Polaris® Low-Distortion Kinematic Mirror Mounts

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POLARIS-K1F Ø1" Mount Cutaway Diagram
(Ø2" Polaris Mounts Incorporate a
Similar Optic Retention Design)

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Spring with Indexing Tab


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POLARIS-K05F6 Ø1/2" Mount Cutaway Diagram

Features

• Machined from Stress-Relieved Stainless Steel with Matched Coefficients of Thermal Expansion (CTE)
• Spring-Loaded, Indexed, Three-Point-Contact Plate Secures Optic
• Hardened Stainless Steel Ball Contacts with Sapphire Seats for Durability and Smooth Movement
• Matched Actuator/Body Pairs Provide Smooth Kinematic Adjustment
• Extensive Testing Guarantees Less than 2 µrad Deviation after Temperature Cycling (See Thermal Test Data tab for Details)
• Passivated Stainless Steel Surface Ideal for Vacuum and High-Power Laser Cavity Applications
• Custom Mount Configurations are Available by Contacting Tech Support

The Polaris^® Low-Distortion Kinematic Mirror Mounts (US Patent 9,599,786) provide long-term pointing stability while minimizing optic surface distortion introduced by the mount.

Optic Retention
Each mount features a three-point-contact faceplate to mount the optic to reduce optical distortion compared to standard setscrew or retaining ring optic mount designs. An indexed retention spring between the optic and retaining ring eliminates bending moments on the optic and ensures the force on the optic remains constant over large temperature changes. See the Low Distortion tab and the Optic Installation tab for more details.

Polaris optic bores are precision machined to achieve a fit that will provide optimum beam pointing stability performance over changing environmental conditions such as temperature changes, transportation shock, and vibration. Each mount is designed to be used with an optic that is within +0.0 mm / -0.15 mm of the specified diameter; using an optic outside of this range will lead to diminished performance. For inquiries about mounts for other optic sizes, please contact Tech Support.

Design
Machined from heat-treated stainless steel, Polaris mounts utilize precision-matched adjusters with ball contacts and sapphire seats to provide smooth kinematic adjustment. As shown on the Thermal Test Data tab, these mounts have undergone extensive testing to ensure high-quality performance. The Polaris design addresses all of the common causes of beam misalignment; please refer to the Design Features tab for detailed information.

Post Mounting
The Polaris mirror mounts are equipped with #8 (M4) counterbores for post mounting. Select mounts also include Ø2 mm alignment pin holes around the mounting counterbore, allowing for precision alignments when paired with our posts for Polaris mirror mounts. See the Usage Tips tab for more recommendations about mounting configurations.

Cleanroom and Vacuum Compatibility
All Polaris mounts, retaining rings, and lock nuts sold on this page are designed to be compatible with cleanroom and vacuum applications. See the Specs tab and the Design Features tab for more information.

• Given is the item number suffix. All item numbers in the Polaris line start with POLARIS.
• For best performance, use optics with a diameter tolerance of up to +0/-0.15 mm.
• When mounted using the included optic retention spring and the included retaining ring.
• When the POLARIS^® lock nuts are used
• When the front plate is parallel to the back plate.
• After 12.5 °C temperature cycle, the beam returns to within 2 μrad of its original position for a Polaris mounted on a Ø1" post with a 2" beam height. Please see the Test Data tab for more details.
• For details on optic installation, please refer to the Optic Installation tab.
• The Ø1/2" Mounts come with 8-32 and M4 low-profile cap screws for mounting without obstructing the transmissive beam path. The Ø25 mm, Ø1", Ø50 mm, and Ø2" Mounts come with standard 8-32 and M4 cap screws.
• Standard DIN 7-m6 ground dowel pins are recommended. The recommended tolerance for the location of the mating dowel pin holes and threaded mounting hole is ±0.003".
• These mounts are vacuum compatible, assembled in a clean environment, chemically cleaned using the Carpenter AAA passivation method to remove sulfur, iron, and contaminants from the surface, and double vacuum bagged. The 8-32 and M4 cap screws included with the Polaris mounts are not rated for pressures below 10^-5 Torr. Prior to placing any components in a sensitive vacuum system, a thorough pre-baking in a bake-out oven should be performed to remove all moisture and surface volatiles. Contact techsupport@thorlabs.com for details.

