Technical Note:
Advantages of New Focus Mirror Mounts

When we design our mirror mounts, we strive to make mounts that provide precision adjustments that really stay put. To give you the ultimate in precision, one of our design criteria is to approach the textbook definition of kinematic—where there exists precisely one constraint or actuator for each independent degree of freedom. That’s why we use a cone-vee-flat configuration. To provide even more precision and durability, we use sapphire seats to ensure that repetitive adjustments do not leave tracks that would make positioning non-kinematic, and therefore non-deterministic and imprecise.

Then, to ensure the mounts have exceptional long-term stability, we use a proprietary screw-assembly process with very tight tolerances to minimize slop. We limit the amount of grease in the actuators to reduce migration over time and from temperature variations. This results in mounts with very smooth movement and high precision, as well as exceptional long-term and thermal stability. In our commercial versions, our unique lock system allows us to maintain this smooth feel without adding grease or increasing costs. Just compare one of our screws with one from another company—you’ll notice the difference right away.

Also, because we know that stability can make all the difference in your experiment, we designed our Classic 1" mount with a thick 5/8" frame and our Classic 2" center mount with a 3/4" frame! Compare any of our mounts to comparably priced versions from our competitors and you’ll find that we have the thickest frames. Even our Tiny mounts are made of stiff stainless steel to achieve greater stability for their size. The graphs to the right show our mounts compared to the competition. The graph on the top shows that our mounts have a smaller deflection for all applied forces so your experiment will be easier to align. The graph on the bottom shows that as an impact force is applied to the mounts, our mounts remain in place while the others misalign.

If you’d like to see for yourself, try the “snap” test with one of our mounts in your lab. Put the mount in an interferometer and “snap” the mount joints by separating them and letting them snap back. This will give you an indication of the quality of the construction of the mount. With sapphire seats, thicker frames, and stiffer springs, our mounts should return to the same starting position, which will translate into excellent thermal stability.
We know you’ll be pleased when you try our mounts. You’ll find that the extra stability and higher resolution will save you both time and frustration.

99-9807 Force vs Deflection
Force vs. deflection graph comparing our mount (shown in light blue) with competitors’ mounts as force is applied to their frames. Our mount deflects much less under all applied forces, making your experiment easier to align.
99-Impact comparisons
The deflection of our mount (shown in blue) and two competitors after impact by a small force. While the other mounts move, creating misalignment, ours remains undeflected. This was measured using
a HeNe laser beam and a quad-cell photodetector.

Complete Compatibility

All our mounts and positioners are designed for use with 1/4-20 or 8-32 screws (metric M6 or M4). Therefore, they are completely compatible with other mounts already in your lab. Also, we have intentionally offset the optic center of our corner mounts 1" (25.4 mm) from that of our center mounts so that they may be easily used together. Rest assured that total integration is not a problem.

How They Work

Turning a single knob tilts the optic with slight translation. In our gimbal mounts there is a 2.5-µm translation for a 1° tilt. For our conventional mounts, one degree of tilt results in 0.35-mm translation. Turning two adjacent knobs an equal amount produces pure tilt in our three-knobbed corner mounts like our Model 9809 classic corner mount. Turning all three knobs an equal amount results in pure translation along the optical axis. A 1° error in one knob results in only 0.0012° tilt in the face plate. The sapphire seats and other design innovations used in our precision mounts result in true kinematic positioning. Using sapphire as the bearing surface for our ball-tipped screws ensures that repetitive adjustments do not leave tracks that make positioning nondeterministic. Also, our 1/4-80 screw sets are made with great precision, so very fine adjustments can be made consistently.