ROBUST AUTOFOCUS FOR DEEP CHANNEL SCENES

Abstract

The disclosure relates to techniques for controlling a medical visualization system, in particular for supporting autofocus functionality when imaging regions of interest in and around deep canals or at "edges" in the site. The disclosure describes techniques for autofocus assistance functionality based on an automatically determined region of interest. An adaptive, confidence-based decision algorithm is used, which is optionally adapted depending on the device parameters of a microscope of the medical visualization system and the temporal change in the xy position of the region of interest in order to maximize the robustness of the autofocus while keeping the response time to a minimum. The decision algorithm exhibits a dependence on the temporal change in the xy position as well as on the defocus value.

Claims

[1] Controller (90, 899) for a medical visualization system (801) with a microscope (802), wherein the controller (90, 899) is configured to perform the following steps: - Obtaining (3005) a sequence of microscope images captured by the microscope depicting a region of interest, - determining (3020) a temporal change (701) of an xy position of the region of interest, - determining (3025) at least one z-position (401) of the region of interest, - based on the z-position (401) of the area of interest, determining (3035) a defocus value (702) of the area of interest, - determining (3040) whether an autofocus triggering criterion is met, which depends on the temporal change (701) of the xy position and on the defocus value (702), wherein the autofocus triggering criterion depends on a ratio of the temporal change (701) of the xy position to the defocus value (702), and - selectively controlling a component (802, 805) of the medical visualization system (801) for focusing based on the defocus value (702) as a function of at least the autofocus trigger criterion. [2] Control according to claim 1, where the autofocus trigger criterion depends on a confidence value in determining the area of interest, where the confidence value depends on the ratio of the temporal change (701) of the xy position to the defocus value (702). [3] Control according to claim 1 or 2, wherein the controller (90, 899) is further configured to perform the following step: - determining (3030) a temporal change (402) of the z-position of the region of interest, where the trigger criterion still depends on the temporal change of the z-position of the region of interest. [4] Control according to claim 3, wherein the trigger criterion depends on a threshold comparison between a predetermined threshold value (411) and the temporal change (402) of the z-position of the region of interest during a rolling time interval (412), wherein a length of the rolling time interval (412) depends on the ratio of the temporal change (701) of the xy position to the defocus value (702). [5] The controller of claim 4, wherein the predetermined threshold value (411) depends on at least one of a depth of field of an optical channel of the microscope or a magnification of an optical channel of the microscope. [6] Controller according to one of the preceding claims, wherein the autofocus triggering criterion further depends on at least one of a depth of field of an optical channel of the microscope (802) or a magnification of an optical channel of the microscope (802). [7] Control according to one of the preceding claims, wherein the autofocus trigger criterion further depends on a sign of the defocus value. [8] Controller according to one of the preceding claims, wherein the controller (90, 899) is further arranged to perform the following step: - Determining (3010) whether the microscope images of the sequence of microscope images show a scene (50) with a deep channel (59), wherein the autofocus trigger criterion is selectively checked when the microscope images of the sequence of microscope images show the scene (50) with the deep channel (59). [9] Controller according to one of the preceding claims, wherein determining the change (701) in the xy position comprises low-pass filtering. [10] The controller of any preceding claim, wherein the controller is further configured to determine the region of interest based on an image analysis of the plurality of microscope images. [11] Control according to one of the preceding claims, wherein the component comprises a zoom lens of the microscope, or wherein the component comprises a robotic microscope carrier of the medical visualization system. [12] A method for controlling a medical visualization system with a microscope, the method comprising: - Obtaining (3005) a sequence of microscope images captured by the microscope depicting a region of interest, - determining (3020) a temporal change (701) of an xy position of the region of interest, - determining (3025) at least one z-position (401) of the region of interest, - based on the z-position (401) of the area of interest, determining (3035) a defocus value (702) of the area of interest, - determining (3040) whether an autofocus triggering criterion is met, which depends on the temporal change (701) of the xy position and on the defocus value (702), wherein the autofocus triggering criterion depends on a ratio of the temporal change (701) of the xy position to the defocus value (702), and - selectively controlling a component (802, 805) of the medical visualization system (801) for focusing based on the defocus value (702) as a function of at least the autofocus trigger criterion. [13] A method according to claim 12, wherein the method is carried out by the controller according to any one of claims 1 to 11.

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