beam, and reflects blue. The blue laser comes in from the
side, and now the three beams are combined.
The laser beams can be seen by the use of smoke in
Figure 2. The third beam is just red, since red is somewhat
dominated by the blue and green, and I thought some red
should stand alone in one beam.
The three beams (two multicolored and one red) are
shone through three disks of stained glass, which are
slowly rotating and distort the beams into wonderful light
patterns. I chose uncolored textured glass for its clarity
and pattern, but you could experiment with other colors
and patterns. The wave-like pattern on the glass that I used
makes the refraction look a little like the waves of sunlight
on the bottom of a clear ocean floor.
The video is filmed from a 4-1/2 ft distance to a wall
6-1/2 ft wide, from the left side of the screen to the
corner of the room toward the right. Doubling the
distance also doubles these dimensions and gives four
times the area.
Figure 3 shows the
frequency bands with the
laser colors and the range
of some instruments. I
found the seventh band
to be so noisy that I
couldn’t tell the music
from the noise, and well
above what most
producing in pitch, so I left it out. I measured the
frequencies with the components I selected, which are
slightly different than the datasheet. Three combined
colors appear projected on the left (which I numbered
“1”); three more combined colors appear projected on
the right (#2); and the solo red laser is in the middle (#3).
The physical arrangement is shown in Figures 4 and 5.
The lowest band has the bass, the bass drum, and
other lowest notes. This is where much of the rhythm
resides, so some blue on the left and some red on the
right allows the whole projected display to pulse with the
beat. The solo red laser covers some midrange tones. The
highest range that I am using ( 5. 9 kHz) holds the treble
notes, some percussion, and overtones of the other
instruments. Since this includes much of the snare and
42 May/June 2018
■ FIGURE 4.View from above.
■ FIGURE 2. The paths of the laser beams. Smoke
makes them visible.
■ FIGURE 3. Frequency band distribution, with typical instrument's frequency ranges.