i Optik 66, No.4 (1980) 331-342 © WlssenschaftUche Verlagsgesellschaft mbH, Stuttgart Image formation in confocal scanning microscopes *) C. J. R. Sheppard **) and T. Wilson Department of Electronic and Electrical Engineering University College London and Department of Engineering Science University of Oxford Received 20 September 1979 Abstract A scanning microscope may be used in a confocal mode of operation, which results in image formation characteristics very different from those in conventional microscopy. The resolution is improved and the depth of field decreased, both of which properties are particularly useful for applications in microbiology. Image formation in conventional and scanning microscopy is compared and contrasted, with emphasis on the Fourier imaging approach. The effects of aberrations on the transfer function are discussed. Inhalt BUdentstehung in konfokaIen Rastermikroskopen. Ein Rastermikroskop kann in konfokalem Betrieb benutzt werden, die Bildentstehung dabei unterscheidet sich sehr von der Bildentstehung bei der konventionellen Mikroskopie. Die Auflosung wird verbessert und die Feldtiefe vergroBert, beide Eigenschaften sind fiir die Mikrobiologie besonders niitzlich. Die Fourier Formalismen der Bildentstehung fUr das konventionelle und das Rastermikroskop werden einander gegeniibergestellt. Diskutiert wird der EinHuB von Aberrationen auf die tJbertragungsfunktion. We begin by considering a simple explanation of confocal imaging. Figure l(a) shows the optical arrangement of a conventional microscope. A reason- ably large area of the object is illuminated by the incoherent source and condenser lens, and each point in the object is imaged by the objective into its corresponding point in the image plane. It is the second lens which is primarily responsible for the resolution, the first lens playing only a secondary *) Given at the 80 th Meeting of the DGaO/1979 European Optics Conference (EOC), 5-9 June 1979 in Bad Harzburg, Germany. **) New address: University of Oxford, Department of Engineering Science, Parks Road, Oxford. 25 Optik 55, Heft 4