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Important Concepts for Selecting Optical Component Mounts

Edmund Optics offers a variety of kinematic, bar-type, translating, ring, and modular mounting components. Before selecting which optical mount is best for your application, it is important to consider the types of adjustment required, how finely the adjustment must be made, and the total adjustment range needed. Katie Schwertz, Design Engineer, reviews degrees of freedom, tips for precision alignment, and a host of other important concepts for optical component mounts.

Hi, I am Katie, one of the Opto-Mechanical Engineers here at Edmund Optics. Today, I want to talk about some of the common types of mounts we offer for optical components and what things to consider when selecting a mount. Before choosing a mount, it is important to first determine what type of adjustment, if any, is required for the optical component. It is also important to consider how finely the adjustment must be made and the total adjustment range available. We refer to the different translation and rotation adjustments that are available as degrees of freedom. Every object has 6 degrees of freedom. In a standard coordinate system, these degrees of freedom are translation in X, Y and Z, and rotation about the X, Y and Z axes as seen in this diagram. In optics, we typically assume the Z-axis is along the optical axis. To hold an optical component with the greatest precision and without causing stress or deformation, all 6 degrees of freedom should be constrained. However, adjustment in some of these degrees of freedom is commonly desired for alignment purposes, and this is something you should consider for your application. Kinematic mounts, also commonly referred to as Tip-Tilt mounts, are a common mounting solution when precision alignment is needed. These types of mounts come in several varieties. For circular, a rectangular optics, with C-mount and T-mount threading, or with 2 or 3 adjustment screws. The 2-adjustment screw mount allows the optic to be tilted around the X and the Y-axis. The kinematic mounts with a third adjustment screw also offer translation in the optical axis, the Z-axis. We also offer a 45-degree adapter that interfaces directly with our kinematic mounts, ideal for mounting mirrors or beamsplitters to create a 90-degree reflection. If you mount any of these on a post, you can add coarse Y translation or rotation. Our C-mount and T-mount threaded lens mounts are cells with the center hole designed to accept single element lenses, filters, reticles and other optical components. A threaded retaining ring is used to fully constrain the element in the cell. They are available in a variety of sizes and are easy to integrate into other mounts for ease of alignment. Our most basic optic mounts are bar-type mounts, as seen here, which can each hold optical components of varying sizes. We offer these types of mounts for either circular or rectangular optics. Bar-type mounts fully constrain the optic without adjustment options. However, coarse Y translation and Y rotation can be achieved with the post movements. Our X Y translating optic mounts provide fine adjustments in the X and Y axes for when your application requires precise alignment and centering. The X, Y, Z translating optical mounts are similar with the added functionality of a Z-axis adjustment. Another type of optical mount is the 3 screw adjustment mount, which can hold varying diameter optical components, cell assemblies and laser tubes. This mount offers coarse X and Y translation by de-centering the optical component within the mount. Again, coarse Y rotation and translation can be achieved with a post, but there is no X or Z rotation or Z translation with this type of mount. Similarly, we offer a self-centering jaw clamp, this mount offers no adjustment alone, but the kinematic mount offers tilt around the Y-axis, and tip around the X-axis. A common way to mount prisms and beamsplitters is to use a table with a clamping arm, as you can see here. The Edmund Optics catalog refers to this type of mount as a prism holder. For precision rotation, which is commonly required for accurate orientation of polarizing materials and other optical components, we offer rotary optic mounts. These mounts provide rotation about the Z-axis. I hope this answers some of your questions about different mounting options for optical components, and how to choose one for your needs. This was just a brief overview of some of our optical mounts. To see more mounting options, including gimbal mounts, prism mounts and miniature mounts, please visit our website. You can browse more of our technical application notes and videos to learn more key concepts and find answers to common questions on our website.