Microscope Stages

A microscope stage moves a sample or objective in x, y, or z motion and is typically available as either a single axis, an XY stage, or an XYZ stage. Microscope stages are also commonly referred to as XY tables, linear actuators, motorized stages, or linear translation stages.

XY motion is performed by an XY microscope stage, which is typically a thin, low-profile stage with a central opening for transmissive imaging. XY microscope stages are typically actuated with stepper motors and lead screws, while cutting-edge designs employ a linear motor and a linear encoder on each axis and close a servo feedback loop.

The function of a microscope stage is to securely hold and position the sample being observed. It allows controlled movement in the X and Y directions to focus on different specimen areas accurately. In more advanced microscopes, stages may also provide fine adjustments in the Z direction to enhance focus depth.

Microscope stages are essential for detailed analysis and imaging in a variety of life science and diagnostic applications, such as:

• Cell analysis: Microscope stages allow accurate movement of cells under a microscope for high-resolution imaging.
• DNA sequencing: these stages enable precise sample manipulation, which is needed for efficient processing.
• Microscopy: XY and Z microscope stages enable researchers to explore tissues, bacteria, and other biological samples in depth. Additionally, in automated diagnostics, microscope stages ensure fast and accurate sample positioning for reliable test results.

The mechanical stage is an essential yet often overlooked part of a microscope. Positioned beneath the objective lenses, it serves as the platform for your slides and samples. This component not only stabilizes the slides but also enables precise movement, allowing for smooth adjustments while observing your specimens.

There are three common configurations of the mechanical microscope stage motion hardware. Selecting the best one depends upon the complexity of the particular application.

1. The XY microscope stage moves the sample below a Z stage that is moving the objective or camera. This is the most common configuration. The benefit of this approach is that the image becomes stable after motion more quickly because the microscope slide is only moving on one motorized axis. This means it can be mounted to a sturdy structure instead of a stack of three moving axes whose resonances need to damp. During sample loading, the objective can be moved vertically away from the sample mounting area, which makes changing samples easier. Also, Abbe errors are reduced because the overall stack is shorter. To understand the impacts of Abbe errors on stage positioning, see our Abbe error white paper. This method works for regular or inverted microscope configurations.
   
2. Three motion axes move the object being imaged in X, Y and Z directions while the camera and objective remain stationary. In this situation, the camera is very stable because it is mounted to a rigid surface. The drawback is that the travel required for the Z axis may be longer because the objective-to-imaging sensor distance is fixed. Typically, it requires less travel to move the objective with respect to the imaging sensor or camera.
3. The objective or camera is moved in X, Y and Z directions, while the sample remains fixed. This approach works best when imaging small parts such as a microscope slide. As part size increases, the complexity of this approach also increases. Larger travels tend to require two axes to support a beam that has the vertical focus axis with both the imaging sensor and objective mounted to it.
   

Microscope stage control refers to the system that moves and positions the microscope stage precisely in different directions—typically the X, Y, and Z axes. This control enables accurate, smooth movement of samples under the lens for detailed examination, crisp, in-focus images, and analysis.

In advanced setups, stage control may be automated or motorized, allowing for programmable positioning, critical for high-throughput applications like cell sorting, tissue scanning, genomic research, and automated diagnostics. This ensures repeatability and precision in life science and clinical workflows.

A digital microscope uses a digital camera rather than a traditional eyepiece. An image of the sample is observed and analyzed directly on an electronic monitor display in real time.

Modern biomedical, life science and diagnostic instruments rely on automated digital microscope technologies. DNA sequencers, cell imaging instruments, and digital pathology scanners are just a few of the many applications for digital microscopy solutions. When designing these complex systems, there are a lot of options to consider which involve tradeoffs in performance, throughput, and cost.

Once the optical imaging elements are selected, the mechanical microscope stage architecture can be finalized. A typical field of view is much smaller than the sample being imaged. Thus, in order to image an entire sample, either the sample or the camera/objective will need to move along two perpendicular axes (XY). In addition, in order to properly resolve the image, the distance between the magnification objective and the camera (or image sensor) needs to be precisely adjusted. This is referred to as the Z axis. The Z axis is typically vertical and motion along it occurs perpendicular to the XY plane to move the sample into the imaging field of view.

The microscope field of view calculation relates the sensor size to the magnification and will determine how many XY movements will be required to image the area of interest on the sample.

Automated microscope focus axes typically use piezo or direct drive technology. In a microscope stage, direct drive linear motors offer extended range, allowing the objective to be retracted during sample load and unload, together with very high resolution and repeatability. The focus axis position is typically commanded by an autofocus sensor, which derives a focus error signal via a laser diode passing through the objective or by a software autofocus algorithm.