Installing an Optic into a Polaris Low-Distortion Mount

Ensure that there is no grease, dirt, or dust in the optic bore or on the optic itself. Remove any particulates with clean compressed air and/or clean with methanol, acetone, or ethanol. The optic, indexed retention spring, and retaining ring are installed from the back of the mount, as shown in the animation to the right. Be sure the index tab is in the key way and touching the retaining ring; reversing the retention spring orientation will result in greater distortion of the optic. Gently turn the retaining ring using a Spanner Wrench until the optic makes contact with the three fingers on the faceplate. For our Ø1/2" mounts, the SPW603 spanner wrench should be used; for the  Ø1" and Ø25 mm mounts, either the SPW602 or SPW606 may be used; for our Ø2" and Ø50 mm mounts our SPW604 may be used.

Securing Optics by Turning Back the Retaining Ring
Continue to tighten until the spring is fully compressed into the pocket of the retaining ring. At this point, the retaining ring will make slight contact with the back of the optic. Loosen the retaining ring in increments of one quarter to one half a turn until the spring pressure alone holds the optic in place (for suggested mount-specific increments, see graphs below). This will put the appropriate force on the optic, resulting in an additional distortion of a few hundredths of a wave for a mounted optic compared to the optic in its unmounted state. The ideal number of turns to loosen the retaining ring depends on the mount used and the application.

Securing Optics with a Torque Driver
Alternatively, the TD24 torque driver along with a Spanner Bit can be used to apply the appropriate torque to the retaining ring when screwing it into the mount. The torque applied to the retaining ring translates to a force applied to the optic; this mounting process imparts a sufficient mounting force while minimizing the optic distortion. For the proper torque setting, please refer to the graphs below.

While the results when using a torque driver on the smaller mounts can be similar to that of loosening the retaining ring, it can be easy to over- or underestimate the amount of torque needed. This can result in securing the optic in the mount too loosely or too tightly, either of which will have a negative effect on the mount’s performance.  

We do not recommend using a torque wrench for mounting an optic in our Ø50 mm or Ø2" Polaris mounts. The increased diameter of the optic cell makes it difficult to get an accurate reading; this can lead to mounting an optic with too much force, resulting in increased distortion of the optic face, or too little force, leaving the optic loose in the mount.

The graphs below show the effect varying amounts of torque or turns of the optic retaining ring have on the surface of a 6 mm thick mirror mounted in a Ø1/2" Polaris mount, a 6 mm mirror mounted in a
Ø25 mm or Ø1" Polaris mount, or a 12 mm thick mirror mounted in a Ø50 mm or Ø2" Polaris mount. The shaded regions below illustrates the acceptable range of turns back depending on application. Setups prone to vibration should be exposed to minimal turns back, while stationary setups may require more turns back. All flatness measurements are taken with a ZYGO interferometer, which uses a 633 nm beam. Please see the Low Distortion tab for more information on optic face distortion as a result of torque.

Ø1/2" Low-Distortion Mounts

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The dashed line indicates 0.10λ for reference. The shaded region represents the recommended torque range. 0.5 turns back from optic contact is recommended for secure mounting with minimal additional distortion caused by the mount. The black dots represent the torque and flatness yielded by using a standard spanner wrench and then loosening the retaining ring the number of turns indicated by the number below the dot. Data for torque values above the shaded region are given for reference and will yield distortion values significantly higher than 0.1 waves.

Ø25 mm Low-Distortion Mounts

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 The data above shows the optic distortion for a 6 mm thick mirror mounted in the
POLARIS-K25F4/M mount. The dashed line indicates 0.10λ for reference. A range of a half to two turns back from optic contact is suggested for secure mounting with minimal additional distortion caused by the mount. However, this can vary based on the application.

Ø50 mm Low-Distortion Mounts

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The data above shows the optic distortion for a 12 mm thick mirror mounted in the
POLARIS-K50F4/M mount. The dashed line indicates 0.10λ for reference. A range of one to two turns back from optic contact is suggested for secure mounting with minimal additional distortion caused by the mount. However, this can vary based on the application.

Ø1" Low-Distortion Mounts

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The data above shows the optic distortion for a 6 mm thick mirror mounted in a
Polaris^® Ø1" Low-Distortion Mount. The dashed line indicates 0.10λ for reference. 1.25 turns back from optic contact is recommended for secure mounting with minimal additional distortion caused by the mount.

