How do I determine a camera projection matrix?

In summary, the conversation is about camera calibration in the field of computer vision. The speaker is an undergraduate student and is using the "Camera Calibration Toolbox for Matlab" to analyze images and determine intrinsic and extrinsic parameters. They are seeking guidance on how to generate the matrix that transforms pixel coordinates into real-world coordinates. There is also a question about how to get depth perception with only one eye while projecting a 3D image onto a 2D surface.
  • #1
BlueScreenOD
14
0
I'm an undergraduate computer-science student doing research in the field of computer vision, and one of the tasks I've been charged with is calibrating the camera on a robot.

I understand the basic principles at work: a vector in 3D world coordinates is transformed into homogeneous 2-space through the pinhole model, and camera calibration is supposed to find the parameters that created that transformation. However, I'm a little stumped on the actual application of these ideas.

I'm using the "Camera Calibration Toolbox for Matlab" (http://www.vision.caltech.edu/bouguetj/calib_doc/). I've successfully used the program to analyze a series of images and determined the intrinsic parameters, and I have a set of extrinsic parameters (one for each image I fed into the program); however, I can't figure out how to generate the matrix that transforms the pixel coordinates into real-world coordinates.

If someone could point me in the right direction and tell me where I can learn what I need to know, I would be greatly appreciative.
 
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  • #2
From a theoretical point of view, I don't see how it is possible. If you are projecting a 3D image onto a 2D surface, how can you tell where along the missing dimension to place the information you collect? In other words, how do you get depth perception with only one eye?
 

1. What is a camera projection matrix?

A camera projection matrix is a mathematical representation of the transformation between 3D points in the world and their corresponding 2D points on the image plane of a camera. It is used to map the points in the 3D world onto a 2D image.

2. How is a camera projection matrix calculated?

A camera projection matrix is typically calculated using a combination of intrinsic and extrinsic parameters of the camera. The intrinsic parameters include the focal length, image sensor size, and principal point, while the extrinsic parameters include the camera's position and orientation in 3D space. These parameters can be estimated using calibration techniques or obtained from the camera's specifications.

3. What is the purpose of a camera projection matrix?

The main purpose of a camera projection matrix is to accurately map 3D points in the real world onto a 2D image. This is essential for tasks such as 3D reconstruction, object tracking, and augmented reality, where the 3D information needs to be projected onto a 2D screen or image.

4. Can a camera projection matrix be used for any type of camera?

Yes, a camera projection matrix can be used for any type of camera, as long as the camera's intrinsic and extrinsic parameters are known. However, the accuracy of the matrix may vary depending on the quality of the camera and the accuracy of the parameter values.

5. How can I validate the accuracy of a camera projection matrix?

There are several methods to validate the accuracy of a camera projection matrix. One way is by using a known 3D object and comparing the projected 2D points with the actual 2D points on the image. Another method is to use a calibration target and comparing the detected features with the known values. Additionally, there are software tools available that can help with visualizing and evaluating the accuracy of a camera projection matrix.

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