Autofocus system and method in digital holography

A computing device for use in an autofocus system for determining a focal plane for at least one object, the computing device being programmed for executing a method comprising:

• reconstructing a holographic image of the at least one object such as to provide a reconstructed image at a plurality of different focal depths,
• wherein the reconstructed image comprises a real component and an imaginary component for jointly encoding phase and amplitude information;
• performing a first edge detection on the real component for at least two depths of the plurality of different focal depths and a second edge detection on the imaginary component for the at least two depths;
• obtaining a first measure of clarity for each of the at least two depths based on a first measure of statistical dispersion with respect to the first edge detection and a second measure of clarity for each of the at least two depths based on a second measure of statistical dispersion with respect to the second edge detection;
• and
• determining the focal plane for the at least one object based on a comparison of a scalar measure of clarity for the at least two depths,
• wherein the scalar measure is based on the first measure of clarity and the second measure of clarity.

A non-transitory, computer-readable medium with instructions stored thereon, wherein the instructions are executable by a processor to perform a method for determining a focal plane for at least one object, the method comprising:

• reconstructing a image of the at least one object such as to provide a reconstructed image at a plurality of different focal depths,
• wherein the reconstructed image comprises a real component and an imaginary component for jointly encoding phase and amplitude information;
• performing a first edge detection on the real component for at least two depths of the plurality of different focal depths and a second edge detection on the imaginary component for the at least two depths;
• obtaining a first measure of clarity for each of the at least two depths based on a first measure of statistical dispersion with respect to the first edge detection and a second measure of clarity for each of the at least two depths based on a second measure of statistical dispersion with respect to the second edge detection;
• and
• determining the focal plane for the at least one object based on a comparison of a scalar measure of clarity for the at least two depths,
• wherein the scalar measure is based on the first measure of clarity and the second measure of clarity.