Five Inverted-Microscope Advantages for Industrial Applications

With an inverted microscope, once a sample is placed on the stage and its surface is brought into focus, then it can be easily exchanged with all other samples, even if they differ greatly in height and size. With parfocal objectives, the sample surface stays in focus for all magnifications independent of the sample placed on the stage.

With an upright microscope, for samples which differ greatly in height and size, users often need to cut off a smaller piece from the large object to use as a sample and then mount/embed it in resin. If both sides of a mounted (resin-embedded) sample are not closely parallel and the goal is to search over a large area of the prepared sample surface with the microscope, then some refocusing may be required at times, depending on the magnification. Because it is advantageous that the surface stays in focus as the sample is moved laterally around on the microscope stage, then to achieve this goal:

1. the sample must be placed on a holder with a putty- or clay-like material where the prepared surface is up;
2. the prepared surface must be covered with a clean lint-free paper or cloth, so it does not get dirty; and
3. then the sample surface must be leveled with a press.

So clearly much more time is required to observe multiple samples, especially if they have to be mounted in resin. For inexperienced users, changing of samples which vary in height on an upright microscope can be challenging until they become accustomed to it.

Even for an experienced user operating an upright microscope who can change samples relatively quickly, assuming only 5 seconds per step, still using an inverted microscope would be overall much faster. In table 1 below, an example involving observation of multiple samples and which compares working with an upright versus an inverted microscope, such as the DMi8, is shown.

Table 1: Comparison of steps for preparing and changing tall, large samples for both upright and inverted microscopes. N.B.: The time needed for mounting the sample in resin, grinding and polishing of the sample surface, and searching the surface for areas of interest with the microscope are excluded here.

If you observe a sample with an upright microscope, your brain has some extra work to do: When you move the sample or stage to the left or the right, the image of the sample that you see through the eyepieces moves the opposite way, i.e. right or left, due to the design and light path of the microscope.

If you observe a sample with an inverted microscope, such as the DMi8, the movement of the sample and its image are always in the same direction. It behaves the same way as when you observe the world without a microscope. Especially for low-experience users, this fact is a big help for their work, because they do not have to think carefully about the direction in which they want to move the sample, but just do it. So, it saves users time and speeds up their workflow.

N.B.: With many upright microscopes, there is usually a higher-cost option to install an eyepiece tube with special optics that can invert the image of the sample, so it is in the same orientation as the sample on the stage. Additionally, the use of a digital camera with any microscope allows the sample image to be observed on a monitor and the image orientation can be easily changed to the same as the sample with the imaging software.