OPTICAL SCANNING DEVICE AND OPTICAL APPARATUS FOR READING AND/OR WRITING INFORMATION IN AN INFORMATION PLANE PROVIDED WITH SUCH A DEVICE

摘要

AN OPTICAL DEVICE FOR SCANNING AN INFORMATION PLANE (3) IS DESCRIBED, WHICH DEVICE COMPRISES A RADIATION SOURCE (6) FOR SUPPLYING A SCANNING BEAM (17), AND AN OBJECTIVE SYSTEM (10) FOR FOCUSING THE SCANNING BEAM TO A SCANNING SPOT (18) ON THE INFORMATION PLANE. THE TEMPERATURE DEPENDENCE OF THE OBJECTIVE SYSTEM CAN BE COMPENSATED BY A COMPENSATOR WHICH IS ARRANGED BETWEEN THE RADIATION SOURCE AND THE OBJECTIVE SYSTEM AND COMPRISES A PLANOCONVEX FIRST ELEMENT (41) AND A PLANOCONCAVE SECOND ELEMENT (42), THE CONVEX SURFACE OF THE FIRST ELEMENT CONFRONTING THE CONCAVE SURFACE OF THE SECOND ELEMENT, AND THE REFRACTIVE INDICES OF THE FIRST AND THE SECOND ELEMENT BEING EQUAL AT THE DESIGN TEMPERATURE BUT HAVING A DIFFERENT TEMPERATURE DEPENDENCE. MOST ILLUSTRATIVE DRAWING IS