tchapters polaris™ kinematic mirror mounts (page 1 of 3)for comparison: to get a 1 µrad change in...

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CHAPTERS

Tables/ Breadboards

Mechanics

Optomechanic Devices

Kits

Lab Supplies

SECTIONS

Mini Series

Ø1/2" Post Assemblies

Ø1" Post Assemblies

Ø1.5" Post Assemblies

Mounting/Angle Brackets

Lab Platforms

Instrument Shelves

Lens Tubes

Cage Systems

Optical Rails

Mirror Mounts

Kinematic Mounts

Fixed Mounts

Translation Mounts

Rotation Mounts

Filter Mounts

V-Mounts

Irises/Apertures

Adapters

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Optomechanics

Polaris™ Kinematic Mirror Mounts ( of 3)

The Polaris Kinematic Mirror Mounts for Ø1/2" (Ø12.7 mm) or Ø1" (Ø25.4 mm) optics provide superior long-term alignment

stability. Extensive research, engineering, computer simulation, and testing

was done during the design process to determine the materials, components, and design elements that would result in the best performance characteristics. The Polaris design addresses all of the common causes of beam misalignment. These include temperature-induced hysteresis of the mirror position, crosstalk, drift, and backlash.

Thermal HysteresisThe temperature in most labs is not constant because of contributing effects like air conditioning system settings, the number of people in the room, and whether equipment is on or off. As a result, it is necessary that all mounts used in an alignment-sensitive optical setup be designed to minimize any thermally induced alignment effects. Thermal effects can be minimized by choosing materials with a low coefficient of thermal expansion (CTE) such as stainless steel. However, even mounts made from a material with a low CTE do not typically return the mirror to its initial position when the initial temperature is restored. All the critical components of the Polaris mirror mounts are heat treated prior to assembly since this process removes internal stresses that can cause temperature-dependent hysteresis in the mirror’s position. As a result, the alignment of the optical system will be restored when the temperature of the mirror mount is returned to the temperature at which the alignment was made.

Another important design feature was to consider how the mirror was held. Other premium ultra-stable mirror mounts require the user to glue the mirror into the mount to achieve the best performance. In contrast, the Polaris uses a flat spring that is pressed into the edge of the mirror using a setscrew. This mechanism, unlike the direct use of a setscrew, provides a more stable means of keeping the mirror locked into place independent of the mount’s temperature.

CrosstalkCrosstalk was minimized by using extremely high dimensional tolerances for both the front and back plates so that the pitch and yaw actuators are orthogonal. In addition, sapphire seats were used at all three contact points. The hardness of sapphire ensures that, with use, the tight tolerances of the initial design will be maintained.

Drift and BacklashIn order to minimize the positional drift of the mirror mount and backlash, it is necessary to limit the amount of play in the adjuster as well as the amount of lubricant used. When an adjustment is made to the actuator, the lubricant will be displaced. This non-equilibrium distribution of lubricant will relax back into an equilibrium state. However, in doing so, this causes the position of the front plate of the mirror mount to drift for an extended period of time. The Polaris mounts use matched adjusters with precision threads that exceed the best industry standards so that very little adjuster lubricant is needed. As a result, the alignment of these mirror mounts is extremely stable, even after being adjusted. In addition, these adjusters have an extremely smooth feel that allows the user to make repeatable small adjustments.

FLEXTURE SPRINGOPTIC RETAINING

MECHANISM

ACCEPTS Ø0.50" (12.7 mm) OPTICS0.23" (5.8 mm) DEEPØ0.45" (Ø11.4 mm) CLEAR APERTURE

0.97"(24.5 mm)

0.47"(11.9 mm)

0.47"(11.9 mm)

0.97"(24.5 mm)

0.77"(19.5 mm)

0.52"(13.2 mm)

0.25"(6.4 mm)

0.50"(12.7 mm)

1.00"(25.4 mm)

0.50"(12.7 mm)

1.00"(25.4 mm)

0.40"(10.2 mm) #8 (M4) CLEARANCE HOLE

2 PLACES @ 90º

3/16"-130 ADJUSTER SCREW5/64" (2.0 mm HEX3 PLACES

0.72"(18.3 mm)NORMAL

Please refer to our website for complete models and drawings.

