Note: Descriptions are shown in the official language in which they were submitted.
71548-10
l. Field of Invention
The invention rel~tes to ~usical instrumen-ts in which
light beams striking detectors produce various tones.
2. Description of the Pr;~or Art
In the past light beams have been used to produce
musical sounds. Typically, the liyht shines on a series of
photocells connected to an amplifier and speaker~ When light
strikes the cell a tone is produced or stopped. Most prior
art light beam musical instruments utilize a shutter to control
the light beam. However, Meissner in U.S. pa-tent 3,038!363
interrupts the light beam with a metal reed and Ferber in U~S.
Patent 3,733,953 uses vibrating guitar strings. Yet, ~n all
prior art light beam musical instruments interruption of the
light beam stops or creates a sound. Volume is not controlled
by the light beam.
In the present invention the loudness of soun~s pro-
duced is dependent upon the intensity of the light beam which
can be changed by interrupting the beam or reflecting the light
backwards to a detector situated next to the light source~ To
make the instrument respond to ~ariations in ligh-t intensity I
provide a special amplifier circuit which responds to both the
amoun~ of the light beam interruption as well as the rapidity of
interruption.
The presentinvention can be Yariously embodied for
use in string, woodwind and percussion instruments. In addition,
the invention can be embodied so that movement of dancers on a
s-tage will control the loudness of the musical sounds.
In accordance with a broad aspect of the invention
there is provided a light beam musical instrument comprising:
a, at least one light source, b. at least one light detector
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posi-tioned for receiving liyht from the ligh-t source and con-
verting variations therein to electric siynals, c. a signal
sensitive amplifier whlch amplifies electrical signals in
accordance with signal variations and is wired to receive elec-
trical signals frorn the detector, said signal sensitive ampli-
fier having means for transforming a signal received from said
light de-tector into a transformed signal which is related to
both the extent of interruption or reflection of a light beam
from said light source and the rapidity of such interruption or
reflection action~ d. a frequency generator, e. modulator means,
adapted to receive said transformed signal from the signal
sensitive amplifier and to receive a tone signal from said
frequency generator and f. a speaker wired to the amplitude
modulator.
Other details, objects and advantages of the invention
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will become apparent Erom the following description of the
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a block diagram of the invention.
Figure 2 is a graph showing how the signal from the
light detector is modified by the invention.
Figure 3 is a circuit dia~ram o the present preferred
circuit for the detector and light sensitive amplifier o Figure
1.
Figure 4 is a side elevational view o~ a harp to which
a present preEerred embodiment of the invention is attached.
Figure 5 is a side view partially in section of a wind
instrument employing a second preferred embodiment of the
invention.
Figure ~ is a perspective view partially in section of
a keyboard instrument employing a third preferred embodiment of
the invention.
Figure 7 is a top plan view o~ a portion of the
keyboard for the keyboard instrument of Figure 6.
Figure 8 is a top plan view of a fourth preferred
embodiment of the invention which is activated by dancers moving
across a stage.
DESCRIPTION OF THE PREFERRED EMBODIMEN~S
Referring to Figures 1 and 2 a light source 10 is
provided which emits a light beam 12 toward detector 14. When
light strikes the detector it emi~s a signal, shown as wave 114
in Figure ~, which is amplified by ampliEier 16 into signal
116. If the 1ight beam is blocked at interrupter 13 (shown in
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chain line) no signaJ wi]l be emitted from the detector 14 The
interrupter 13 could be an instrument ke~, a string, a Einger or
a body. After the signal is amplified it goes to a special
amplifier 18 which responds to the amount of light beam
interruption (indicated by the signal coming from detector 14)
and the rapidity of the interruption. A signal S entering this
amplifier would be transformed into S ~K dS where K is a
dt
constant and dS is the first derivative of S with respect to
time. The transformed signal is shown as wave 118 in Figure
2. Thus modified, the signal is applied to a voltage controlled
amplitude modulator 20 to control the amplitude ~and hence the
loudness) of the signal which is supplied by a frequency
generator 22. The signal emitted by the amplitude modulator 20,
shown as wave 120 in Figure 2, may be fed to a mixer 24 and
there combined with other signals 250 The mixer 24 can be
attached to output controls 26 which may filter, color or
amplify the output before it is fed to a speaker 28.
The present preferred circuitry for the light detector
14 amplifier 16 and special amplifier 18 is shown in Figure 3.
