Endoscope Phase Detection Autofocus Lens Position Selection
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Solution Overview
Problem
Endoscope apparatuses face challenges in capturing deep-focus images due to the diffraction limit, leading to frequent changes in the in-focus object plane position, which increases the burden on users during screening examinations.
Innovation Solution
An endoscope apparatus equipped with a phase difference detection element, a phase difference calculation section, a lens position selection section, and a driver section that selects between near and far point-side lens positions based on calculated phase differences to maintain an in-focus object plane position, reducing the frequency of focus changes and enhancing the depth of field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of pixels of the image sensor is increased to improve image quality, then the image resolution is improved, but the aperture becomes limited due to the diffraction limit, making it difficult to capture deep-focus images
Solution Approach 1:
The imaging section is divided into multiple imaging elements (first imaging element and second imaging element) with different focal lengths. The first imaging element has a longer focal length for capturing distant objects, while the second imaging element has a shorter focal length for capturing near objects. This segmentation allows the system to capture a wide depth of field by using different imaging elements for different depth ranges, resolving the contradiction between image resolution and depth of field.
2Measurement precision
If autofocus control is performed frequently to maintain focus on moving objects, then the observation accuracy is improved, but the in-focus object plane position changes frequently, increasing the burden on users
Solution Approach 1:
The system dynamically switches between different imaging elements based on the detected object distance. When the object is far away, the first imaging element is used; when the object is close, the second imaging element is used. This dynamic adaptation allows the system to maintain accurate focus observation without frequently changing the in-focus plane position, as each imaging element is optimized for its specific depth range, thereby reducing user burden while maintaining observation accuracy.
3Device complexity
If a single imaging element is used to simplify the structure, then the device complexity is reduced, but the depth of field is limited and cannot capture both near and far objects effectively
Solution Approach 1:
The imaging section is designed with multiple imaging elements that can be selectively activated based on the object distance. This multi-functional design allows a single imaging section to perform multiple functions: capturing distant objects using the first imaging element and capturing near objects using the second imaging element. This resolves the contradiction by achieving extended depth of field coverage without requiring completely separate imaging systems, thus balancing structure simplicity with versatility.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution allows for a stable and deep depth of field, reducing user burden by minimizing changes in the in-focus object plane position and ensuring the observation target remains in focus over a wide range, thereby improving the efficiency of screening examinations.
Implementation Method 1
a phase difference detection element for implementing phase detection autofocus
Data Source
AI summary
An endoscope apparatus includes an imaging section that includes a phase difference detection element for implementing phase detection autofocus, and acquires a captured image, a phase difference calculation section that calculates a phase difference based on a signal output from the phase difference detection element, a lens position selection section that selects a lens position that is either a near point-side lens position or a far point-side lens position based on the phase difference, the near point-side lens position and the far point-side lens position being discrete lens positions set in advance, and a driver section that changes a lens position of the imaging section to the lens position selected by the lens position selection section.