A novel real image in-line laser holography enables a tunable image contrast by a simple pair of filters, edge sharpness and visualization of sub-wavelength structures by incorporating higher-order scattered light through large diameter lenses. Demonstrated also are the accuracy in object sizing and the ease of imaging while varying the focal depth based on a single-shot imaging via holographic principle. In addition, the use of broad, collimated laser beam for irradiation has led to a wider field of view, making it particularly useful for an extensive monitoring of, and sweeping search for, cells and microbial colonies.