Pulse wave detecting device and pulse measurer

The present invention relates to a pulse wave detecting device for detecting pulse waves, and to a pulse measurer employing this pulse wave detecting device. The present invention addresses the problem of obtaining a pulse wave signal in which the noise components have been suitably removed from a pulse waveform, and of determining the pulse rate with high accuracy based on this pulse wave signal. The method for deriving the pulse wave signal and pulse rate is as follows. The pulse wave signal from pulse wave detecting sensor unit (30) is temporarily stored in buffer (503). When impulse noise is detected in the pulse wave signal in buffer (503) by impulse noise detecting means (505), the band pass for first digital filter (506) becomes a hill-shaped curve centered on the frequency corresponding to the preceding pulse rate, and impulse noise in the pulse wave signal output from buffer (503) is decreased. Thereafter, overall noise and body movement components are decreased in the pulse wave signal by means of second digital filter (507) and third digital filter (508). The signal is then subjected to frequency analysis by frequency analyzer (509), and the pulse rate is calculated from the results of this analysis.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a pulse wave detecting device for 
detecting pulse waves, and to a pulse measurer employing the 
aforementioned pulse wave detecting device. 
2. Description of the Related Art 
Pulse measurers which detect pulse waves, calculate the pulse rate, and 
then notify the user of the calculated result have been commercially 
available for some time. This type of pulse measurer calculates the pulse 
rate using the signals (pulse wave signals) output from a pulse wave 
detecting sensor that is disposed near a site on the user's body where the 
pulse measurement is to be made. Known methods for calculating the pulse 
rate include the rectangular wave processing method and frequency analysis 
method described below. 
(A) Rectangular wave processing method 
In the rectangular wave processing method, the pulse wave signal is 
converted to a rectangular wave, and the pulse rate is calculated by 
measuring the period of the rectangular wave (the pulse rate is 
proportional to the reciprocal of the period). In other words, the pulse 
rate can be calculated by investigating the variation in the level of the 
pulse wave signal over a time domain. Thus, this method enables 
calculation of the pulse rate by only a small amount of calculations and a 
small-scale circuit structure. 
(B) Frequency analysis method 
In the frequency analysis method, the pulse wave signal is subjected to 
frequency analysis, the spectral line having a maximal level is extracted 
from the spectrum obtained as a result of the frequency analysis, and the 
pulse rate is calculated from the frequency of this spectral line. In 
other words, the pulse rate is calculated by comparing the levels of the 
pulse wave signals within a frequency domain. FFT is typically employed as 
the frequency analysis method. 
However, in addition to the pulse wave components, other noise may be 
superimposed on the output from the pulse wave detecting sensor. Since 
this superimposed noise is not necessarily regular, merely providing an 
analog filter at the input stage does not sufficiently remove its effects. 
Accordingly, the present inventors have proposed the following processes 
(1) through (3) for reducing such noise. 
(1) Impulse noise removal processing 
As used here, impulse noise is the general term for noise which is 
generated suddenly. An example of a pulse wave signal containing 
superimposed impulse noise is shown in FIG. 11. FIG. 11(a) shows the pulse 
wave signal in the time domain, while FIG. 11(b) shows the spectrum 
obtained after performing an FFT on this pulse wave signal. As is clear 
from the figures, due to the superimposition of impulse noise, the pulse 
wave signal is extremely deformed over the time period t1.about.t2 in FIG. 
11(a), and a spectral line is present which is higher than spectral line 
SP which shows the fundamental wave of the pulse wave. As described above, 
in the frequency analysis method, the pulse rate is calculated based on 
the highest level spectral line. Thus, since frequency analysis is 
performed on the pulse wave signal containing the superimposed impulse 
noise as shown in the figure, it is not possible to accurately calculate 
the pulse rate. 
Therefore, the present inventors proposed a device which monitors for the 
presence or absence of phenomena which cause impulse noise to be 
generated, and when, based on the results of this monitoring, there is a 
concern that impulse noise may be superimposed, performs frequency 
analysis after inserting a dummy signal in the interval containing the 
impulse noise in the pulse signal (for example, time period t1.about.t2 in 
FIG. 11(a)) (for details, see specification and figures accompanying 
Japanese Patent Application No. 273238 of 1995: Japanese Patent First 
Publication No. 113653 of 1997). In this device, because a dummy signal 
having a value of 0 is inserted in the time interval t1.about.t2 in which 
the impulse noise is superimposed, spectral line SP, which expresses the 
fundamental wave of the pulse wave, becomes the highest level spectral 
line in the spectrum obtained as a result of FFT processing. Note that, as 
is clear from FIGS. 12(a) and 12(b), the above-described device is 
premised on the use of frequency analysis. 
(2) Window processing 
Typically, the change in the pulse wave (pulse rate) is continuous, with 
there being only a slight chance of a large deviation from the previously 
detected value. Window processing is processing which takes advantage of 
this fact to set a suitable range (window) for the current detection value 
by multiplying the value detected previously by a fixed coefficient and, 
when a detected value outside the range is obtained, which removes this 
value as an anomalous value resulting from noise. When there is poor 
following of the pulse rate by the window, then, if the pulse rate changes 
abruptly such as at the start of exercise (t1) or the like, the pulse rate 
cannot be followed, as shown in FIG. 13. As a result, a phenomenon occurs 
in which even if the detected value is a normal value, it is removed as an 
anomalous value. Moreover, this phenomenon continues until the window is 
correctly revised. The present inventors have therefore proposed a 
technique for improving the window's ability to follow the pulse rate (for 
details, see specification and figures accompanying Japanese Patent 
Application No. 24511 of 1996: Japanese Patent Application First 
Publication No. 154825 of 1997). 
(3) Processing to remove body motion component 
As explained above, the pulse wave detection sensor is typically disposed 
near the site on the user's body where measurements are to be made. 
Accordingly, when the user is exercising, a body motion component is 
superimposed on the pulse wave signal. An example of the spectrum obtained 
from performing FFT on a pulse wave signal containing a superimposed body 
motion component is shown in FIG. 14(a). In the example shown in this 
figure, the spectral lines on the left are the pulse wave components, 
while the spectral lines on the right are the body motion components. The 
spectral lines of both these groups are of approximately the same level. 
Of course, FIG. 14(a) is merely one example, and a situation is also 
possible in which the highest level spectral line is present among the 
spectral lines for the body motion component. Accordingly, if frequency 
analysis is carried out on a pulse wave signal containing a superimposed 
body motion component, the correct pulse rate cannot be calculated. 
