JPH0730008Y2 - Finger pulse wave sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention inserts a fingertip between a light emitting element and a light receiving element,
The present invention relates to a finger plethysmography sensor that detects a volume change of a blood vessel due to a pulsation as an electric signal by a change in a transmitted light amount.

[Conventional technology]

As a conventional fingertip pulse wave sensor of this kind, a pad on the nail side of the fingertip in which one of the light receiving element and the light emitting element is embedded,
The other one is made to face the pad on the ventral side, and a U-shaped bent leaf spring is attached to the back surface of one of the pads, and the fingertip inserted between both pads is clamped in a compressed state. Such a leaf spring type is well known.

Further, the two arms in which the light-receiving element and the light-emitting element are embedded are hinged to each other in a clothes-sandwiched shape, and a coil spring is attached to the hinge pin to urge the finger pinches toward each other. Wave sensors are also known.

[Problems to be solved by the device]

In such a fingertip pulse wave sensor, setting the fingertip setting position accurately is important for ensuring the accuracy of the detected waveform. Particularly, in an acceleration fingertip plethysmometer that non-invasively monitors the state of peripheral circulation by differentiating the detected waveform twice with respect to time to convert it into an acceleration waveform, the accuracy of the detected waveform greatly affects the measurement result. .

However, in the conventional fingertip pulse wave sensor, no consideration was given to accurately setting the fingertip and confirming the regular setting.

Accordingly, the applicant of the present application has provided a fingertip stopper on the fingertip abdomen setting surface and a position closer to the fingertip abdomen setting surface than the nail position in front between the fingertip abdomen setting surface and the fingertip apex stopper surface. , And proposed a fingertip pulse wave sensor with a touch sensor that detects the contact of the tip. This makes it possible to set the fingertips easily and accurately, and the fingertip set can be monitored without distorting the fingertips just by touching the stopper with the fingertips, and not only for the examinee but also for the examiner. It is easy to check the set status.

However, when using a capacitance type touch sensor known per se, when trying to detect a fingertip set with high accuracy, there is a problem that commercial power supply voltage is induced in the electrode plate and interferes depending on the surrounding conditions. .

Therefore, the present invention is based on the assumption that a touch sensor that detects that the oscillation frequency defined by the capacitance of the electrode plate is reduced by setting the fingertip to the regular setting position is used. It is an object of the pulse wave sensor to prevent a decrease in detection accuracy of a fingertip set even when a commercial power supply voltage is induced in the electrode plate.

[Means for Solving the Problems]

According to the present invention, in order to achieve this object, a fingertip stopper having a height that allows a protruding nail to escape is provided on a fingertip belly setting surface, and at least the surface of the fingertip stopper is set to a regular position. An electrode plate of a touch sensor that detects the fingertips from the change in capacitance is provided, and an oscillation circuit that oscillates at a frequency corresponding to the capacitance of the electrode plate is provided on this electrode plate as the circuit part of the touch sensor. A countdown circuit that counts down the oscillation signal by the ratio of the commercial power frequency / oscillation frequency at the time of fingertip detection, and the cycle of this counteddown signal changes from the non-detection period to the oscillation frequency when the fingertip is set to the normal position. This is followed by a countdown period determination circuit that detects the corresponding increase in the length and outputs a fingertip detection signal.

[Action]

When the fingertip is set at a regular position between the fingertip abdomen setting surface and the nail setting surface and comes into contact with the fingertip stopper, the oscillation frequency of the oscillating circuit decreases due to an increase in the capacitance of the electrode plate by a predetermined amount. In the countdown circuit, this oscillation signal is converted into a signal that is counted down by the ratio of the commercial power frequency / oscillation frequency at the time of fingertip detection. Therefore, even if the cycle of each counted down oscillation signal changes according to the magnitude of the ± voltage induction of the commercial power supply during the countdown process, it is finally converted into a countdown signal of almost the commercial power supply cycle, and the effect of ± voltage induction Are canceled out over the cycle of the commercial power source, and fluctuations in the cycle are avoided. The countdown cycle determination circuit detects that the cycle of the countdown signal has become longer than a predetermined reference predetermined cycle, outputs a fingertip detection signal, and automatically starts notification or measurement.

[Example of device]

1 to 4 show a fingertip pulse wave sensor according to an embodiment of the present invention.

