Real-time autofocus focusing algorithm

A digital scanning apparatus comprising:

• an objective lens positioned for viewing a portion of a sample, wherein the objective lens defines an optical path;
• an imaging sensor comprising a plurality of imaging-sensor pixels configured to capture image data via the optical path;
• a focusing sensor comprising a plurality of focusing-sensor pixels located in different image planes and configured to capture image data via the optical path;
• and
• a processor configured to:
• receive image data from the plurality of imaging-sensor pixels of the imaging sensor,
• receive image data from the plurality of focusing-sensor pixels of the focusing sensor,
• calculate a ratio for a plurality of pairs of positions on the imaging sensor and the focusing sensor that are aligned along the optical path and sense a same field of view, and
• adjust a distance between the objective lens and the sample, during scanning of the sample, based on the calculated ratios.

A non-transitory computer-readable medium having instructions stored thereon, wherein the instructions, when executed by a processor of a digital scanning apparatus configured to scan a sample, cause the processor to:

• receive image data from a plurality of imaging-sensor pixels of an imaging sensor, the imaging sensor configured to capture image data via an optical path defined by an objective lens;
• receive image data from a plurality of focusing-sensor pixels of a focusing sensor, the focusing-sensor pixels located in different image planes, and the focusing sensor configured to capture image data via the optical path;
• calculate a ratio for a plurality of pairs of positions on the imaging sensor and the focusing sensor that are aligned along the optical path and sense a same field of view;
• and
• adjust a distance between the objective lens and the sample, during scanning of the sample, based on the calculated ratios.