Therefore, the present inventors proposed a device comprising a body motion 
detecting sensor which subtracts the spectrum (14(b)) obtained by 
performing FFT on the signal (i.e., the body motion signal) output from 
the body motion detecting sensor from the spectrum shown in FIG. 14(a), 
and then selects the highest level spectral line after obtaining a 
spectrum that consists of only pulse wave components such shown in FIG. 
14(c) (for details, see Japanese Patent Application No. 227338 of 1995). 
As is clear from this figure, by means of this device, the selected 
spectral line is spectral line SP which expresses the fundamental wave of 
the pulse wave. The device described here is premised on the use of 
frequency analysis, as should be clear from the fact that spectrum 
subtraction is carried out. 
In the impulse noise removal processing described under (1) above, 
phenomenon causing impulse noise, for example, features employed in a 
wristwatch like a flashing back light or a sounding alarm, are set in 
advance, and a dummy signal is inserted in the pulse wave signal at the 
time which has been set for the occurrence of these phenomenon. However, 
general impulse noise may also occur which is not related to the internal 
state of the device itself, making it extremely difficult to detect all 
these phenomena. On the other hand, if the device is designed so that a 
dummy signal is inserted regardless of the generation of such phenomenon, 
then it is possible to completely remove the impulse noise. However, the 
essential pulse wave components are also removed entirely. In other words, 
removal of all the impulse noise while having only a minimal effect on the 
essential pulse wave components is extremely difficult to accomplish by 
means of the only the processing described in (1) above. 
Moreover, in the case of the window processing described under (2) above, 
values detected outside the window are removed, so that when changes in 
the window cannot follow changes in the pulse wave (when an arrhythmia has 
occurred for example), an accurately detected value is removed as an 
anomalous value. 
Finally, in the body motion component removal processing described under 
(3) above, spectrum subtraction is carried out. However, because the body 
motion components (on the left in FIG. 14(a)) in the output from the pulse 
wave detecting sensor, and the body motion components (FIG. 14(b)) in the 
output from the body motion detecting sensor do not in fact completely 
coincide, it is not possible to completely remove the body motion 
component by subtracting the latter from the former. 
SUMMARY OF THE INVENTION 
The present invention was conceived in consideration of the above-described 
circumstance, and has as its first objective the provision of a pulse wave 
detecting device capable of obtaining a pulse wave signal in which the 
noise component has been appropriately removed from the pulse waveform. 
The present invention further has as a second objective the provision of a 
pulse measurer capable of determining the pulse rate with high accuracy by 
employing the aforementioned pulse wave detecting device. 
In order to resolve the above-described problems, a first construction of 
the present invention's pulse wave detecting device is provided with a 
pulse wave detecting sensor for detecting pulse waves and outputting pulse 
wave signals; a filter having variable characteristics for filtering the 
pulse wave signal output from said pulse wave detecting sensor and 
outputting the result; a pulse rate calculating means for calculating the 
pulse rate based on the pulse wave signal which was filtered by said 
filter; and a characteristics setting means for setting characteristics of 
said filter based on the pulse rate calculated by said pulse rate 
calculating means; wherein the characteristics are set in response to the 
pulse rate calculated based on said filtered pulse wave signal. 
Accordingly, it is possible to reduce non-pulse wave components in said 
filtered pulse wave signal, so that the pulse wave can be detected with 
even higher accuracy. 
The first structure as described above is provided with a buffer for 
temporarily storing the pulse wave signal output from said pulse wave 
sensor and then outputting it to said filter; and an impulse noise 
detecting means for detecting impulse noise from the pulse wave signal 
that was temporarily stored in said buffer. The characteristics setting 
means may be designed to set the characteristics of said filter after 
taking into account the results of detection by said impulse noise 
detecting means. In this case, for example, said filter carries out 
selective filtering of the pulse wave signal in which said impulse noise 
detecting means detected impulse noise, so that the impulse noise 
component is reduced or removed without any large reduction or removal of 
the essential pulse wave components. 
In the above-described first construction, it is also possible to construct 
said filter so that a level at which the pulse wave signal passes through 
said filter gradually becomes lower from a reference frequency to the 
lower and upper limit frequencies of the fundamental wave of the pulse 
wave, and to set characteristics of said filter by having said 
characteristics setting means set the reference frequency. In this case, 
it is possible to reduce the overall noise components without greatly 
reducing or removing the essential pulse wave components. Note that the 
reference frequency is the frequency complying with the preceding pulse 
rate. 
In each of the above-described constructions, it is also possible to design 
said characteristics setting means so that the characteristics set in said 
filter are changed in response to the state of change in the pulse rated 
calculated by said pulse rate calculating means. In this case, it is 
possible to detect the pulse wave with even greater accuracy. 
In addition, it is also acceptable to provide a notifying means for 
notifying the user of the pulse rate calculated by said pulse rate 
calculating means to each of the pulse wave detecting devices described 
above. As a result, it becomes possible to realize a pulse measurer which 
measures the pulse rate at high accuracy. 
In order to resolve the problems described above, a second construction of 
the present invention's pulse wave detecting device is provided with a 
pulse wave detecting sensor for detecting the pulse wave and outputting 
pulse wave signals; a filter having variable characteristics for filtering 
the pulse wave signal output from said pulse wave detecting sensor and 
outputting the result; a body motion detecting sensor for detecting body 
motion and outputting a body motion signal; a pitch calculating means for 
calculating a pitch of the body motion based on the body motion signal 
output from said body motion detecting sensor; and a characteristics 
setting means for setting characteristics of said filter based on the 
pitch calculated by said pitch calculating means; wherein characteristics 
are set in said filter in response to the pitch of body motion calculated 
based on the body motion signal output from said body motion detecting 
sensor. Accordingly, it is possible to reduce noise components due to body 
motion in the filtered pulse wave signal, so that it becomes possible to 
detect the pulse wave with even greater accuracy. 
In the second construction described above, said characteristics setting 
means may be designed so that the characteristic set in said filter are 
changed in response to the state of change in the pitch calculated by said 
pitch calculating means. In this case, it is possible to detect the pulse 
wave with even higher accuracy. 
In addition, by providing pulse wave detecting devices of the constructions 
described above with a pulse rate calculating means for calculating the 
pulse rate based on the pulse wave signal filtered by said filter, and a 
notifying means for notifying the user of the pulse rate calculated by 
said pulse rate calculating means, it is possible to realize a pulse 
measurer which measures the pulse rate with a high degree of accuracy.

PREFERRED EMBODIMENTS OF THE PRESENT INVENTION 
Embodiments of the present invention will now be explained with reference 
to the accompanying figures. Note that the pulse measurer according to 
these embodiments is provided with the functions of a regular digital 
wristwatch, and is employed by switching between a watch mode and a pulse 
measurer mode. 
