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TUCoPS :: Hardware Hacks :: lightshw.txt

How to set up a Laser Light Show

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*                                                                        *
*                    Make Your Own Laser Light Shows                     *
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*                       Written by: The Professor                        *
*                                                                        *
*                               07/91                                    *
* SOURCES:                                                               *
*         * The Laser Cookbook (88 Practical Projects), Gordon McComb,   *
*           Tab Books. 1988                                              *
*                                                                        *
*         * Midwest Laser Products, PO Box 2187, Bridgeview, IL 60455    *
*           (708) 460-9595  Ask for free catalog.  Great prices on       *
*           laser equipment!                                             *
*                                                                        *
*                                                                        *


     This file has been written based on my experiences with homemade laser
light shows.  I have used Helium Neon lasers to create an array of light show
     For those of you who are not aware, Helium Neon lasers come in many
sizes from 1/2 milliwatt to 40 milliwatt output power.  They produce an
INTENSE beam of light usually visible for at least a MILE!  I can see the
spot produced by my 1.4 milliwatt HeNe laser on the water tower 8 blocks from
my house!  The beam from a HeNe laser is usually red (633 nanometer
wavelength.)  They do come in other colors but are very expensive and usually
on the low power scale.  A good 1-2 milliwatt HeNe laser can be purchased
mail-order for under $100 (See Sources,just under the title.) 


     When light travels through space it is un-seen, only when it reflects
off of an object or particle can it be seen.  What does this mean?  Well, the
beam of light produced from any laser is invisible as it travels through the
air unless the laser is of considerable power, like 40 milliwatts(mW).  Why
does it take such power?  In order for the beam of light to be seen, the
photons of light must be reflected off of any of the tiny particles in the
air to reach your eye.  Only the higher power lasers emit enough light energy
(number of photons) to create a sufficient amount of reflection off of the
particles.  This fact allows us to categorize light shows into two different
types of effects: 1) Beam Effects  2) Projection Effects.


     Beam effects are cool!  Beam effects are those effects where the actual
beam of light is seen.  These are usually done by using a fog-machine.  This
permits these effects to be done with any 1/2 mW or greater laser.  Usually
the entire room where the audience sits is filled with a light fog (or
cigarette smoke) with dim or no lighting.  This creates a good medium for
beam effects! 
The Cone

     The cone effect creates a cone of light floating in the air.  This
effect can remain stationary or be scanned slowly through the air.  This
effect is most easily created by taking a small dc hobby motor and mounting a
mirror perpendicular to its shaft like so:

                    |    [               ]
                    |____[               ]
                    |    [               ]
                    |    [               ]
              mirror^      ^motor^

     How do you mount a mirror onto a motor in that fashion?  Got a penny? 
That, a small drill bit and a little glue is all it takes.  Use a drill bit
slightly smaller than the shaft of the motor and drill a hole in the center
(in the middle column of the Lincoln Memorial) of the penny.  Note, newer
pennies are softer and easier to drill.  Now fit the shaft into the hole. 
Make sure the shaft does not stick out on the other end, a snug fit is
required.  Use a drop of super glue to keep them stuck together.  Now you are
ready to mount the mirror.  Find a small, thin piece of mirror about 1/2 inch
square.  If you don't have a piece of mirror that small use a glass cutter to
cut the mirror or just break it and look for a nice piece.  The figure of 1/2
inch square is just an approximation and the mirror does not have to be
perfectly square.  Use some thick glue like silicon, RTV gasket sealant, Shoe
Goo, or whatever.  Apply it to the back of the mirror and stick the mirror
onto the penny.  Allow it to dry for awhile.  Now you are set!  
     Power the motor with a small dc power supply, batteries, train- set
power pack, whatever, and shine the laser into the mirror.  The reflected
beam will scan a perfect circle that gets larger and larger the further out
it goes.  To observe the cone effect fill the room with smoke or fog.  Set
the motor across the room and aim the laser into it so that the cone appears
right over your couch or chair. Grab a seat and enjoy!
     How does this work?  Well, when the mirror was mounted to the motor it
was mounted so that the mirror 'warbled' a little bit.  It was slightly
off-axis.  It is nearly impossible to mount it perfectly on-axis; also the
bearings (or sleeve) that holds the shaft will have play in it allowing the
mirror to 'warble'.  The more off-axis the mirror is, the faster the cone
will expand.
The Sheet or Artificial Wall/Ceiling Effect

     This effect can be created in several ways.  One way is to use a
cylindrical lens.  The lens expands the beam in only one direction.  The arc
of light is then shined through the smoke or fog.  This creates the effect of
an artificial ceiling, or sheet of light.  Move the laser or lens around to
create a moving sheet of light.  Best effects are when the sheet goes above
and below the audiences eyes, or just over the ground.
     If you do not have a cylindrical lens you can create this effect using a
dc hobby motor again.  This time the mirror must be mounted so that it
around with the shaft (reflective surface parallel with the shaft.)  This
requires that the mirror be glued to the length of the shaft.  Use strong
glue that will fill gaps (Super Glue probably would not be a good choice.) 
Now shine the laser into the mirror and notice that the beam scans a line. 
If you were to slow down the motor, you'd see that the beam is not reflected
for half the period of rotation (That is, when the beam strikes the back of
the mirror.)  When the beam hits the reflective part of the mirror it is
reflected outward in an arc.  Unfortunately this reduces the power of the
beam as it is scanned.

