{"product_id":"credit-card-sized-flat-plastic-magnifier-fresnel-magnifying-lens-solar-firelighter","title":"Credit Card Sized Flat Plastic Magnifier Fresnel Magnifying Lens, Solar Firelighter","description":"\u003cp\u003eThis 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.\u003c\/p\u003e\n\u003cp\u003eIn 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.\u003c\/p\u003e","brand":"HJW Electronics","offers":[{"title":"1 Lens","offer_id":58759461929344,"sku":null,"price":1.9,"currency_code":"GBP","in_stock":true},{"title":"5 Lenses","offer_id":58759461962112,"sku":null,"price":4.9,"currency_code":"GBP","in_stock":true},{"title":"10 Lenses","offer_id":58759461994880,"sku":null,"price":7.9,"currency_code":"GBP","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1007\/2136\/1280\/files\/cc_top_s.jpg?v=1787504984","url":"https:\/\/shop.usefulcomponents.com\/products\/credit-card-sized-flat-plastic-magnifier-fresnel-magnifying-lens-solar-firelighter","provider":"HJW Electronics","version":"1.0","type":"link"}