Dermatoscope Focus Depth Control via 3D Shadow Reconstruction
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Solution Overview
Problem
Current dermatoscopes, both analog and digital, face challenges in accurately controlling focus depth during skin imaging, which is crucial for diagnosing skin cancers like melanoma, as existing autofocus algorithms are not suitable for structures at different depths within the skin.
Innovation Solution
The development of an inspection unit with a plurality of optical elements, including light sources arranged in rings to generate shadows, and a digital image capturing device, coupled with a processing engine for 3D shadow reconstruction, allows for precise calibration of focus depth using calibration patterns on the skin or within the device, enabling accurate association of image data with absolute focus depths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If conventional autofocus algorithms are used, then the device can automatically adjust focus, but it cannot accurately determine focus depth for structures at different depths in the skin
Solution Approach 1:
The patent introduces a calibration target with known depth markings as an intermediary object. The system first focuses on this calibration target to establish a reference relationship between focus position and depth, then applies this calibration to determine absolute focus depths during actual skin imaging. This mediator enables the system to measure focus depth accurately without requiring complex real-time depth sensing during patient examination.
2Loss of information
If multiple light sources are added for 3D reconstruction, then depth information can be obtained, but device complexity increases
Solution Approach 1:
The patent adds a temporal dimension to the imaging process by sequentially activating multiple light sources at different positions around the optical axis. Instead of adding complex spatial sensors, the system captures a series of 2D images with different illumination angles and reconstructs 3D information through computational processing. This approach obtains depth information by exploiting the time dimension of sequential imaging rather than adding parallel spatial measurement components.
3Measurement precision
If focus depth control is improved for diagnosis, then diagnostic accuracy increases, but the calibration process becomes more complex
Solution Approach 1:
The patent performs focus depth calibration in advance using a calibration target with known depth markings before actual patient examination. The system captures images of the calibration target at multiple focus positions, establishes a mapping relationship between focus control values and absolute depths, and stores this calibration data for later use. This preliminary calibration action separates the complex measurement setup from the routine diagnostic process, making the actual patient examination simpler while maintaining high precision.
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
This solution enables precise control of focus depth, improving the accuracy of skin imaging and diagnosis by linking digital driving values to absolute focus depths, thereby enhancing the detection of skin cancers and reducing the need for unnecessary biopsies.
Implementation Method 1
a first ring of a plurality light sources arranged around the optical axis and a second ring of a plurality of light sources arranged around the optical axis, the first ring of light sources projecting light substantially parallel to the optical axis and the second ring of light sources projecting light substantially perpendicular to the optical axis
Data Source
AI summary
A dermatoscope which can focus at a certain depth, e.g. below the top surface of the skin. Light sources are provided for creating shadows of a skin lesion and an image acquisition device to take images from which a 3D reconstruction can be made.