavelength error

0 1 0 2 0 3 0 4 0 5 0 6 0- 0 . 0 7

- 0 . 0 6

- 0 . 0 5

- 0 . 0 4

- 0 . 0 3

- 0 . 0 2

- 0 . 0 1

0

0 . 0 1

0 . 0 2

D is p la c e m e n t ( m )

Erro

r (m

m)

R u n # 1C o r r e c te d r u n # 1R u n # 2C o r r e c te d r u n # 2E 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

1 x 10-6

Wavelength in instrument = 632.990400 nmCalibrated wavelength (NIST) = 632.991061 nm Difference = 0.6 × 10-3 nmRelative length error = 0.6 × 10-3 nm / 633 nm = 1 × 10-6

11--D Cooperative Target Range FacilityD Cooperative Target Range Facility

0 5 1 0 1 5 2 0 2 5 3 0 3 5-0 . 0 4

-0 . 0 3

-0 . 0 2

-0 . 0 1

0

0 . 0 1

0 . 0 2

0 . 0 3

0 . 0 4

D is p la c e m e n t (m )

Erro

r (m

m)

R u n # 1R u n # 2R u n # 3M P E

Ranging test of an IFM tracker; passing specificationsRanging test of an IFM tracker; passing specifications

+MPE

−MPE

11--D Cooperative Target Range FacilityD Cooperative Target Range FacilityRanging test of an ADM tracker passing specificationsRanging test of an ADM tracker passing specifications

0 1 0 2 0 3 0 4 0 5 0 6 0-0 . 0 8

-0 . 0 6

-0 . 0 4

-0 . 0 2

0

0 . 0 2

0 . 0 4

0 . 0 6

0 . 0 8

D is p la c e m e n t (m )

Erro

r (m

m)

R u n # 1R u n # 2R u n # 3M P E

+MPE

−MPE

Significantly morepoints sampled than required by B89.4.19

Ranging System Test on ADM #2-2

0.000

0.100

0.200

0.300

0.400

0 5 10 15 20 25

Length, m

Erro

r, m

m

11--D Cooperative Target Range FacilityD Cooperative Target Range FacilityRanging test of an ADM tracker showing complex Ranging test of an ADM tracker showing complex range errors before compensation & small errors range errors before compensation & small errors after compensationafter compensation

Before Cal

After Cal

Volumetric System Tests:Volumetric System Tests:Check OpticalCheck Optical--Mechanical AlignmentsMechanical Alignments

Volumetric System TestsVolumetric System Tests

b

a

A

D h

Target stands

Standing axis

a

bh

D

Target nestsA

Standing axis

Horizontal Positions Vertical Positions

Volumetric System TestsVolumetric System Tests

Right Diagonal Position Left Diagonal Position

45 degrees0.7A

h

a

b Target nests

D

0.7A

Standing axis A

45 degrees

h

0.7A

D

a

b

Target nests

0.7A

Standing axis

A

Large Scale Volumetric Test FacilityLarge Scale Volumetric Test Facility

B89.4.19 Volumetric System TestsB89.4.19 Volumetric System Tests(Horizontal Tests)(Horizontal Tests)

Back to back target SMRs

LaserInterferometer

B89.4.19 Volumetric System TestsB89.4.19 Volumetric System Tests(Horizontal Tests (Horizontal Tests –– Physical Artifact)Physical Artifact)

B89.4.19 Volumetric System TestsB89.4.19 Volumetric System Tests(Diagonal Tests)(Diagonal Tests)

Volumetric Performance Test on ADM #6

-0.15

-0.10

-0.05

0.00

0.05

0.10

0.15

Erro

r, m

m

1st reading

2nd reading

3rd reading

+MPE

-MPE

Vertical Right DiagonalHorizontal Left Diagonal User

All readings in ADM mode unless otherw ise indicated

3m

6m

3m

6m

3m

6m

3m

6m

1m

3m5m

0 9 0 18 0 2 7 0 0 9 0 18 0 2 7 0 0 9 0 18 0 2 7 0 0 9 0 18 0 2 7 0 0 9 0 18 0 2 7 0 0 9 0 18 0 2 7 0 0 9 0 18 0 2 7 0 0 9 0 18 0 2 7 0

B89.4.19 Volumetric System TestsB89.4.19 Volumetric System TestsVolumetric test of an ADM, passing MPE specificationsVolumetric test of an ADM, passing MPE specifications

