System Corrects for Chromatic Aberration to Improve Imaging of Eye

By | August 2, 2019

Our eyes are an imperfect window into the world. Individual and unique aberrations of every eye make it challenging to study how people perceive the world, but also create an impediment to imaging the eye accurately for signs of disease. Since eye imaging equipment has to peer through the imperfect lenses of our eyes, the resulting images end up imperfect as well.

Most existing ophthalmology equipment already features technology to correct for monochromatic aberrations, which don’t depend on color. Chromatic aberrations, though, which change depending on the wavelength of light being used, are still not accounted for and create an impediment for many studies of the eye.

Images of the smallest cone photoreceptors in the retina, approximately 2 microns wide. Coloration was added to represent the different wavelengths of light used to capture the images after compensating for chromatic aberration.
Credit: Xiaoyun Jiang, Ramkumar Sabesan, University of Washington

Now, researchers at University of Washington have developed a system that compensates for chromatic optical aberrations of every eye and provides unprecedented imaging that will help scientists to study how we perceive colors while improving the ability of clinicians to diagnose and monitor disease. Moreover, the same technology has allowed for imaging of light-sensitive cells within the eye at different light wavelengths, which results in accurate assessments of longitudinal chromatic aberrations, a poorly studied topic.

The researchers have already integrated their technology into two existing ophthalmic instruments and tried them on human volunteers, demonstrating significant improvements in imaging quality.

Here’s a bit about the underlying technology, according to The Optical Society:

…the researchers used a device known as a Badal optometer, which consists of a pair of lenses that are a certain distance apart. Changing the distance between the two lenses changes the focus without altering the size of an image viewed through the lenses.

The researchers modified this simple Badal optometer by adding two filters that transmit longer wavelengths of light while reflecting shorter ones. These filters were kept stationary within a traditional Badal optometer, such that now, when the distance between the lenses is changed, the transmitted and reflected wavelength bands have subtly different levels of focus sufficient to compensate for the eye’s native chromatic aberration for the two wavelength bands.

By finely tuning the selection of filters, distances between the lenses and multiple color illumination, this setup can be used collectively to measure and compensate for chromatic aberration in a customized fashion.

Study in journal Optica: Measuring and compensating for ocular longitudinal chromatic aberration

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Via: The Optical Society