What is the size of the target ?
What is the range of laser to target ? If not fixed may need a collimated beam.

 

What is the size of the target ?
What is the range of laser to target ? If not fixed may need a collimated beam.

@mike_canada
For a diffuser, consider sanding a piece of plastic film cut from a food container or product packaging. A grocer could likely give or sell you a container of suitable size. I cut out and save the nice flat areas of some containers for odd and end use such as this.

 

Ok 2 say I should do sanding. So my local plastics shop offers polycarbonate and acryllic plastic but they say the latter breaks easier but I don't know which is better. And what grade sandpaper is best? I'm going to be making multiple pieces of these. And the sensors are 2 inches apart at most and I have 12 sensors on the board almost evenly spaced out but the worst case distance between any 2 sensors is 2.5 inches.

 

Also, has anyone tried lens from digikey? would they improve my phototransistors as well or would they defeat the purpose I'm trying to achieve?

https://www.digikey.ca/products/en/...umnSort=0&page=1&stock=1&nstock=1&pageSize=25

 

Also, has anyone tried lens from digikey? would they improve my phototransistors as well or would they defeat the purpose I'm trying to achieve?

https://www.digikey.ca/products/en/...umnSort=0&page=1&stock=1&nstock=1&pageSize=25

If the laser beam does not hit the dome, then no, the dome will not help you. You need to diffuse the light far enough in advance of the sensor that the cone of diffused light will hit a sensor despite the beam missing the sensor itself.

 

In my limited experience polycarbonate material seems much more brittle and less durable than acrylic.

One other thing, it would be a good idea to make only one with your chosen material and try it out before committing to many of a particular design. large or medium grit sandpaper should do it. I wanted to hedge my bet I would try coarse grit first because if it does not work well you can always go over it with medium grit as a second try. You can't go the other way, from small to large.

 

Ok 2 say I should do sanding. So my local plastics shop offers polycarbonate and acryllic plastic but they say the latter breaks easier but I don't know which is better. And what grade sandpaper is best? I'm going to be making multiple pieces of these. And the sensors are 2 inches apart at most and I have 12 sensors on the board almost evenly spaced out but the worst case distance between any 2 sensors is 2.5 inches.

Acrylic is usually preferred for light guides (https://vcclite.com/how-to-select-the-right-material-for-led-light-pipe-applications/ ). Also, should abrasion not allow enough light to scatter, one can buy acrylic sheets that are fluorescent. I have not checked on the light absorption properties of those sheets.

 

In my limited experience polycarbonate material seems much more brittle and less durable than acrylic.

One other thing, it would be a good idea to make only one with your chosen material and try it out before committing to many of a particular design. large or medium grit sandpaper should do it. I wanted to hedge my bet I would try coarse grit first because if it does not work well you can always go over it with medium grit as a second try. You can't go the other way, from small to large.

If the material was polycarbonate it was not brittle. PolySTYRENE is indeed quite brittle. Shattering polycarbonate takes a Bridgeport mill with a fly cutter at about 1200 RPM and an excessive feed rate. Polystyrene may break if you look at it funny.

 

What about the self-adhesive matting / frosting foil used on windows?

 

I don't think the purpose is to increase reflection. It seems to me the purpose should be to get the light inside the window so it can act like a light pipe/guide. Avoiding interfaces between different materials will help.

 

I don't think the purpose is to increase reflection. It seems to me the purpose should be to get the light inside the window so it can act like a light pipe/guide. Avoiding interfaces between different materials will help.

The purpose is to make any of the two sensors spaced 2.5 inches apart recognize the lazer beam even if the lazer beam hits directly in-between the two.

Here's an example from another website: The small beam (my lazer beam) hits the diffuser plate (which lets say is my scratched up plastic) then it expands to the absorber. except in my case, the absorber is my circuit board. The light therefore expands because of the diffuser in this example. That's the kind of thing I'm trying to achieve.

 

Problem for adjusting unvisible beam placement?? For larger power NR/MIR lasers one method is to apply the paper test. The place where it is focused, the paper sheet will blow in flame. For smaller lasers are chalk test - while looking in thermal camera just pour a chalk dust hat makes the path visible. However for larger beams, especially focused, it may kill the camera. I have lost one mine after caching a glimpse even the tertiary reflection - emballage, wall, other emballage and then me. Many laserists in this manner have lost their eyesight in large extent. Last method is the same paper and look with IR camera, but a filter like welder mask is welcome.

