# Fun Stuff to do With a Laser Pointer **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [July 24, 2010, 8:41pm UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877 "2010-07-24T20:41:14Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [July 26, 2010, 1:14pm UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877/21 "2010-07-26T13:14:59Z")
> [@RalfCoder](#): > > A backyard astronomer friend of mine used to use his to turn off the street light that lit up his yard. For people who know some astronomy, trying to show other people the night sky, laser pointers have been nearly a god send. I remember the years of “see that star…no, not that one, the other one…which one?..” ARGGHHH! Now, with a laser pointer, get somebody to stand next to you, aim that sucker in whatevers direction, and they can SEE which thing you are pointing to. ---
**Author:** ![Ale](https://avatars.discourse-cdn.com/v4/letter/a/f19dbf/32.png) [@Ale](https://boards.straightdope.com/u/Ale)\ **Post date:** [July 26, 2010, 1:54pm UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877/22 "2010-07-26T13:54:56Z")
**Sunspace** , I’d like to use it to distract the tiger, not to slice it in half and set the forest on fire. 😛 > [@RalfCoder](#): > > Road signs, license plates, and tail lights light up like magic when you can hit them. Use caution so you don’t blind oncoming traffic, of course. I once had an oncoming carload of teenagers hit me with one while driving. It was only for an instant, but still unnerving. Heh, now I picture your car having one of [these](http://thefutureofthings.com/news/1051/boeing-tests-avenger-solid-state-laser-weapon.html) on the roof. [Paul Hogan]That’s not a laser… _this_ is a laser.[/Paul Hogan] _Car full of punks goes up in a poof of smoke._ ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [July 26, 2010, 2:02pm UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877/23 "2010-07-26T14:02:05Z")
> [@](#): > > Heh, now I picture your car having one of these on the roof. > > [Paul Hogan]That’s not a laser… this is a laser.[/Paul Hogan] > > Car full of punks goes up in a poof of smoke. > Reply With Quote Yeah. No joke – I can see “laser dueling” or “laser jousting” – shining lasers at opposite cars by laser -equipped jerks – as a real possibility. You don’t need Lucas-sued high-power laser pointers to make this a potentially dangerous situation. ---
**Author:** ![dmatsch](https://avatars.discourse-cdn.com/v4/letter/d/3be4f8/32.png) [@dmatsch](https://boards.straightdope.com/u/dmatsch)\ **Post date:** [July 26, 2010, 3:27pm UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877/24 "2010-07-26T15:27:17Z")
> [@N9IWP](#): > > Green lasers are great for pointing out constellations, but since you have a red one that blows that idea. > > I don’t think diode based lasers are good for holography, but you could try > > Brian If you happen to have a green laser AND a red one, for Og’s sake don’t cross the streams. It would be bad. Giant Twinkie kind of bad that I wouldn’t have to tell you about. ---
**Author:** ![MeanOldLady](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/meanoldlady/32/10737_2.png) [@MeanOldLady](https://boards.straightdope.com/u/MeanOldLady)\ **Post date:** [July 26, 2010, 3:33pm UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877/25 "2010-07-26T15:33:52Z")
> [@needscoffee](#): > > My daughter tapes it to her BB gun. I laughed. Your daughter is hilarious. ---
**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\ **Post date:** [July 26, 2010, 3:54pm UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877/26 "2010-07-26T15:54:14Z")
> [@dmatsch](#): > > If you happen to have a green laser AND a red one, for Og’s sake don’t cross the streams. It would be bad. Giant Twinkie kind of bad that I wouldn’t have to tell you about. But add a blue one and everything’s all full-colour okay! ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [July 26, 2010, 4:43pm UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877/27 "2010-07-26T16:43:03Z")
> [@](#): > > If you happen to have a green laser AND a red one, for Og’s sake don’t cross the streams. It would be bad. Giant Twinkie kind of bad that I wouldn’t have to tell you about. I actually once built a measuring device that did precisely this. It worked beautifully. Sometimes crossing the streams is the best thing to do. As far as holography goes, 1.) There’s no reason you can’t use a diode laser, but I wouldn’t use a handheld pointer – it’d shake too much. 2.) Laser pointers aren’t well known for their coherence length, and it’s the coherence length that limits the size of your hologram. Dennis Gabor’s holograms (made over a decade before the laser was invented) had a thickness that could be measured in microns, because filtered mercury light has a short coherence length. 3.) you can get small lasers with much longer coherence lengths than laser pointers for about the same cost, I think. So pointers probably aren’t your best choice. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [July 26, 2010, 5:10pm UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877/28 "2010-07-26T17:10:17Z")
> [@CalMeacham](#): > > [ > 2.) Laser pointers aren’t well known for their coherence length, and it’s the coherence length that limits the size of your hologram. Its not as bad as you think. [http://www.holoworld.com/holo/diode.html](http://www.holoworld.com/holo/diode.html) ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [July 26, 2010, 5:23pm UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877/29 "2010-07-26T17:23:58Z")
> [@](#): > > [http://www.holoworld.com/holo/diode.html](http://www.holoworld.com/holo/diode.html) Hmm. I don’t trust his statement that “the laser pointer doesn’t have to be tied down”. Unless your exposure is a quick flash, any unsteadiness in your hand is going to “smear” out the interference fringes that are the very basis of holograms. Every setup I’ve used – and every one I’ve read about – has had source, plate, and object firmly secured. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [July 26, 2010, 5:31pm UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877/30 "2010-07-26T17:31:59Z")
> [@CalMeacham](#): > > > [@](#): > > > > [http://www.holoworld.com/holo/diode.html](http://www.holoworld.com/holo/diode.html) > > Hmm. > > I don’t trust his statement that “the laser pointer doesn’t have to be tied down”. Unless your exposure is a quick flash, any unsteadiness in your hand is going to “smear” out the interference fringes that are the very basis of holograms. Every setup I’ve used – and every one I’ve read about – has had source, plate, and object firmly secured. I’ve done what he’s done. And worse. Not handheld mind you. But you can make some nice holograms with cheap laser pointers and without 2 ton granite tables, temp controlled labs, and everthing bolted the bejezuss down. The guy has DONE this stuff and others have replicated it. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [July 26, 2010, 5:39pm UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877/31 "2010-07-26T17:39:41Z")
Missed edit window. I think you either misread (or he miswrote) that he was suggesting that you could make a hologram handholding the laser during the exposure. The more important point being a cheap laser pointer can have more than enough coherence length to make a good hologram. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [July 26, 2010, 5:45pm UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877/32 "2010-07-26T17:45:21Z")
> [@](#): > > I think you either misread No, I didn’t misread it – he said it. And I didn’t say you had to have granite tables. Heck, Unterseher has you making holograms in a sandbox. But I don’t buy that you can hand-hold the laser pointer and get good results. I’ll also accept that some laser pointers will have enough coherence length, but I doubt if they all do, and choosing one at random isn’t the best way to find one that’ll work. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [July 26, 2010, 6:01pm UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877/33 "2010-07-26T18:01:27Z")
> [@CalMeacham](#): > > > [@](#): > > > > I think you either misread > > No, I didn’t misread it – he said it. > > And I didn’t say you had to have granite tables. Heck, Unterseher has you making holograms in a sandbox. But I don’t buy that you can hand-hold the laser pointer and get good results. > > I’ll also accept that some laser pointers will have enough coherence length, but I doubt if they all do, and choosing one at random isn’t the best way to find one that’ll work. Depends on the chance of having a good one vs a bad one doesnt it?. You can buy a bunch of cheap laser pointers for the cost of one lab quality HeNe, much less a HeNe thats more than a few milliwatts. Then consider how fragile and power hungry one is vs how small, durable, and low power consumption the other is. Hey, point out where he said the hand holding thing and I’'ll see what I think he was saying. PS, the first cheap pointer we tried worked nicely. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [July 26, 2010, 6:57pm UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877/34 "2010-07-26T18:57:02Z")
> [@](#): > > Hey, point out where he said the hand holding thing and I’'ll see what I think he was saying. You don’t have to interpret – I can read him just fine: > [@](#): > > I could have mounted the laser pointer and spatial filter on a tripod and shot the reference beam down at the required angle. Remember, the ONLY part of your system that needs to have vibration isolation with single-beam holography is the object and the plate. The laser and lens/spatial filter does NOT have to be isolated or even located on the table. [http://www.holoworld.com/holo/diode7.html](http://www.holoworld.com/holo/diode7.html) ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [July 26, 2010, 7:15pm UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877/35 "2010-07-26T19:15:25Z")
