Hi Bill
Thank you once again for you very open an informative comments.
Quote Bill
You have to increase the divergence period (unless you want to use 5 milliwat lasers). This might seem controversial to some, but not to the people who really know what the hell they are doing. James, back me up here...
I can also back you up on this & I am sure James would also, but it is also important to understand the power density will be reduced with an increase in divergence. The resulting power density will also depend on the initial power, even if we do use a 1W CW laser at 10mr, 2 mm dia we are still looking at approx. 22m NOHD for a single beam exposure. Therefore even if the beam is diverged my view is that it cannot be practical to use more than a 500mW projector for audience scanning purposes unless you spend serious money to obtain a system like PASS.
I for one do not wish to have the HPA (Health Protection Agency) cross examining myself in a court if things were to go wrong, purely because I had not covered even the basics of laser safety !!.
I do agree it would be a good project for hobbyists to create a simple scan fail project, but count me out as I would not wish to be the one who put forward a circuit only to find myself in court trying to say it was not me my lord ?? they built it !!
My ideas on audience scanning involves some ideas put forward by Greg Makhov & John Tyrer, but I certainly wold not make them public without external independent evaluation.
I have also in the past, offered and even given advice free and open to members of PL and UKLM, the offer still stands if anyone is interested in a safety workshop type event at the next meeting.
I am also willing to offer a day or two at our office in Durham for up to 10 people to show how to create a safer display, and debate audience scanning FREE as this is not only in my own interest, but also to protect the industry.
Regards
Kevin