Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

B Laser rangefinder

  1. Feb 26, 2016 #1
    1. Laser rangefinder is said to work by the laser reflecting from the object and the device measuring the distance.. but if the object is not reflective.. how can the laser bounce back?

    2. Is the laser in the Laser rangefinder harmful to the eyes?
     
  2. jcsd
  3. Feb 26, 2016 #2

    berkeman

    User Avatar

    Staff: Mentor

    If the object absorbs too much of the laser light, then no, you will not be able to use a laser rangefinder for the job.

    As to eye safety, that is covered in the wikipedia article: https://en.wikipedia.org/wiki/Laser_rangefinder

    :smile:
     
  4. Feb 26, 2016 #3
    how about concrete surface like in buildings.. how can it even reflect off concrete??
     
  5. Feb 26, 2016 #4

    berkeman

    User Avatar

    Staff: Mentor

    Use a window instead, or some other surface like metal that reflects well.

    Also, did you read the wikipedia article? What do they suggest when the object is not very reflective? :smile:
     
  6. Feb 26, 2016 #5
    I read it two times. It didn't suggest what to do if objective is not very reflective.. just black laser absorbing paint for military use.
    Anyway. It's not written there what if the target surface is in an angle.. then the laser would bounce off an angle too.. but for the laser to bounce back to the device.. the surface has to be exactly 90 degrees to the line of site.. how often can you find such surface in the field??
     
  7. Feb 26, 2016 #6

    berkeman

    User Avatar

    Staff: Mentor

    It said to use reflectors (like cube corner retro-reflectors). That's what surveyors use in their work with laser rangefinders. :smile:
     
  8. Feb 26, 2016 #7
    I'll use it to measure the distances of buildings.. if the laser hits the concrete from an angle.. how can it reflect back to the device? Do you think it will work? Thanks :)
     
  9. Feb 26, 2016 #8

    russ_watters

    User Avatar

    Staff: Mentor

    Laser light reflects off of concrete. If light didn't reflect off concrete, it would be black, not white!
     
  10. Feb 26, 2016 #9
    Makes sense. But if you hit it off at say 30 degrees from the sides, how can it return to the device, it should go on the other side.

    I want to use it to estimate the distances of buildings because I'm studying the effect of binocular magnification and depth of field. How come lower magnification has larger depth of fields. For example. 7X binocular has objects in focus more than 25 yards? While 8X has shallow depth of field. What physics principles makes this happen? I want to use laser rangefinder to get the distances to the target.
     
  11. Feb 26, 2016 #10

    mathman

    User Avatar
    Science Advisor
    Gold Member

    Most surfaces are not mirror like in their reflection property. For most surfaces the light is scattered in all directions and some gets back to the receiver.
     
  12. Feb 26, 2016 #11
    What happens if the building is made of glass?
     
  13. Feb 26, 2016 #12

    berkeman

    User Avatar

    Staff: Mentor

    Look, you need to go put cube corners on these buildings temporarily for your surveying of the distances for your project. Just have two people do the surveying. That is so standard.... What is so hard to understand about this?
     
  14. Feb 26, 2016 #13
    https://www.amazon.com/Nikon-8397-A...F8&qid=1456528883&sr=8-4&keywords=range+meter

    see above product.. it's supposed to be shoot and read... why.. does it only read for few selected targets only?
     
  15. Feb 26, 2016 #14

    berkeman

    User Avatar

    Staff: Mentor

    I didn't find that on a quick skim of the link but why do you think it says that?

    Are you looking to use a laser rangefinder for an application? What is your application?
     
  16. Feb 26, 2016 #15
    I have a binocular. I want to see the distance to any target...
     
  17. Feb 26, 2016 #16

    berkeman

    User Avatar

    Staff: Mentor

    There are other ways to do this.

    There are inexpensive rangefinders that use parallax to estimate the distance. Have you looked at those? Why do you need to estimate those distances?
     
  18. Feb 26, 2016 #17
    I understand to study the relationships between magnification of binocular and depth of fields.. lower magnification has greater depth of fields (meaning more objects in focus). I heard when you use 7X binocular.. everything beyond 25 yards is in focus.. but for higher magnification.. they are not in focus.. know the formula for determining magnification and depth of field? Thanks.
     
  19. Feb 26, 2016 #18

    berkeman

    User Avatar

    Staff: Mentor

    So for that you should be able to use a simple visual estimation of distance, IMO.
     
  20. Feb 27, 2016 #19

    davenn

    User Avatar
    Science Advisor
    Gold Member

    that doesn't even begin to make sense

    read this wiki link on DOF

    https://en.wikipedia.org/wiki/Depth_of_field



    Dave
     
  21. Feb 27, 2016 #20

    russ_watters

    User Avatar

    Staff: Mentor

    Which, again, is why you can see them!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Laser rangefinder
  1. Laser TEM modes (Replies: 2)

  2. Laser and Metal (Replies: 5)

  3. Class I laser (Replies: 8)

Loading...