B89.4.19 Volumetric System TestsB89.4.19 Volumetric System Tests

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

Erro

r (m

m)

1st reading2nd reading3rd readingMPE

3m 6m 3m 6m 3m 6m 3m 6m0 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

3 m 6 m

3 m6 m

3 m6 m

3 m6 m

1 m

Horizontal Vertical Right Diagonal Left Diagonal

Volumetric test of an IFM tracker, failing MPE specificationsVolumetric test of an IFM tracker, failing MPE specifications

B89.4.19 Volumetric System TestsB89.4.19 Volumetric System Tests

H o r 3 m

H o r 6 m

V e r 3 m

V e r 6 m

R D 3 m

R D 6 m

L D 3 m

L D 6 m

0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0

Erro

r

Beam Tilt (X)

Beam Tilt (Y)

Horizontal Angle Encoder Eccentricity (Y)

Horizontal Angle Encoder Eccentricity (X)

0 5 1 0 1 5 2 0 2 5 3 0 3 5-0 .4

-0 .2

0

0 .2

0 .4

Erro

r (m

m)

M e a s u re d e rro rsS im u la te d e rro rs

H o r 3 m

H o r 6 m

V e r 3 m

V e r 6 m

R D 3 m

R D 6 m

L D 3 m

L D 6 m

0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0

(0 5 1 0 1 5 2 0 2 5 3 0 3 5

-0 .4

-0 .2

0

0 .2

0 .4

Erro

r (m

m)

M e a s u re d e rro rsS im u la te d e rro rs

0 5 1 0 1 5 2 0 2 5 3 0 3 5-0 .4

-0 .2

0

0 .2

0 .4

Erro

r (m

m)

M e a s u re d e rro rsS im u la te d e rro rs

H o r 3 m

H o r 6 m

V e r 3 m

V e r 6 m

R D 3 m

R D 6 m

L D 3 m

L D 6 m

0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0 0 9 0 1 8 0 2 7 0

(

Simulated and actual errors for the volumetric testSimulated and actual errors for the volumetric test

B89.4.19 Two Face TestB89.4.19 Two Face Test

B89.4.19 Two Face TestsB89.4.19 Two Face Tests

0

0.05

0.1

Erro

r (m

m)

1st reading2nd reading3rd readingMPE

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 0 90 180 270

D minimum 3 m 6 m

Low Mid High Low Mid High Low Mid High

Two face test of an ADM tracker, passing MPE specificationsTwo face test of an ADM tracker, passing MPE specifications

B89.4.19 B89.4.19 Two Face Two Face TestsTests

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 0 90 180 270

D minimum 3 m 6 m

Low Mid High Low Mid High Low Mid High

0

0.1

0.2

0.3

0.4

0.5

Erro

r (m

m)

1st reading2nd reading3rd readingMPE

Two face test of an ADM tracker, failing MPE specificationsTwo face test of an ADM tracker, failing MPE specifications

B89.4.19 B89.4.19 Two Face Two Face TestsTests

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 0 90 180 270

D minimum 3 m 6 m

Low Mid High Low Mid High Low Mid High (Kz)

Erro

r

Horizontal angle encoder eccentricity (X) Horizontal angle encoder eccentricity (Y)

0 5 10 15 20 25 30 350

0.1

0.2

0.3

0.4

0.5

Erro

r (m

m) Measured errors

Simulated errors

Simulated and actual errors for the two face testSimulated and actual errors for the two face test

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 TrackersFinal Thoughts On Laser TrackersLarge Measurement Volumes; range Large Measurement Volumes; range > 30 m> 30 m–– Very Low Cost Compared to Large CMMsVery Low Cost Compared to Large CMMs

Portable, Bring the Tracker to the WorkpiecePortable, Bring the Tracker to the Workpiece–– Allows Factory Floor to be Easily ReconfiguredAllows Factory Floor to be Easily Reconfigured

ADM Systems Yield Direct MeasurementsADM Systems Yield Direct Measurements–– No Issue with Beam Breakage or No Issue with Beam Breakage or ““WalkoutWalkout””

Standardized Tracker Tests AllowTracker 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)

Final Thoughts On Laser Trackers

ISO Working Draft for Trackers– Combines B89 & VDI work– Improves sensitivity to errors– Includes SMR probe test– Includes workpiece CTE compensation test

Laser Trackers: Laser Trackers: Testing and StandardsTesting and Standards

Q & AQ & A

Steven.Phillips@NIST.gov

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.