Method and apparatus for inputting a voice through a microphone

An apparatus and method for inputting a voice through a microphone mounted at a position facing a speaking person. An image of a speaking person is generated and used to detect the position of a mouth of the speaker. The microphone is then moved in accordance with position of the mouth.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a voice input method and apparatus which provides 
a reliable voice input through a microphone for recognition of voice 
commands even though the microphone is mounted at a distance. 
2. Description of The Related Art 
Various systems have been developed, employing voice recognition, to 
monitor and control entry into and exit from motor vehicles, elevators, 
and important facilities (see, for example, U.S. Pat. Nos. 4,558,298 and 
4,450,545). Such systems are intended to eliminate the inconvenience of 
prior gate or door open/close control systems which employ keys or ID 
(identification) cards (e.g., necessity of carrying a key or an ID card at 
all times and poor operability of the key or ID card sets). Further, such 
systems are intended to open or close a gate (door) by recognizing a voice 
command (e.g., an ID number) from the speech of a person, or by 
identifying the person from characteristics of the input speech. Such 
systems based on voice recognition are very satisfactory, because each 
person does not need to carry his key or ID card at all times and the 
person can be identified with high accuracy by his voice. 
For accurate voice recognition, however, a voice must be collected at a 
high signal-to-noise ratio without contamination of ambient noise. 
Conventionally, a handset type microphone or close range microphone was 
used to avoid possible noise contamination. Either of these microphones 
may collect speech at a very close position to the mouth of a speaking 
person and achieve a desired high S/N ratio of input speech. These 
microphones, however, require a person to hold them during speaking, 
resulting in impaired operability. 
To collect only desired voice sounds, the use of soundproof walls or sharp 
directional microphones has been considered for cutting off ambient noise. 
However, soundproof walls may be very expensive and the voice input 
apparatus may be rendered inappropriate for many uses. When a sharp 
directional microphone is employed, if the directional reception sector 
for the microphone deviates slightly from the direction toward the 
speaking person's mouth, it might collect a large amount of ambient noise 
together with desired speech, thereby reducing the S/N ratio drastically. 
As is obvious from the foregoing, the related voice input apparatus based 
on voice recognition technology still have many problems. Remaining 
unsolved, until this invention, is the problem of how a person's speech 
can be collected at a high S/N ratio without impairing the usefulness and 
operability of the voice input apparatus. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a voice 
input apparatus and method which can collect voice data from a person at a 
high S/N ratio without impairing the usefulness and operability of the 
voice input apparatus. 
In accordance with the present invention, the foregoing object, among 
others, is achieved by providing an apparatus and method for inputting a 
voice through a microphone mounted at a position facing a speaking person. 
An image of the speaking person is generated and employed to detect the 
position of the mouth of the person. Then, the microphone can be moved 
automatically in accordance with the position of the mouth of the speaker. 
Preferably, the direction of the microphone toward the mouth is determined 
based on the position of the mouth in relation to the mounting position of 
the microphone.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
One of the preferred embodiments of the present invention will be described 
with reference to the accompanying drawings. 
FIG. 1 is a schematic block diagram of the voice input apparatus according 
to one embodiment of the present invention. FIG. 2 is a schematic 
illustration for showing the operation thereof. The apparatus may be 
introduced into a system which opens or closes a door and monitors all 
persons passing through the door by speech and/or voice recognition 
technology. It should be obvious that the apparatus is applicable to 
vending machines, auto tellers' machines and any other apparatus using 
speech and/or voice input and speech recognition technology. 