POLARIS-K05Post and Mirror Not Included

POLARIS-K1-HMirror Not Included

Please Visit www.thorlabs.com

for the POLARIS-K1

Mount Usage Tips

12-12-13Updated Drawing

- LF

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CHAPTERS

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Lab Platforms

Instrument Shelves

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Mirror Mounts

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Translation Mounts

Rotation Mounts

Filter Mounts

V-Mounts

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Optomechanics

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For Comparison: To get a 1 µrad change in the mount’s position, the 100 TPI adjuster on a Ø1" Polaris mirror mount needs to be rotated by only 0.05° (1/7200 of a turn). A highly skilled operator might be able to make an adjustment as small as 0.3° (1/1200 of a turn), which corresponds to 6 µrad.

Test Conditions: Each kinematic mirror mount was attached to a Ø1" stainless steel post secured to a stainless steel optical breadboard in a temperature-controlled environment. The mirror was mounted (not glued) in the mirror mount. The beam from an independently temperature-stabilized diode laser was reflected off the mirror’s surface onto a position sensing detector.

Purpose: To determine the effects that cyclic temperature changes have on the position of the mirror. Specifically, does the mount reliably return the mirror to its initial position, so that the alignment of the optical system is unaffected by the cycling of the temperature.

Procedure: The temperature of each Ø1/2" mirror mount tested was raised by 13.5 °C. The elevated temperature was maintained for 60 minutes (soak time). Then the temperature of the mirror mount was returned to the starting temperature. A similar procedure was applied to the Ø1" mirror mounts with a temperature change of 12.5 °C and a 120 minutes soak time.

Results: As can be seen in the plots below, when the Polaris mounts were returned to their initial temperature, the angular position (both pitch and yaw) of the mirror mounted returned to within 2 µrad of its initial position. The best result achieved with a competitor’s mount was significantly worse. The performance of the mount was tested further by subjecting it to repeated temperature change cycles.

After each cycle, the mirror’s position reliably returned to within 2 µrad of its initial position.


Temperature Cycling Test

1.00"(25.4 mm)

Ø0.93" (Ø23.9 mm)

Clear ApertureAccepts Ø1.00"

(Ø25.0 mm) Optics

2.00"(50.8 mm)

100 TPI Adjuster (3 Places)

#8 (M4)Counterbored Through Hole(2 Places)

1.58"(40.2 mm)2.00"

(50.8 mm)

1.00"(25.4 mm)

Flexure Spring Optic Retaining

Mechanism

POLARIS-K1POLARIS-K1Mirror Not Included

0 50 100 150 200 250 300-5 -5

Time (min)

0

10

20

30

40

0

10

20

30

40

Change in Temperature (°C)

Yaw (µrad)Pitch (µrad)Temperature (°C)

Angu

lar D

efle

ctio

n (µ

rad)

Best Competitor Results

Angular Deflection Caused by Cycling the Temperature for ø1/2" Mount

Time (min)

Angu

lar D

efle

ctio

n (µ

rad)


13.5

6.75

0

6.75

13.5

Yaw (µrad)

Pitch (µrad)

Temperature (°C)

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

60 70 80 90 100 110 120 130 140

5

4

3

2

1

0

-1

-2

-3

-4

-5

Time (min)

Angu

lar D

efle

ctio

n (µ

rad)


5

4

3

2

1

0

-1

-2

-3

-4

-5


20

10

0

-10

-20

-30

Angu

lar D

efle

ctio

n (µ

rad)

125 150 200 250 300

-4

-3

-2

-1

0

1

2

3

4

5

-5

-4

-3

-2

-1

0

1

2

3

4

5

Time (min)

-5

0 50 100 150 200 250 300-5

0

10

20

30

40

10

20

30

40 Change in Temperature (°C)


Angular Deflection Caused by Cycling the Temperature for ø1" Mount

Angu

lar D

efle

ctio

n (µ

rad) Yaw (µrad)

Pitch (µrad)Temperature (°C)


