Abstract:
A pulse wave monitor having a structure capable of automatically performing optimal positioning of a pulse wave probe with respect to a user&#39;s body. A plurality of transmitting piezoelectric vibrators for transmitting an ultrasonic wave to an artery are provided along with a plurality of receiving piezoelectric vibrators for receiving an ultrasonic wave from the artery. An optimal combination of a transmitting piezoelectric vibrator and a receiving piezoelectric vibrator for use in pulse wave measurement is determined based on the intensity of a received ultrasonic wave signal. Ultrasonic wave transmission and reception are made by the optimal combination so that accurate pulse wave detection measurement is made possible by automatic positioning of the pulse wave probe.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to pulse wave detecting devices and, more particularly, to a pulse wave detecting device for detecting a pulse wave by transmitting and receiving an ultrasonic wave to and from an artery. 
     It is broadly implemented to detect a pulse wave from blood flow through an artery, at medical sites or in health care. Pulse wave detection is broadly conducted by electronically, automatically detecting a pulse frequency or the like by using a pulse wave detecting device, besides detecting of a pulse frequency per a given time through palpation. 
     The devices which electronically detect a pulse wave and acquire a pulse frequency include those having a piezo-type piezoelectric element that is to be positioned as a sensor over an artery in order to detect a pulse frequency from a pressure change of a surface skin caused due to an artery pressure change (surface skin displacement by pressure) and those using an ultrasonic wave to detect a pulse frequency. 
     The pulse wave detecting devices using an ultrasonic wave include those utilizing the Doppler effect due to blood flow, as proposed, e.g. in Japanese Patent Laid-open No. 214335/1989 and U.S. Pat. No. 4,086,916. 
     With reference to FIGS. 5A and 5B, the conventional pulse wave detecting device  1  will be explained on its basic structure and operation. 
     The pulse wave detecting device  1  is mounted on a wrist watch and used as below. 
     First, a pulse wave probe having an ultrasonic wave transmitting transducer  11  and ultrasonic wave receiving transducer  21  formed by a plurality of piezoelectric vibrators is slidably mounted by screwing in an optimal position of a watch strap for detecting a pulse wave (e.g. in a position where the pulse wave detection signal assumes a maximum). 
     When actually detecting a pulse wave by the pulse wave detecting device  1 , as shown in FIGS. 5A and 5B an ultrasonic wave A is transmitted from the piezoelectric element of the ultrasonic wave transmitting transducer  11  driven by a drive part  12  toward an artery  2  in a human body surface  3 . Then, a reflection wave B reflected by the blood flowing through the artery  2  is received by the ultrasonic wave receiving transducer  21 . 
     Next, the reflection ultrasonic wave B thus received is waveform-detected by a receiving part  22 . The waveform-detected ultrasonic wave is processed in a signal processing part  23  to detect a change in frequency or phase of the reflection wave B. The signal processed by the signal processing part  23  is displayed of its waveform on a display device of an output part  24 . 
     When the heart contracts, the blood flowing through the artery  2  is high in speed. Accordingly, the reflection wave of ultrasonic wave transmitted toward the artery  2  is increased in frequency due to the Doppler effect. Conversely, when the heart expands the blood flowing speed is low and hence the frequency thereof decreases. 
     In this manner, an ultrasonic wave is radiated to a blood flow in an artery varying in speed depending on heart pulsation. By detecting a change of frequency, it is possible to detect a pulse wave, and furthermore a pulse frequency or a blood flow speed. 
     However, the above pulse wave detecting device  1  has the following defects. 
     First, when wearing the wrist watch type pulse wave detecting device  1  on a wrist, it takes time in adjusting and positioning, by sliding, the pulse wave probe to an optimal position for detecting a pulse wave. 
     Second, even where the wrist watch type pulse wave detecting device  1  be worn at an optimal position on the wrist, if the pulse wave probe is deviated in position because of a subsequent movement of the body or the like, then correct measurement would be impossible to conduct. 
