Spectral Fundus Imaging Using Liquid Crystal Tunable Filter
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Solution Overview
Problem
Current methods for measuring spectral fundus images face challenges in maintaining consistent light intensity and accuracy due to variations in light intensity across different wavelengths, and alignment issues between the eye and the apparatus over time, leading to displaced images and suboptimal spectral analysis.
Innovation Solution
The apparatus employs a spectral characteristic correcting filter and a liquid crystal wavelength tunable filter to maintain consistent light intensity and correct for alignment changes, using image correlation and affine transformation to automate position correction and spectral analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If spectral images are obtained using a liquid crystal wavelength tunable filter, then spectral images can be obtained relatively easily at any wavelength, but the amount of light varies greatly by wavelength with insufficient light on the short wavelength side and excessive light on the long wavelength side
Solution Approach 1:
The patent applies parameter changes by introducing a spectral characteristic correcting filter with specific transmission characteristics that vary by wavelength. This filter compensates for the non-uniform light intensity by transmitting more light at short wavelengths and less light at long wavelengths, thereby equalizing the overall light intensity across the spectral range when combined with the liquid crystal wavelength tunable filter's characteristics.
2Measurement precision
If spectral images are taken at every 10 nm in the wavelength range from 510 nm to 720 nm, then spectral images can be obtained with high wavelength analysis, but it takes about 20 seconds to complete the measurement which causes alignment displacement between images
Solution Approach 1:
The patent applies preliminary action by performing image position correction based on correlation calculation before spectral analysis. The system automatically detects displacement between spectral images and corrects positions using affine transformation, thereby eliminating the adverse effect of time-related alignment displacement that occurs during the 20-second measurement process.
3Measurement precision
If multiple spectral images are taken over time to achieve high wavelength analysis, then detailed spectral characteristics can be examined, but alignment between the eye and apparatus varies during measurement causing images to be displaced
Solution Approach 1:
The patent applies feedback by implementing an automatic image position correction system that calculates correlation between spectral images and detects positional displacement. The system then applies affine transformation to correct the positions, creating a feedback loop that continuously ensures accurate alignment throughout the multi-wavelength imaging process.
4Measurement precision
If diffraction gratings or prisms are used for light separation, then spectral measurement can be performed, but the amount of light is insufficient and the apparatus is complex
Solution Approach 1:
The patent applies mechanics substitution by replacing the mechanical light separation systems (diffraction gratings or prisms) with a liquid crystal wavelength tunable filter. This liquid crystal-based system uses electro-optic effects rather than mechanical dispersion, thereby simplifying the apparatus structure while maintaining spectral measurement capability and improving light efficiency.
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 ensures consistent light intensity across the visible spectrum, reduces alignment errors, and enables accurate, automated spectral analysis of retinal substances, improving the quality and reliability of spectral fundus image data.
Implementation Method 1
the advent of the liquid crystal wavelength tunable filter has made it possible to take spectral images at any wavelength
Implementation Method 2
a liquid crystal wavelength tunable filter capable of choosing a wavelength of a transmitted light beam in a specified wavelength range
Implementation Method 3
a spectral characteristic correcting filter having a wavelength characteristic for correcting the wavelength characteristic of emitted light intensity of the illumination light source and the transmission wavelength characteristic of the wavelength tunable filter
Implementation Method 4
an illumination light source that emits a light beam in a specified wavelength range, for illuminating a fundus of a subject eye
Implementation Method 5
a light receiving optical system for receiving the light beam reflected from the illuminated fundus and for forming a fundus image on the light receiving surface
Implementation Method 6
for forming a fundus image on the light receiving surface
Data Source
AI summary
The object of the invention is to provide a favorable spectral characteristic that reduces variation depending on the frequency of received light intensity, and that is gentle on a subject eye. It also eliminates displacement between positions of respective spectral images of the same part even if a change in alignment occurs between the eye and apparatus with the lapse of time. An apparatus 1 for measuring spectral fundus image data of this invention comprises: an illumination optical system 10 having an illumination light source 11 that emits a light beam in a specified wavelength range; a light receiving optical system 20 for forming a fundus image on the light receiving surface of a photographing section 4; a liquid crystal wavelength tunable filter 32 capable of choosing a wavelength of a transmitted light beam in a specified wavelength range; a spectral characteristic correction filter 13 having wavelength characteristic for correcting the wavelength characteristic of the emitted light intensity of the illumination light source 11 and the transmission wavelength characteristic of the wavelength tunable filter 32 so that the received light intensity on the light receiving surface is kept within the specified range; and a data measuring section 7 for taking the spectral fundus image data from the light receiving surface while changing the wavelength of the light beam passing through the wavelength tunable filter 32.