LEOI-30A is composed of light source, diffractive element, photoreceiving unit, computer, and software. Employing a high precision displacement transducer (grating ruler), this system can be used to accurately record the intensity distribution of single-slit, multi-slit, multi-aperture, and multi-rectangle diffraction. Data acquisition and data processing are computer-controlled to allow comparison between theoretical prediction and measurement result. LEOI-30B is a less expensive model that does not contain a grating ruler in the system.