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Lens selection from several aspects, sensor selection, accuracy, baseline length, field size
1. Lens Selection
The main parameters of the lens 1.1
. A focal length (focal lenth):
Refers to the focal length of the lens from the center to the map image may be in a clear distance from the image plane.
The focal length determines the size of the size of the viewing angle, the focal length of a small value, a large viewing angle, the observed range is large; large focal length value, a small viewing angle, a small viewing range. According to the focus adjustment can be divided into fixed focus lens and a zoom lens into two categories.
. B iris (Iris):
An F to F ratio of the lens focal length and clear aperture D is measured. F are marked with a maximum value on every shot. We usually aperture value F2.8, F8, F16 and so is the aperture "factor" is a relative aperture, is not the physical aperture stop, the aperture of the iris and lens of the physical sensing device (CCD or film or CMOS), the distance related. Numerical aperture (F) 1 1.4 2 2.8 4 5.6 8 11 16 22 32
c. Support maximum dimension CCD (SensorSize)
The imaging lens may cover the maximum diameter of the CCD chip size. They are: 1/2 ", 2/3", 1 "and 1" or more.
d. Interface
Commonly used include C, CS, F, V, T2, Leica, M42x1, M75x0.75 like.
e. depth
Field is the focus on the subject in the clear, front object within a certain distance, it is still clear image range.
Depth of field with the aperture value of the lens focal length, shooting distance varies.
The larger the aperture, the smaller the depth of field; the smaller the aperture, the greater the depth of field.
The longer the focal length, the smaller the depth of field; the shorter the focal length, the greater the depth of field.
, The smaller the depth of field closer subject distance; when farther away from the subject, the greater the depth of field.
f. Resolution (Resolution)
Representative ability resolution camera to record the details of the object, which can be resolved per millimeter of black and white lines is the number of units of measurement: "/ mm" (lp / mm). The higher the resolution the sharper the image forming lens.
g. working distance (Workingdistance, WD)
A first lens face of the distance to the object.
h. field of view (Field ofView, FOV)
The camera photographed the actual size of the area.
1.2 Calculation Method
Using field of view FOV and select an appropriate working distance of the focal length f
Accuracy is calculated using the FOV field size and the pixel size of the sensor:
Accuracy (m) = FOV (V or H) ÷ pixel size (V or H)
The camera can be selected according to the pixel accuracy
