Test device for characterising materials used in optical recording

摘要

The device has a diaphragm (23) reducing size of a numerical aperture of an incident laser beam (21) lower than size of a numerical aperture of a focusing lens (22). The diaphragm is placed between a laser source (20) e.g. laser diode, and the focusing lens. An interception device i.e. detector (26), intercepts a reflected laser beam (25) after the incident laser beam passes through the focusing lens or before the incident laser beam reaches the diaphragm. The laser source directs the incident laser beam to an optical recording medium (10).