0

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CHAPTERS

Tables/ Breadboards

Mechanics


Kits

Lab Supplies

SECTIONS

Mini Series





Lab Platforms

Instrument Shelves

Lens Tubes

Cage Systems

Optical Rails

Mirror Mounts

Kinematic Mounts

Fixed Mounts

Translation Mounts

Rotation Mounts

Filter Mounts

V-Mounts

Irises/Apertures

Adapters

tt

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Optomechanics

ITEM # $ £ € RMB DESCRIPTION POLARIS-K05 $ 129.00 £ 92.88 € 112,23 ¥ 1,028.13 Polaris™ Ø1/2" Ultra-Stable Kinematic Mirror Mount

POLARIS-K1 $ 129.00 £ 92.88 € 112,23 ¥ 1,028.13 Polaris™ Ø1" Ultra-Stable Kinematic Mirror Mount

POLARIS-K1-H $ 126.00 £ 90.72 € 109,62 ¥ 1,004.22 Hex-Driven Polaris™ Ø1" Ultra-Stable Kinematic Mirror Mount

Drift Due to an Angular Adjustment Purpose: To determine the long-term drift effects of making an angular adjustment. See the Drift and Backlash discussion on page XXX for why this drift occurs.

Procedure: The pitch adjuster on the POLARIS-K1 was rotated 125° and then rotated back to its starting point.

Plot Interpretation: In order to show the long-term effects, the vertical axis scale is zoomed in. The initial displacement at t=0 was greater than 2500 µrad with a correction back in the other direction at the end to get close to zero on the position sensing detector. Due to the length of the time scale, the initial displacement to start the test shows up as a vertical red line at the start of the plot.

Results: As can be seen from the zoomed region in the plot to the right, the deviation in the beam propagation direction was less than 5 µrad of pitch rotation and less than 2 µrad of yaw rotation.

ConclusionsThe Polaris is a high-quality ultra-stable mount that will reliably return the mirror to its original position after cycling through a temperature change. In addition, the high-precision matched adjusters show very little drift even after making a large adjustment. As a result, the Polaris is ideal for use in applications that require long-term alignment stability.

Angular Drift After a Large Pitch Adjustment

Time (min)An

gula

r Cha

nge

(ura

d)0 5 10 15 20 25 30 35 40 45 50 55

543210

-1-2-3-4-5

Change in YawChange in Pitch

Angular Adjustment Test

1.00"(25.4 mm)

Ø0.93" (Ø23.9 mm)

Clear ApertureAccepts Ø1.00"

(Ø25.0 mm) Optics

2.00"(50.8 mm)

2.00"(50.8 mm)

1.00"(25.4 mm)

Flexure Spring Optic Retaining

Mechanism

0.30"(7.6 mm)

1.08"(27.5 mm)

0.60"(15.2 mm)

1/4"-100 Adjuster Screw5/64" (2.0 mm) Hex (3 Places)

#8 (M4) CenterboredThrough Hole(2 Places)

1.03"(26.0 mm)Nominal

POLARIS-K1-H

Please refer to our website for complete models and drawings.


SPECIFICATIONS POLARIS-K05 POLARIS-K1 & POLARIS-K1-H

Optic Size Ø1/2" or Ø12.5 mm Ø1" or Ø25 mm

Optic Thickness (Min) 0.08" (2 mm)

Adjusters 130 TPI 100 TPI

Resolution* ~7.5 mrad/rev ~7 mrad/rev

Front Plate Translation (Max) 5 mm 6 mm

Angular Range ±5° ±4°

Front Plate Separation at Pivot Adjuster 1.5 ± 1 mm 3 ± 1 mm

Beam Deviation** <2 µrad

Mounting #8 (M4) Counterbore

Operating Temperature Range -30 to 200 °C

*When the front plate is parallel to the back plate** After 12.5° temperature cycle, the beam returns to within 2 µrad of its original position. Note: this value does not take into

account effects caused by the method at which the Polaris is mounted.

POLARIS-K1-HShortened Hex Drive Ideal for Applications with Space Constraints

POLARIS-K05

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tchapters polaris™ kinematic mirror mounts (page 1 of 3)for comparison: to get a 1 µrad change in...

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