JP2010193064A - A/d converter and headset - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an A/D converter capable of performing analog/digital conversion of a plurality of analog signals at a low cost, and a headset utilizing the A/D converter. <P>SOLUTION: The A/D converter includes: a signal composition part 104 for inputting the plurality of analog signals and successively switching the respective analog signals to composite one signal; an A/D conversion part 105 for performing analog/digital conversion of the signal composited by the signal composition part 104; and a signal separation part 106 for separating digital signals from the A/D conversion part 105 in timing corresponding to signal switching timing in the signal composition part 104. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an A / D conversion device and a headset.

  Conventionally, various sensors such as an acceleration sensor, a tilt sensor, a gyro sensor, an impact sensor, and a magnetic field sensor, a speaker and a microphone are provided, and processing of output signals from the various sensors and processing of audio signals related to the speaker and microphone are performed. A head-mounted information processing apparatus is known (see, for example, Patent Document 1).

JP 2002-141841 A

However, conventionally, when the analog signals output from various sensors and the output from the microphone are converted into digital signals as described above, each analog signal is converted into an analog signal using a separate A / D converter.・ Digital conversion. That is, when there are a plurality of analog signals, a plurality of A / D converters are required. Therefore, the problem is that the cost of the apparatus increases by the amount of the A / D converter.
In addition, since a plurality of analog signals do not necessarily have to be sampled at the same sampling rate, they correspond to analog signals whose sampling rate may be low among a plurality of A / D converters provided. An A / D converter will actually only use part of its capabilities. For example, the audio signal needs to be sampled at several kHz, but the acceleration data often does not need to be sampled at such a high frequency. Therefore, the capability of the apparatus is not used effectively, and the cost spent is wasted.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an A / D converter capable of analog-digital conversion of a plurality of analog signals at low cost, and the A / D converter. It is to provide a headset using the.

The present invention has been made in order to solve the above-described problem. A signal synthesis unit that inputs a plurality of analog signals and synthesizes them into one signal by sequentially switching the analog signals, and synthesis by the signal synthesis unit An A / D converter that performs analog / digital conversion of the received signal, and a signal separator that separates the digital signal from the A / D converter at a timing corresponding to the signal switching timing in the signal synthesizer. This is an A / D conversion device.
In the A / D converter according to the present invention, the signal synthesizer synthesizes a signal by applying a predetermined gain to each analog signal.
In the A / D converter according to the present invention, the signal synthesizer switches each analog signal every clock of a predetermined clock signal.

  The present invention also relates to a headset that has a microphone and a speaker and is worn on the head, which collects sound and outputs an analog signal based on the collected sound, and movement of the wearer of the headset An acceleration sensor that detects an acceleration corresponding to the detected acceleration, outputs an analog signal based on the detected acceleration, an analog signal from the microphone and an analog signal from the acceleration sensor, and sequentially switches each analog signal to A signal synthesizer for synthesizing the signal, an A / D converter for analog-to-digital conversion of the signal synthesized by the signal synthesizer, and the A / D conversion at a timing corresponding to a signal switching timing in the signal synthesizer A signal separation unit for separating the digital signal from the unit and a signal representing the acceleration separated by the signal separation unit. A number of steps calculation unit for calculating the number of steps of the wearer's set, a headset, comprising a communication unit, the transmitting signals representing sound separated by the signal separation unit to the external device.

The A / D converter and the headset according to the present invention sequentially switch a plurality of analog signals to combine them into one analog signal, and convert the combined signal from analog to digital. Therefore, according to the A / D conversion device and the headset according to the present invention, it is possible to perform analog / digital conversion of a plurality of analog signals, and a plurality of A / D conversion devices are not necessary, so that the cost can be reduced. .
Further, by synthesizing signals by applying a predetermined gain to each analog signal, the maximum value level of each signal becomes substantially equal. Therefore, the sensitivity of analog-digital conversion for a plurality of analog signals can be made comparable.
Further, by switching each analog signal for every clock of a predetermined clock signal, sampling of each analog signal can be performed evenly in time. As a result, there is no inconvenience that a digital signal for a certain analog signal cannot be obtained over a long period of time (conversion to another analog signal is performed during that time).

