Scanning Ophthalmoscope Shear Distortion Correction
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Solution Overview
Problem
Ultra-wide field scanning ophthalmoscopes face challenges in achieving consistent retinal image dimensions due to shear distortion caused by tilted input laser beams, affecting initial perceptions and measurement accuracy.
Innovation Solution
A scanning ophthalmoscope design featuring a source of collimated light, two scanning elements, and a scan relay device with two foci, along with a scan transfer device, which creates a two-dimensional collimated light scan from an apparent point source, eliminating the need for a tilted input beam and reducing shear distortion by aligning rotational axes orthogonally to the planes defined by the scan relay and transfer device foci.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a tilted input laser beam is used to allow transmission through the pupil, then light transmission efficiency is improved, but shear distortion is introduced in the retinal scan
Solution Approach 1:
An intermediate optical element (the scan relay device with two foci) is introduced between the scanning elements and the pupil. This intermediary device redirects the laser beam along a different optical path that is not tilted relative to the retinal surface, thereby transmitting light efficiently through the pupil while avoiding shear distortion in the retinal scan pattern.
Solution Approach 2:
The patent replaces the mechanical tilting of the input beam with an optical solution using a scan relay device. Instead of mechanically tilting the laser beam to achieve proper transmission, the system uses optical elements to redirect and relay the beam, substituting mechanical adjustment with optical path management to achieve the same transmission goal without distortion.
2Device complexity
If the rotational axes of scanning elements are aligned parallel to the scan relay device foci line, then the scan geometry is simplified, but shear distortion increases
Solution Approach 1:
The patent introduces asymmetry in the optical configuration by positioning the scan relay device with two foci at specific locations relative to the scanning elements. The rotational axes of the scanning elements are oriented at specific angles (not parallel) to the line joining the foci, creating an asymmetric arrangement that compensates for shear distortion while maintaining geometric simplicity.
Solution Approach 2:
The patent changes the angular parameters of the scanning element rotational axes relative to the scan relay device foci line. By optimizing this angular relationship, the system achieves a balance where the scan geometry remains simple but shear distortion is minimized, improving image orthogonality without significantly increasing complexity.
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 consistent retinal image dimensions and improved measurement accuracy by removing shear distortion, facilitating simpler quantification of retinal features and enhancing image orthogonality without requiring a tilt in the input laser beam.
Implementation Method 1
The scan relay device has two foci and the scan transfer device has two foci... the scan relay device and scan transfer device combine to provide a two-dimensional collimated light scan from an apparent point source
Implementation Method 2
a first scanning element; a second scanning element... The rotational axes of the first and second scanning elements are substantially orthogonal
Data Source
AI summary
The present invention provides a scanning ophthalmoscope for scanning the retina of an eye and a method of scanning the retina of an eye. The ophthalmoscope (10) comprises a source of collimated light (12), a first scanning element (14), a second scanning element (16) and a scan relay device (18) having two foci (18a, 18b). The source of collimated light (12), the first and second scanning elements (14, 16) and the scan relay device (18) combine to provide a two-dimensional collimated light scan (21) from an apparent point source (19). The scanning ophthalmoscope (10) further comprises a scan transfer device (20), wherein the scan transfer device (20) has two foci (20a, 20b) and at least one vertex (20c) and the apparent point source (19) is provided at a first focus (20a) of the scan transfer device (20) and an eye (22) is accommodated at a second focus (20b) of the scan transfer device (20), and wherein the scan transfer device (20) transfers the two-dimensional collimated light scan (21) from the apparent point source (19) into the eye (22). The two foci (18a, 18b) of the scan relay device (18) and the two foci (20a, 20b) of the scan transfer device (20) define a first plane and the two foci (20a, 20b) and the at least one vertex (20c) of the scan transfer device (20) define a second plane and wherein the first and second planes are substantially parallel.