Bright / dark field of view: BD Plan Apo SL

Note: these objective lenses have very long working distance.

When choosing the objective lens, I don't understand some professional terms very well. The field of view of the objective lens is a very important concept for microscope observation. If you choose a suitable field of view, it will play a very important role in observation. Sometimes when purchasing the microscope objective lens, because the field of view is not selected correctly, it will bring great trouble to the observer, or even can't see the sample at all, Or the effect is very bad. The following is a brief introduction to the two fields of view used by the objective lens, namely bright field and dark field:

1. Bright field (BF): refers to the brightness difference (light and dark difference) generated by the difference of light absorption between the background and details to see the details.The illumination light irradiates the sample vertically through the objective lens. After the sample absorbs the light, it is vertically reflected and transmitted to the eyepiece or camera through the optical path. The obtained image is the bright field image.

2. Dark field (DF): use the dark field aperture to let only the light scattered by details pass through the microscope, but not the direct light shining on the background into the microscope, so as to form an image of bright details and dark background, so that people can see the bright details under the dark back, just like looking at the stars in the sky at night. The incident light that passes through the camera or the oblique angle of the eyepiece is absorbed by the illumination of the sample, and the reflected light is absorbed by the oblique angle of the camera.

When we study details at a high level, we can use the way of dark field. The most commonly used field of view of objective lens is bright field and dark field mode. In addition to the bright and dark fields, there are also the field of view modes of polarized light and differential interference.

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