     SUMMARY OF THE INVENTION 
     It is therefore a first object of the present invention to provide a pulse wave detecting device which is capable of automatically positioning a pulse wave probe in an optimal position when putting the pulse wave detecting device. 
     It is a second object of the invention to provide a pulse wave detecting device in which a pulse wave probe can be newly positioned automatically in an optimal position even when there is positional deviation in the pulse wave probe after wearing the pulse wave detecting device. 
     In the present invention, the first and second objects are achieved by a pulse wave detecting device comprising transmitting means having a plurality of transmitting piezoelectric vibrators to transmit an ultrasonic wave toward an artery, receiving means having a plurality of receiving piezoelectric vibrators to receive an ultrasonic wave propagating through the artery, pulse wave information acquiring means for acquiring pulse wave information from an ultrasonic wave signal transmitted from any one of the transmitting piezoelectric vibrators and received by any one of the receiving piezoelectric vibrators, signal intensity detecting means for detecting a signal intensity of the received ultrasonic wave by the receiving means, and optimal combination determining means for determining an optimal combination of a transmitting piezoelectric vibrator to be used by the transmitting means and a receiving piezoelectric vibrator to be used by the receiving means on the basis of the signal intensity of the ultrasonic wave detected by the signal intensity detecting means, and causing the transmitting piezoelectric vibrator of the optimal combination to transmit an ultrasonic wave and the receiving piezoelectric vibrator of the optimal combination to receive the ultrasonic wave. 
     Also, the optimal combination determining means has switching means to switch to any one of the transmitting piezoelectric vibrators and selecting means to select any one of the receiving piezoelectric vibrators, the optimal combination determining means causing the switching means and the selecting means to change in order over the transmitting piezoelectric vibrators and the receiving piezoelectric vibrators, respectively, and determining an optimal combination of the transmitting piezoelectric vibrator and the receiving piezoelectric vibrator assuming a maximum value in signal intensity of an ultrasonic wave. 
     Also, the optimal combination determining means causes the switching means and the selecting means to periodically change in order over the transmitting piezoelectric vibrators and the receiving piezoelectric vibrators, respectively, and determines an optimal combination of the transmitting piezoelectric vibrator and the receiving piezoelectric vibrator assuming a maximum value in signal intensity of an ultrasonic wave. 
     Also, the optimal combination determining means, when a signal intensity of an ultrasonic wave detected by the signal intensity detecting means decreases, causes the switching means and the selecting means to change in order over the transmitting piezoelectric vibrators and the receiving piezoelectric vibrators, respectively, and determines an optimal combination of the transmitting piezoelectric vibrator and the receiving piezoelectric vibrator assuming a maximum value in signal intensity of a ultrasonic wave. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing a basic structure of a pulse wave detecting device; 
     FIGS. 2A and 2B are view for explaining an arrangement of piezoelectric vibrators on a pulse wave probe provided in the pulse wave detecting device; 
     FIGS. 3A to  3 C are view showing a state where the pulse wave detecting device is assembled in a timepiece; 
     FIGS. 4A to  4 C are view for explaining modifications in arrangement of piezoelectric vibrators on a pulse wave probe provided in the pulse wave detecting device; and 
     FIGS. 5A and 5B are view for explaining a conventional pulse wave detecting device. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Preferred embodiments of a pulse wave detecting device of the present invention will now be described with reference to FIG. 1 to FIG.  4 . 
     (1) Outline of Embodiments 
     (i) Scan measurement: 
     By a signal intensity measuring part  123  of a pulse wave detecting device  1000 , any of transmitting piezoelectric vibrators  101 A- 101 D is switched to through a switching part  111  and any of receiving piezoelectric vibrators  102 A- 102 D is selected through a selecting part  121 . 
     This process provides a total of 16 pairs of transmitting piezoelectric vibrator and receiving piezoelectric vibrator. While scanning for all the 16 pairs of transmitting piezoelectric vibrator  101 A- 101 D and receiving piezoelectric vibrator  102 A- 102 D, an ultrasonic wave is transmitted toward an artery through any of the transmitting piezoelectric vibrators  101 A- 101 D and an ultrasonic wave propagating through the artery is received by any of the receiving piezoelectric vibrators  102 A- 102 D. 