It is a block diagram which shows the structure of the headset with a heart rate measurement function by one Embodiment of this invention. It is a timing chart for demonstrating the specific example of operation | movement of a signal synthetic | combination part, an A / D conversion part, and a signal separation part. It is a block diagram which shows the structure inside a heart rate calculation part. It is a figure explaining an example of the calculation method of the step count by a step count calculation part. It is a figure for demonstrating the operation | movement which a direction calculation part calculates the direction of a head.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a headset with a heart rate measurement function according to an embodiment of the present invention. The headset is an audio device that includes a microphone and a speaker (earphone) and exchanges audio signals with an external device (for example, a telephone, not shown in FIG. 1). The microphone and the speaker are arranged near the ear and mouth. It has a shape that can be worn on the user's head in a state. In FIG. 1, a headset 100 includes a microphone 101, an acceleration sensor 102, a gyro sensor 103, a signal synthesis unit 104, an A / D conversion unit 105, a signal separation unit 106, filters 107 to 109, a heart rate. A number calculation unit 110, a step count calculation unit 111, a direction calculation unit 112, a D / A conversion unit 113, a speaker 114, a communication unit 115, and an antenna 116 are configured.

  The headset 100 of this embodiment includes a step count measurement function and a direction (head orientation) measurement function in addition to the heart rate measurement function. 1, the microphone 101, the filter 107, and the heart rate calculation unit 110 correspond to the heart rate measurement function, the acceleration sensor 102, the filter 108, and the step count calculation unit 111 correspond to the step count measurement function, and the gyro sensor 103, The filter 109 and the direction calculation unit 112 correspond to the direction measurement function. In addition, each part other than these in FIG. 1 is a part used in common for each measurement function of the heart rate, the number of steps, and the direction, or a part used for the original voice function of the headset. Each part will be described below in order.

  The microphone 101 collects sound and outputs an audio signal (analog) to the signal synthesis unit 104. The microphone 101 is inserted into the ear or placed near the ear when the headset 100 is worn on the head. Since the heartbeat sound transmitted through the body exists in the ear, the heartbeat sound can be collected by the microphone 101. In addition to the heartbeat sound, the sound collected by the microphone 101 includes a voice spoken by the user wearing the headset 100 and other environmental sounds.

  Here, the repetition frequency of the heartbeat is normally in the range of about 1 to several Hz, and the waveform of the heartbeat (one cycle) is composed of components having a frequency higher than the repetition frequency. In order to collect such heartbeat sounds, it is assumed that the microphone 101 has a frequency characteristic in which the lowest frequency that can be collected is at least 10 Hz or less.

  The acceleration sensor 102 outputs an electrical signal (analog) corresponding to the acceleration applied in a predetermined one axis direction to the signal synthesis unit 104. Here, it is assumed that the acceleration sensor 102 is attached to the headset 100 so that a predetermined one-axis direction is a vertical direction (vertical direction) when viewed from the user wearing the headset 100. That is, the acceleration sensor 102 can detect acceleration when the user wearing the headset 100 moves up and down.

  The gyro sensor 103 outputs an electrical signal (analog) corresponding to the angular velocity around a predetermined axis to the signal synthesis unit 104. Here, it is assumed that the gyro sensor 103 is attached to the headset 100 so that the predetermined axis is an axis (vertical axis) parallel to the neck of the user wearing the headset 100. That is, the gyro sensor 103 can detect the angular velocity when the user wearing the headset 100 turns his / her head left and right.

  The signal synthesis unit 104 sequentially switches the signals from the microphone 101, the acceleration sensor 102, and the gyro sensor 103 in a predetermined cycle to synthesize them into one signal, and outputs the synthesized signal to the A / D conversion unit 105. In other words, the audio signal from the microphone 101 is output from the signal synthesis unit 104 at a certain timing, the electrical signal from the acceleration sensor 102 is output at another certain timing, and the gyro sensor 103 from the gyro sensor 103 at another certain timing. An electrical signal is output, and the output signal of the signal synthesis unit 104 is a signal in which these are periodically repeated.

  In general, the signal from the microphone 101, the signal from the acceleration sensor 102, and the signal from the gyro sensor 103 have different maximum levels. Therefore, the signal synthesizer 104 multiplies each signal from the microphone 101, the acceleration sensor 102, and the gyro sensor 103 with a predetermined constant gain so that the maximum value level of each signal becomes substantially equal. Therefore, each signal is synthesized. In this way, when analog / digital conversion is performed by the A / D conversion unit 105, the sensitivity of analog / digital conversion for the signals from the microphone 101, the acceleration sensor 102, and the gyro sensor 103 can be made comparable. it can.

