Music – Accessories – Recording devices
Reexamination Certificate
1999-09-14
2001-05-08
Donels, Jeffrey (Department: 2837)
Music
Accessories
Recording devices
C084S019000, C084S724000
Reexamination Certificate
active
06229081
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a musical instrument and, more particularly, to a keyboard musical instrument of the type having key sensors for detecting the current positions of keys, a position sensing device and a light-emitting controller both incorporated therein.
DESCRIPTION OF THE RELATED ART
An automatic player piano is an example of the keyboard musical instrument. The automatic player piano records a performance on the keyboard, and stores the performance in a suitable memory in the form of pieces of music data information. When a user requests the automatic player piano to reproduce the performance, the pieces of music data information are read out from the memory, and selectively energizes key actuators so as to move the black/white keys without fingering. Thus, the automatic player piano has two modes of operation, i.e., the recording mode and the playback mode.
Key sensors are provided under the black/white keys, and convert the current key positions to positional signals. The positional signals are supplied to a controller, and the controller extracts the pieces of music data information to be required for the playback from the positional signals and variance thereof. Thus, the key sensors are important components of the automatic player piano.
An optical key sensor is popular to the automatic player piano. A light-emitting diode is paired with a photo-detecting diode, and produces a light beam across a trajectory of a shutter plate attached to the black/white key. If the optical key sensors are individually installed for the black/white keys, the installation makes the price of the automatic player piano go up.
An optical sensor matrix was proposed in Japanese Patent Application No. 7-270332, which was published, as Japanese Patent Publication of Unexamined Application No. 9-54584. Twelve light emitting diodes and eight photo diodes form in combination the optical sensor matrix for the keyboards, which usually consists of eighty-eight black/white keys.
FIG. 1
illustrates the optical sensor matrix. Although the optical sensor matrix is used for eighty-eight black/white keys, only one white key
10
is shown in
FIG. 1. A
shutter plate KS is attached to the lower surface of the white key
10
, and is hatched in
FIG. 1
for the purpose of discrimination. The prior art optical sensor matrix includes a light emitting sensor head
221
, a light receiving sensor head
222
, a light emitting diode array
224
, a photo diode array
225
and bundles of optical fibers
226
and
227
. The light emitting sensor head
221
and the light receiving sensor head
222
are fixed to a frame SB together with other light emitting sensor heads (not shown) and other photo detecting sensor heads
222
(not shown), and are spaced from one another. Twelve light emitting diodes form the array
224
, and eight photo-detecting diodes form the other array
225
. One of the light emitting diodes is connected through an optical fiber of the bundle
226
to the light emitting sensor head
221
, and the light receiving sensor head
222
is connected through an optical fiber of the bundle
227
to one of the photo detecting diodes. Each of the light emitting diodes
224
is connected to eight optical fibers of the bundle
226
, and twelve optical fibers of the bundle
227
are connected to each photo detecting diode
225
. For this reason, eight light emitting sensor heads
221
concurrently radiate the eight optical beams, and the eight photo diodes
225
simultaneously receive the light transferred from the associated light receiving sensor heads
222
through the optical fibers
227
. Although the combinations of the light emitting diodes
224
and the photo detecting diodes
225
are ninety-six, only eighty-eight combinations are used for the eighty-eight black/white keys.
When the light emitting diode
224
is energized, the light emitting diode generates light. The light is propagated through the optical fiber
226
to the light emitting sensor head
221
, and the light emitting sensor head
221
radiates a light beam to the light receiving sensor head
222
across the trajectory of the shutter plate KS. The light beam is 5 millimeter in diameter. The light receiving sensor head
222
receives the light beam, and the received light is propagated through the optical fiber
227
to the associated photo diode
225
. The photo diode
225
converts the light to an electric signal Sa, and supplies the electric signal Sa to a controller (not shown).
The electric signal Sa is representative of the amount of received light. A player is assumed to depress the white key
10
. The white key
10
sinks toward the end position, and the shutter plate KS gradually intersects the light beam. As a result, the amount of received light is decreased, and, accordingly, the photo detecting diode
225
reduces the magnitude or the voltage of the electric signal Sa.
The position-to-voltage converting characteristics of the prior art optical sensor matrix is represented by plots C
1
in FIG.
2
. The rest position of the white key
10
and the end position of the white key
10
are respectively abbreviated as “K
R
” and “K
E
” in FIG.
2
. The shutter plate K
S
partially intersects the optical beam at the rest position K
R
, and the shutter plate K
S
is evacuated from the optical beam at position “K
O
”. The potential level of the electric signal Sa gradually falls from the rest position K
R
to the end position K
E
. When the white key
10
reaches the end position K
E
, the shutter plate KS allows part of the light beam to reach the light receiving sensor head
222
, and the electric signal Sa still has a potential level. If the shutter plate KS reaches the position K
D
, the shutter plate KS perfectly intersects the light beam, and the photo detecting diode
225
decreases the potential level of the electric signal Sa to zero. The white key
10
is moved between the rest position K
R
and the end position K
E
, and the photo detecting diode
225
varies the electric signal along the plots between the rest position K
R
and the end position K
E
.
The position-to-voltage converting characteristics C
1
is determined for a typical key during the fabrication of the automatic player piano, and pieces of control data information representative of the position-to-voltage converting characteristics C
1
are stored in a non-volatile memory. The controller (not shown) determines the current key position on the basis of the position-to-voltage converting characteristics C
1
during the recording, and digital codes representative of the pieces of music data information are produced from the current key position and the variance of the current key position. However, the performance reproduced in the playback is not consistent with the original performance. This is the problem inherent in the prior art automatic player piano.
SUMMARY OF THE INVENTION
It is therefore an important object of the present invention to provide an automatic player piano, which faithfully reproduces an original performance. It is also an important object of the present invention to provide a position sensing device, which exactly determines the current position of a moving object such as, for example, a black/white key.
The present inventors contemplated the problem inherent in the prior art automatic player piano, and noticed that the light emitting diodes
224
, the optical fibers
226
/
227
and the photo diodes
225
had individualities. The individualities were influential on the position-to-voltage converting characteristics. Each of the prior art optical key sensors was the combination of the light emitting diode
224
, the optical fibers
226
/
227
, the light emitting sensor head
221
, the light receiving sensor head
222
and the photo detecting diode
225
, and the position-to-voltage converting characteristics of one optical key sensor were usually different from the position-to-voltage converting characteristics of the others. Moreover, the position-to-voltage converting characteristics were varied with time as i
Sasaki Tsutomu
Ura Tomoyuki
Donels Jeffrey
Morrison & Foerster
Yamaha Corporation
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