What to Consider When Choosing a Microscope Camera

Thanks to recent advances in technology, there are many interesting microscopy-dedicated cameras available on the market. Here, we summarize the current methods and technologies used by these cameras as a guideline for achieving high-quality images and maximizing the benefits of the latest techniques for your observations and experiments.

Key Elements of Image Quality

The most important factor in ensuring successful microscopic imaging is choosing the appropriate optics and camera for your application. For example, an sCMOS (scientific complementary metal-oxide semiconductor) camera is a great choice for most fluorescence imaging but unsuitable for long-exposure applications, such as bioluminescence imaging. The following sections detail the major elements to consider regarding microscope camera capabilities and advantages according to the application.

Resolution

Microscopes can be used to observe tiny structures that are difficult to resolve optically. These optical limitations mean that a higher number of pixels or smaller pixel pitch does not always provide higher resolution. The key to achieving better resolution is to select the proper pixel pitch in relation to the numerical aperture (NA), the total magnification of the optical system, and the sample’s spatial frequency. Fig.1 is a schematic of the modulation transfer function (MTF) demonstrating the response of an imaging system with a 500 nm light and 5 μm pixel pitch. Fig.1(a) indicates that the sensor’s Nyquist frequency, which is half of the sampling frequency or the reciprocal of the pixel pitch of the sensor, is lower than the optical cutoff frequency, which is defined in Eq.1. In this case, it is worth trying a smaller pixel pitch to achieve higher resolution. On the other hand, in the case of Fig.1(b) and (c), a smaller pixel sensor cannot provide higher resolution because the light from the sample has been spread much larger than the pixel pitch in a point spread function (PSF) manner of the optical system. A sample’s spatial frequency should also be carefully considered. Industrial samples often have sharp edges, which means that they feature higher spatial frequencies than biological samples and require a higher sampling pitch.

Figure 1 – MTF plot (left) and schematic figure (right) to explain the relation between PSF and the pixel pitch. (a) 10x NA 0.4, (b) 10x NA 0.2, (c) 40x NA 0.9

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