METHOD FOR AUTOFOCUSING OPTICAL RADIATION ON A DATA-PROCESSING LAYER OF INFORMATION-CARRYING MEDIUM AND DEVICE FOR CARRYING OUT SAID METHOD

The inventive method for autofocusing consists in the following: a data-processing layer (DL 3) of a carrying medium (4) is oriented along a mirror surface (MS 2) of a reflector. A primary image of an optical signal from a source (1) is formed by means of the primary entry of the optical system (EOS) and focused in a zone (MS 2) with the aid of a focusing unit (5) of said EOS. The radiation reflected from the MS 2 to the DL 3 is focused with the aid of a focusing unit (6) of the second EOS. A defocusing compensation is carried out by moving the MS 2 of the reflector along the optical axis (7) of the focusing unit (5). The movement of the MS 2 and an operational changing of the attitude position of the DL 3 are coordinated in such a way that the relative position thereof can be invariable in time. A system having a telecentric ray course and a longitudinal magnification " alpha " which is close or equal to a value 0.5/k is used as the optical system. The k is a number of reflections of the optical signal from the MS 2. The inventive device for carrying out said method comprises the reflector with the MS 2, the radiation source (1) and the telecentric optical system (TOS) which has the longitudinal magnification " alpha ". The TOS comprises a light-dividing element (9) whose one output termination is optically connected to the focusing unit (5) in such a way that it makes possible to focus the primary image of the source (1) in the MS 2 zone. The second output termination is connected to the focusing unit (6) in such a way that it enables the radiation reflected from the MS 2 to be focused to the DL 3. The reflector is provided with a device for moving the MS 2 thereof along the optical axis (7) of the focusing unit (5) thereby ensuring the relative position in time of the MS 2 and the DL 3 when the attitude position of the DL 3 is changed. Selon l'invention, le procédé de mise au point automatique consiste en ce qui suit: la couche de données (CD, 3) d'un support (4) est orientée parallèlement à une surface de miroir (SM, 2) d'un réflecteur. Au moyen d'une première composante du système optique (CSO) on forme une image primaire du signal lumineux provenant d'une source (1) et on la met au point dans la zone SM (2) au moyen d'un système de mise au pont (5) de cette CSO. Au moyen d'un système de mise au pont (6) d'une deuxième CSO, on met au point sur la CD (3) le rayonnement réfléchi depuis la SM (2). La compensation du déplacement du foyer se fait par le dé