[SML] Laser projection for white stars

[Joe]

I am aware that a large percentage of "laser" products advertised on Ebay or Amazon are not lasers (neither company cares about fraudulent listings) . Though, I do think the star projector in the link I provided is a laser.  I suspect the image is actually created by putting a laser beam through a type of hologram and then duplicating it with either a prism or diffraction grating.  And color holograms that use 3 colors of laser are certainly viable to create. I don't know what the beam spread can be.
I also see the great advantage of a LED light source, in regard to eye safety.  I imagine such a device would be essentially a gobo projector.  But, I've never seen one with much of a beam spread.  Though, if such a device was cheap enough, multiples could be used.

-Joe Dunfee
 717-203-8670 Cell
 

    On Wednesday, February 15, 2023 at 07:25:24 PM EST, Matthew Breton via Stagecraft <stagecraft at theatrical.net> wrote:  
 
 A lot of these "lasers" are just LEDs without diffusing lenses, since LEDs are by nature point sources.  I think one of the comments on this particular product drives that point home.  ("NOT NOT NOT a laser product!")  A 5W LED is nowhere near as bright or dangerous as a 5W laser ... but watch out, just the same.

Matthew Breton 
Design for Theater and Dance From: Stagecraft <stagecraft-bounces at theatrical.net> on behalf of PJ Veltri via Stagecraft <stagecraft at theatrical.net>
Sent: Monday, February 13, 2023 3:23 PM
To: Stagecraft Mailing List <stagecraft at theatrical.net>
Cc: PJ Veltri <pjveltri at gmail.com>
Subject: Re: [SML] Laser projection for white stars The Sharelife one on Amazon appears to have a White LED source if you believe the reviews.
PJ
On Mon, Feb 13, 2023 at 2:35 PM *Hobbit* via Stagecraft <stagecraft at theatrical.net> wrote:

The other problem with "white" is that it's usually a mix of wavelengths,
and if the effect-generator does *anything* with diffraction you get a
spread of the wavelengths, i.e. little sets of R/G/B dots.  If this is the
"Sharelife" unit I managed to search up, the supposed "output" does have a
pattern, and it looks like it's a *de-saturated* photo of what we'd more
ordinarily expect from a typical double-diffraction projector.

    http://techno-fandom.org/~hobbit/lighting/laserspray/

One way I've seen "stars" done is with seriously fast scanning and modulation,
turning the (full) beam on for a very short line in various directions across
a set of points, making a little six or eight way "splat" around each point to
make it look more "star" like than just a dot.  Something of that capability
isn't going to come from fleabay for $200, especially if backed by software
that could make those points move around and stay in self-alignment.

And yeah, a genuine 2 or 5 watts is a lot.  So easy to have these days, where
not that long ago it took 208 3-phase, a rack of 2N3055s the size of Delaware,
and water cooling...

_H*

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