Assisted Autofocus Z-Scan Adaptation for Rapid Best-Focal-Plane Detection

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Solution Overview

Problem

Existing autofocus methods struggle with efficiency and accuracy in finding the best focal plane when the working distance varies significantly, particularly in medical imaging systems, due to the need for extensive scanning and potential errors in focal plane tracking.

Innovation Solution

An assisted autofocus method that utilizes external site information to estimate the working distance and adapt the z-scan range, allowing for precise and rapid identification of the best focal plane by optimizing the scan location and parameters based on the estimated value.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the working distance varies within a large range, then the imaging system can accommodate different surgical positions, but the autofocus requires much too much time to find the best focal plane

Engineering Contradiction:

Improveworking distance rangeVSAvoidautofocus time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by using a rough autofocus determination based on contrast measurement to pre-identify the approximate location of the best focal plane before performing the precise autofocus determination. This preliminary step narrows down the search range, allowing the system to quickly adapt to large working distance variations without requiring a complete time-consuming scan of the entire range.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The autofocus process is segmented into two distinct stages: a rough autofocus determination that quickly identifies the approximate focal plane location using contrast measurement, and a precise autofocus determination that performs fine-tuned scanning in the identified region. This segmentation allows the system to handle large working distance variations efficiently by dividing the search space into a broad preliminary search and a focused precise search.

Inventive Principle:

Principle #1Segmentation

2Measurement precision

If a z-scan traverses the entire working range to find the best focal plane, then accurate focusing is achieved, but the frame rate of the image sensor limits the speed

Engineering Contradiction:

Improvefocal plane accuracyVSAvoidz-scan speed

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The rough autofocus determination serves as a preliminary action that identifies the approximate location of the best focal plane before the precise z-scan is performed. This preliminary step provides the controller with information about where to center and how to configure the precise scanning range, thereby reducing the number of focal planes that need to be scanned while maintaining accurate focusing.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

Instead of scanning the entire working range, the patent performs a partial scan focused on a reduced range around the approximately determined best focal plane location. This partial action is sufficient to achieve precise focusing because the preliminary rough determination has already narrowed down the search space to the relevant region.

Inventive Principle:

Principle #16Partial or excessive action

3Speed

If tracking the focal plane is used to quickly adjust focus after a z-scan, then speed is increased, but errors accumulate between the current focal plane and the actual best focal plane

Engineering Contradiction:

Improvefocus adjustment speedVSAvoidfocal plane accuracy

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The patent implements feedback by continuously performing rough autofocus determinations based on contrast measurement to monitor the actual best focal plane location. This feedback mechanism detects deviations between the tracked focal plane and the actual best focal plane, allowing the system to initiate new rough autofocus determinations and subsequent precise z-scans when necessary to correct accumulated errors.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system maintains continuity of useful action by continuously performing rough autofocus determinations and using the resulting information to guide precise autofocus determinations. This continuous process ensures that the focal plane tracking remains accurate over time, preventing error accumulation while maintaining fast focus adjustment capability.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS20250231391A1Assisted autofocus method and associated optical imaging system

Publication Date: 2025.07.17 SCHOLLY FIBEROPTIC GMBH

AI summary

To improve the accuracy and the speed of an autofocus method by which it is possible to automatically find a current best focal plane (13) which provides the best possible image quality for an object (3) situated at a certain working distance (11) from an optical imaging system (1), a spatial location and preferably at least one further parameter of a z-scan (17) performed to find the best focal plane (13) is modified on the basis of an estimated value (41) for the working distance (11). In this case, the estimated value (41) can be determined on the basis of site information retrieved from an external system, for example an image-based navigation system (36) or a robotics system (34) used to displace the imaging system (1). The assisted adaptation of the autofocus thus allows shortening the time required to find the best focal plane (13).