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Machine Vision Lenses Technical Terms

Image Sizes

There are several types of imaging sensors for FA cameras, with different image sizes.The aspect ratio of FA camera is normally 4:3 (H:V).

Product symbolImage sensorImage size (mm)
Horizontal :HVertical :VDiagonal :D
C1”12.89.616.0
H2/3”8.86.611.0
D1/2”6.44.88.0
35mm camera lens
(Reference)
35mm Film36.024.043.3
[image] Image Circle with Diagonal, Vertical, and Horizontal measurements
Angle of View
[image] Focal Length and Diagonal, Vertical, and Horizontal
Depth of Field

When focusing on a certain area in front of and behind the deep object appears in focus. This area is called the depth of field. This is because the focus appears sharp if the focus misalignment is under a certain volume. This certain volume is called the permissible circle of confusion.

The depth of field has following properties.

  • 1)The larger the F No. is, the wider the depth of field becomes.
     
  • 2)The shorter the focal length is, the wider the depth of field becomes.
     
  • 3)The longer the distance to the object is, the wider depth of field becomes.
     
  • 4)The backward depth of field is wider than the forward depth of field.
Image sensorPermissible circle of confusion
1”0.03 mm
2/3”0.021 mm
1/2”0.015 mm
1/3”0.011 mm
1/4”0.008 mm
[image] Representation of Depth of Field, Focal Depth, and Permissible Circle of Confusion
Field of View and Focal Length
[image] Representation of Field of View and Focal Length

(1) How to calculate the field of view
If the distance to the object is finite, you can use the following formula to calculate the field of view.

[image] Calculation for Field of View

(2) How to calculate focal length
If the distance to the object is finite, you can use the following formula to calculate the focal length.

[image] Calculation for Focal Length