The capacity of a microscope to maintain focus on objects located at varying distances from the lens is a critical performance parameter. It describes the thickness of the specimen that is acceptably in focus simultaneously. A greater value for this parameter allows for clearer imaging of three-dimensional structures without constant refocusing. For example, a microscope with a large value permits the visualization of the entire depth of a cell culture without adjusting the focal plane.
This characteristic significantly impacts the analysis of complex samples and the efficiency of research workflows. A substantial parameter enables more detailed observation of intricate biological specimens and reduces the time needed for image acquisition. Historically, achieving improved values has been a challenge, necessitating trade-offs with other optical qualities such as resolution and light gathering ability. Advances in optical design and technology have sought to overcome these limitations.