     After waveform-detecting the received ultrasonic wave signal by a receiving part  122 , the ultrasonic wave signal thus waveform-detected is supplied to the signal intensity measuring part  123  where it is measured of a signal intensity. The signal intensity measuring part  123  determines, among signal intensities of the totally 16 pairs of transmitting piezoelectric vibrator  101 A- 101 D and receiving piezoelectric vibrator  102 A- 102 D, a pair representing a maximum intensity as an optimal pair for pulse wave detection. 
     (ii) Pulse wave detection measurement: 
     In order to enable transmitting/receiving an ultrasonic wave by the determined optimal pair, the signal intensity measuring part  123  supplies a switch instruction signal to the switching part  111  and a select instruction signal to the selecting part  121 . The pulse detecting device  1000  causes the receiving part  122  to waveform-detect the ultrasonic wave obtained by the optimal pair and then a signal processing part  124  to acquire out of the waveform-detected ultrasonic wave signal a pulse wave signal and pulse frequency to be displayed on a display part of an output part  125 . 
     (2) Detailed Embodiments 
     FIG. 1 shows a block diagram illustrating a basic configuration of a pulse wave detecting device  1000  according to a preferred embodiment. 
     Referring first to FIG.  1  and FIG. 2, various constituent components will be explained of the pulse wave detecting device  1000 . 
     As shown in FIG. 1, the pulse wave detecting device  1000  includes a pulse wave probe  100  having a transmitting transducer  101  and a receiving transducer  102 , a switching part  111 , a driving part  112 , a selecting part  121 , a receiving part  122 , a signal intensity measuring part  123 , a signal processing part  124  and an output part  125 . 
     The transmitting transducer  101  and receiving transducer  102  are arranged on a pulse wave probe substrate  150  with 10 mm in length by 15 mm in width, and are further provided with the following constituent components. 
     The transmitting transducer  101  has four transmitting piezoelectric vibrators  101 A,  101 B,  101 C and  101 D (hereinafter referred to as “transmitting piezoelectric vibrators  101 A- 101 D”) each having a size, of 3 mm in length by 2 mm in width by 200 μm in thickness. The transmitting transducer  101  causes any piezoelectric vibrator switched by the switching part  111  to transmit an amplitude-modulated 32-kHz ultrasonic wave toward an artery. By thus rendering 32 kHz the transmitting frequency from the transmitting transducer  101 , where arranging a pulse wave detecting device  1000  in a timepiece, that frequency is common to a transmitting frequency of the timepiece. Accordingly, a not-shown transmitter of the timepiece is commonly used in a driving circuit of the driving part  112 . Outputting is made after amplification as required. This can reduce the number of parts needed for the pulse wave detecting device  1000 , thus reducing manufacture cost. 
     The receiving transducer  102  has four receiving piezoelectric vibrators  102 A,  102 B,  102 C and  102 D (hereinafter referred to as “receiving piezoelectric vibrators  102 A- 102 D”) each having a size of 3 mm in length by 2 mm in width by 200 μm in thickness. The receiving transducer  102  causes any one of the receiving piezoelectric vibrators  102 A- 102 D selected by the selecting part  121  to receive an ultrasonic wave transmitted from any one of the transmitting piezoelectric vibrators  101 A- 101 D of the transmitting transducer  101  and propagating through a human body including an artery and to supply it to the receiving part  122 . 
     The pulse wave probe  100  is a unit to function as a pulse wave sensor, which has the transmitting transducer  101  and receiving transducer  102  arranged on the common pulse probe substrate  150 . 
     On the pulse wave probe  100 , the transmitting piezoelectric vibrators  101 A- 101 D (or the receiving piezoelectric vibrators  102 A- 102 D) in a row of the pulse wave probe  100  shown in FIG. 1 are set up such that, when conducting pulse wave detection measurement, they are perpendicular to a radial artery, i.e. the transmitting transducer  101  and receiving transducer  102  are put in parallel in a direction of a radial artery blood flow and the transmitting piezoelectric vibrators  101 A- 101 D and receiving piezoelectric vibrators  102 A- 102 D are in contact with a body surface. 
