Description of the definition of the depth of focus of the microscope

The abbreviation of depth of focus of the depth of focus, that is, when using a microscope, when the focus is on an object, not only the points on the plane of the point can be seen clearly, but also within a certain thickness of the plane. Clearly, the thickness of this clear part is the depth of focus.

Depth of focus

The depth of focus is large, and the full layer of the object to be inspected can be seen. When the depth of focus is small, only a thin layer of the object to be inspected can be seen. The depth of focus has the following relationship with other technical parameters.
1. The depth of focus is inversely proportional to the total magnification and the numerical aperture of the objective lens.
2. The depth of focus is large and the resolution is reduced.
Since the low magnification objective lens has a large depth of field, it causes difficulty in photographing at a low magnification objective lens. This will be described in detail during photomicrography.
Depth of focus: A sharper imaging distance that can be obtained by the point on the object on the imaging axis behind the lens.
Depth of focus: refers to the distance that the focus (focal plane) is allowed to move along the optical axis of the lens while keeping the image relatively clear.
Depth of focus: The distance between the retinal images of the eye that is conjugated to the depth of field (not very accurate).
Depth of focus (simply): The clear range of imaging on both sides of the image plane of the lens.
Definition: The depth of focus starts from the front of the image plane, and the cone of light that converges when reaching the image plane forms a minimum circle of dispersion. Then the divergent cone of light behind the image plane extends to the same diameter at the beginning of the depth of focus and disappears. Its depth is very high. The small is only a few percent of an inch. Therefore, the focus depth provided by the depth of focus is small.

Factors and rules affecting depth of focus

1. The aperture is inversely proportional to the depth of focus. The aperture is small and the depth of focus is large; the aperture is large and the depth of focus is small.
2. The shooting distance is inversely proportional to the depth of focus. The shooting distance is close, the depth of focus is large; the shooting distance is long, and the depth of focus is small.
Reason: The pitch (object distance) decreases, the image distance increases, and the distance between the far and near blurring circles increases, so the depth of focus increases.
3. The focal length of the lens is proportional to the depth of focus. The lens has a long focal length, a large depth of focus, a short focal length of the lens, and a small depth of focus.
Reason: When the shooting distance is fixed, the focal length increases, and the distance between the far and near blurring circles increases, so the depth of focus increases.
4. The depth of focus is proportional to the blurring circle. The allowed blurring circle is large and the depth of focus is large; the allowed blurring circle is small and the depth of focus is small.
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