Ø2" Low-Distortion Mounts

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The data above shows the optic distortion for a 6 mm thick mirror mounted in a Polaris^® Ø2" Low-Distortion Mount. The dashed line indicates 0.10λ for reference. 1.25 turns back from optic contact is recommended for secure mounting with minimal additional distortion caused by the mount. The error bars signify the standard deviation of the test results at every 0.25 turn interval. The spring will start to disengage from the optic at 3.25 turns back

Mounting stresses are responsible for the strain on an optic that results in optic distortion. Minimizing distortion effects is crucial; any distortion to the optic is transmitted to the light that is reflected from it.

Placing the 3-point mounting forces perpendicular to the face of the optic and indexing them directly opposite each other minimizes bending moments on the optic, thus reducing optic distortion. Typical 360° face mounts and side-located setscrew mounts create bending moments that cause optic distortion as seen in the drawings below. Spring loading the optic allows one to gradually tune the retention force, dampening stresses caused by temperature changes, and it provides a soft means of compensating for variances in manufacturing that can further produce stress on the optic. The finite element analysis results shown below show the displacement, stress, and strain applied to the optic for 20 oz-in of torque applied to the retaining ring of our POLARIS-K05F6 and POLARIS-K1F mounts, and 10 oz-in of torque applied to the setscrew of the equivalent standard setscrew mount. The POLARIS-K05F1 and POLARIS-K05F2 use the same front plate as the POLARIS-K05F6 and will show similar performance. The POLARIS-K25F4/M, POLARIS-K1F1, POLARIS-K1F2, POLARIS-K50F4/M, and Ø2" low-distortion Polaris mounts also have a similar design and therefore will show similar performance to the POLARIS-K1F.

Simulation Results for POLARIS-K05F6 Ø1/2" Low-Distortion Mount*

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* The POLARIS-K05F1 and POLARIS-K05F2 low-distortion Polaris mounts will show similar performance to the POLARIS-K05F6.

Simulation Results for POLARIS-K1F Ø1" Low-Distortion Mount*

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* The POLARIS-K25F4/M, POLARIS-K1F1, POLARIS-K1F2, POLARIS-K50F4/M, and Ø2" low-distortion Polaris mounts will show similar performance to the POLARIS-K1F.

Optical Distortion Testing Using a ZYGO Phase-Shifting Interferometer

A ZYGO Phase-Shifting Interferometer was used to perform wavefront distortion measurements on all Polaris Low-Distortion Mirror Mounts. The results of these tests can be found below.

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Ø1/2" Mounts

Procedure
A BB05-E02 Ø1/2" Broadband Dielectric Mirror was installed into a POLARIS-K05F6 Low-Distortion Kinematic Mount using the procedure detailed in the Optic Installation tab; that is, the retaining ring was tightened until the spring was fully compressed, and then the retaining ring was turned back a half turn. The mount was then secured to a Ø1" stainless steel post using an 8-32 cap screw tightened to a torque of 16 in-lb. The Zygo interferometer aperture outer diameter was set to 80% for these measurements. 

Results
As seen in the image to the right, the wavefront distortion was found to remain at or below 0.1λ.

Ø25 mm Mounts

Procedure
A custom Ø25 mm Broadband Dielectric Mirror was installed into a POLARIS-K25F4/M Low-Distortion Kinematic Mount using the procedure detailed in the Optic Installation tab; that is, the retaining ring was tightened until the spring was fully compressed, and then the retaining ring was loosened incrementally. The mount was then secured to a Ø1" stainless steel post using an 8-32 cap screw tightened to a torque of 16 in-lb. Results of each measurement are provided in the table to the right.

Results
As seen in the table to the right, the wavefront distortion was found to remain below 0.1λ.

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Retaining Ring Turned Back a 1/4 Turn

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Retaining Ring Turned Back a 1/2 Turn

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Retaining Ring Turned Back a 3/4 Turn

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Retaining Ring Turned Back 1 Turn

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Retaining Ring Turned Back 1.25 Turns

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Retaining Ring Turned Back 1.5 Turns

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Retaining Ring Turned Back 1.75 Turns

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Retaining Ring Turned Back 2 Turns

Ø1" Mounts

Procedure
A BB1-E02 Ø1" Broadband Dielectric Mirror was installed into a POLARIS-K1F Low-Distortion Kinematic Mount using the procedure detailed in the Optic Installation tab; that is, the retaining ring was tightened until the spring was fully compressed, and then the retaining ring was loosened incrementally. The mount was then secured to a Ø1" stainless steel post using an 8-32 cap screw tightened to a torque of 16 in-lb. Results of each measurement are provided in the table to the right.

