Credit Card Sized Flat Plastic Magnifier Fresnel Magnifying Lens, Solar Firelighter

This is one item of new fresnel magnifier available in packs of 1, 5, or 10. The material is optical PVC. The plastic is 52 X 83mm and the magnifying area is 42 X 77mm. The thickness measures about 0.47mm. The focal length is about 18cm. You can just about use this to light fires on black paper in bright sunlight but it takes a bit of patience. Of course you can use this as a pocket magnifier, or more interestingly I've used these to project tight beams from infra-red or visible LEDs for light based experimental free space voice or RF link transmission systems, using another similar lens and a photodiode at the receiver end.

In one of the pictures a spot of light is projected onto my wall some 3 metres distant from a simple 5mm bright green LED running at about 18mA. Looking at this from the far end, the single LED and lens combination is impressively bright, like a railway signal. With a keyswitch on the LED you could use it for morse-code signalling over a substantial distance like an Aldis lamp.