It’s long been thought that the human eye cannot see “invisible” aka infrared light. This invisible light emanates from radio waves, those beams that come television remote to your television and x-rays. Recently, though a team of researchers from the Washington University School of Medicine, St. Louis discovered that in some instances, the human eye can sense infrared light.
Experiments on the retinas of both humans and rodents, researchers found that powerful lasers emit pulses of infrared light and when these lasers pulsed in rapid succession, the light-sensing cells in the retina could detect the infrared light. If that occurs, the human eye can detect that light that has fallen outside of the visible spectrum.
The benefit of this knowledge is that doctors can use it to access parts of the retina to assure it’s working properly. One of the researchers was quoted as saying, “…this discovery will have some very practical applications.”
Researchers, once they realized that some light that was thought to be invisible to the human eye, worked to determine which type of light could be senses and which type of lasers and pulses created the recognition. It was reported that, “… laser pulses of different durations delivered the same total number of photons,” they found that, “the shorter the pulse, the more likely it was a person could see it.” Although the people couldn’t “see” the light, they could “sense” the light from the laser pulses.
The way we see light, typically, is that a photon (particle of light) is absorbed by the retina then a photopigment molecule is created. This jumpstarts the process of converting light into vision. The visible spectrum includes waves of light that are between 400 and 720 nanometers long. However, as researchers discovered, if “the retina is hit by a pair of photos that are 1,000 nanometers long, they deliver the same amount of energy as a single pulse from a 500 nanometer photon – all well within the visible spectrum.”
These researchers were the first to uncover that the human eye can sense light on this formerly invisible spectrum. Researchers are now working to find ways to use the two-photon approach to develop a new ophthalmoscope to allow eye doctors to examine the inside of patient’s eyes. It’s believed that if doctors can send a pulse of infrared laser into the eye they could stimulate areas of the retina to learn more about the structure and function of a healthy eye. This could lead to treatment of retinal diseases including macular degeneration.
UKA Optics is a manufacturer of custom lenses for use in many industries. Lenses include those for diode laser collimators, CD and DVD players, laser pointers, laser levels, laser surface inspection systems and positioning and measuring equipment. Standard and custom laser lens assemblies are available as well.