Machine Vision Lenses Technical Terms

Image Sizes Angle of View Depth of Field Focal Length Brightness of a Lens (F No.)Field of View and Focal Length Distortion MTF (Modulation Transfer Function)

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 symbol	Image sensor	Image size (mm)
Product symbol	Image sensor	Horizontal :H	Vertical :V	Diagonal :D
C	1”	12.8	9.6	16.0
H	2/3”	8.8	6.6	11.0
D	1/2”	6.4	4.8	8.0
35mm camera lens (Reference)	35mm Film	36.0	24.0	43.3

Angle of View

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 sensor	Permissible 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

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.

(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.