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Example 34  Modeling lens distortion

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Example 34  Modeling lens distortion

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Example 34  Modeling lens distortion

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There is a difference between the actual values ​​of view angles given in the specification of cameras(lenses) and angle values ​​obtained by calculation.

The reason for the difference is the lens distortion. Distortion can lead to a significant deviation of the view area form from a regular pyramid and warping of the spatial resolution distribution.

See more: About lens distortion

 

Accounting distortion when designing CCTV provides models of the view areas and images more close to reality, and thus more fully use cameras in the project.

 

 

Problem

 

There is a camera AXIS M1004–W/M1014/M1034-W. It is required to obtain a model of the view area, the distribution of the spatial resolution and image from this camera with taking into account lens distortion.

 

Camera parameters according to manufacturer's specification:

Sensor format - 1/4";
Lens focal length - 2,8mm;
Real horizontal view angle - 80 degrees.
Number of pixels 1280x800 (max)

 

It is recommended to measure real view angles practically.

 

Order of work

 

1. Create a camera by clicking the New camera button and place it on the layout.

2. Open the Camera geometry box and specify camera parameters:

Sensor format - 1/4";
Lens focal length - 2,8mm;
Aspect ratio: 16/10 (1280/800=16/10).

 

3. Click on the button to open the Sensor and Lens box.

In the box, pay attention to the difference between the calculated horizontal view angle - 65.5 degrees and the actual view angle from the manufacturer's specification - 80 degrees. The difference indicates that the lens distortion is present.

 

 

4. On the Lens distortion panel check the Horiz. checkbox and enter 80 to the field under it. Clear the Vert. and Diag. checkboxes, because of the vertical and horizontal view angles are unknown.

 

 

5. Turn on modeling distortion, by checking the Simulate checkbox. After that we will see significant change of view area in the Graphics window.

 

Without simulating distortion

With simulating distortion

 

6. To observe influence of the distortion on the distribution of spatial resolution you should enter the number of pixels of the camera (1280x800) in the Sensitivity and resolution and turn on modeling spatial resolution . See Visualization of cameras' control area projections and spatial resolution inside them.

 

Without simulating distortion

With simulating distortion

 

7. To observe influence of the distortion on the image from the camera, open the 3D Video and place several 3D models within camera's view area.

 

Without simulating distortion

With simulating distortion

 

8. To observe influence of the distortion on the form of the view area in 3D, open the 3D World .

 

Without simulating distortion

With simulating distortion

 

See also: Sensor and Lens>Lens distortion, About lens distortion, Measuring real view angles, Specifying active area size of the image sensor