Re: fun things to try / laser pen questions

[P3D John W Roberts <roberts@xxxxxxxxxxxxxxxxx>]

>Date: Thu, 14 Nov 1996 18:16:10 -0600
>From: P3D Larry Berlin  <lberlin@xxxxxxxxx>
>Subject: Re:  fun things to try / laser pen questions

>>From: P3D John W Roberts writes:
>>I've taken 3D photos at night, with the camera shutters open and a
>>(helium-neon) laser used to "scan" over a still scene in various patterns.

>******************  Wow, great idea. It's amazing how easy some of the
>alternatives to complete computer reconstruction are which exist in stereo
>photography. I like this one a lot! Such stereo laser traced photo-meshes
>would provide easy accurate means of assigning coordinate points in the
>software that converts stereo photos to 3D models. Although to be fair, it
>may be just as easy to project any slide image with a strong contrasting
>texture or grid onto an object which is then photo'd in 3D. Any strong
>texturing would make coordinating depth points easy.
I once saw an article describing a method in which a "speckled" pattern was
projected onto a scene to help in the creation of a 3D model using computer
analysis.

One incentive to get a laser pen is that I would like to experiment
with the use of mechanical aids to produce a regular scan pattern, and this
would be much easier with a laser pen because of the light weight, small size,
and lack of a power cord. Another idea is to put a rotating slotted wheel
in front of the laser to produce a controlled "dotted line". Of course
scanning can be performed with a large fixed laser using rotating polygonal
mirrors, etc.

>****************  What's the price range of the 635 nm pointers you've found?

The 635nm pointers seem to be available from multiple sources for around
$90-100.

Other options:
 - the bare laser diodes (or diode plus collimating lens), from electronic
     parts suppliers.
 - laser sights intended for firearms - bright but more expensive. I'm not
     sure how they connect the battery. (Caution: when using a laser sight
     to scan a human subject for a 3D photograph, remove it from the firearm
     first!!! :-)
 - green laser pointer (!) - I came across an ad for a 1mW, 532nm laser pointer
     (frequency doubled) - a bargain at only $859! (I think I'll wait a while
     on getting one of those.)

By the way, thanks to all those who replied on my laser pointer question.
I forgot to include one parameter, which may favor the 635nm model:
visibility to cats. ;-)

John R


------------------------------