In these figures, 10 is a fingertip set table that is installed on a flat surface, and the surface of the fingertip set surface 11 is inclined to correspond to the standard shape of the fingertip ball in a natural state with respect to the bottom surface. And a fingertip guide surface 12 inclined at the same gradient corresponding to the belly between the first and second joints of the following finger, and a raised surface 13 is formed in which the vicinity of the third joint is located at the apex. Furthermore, on both sides of the fingertip belly setting surface 11 and the fingertip guide surface 12,
The guide walls 10a are formed at intervals slightly wider than the standard finger width.

A circular transparent window 14 that also functions as a clearance for the central portion of the fingertip pad is formed on the fingertip pad setting surface 11, and the tip has a curved shape corresponding to the tip shape of the fingertip and is long. A stopper 30 having a height that allows the extended claw to escape is formed.

Electrode plate 38 made of copper foil (indicated by a dotted line in the figure) is formed around the transparent window 14 on the front surface of the stopper and the finger-tip pad setting surface 11 so as to form a capacitive touch sensor. But,
It is attached to the inner side in consideration of safety, and is covered with a larger-shaped insulating sheet 39 so as to be completely hidden on the upper surface.

As shown in FIG. 2, this electrode plate oscillates at a frequency corresponding to the electrostatic capacitance present between the grounds, for example, 500 kHz, and when the fingertip is set to the normal position, the electrostatic capacitance increases. , An oscillator 40 whose oscillation frequency changes to, for example, 200 kHz,
A countdown circuit for converting the oscillation signal into a rectangular wave signal counted down to 50 Hz / 200 KHz≈1 / 2 ¹² = 1/4, 096, for example, a flip-flop circuit 41, and a cycle of the counted down rectangular wave signal when the contactless This is followed by a countdown cycle determination circuit 42 which outputs a fingertip detection signal when the cycle reaches a reference cycle, for example, 18 ms (pulse width 9 ms) from the cycle 8.2 ms (pulse width 4.2 ms).

This discrimination circuit compares, for example, a CR charging circuit 421 for a counted down rectangular wave signal with a comparator 422 which compares the charging voltage with a level corresponding to a reference period and outputs a fingertip detection signal when this level is reached. It is configured. Also,
The reference period of 18 ms is set in consideration of the variation in the capacity increase in the regular set state with respect to the period of 20.48 ms in which 200 kHz is counted down at a reduction ratio of 1/2 ¹² . Further, the characteristics of the oscillator 40, including the shape characteristics of the electrode plate 38, cannot be lowered to about 200 kHz when the fingertip 1 is in contact with only the stopper 30 or only the fingertip abdomen setting surface 11, that is, the countdown period. Is set so that the reference period does not reach 18 ms.

Reference numeral 20 denotes a claw pressing slider, and an inner surface panel 20b thereof is provided with a claw contact surface 21 for contacting a claw, and slider arms 22 inclined to the bottom surface 10b are provided on both sides of the claw contact surface 21. It is mounted so as to be slidable in guide grooves 18 on both walls of 10. A light receiving element 19 is mounted behind the transparent window 14, and a light emitting element 29 is mounted behind the transparent window on the claw contact surface 21. A cover 35 made of a matte translucent synthetic resin is attached to the inner panel 20b. Further, a plate-like bracket 37, on which 12 LEDs 36 are set on the front surface and 20 LEDs on each of the both surfaces, is installed so that the cover 35 is illuminated from the back surface.

A lower end between both slider arms 22 is connected by a rod 23, and a core of a bobbin 16 rotatably attached to an arm 15 provided below is provided inside the raised surface 13, that is, inside the rear of the fingertip setting base 10. A constant load mainspring 17 known per se, whose inner end is crimped by spring force, is stored in the main body. The outer end 17a of this spring is locked to the rod 23.

The operation of the fingertip pulse wave sensor thus configured is as follows.

Normally, the slider 20 is closed by occupying the position where the trailing edge 20c abuts the leading edge 10c of the fingertip setting table 10.

At the time of measurement, insert the fingertip 1 into the gap S on the fingertip guide surface 12 and slide it along the fingertip guide surface 12 so that the fingertip pad is in contact with the fingertip pad setting surface 11. The tip of the point is advanced until it abuts the stopper 30. As a result, when the fingertips 1 come into contact with the central portions of the front surface and the bottom surface, which are the regular set positions on the insulating sheet 39, the electrostatic capacitance exhibited by the electrode plate 38 increases and the oscillator 40 oscillates at about 200 kHz. The oscillation signal is converted into a rectangular wave signal with a period of about 20.48 ms by the flip-flop operation in the countdown circuit 41.

