Autofocus Control Using Pattern Image in Fluorescence Imaging
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Solution Overview
Problem
The low signal level of fluorescence captured images in photodynamic diagnosis systems leads to inappropriate evaluation values for autofocus processes, resulting in inadequate image focus and quality for observation.
Innovation Solution
A medical control device that includes circuitry to control a light source emitting excitation light and image light with a specific pattern, acquiring images, calculating autofocus evaluation values, and performing autofocus based on these values, with the circuitry ensuring the pattern image is included in the captured image for evaluation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical filter is used to cut all excitation light in the fluorescence capturing path, then the fluorescence signal can be captured without excitation light interference, but the evaluation value for autofocus becomes inappropriate due to very low signal level
Solution Approach 1:
The patent divides the optical path into two separate paths: a fluorescence capturing path with an optical filter that blocks excitation light, and an evaluation image capturing path without the filter that allows excitation light to pass through. This segmentation enables each path to serve its specific function optimally - one for accurate fluorescence capture and another for reliable autofocus evaluation.
Solution Approach 2:
The patent introduces a pattern image as an intermediary element that is superimposed on the observation target. This pattern image serves as a mediator that provides sufficient signal strength for autofocus evaluation while being distinct from both the excitation light and fluorescence signal, allowing the autofocus system to operate reliably without interfering with the fluorescence measurement.
2Reliability
If excitation light is transmitted to the fluorescence capturing device to provide sufficient signal for autofocus evaluation, then the signal level increases, but the excitation light is in the blue wavelength band that hardly contributes to brightness in the green wavelength band
Solution Approach 1:
The pattern image acts as an intermediary that converts the blue excitation light into a visible evaluation pattern. By superimposing a known pattern (such as a grid or stripes) onto the observation target, the system creates a high-contrast evaluation image that is visible in the green wavelength band, enabling reliable autofocus evaluation even though the excitation light itself is in the blue band.
Solution Approach 2:
The patent utilizes the wavelength characteristics of different light sources: the excitation light in the blue band (375-445 nm) excites protoporphyrin to emit fluorescence in the red band (600-740 nm), while a separate illumination source provides green band light (500-560 nm) for the pattern image. This color differentiation allows simultaneous capture of fluorescence and evaluation pattern without mutual interference.
3Device complexity
If the fluorescence captured image is used for autofocus calculation, then the process can be simplified, but the very low signal level prevents calculation of an appropriate evaluation value
Solution Approach 1:
The patent segments the imaging function into two distinct modes: fluorescence imaging mode using the optical filter for high-sensitivity fluorescence detection, and evaluation imaging mode without the filter for high-signal autofocus evaluation. This segmentation resolves the contradiction by allowing each mode to use the optimal signal source for its purpose without compromising the other.
Solution Approach 2:
The imaging device is designed with multi-functionality, capable of operating in both fluorescence capturing mode and evaluation image capturing mode by controlling the presence or absence of the optical filter in the light path. This universal design allows the same hardware to serve both specialized functions, maintaining simplicity while ensuring reliability.
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 approach allows for appropriate autofocus and image generation suitable for observation by using the pattern image to enhance evaluation values, even in low signal conditions.
Implementation Method 1
when the protoporphyrin is excited with excitation light (for example, blue visible light in wavelength band of 375 nm to 445 nm), the protoporphyrin emits fluorescence (for example, red fluorescence in wavelength band of 600 nm to 740 nm)
Implementation Method 2
acquire a captured image obtained by capturing an observation target irradiated with light emitted from the light source device
Data Source
AI summary
A medical control device includes circuitry configured to: control an autofocus operation on a captured image from an observation target illuminated with excitation light of a first wavelength band and a pattern image of a second wavelength band, the observation target fluorescing in response to the excitation light to output light in a third wavelength band. The captured image includes light components in the first to third wavelengths bands, of which the second and third wavelength bands are different. The autofocus operation is controlled by calculating, based on the pattern image of the second wavelength band in the captured image, an evaluation value used in an autofocus process that controls a focus position of an imaging device configured to generate the captured image.