I've been trying to optimise the focus of the Milestag IR beam today. At first I thought the best way would be to observe the beam, and try to get the brightest dot at the furthest distance.
To achieve this I created this unholy device:
This is a super sensitive IR camera with a battery powered CCTV alignment monitor + the Milestag IR focusing section of my gun with faux reload and trigger switches.
My idea was to see how far I could get the beam to be a minimum diameter.
It worked very well, except that at the distances I want I could hardly detect the IR light on the small monitor.
Also I looked a bit of a cock as I walked about my street in darkness with this thing.
So I sat back and thought 'what am I trying to achieve?'. Answer: IR reception at maximum distance so I came up with this:
It's the TSOP4856 detector the Milestag system uses connected via a transistor to a LED. When it detects a 57kHz IR signal the LED illuminates. With the aid of a helper I should be able to optimise the IR focus. The further away the LED lights, the better the focus.
Here is the test circuit built up: