An innovative method of in situ real-time optical monitoring of thin film deposition and etching is presented. In this technique, intensity maps of a thin film corresponding to a series of wavelengths selected by a monochromator \left(300\text{–}800\text{\hspace{0.17em} nm}\right) are recorded by a CCD camera. From the maps the reflectance spectra at individual points of the sample surface can be extracted. By fitting the reflectance spectra to the theoretical ones, the maps of a thin film morphology (including optical parameters) and their temporal development during technological processes can be obtained. The method was tested by in situ observation of the growth of silicon nitride and silicon oxide thin films prepared by ion beam sputtering and by the monitoring of etching of thermally grown {\text{SiO}}_2 thin films.