As shown in Figure 3, a light beam 12 strikes a photo transistor
30. The operational amplifier 32 is driven at the output below
ground level when the light beam is not interrupted. As the
light beam begins to be interrupted the photo transistor
supplies a positive signal which is greatly amplified due to the
by-pass diode Dl. When the signal crosses the ground level D
becomes reverse biased, and the amplification depends upon the
setting of the variable resistor 34~ The emerging output signal
is coupled through diode D2 so that only a positive ground-
referenced portion is transmitted to the next stage. This
second stage controls the rapidity of attack by differentiating
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the input signal S to output signal SO according to the formula:
SO = S [1~ (s~C )] where T represents the ef~ective resis-
tance of the con-trol transistor 36, C is the capacitance of C, R
is the resistance of R5l and s = j~ = j2~ f. Thus, if the
transistor is kept non-conducting, T is very large and the
transfer function is merely unity, the output signal emerges
unaffected. However, if the transistor is brought into
conduction through supplying a positive signal controlled by a
foot pedal, then T becomes small and the output signal has a
large differentiated component. The diode D3 cuts out the
negative part of the derivative. The signal from operational
amplifier 38 is then applied to a voltage controlled amplitude
modulator (see Figure 1) to control the volume of a tone
supplied by a frequency generator as described above.
In Figure 4 the invention is applied to produce a
harp-like instrument using light sources 41 and detectors 42.
Each light source produces a beam of light 44 which can be
interrupted with fingers. The light beams can be made of
different colors in the spectrum to correspond to different
notes. Each light detector is wired to an amplifier, special
amplifier, amplitude modulator and frequency generator as shown
in Figure 1. The signals from all of the amplitude modulators
can be mixed electronically and directed to a single output. In
this instrument I prefer to use light beams in place of the
strings of a harp because it would be expensive to produce an
instrument containing strings and light source - light detector
pairs associated with each string. ~owever, one could use my
invention in this manner. Alternatively~ one could make a harp-
]ike instrument containing various combinations of light source
- light detector pairs and strings~ For example, strings could
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be placed at octave intervals for a chosen note to indicate
where the octave changes.
A woodwind-like instrument employing another embodi-
ment of the invention is shown in Figure 5. The instrument has
a mouthpiece 50, body 52 and bell 54. A plurality of keyholes
53 are provided along the body. A rib 56 runs through the
center of the body and SeLveS as a mounting for light sources 58
and detectors 60. One light source 58 and one detector 60 is
provided for each keyhole 58~ When a finger 62, thumb 63 or
instrument key (not shown) is positioned over a keyhole~ light
51 from the light source will be reflected back to the detector
58 which is wired as illustrated in Figure 1. The reflected
light will cause a signal to flow to the amplification mixing
and filtering circuits 64 and speaker 65 contained in the bell
54 to produce sounds. A pressure transducer 66 that senses air
pressure and attached sponge pad 67 for filtering noise are
provided in the mouthpiece for overall volume control. Another
embodiment for volume control can be implemented by pressing a
transducer with the lips or teeth to change the signal flowing
Erom the transducer 66 to the amplification, mixing and
filtering circuits 64 thereby changing the volume. To eliminate
the need for providing amplifiers and a speaker inside the
instrument an output jack can be provided to connect the
instrument to external amplifiers and speakers. This would
enable the instrument to be connected to high quality external
sound systems or recording devices~
Referring now to Figures 6 and 7, a keyboard instru
ment is shown having a body 70 containing two keyboards 72.
Each keyboard is comprised of a rectangular plate 73 having a
series of slots 74 in it. A light source 75 and optional lens
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76 are positioned below each slot to direct light through the
slot an~ focus it on a detector. A light detector 77 is
positioned above each slot. The light detectors are wired to
amplification mixing and filtering circuits in ~ manner such
that interruption of a given light source - light detector
combination will produce a unique sound. Pedal~ 78 are provided
for controlling overall loudness and to control the attack on
transistor T in Figure 3.
A final preferred embodiment shown in Figure 8 is
comprised of light sources 80 and light detectors 82 positioned
on a stage 79. The light detectors ar~ connected to other
components as discussed above so that sounds will be produced by
light beams ~1 striking the detectorsO Interruption of the
light beams by a musician or dancer 84 will cause the tone to
stop with the rapidity of interruption controlling the
loudness. These arrangements on the stage can employ beams
going in any direction vertically and horizontally, and both
interrupting and reflectin~ schemes are conceivableO
If desired, in certain usesl one may eliminate the
specific ampli~ude modulator disclosed hereinbefore and modulate
the light source. For example, in a clarinet type arrangement
one might modulate a solid-state light source with the desired
f~equency from a frequency g~nerator and thereby eliminate the
need for a separate amplitude modulator.
While I have illustrated and described certain present
preEerred embodiments of my invention it is to be distinctly
understood that the invention is not limited thereto but may be
varlously ernbodied within the scope of the following claims.
6.
