Breaking barrier of the mass production of novel materials (composite, smart, enhanced by surface layers) and introducing new technologies (laser processing, joint between nonconventional materials) pose new requirements for the industrial systems of full-field strain analysis. This quality of experimental data has to be sufficient to introduce them into numerical analysis (FEM) to perform complicated modelling of fracture mechanics, fatigue process or residual stress distribution. The experimental method, which fulfills the quality requirements, is grating interferometry. In the paper the novel type of laser full-field extensometer based on four-beam grating (moire) interferometry is presented. It is designed for medium size field of view (6 x 4.5 mm2). The extensometer is integrated and works directly on a standard loading machine with the possibility to control the load on the base of local on-line strain measurements. It enables the measurements during static, monotonic and cyclic loads and full-field analysis of arbitrary sequence of images. The extensometers give high contrast and good quality interferograms, are insensitive to vibrations and work with simple, low cost laser diode. The capabilities of the extensometers are presented on the example of low cyclic fatigue testing of steel specimens with hold and notch.