> [@CalMeacham](#): > > > [@](#): > > > > Hey, point out where he said the hand holding thing and I’'ll see what I think he was saying. > > You don’t have to interpret – I can read him just fine: > > > [@](#): > > > > I could have mounted the laser pointer and spatial filter on a tripod and shot the reference beam down at the required angle. Remember, the ONLY part of your system that needs to have vibration isolation with single-beam holography is the object and the plate. The laser and lens/spatial filter does NOT have to be isolated or even located on the table. > > [http://www.holoworld.com/holo/diode7.html](http://www.holoworld.com/holo/diode7.html) That DOESNT mean its handheld does it? You said “handholding”. I sure don’t see that in there anywhere. He said on a tripod for pete’s sake. The dude has a website that details making holograms. He started it over 10 years ago. He MAKES them. He teaches classes on making them. He has plenty of actual specs on most pages. What do you think is most likely? He’s made up the whole thing? He’s just made up this one thing? He’s not quite right on one thing? Your impression of what will work and not work aint quit right? ( You do realize that people have done holography with no vibration isolation right?) You did notice it is single beam reflection holography he was talking about didnt you? Call him or email him and see if he’s actually done what he says is doable. Oh, all my references are in storage, but now that I think about it, I seem to recall that the laser actually being on the vibration isolation table wasnt required being mentioned a time or two as well. ---
**Author:** ![Floppy\_Joe](https://avatars.discourse-cdn.com/v4/letter/f/3bc359/32.png) [@Floppy\_Joe](https://boards.straightdope.com/u/Floppy_Joe)\ **Post date:** [July 26, 2010, 7:23pm UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877/36 "2010-07-26T19:23:49Z")
Back in my halcyon days, we had prepared a dark and smokey room (don’t ask). In the center of the room, hanging by a thread was on of those large, round, faceted crystals. Pointing the red pointer at the crystal, you could see the myriad beams of laser light being reflected all over the room. Pretty trippy, I tell ya what. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [July 26, 2010, 7:33pm UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877/37 "2010-07-26T19:33:59Z")
> [@](#): > > That DOESNT mean its handheld does it? You said “handholding”. I sure don’t see that in there anywhere. He said on a tripod for pete’s sake. > > The dude has a website that details making holograms. He started it over 10 years ago. He MAKES them. He teaches classes on making them. He has plenty of actual specs on most pages. > > What do you think is most likely? > > He’s made up the whole thing? > > He’s just made up this one thing? > > He’s not quite right on one thing? > > Your impression of what will work and not work aint quit right? ( You do realize that people have done holography with no vibration isolation right?) > > You did notice it is single beam reflection holography he was talking about didnt you? > > Call him or email him and see if he’s actually done what he says is doable. Jeez, calm down. I’ve made holograms.I’ve made single-beam holograms. I;'m not accusing him of making things up. He doesn’t say “handholding”, but he does say that “the only part that needs vibration isolation is the object and the plate:”, which seems not right to me, and implies that you could do it handheld, which I admit is hyperbole for "not tied down. But you’re taking this far too personally. ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [July 26, 2010, 8:02pm UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877/38 "2010-07-26T20:02:11Z")
> [@CalMeacham](#): > > I’ve made holograms.I’ve made single-beam holograms. I;'m not accusing him of making things up. He doesn’t say “handholding”, but he does say that “the only part that needs vibration isolation is the object and the plate:”, **which seems not right to me,** and implies that you could do it handheld, which I admit is hyperbole for "not tied down. You are reading stuff into it that just ISNT there. He didn’t say handheld. He didnt even apparently say not tied down. He just said NOT on the vibration isolation table. You need to think about that bolded part a bit. Yeah, I am going to get a bit peeved because you think a guy (who actually does the stuff) is wrong because you are virtually making stuff up about what he said and then imply he doesnt know what he is talking about because of stuff you made up. ---
**Author:** ![Bookkeeper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bookkeeper/32/281_2.png) [@Bookkeeper](https://boards.straightdope.com/u/Bookkeeper)\ **Post date:** [July 26, 2010, 8:43pm UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877/39 "2010-07-26T20:43:18Z")
Two of our three cats go nuts over the laser pointer (the other just looks at you and goes “Meh”). I have one I got as a freebie at a conference (combination pen, USB key, and laser pointer) that is easily visible on the side of the apartment building 3 blocks away. I can see why these are dangerous to airplane pilots at night! ---
**Author:** ![billfish678](https://avatars.discourse-cdn.com/v4/letter/b/7bcc69/32.png) [@billfish678](https://boards.straightdope.com/u/billfish678)\ **Post date:** [July 27, 2010, 1:53am UTC](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877/40 "2010-07-27T01:53:30Z")
I sent the Holoworld guru/creator Frank DeFreitas a quick email about not having the laser on the vibration isolation table. Here is part of his response: Hello Bill. Thank you for your kind words. Not only does the laser not have to be on the vibration isolation table for single beam holograms, it was a practice back in the days of DCG recording to actually TAP on the laser to reduce speckle in the final images. [Previous page](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877.md?page=1) [Next page](https://boards.straightdope.com/t/fun-stuff-to-do-with-a-laser-pointer/547877.md?page=3)