A: STRUCTURE OF EMBODIMENT 
A-1: Overall Structure 
FIG. 1 shows the state of attachment of the pulse measurer, with the device 
roughly comprised of a device main body 10 having a wristwatch structure, 
a cable 20 connected to device main body 10, and a sensor unit 30 (pulse 
wave detecting sensor) provided to the end of cable 20. A wristband 12 is 
attached to device main body 10 which wraps around the user's wrist from 
the 12 o'clock position and affixes at the 6 o'clock position of the 
wristwatch. Device main body 10 can be freely attached and removed from 
the user's wrist by means of this wristband 12. Pulse wave detecting 
sensor unit 30 is blocked from light by band 40 employed for fixing the 
sensor in place, and is attached at the base of the user's index finger. 
By attaching pulse wave detecting sensor unit 30 in this way to the base 
of the finger, not only is cable 20 made shorter so that it does not 
present interference to the user during exercise, but the influence of the 
outside environment can also be reduced. 
A-2: Structure of the Main Body of the Pulse Measurer 
FIG. 2 is a planar view showing the state of the main body of the pulse 
measurer when the wristband or cable is released. FIG. 3 is side view 
showing the pulse measurer from the 3 o'clock direction. In FIG. 2, device 
main body 10 is provided with a watch case 11 (main body case) made of a 
resin. A liquid crystal display device 13 (display means) is provided to 
the surface of watch case 11 for displaying the current time and date, as 
well as the pulse rate and other pulse wave information. LCD device 13 is 
provided with first, second, and third segment display regions 131-133, 
respectively, and a dot display region 134. First segment display region 
131 is positioned at the upper left area of the display panel; second 
segment display region 132 is positioned at the upper right area of the 
display panel; third segment display region 133 is positioned at the lower 
right area of the display panel; and dot display region 134 is positioned 
at the lower left area of the display panel. Graphic display of various 
information can be carried out on dot display region 134. 
A controller 5 for carrying out control of the display device and signal 
processing on the detected signal is provided inside watch case 11, so 
that the display of changes in the pulse rate based on the results 
detected by pulse wave detecting sensor unit 30 can be displayed on LCD 
device 13. A watch circuit is formed in controller 5 so that the display 
of ordinary time, lap times or split times is possible on LCD device 13. 
Button switches 111.about.117 are provided to the outer periphery and 
surface of watch case 11, for carrying out external manipulations such as 
setting the time, switching the mode, or initiating measurement of lap 
time or pulse wave information. 
The electrical source for a pulse measurer 1 of the type which attaches to 
the arm is a button-shaped battery 59 housed in watch case 11. Cable 20 
supplies electric power from battery 59 to pulse wave detecting sensor 
unit 30, and inputs the results detected by sensor unit 30 to controller 5 
in watch case 11. In order to ensure the wrist's freedom of movement and 
to protect the palm of the user's hand in the event of a fall, device main 
body 10 is enlarged in the 3 o'clock to 9 o'clock direction, with a large 
overhang 101 being further provided to the wristwatch in the 9 o'clock 
direction thereof. In addition, wristband 12 is connected at a position 
which is shifted toward the 3 o'clock side of the watch. 
A flat piezo element 58 used as a buzzer (or used for producing informative 
sound) is disposed inside the watch case 11, at the 9 o'clock position 
with respect to the battery 59. Battery 59 is heavier than piezo element 
58, such that the position of the center of gravity in the device main 
body 10 shifts toward the 3 o'clock side. Moreover, wrist band 12 is 
connected to the side of the main body 10 toward which the weight center 
has shifted. As a result, device main body 10 can be attached to the arm 
in a stable manner. Further, since battery 59 and piezo element 58 are 
disposed in the planar direction, device main body 10 may be made thinner. 
By providing a battery cover 118 to the rear surface 119 of the wrist 
watch, the user can easily change the battery 59. 
A-3: Structure of Attachment of Pulse Measurer Main Body to Arm 
In FIG. 3, a coupler 105 for holding a push pin 121 attached to the end of 
wristband 12 is formed at the 12 o'clock direction on watch case 11. At 
the 6 o'clock direction of watch case 11, wristband 12 wrapped around the 
arm is folded back at an intermediate point along its length, and a 
receiving member 106 to which stopper 122 attaches for holding at this 
intermediate position is formed. 
At the 6 o'clock direction of device main body 10, a portion extending from 
the rear surface 119 to receiving member 106 forms a rotation stopping 
member 108 which is formed in a unitary manner with watch case 11 and 
forms an approximately 115.degree. angle with rear surface 119. In other 
words, when device main body 10 is attached by means of wrist band 12 so 
as to be positioned on the supper surface L1 (on the palm side of the 
hand) of right wrist L (arm), then rear surface 119 of watch case 11 
adheres to upper surface L1 of wrist L, while rotation stopping member 108 
comes in contact with side surface L2 where the radius is present. In this 
arrangement, rear surface 119 of main body 10 straddles radius R and ulna 
U, while the portion extending from bent part 109 of rotation stopping 
member 108 and rear surface 119 to rotation stopping member 108 comes in 
contact with radius R. Because rotation stopping member 108 and rear 
surface 119 anatomically form a theoretical angle of about 115.degree., 
even if the user rotates device main body 10 in the direction of arrow A, 
or in the direction of arrow B, main body 10 does not deviate 
unnecessarily from its current state. In addition, since the rotation of 
device main body 10 is controlled by just two sites on either side of the 
arm through rear surface 119 and rotation stopping member 108, rear 
surface 119 and rotation stopping member 108 come in contact with the arm 
with surety even in the case of a thin arm. Thus, the effect of stopping 
rotation is obtained with certainty, while there is no pinching sensation 
even in the case of a thicker arm. 
A-4: Structure of Pulse Wave Detecting Sensor Unit 
FIG. 4 is a cross-sectional view of the pulse wave detecting sensor unit in 
this embodiment. In the pulse wave detecting sensor unit 30 in FIG. 4, a 
component housing space 300 is formed therein by means of applying a cover 
302 to the rear side of sensor frame 36 for the case body. Circuit board 
35 is disposed inside this component housing space 300. LED 31, 
phototransistor 32, and other electronic parts are mounted on circuit 
board 35. The end of cable 20 is fixed in place at pulse wave detecting 
sensor unit 30 by a bush 393. Each of the wires of cable 20 are soldered 
onto the pattern of each of circuit boards 35. Pulse wave detecting sensor 
unit 30 is attached to the finger so that cable 20 is pulled out from the 
base of the finger to the side of device main body 10. Accordingly, LED 31 
and photo transistor 32 are disposed so as to lie along the direction of 
the length of the finger. LED 31 is positioned on the side toward the tip 
of the finger, while photo transistor 32 is positioned at the base of the 
finger. As a result, light from the outside environment does not readily 
reach photo transistor 32. 