 

An absorber has no part of the functioning. And I was considering that the intent was to detect misses that were close to the sensors, but not ON the sensors. A slightly thicker acrylic sheet, rough on the front side but smooth on the back side, should deliver the greatest amount of light to the sensors nearby. Possibly the sensor faces will also need to be rough so as to bring light arriving at an angle to the actual sensing junction. O had to do that with one brand of sensors in a laser sensing application. Both Fairchild and Honeywell sensors were more sensitive to light after a very mild sanding of the lense.

 

My lazer isn't "that" dangerous. I tested it on paper, walls, plain polycarbonate sheets and nothing burned. Heck, I even tested it on my pants while they were on me and no harm.

A slightly thicker acrylic sheet, rough on the front side but smooth on the back side, should deliver the greatest amount of light to the sensors nearby

So If I went to the plastics company and ordered such a sheet, how do I tell them to make it rough? just randomly sand it with the coarsest paper? or would special sanding patterns work better?

 

My lazer isn't "that" dangerous. I tested it on paper, walls, plain polycarbonate sheets and nothing burned. Heck, I even tested it on my pants while they were on me and no harm.



So If I went to the plastics company and ordered such a sheet, how do I tell them to make it rough? just randomly sand it with the coarsest paper? or would special sanding patterns work better?

I would suggest about "120 grit" carborundum sandpaper, (The orange stuff). And just enough sanding to not leave any untouched areas on the laser facing side. But your application may differ.

AND PLEASE BE AWARE that a laser that does notdo any burning or scorching is still strong enough to cause instant and permanent eye damage and destruction.

 

My lazer isn't "that" dangerous. I tested it on paper, walls, plain polycarbonate sheets and nothing burned. Heck, I even tested it on my pants while they were on me and no harm.



So If I went to the plastics company and ordered such a sheet, how do I tell them to make it rough? just randomly sand it with the coarsest paper? or would special sanding patterns work better?

I wouldn’t expect the plastics supply company to do the sanding. I’d do it myself. I’d place the sheet on a towel and use an orbital sander to scratch up one side. I’d then follow up with hand sanding to even out the scratches.

Do you have a plastics company nearby? I do. And most of the time I can find what I need in their scrap pile. Which I get for free or a dollar or two.

 

My lazer isn't "that" dangerous. I tested it on paper, walls, plain polycarbonate sheets and nothing burned. Heck, I even tested it on my pants while they were on me and no harm.



So If I went to the plastics company and ordered such a sheet, how do I tell them to make it rough? just randomly sand it with the coarsest paper? or would special sanding patterns work better?

These sites have useful info regarding IR transmission in plastics:
www.gsoptics.com/transmission-curves/
http://www.plasticgenius.com/2011/05/infrared-and-ultraviolet-transmission.html

 

These sites have useful info regarding IR transmission in plastics:
www.gsoptics.com/transmission-curves/
http://www.plasticgenius.com/2011/05/infrared-and-ultraviolet-transmission.html

OOPS!!! I had been considering that the laser was one in the bright red range. I have no ideas about how IR travels in plastics. Possibly the same, possibly not. Better check those reference links.

 

I tried a sample of sanded Lexan & was disappointed with result. Distance for 2.5" spread was about 8" with a non uniform field. Might do some more sanding. Tried a parabolic concentrator,
5mm exit, 13 mm entrance, 10 mm long with an acceptance angle of about 45 deg. @ US $2.00.
A cone made from Al tape, 5 X 15 X 20 mm also about 45 deg. worked. A large cone , .25" X 2" X 3.5" covered the 2" dia. at 0 deg. but only about 20 deg. acceptance angle. Light source 3mW red laser non modulated in semi dark room.

 

When my boys were young and I used to take them to Laser Tag - I learned something interesting.... It wasn't the LASER that was setting off the other players' vest, but actually IR. There once was a kid in playing who had a TV remote and was setting off everybody's vest.....