Synopsis
Many clinicians, when working with digital microscopes, refer to the field of view because it’s easier and represents the size of the area the microscope covers. However, total magnification is still important and when the total magnification is calculated correctly, you achieve optimal results. Ideally, you need to pay attention to the diverse details of the specimen and that can be achieved only at certain magnifications. Total magnification generally multiplies all the magnifications, like the lateral magnification, the magnification of the monitor, and microscope adapter magnifications. To achieve the best view of the specimen details that you need to interpret, it is necessary to calculate the total magnification the right way.
What is Magnification in Digital Microscopy?
In digital light microscopes, with image sensors and no eyepieces, the image is displayed directly on an electronic monitor. This brings a significant change to the usual way the magnification of an object viewed via a microscope is determined. Over the years, there have been various standards that define magnification when viewing an image through a microscope’s eyepieces.
The Purpose of Magnification
Image magnification refers to the apparent size of an object, or in other words, how much larger it appears. A magnified image makes it possible to observe greater details of an object. It allows you to see the image in a way that is not possible when observing with your naked eyes. The purpose of magnification is to provide as much detail as possible, depending on your specific requirements. The level of magnification corresponds to the amount of detail you need to see.
What Is Total Magnification?
You achieve total magnification by multiplying all the individual magnifications. The magnification values printed on objective lenses indicate the actual magnification of the object. In digital microscopy, total magnification is achieved differently than in conventional microscopy. The slide is scanned, and the image can be digitally enhanced. Total magnification in digital microscopy is straightforward, making it easy to navigate through different levels of detail.
Infinity-corrected Microscopes
In modern infinity-corrected microscopes, a tube lens is employed. Here the objective images with the focal length of approximately 200 mm, create the image before the ocular or directly on a camera chip. The magnification (M) of that system equals the focal length (F) ratio
and this is the value that is imprinted on the objective. The objective has no quantifiable magnification.
Finite Distance Microscopes
In finite distance microscopes, when the image goes directly from the objective onto a camera chip, then the magnification (M) is the ratio
If the image is significantly larger than the focal length of the objective, then the object distance is about the focal length (F) and the magnification becomes
How to Calculate Total Magnification?
Magnification is the ratio of the size of the object in an image produced by the optical system to the actual size of the object itself. The lateral magnification MDIS, is defined as:
The upper limit of visual magnification depends on the maximum resolving power of the microscope system. When magnification exceeds the optimal range, no additional details of the sample become visible. This is known as empty magnification. Even within the microscope’s resolving power, the practical level of observable detail also depends on the distance between the display of the image and the observer’s eyes.
Magnification of the Output Device
The magnification on the monitor is also critical. When using a digital microscope, you need to calculate the effective magnification and the size of your sample on your monitor. To determine the total magnification, objective magnification, microscope adapter magnification, CCD chip diagonal dimension, and TV monitor diagonal dimension are vital:
How to Calculate Video Magnification?
The video magnification is determined by dividing the monitor diagonal (in mm) by the CCD chip diagonal (mm). To determine video magnification on a computer monitor, you need to divide the actual image diagonal by the CCD chip diagonal. For example, When the format of a CCD chip is ⅓’’, and the diagonal 9’’, the magnification will be 38.1x. When the format of the CCD chip is 1.0’’ and the diagonal is 27’’, the magnification will be 42.9x.
The Size of the Specimen
The approximate real size of a specimen is determined by dividing the length of the specimen measured on the monitor screen by the total magnification of the monitor.
For example, if the measured length of the specimen is 100 mm and the magnification 271.35x, the real size of the specimen would be:
Total Magnification Vs. Field of View
In digital microscopes, optical magnification cannot typically be calculated due to the absence of eyepieces. Instead, video magnification is relative to the size of the monitor. For this reason, many clinicians refer to the field of view, which is the size of the area the microscope captures and displays on the screen. The field of view can be easily determined by knowing the size of the area you need to inspect.
Conclusion
Total magnification, just as a field of view, is significant in digital microscopy. In working with digital microscopes, clinicians often use field of view because it is easier to handle. A field of view encompasses the working area of the microscope. However, there are times when magnification is necessary and irreplaceable, especially when the task requires interpreting certain details. To work optimally, it is necessary to calculate total magnification properly. Total magnification equals the multiplications of objective magnification, microscope adapter magnification, and video magnification. Magnification in general is the ratio of the dimension of the object in the image and the true dimension of the object. When calculating the total magnification, it is also necessary to consider the size of the monitor and the size of the specimen to get the best possible result.