In pulse wave detecting sensor unit 30, a light transmitting window is 
formed in the upper portion of sensor frame 36 (i.e., the area of actual 
pulse wave signal detection) by means of a light transmitting plate 34 
consisting of a glass plate. The light emitting surface of LED 31 and the 
light receiving surface of photo transistor 32 are oriented in the 
direction of light transmitting plate 34. For this reason, when the 
surface of the finger adheres to the outer surface 341 (contact surface 
with finger surface/sensor surface) of light transmitting plate 34, LED 31 
is positioned to emit light toward the finger surface, while photo 
transistor 32 is positioned to receive the light from LED 31 which has 
reflected off the surface of the finger. In order to improve the adherence 
between the outer surface 341 of light transmitting plate 34 and the 
surface of the finger, outer surface 341 of light transmitting plate 34 is 
formed so as to project out from the peripheral portion 361 thereof. 
This embodiment employs a InGaN-type (indium-gallium-nitrogen) blue LED for 
LED 31. The generated light spectrum of a blue LED has a peak at 450 nm, 
for example, with the generated light wavelength region being in the range 
of 350 to 600 nm. In this case, a GaAsP-type (gallium-arsenic-phosphorous) 
photo transistor may be used for photo transistor 32 corresponding to LED 
31 having the light emitting characteristics described above. The 
wavelength region of the received light of the photo transistor has, for 
example, a main sensitive region in the range of 300 to 600 nm, with a 
sensitive region also present below 300 nm. 
A pulse wave detecting sensor unit 30 of this design is attached to the 
base of the finger using a sensor affixing pad 40. When, in this 
arrangement, light from LED 31 irradiates the finger, the light reaches 
the blood vessels where a portion thereof is absorbed by the hemoglobin in 
the blood. Light reflected from the finger (blood vessels) is received at 
photo transistor 32. Changes in the received light correspond to changes 
in the blood pressure (i.e., pulse waves in the blood). In other words, 
when the blood volume is great, there is weaker reflection of the light, 
while when the blood volume is small, there is stronger reflection of the 
light. Thus, it is possible to measure the pulse rate by detecting changes 
in the intensity of the reflected light. 
This embodiment employed an LED 31 having a light generating region in the 
range of 350 to 600 nm, and a photo transistor 32 having a light receiving 
region in the range of 300 to 600 nm. Pulse wave information is expressed 
based on the results of detection in the overlapping wavelength region 
from 300 nm to 600 nm, i.e., in the wave length region that is below about 
700 nm. If the above-described pulse wave detecting sensor unit 30 is 
employed, then, even if outside light strikes the exposed portion of the 
finger, light included in the outside light that is below 700 nm will not 
reach photo transistor 32 (receiving member) by employing the finger as a 
waveguide. Light in the wavelength region below 700 nm that is included in 
the outside light tends to have a difficult time passing through the 
finger, so that even if the portion of the finger not covered by sensor 
fixing pad 40 is irradiated with outside light, the light does not reach 
photo transistor 32 by passing through the finger as indicated by dashed 
line X. Moreover, the hemoglobin in blood has a large absorption 
coefficient with respect to light having a wavelength in the range of 300 
nm to 700 nm, so that if light in a wavelength region of less than 700 nm 
is employed, it is possible to obtain a pulse wave signal having a high 
S/N ratio. 
A-5: Structure of Connection Between Pulse Measurer Main Body and Pulse 
Wave Detecting Sensor Unit 
A connector 70 is provided at the 6 o'clock position to the surface of the 
portion of device main body 10 which extends as rotation stopping member 
108. Connector piece 80, which is provided to an end of cable 20, is 
attached to connector 70 so as to be freely releasable. By releasing 
connector piece 80 from connector 70, pulse measurer 1 may be used as a 
regular wristwatch or stopwatch (in which case, a specific connector cover 
is attached to protect connector 70). 
A-6: Structure of Controller 
The structure of controller 5 of pulse measurer 1 will now be explained. 
However, since those parts relating to watch functions are well-known, an 
explanation thereof will be omitted, and only those parts relating to the 
pulse measuring functions will be explained here. 
FIG. 5 is a block diagram showing the structure of the main parts of a 
controller 5 which is formed inside the main body of the pulse measurer. 
As shown in this figure, a body motion detecting sensor 101, such as an 
acceleration sensor or the like, is provided inside the main body of the 
pulse measurer. Controller 5 is provided with a design for determining the 
pulse rate and pitch of movement based on the results (body motion signal) 
detected by body motion detecting sensor 101 and the results (pulse wave 
signal) detected by pulse wave detecting sensor 30. 
In controller 5, 501 is a pulse wave signal amplifying circuit for 
amplifying and outputting the detection results (pulse wave signal) from 
pulse wave detecting sensor unit 30; 502 is an A/D converter for 
converting the output (analog voltage signal) from pulse wave signal 
amplifying circuit 501 to a specific bit digital signal (-127.about.127, 
for example), and outputting this result; and 503 is a buffer for 
temporarily storing the output from A/D converter 502, and then outputting 
it. The capacity of buffer 503 is suitably set in correspondence with the 
duration of detection (for example, 16 seconds) during frequency analysis 
in the following step. Here, detection values corresponding to 4 seconds 
can be stored. Detected values corresponding to 4 seconds in buffer 503 
are output immediately after the end of the processing to detect impulse 
noise, which will be discussed below. Thus, these 4 seconds have almost no 
effect on the device's overall delay time. 
505 is an impulse noise detecting means. Impulse noise detecting means 505 
determines whether or not the detected values that are stored in buffer 
503 are being effected by impulse noise, and outputs the result of this 
determination. The method for making the aforementioned determination may 
be optionally selected. In this embodiment, a method is employed in which 
a "1" is output when the proportion of values detected outside a specific 
range with respect to the number of values detected overall in buffer 503 
exceeds a specific threshold value, while a "0" is output in all other 
cases. 
506.about.508 are first through third digital filters which sequentially 
carry out impulse noise removal processing, pseudo-window processing, and 
body movement component removal processing on the pulse wave signal output 
from buffer 503. A FIR filter is optimally employed for each of the 
digital filters, for example. The specifics of processing by each of the 
digital filters will be explained below. 509 is a frequency analyzer which 
performs frequency analysis (FFT processing, for example) on the pulse 
wave signal output from third digital filter 508, and outputs this result 
(spectrum). Although not shown in the figures, the pulse wave signal from 
digital filter 508 is provided with a recording means which is capable of 
recording a specific detection duration only (16 seconds, for example). 
