EYE PROBLEMS like cataracts and age-related macular degeneration are all too common in Australia, especially among those of "mature age". In fact, it was recently estimated that one in every four people over 75 has symptoms of this kind of visual impairment, while one in every 10 lose their central vision.

Understandably, those unlucky enough to suffer from these problems can find it very difficult to read a book, magazine or newspaper. This lowers their quality of life dramatically and deprives them of important sources of news, entertainment and information.

In many cases, however, reading printed material can be made a lot easier by using improved lighting to increase the contrast, plus a magnification system to enlarge the type. Optical magnifiers with built-in lighting are available for use as reading aids but they’re fairly pricey. You can also get similar devices using video magnification but these are even more expensive. As a result, such devices are often out of the reach of the people who could benefit from them.

The Video Reading Aid skates over the printed page on a plastic skirt (actually an upside down food container). This keeps the lens at the correct focal distance and makes the unit easy to operate.

Recently, we decided to have a go at a video magnifier ourselves and this project is the result. It combines one of the very small low-cost black and white CMOS cameras currently available from various suppliers with a very compact video processing circuit, and has a switch so you can select one of three image options: high contrast greyscale positive, hard limited or ‘digital’ black and white positive, or digital negative. And the output is standard video so it’s compatible with any normal PAL TV receiver.

The camera and video processor are both fitted inside a standard UB3-size project box. Because a person with impaired vision doesn’t want to be fiddling with camera focusing, we’ve mounted it on plastic food container to give it a fixed focal length. In use, this plastic skirt sits directly on the printed page and slides easily over the page, without marking.

Basically, it behaves a bit like a giant mouse – you just slide it so that the lens is over the text you want to read.

Illumination is provided via four high-output white LEDs, which mount on the underside of the box adjacent to the lens. In practice, the LEDs have to be "doctored" to ensure that their light output is reasonably diffused over the camera’s viewing area but this is easy to do, as described later in the article.