Results
As seen in the image to the right, the wavefront distortion was found to remain at or below 0.1λ.

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Retaining Ring Turned Back a 1/4 Turn

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Retaining Ring Turned Back a 1/2 Turn

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Retaining Ring Turned Back a 3/4 Turn

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Retaining Ring Turned Back 1 Turn

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Retaining Ring Turned Back 1.25 Turns

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Retaining Ring Turned Back 1.5 Turns

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Retaining Ring Turned Back 1.75 Turns

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Retaining Ring Turned Back 2 Turns

Ø50 mm Mounts

Procedure
A custom Ø50 mm Broadband Dielectric Mirror was installed into a POLARIS-K50F4/M Low-Distortion Kinematic Mount using the procedure detailed in the Optic Installation tab; that is, the retaining ring was tightened until the spring was fully compressed, and then the retaining ring was loosened incrementally. The mount was then secured to a Ø1" stainless steel post using an 8-32 cap screw tightened to a torque of 16 in-lb. Results of each measurement are provided in the table to the right.

Results
As seen in the table to the right, the wavefront distortion was found to remain below 0.1λ.

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Retaining Ring Turned Back a 1/4 Turn

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Retaining Ring Turned Back a 1/2 Turn

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Retaining Ring Turned Back a 3/4 Turn

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Retaining Ring Turned Back 1 Turn

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Retaining Ring Turned Back 1.25 Turns

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Retaining Ring Turned Back 1.5 Turns

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Retaining Ring Turned Back 1.75 Turns

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Retaining Ring Turned Back 2 Turns

Ø2" Mounts

Procedure
A BB2-E02 Ø2" Broadband Dielectric Mirror was installed into a POLARIS-K2F Low-Distortion Kinematic Mount using the procedure detailed in the Optic Installation tab; that is, the retaining ring was tightened until the spring was fully compressed, and then the retaining ring was loosened incrementally. The mount was then secured to a Ø1" stainless steel post using an 8-32 cap screw tightened to a torque of 16 in-lb. Results of each measurement are provided in the table to the right.

Results
As seen in the table to the right, the wavefront distortion was found to remain at or below 0.133λ.

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Retaining Ring Turned Back a 1/4 Turn

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Retaining Ring Turned Back a 1/2 Turn

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Retaining Ring Turned Back a 3/4 Turn

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Retaining Ring Turned Back 1 Turn

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Retaining Ring Turned Back 1.25 Turns

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Retaining Ring Turned Back 1.5 Turns

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Retaining Ring Turned Back 1.75 Turns

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Retaining Ring Turned Back 2 Turns

Positional Repeatability After Thermal Shock

This testing was done to determine how reliably the mount returns the mirror, without hysteresis, to its initial position so that the alignment of the optical system is unaffected by the temperature shock. During the testing phase, the Polaris kinematic mirror mount was attached to a Ø1" stainless steel post secured to a stainless steel optical breadboard in a temperature-controlled environment. Each mount was secured to the post by an 8-32 cap screw with 16 in-lb of torque. The mirror was mounted (not glued) in the mirror mount, and 8 oz-in of torque was applied to the retaining ring for the Ø1/2" and Ø1" mounts. The Ø2" mounts had the retaining ring backed out by 1.25 turns from optic contact; please see the Optic Installation tab for why a torque wrench was not used with our Ø2" mounts. The beam from an independently temperature-stabilized diode laser was reflected off the mirror’s surface onto a position sensing detector. 

Procedure:
The temperature of each mirror mount tested was raised to 37 °C. The elevated temperature was maintained in order to soak the mount at a constant temperature. Then the temperature of the mirror mount was returned to the starting temperature. The results of these tests are shown below.

Results:
As can be seen in the plots in the expandable tables below, when the Polaris low-distortion mounts were returned to the initial temperature, the angular position (both pitch and yaw) of the mirrors returned to within 2 µrad of the initial position. The performance of the Polaris mounts was tested further by subjecting each mount to repeated temperature change cycles. After each cycle, the mirror’s position reliably returned to within 2 µrad of its initial position.