510 is a body motion signal amplifying circuit which amplifies the results 
(body motion signal) detected by body motion detecting sensor 101, and 
outputs this result. 511 is an A/D converter which converts the output 
(analog voltage signal) from body motion signal amplifying circuit 510 to 
a specific bit digital signal (-127.about.127, for example). 512 is a 
buffer for temporarily storing the output from A/D converter 511 and then 
outputting it. Buffer 512 has the same capacity as buffer 503. 
513 is a frequency analyzer having the same structure as frequency analyzer 
509. Frequency analyzer 513 carries out frequency analysis (FFT 
processing, for example) on the body motion signal output from buffer 512, 
and outputs this result (spectrum). Typically, the recording means for 
each of frequency analyzers 509 and 513 are provided in the same memory 
(RAM, for example). 
514 is a pulse wave rectangular wave processing means which converts the 
pulse wave signal from the pulse wave signal amplifying circuit 501 to a 
rectangular wave, and outputs this result. 515 is a body motion signal 
detecting means which outputs the body motion detecting signal when the 
amplitude of the body motion signal from body motion signal amplifying 
circuit 510 exceeds a specific value (50 [mV] for example). 516 is a pulse 
wave-body motion component extracting means which extracts the frequency 
corresponding to the pulse and the frequency corresponding to the pitch of 
the body motion from the results output from each of frequency analyzers 
509 and 513. 517 is a calculation method switching means for inputting the 
rectangular wave signal from pulse wave rectangular wave processing means 
514 and each of the frequencies from pulse wave-body motion component 
extracting means 516, outputting a signal for calculating the pulse rate 
and the pitch, and then switching the signal output to the following step 
based on the body motion detection signal from body motion signal 
detecting means 515. An explanation of the processing for determining the 
frequency (frequency of the fundamental wave of body motion) with respect 
to the body motion pitch will be covered under the explanation of the 
device's operations. 
When calculation method switching means 517 receives a body motion absent 
signal from body motion signal detecting means 515, it outputs to the 
following step the rectangular wave signal from pulse wave rectangular 
wave processing means 514 and the frequency corresponding to the pitch of 
body motion which was extracted by the pulse wave-body motion component 
extracting means 516, and stops the operation of A/D converter 502, buffer 
503, impulse noise detecting means 505, first through third digital 
filters 506.about.508, and frequency analyzer 509. On the other hand, when 
calculation method switching means 517 receives a body motion present 
signal from body motion signal detecting means 515, it initiates operation 
of A/D converter 502, buffer 503, impulse noise detecting means 505, first 
through third digital filters 506.about.508, and frequency analyzer 509, 
and outputs each of the frequencies from pulse wave-body motion component 
extracting means 516 to the following step. 
518 is a pulse rate calculating means which calculates the pulse rate based 
on the rectangular wave signal or frequency of the fundamental wave of the 
pulse wave supplied via calculation method switching means 517. 519 is a 
pitch calculating means for calculating the pitch of body motion based on 
the frequency of the fundamental wave of body motion supplied via 
calculation method switching means 517. Each of pulse rate calculating 
means 518 and pitch calculating means 519 supply the calculated pulse 
rate/pitch to LCD device 13. The calculation of the pulse rate/pitch from 
the frequency is realized by multiplying the frequency by the constant 
"60", while the calculation of the pulse rate/pitch from the rectangular 
wave signal is realized by measuring the period of the rectangular wave, 
and then multiplying the inverse of the measured value by the constant 
"60". 
520 is a first coefficient calculating means (characteristics setting 
means) for calculating and outputting the coefficient set in first digital 
filter 506 based on the result (pulse rate) calculated by pulse rate 
calculating means 518. The characteristics of first digital filter 506 are 
expressed by the coefficient calculated by first coefficient calculating 
means 520 only when the result of the determination by impulse noise 
detecting means 505 is "1", i.e., only when impulse noise has been 
detected. In all other cases, the characteristics are such that all bands 
are through. The coefficient output by first coefficient calculating means 
520 includes a frequency fb1 which becomes the reference (reference 
frequency), and cut-off frequencies f1, fh. Reference frequency fb1 is 
calculated based on the pulse rate detected immediately previously, while 
cut-off frequencies f1, fh are set in response to the change in the pulse 
rate. For example, if the change in the pulse rate is large and the 
stability of pulse transition is low, then cut-off frequencies f1, fh are 
set so that the interval with reference frequency fb1 becomes wider. 
Conversely, if the change in the pulse rate is small and the stability of 
pulse transition is high, then cut-off frequencies f1, fh are set so that 
the interval with reference frequency fb1 becomes more narrow. Note that 
an arrangement is also possible in which cut-off frequencies f1, fh are 
set so that the interval with reference frequency fb1 becomes constant. 
An example of the characteristics of the first digital filter which is 
specified by the coefficient value output by first coefficient calculating 
means 520 is shown in FIG. 6(a). As shown in this figure, the 
characteristics which are set in first digital filter 506 when impulse 
noise is detected by impulse detecting means 505 form a hill-shaped curve, 
the highest point of which is the level at which reference frequency fb1 
passes through the filter. Namely, the damping factor of the signal input 
to first digital filter 506 falls in the vicinity of reference frequency 
fb1 in the frequency domain. As the distance from reference frequency fb1 
increases, the damping factor increases, until it exceeds cut-off 
frequency f1, fh beyond some given distance, and the signal is cut-off. 
In this embodiment, when the reference frequency fb1 is 2.3 [Hz], i.e., 
when the pulse rate through the immediately preceding point in time is 140 
[beats/sec], the value output from first digital filter 506 at the time of 
detection of impulse noise is set so as to be the weighted average value 
of 5 sampling points: 
EQU X.sub.N =(-1.multidot.X.sub.N -1.multidot.X.sub.N+1 +4.multidot.X.sub.N+2 
-1.multidot.X.sub.N+3 -1.multidot.X.sub.N+4)/8 
(N=0,1,2,3,4, . . . ,N-1) 
521 is a second coefficient calculating means which calculates the 
coefficient set in second digital filter 507 based on the results (pulse 
rate) calculated at pulse rate calculating means 518, and outputs this 
result. Without exception, the characteristics of second digital filter 
507 are the characteristics expressed by the coefficient calculated at 
second coefficient calculating means 521. An example of the 
characteristics of second digital filter 507 which is specified by the 
coefficient output from second coefficient calculating means 521 is shown 
in FIG. 6(b). As shown in this figure, the characteristics set in second 
digital filter 507 form a hill-shaped curve in which the damping factor of 
fundamental frequency fb1 is lowest and then gradually increases toward 
the base of the hill. 
Second coefficient calculating means 521 is provided with a recording means 
for recording only a specific number of the most recent pulse rates. 
Second coefficient calculating means 521 supplies the coefficient in 
response to the change in the pulse rate that is recorded in the recording 
means to second digital filter 507, and changes the slope of the edge line 
of the characteristics. For example, when the change in the pulse rate is 
small, the slope of the edge line is sharp, while when the change is 
large, the slope of the edge line is more gradual. As a result of this 
design, it is possible to avoid the situation in which the pulse wave 
components in the pulse wave signal fall sharply, while also decreasing 
non-pulse wave noise components. 
522 is a third coefficient calculating means (means for setting 
characteristics of the filter) which calculates the coefficient set in the 
third digital filter 508 based on the results (pitch) calculated at pitch 
calculating means 519, and outputs this result. Without exception, the 
characteristics of third digital filter 508 are the characteristics 
expressed by the coefficient calculated at third coefficient calculating 
means 522. An example of the characteristics of third digital filter 508 
which is specified by the coefficient value output from third coefficient 
calculating means 522 is shown in FIG. 6(c). As shown in this figure, the 
characteristics set in third digital filter 508 are pinched at frequencies 
which are multiples of the fundamental frequency fb2 (frequency of the 
fundamental wave of body motion), i.e., cut-off the components of 
frequencies which are multiples of the fundamental frequency fb2 (body 
motion component). 
Third coefficient calculating means 522 is provided with a recording means 
for recording only a specific number of the most recent pitches. Third 
coefficient calculating means 522 supplies the coefficient in response to 
the change in the pitch that is recorded in the recording means to third 
digital filter 508, and changes the strength of the pinching. For example, 
when the change in the pitch is small, the pinching is made stronger and 
the components of frequencies which are multiples of fundamental frequency 
fb2 are greatly damped. Conversely, when the change is large, the pinching 
is made small, and there is not very much damping even if there are 
components of frequencies which are multiples of the fundamental frequency 
fb2. As a result of this design, it is possible to avoid the situation in 
which the pulse wave components in the pulse wave signal fall sharply, 
while also greatly decreasing non-pulse wave noise components (body motion 
components). 
Note that in this embodiment, LCD device 13 carries out the numerical 
display of the pulse rate and pitch in specific regions. However, it is 
also acceptable to display pictorial characters corresponding to numerical 
values, or graphs showing the state of pulse rate and pitch changes. A 
sweep display is also acceptable for the wave form (pulse waveform) 
expressed by the pulse wave signal output from third digital filter 508. 
The structural elements which were functionally expressed in the preceding 
explanation are realized as software by means of circuit elements like a 
CPU, ROM, RAM or the like. The method for realizing these structural 
elements is voluntary matter of design. Accordingly, an explanation is 
omitted as to which structural element is realized with which circuit 
element. Finally, from the perspective of saving space and lowering costs, 
a design is desirable in which as much as possible the above-described 
circuit elements serve in both the watch mode and the pulse measurer mode. 
B: OPERATION OF THE EMBODIMENT 
The operation of the above-described embodiment will now be explained. 
However, since the operation of this device as a watch is well-known, an 
explanation of this function will be omitted here. Note that switching 
between the watch mode and the pulse measurer mode can be accomplished by 
depression of a specific button. 
B-1: Calculation Method Switching Operation 
FIG. 7 is a flow chart showing the flow of basic processing in the pulse 
measurer mode. As shown in this figure, in the pulse measurer mode, pulse 
wave detecting sensor unit 30 and body motion detecting sensor 101 
ordinarily output a pulse wave signal and a body motion signal. The body 
motion signal output from body motion detecting sensor 101 is amplified by 
body motion signal amplifying circuit 510, and supplied to body motion 
signal detecting means 515. As a result, the body motion detecting signal 
which serves as the reference for switching the pulse rate calculation 
method is supplied to calculation method switching means 517 from body 
motion signal detecting means 515. In calculation method switching means 
517, the method for calculating the pulse rate (i.e., frequency analysis 
method/rectangular wave processing method) is switched based on the body 
motion detection signal supplied from the body motion signal detecting 
means 515 (steps S401, S402). 
Specifically, when a body motion detection signal is supplied from body 
motion signal detecting means 515, and when the time period during which a 
body motion detection signal is not supplied is less than a specific 
period of time, then a "body motion present" determination is made. The 
output from pulse wave-body motion component extracting means 516 is 
supplied without alteration to pulse rate calculating means 518 and pitch 
calculating means 519 which are the subsequent steps. As a result, the 
calculation method is switched to the frequency analysis method. 
Conversely, when the time period during which a body motion detection 
signal is not supplied exceeds a specific period of time, then a "body 
motion absent" determination is made. A rectangular wave signal from pulse 
wave rectangular wave processing means 514 and the frequency with respect 
to the body motion pitch from pulse wave-body motion component extracting 
means 516 are supplied to pulse rate calculating means 518 and pitch 
calculating means 519. As a result, the calculation method is switched to 
the rectangular wave processing method. Additionally, in order to conserve 
energy, the operations of unnecessary circuit elements, or the power 
supply to these elements, is suspended in each of these methods. 
B-2: Rectangular Wave Processing Method 
When the rectangular wave processing method is employed as the calculation 
method, the pulse wave signal detected by pulse wave detecting sensor unit 
30 is amplified by pulse wave signal amplifying circuit 501, converted to 
a rectangular wave signal by pulse wave rectangular wave processing means 
514, and supplied to pulse rate calculating means 518 via calculation 
method switching means 517. On the other hand, the body motion signal 
detected by body motion detecting sensor 101 is amplified by body motion 
signal amplifying circuit 510, converted to a digital signal at A/D 
converter 511, and stored temporarily in buffer 512. The body motion 
signal output from buffer 512 is subjected to frequency analysis 
processing (for example, FFT processing in which the duration of detection 
is 16 seconds) at frequency analyzer 522, and the frequency of the 
fundamental wave of body motion is extracted by pulse wave-body motion 
component extracting means 516 from the results of this frequency 
analysis. 
The processing by which pulse wave-body motion component extracting means 
516 determines the frequency of the fundamental wave of body motion and 
the pulse wave from each of the frequency analysis results (spectrums) 
described above will now be explained with reference to FIG. 8. 
