Autofocus Control for Chromatic Aberration in Medical Observation Devices
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Solution Overview
Problem
Medical observation devices, such as endoscopes and surgical microscopes, face challenges in maintaining a clear focus during specific light observation methods like narrow-band imaging, auto fluorescence imaging, and infra red imaging due to misalignment caused by chromatic aberration in the optical system.
Innovation Solution
A medical observation device and method that control the focal position of the optical system by computing an AF evaluation value based on AF evaluation signal coefficients specific to the targeted observation band, allowing for precise focus adjustment even with optical systems having large chromatic aberration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If specific light observation is performed using an optical system with large chromatic aberration, then the observation can be conducted in different spectral bands (NBI, AFI, IRI), but misalignment occurs in the in-focus position making clear image acquisition difficult
Solution Approach 1:
The patent changes the evaluation parameters for autofocus by selecting different spectral components (R, G, B channels) based on the observation band being used. For NBI, it uses specific wavelength ranges; for AFI, it uses fluorescence bands; for IRI, it uses infrared bands. This parameter adaptation allows the optical system to achieve accurate focus in each specific light observation mode despite chromatic aberration.
Solution Approach 2:
The patent creates a universal autofocus evaluation mechanism that works across multiple observation bands (NBI, AFI, IRI) by selectively applying different spectral component weighting strategies. The same autofocus hardware and control system serve multiple functions by adapting its evaluation criteria based on the selected observation mode, eliminating the need for separate focus mechanisms for each band.
2Adaptability or versatility
If chromatic aberration is present in the optical system, then the system can transmit multiple wavelengths for different observation modes, but the in-focus position shifts depending on the wavelength band
Solution Approach 1:
The patent dynamically adjusts the autofocus evaluation parameters based on the selected observation band. By changing which spectral components are weighted in the contrast evaluation function, the system compensates for chromatic aberration-induced focus shifts without requiring physical optical realignment for each wavelength band.
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
Enables clearer subject images during specific light observations by accurately controlling the focal position in accordance with the targeted observation band, improving image clarity and focus precision.
Implementation Method 1
misalignment occurs in the position where the optical system is in focus due to chromatic aberration in the optical system
Data Source
AI summary
[Object] To control the focal position of an optical system with a more favorable aspect, in accordance with the band targeted for observation. [Solution] A medical observation device includes: a computation section that applies, to an imaging signal corresponding to each of a plurality of different spectral components based on a light receiving result regarding observation target light from a subject in vivo from an image sensor, weights of the plurality of spectral components corresponding to a band targeted for observation from among bands in the observation target light, and computes an evaluation value indicating a degree of being in-focus on a basis of the imaging signal to which the weights are applied; and a control section that controls, on a basis of the evaluation value, a position of at least one optical member in an optical system that forms an image of the observation target light from the subject onto the image sensor, and thereby controls a focal position of the optical system.