  The A / D conversion unit 105 performs analog / digital conversion on the signal (analog) from the signal synthesis unit 104 and outputs the converted signal (digital) to the signal separation unit 106. As described above, the signal from the signal synthesis unit 104 is one signal synthesized by sequentially switching the signals from the microphone 101, the acceleration sensor 102, and the gyro sensor 103. Therefore, the output signal of the A / D conversion unit 105 includes an analog / digital conversion result for the signal from the microphone 101, an analog / digital conversion result for the signal from the acceleration sensor 102, and an analog / digital conversion result for the signal from the gyro sensor 103. Is a digital signal that is sequentially arranged.

  The signal separation unit 106 separates the signal from the A / D conversion unit 105 at a timing corresponding to the signal switching timing in the signal synthesis unit 104, and outputs the separated signals to the corresponding filters 107-109. Specifically, the signal separation unit 106 outputs the output signal of the A / D conversion unit 105 (a signal obtained by analog-to-digital conversion of the signal from the microphone 101 at the timing when the signal synthesis unit 104 outputs the signal from the microphone 101. ) To the filter 107, and at the timing when the signal synthesis unit 104 outputs a signal from the acceleration sensor 102, an output signal of the A / D conversion unit 105 (a signal obtained by analog-digital conversion of the signal from the acceleration sensor 102) Is output to the filter 108, and at the timing when the signal synthesis unit 104 outputs the signal from the gyro sensor 103, the output signal of the A / D conversion unit 105 (a signal obtained by analog-digital conversion of the signal from the gyro sensor 103) is output. Output to the filter 109.

  FIG. 2 shows a timing chart for explaining specific examples of operations of the signal synthesis unit 104, the A / D conversion unit 105, and the signal separation unit 106. In FIG. 2, the signal synthesizer 104 generates a switching signal MIC for switching the output signal to the audio signal from the microphone 101, for periods T1, T3, T5, T7, T9, T11,. Turn on. Further, the signal synthesizer 104 turns on the switching signal ACC for switching the output signal to the electrical signal from the acceleration sensor 102 in the periods T2, T6, T10,... Every four clocks of the clock signal CLK. Further, the signal synthesizer 104 turns on the switching signal GYR for switching the output signal to the electric signal from the gyro sensor 103 in the periods T4, T8, T12,... Every four clocks of the clock signal CLK.

  As a result, in the period T1, the output signal of the signal synthesis unit 104 is an audio signal from the microphone 101, in the period T2, the output signal of the signal synthesis unit 104 is an electric signal from the acceleration sensor 102, and in the period T3, the signal synthesis is performed. The output signal of the unit 104 is an audio signal from the microphone 101, and the output signal of the signal synthesis unit 104 is an electrical signal from the gyro sensor 103 in the period T 4. Thereafter, similarly, the output of the signal synthesis unit 104 is switched in the order of the audio signal from the microphone 101, the electrical signal from the acceleration sensor 102, the audio signal from the microphone 101, and the electrical signal from the gyro sensor 103.

  Here, if the A / D conversion unit 105 performs analog / digital conversion in synchronization with the clock signal CLK, the output signal AD_OUT of the A / D conversion unit 105 is digital of the audio signal from the microphone 101 in the period T1. It becomes a digital value of the electrical signal from the acceleration sensor 102 in the period T2, becomes a digital value of the audio signal from the microphone 101 in the period T3, and becomes a digital value of the electrical signal from the gyro sensor 103 in the period T4 (hereinafter, also) The same). In addition, the signal separation unit 106 outputs the digital value of the audio signal from the microphone 101 to the filter 107 in the period T1, outputs the digital value of the electric signal from the acceleration sensor 102 to the filter 108 in the period T2, and in the period T3. The digital value of the audio signal from the microphone 101 is output to the filter 107, and in the period T4, the digital value of the electrical signal from the gyro sensor 103 is output to the filter 109 (the same applies thereafter).

Returning to FIG.
The filter 107 passes a frequency component lower than a predetermined frequency, which is a main frequency component constituting the heartbeat waveform, out of the frequency components included in the audio signal from the microphone 101 output from the signal separation unit 106. It outputs to the heart rate calculation part 110, and cuts off frequency components higher than the predetermined frequency. Here, as described above, the audio signal from the microphone 101 includes the user's speaking voice in addition to the heartbeat. The heartbeat is mainly composed of frequency components of approximately 100 Hz or less, and the user's voice is mainly composed of frequency components of 500 Hz or more. Therefore, by setting the pass frequency band of the filter 107 to 100 Hz or less, only the heartbeat signal component can be output to the heart rate calculator 110.