Referring to FIGS. 1 and 2, a microphone 12 used herein has sharp 
unidirectional characteristics. The microphone 12 is supported by a 
servomechanism (moving means) 14 for positioning the microphone 12. The 
servomechanism is mounted to the upper portion of a wall A. The 
servomechanism 14 operates to adjust the direction of the microphone 12 
within a range which covers the voice input area B in front of the wall A 
in accordance with a well known technique. Speech collected through the 
microphone 12 is transmitted to a vocal recognition device 16 for speech 
and/or voice recognition processing. For this recognition processing, one 
possible technique is disclosed in U.S. Pat. No. 3,688,267. The resulting 
data from the vocal recognition device 16 is then transmitted to a 
controller 18 for opening or closing the door, which is driven by a door 
open/close mechanism 20. This door open/close mechanism 20 may be as 
described in U.S. Pat. No. 4,472,617, etc. 
On the wall A, a camera (picking up means) 22 is provided for picking up an 
image of a person C who enters the voice input area B to speak. The image 
of the person C is picked up as shown in FIG. 3. The image of the person C 
picked up by the camera 22 is processed by a picture processor (detecting 
means) 24 to obtain information relating to the position of the person's 
mouth. This technique is disclosed in IEICE Technical Report Vol. 87, No. 
71, pp. 7-12. Positional information for the mouth is supplied to the 
controller (determining means) 18 for determining the direction of the 
microphone 12. It should be appreciated that a panel D is provided behind 
the voice input area B at the opposite side of wall A. The panel D 
prevents the camera 22 from picking up undesired background noise from 
behind the person C. It should be further appreciated that the panel D may 
be omitted since the image of the person C can be discriminated from the 
background when the background is outside of the depth of focus of the 
lens system of the camera 22 when the lens system is focused on person C. 
A speaker 26 embedded in the wall A produces audio messages from the system 
to the person C. An audio response unit 28 activated by the controller 18 
synthesizes aural signals by a well known synthesis-by-rule method 
according to message information submitted by the system and drives the 
speaker 26 to produce suitable audio messages. 
An ultrasonic sensor 30 is also mounted on the wall A under the speaker 26. 
The ultrasonic sensor 30 is energized by a distance detecting circuit 32 
to transmit ultrasonic waves at the person C. The distance detecting 
circuit 32 measures the period of time from wave transmission to reception 
of reflected waves at the ultrasonic sensor 30 to detect the distance 
between the wall A and the person C entering the voice input area B. The 
distance information detected by the distance detecting circuit 32 is also 
supplied to the controller 18 for controlling the directional adjustment 
of the microphone 12. 
The controller 18 is connected to a host computer 34. The host computer 34 
matches the output data of the speech or voice recognition device 16 with 
the previously registered management data such as a person's ID number. In 
addition, the host computer 34 also generates response messages for each 
speech input and guidance messages to be given to the person C. 
The above configuration of the present invention provides the following 
operation. Control of the direction of the microphone 12, is one of the 
distinctive features of the present apparatus and is accomplished, as 
described above, according to positional information for the mouth which 
is obtained from the person's image picked up by the camera 22, the 
distance information detected by means of the ultrasonic sensor 30, and 
the mounting position information for the microphone 12. 
The picture processor 24 eliminates the background information from the 
picture signals transmitted from the camera 22 and provides horizontal 
projection X of the image of the person C as shown in FIG. 3. The 
components a, b, ...,h of the projection X are scanned. Scanning first 
occurs from top a to a point b in FIG. 3 where luminance first changes. 
The point b where luminance first changes is considered the top of the 
person's head. Luminance changes of the projection X are further scanned 
to determine that the component d shows the forehead portion, the 
component e shows the eye portion, the component g shows the mouth 
portion, and the component h shows the neck portion. These determinations 
can be made because the luminance of the hair (head) portion, the eye 
portion, and the mouth portion are largely different as compared with the 
skin portion where the luminance is almost uniform. The vertical component 
Mx of the mouth position in the person's image can be detected from the 
relation between the difference in luminance and the detected position. 