FIG. 8 shows an example of the results obtained from frequency analysis of 
the body motion signal. In general, as shown in this figure, the level of 
the frequency component of the second harmonic of body motion is higher 
than the frequency component of the fundamental wave of body motion (i.e., 
the fundamental wave of the user's arm movements). This is due to the 
following. Namely, the fundamental wave of body motion corresponds to a 
pendulum motion, in which the swinging forward and drawing back motion of 
the arms constitutes one period. Typically, however, it is difficult to 
render the swinging of the arms during running into a smooth pendulum 
motion, so that the level of this component is low. In contrast, the 
second harmonic of body motion corresponds to the vertical movement 
generated uniformly when taking steps with the right and left feet, and to 
the acceleration that is applied at the instant the arms swing forward and 
the instant they are drawn back. Thus, second harmonic components appear 
at a high level. 
Accordingly, the second harmonic components of body motion are 
characteristically easy to obtain. In the case of ordinary running, given 
a range of 2 to 4 Hz, it is possible to cover the region in which the 
second harmonic appears, regardless of whether the pace of running is slow 
or fast. Accordingly, by extracting the characteristic second harmonic 
component after limiting the region in this way, it is possible to achieve 
a higher accuracy of detection. 
Therefore, in this embodiment, the frequency (fs) of the highest level 
spectral line is determined from the results of frequency analysis of the 
body motion signal. A determination is then made as to whether or not a 
spectral line above a specific threshold level is present in the frequency 
domain which is 1/2 that of fs. When a determination is made that such a 
spectral line is present, fs is designated as the frequency of the second 
harmonic of body motion, and fs/2 is designated as the frequency of the 
fundamental wave of body motion. When a determination is made that a 
spectral line having a level above a given threshold value is not present, 
then fs is assumed to be the frequency of the third harmonic, and a 
determination is made as to whether or not a spectral line of a level 
above a given threshold value is present in the fs/3 frequency domain. If 
such a spectral line is found to be present, then fs/3 is specified as the 
frequency of the fundamental wave of body motion, while if such a spectral 
line is found to be absent, fs is specified as the frequency of the 
fundamental wave of body motion. Note that the reason why consideration is 
given through the third harmonic is that a range of 2.about.4 [Hz] has 
been assumed for the range in which the fundamental wave of body motion 
can be found to be present. 
The frequency of the fundamental wave of body motion thus specified is 
supplied to pitch calculating means 519 via calculation method switching 
means 517. The preceding is the processing in step S407 in FIG. 7. 
The period (value of the wave interval) of the rectangular wave signal 
supplied via pulse wave-body motion component extracting means 516 is 
obtained in pulse rate calculating means 518. The value obtained by 
multiplying the reciprocal of the period (i.e., the frequency) by 60 is 
designated as the pulse rate. In pitch calculating means 519, the value 
obtained by multiplying the frequency supplied via pulse wave-body motion 
component extracting means 516 by 60 is designated as the pitch (step 
S408). Calculating means 518 is designed to supply the calculated pulse 
rate to coefficient calculating means 520,521, and calculating means 519 
is designed to supply the calculated pitch to coefficient calculating 
means 522. However, the processing to supply the calculated pulse rate and 
pitch is halted during the time period that the rectangular wave 
processing method has been selected (of course, an arrangement is also 
possible in which supply processing is carried out in both cases). The 
pulse rate and pitch calculated by calculating means 518 and 519 are 
displayed by supplying them to LCD device 13, thereby providing visual 
notification to the user (step S409). An arrangement is also possible in 
which the notification is provided to the user be a means which does not 
rely on visual senses, such as using a tone to alert the user of the pulse 
rate and pitch. 
B-3: Frequency Analysis Method 
When the frequency analysis method is employed as the calculation method, 
the pulse wave signal detected by pulse wave detecting sensor unit 30 is 
amplified by pulse wave signal amplifying circuit 501, converted to a 
digital signal (for example, an integer value in the range of 
-127.about.127) by A/D converter 502 (step S403), and temporarily stored 
in buffer 503. Since the processing carried out on the body motion signal 
to obtain the frequency of the fundamental wave of body motion is 
equivalent to that described under the preceding section "B-2: Rectangular 
wave process method", an explanation thereof is omitted here. 
Filter processing by first through third digital filters 506.about.508 is 
carried out on the pulse wave signal that was temporarily stored in buffer 
503, thereby reducing or removing the noise component in the pulse wave 
signal (step S404). This filter processing will now be explained in order 
below. 
When the detected value (a 4-second pulse wave signal, for example) stored 
in buffer 503 is not being effected by impulse noise, i.e., more 
specifically, when the proportion of values detected outside a specific 
range with respect to the number of values detected overall in buffer 503 
is below a specific threshold value, then a signal (a signal which a value 
of "0", for example) indicating that impulse noise was not detected is 
output from impulse noise detecting means 505 according to the timing at 
which the detected value is output from buffer 503 to first digital filter 
506. The coefficient calculated by first coefficient calculating means 520 
based on the pulse rate calculated immediately previously is supplied to 
first digital filter 506. Because a signal indicating that impulse noise 
was not detected is supplied from impulse noise detecting means 505, those 
characteristics pass through for all bands. Accordingly, the pulse wave 
signal is supplied without modification to second digital filter 507. 
In contrast, when the detected value stored in buffer 503 is being effected 
by impulse noise, i.e., more specifically, when the proportion of values 
detected outside a specific range with respect to the number of values 
detected overall in buffer 503 exceeds a specific threshold value, then a 
signal (a signal having a value of "1", for example) indicating that 
impulse noise was detected is output from impulse noise detecting means 
505 according to the timing at which the detected value is output from 
buffer 503 to first digital filter 506. In this case, the characteristics 
of first digital filter 506 become such as shown in FIG. 6(a), and 
components which are not frequency components of the anticipated pulse 
wave are damped or cut-off. 
An example of the waveform of the pulse wave signal before filtering by 
first digital filter 506 is shown in FIG. 9(a), while the result obtained 
after FFT processing of this waveform is shown in FIG. 9(b). An example of 
the waveform of the pulse wave signal after filtering of this same pulse 
wave signal by first digital filter 506 is shown in FIG. 10(a), while the 
result obtained after FFT processing of this waveform is shown in FIG. 
10(b). As shown in these figures, low frequency components (impulse noise) 
are greatly damped by first digital filter 506. Namely, the impulse noise 
component in the pulse wave signal is greatly reduced or removed by first 
digital filter 506. 
The coefficient calculated by second coefficient calculating means 521 
based on the pulse rate calculated immediately previously is supplied to 
second digital filter 507. These characteristics are as shown in FIG. 
