# Visual Perception: Camera Calibration

## Camera Calibration using DLT and Zhang’s Method from theoretical math explanation to MATLAB code application

We learned what Camera Calibration Matrix is in the previous post of this series. A general issue in Visual Perception is that usually, we need to calibrate our cameras before using them. That means, we need to **estimate Camera Calibration Matrix parameters** (intrinsic parameters) and **extrinsic **parameters (rotation and translation matrix of the camera)

To estimate these parameters, we will examine different methods but for each case, we will be using some **3D world points** and **their 2D projected image points**.

**DLT (Direct Linear Transform)**

DLT is a general way to create linear equations for a specific problem and put these linear equations in matrices in such a way we find the “unknowns” of the equation. For this purpose, we try to have an AX = 0 linear equation form where A includes the known data and X includes the unknown data. So the target is to find the X matrix.

Let’s start to apply DLT for our calibration problem then. We have a homogenous 3D world point, a P projection matrix, and a 2D homogenous image point: