Multiband Filter for Macular Pigment Measurement
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Solution Overview
Problem
Current methods for measuring macular pigment, such as reflectance photography and autofluorescence, require multiple images and are prone to errors due to eye and camera movement, leading to inaccuracies and the need for complex digital processing.
Innovation Solution
A multispectral imaging technique using a multiband filter in a digital fundus camera allows for simultaneous measurement of multiple wavelengths with sharply defined bandpass regions, providing accurate topographic data from a single image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple images are taken at different wavelengths using reflectance photography or autofluorescence methods, then macular pigment measurement is achieved, but eye and camera movement cause inaccuracies and require complex digital processing
Solution Approach 1:
The patent combines multiple wavelength measurements into a single image capture by using a dichroic mirror to split the light path and direct different wavelength ranges to separate detectors simultaneously. This eliminates the need for sequential imaging and subsequent digital alignment, reducing processing complexity while maintaining measurement precision.
Solution Approach 2:
The patent performs preliminary wavelength separation using optical filters and a dichroic mirror before detection, rather than attempting to separate wavelengths after image capture. This preliminary optical sorting eliminates the need for complex post-processing to correct for eye and camera movement between sequential shots.
2Loss of information
If two different pictures are taken of the fundus at different wavelengths, then macular pigment distribution mapping is possible, but movement of the eye and camera causes shifts in field of view, magnification, and lighting
Solution Approach 1:
The patent merges simultaneous multi-wavelength detection into a single captured image frame by using a dichroic mirror to split the light path and direct different wavelengths to separate detectors at the same moment. This ensures that the field of view, magnification, and lighting conditions are identical across all wavelength measurements, eliminating registration errors from eye or camera movement.
3Measurement precision
If digital image processing software is used to correct for movement artifacts, then measurement accuracy can be improved, but the corrections take time and may introduce additional artifacts
Solution Approach 1:
The patent combines multiple wavelength measurements into a single simultaneous capture using a dichroic mirror and multiple detectors, eliminating the need for time-consuming post-capture alignment and correction algorithms. The measurement is obtained directly from the simultaneously captured image data, reducing processing time to minimal computational steps.
4Measurement precision
If specialized software is required for correction, then measurement accuracy is maintained, but the system becomes more complex and requires additional resources
Solution Approach 1:
The patent merges the wavelength separation function into the optical hardware using a dichroic mirror and multiple detectors, eliminating the need for specialized software for wavelength differentiation. The system captures multiple wavelengths simultaneously in a single image frame, requiring only basic image processing to separate the detector signals, thereby reducing software complexity and resource requirements.
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 enables precise, cost-effective, and efficient measurement of macular pigment distribution across the macula with reduced artifacts, facilitating rapid and accurate assessment of macular degeneration risk.
Implementation Method 1
a multiband filter having bandpass regions within spectral ranges of the red, green and blue detectors
Implementation Method 2
The first wavelength is blue, in the region of maximal absorbance of the macular pigment, which is around 465 nm
Data Source
AI summary
Methods and apparatus are provided for accurately imaging, assessing and measuring a patient's macular pigment. A multiband filter is employed in combination with a color digital fundus camera to provide a method that operates with a single imaging exposure. The multiband filter has bandpass regions within spectral ranges of the red, green and blue detectors of the CCD array employed within the fundus camera, the bandpass regions being sufficiently sharply defined so as to avoid regions where the CCD detector responses spectrally overlap. This provides three discrete channels of grayscale data corresponding to the bandpass regions of the multiband filter, which can be used to calculate macular pigment topographically. Methods are also disclosed for calculating the optical density of the macular pigment and advantageously displaying the resulting data.