6(b). In other words, these characteristics are such that the degree of 
damping increases with greater distance from the frequency of the pulse 
wave. Accordingly, in addition to impulse noise, other noise components 
are also damped. In situations in which the pulse rate does not change 
abruptly, such as when the user is at rest, then a frequency component 
which is only slightly separated from the frequency of the anticipated 
pulse wave may also be considered a noise component. 
In situations when the pulse changes abruptly, such as at the start of 
exercise, there is a possibility that frequencies that are separated to 
some degree from the frequency of the pulse wave anticipated will include 
essential pulse wave components. Therefore, second coefficient calculating 
means 521 is designed to make the slope of the edge line in FIG. 6(b) 
steep when the change in the pulse rate is small, and to make the slope 
more gradual when the change in the pulse rate is large, so that noise 
components are damped without damping the essential pulse wave components 
very much. 
The coefficient calculated by third coefficient calculating means 522 based 
on the pitch calculated immediately previously is supplied to third 
digital filter 508, with these characteristics being as shown in FIG. 
6(c). As explained above, reference frequency fb2 is the frequency of the 
fundamental wave of body motion. Accordingly, the harmonic components and 
the fundamental wave component of body motion in the pulse wave signal are 
damped. Additionally, in the same way that second coefficient calculating 
means 521 acts on second digital filter 507, third coefficient calculating 
means 522 intensifies the pinching in FIG. 6(c) when the change in the 
pitch is small and reduces the pinching when the change in the pitch is 
large. Accordingly, in situations where the pitch does not change 
abruptly, the body motion components are greatly reduced or removed, while 
in situations when the pitch does change abruptly, such as when exercise 
is initiated, the preceding pitch and the current pitch may differ 
greatly. Thus, damping of the body motion components is confined to a 
small amount. 
The pulse wave signal thus shaped is subjected to specific frequency 
analysis processing (in this embodiment, FFT processing having a detection 
time of 16 seconds) by frequency analyzer 509 (step S405). 
Next, pulse wave-body motion component extracting means 516 specifies the 
frequency of the fundamental wave of body motion and the pulse wave from 
the results (spectrums) obtained from the above-described frequency 
analysis (step S406). The processing for determining the frequency of the 
fundamental wave of the pulse wave will now be explained. 
Pulse wave-body motion component extracting means 516 first selects the 
spectral lines in order starting with the highest level spectral line from 
among the results obtained from frequency analysis of the pulse wave 
signal. Pulse wave-body motion component extracting means 516 then 
compares the frequency of the selected spectral lines with the frequency 
of the fundamental wave of body motion (fs/2 for example) and the 
frequency of the higher harmonic waves (fs, 3 fs/2, for example). If they 
do not coincide, pulse wave-body motion component extracting means 516 
specifies the frequency of the aforementioned spectral lines as the 
frequency of the fundamental wave of the pulse wave. The frequency of the 
fundamental wave of the pulse wave thus specified is then supplied to 
pulse rate calculating means 518 via calculation method switching means 
517. 
The fundamental wave and harmonic components of body motion are greatly 
reduced or removed from the pulse wave signal by third digital filter 509. 
Accordingly, it is theoretically acceptable to provide a design in which 
the frequency of the highest level spectral line from the results of 
frequency analysis of the pulse wave signal is simply specified as the 
frequency of the fundamental wave of the pulse wave. However, in this 
case, when the pitch changes abruptly, the amount of damping carried out 
on the fundamental wave and harmonic components of body motion by the 
third digital filter remains slight. Thus, there is a possibility that the 
spectral lines of the remaining body motion components may be selected as 
the spectral line of the fundamental wave of the pulse wave. Accordingly, 
it is preferable to change the processing in response to the degree of 
change in the pitch. 
Next, the pulse rate is calculated from the aforementioned frequency at 
pulse rate calculating means 518 to which the frequency of the fundamental 
wave of the pulse wave is supplied. This pulse rate is supplied to LCD 
device 13, first coefficient calculating means 520, and second coefficient 
calculating means 521. The pitch is calculated from the frequency at pitch 
calculating means 519 to which the frequency of the fundamental wave of 
body motion was supplied. This pitch is supplied to LCD device 13 and 
third coefficient calculating means 522 (step S408). It is also acceptable 
to provide a design in which the value supplied from pulse rate 
calculating means 518 to first coefficient calculating means 520 and 
second coefficient calculating means 521, and the value supplied from 
pitch calculating means 519 to third coefficient calculating means 522, 
are designated as each of the frequencies supplied via calculation method 
switching means 517, and in which each of coefficient calculating means 
520.about.522 calculate the coefficients based on each of the 
aforementioned frequencies. 
Note that the pulse rate and pitch supplied to LCD device 13 are displayed 
in the corresponding region, thereby providing notice to the user (step 
S409). 
C: SUMMARY 
As explained above, the present embodiment enables damping or removal of 
noise components in a pulse wave signal by employing first through third 
digital filters 506.about.508. As a result, it is possible to improve the 
accuracy of processing to detect the pulse rate using frequency analysis 
in a subsequent step. In addition, the pulse wave signal itself is shaped, 
so that, for example, in an arrangement in which the pulse wave itself is 
displayed, it is possible to display an even more accurate waveform for 
the pulse wave. 
Moreover, at the first digital filter, when impulse noise has not been 
generated, then the signal over the entire region passes through the 
filter. Thus, pulse wave signals which do not contain superimposed impulse 
noise are not subjected to filtering. Further, since filtering primarily 
damps or removes impulse noise components, there is no concern that 
essential pulse wave components present in the area of superimposition of 
the impulse noise will be greatly reduced or removed. 
Since frequency components to be removed are not present, or at least have 
been damped, at the second digital filter, there is no concern that 
essential pulse wave components will be removed, even if the pulse rate 
changes abruptly. The frequency components of the fundamental wave and 
higher harmonic waves of body motion are greatly damped or removed at the 
third digital filter, thus subsequent processing is reduced. In addition, 
since the characteristics of the second and third digital filters can be 
changed in response to the degree of change in the pulse rate or pitch, it 
is possible to obtain an even more accurate pulse waveform and pulse rate. 
D: MODIFICATIONS 
The preceding embodiments employed first.about.third digital filters 
simultaneously, however an arrangement is also possible in which only one 
or two of these filters is employed. It is also acceptable to combine the 
second and third digital filters to realize a single filter. An 
arrangement may also be considered in which the buffer and impulse noise 
detecting means are omitted, and filtering is carried out on all pulse 
wave signals using the first digital filter. In this case, first through 
third digital filters may be realized as one single filter. In addition, 
the arrangement for mounting the device is not limited to a wristwatch, 
rather, a necklace or eyeglasses may also be considered. Of course, the 
pulse measurer may also be used alone, or as a device for detecting pulse 
waves.