  The filter 108 includes, among frequency components included in the electrical signal from the acceleration sensor 102 output from the signal separation unit 106, a frequency component corresponding to vibration when the user wearing the headset 100 walks or runs. It is passed and output to the step count calculation unit 111, and other frequency components are blocked. Since vibration due to walking or running is at most several Hz, the characteristics of the filter 108 only need to pass a frequency component of 100 Hz or less and block higher frequency components, for example. Thereby, the high frequency noise component contained in the electrical signal from the acceleration sensor 102 can be removed.

  The filter 109 includes a predetermined frequency component corresponding to the speed at which the user wearing the headset 100 moves the head among the frequency components included in the electrical signal from the gyro sensor 103 output from the signal separation unit 106. It passes and outputs to the direction calculation part 112, and cuts off other frequency components. Since the speed at which the user moves the head is at most several times per second, the characteristics of the filter 109 may be those that pass a frequency component of 100 Hz or less and block higher frequency components, for example. Thereby, the high frequency noise component contained in the electrical signal from the gyro sensor 103 can be removed. Further, by removing the noise component, it is possible to reduce a drift error (an error caused by integrating the angular velocity) when the direction calculation unit 112 described later calculates the head direction.

  The heart rate calculator 110 measures the heart rate (the number of heartbeats per unit time) based on the audio signal corresponding to the waveform of the heartbeat sound output from the filter 107. FIG. 3 is a block diagram showing an internal configuration of the heart rate calculation unit 110. In FIG. 3, the heart rate calculation unit 110 includes a reference waveform storage unit 1101, a correlation waveform extraction unit 1102, and a counting unit 1103.

  The reference waveform storage unit 1101 stores a waveform for one cycle of the heartbeat sound. This waveform is prepared in advance by, for example, collecting heartbeat sounds of a large number of persons and averaging the waveforms. Hereinafter, this waveform is referred to as a reference heartbeat waveform.

  The audio signal from the filter 107 is input to the correlation waveform extraction unit 1102. The correlation waveform extraction unit 1102 correlates the waveform of the input voice signal with the reference heartbeat waveform stored in the reference waveform storage unit 1101, and extracts a waveform highly correlated with the reference heartbeat waveform from the input voice signal. The data is output to the counting unit 1103. As a result, an audio signal that does not include unnecessary low-frequency audio that cannot be completely removed by the filter 107 and includes only heartbeat sound is output to the counting unit 1103. Note that the high correlation with the reference heartbeat waveform means that the correlation value between the input voice signal waveform and the reference heartbeat waveform is equal to or greater than a predetermined threshold value.

  The reference waveform storage unit 1101 may store data indicating the characteristics of the reference heartbeat waveform instead of storing the reference heartbeat waveform itself. In this case, the correlation waveform extraction unit 1102 may extract a waveform having a high degree of coincidence with the feature data stored in the reference waveform storage unit 1101 from the input voice signal.

  The counting unit 1103 counts the number of repetitions of the audio signal waveform output from the correlation waveform extraction unit 1102 (a waveform based only on heartbeat sounds), and outputs the counted value as a heart rate. The audio signal waveform from the correlation waveform extraction unit 1102 is a waveform in which one heartbeat waveform corresponds to one beat of the heartbeat and a plurality of the heartbeat waveforms are temporally continuous. By obtaining the number of repetitions, the heart rate can be obtained.

The description returns to FIG. 1 again.
The step count calculation unit 111 measures the number of steps based on the output signal from the filter 108. The output value from the filter 108, that is, the acceleration value obtained by removing the high-frequency noise component from the acceleration detected by the acceleration sensor 102, is used when the headset 100 is worn, for example, as a curve (acceleration measurement data) shown in FIG. The positive and negative values are repeated according to the vertical movement of the person. Here, for example, while the acceleration value takes a positive value, the user is in a state of moving up while walking or running, and while the acceleration value takes a negative value, the user moves down. Is in a state of performing. Therefore, the step count calculation unit 111 counts the number of steps by determining that the acceleration value has crossed the zero point twice from the positive value to the negative value or from the negative value to the positive value, thereby determining one step in walking or running. be able to.

