Wednesday, June 14, 2017

Microscope Magnification versus Resolution

In microscopy there are two concepts that many people often think of as a single concept, but they are very different. These two concepts are magnification and resolution. From a technical perspective, resolution is a quantified concept that is defined by the numerical aperture (NA) rating of the objective lenses of the microscope. Numerical Aperture is a number that expresses the ability of a lens to resolve fine detail in an object being observed. Magnification is simply how much an image is enlarged.

Below are two images of the same small printed part with text on it. The first image was captured using a stereo microscope with a lens that has NA of 0.10. This image was captured at 90x. Notice in the image below captured with the stereo microscope it is very hard to even read any of the printed text on the circuit. It should also be noted that it took nearly two hours to capture an image of this quality.

Image of a circuit captured under a stereo microscope at 90x magnification.
Stereo Microscope image captured at 90x, NA 0.10

The next image was captured using a metallurgical microscope with a lens that has NA of 0.30 and a magnification of 100x. This image took a few minutes to capture. The magnifications of the two captured images are similar however, notice how much easier it is to read the printed letters in the image that was captured with the metallurgical microscope. That ability is due to better resolution, which was obtained because of a higher numerical aperture of the lens used.

Metallurgical microscope image of a circuit captured at 100x magnification showing high quality resolution.
Metallurgical Microscope image captured at 100x, NA 0.30

Contact Microscope World with questions regarding NA, resolution, magnification or any other microscopy related questions.