This book is a contribution on Confocal Scanning Laser Microscope. Misalignment of optics in this Microscope is mainly investigated. In addition, Non- Scanned Confocal Laser Microscope is proved to be equivalent to the Confocal Scanning Laser Microscope (CSLM) as explained in a complete chapter. Poly chromatic correlation is achieved using this Microscope. In addition, further improvement in the microscope resolution is attained using the aperture modulation. The book explains the different topics corresponding to the CSLM based only on the knowledge of Fourier Optics.