Confocal microscopy involves moving the focal plane of a microscope vertically through the sample while acquiring a series of images. The images can later be assembled using software to form an apparent 3-D effect. For biological samples, speed is often an important concern as the lasers used for image scanning can photobleach or damage the sample under prolonged exposure.
Problems Associated with Traditional Confocal Microscopy Imaging Systems
While many standard microscopy stages provide motorized Z-axis motion, their positioning resolution is too coarse and their speed is too slow to successfully image most cellular level objects. One answer to the high speed, high resolution Z-axis positioning problem is the use of mechanisms to vertically move the objective lens. While this method has been adopted and used successfully for some situations, it has some fundamental limitations. The limited space around the objective lens available for the positioning actuator combined with the relatively high mass of the lens means that the ultimate positioning speed is quite limited. Typical systems using this method cannot achieve an imaging rate faster than 20ms per sample. Since each lens requires a matching positioning mechanism, the overall cost can grow quickly as different lenses are added to the inventory.
The Mad City Labs Solution and Its Advantages
The approach adopted by Mad City Labs, the largest U.S. manufacturer of nanopositioning stages, is to mount a high speed Z-axis nanopositioning stage on top of the user’s conventional motorized microscope stage. By keeping the physical profile of the additional stage to an absolute minimum, access to the sample remains unobstructed and the range of motion of the objective lens is not excessively impacted. Because the added Z-axis stage is independent of the chosen objective lens, the overall cost of the system is also minimized. The primary benefit of this approach, however, is the unparalleled level of positioning speed and control. With a resonant frequency in excess of 1 kHz, Mad City Labs model Nano-Z100 can move vertically at rates of 3 to 4 ms per step – five times faster than the typical objective lens positioning mechanism. Internal position sensors constantly transmit position data to the attached controller to form a closed loop feedback system. This results in motion which is highly repeatable and stable throughout the range of travel. Like all nanopositioning stages made by Mad City Labs, the Nano-Z100 uses flexure hinges to provide frictionless, 100% reversible motions into the sub-nanometer realm. Conventional bearing guided stages cannot achieve the same performance because the moving bearing contacts generate an endless assortment of errors at the nanometer level which cannot be corrected or compensated.
Versatility of the Mad City Labs Confocal Microscope Stages
Mad City Labs’ Nano-Z100 stages are available for all major inverted optics microscopes and can easily retrofitted into existing systems. Special designs and adaptations of the Nano-Z100 for specific applications can be accomplished by contacting Mad City Labs’ design engineers.