282
•
Additional Reference Information
Nano Series GigE Vision Camera
Lens Modeling
Any lens surrounded by air can be modeled for camera purposes using three primary points: the
first and second principal points and the second focal point. The primary points for a lens should be
available from the lens data sheet or from the lens manufacturer. Primed quantities denote
characteristics of the image side of the lens. That is, h is the object height and h
′
is the image
height.
The focal point is the point at which the image of an infinitely distant object is brought to focus.
The effective focal length (f
′
) is the distance from the second principal point to the second focal
point. The back focal length (BFL) is the distance from the image side of the lens surface to the
second focal point. The object distance (OD) is the distance from the first principal point to the
object.
Primary Points in a Lens System
Magnification and Resolution
The magnification of a lens is the ratio of the image size to the object size:
h
h
m
'
=
Where m is the magnification, h’ is the image height (pixel
size) and h is the object height (desired object resolution
size).
By similar triangles, the magnification is alternatively given by:
OD
f
m
'
=
These equations can be combined to give their most useful form:
OD
f
h
h
'
'
=
This is the governing equation for many object and image
plane parameters.
Example:
An acquisition system has a 512 x 512 element, 10m pixel pitch area scan camera, a
lens with an effective focal length of 45mm, and requires that 100
µ
m in the object space
correspond to each pixel in the image sensor. Using the preceding equation, the object distance
must be 450mm (0.450m).
OD
mm
m
m
45
100
10
=
µ
µ
)
450
.
0
(
450
m
mm
OD
=
Summary of Contents for C1240
Page 215: ...Nano Series GigE Vision Camera Operational Reference 205 ...
Page 275: ...Nano Series GigE Vision Camera Technical Specifications 265 Models M C4090 M C5100 ...
Page 276: ...266 Technical Specifications Nano Series GigE Vision Camera Models M C700 M C1450 ...
Page 277: ...Nano Series GigE Vision Camera Technical Specifications 267 Model M C1950 ...
Page 278: ...268 Technical Specifications Nano Series GigE Vision Camera Model C4900 ...
Page 297: ...Nano Series GigE Vision Camera Additional Reference Information 287 ...
Page 299: ...Nano Series GigE Vision Camera Additional Reference Information 289 ...