Then, the horizontal luminance change Y in the face image detected above is 
determined to locate the position of each ear in the image and calculate 
horizontal components F1 and F2 of the face position of the person C. The 
horizontal component My of the mouth position is calculated from the 
horizontal components F1 and F2 by the equation: 
EQU My=(F1+F2)/2 
After the position of the person's mouth in the image picked up by the 
camera 22 is obtained, the mouth position in the three-dimensional voice 
input area B is calculated from the optical system position defined by the 
lens system of the camera 22 and the distance information to the person C 
detected by means of the ultrasonic sensor 30. The optimal direction of 
the microphone 12 toward the mouth of the person C in the 
three-dimensional space (relative angle) is calculated from the positional 
information of the mouth and the positional information of the microphone 
12. The microphone driving servomechanism 14 is driven to adjust the 
direction of the microphone 12 so that it corresponds to the calculated 
direction. 
As a result, the microphone 12 is directed toward the mouth of the person C 
and the speech from the person C can be collected at a high S/N ratio. 
In the operation of the gate entrance/exit control system which employs the 
present apparatus, the system first detects the entrance of a person into 
the voice input area B by the ultrasonic sensor 30 as described above. The 
present apparatus is activated by the detection signal of the person C. 
The audio response unit 28 is then activated and through speaker 26 issues 
to person C the audio message: "Please face the camera." The camera 22 
picks up the image of the person C facing the camera. At the same time, 
the distance to the person C is calculated by means of reflected 
ultrasonic waves activated by the ultrasonic sensor 30. Then the mouth 
position of the person C is calculated as described above to determine the 
direction of the microphone 12 toward the mouth. 
After these procedures, the system is ready for voice input and issues to 
the person C the audio message: 
"Please say your ID number." 
Speech of the person C is collected by the microphone 12. The vocal signal 
collected by the microphone 12 is processed by the vocal recognition 
device 16 so that the recited ID number is made machine-readable. The 
processed data is sent to the host computer 34 through the controller 18. 
If the speech is not recognized properly, the system issues to the person C 
the message: 
"Please say your ID number again clearly digit by digit." 
to ask for reentry of the ID number and the second speech is again 
processed by the vocal recognition device 16. 
The recognized ID number is compared with previously registered management 
data to determine whether the person C should be admitted into the 
facility. When the person C is found to be admittable, the door open/close 
mechanism 20 is driven to open the door with the message issued: 
"The door will open. Please come in." 
When the person C is not found to be admittable, the system issues to the 
person C the message: 
"Your ID number is not found. The door will not open." 
A sequence of processes of the system is completed with one of these 
messages. 
It should be apparent to those skilled in the art that individual 
identification of the person may also be accomplished by extracting 
personal characteristics of the input voice pattern during the speech 
recognition process. This may be done in lieu of, or in combination with 
the speech recognition method. 
According to the present apparatus, the microphone 12 with a sharp 
directivity can be effectively directed toward the mouth of the person C, 
thereby resulting in reliable collection of the speech made by the person 
at a high S/N ratio. The sharply directional microphone 12 used herewith 
can be provided at a distance from the person C without any loss in S/N 
ratio. Consequently, the person can speak unaffected by the presence of 
the microphone 12, and the person will not feel that he is forced to speak 
to the system. In addition, even when both hands are occupied, easy entry 
of an ID number or any other information can be achieved by speaking. 
By setting a person at ease during speaking, a better reflection of 
personal characteristics in the input voice and enhanced accuracy for 
individual identification can be expected. 
It should be understood that the present invention is not limited to the 
aforementioned embodiment. In the foregoing, the present invention has 
been described in conjunction with an entrance/exit control system through 
door open/close control, but it should be further understood that the 
present invention may be applicable to other systems based on voice input 
technology. The picture processing used herewith is not limited to a 
particular type and the picture processing may also be used to calculate 
the distance to the person C, (see, e.g., Japan patent application No. 
62-312192), which will eliminate the distance calculating process with 
ultrasonic waves. 
Moreover, it should be also understood that various modifications to the 
present invention will be apparent to those skilled in the art without 
departing from the spirit and scope of the invention. Such modifications 
are intended to be included in this application as defined by the 
following claims.