Focus control device, endoscope apparatus, and method for controlling focus control device

An endoscope focus control device comprising:

• a processor comprising hardware, the processor being configured to implement:
• an area setting process that sets a plurality of areas to a captured image that has been captured by an imaging section, each of the plurality of areas including a plurality of pixels;
• a direction determination process that determines whether a target in-focus position lies in a NEAR direction or a FAR direction with respect to a reference position with respect to at least two of the plurality of areas set to the captured image to calculate a direction determination result with respect to each of the plurality of areas, the target in-focus position being a target of an in-focus object plane position, and the direction determination result indicating one of NEAR, FAR, and NULL;
• and
• a focus control process that preferentially brings an area among the plurality of areas that is situated away from the imaging section into focus based on the direction determination result,
• wherein the processor calculates at least one of area information about an area for which it has been determined that the target in-focus position lies in the NEAR direction, and the area information about an area for which it has been determined that the target in-focus position lies in the FAR direction, based on the direction determination result, and determines whether to perform the focus control process that moves the in-focus object plane position in the NEAR direction, or the focus control process that moves the in-focus object plane position in the FAR direction, based on whether or not the area information satisfies a given condition,
• wherein the processor implements the focus control process that calculates a feature quantity with respect to each of the plurality of areas, and sets an effective area based on the feature quantity, the effective area being an area among the plurality of areas for which a direction in which the in-focus object plane position is moved is determined, and
• wherein the processor implements the focus control process that sets an area among the plurality of areas for which it has been determined that tissue is captured, to be the effective area based on the feature quantity.

A method for controlling a focus control device, the method comprising:

• setting a plurality of areas to a captured image that has been captured by an imaging section, each of the plurality of areas including a plurality of pixels;
• performing a direction determination process that determines whether a target in-focus position lies in a NEAR direction or a FAR direction with respect to a reference position with respect to at least two of the plurality of areas set to the captured image to calculate a direction determination result with respect to each of the plurality of areas, the target in-focus position being a target of an in-focus object plane position, and the direction determination result indicating one of NEAR, FAR, and NULL;
• performing a focus control process that preferentially brings an area among the plurality of areas that is situated away from the imaging section into focus based on the direction determination result;
• and
• calculating at least one of area information about an area for which it has been determined that the target in-focus position lies in the NEAR direction, and the area information about an area for which it has been determined that the target in-focus position lies in the FAR direction, based on the direction determination result, and determining whether to perform the focus control process that moves the in-focus object plane position in the NEAR direction, or the focus control process that moves the in-focus object plane position in the FAR direction, based on whether or not the area information satisfies a given condition,
• wherein the focus control process calculates a feature quantity with respect to each of the plurality of areas, and setting a null area based on the feature quantity, the null area being an area for which a direction in which the in-focus object plane position is moved is not determined, and
• wherein the focus control process sets an area among the plurality of areas for which it has been determined that an object other than tissue is captured, to be the null area based on the feature quantity.