Important Concepts for Selecting Manual Translation Stages
Edmund Optics offers a variety of ball bearing, crossed roller bearing, dovetail, and rack and pinion translation stages for linear translation, rotary, and tip-tilt movement. Before selecting which translation stage 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. Join Katie Schwertz, Design Engineer, as she reviews degrees of freedom, mechanical movement, translation stage construction, and a host of other important concepts for manual translation stages.
Hi, I am Katie, one of the Opto-Mechanical Engineers here at Edmund Optics. Today I want to talk about some of the basic types of manual stages we offer, and what things to consider when selecting a stage. The main types of stages are linear translation, rotary, and tip-tilt. Before choosing a stage, it is important to first consider what type of adjustment is required for your application, as well as 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. Let's take a look at a few types of stages. Linear stages provide translational motion in the X, Y, or Z-axis and some can be stacked to provide motion in a combination of these directions. You can find out more about how to stack stages in the video "Multi-Axis Stage Configurations." When using a linear stage, there are several options to consider. We offer dovetail stages, ball bearing stages, rack and pinion stages, and crossed roller bearing stages. Dovetail stages are the simplest stages composed of a base and a rail that interlock to allow the stage to slide against the rail. You can see this mechanism in both this small stage, as well as our large rail and carrier system. This configuration is very stable and allows for large load capacities and long travel. However, precise control is difficult with these types of stages due to the amount of friction, so they are best for coarse positioning. Rack and pinion stages are a type of dovetail stage that have translation knobs on one or both sides of the stage. Each rotation of the knob causes the circular pinion to engage teeth on a linear gear, or the rack, converting the rotational motion into a specific increment of linear travel. The sawtooth gear pattern between the stage and track allows for coarse positioning along the length of the track with moderate load capacity. Ball bearing stages are mechanically simple stages that consist of a stationary base with a mobile carrier on top. On either side of the base there are rows of steel balls guided by V-grooves or rods to provide accurate sliding motion of the stage. Ball bearing stages have low friction due to the point contact between the bearing and the rods, so they provide smooth, precise movement and reduce wear problems while still providing moderate load capacity and added positioning reliability over dovetail stages. Crossed roller stages operate similarly to ball bearing stages, but feature orthogonally alternating cylindrical rollers that provide a line contact instead of a point contact. This provides higher accuracy, rigidity, and load capacity, but this is a trade off with a higher cost. A unique stage available from Edmund Optics featuring crossed roller bearings is a ‘lift style’ vertical translation stage. This type of stage can be used independently, or several linear translation stages can be combined to provide this versatility. If you need rotational movement, typically around the Y-axis, the best option is to use a rotary stage. Rotary stages are available with varying precision, from coarse adjustments to precise angular movement with a micrometer. Other options to provide rotational motion in different axes include tip-tilt stages and goniometers. Tip-tilt stages provide slight rotation around the X and Z axes with micrometer precision. They can be stacked with other stages to provide multi-axis adjustments. Goniometers provide rotation about a fixed point above the center of the mounting surface. The advantage of goniometers is that the motion is purely rotational as opposed to traditional tip-tilt stages, which incur a small translation when adjusted. Goniometers are recommended for applications where high-precision rotational adjustments are required – for example with critical beam steering applications. The goniometers available from Edmund Optics are also stackable for two-axis rotation. I hope this answers your questions about some of the different types of stages we offer, and which suit your needs. To see more stage options, including lab jacks, which provide coarse lifting motion, micro positioners, and motorized stages, 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 also on our website.