The opportunities and special features of using a multi-purpose digital holographic camera (DHC) adapted for particle research for various diagnostic tasks, such as plankton investigation in its habitat, optical glass diagnostics, and study of defects in single crystals, are investigated. Experimental research with the DHC carried out and described in this paper has demonstrated the universality of the DHC measurement technology and its effectiveness for solving a number of diagnostic tasks in the study of small particles of different natures in various media.