The computer which appraises the picture which is recorded the digital camera which records the picture which is reflected the emitter (12) with, combination image formation system (16) with, the focus (18a) on at least part the reflected characteristic surface (18) with, the said surface (18) by (24) with, the camera (24) by (C) and combination image formation system (16) being high-level, optical system (10) it being in beam route, the optical element which exerts influence on the said picture according to focus position (34 and 36) with the optical system which it has (10) focus positionThe device and the method of detecting are offered.< Selective figure >Figure 2放射源(12)と、合焦結像系(16)と、焦点(18a)上の少なくとも一部が反射性の表面(18)と、該表面(18)によって反射された画像を記録するデジタル・カメラ(24)と、カメラ(24)によって記録された画像を評価するコンピュータ(C)と、合焦結像系(16)の上流で光学系(10)のビーム経路の中にあって焦点位置に応じて該画像に影響を及ぼす光学素子(34、36)とを備える光学系(10)の焦点位置を検出する装置および方法が提供される。【選択図】図2
