Small bioptic telescopes mounted on glasses to help people with visual impairments have been in existence for about 60 years and are allowed for use in driving by 39 states in the U.S. Most of them were either too heavy or too ugly to be widely used. Now, a Harvard research team has developed a new generation of telescopes embedded in glasses lens. According to one of the researchers, 'one major advantage is the appearance of the glasses. Because they look almost like normal everyday spectacles, it is more likely that visually impaired people will use them.' But read more...
You can see above how will look like the next generation of the in-the-lens telescopic device. This figure "shows a conceptual simulation of the appearance of the in-the-lens Keplerian telescope." (Credit: Schepens Eye Research Institute) Pretty discrete, isn't?
This project was led by Eli Peli, a senior scientist at the Schepens Eye Research Institute which is an affiliate of Harvard Medical School. Eli Peli worked with the members of his Vision Rehabilitation Laboratory and with Fernando Vargas-Martín from the University of Murcia, Spain.
Before going further, here is some background about bioptic telescopes. "These telescopes enable a visually impaired driver to read road signs and see other objects essential for safe driving, while also viewing the larger scene in front of the vehicle. In previous designs, the telescope is mounted through the top of the regular lens or above the frame. In both cases, the telescopic eyepiece is above the wearer's pupil, requiring the driver to tilt his/her head up and down rapidly to view alternatively the magnified and unmagnified scenes. Drivers use the telescope only for a very small fraction of the driving time, looking through the regular spectacle lens most of the time."
But as I mentioned above, many people were not using these devices because of their strange look. This is why the research team designed a wide-field telescope made of straight and curved mirrors built completely within the spectacle lens, "They started with a telescope made with mirrors and lenses to prove the image shifting principle. To embed the whole telescope inside the spectacle lens they had to obtain the magnifying power from curved mirrors instead of lenses, as mirrors maintain their power when embedded inside the spectacle lens, while the lenses lose their power when not in the air. Regular spherical mirrors can not be tilted without loss of focus, so they constructed a version made with tilted parabolic mirrors. The latter worked well and was in focus, but the images were distorted enough due to the parabolic shape to cause a disturbing effect during head movements. The latest design they constructed is based on spherical and flat mirrors with the flat mirrors implemented as tilted beam splitters that use polarization to reduce light loss."
This research work has been publised in the May/June 2008 issue of the Journal of Biomedical Optics under the title "In-the-spectacle-lens telescopic device" (Volume 13,Issue 3, Article 034027, June 24, 2008). Here are two links to the abstract and to the full paper (PDF format, 11 pages, 789 KB). The above picture was picked from this document.
Here is a quote from the introduction describing the work done by the team. "We designed a wide-field Keplerian telescope that is built completely within the spectacle lens. The design uses embedded mirrors inside the carrier lens for optical pathway folding, and conventional lenses or curved mirrors for magnification power. The short height of the ocular, its position, and a small tilt of the ocular mirror enable the wearer to simultaneously view the magnified field above the unmagnified view of the uninterrupted horizontal field. These features improve the cosmetics and utility of the device. The in-the-lens design allows the telescope to be mass produced as a commodity ophthalmic lens blank that can be surfaced to include the wearer's spectacle prescription."
For more information, Peli also developed techniques ho help people with low vision to better see and enjoy television. Here is a link to two documents issued by the Schepens Eye Research Institute on January 15, 2008, here and there. Here is a short quote. "'We knew it was time to address the changing technology,' says Peli, who pointed out that digital television will replace traditional television technology over the next few years due to government mandate."
Sources: Schepens Eye Research Institute press release, July 24, 2008; and various websites
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