The direction calculation unit 112 measures the orientation of the head based on the output signal from the filter 109. Specifically, the direction calculation unit 112 stores the orientation θ0 of the head 900 of the headset wearer at the initial time t = t0 (FIG. 5A), and the filter 109 Of the head 900 at an arbitrary time t after the initial time t0 by adding an integrated value to the initial value θ0 from time to time, that is, the angular velocity ω detected by the gyro sensor 103. (B) and (C) in FIG. That is, the orientation of the head at time t = t0 + Δt is θ = θ0 + ω1 · Δt
The head orientation at time t = t0 + 2Δt is θ = θ0 + ω1 · Δt + ω2 · Δt
((C) in the figure). However, ω1 and ω2 are angular velocities detected by the gyro sensor 103 at times t = t0 + Δt and t = t0 + 2Δt, respectively, and Δt is one sampling period (see FIG. 2) for the output from the gyro sensor 103. 4 clocks). The head direction is assumed to be, for example, the front of the face of the headset wearer.

  The communication unit 115 performs wireless communication between the headset 100 and a device outside the headset 100 via the antenna 116. Specifically, the communication unit 115 acquires data representing the heart rate from the heart rate calculation unit 110, acquires data representing the number of steps from the step number calculation unit 111, and data representing the head direction from the direction calculation unit 112. And send the acquired data to an external device. These data transmitted to the external device can be displayed on the display screen of the external device or stored in the memory of the external device, for example. Further, the communication unit 115 acquires the audio signal of the microphone 101 directly from the signal separation unit 106 and transmits it to an external device. As described above, the voice signal includes the voice of the user wearing the headset 100. The communication unit 115 receives an audio signal from an external device. The received audio signal (digital) is converted from digital to analog by the D / A converter 113, and the converted audio signal (analog) is input to the speaker 114, and the audio is emitted from the speaker 114. The external device is, for example, a telephone, and the communication unit 115 exchanges telephone voice signals with the telephone, so that a user wearing the headset 100 can make a telephone call without bringing the ear or mouth close to the telephone.

As described above, the embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the above, and various design changes and the like can be made without departing from the scope of the present invention. It is possible to
For example, FIG. 2 showing the timings at which the signal synthesis unit 104 turns on the switching signals MIC, ACC, and GYR is merely an example, and the timing at which each switching signal is turned on may be changed to another mode. As another aspect, since there are few practical problems even if the rate at which the output of the acceleration sensor 102 or the gyro sensor 103 is sampled is lower than the rate at which the output of the microphone 101 is sampled, the switching signals ACC and GYR For example, the clock signal CLK may be turned on every 20 clocks (every 4 clocks in FIG. 2).
The communication unit 115 may perform communication by wire.

  DESCRIPTION OF SYMBOLS 100 ... Headset 101 ... Microphone 102 ... Acceleration sensor 103 ... Gyro sensor 104 ... Signal synthesis | combination part 105 ... A / D conversion part 106 ... Signal separation part 107-109 ... Filter 110 ... Heart rate calculation part 111 ... Step count calculation part 112 ... Direction calculation unit 113 ... D / A conversion unit 114 ... speaker 115 ... communication unit 116 ... antenna 1101 ... reference waveform storage unit 1102 ... correlation waveform extraction unit 1103 ... counting unit

Claims (4)

A signal synthesizer for inputting a plurality of analog signals and synthesizing them into one signal by sequentially switching each analog signal;
An A / D converter for analog / digital conversion of the signal synthesized by the signal synthesizer;
A signal separation unit for separating the digital signal from the A / D conversion unit at a timing corresponding to a signal switching timing in the signal synthesis unit;
An A / D conversion device comprising:   The A / D conversion apparatus according to claim 1, wherein the signal synthesis unit synthesizes the signals by multiplying each analog signal by a predetermined gain.   The A / D converter according to claim 1, wherein the signal synthesis unit switches each analog signal for each clock of a predetermined clock signal. A headset that has a microphone and a speaker and is worn on the head,
A microphone that collects sound and outputs an analog signal based on the collected sound;
An acceleration sensor that detects acceleration according to the movement of the headset wearer and outputs an analog signal based on the detected acceleration;
A signal synthesis unit that inputs an analog signal from the microphone and an analog signal from the acceleration sensor, and synthesizes the analog signal into one signal by sequentially switching each analog signal;
An A / D converter for analog / digital conversion of the signal synthesized by the signal synthesizer;
A signal separation unit for separating the digital signal from the A / D conversion unit at a timing corresponding to a signal switching timing in the signal synthesis unit;
A step calculation unit that calculates the number of steps of the wearer of the headset based on the signal representing the acceleration separated by the signal separation unit;
A communication unit that transmits a signal representing the sound separated by the signal separation unit to an external device;
A headset comprising:

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