Timepix is a universal readout chip for pixel detectors which can be connected to various semiconductor sensors. The device has a 256×256 matrix of square pixels with a pitch of 55 μm. Every single pixel is able to measure the collected charge. The traditional material used for sensors is mono-crystalline silicon (Si). However, other materials such as gallium arsenide (GaAs) or cadmium telluride (CdTe) are applicable as well. To describe the properties of the sensors it is important to probe and evaluate the charge collection efficiency and its homogeneity across sensor area (or if possible even in its volume).