Foreword 



The extensive development of microscopy, whether in the field of 

 methods or instrumentation, requires from the user an ever-growing 

 knowledge regarding the phenomena on which modern techniques are 

 based. The images observed and the frequently tricky measurements 

 made by means of complex instruments must be interpreted correctly. 

 This is the reason why Chapter I is devoted to image formation in the 

 microscope. The image of a pinpoint light-source is first examined, 

 followed by an investigation of extended objects according to the type 

 of illumination used. The mathematical developments related to such 

 matters are not gone into and the object of this work will be only 

 to emphasize general principles and basic results. 



This preliminary survey serves as introduction to the chapters that 

 follow in which observation methods in visible, uUra-violet and infra-red 

 fight are set forth, together with geometrical and physical measurements 

 and fundamentals of microspectrophotometry and chemical microscopy. 



Measurements of path differences in interference microscopy and 

 their application to the determination of refractive indices and thick- 

 nesses are fully gone into. Lastly, the description of new devices will 

 be generally preceded by that of more conventional instruments in 

 order to make quite clear the underlying principles of up-to-date 

 techniques and instrumentation. 



M. Francon 



Paris 



[X 