    Laser Beams Everywhere

     This effect creates many laser beams moving around in the air all coming
from one location.This effect is really cool!  What you do is get 3 mirrors
like the 1 foot square ones sold at all building supply stores.  Place them
next to each other like the corner of a room.  One is like the floor and the
other two mirrors are like walls.  Now place a small clear crystal ball in
the corner of the mirrors.  The crystal ball must be a multi-facet ball,
shaped like a 20 (or more) sided die.  They can be found in crystal shops and
some department stores among other places at the mall.  You may even find
something similar hanging on a chandelier or lamp at home or a friends
house.  Now, the laser is aimed into the crystal ball.  What happens?  Well,
when the laser beam goes into the crystal it gets refracted and reflected and
comes out as several beams of light.  Some of these beams will get reflected
by the mirrors back into the crystal to create even more beams of light.  The
others will shine out across the room.  They will all appear to be coming
from the crystal ball.  I like to hold the laser while shining it into the
crystal that way I can move it around a bit and make the beams change and
move around in the air.  Once again since this is a beam effect it requires a
dim, smoke or fog filled room.  The thicker the smoke or fog the better.
     Well, that's it for the beam effects.  If you have difficulty creating
the proper medium for beam effects try simply blowing smoke near the
particular 'effect generator' to get an idea of how it will look.  The effect
will look even better in the entire room.


     These effects are created by scanning the beam rapidly in random or
predetermined patterns to create images projected onto a wall or ceiling.  If
you have ever been to a laser show where they show the world rotating, or
Mickey Mouse, or some other animation these are examples of projection
effects.  Doing these effects requires some expensive scanning equipment like
galvanometers, galvo drivers, a computer, and some other hardware.  These
systems range in price from about seven thousand on up.  A guy at Midwest
Laser Products says they will have a sophisticated laser light show using an
Amiga computer (because of its audio outputs) for around $2900.
     There are several other ways to create cool projection effects.  I will
start with the simplest.

   Mirror on Speaker

     For this effect take an old speaker and glue a small mirror on the front
of the cone.  Play music through the speaker so that the mirror vibrates. 
Shine your laser into it and have it reflect the beam onto the wall or
ceiling.  You will see a bunch of random patterns pulsating to the bass of
the music.  I have found that a great way to view this effect is by placing a
mirror (at least 2 feet by 2 feet in size) against the wall of a room at a
corner of the room; not necessarily next to the floor or ceiling, just at the
edge of two walls.  Now position the reflected beam from the speaker so that
it is in the corner of the wall next to the mirror.  When music is played
into the speaker the random pattern that is created is now symmetrical on
side of the corner.  With this set-up people have claimed to see butterflies,
bats, upside-down bunny rabbits, etc.This type of effect is great with music
like Pink Floyd.  Try all sorts of music.  Music with only single notes
played create cool patterns.  Experiment!

   The Spirograph

     Remember how the cone was produced?  Well using several dc hobby motors
(2 is enough) you can create all sorts of spirograph type patterns including
a perfect 5 point star.  To make the spirograph generator make two
motor/mirror assemblies as described in The Cone at the beginning of this
text.  This time you must use two variable dc power supplies, one to power
each motor.  Mount the motors onto a piece of wood.  I used electrical
conduit holders to hold the motors in place.  Mount them so that the beam can
be aimed into one of the mirrors and reflected onto the other and then out to
a wall or ceiling.  The mirrors should be close to each other (within about
an inch.)  The arrangement may look like this:

             | /    
    mirror  _|/      laser beam out.
                laser beam in.

     Now shine the laser into the mirrors as shown above and vary the speeds
and directions of the motors.  Cool huh?!  It is possible to get a perfect
five point star!  
     I like to take this apparatus and shine the output pattern on a mirror
about 2" by 1 1/2" mounted onto a speaker.  Make it so that the whole pattern
fits on the mirror.  Now reflect this onto the ceiling or wall and turn up
some music slowly.  The patterns will distort and 'dance' to the music!
     Another fun thing to do with this is to use some optics to reduce the
size of the image so that it can be projected onto distant objects at night. 
Like on the side of a building.

   Lumia Effects
     Lumia effects are created using a piece of shower door glass (or
plastic) or the plastic covers over fluorescent lighting fixtures.  The laser
beam is shined through this material to create cloud and fibrous type
patterns on the wall.  It can also be used to distort images or as an awesome
background.  I like to move the laser slowly as it is shined through the
material this will make the clouds or fibers appear to flow.


     All laser light effects are best with music.  Play around with different
types of music to see what creates the best effect.  There are many other
ways of creating laser light effects and many variations of the effects
mentioned here, EXPERIMENT.
     Laser light spreads out as it travels.  Beam spread is usually measured
in milliradians.  A typical HeNe laser will have a beam spread of 1.5 mRad. 
As a rule of thumb this is about 1.5 millimeters spread to each meter
traveled.  Hence at 100 meters the beam will be about 150mm wide which is
just under 6 inches in diameter.  Using this formula you can calculate your
beam diameter at different distances.
     Another thing to remember is that the mirrors that you find around the
house and in the stores are rear-surface reflective mirrors.  The light is
reflected off of the rear-surface of the mirror.  The problem with these is
that the front surface of the glass will also reflect a slight portion of the
beam at a slightly offset angle.  This will create a thicker looking beam
which is usually undesirable.  To avoid this you can use front-surface
mirrors.  These mirrors are generally more costly and difficult to clean. 
     Lasers are a lot of fun at college!  I use to shine one out my dorm-room
window onto the sidewalk at night.  You should have seen the crazy way people
reacted when they saw this little red dot 'walking' down the sidewalk.  Me
and some buddies use to shine it at the girls walking home from parties(when
we weren't out) and shout to them that it was a breast enlarger.  Many of
them would go wild and damn near flash their tits, several of them came up to
my room that night!  It was great.  Lasers are great.  College is great.
     Another fun trick is to shine the laser on the ground near a cat or
dog...just watch 'em try to catch it!


The Professor.

'Knowledge is power.'

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