For Comparison:
To get a 1 µrad change in the mount’s position, the 100 TPI adjuster on the POLARIS-K1F 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.

Click to Enlarge 3-Adjuster Low-Distortion Mount

Click to Enlarge 2-Adjuster Low-Distortion Mount

Click to Enlarge The plot above shows the final angular position of the POLARIS-K05F2 for 40 consecutive thermal shock tests. The change in temperature is the difference between the starting temperature and the temperature at the end of the test and includes factors such as the variation in room temperature.

Click to Enlarge 3-Adjuster Low-Distortion Mount

Click to Enlarge The plot above shows the final angular position of the POLARIS-K1F for 10 consecutive thermal shock tests. The change in temperature is the difference between the starting temperature and the temperature at the end of the test and includes factors such as the variation in room temperature.

Click to Enlarge 2-Adjuster Low-Distortion Mount

Click to Enlarge Click to Enlarge The plots above show the final angular position of the POLARIS-K1F1 and POLARIS-K1F2 for 20 consecutive thermal shock tests. The change in temperature is the difference between the starting temperature and the temperature at the end of the test and includes factors such as the variation in room temperature.

Click to Enlarge 3-Adjuster Low-Distortion Mount

Click to Enlarge The plot above shows the final angular position of the POLARIS-K2F for 20 consecutive thermal shock tests. The change in temperature is the difference between the starting temperature and the temperature at the end of the test and includes factors such as the variation in room temperature.

Click to Enlarge 2-Adjuster Low-Distortion Mount

Click to Enlarge The plot above shows the final angular position of the POLARIS-K2F1 for 20 consecutive thermal shock tests. The change in temperature is the difference between the starting temperature and the temperature at the end of the test and includes factors such as the variation in room temperature.

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Design Features of the Polaris Low Distortion Mounts

Several common factors typically lead to beam misalignment in an optical setup. These include temperature-induced hysteresis of the mirror's position, crosstalk, drift, and backlash. Polaris mirror mounts are designed specifically to minimize these misalignment factors and thus provide extremely stable performance. Hours of extensive research, multiple design efforts using sophisticated design tools such as finite element analysis software, and months of rigorous testing went into choosing the best components to provide an ideal solution for experiments requiring ultra-stable performance from a kinematic mirror mount.

Thermal Hysteresis
The temperature in most labs is not constant due to factors such as air conditioning, the number of people in the room, and the operating states of equipment. Thus, 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), like 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 a temperature-dependent hysteresis. As a result, the alignment of the optical system will be restored when the temperature of the mirror mount is returned to the initial temperature.

The method by which the mirror is secured in the mount is another important design factor; these Polaris mounts offer excellent performance without the use of adhesives. Instead, they have a three-point-contact faceplate, an indexed retention spring, and a stainless steel retaining ring that hold the optic in place. This design minimizes distortion on the optic surface while maintaining beam pointing stability.

Crosstalk
Crosstalk is minimized by carefully controlling the dimensional tolerances of the front and back plates of the mount so that the pitch and yaw actuators are orthogonal. In addition, sapphire seats are used at all three contact points. Standard metal-to-metal actuator contact points will wear down over time. The polished sapphire seats of the Polaris mounts, in conjunction with the hardened stainless steel actuator tips, maintain the integrity of the contact surfaces over time.

Drift and Backlash
In 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 squeezed out of some spaces and built up in others. This non-equilibrium distribution of lubricant will slowly relax back into an equilibrium state. However, in doing so, this may cause the position of the front plate of the mount to move. The Polaris mounts use adjusters matched to the body that exceed all industry standards so very little adjuster lubricant is needed. These adjusters have a smooth feel that allows the user to make small, repeatable adjustments.

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Polaris Mounts are Shipped Inside Two Vacuum Bag Layers

Cleanroom and Vacuum Compatibility
All Polaris mounts, retaining rings, and lock nuts sold on this page are designed to be compatible with cleanroom and vacuum applications. They are chemically cleaned using the Carpenter AAA passivation method to remove sulfur, iron, and contaminants from the surface. After passivation, they are assembled in a clean environment and then double vacuum bagged, as shown in the image to the right, to eliminate contamination when transported into a cleanroom.

