What is Camera matrix ? How can I create this camera matrix for any image while capturing it ?

Hello Friend, I am working on a project of creating 3D model of an object from its images. I will use "Shape from silhouette' method for it. For implementation of this method I need images of that object and the camera matrix for each image I am using for it. So I need to create a camera matrix for the images I have to capture of the object. So requiring the guideline for how to create this camera matrix. Help me out with the procedure that how to create a camera matrix for image and what this camera matrix is ?

Samvit