Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers

LPF Donation via Stripe | LPF Donation - Other Methods

Links below open in new window

ArcticMyst Security by Avery

Time tunnel problems...

Joined
Feb 28, 2008
Messages
573
Points
0
I'm trying to make a time tunnel, but I have been having a few problems.  Basically what I have is a motor assembly that I have attached a mirror to, but I'm unsure what angle the mirror needs to be at to get the effect.  

I know the mirror needs to be tilted a little (from horizontal), and I've tried a couple of angles, maybe a 30 degree tilt, and then about half of that.  The first time I got more or less of a liquid sky effect with a little curvature - not what I want, of course.  The second time, I did get a narrower shape but not a circle - what I'm getting is a tear-drop shape instead of a round tunnel... :-?  I get a shape like this when I hit the spinning mirror with a laser (excuse the sloppy photoshopping -it's a thin line of course and not a solid shape):

d4a.jpg


I don't want a tear-drop shaped tunnel; I want a perfectly round one.

This is how my mirror is set now (as seen from the side view, the mirror being represented by the top line):
5ea.jpg


What am I doing wrong and why am I not getting a perfect circle?
 





Joined
Sep 8, 2008
Messages
182
Points
0
Schrecken_Licht,

I couldn't view your pics. But I can tell you that-

1. You want the mirror to 'wobble' just a little bit. You need only a few degrees off of perpendicular to the axis of spin of the motor.

2. For the time tunnel to be round(ish) you'll want to keep the plane of the mirror roughly 45 degrees to the path of the beam. Also, you'll need to remember the beam becomes oval when the surface you are projecting onto is not roughly perpendicular to the path of the beam.

Get your pictures fixed and it'll be easier to help you... ;)

cheers,
kernel
panic
 

Attachments

  • wobble.JPG
    wobble.JPG
    6.4 KB · Views: 176
Joined
Sep 12, 2007
Messages
9,399
Points
113
The degree of divergence will be double what the degree of the mirror is with respect to the motor. Any more than 10 degrees is too much, as you'll make more of a disk of light rather than a tunnel.

The shape is possibly caused by excessive motor rattling. If you already have the motor secured, the mirror is likely not secured.
 
Joined
Jul 24, 2008
Messages
1,415
Points
36
a good thing to do is just put the mirror on as flat as you can... you wont get it perfect and it will be slightly angled... more than enough for a tunnel. then shine away
 
Joined
Feb 28, 2008
Messages
573
Points
0
Ah-HA! Finally got it working! :) I got a good angle this time - very slight, even though my tunnel is a bit more of a funnel....but that's good for what I'm trying to do.  At least I now know how to adjust the mirror to change the width of the tunnel.  And it's perfectly round....

So, that lady down the street thinks she's got the coolest display going for Halloween night - not any more!  I'll have to post pics of my set-up when I get it all finished.  Thanks everyone for your help. :)

db4.jpg

c96.jpg
 




Top