{"id":675,"date":"2018-05-20T14:43:02","date_gmt":"2018-05-20T12:43:02","guid":{"rendered":"http:\/\/valentijn.sessink.nl\/?p=675"},"modified":"2018-05-21T13:06:22","modified_gmt":"2018-05-21T11:06:22","slug":"laser-tag-optics","status":"publish","type":"post","link":"https:\/\/valentijn.sessink.nl\/?p=675","title":{"rendered":"Laser tag – optics"},"content":{"rendered":"

As noted before, laser tag actually is infrared tag. To be able to focus the infrared beam properly, you need a lens. The problem of choosing the right lens is discussed elsewhere, for example\u00a0 on the Arduino forum<\/a>, at the Milestag DIY Laser pages<\/a> and from a more theoretical viewpoint, here on a Caltech alumi page<\/a>. Problem with all these pages is: where are you going to actually buy these lenses? I found it all too hard to find a lens with a well advertised focus length; a not too large diameter (it should look like a “gun”, right? A lens with a 60mm diameter could go for a rocket launcher, but not for a proper gun). Search for “LED lens” and you will find an endless stream of all sorts of LED enclosures with light dispersing capabilities.<\/p>\n

\"flashlight<\/p>\n

Then, if you have the lenses, another problem comes up: you need to build an enclosure with your IR led at focus distance from the new lens. The milestag page above has some information about it and it is doable – but it’s a project all by itself.<\/p>\n

Luckily, there is a much easier solution. Flashlight manufacturers have long overcome the whole problem, and it is trivial to buy a focusable led flashlight.<\/p>\n

Do pay attention to the focus: you need a flashlight that will show a sharp picture of the LED chip on the wall. Seeing the image of the LED means focus distance – which, in turn, means your IR LED beam is focussed.<\/p>\n

The picture on the left shows just that: you can almost see the chip structure as a projection on the wall (it’s a bit hard to capture by camera – but trust me: I could see the wire coming out of the LED structure).<\/p>\n

Do note, that this is a regular, white light, flashlight, not an IR light. There are two ways of getting a proper IR flashlight: buy one; make one. In both cases, you are going to change the inner electronics of the light. Here is how.<\/p>\n

First, remove the lens structure:<\/p>\n