     The arrangement of the receiving piezoelectric vibrators  102 A- 102 D and the transmitting piezoelectric vibrators  101 A- 101 D is further explained with reference to FIGS.  2 . 
     FIG. 2A is a top view of the pulse wave probe  100 . As shown in FIG. 2A, the four transmitting piezoelectric vibrators  101 A- 101 D are arranged at equal intervals in a row form in a lengthwise direction (vertical direction) of the pulse wave probe substrate  150 . The four receiving piezoelectric vibrators  102 A- 102 D are arranged at equal intervals in a row form in parallel with and with a spacing by a constant distance from the lengthwise row of the transmitting piezoelectric vibrators  101 A- 101 D. Furthermore, each pair of the transmitting and receiving piezoelectric vibrators  101 A and  102 A,  101 B and  102 B,  101 C and  102 C and  101 D and  102 D is arranged in a perpendicular direction to the lengthwise direction (horizontal direction) of the pulse wave probe substrate  150 . 
     FIG. 2B is a sectional view of FIG. 2A wherein the transmitting piezoelectric vibrators  101 A- 101 D and the receiving piezoelectric vibrators  102 A- 102 D are arranged on the substrate  150 . As shown in FIG. 2B, the transmitting piezoelectric vibrators  101 A- 101 D and receiving piezoelectric vibrators  102 A- 102 D are fitted in respective depressions formed in the pulse wave probe substrate  150 , and fixed such that the piezoelectric vibrators at top surfaces are substantially in flush with each other. 
     The switching part  111  (FIG. 1) receives a switch instruction signal supplied from the signal intensity measuring part  123  through a signal line a, and switches so that an ultrasonic wave can be transmitted from any of the transmitting piezoelectric vibrators  101 A- 101 D. 
     The driving part  112  has a transmitting source of an oscillator such as of quartz to generate an alternating current at a frequency dependent upon its eigenfrequency, and frequency-divide the same frequency into a 32-kHz high frequency. The driving part  112  drives by the 32-kHz high frequency any of the transmitting piezoelectric vibrators  101 A- 101 D switched by the switching part  111 , thus transmitting an ultrasonic wave. 
     Incidentally, the driving part  112  is driven by turning on a power to the pulse wave detecting device  1000 . The selecting part  121  receives a select instruction signal supplied through a signal line b and selects any of the receiving piezoelectric vibrators  102 A- 102 D. 
     The receiving part  122  waveform-detects the ultrasonic wave received by any of the receiving piezoelectric vibrators  102 A- 102 D and supplies a waveform-detected ultrasonic wave to the signal intensity measuring part  123  and signal processing part  124 . 
     The signal intensity measuring part  123  measures a signal intensity of the ultrasonic wave having been waveform-detected by the receiving part  122  after received by any one of the receiving piezoelectric vibrators  102 A- 102 D, with respect to the ultrasonic wave transmitted from any one of the transmitting piezoelectric vibrators  101 A- 101 D. 
     The signal processing part  124  has a not-shown pulse wave information acquiring part and pulsation count part. This pulsation information acquiring part has a not-shown count part to count a pulse frequency based on a signal supplied from the receiving part  122 . This count part measures a time interval of pulse waves by a predetermined number of times (e.g. three times, five times, seven times, ten times, etc.), and determines a pulse frequency per minutes from a mean time T of rounds of measurements according to the following Equation (1). 
     
       
           V= 60 /T   (1) 
       
     
     Incidentally, there is no limitation to the case where determining a pulse frequency from a mean time T of pulse waves. For example, a pulse count w in a predetermined time t (e.g. 10 seconds) may be detected and a pulse frequency V per minute may be determined according to the following Equation (2). 
