Wavefront error measurement technique using an extended incoherent light souce is investigsted. The principle of extended target correlation wavefront sensing employing an irradiance-transmittance type of mask is analysed. The Problems of simulation and selection of a target in laboratory experiments are discussed. The methods of generating the mask images from the forget structure and of preparing the experimental masks from the mask image are explored. Typical results of the mask images generated by processing the object images are given. The effects of two different mask on wavefront sensing are compared. The experimental reaults which are agreement with the theory analyses are obtained.