The sapphire contacts are bonded into place using a NASA-approved low outgassing procedure. In addition, DuPont LVP High-Vacuum (Krytox) Grease, an ultra-high-vacuum-compatible, low outgassing PTFE grease, is applied to the adjusters. These features provide high-vacuum compatibility and low outgassing performance. Please note that the 8-32 and M4 cap screws included with the Polaris mounts are not rated for pressures below 10^-5 Torr.

The vacuum bags do not contain any desiccant materials and tightly wrap the mount, preventing friction against the mount during shipping. This packing method protects the mount from corrosion, gas or liquid contamination, and particulates during transport. The first vacuum bag should be opened in a clean environment while the second vacuum bag should only be opened just prior to installation. When operating at pressures below 10^-5 Torr, we highly recommend using an appropriate bake out procedure prior to installing the mount in order to minimize contamination caused by outgassing.

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POLARIS-K05F6 mounted on a Ø1", stainless steel
pedestal post.

Polaris kinematic mirror mounts are specifically designed to provide excellent performance under thermal changes and vibrations. Below are some usage tips to ensure that the mount provides optimal performance.

Match Materials
Due to its relatively low coefficient of thermal expansion, stainless steel was chosen as the material from which to fabricate the front back plates of the Polaris mounts. When mounting, we recommend using components fabricated from the same material, such as our Ø1" stainless steel posts of posts.

Mounting Options
If post mounting a Polaris mount, we recommend using a stainless steel post such as our Ø1" stainless steel posts or Ø1" post extensions with our POLARIS-CA1 Clamping Arm. By choosing components fabricated from the same material as the mount itself, all expansions and contractions will occur at the same rate. In addition, it is best to use the shortest post possible. Alternatively, mount the Polaris directly onto a flat surface such as a breadboard using a 1/4"-20 to 8-32 thread adapter (Item # AE8E25E) or M6 to M4 thread adapter (Item # AE4M6M), which results in even better performance. Ensure that the mounting surface is highly flat, polished, and free of debris or scratches.

Mount Alignment
During alignment, minimized deflection will be achieved if the mount's front plate is kept parallel to the base plate. This ensures even thermal expansion of all the adjustment screws, causing the mounted mirror to translate in the Z direction as opposed to rotating during temperature changes.

Front Plate’s Position
Although the mount is designed to allow adjustments of up to 6.8° for the Ø2" mounts, 8° for the Ø1" mounts, and 10° for the Ø1/2" mounts, to achieve the best performance, it is recommended that the front plate be kept as parallel as possible to the back plate. This ensures the highest stability of the adjustments.

Polish and Clean the Points of Contact
We highly recommend that the points of contact between the mount and the post, as well as the post and the table, are clean and free of scratches or defects. For best results, we recommend using a polishing stone to clean the table’s surface and a polishing pad for the top and bottom of the post as well as the bottom of the mount.

Not Recommended
We do not recommend taking the adjusters out of the body, as it can introduce contamination to the threading, which can consequently reduce the fine adjustment performance significantly. Also, do not pull the front plate away as it might stretch the springs beyond their operating range or crack the sapphire seats. Finally, do not over tighten the retaining ring that secures the indexed spring that holds the optic in place; only slight force is required to secure the optic in place. For more information, please see the Low Distortion tab. Do not adjust or remove the spring-loaded ball contact in the faceplate of the Ø1" or Ø2" Polaris mounts; the correct position is set at the factory.

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Adjuster Lock Nuts
The 3-adjuster POLARIS-K05F6 and 2-adjuster POLARIS-K05F2 come with lock nuts pre-installed. For Polaris mounts that do not include lock nuts, the POLARIS-LN05 and POLARIS-LN1 lock nuts are available separately below. Lock nuts only need to be lightly tightened to a torque of approximately 4 to 8 oz-in (0.03 to 0.06 N·m). The beam can be held on target with the adjuster thumbscrew or hex key while lightly tightening the lock nut by hand or with a thin-head wrench or cone wrench. To avoid cross threading the lock nut, place it against the adjuster and "unscrew" the lock nut until you feel a slight drop; then thread the lock nut onto the adjuster. Each lock nut is pre-greased with the same ultra-high-vacuum-compatible, low-outgassing PTFE grease as the Polaris mounts and has been tested for adjuster fit.

Low Incident Angles
The recessed edge of our Polaris Low-Distortion Mounts make them ideal for applications requiring low angles of incidence. The illustration to the right shows two Polaris Low-Distortion Mounts with Ø1/2" mirrors (green) used at a near-normal incident angle.