     
       
           V=w× (60 /t )  (2) 
       
     
     In the count part, a pulse wave signal is generated that represents a presence of a pulse wave such as a pulse signal on each pulse wave, which is to be supplied together with a determined pulse frequency to the output part  125 . 
     The output part  125  has a not-shown display part to display a pulse frequency and pulse wave signal supplied from the pulsation count part of the signal processing part  124 . The display part is structured by a liquid crystal display to image-display a pulse frequency and pulse wave signal. Alternatively, a pulse frequency may be electrically displayed on a panel. 
     The overall operation of the pulse wave detecting device  1000  will now be explained by separating as (i) scan measurement and (ii) pulse wave detection measurement, with reference to FIG.  1 . 
     (i) Scan measurement 
     By scan measurement explained below, an optimal pair is determined for pulse wave detection which is a combination of any one of the transmitting piezoelectric vibrators  101 A- 101 D and any one of the receiving piezoelectric vibrators  102 A- 102 D. 
     First, the user puts the pulse wave probe  100  on a body surface  5  such that the row of transmitting piezoelectric vibrators  101 A- 101 D (or receiving piezoelectric vibrator  102 A- 102 D) is nearly perpendicular to a radial artery  2  (see FIG.  3 C). 
     Next, the user turns on a power to the pulse wave detecting device  1000 . When turning on a power, the signal intensity measuring part  123  supplies a switch instruction signal for switching to any one of the transmitting piezoelectric vibrators  101 A- 101 D to the switching part  111  via the signal line a. The driving part  112  drives any one of the transmitting piezoelectric vibrators  101 A- 101 D switched by the switching part  111  so that an ultrasonic wave at a frequency of 32 KHz can be transmitted toward an artery  2 . 
     The signal intensity measuring part  123  supplies a switch instruction signal for switching to any one of the transmitting piezoelectric vibrators  101 A- 101 D to the switching part  111 , and then a select instruction signal for selecting one per time of the receiving piezoelectric vibrators  102 A- 102 D to the selecting part  121  via the signal line b. 
     In this manner, the signal intensity measuring part  123  controls to make totally  16  combinations each of any one of the transmitting piezoelectric vibrators  101 A- 101 D and any one of the receiving piezoelectric vibrators  102 A- 102 D, so that scan measurement on signal intensity can be made with using all these pairs. 
     After the receiving part  122  sequentially waveform-detects ultrasonic wave signals respectively supplied through the 16 pairs, the signal intensity measuring part  123  measures intensities of these signals and temporarily stores them to a not-shown memory part. 
     Next, the signal intensity measuring part  123  determines an optimal pair from among the totally 16 pairs of the transmitting piezoelectric vibrators  101 A- 101 D and the receiving piezoelectric vibrators  102 A- 102 D, based on the signal intensity data in temporary storage. 
     In this case, the signal intensity measuring part  123  determines as an optimal pair a maximum pair in value from the temporarily stored signal intensities. 
     Thus, an optimal pair is determined for pulse wave detection by the above operation, ending scan measurement. 
     Incidentally, a desired signal intensity value may be stored in the memory part of the signal intensity measuring part  123  so that an optimal pair can be taken by a closest pair in value to that signal intensity. This can prevent against unnecessary waste of power due to excessive signal intensity for pulse wave detection measurement. 
     Meanwhile, scan measurement may be made at a constant time interval except for a time after turning on a power to the pulse wave detecting device  1000 . Also, where a signal intensity of an optimal pair weakens, scan measurement may be made again to predetermine an optimal pair thereby resuming a measurement. 
     By thus carrying out scan measurement, it is possible to monitor for enabling optimal pulse wave measurement with an optimal pair at all times. 
     (ii) Pulse wave detection measurement 
     Pulse wave measurement as explained below is made by an optimal pair of any one of the transmitting piezoelectric vibrators  101 A- 101 D and any one of the receiving piezoelectric vibrators  102 A- 102 D determined by the above-mentioned scan measurement. 
