SparkFun Forums

[aride4ever]

Hi all, I was hoping someone would have some experience building a precision laser target, My goal is to build a larger version of the LaserLyte Laser Training Target. The idea is to cut down the weekly cost of ammo and be able to practice indoors in a cool environment.
I thought about using a bank of small photo sensors placed into a honeycomb lattice so that only the brief laser light would trigger it.
The problem I am having is how to register each sensor so that I can display an led in the same target location.
Do you know of another sensor type that can register the exact point at which the beam hits ?
The idea would be to get the sensor to read with a tolerance of 9-12mil.
I have found commercial product but there price is way out of my range $4-5k
I appreciated any feedback.
Thanks
AR

[fll-freak]

9-12 mils? Seriously? Over what sized target? Are we taking those human form targets that are at least 1 foot square?
At 10 mils, you get one hundred steps per inch or 1,200 steps per foot. For a one foot square target that is 1,200*1,200 pixels. That's 1,440,00 pixels! The complexity in wiring up a million sensors boggles the mind.

Now if the target is just the bullseye area, then perhaps a camera sensor like in a DSLR might be possible. With the right filter in front of the lens, and the camera taking "pictures" as fast as it can, and a custom interface to the sensor, and software that does not save them image but is just looking for a bright spot, it might be possible.

[odin84gk]

fll-freak is onto something. Wiring up a large number of phototransistors may not be the best option. However, a computer-attached camera may work. Combine that with image detection software (openCV) and it could be built for $500 or less. The challenge with that is the need to capture a short burst. Either get a high-speed camera, lengthen the amount of time a burst is seen (1/30 of a second or longer), or get a material that will "hold" the light image, such as a phosphorescent material.
For example:
Europium doped Strontium Salt (SrAlO3 : Eu 2%) with some small presence of Sulfur-Aluminum Complex
http://www.youtube.com/watch?v=tXgAUCAACIA

This would hold the light long enough for the user to see where they hit, or long enough that a webcam can process the hit.

[Mee_n_Mac]

Having given this some thought years ago ... let me also agree with the above and a camera of some sort, with the appropriate lens to just cover the target in the FOV, is the way to go. Depending on what you use for a camera you can trigger it to capture only when the "shot is fired" or use a video-cam of some sort. The problem, that I couldn't find a way around, is that such a system is good for 1 shot or for revolvers and DAOs. Having to re-cock a SA autoloader is a bit of a PITA and an unnatural practice.

One advantage to using a video cam or the phosphorescent target (I like that idea !) is you could have the laser run longer than normal and get an idea of how bad your trigger control or flinch is.

http://hackaday.com/2012/06/04/bill-por ... m-exhibit/
http://hackaday.com/2012/06/01/visualiz ... -computer/

[aride4ever]

thanks, I have been working on a camera/projector system for a while but im not able to get the accuracy or flexibility out of it that im looking for. I'm getting about a 2 inch spot per shot. I'm using a older canon DLSR as the image processor and piping it out to video. I realized after posting that the shear size of the project I was hoping for ( size of a large pizza box ) would probably be out of my technical area. The reactive paper was my first thought I remember using sun paper when I was younger but couldn't find anything that would hold an image short term, I will check the youtube vid out. This whole thing came about because the neighbors are tired of hearing the blanks go off.

[fll-freak]

Have you considered building a sound proof room?

Pizza box at 2mil increments is a whole lot of pixels!

When using your DSLR, where you shooting into the lens/laser or was the DSLR looking at the target from a similar vantage point as the shooter? If the latter, was the pizza box the whole field of view? If not, a telephoto lens might be needed to get the whole camera sensor on the target.

The other issue is your laser. How small a dot is it casting. If you got a quarter sized dot on the target, getting your 2mil accuracy is not going to happen. You will need a tiny dot.

[Mee_n_Mac]

I'd question, really really hard, the need for 2 mil accuracy.

[Polux rsv]

Admitting you already have a good level, the area you need is only some cm2 , so a simple video camera will do the job. And you can record the complete sequence of breath-adjust-stop breathing-pull the trigger-re breath. This will help you discover parasitic movements during the sequence. This is probably more important than the pure precision. I saw this on TV during the standing 10m world championship. It was interesting to see how they breath and adjust the sight before pulling the trigger.

Angelo