At this time, the oscillation signal of 200 kHz is amplitude-modulated by the induction of ± half-wave voltage in the cycle of the commercial power supply. Therefore, the cycle of each oscillation signal fluctuates in the countdown process, and the accuracy will be reduced if discrimination is attempted in this process. It may decrease. However, by finally counting down to approximately the commercial power supply cycle, the influence of the power supply induction over the commercial power supply cycle is averaged or canceled, and a rectangular wave signal having a cycle in which the influence of the power supply induction is removed is obtained. Then, a stable rectangular wave with a period of about 20 ms is generated corresponding to the variation in the capacitance when the fingertip is set, and even when the commercial power supply is 60 Hz, the canceling action is obtained almost corresponding to the power supply cycle. To be The countdown cycle determination circuit 42 detects that the cycle of the counted down rectangular wave exceeds 8.2 ms to 18 ms, outputs a fingertip detection signal, and causes all the LEDs 36 to cause the cover 35 to emit light in a planar manner. The claw abutment surface 21 separates from the fingertip abdomen setting surface 11 corresponding to the height of the claw, but its pressing force does not vary between individuals due to the constant load spring, and is maintained at a substantially constant and appropriate value. No disturbance light is incident, the fingertip 1 is constantly positioned and stabilized on the fingertip abdomen setting surface 11, and the pulse wave waveform is not distorted due to excessive pressure.

When the fingertip 1 is in contact with the insulating sheet 39 while being displaced in the peripheral direction, the capacitance of the electrode plate 38 is insufficiently increased, so that the fingertip detection signal is not generated and the LED 36 does not emit light. . Furthermore, the fingertip 1 floats from the fingertip abdomen setting surface 11 and the stopper 30
Over the top of the upper end 32, or if the stopper 30
Even if the tip of the fingertip touches the tip of the fingertip and the contact to the fingertip abdomen setting surface 11 is incomplete and floating, the contact area is insufficient and sufficient capacitance increase cannot be obtained. No signal is output.

There are various conceivable structures of the sensor body, such that the sliding direction is parallel to the bottom surface, or a helical spring that is sufficiently long for the sliding stroke is used for a constant load.

A timer may be provided to such a touch sensor so that a start signal for automatically starting measurement can be output when the detection signal is continuously generated for a predetermined time or longer.

[Effect of device]

As described above, according to the present invention, by using the capacitance type touch sensor, the fingertip set can be detected only by bringing the fingertip into contact with the electrode plate. It is possible to obtain various pulse waveforms. Moreover, even when the commercial power source is guided to the electrode plate, the cycle corresponds to the commercial power cycle period for discriminating, so that the influence of the power source voltage in the countdown process is averaged and the influence of the power source induction can be avoided.

[Brief description of drawings]

FIG. 1 is a perspective view of a fingertip pulse wave sensor according to an embodiment of the present invention, excluding a slider portion, and FIG. 2 is a diagram showing a configuration of a circuit portion of the fingertip pulse wave sensor according to the embodiment, and FIG. FIG. 4 is a central sectional view of the fingertip pulse wave sensor according to the same embodiment, and FIG. 4 is a perspective view showing a fingertip wearing state of the fingertip pulse wave sensor according to the embodiment. DESCRIPTION OF SYMBOLS 1 ... Finger tip, 11 ... Finger tip set surface, 19 ... Light receiving element, 21 ... Nail contact surface, 29 ... Light emitting element, 30 ... Stopper, 38 ... Electrode plate, 39
…Insulating sheet.

Claims (1)

[Scope of utility model registration request] 1. A light emitting element is provided on one side of the fingernail belly setting surface and the nail setting surface while the fingernail belly setting surface on which the ball of the fingertip is set and the nail setting surface on which the nail is set face each other. Then, in the fingertip pulse wave sensor in which the light receiving element is arranged to face the other side and detects the volume change of the blood vessel due to the pulsation as an electric signal by the change of the transmitted light amount, the fingertip belly set surface is projected. A fingertip stopper with a height that allows the nail to escape is provided in a protruding manner, and at least the surface of this fingertip stopper is provided with an electrode plate for a touch sensor that detects the fingertip set at the proper position from the change in capacitance. An oscillation circuit that oscillates at a frequency corresponding to the electrostatic capacitance exhibited by the electrode plate as a circuit portion of the touch sensor on the plate, and counts down this oscillation signal at a ratio of approximately commercial power frequency / oscillation frequency at fingertip detection. You The countdown circuit and the period of the counted down signal are detected to increase from the period of non-detection corresponding to the oscillation frequency when the fingertip is set to the regular position, and the fingertip detection signal is output. A finger pulse wave sensor, characterized in that it is followed by a countdown period determination circuit.