     First, the signal intensity measuring part  123  supplies a switch instruction signal to the switching part  111  through the signal line a to perform pulse wave detection with the optimal pair as determined in the scan measurement. This provides switching to a transmitting piezoelectric vibrator for the optimal pair (hereinafter referred to as “optimal transmitting piezoelectric vibrator”) of the transmitting piezoelectric vibrators  101 A- 101 D. A selection instruction signal is supplied to the selecting part  121  through the signal line b to select a receiving piezoelectric vibrator for the optimal pair (hereinafter referred to as “optimal receiving piezoelectric vibrator”) of the receiving piezoelectric vibrators  102 A- 102 D. 
     Now the below operation will be described on an assumption that in scan measurement (i) a transmitting piezoelectric vibrator  101 B be determined as an optimal transmitting piezoelectric vibrator and a receiving piezoelectric vibrator  102 C as a optimal receiving vibrator. 
     When starting a pulse wave detection measurement, an ultrasonic wave transmitted from the transmitting piezoelectric vibrator  101 B and propagated through a human body including an artery  2  is received by the receiving piezoelectric vibrator  102 C and supplied bypassing the selecting part  121  to the receiving part  122 . 
     Next, the receiving part  122  waveform-detects the ultrasonic wave received by the receiving piezoelectric vibrator  102 C. 
     The waveform-detected ultrasonic wave by the receiving part  122  is supplied to the signal processing part  124 . Based on this signal, the signal processing part  124  counts a pulse frequency to form a pulse wave signal. 
     The pulse frequency and pulse wave signal counted by the signal processing part  124  are supplied to the output part  125 . The output part  125  displays on the display part the pulse frequency and pulse wave signal supplied from the pulsation count part of the signal processing part  124 . 
     Explanation will now be made on a state of detecting a pulse wave by a pulse wave detecting device  1000  built in a timepiece  200 , with reference to FIG. 3A to FIG.  3 C. 
     The pulse wave detecting device (timepiece)  1000  includes, as shown in FIG. 3A, a timepiece main body  200  and a strap  201 . A pulse wave probe  100  is mounted as a pulse wave sensor on an inner surface of the strap  201 . 
     As shown in FIGS. 3B and 3C, the timepiece  200  is put on a left (or right) wrist  5  with the timepiece main body  200  positioned on a back of the hand similarly to ordinary timepieces. In such a case, the pulse wave probe  100  can be adjusted in position so as to be over a radial artery by moving the pulse wave probe  100  in a lengthwise direction of the strap  201 . The pulse wave probe  100  in its concrete arrangement form was described before and explanation thereof is omitted herein. 
     The timepiece main body  200  is arranged with a switching part  111 , a driving part  112 , a selecting part  121 , a receiving part  122  a signal intensity measuring part  123 , a signal processing part  124  and an output part  125 , besides driving part such as a timepiece movement. 
     The driving part  112  may be used also as a driving circuit used in timepiece function. 
     Incidentally, the pulsation sensor  1000  and the timepiece main body  200  are connected by not-shown wiring built in the strap  201 . 
     The timepiece main body  200  has a display surface (dial) having a timepiece display part  250  to display a time (day, day of the week, etc.) as a timepiece, and a display part  260  having a not-shown pulse frequency display part to display a pulse frequency and a not-shown pulse wave display part. 
     The signal processing part  124  has a pulse wave measuring part which supplies a pulse signal to the display part  260  each time detecting a pulse waveform peak. In response to the pulse signal, the pulse wave display part flickers in green. Seeing a flicker on the pulse wave display part  260 , a user can visually recognize his or her pulse wave. 
     Incidentally, the flicker color of the pulse wave display part  260  may be changed depending on a pulse frequency, e.g. a pulse frequency of  69  and lower is represented by yellow flicker,  70  to  90  by blue flicker,  91  to  110  by green flicker,  111  to  130  by orange flicker, and  131  and higher by red flicker. The flickering color on the pulse wave display part  260 , if changed in this manner, facilitates to distinguish a current pulse wave state. 
     (3) Modifications 
     The invention is not limited to the embodiments, and can adopt various modifications within the scope thereof as given below. 
     Note that in the below modifications explanations are centered on the modifications with the same constituent parts as those explained in the embodiments omitted to explain. 
     (a) First Modification 
     In the preferred embodiments as shown in FIG.  2 A and FIG. 3C, where the pulse wave probe  100  is rested over a radial artery, the transmitting piezoelectric vibrators  101 A- 101 D and the receiving piezoelectric vibrators  102 A- 102 D were formed on the pulse wave substrate  150  such that any of the transmitting piezoelectric vibrators  101 A- 101 D is positioned downstream (or upstream) the artery blood flow and any of the receiving piezoelectric vibrators  102 A- 102 D upstream (or downstream) an artery  2 . 
     On the contrary, in this first modification, as shown in FIG. 4A transmitting piezoelectric vibrators  101 A′- 101 D′ and receiving piezoelectric vibrators  102 A′- 102 D′ are formed on a pulse wave substrate  150  such that they are to be alternately positioned checkerwise at the upstream and downstream of the artery blood flow. 
     According to the first modification, proper pulse wave detection is possible even where for example there is no artery in an line form along a radius. 
     (b) Second Modification 
     In the preferred embodiment, as shown in FIG. 2B the four transmitting piezoelectric vibrators  101 A- 101 D of the transmitting transducer  101  and the four receiving piezoelectric vibrators  102 A- 102 D of the receiving transducer  102  are fitted in depressions formed from a top surface toward a backside of the pulse wave probe substrate  150  so that the piezoelectric vibrators are fixed substantially flush at their top surfaces with each other. 
     On the contrary, in this second modification, as shown in FIG.  4 B and FIG. 4C a V-formed groove is formed lengthwise in the substrate from one edge portion to the other edge portion on the top surface thereof so that the piezoelectric vibrators are fixed slant on slopes of the groove. 
     According to the second modification, the receiving piezoelectric vibrators are easy to receive a ultrasonic wave transmitted from the transmitting piezoelectric vibrator and reflected back by the blood flowing through an artery. 
     (c) Third Modification 
     The sectional structure of the pulse wave probe of the first modification may adopt a structure of FIG. 4B or FIG. 4C of the second modification, besides the structure of FIG. 2B of the preferred embodiment. 
     Similarly, the sectional structure of the pulse wave probe  100  in FIG. 2A of the preferred embodiment may adopt a structure of FIG. 4B or FIG. 4C of the second modification, besides the structure of FIG. 2B of the preferred embodiment. 
     (d) Fourth Embodiment 
     In the above examples, explanations were made on the embodiments of the pulse wave count part that transmits a ultrasonic wave at 32-kHz frequency toward an artery to detect a pulsation from a ultrasonic wave signal attenuated and amplitude-modulated by a blood flow. 
     However, the piezoelectric vibrators  101 A- 101 D of the transmitting transducer  101  is not limited in transmitting frequency to 32 kHz but can transmit a ultrasonic wave at an arbitrary frequency, i.e. selectable in a range of 20 kHz to 50 kHz, preferably 30 kHz to 40 kHz. Meanwhile, where the timepiece adopts another transmitting frequency m it is possible to use the same frequency m. 
     Meanwhile, pulsation detection may be made from an ultrasonic wave signal that is modulated in frequency by the Doppler effect caused due to a velocity of blood flow through an artery in place of using the pulse wave count part for detecting pulsation from an ultrasonic wave signal modulated of amplitude by artery blood flow. In such a case, an ultrasonic wave is transmitted at a higher frequency of about 10 MHz in order to cause the transmitted ultrasonic wave to be reflected upon the blood flowing through an artery. Thus, a pulse wave count part can be available that detects pulsation from a Doppler shift amount (frequency shift amount) in a received ultrasonic wave. 
     According to the present invention, the pulse wave probe can be automatically positioned in an optimal position when wearing the pulse wave detecting device. 
     Also, according to the invention, even if the pulse wave probe is deviated in position after wearing the pulse wave detecting device, the pulse wave probe can be newly, automatically positioned to an optimal position.