JPH0357430A - Photoelectric pulsimeter - Google Patents

Abstract

PURPOSE:To prevent a whisker pulse which becomes a pulse signal (HPUL) from being recognized erroneously as a correct HPUL signal generated by a pulse by masking the HPUL signal in a specific period after turn-on of a light emitting element is started. CONSTITUTION:An LED light emitting signal (c) brings an LED inputted to a switching transistor 13 for LED light emission to light emission and an HPUL detecting signal (f) is delayed by 4096Hz and inputted to a clock of a half latch 26 for generating the HPUL signal. The half latch 26 for setting an HPUL signal (b) outputted from an amplifying circuit 17 as data latches the data by a clock signal delayed by 4096Hz from an LED light emission period and inputted, therefore, it does not occur that a whisker pulse generated in the LED light emission period becomes data, and only a pulse can be outputted exactly as a pulse signal (g) to an arithmetic means 27 by a CPU and a logic circuit, etc. Also, the half latch 26 is reset (h) by the arithmetic means 27, etc., after outputting the pulse signal (g), and becomes a state of waiting for an input of the next HPUL signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a photoelectric pulse meter having a light emitting element that lights up intermittently.

[Summary of the invention]

The present invention utilizes a pulse signal (hereinafter referred to as HPL) which is the output of an amplifier circuit.
When detecting the JL signal on the CPU side, by masking the detection when the light emitting element is in the ON state, it is possible to detect only the pulse signal without recognizing the whisker pulse that accompanies the lighting of the light emitting element. This is what I did.

(Prior Art) Conventionally, LEDs and the like have been used as light-emitting elements in pulsometers that use optical means to detect changes in blood flow and count and display pulse rates. If you turn it on, the current consumption will be very large.
The LED's light emission is intermittently lit at the minimum light emitting time in order for changes in blood flow to be captured as electrical signals via the light receiving element, reducing the consumption of t current by 1! We are trying to reduce ff. (Jitsukai 53rd year)
(Refer to Japanese Patent No. 76697) The general operation will be explained using the schematic diagram of the photoelectric pulse meter shown in FIG.

Here, LED II is used as a light emitting element. This LE
DII intermittently emits light via the switching transistor 13 in response to the light emission signal C from cputs. The intensity of the emitted light is adjusted by the current limiting resistor l2. The emitted infrared light hits the subject's finger 14 and the magnitude of the blood flow is converted into the intensity of reflected light, which is transmitted to the light receiving element 15. Here, the light receiving element 15 uses a phototransistor.

Since the output of the phototransistor 15 generates a current according to the strength of the reflected light, the resistor 16 generates a blood flow voltage a that corresponds to the strength of the blood flow in the finger. The HPUL signal b is amplified, shaped, and synchronized with the pulse.
The HPUL signal is manually inputted to the PLl 18, and the CPU 18 calculates the pulse rate per unit time based on the period at which the HPUL signal is manually inputted.
Although not shown here, it writes to memory and displays it. 19 is a battery that supplies current to each of the circuits mentioned above. [Problem to be Solved by the Invention] When measured using the above method, when a battery is used as a power source for a pulse meter, the internal resistance of the battery decreases when the battery capacity decreases or the environmental temperature becomes low. When it becomes high, when the light emitting element is turned on, the voltage drops due to the voltage drop due to the current flowing through the light emitting element, and a whisker pulse is generated in the waveform shaping circuit, which is the final output stage of the amplifier circuit, in synchronization with the lighting of the light emitting element.
Whisker pulses may appear on the HPUL signal.

FIG. 3 illustrates the above state. When operating normally, the HPUL signal b is only a pulse signal synchronized with the pulse like b1, but if a whisker pulse is generated for the reason mentioned above, the HPUL signal b is only a pulse signal synchronized with the pulse as shown in b-2. This has the disadvantage that if the whisker pulses are overlapped with each other and the CPU recognizes the whisker pulses as an HPUL signal, it becomes impossible to accurately calculate the pulse.

[Means to solve the problem]

In order to solve the above problem, in the present invention, the HPUL signal is masked during a specific period after the light emitting element starts lighting, so that the whisker pulse that becomes the HPUL signal is not mistakenly recognized as the correct HPUL signal due to the pulse. I made it. [Operation] By taking the above-mentioned signals, the CPU will not mistakenly recognize the whisker pulse as an HPUL signal, so it will be able to recognize only the correct HPUL signal synchronized with the pulse and calculate the correct pulse rate. Become.

〔Example〕

In the following, embodiments of the present invention will be explained in terms of software implementation and hardware implementation based on the drawings. Note that the photoelectric pulse detection circuit is the same as that shown in FIG.

Figure 1 is an example of a flowchart when the present invention is implemented by programming to CP018. When a periodic (in this example, 128 Hz) light emitting ink is applied to cause LED II to emit light intermittently, LEDon command 2 is issued.
．． The LEDoff command 4 is executed sequentially, and the LEDon time is managed by the WAIT routine 3 as a time during which a change in blood flow can be prompted as an electrical signal via the light receiving element. During this LEDon time, the level of the HPUL signal b is not detected because a whisker pulse may occur due to current fluctuations. After L E Doff, wait until the power supply stabilizes and the whisker pulse disappears using WAIT routine 5, then detect the level of HPUL signal b (
In step 6), if the HPUL signal b is #L', it is determined that there is no pulse pulse input and the process exits to H A LTIO (step 7). If HPIJL signal b is "L", it is determined that there is no pulse pulse human power and the process goes to 7LHALT10 (
Step 7). If the HP[JL signal b is 'H', it is assumed that a pulse pulse has been received, and HPUL human recognition processing to check the pulse width and processing such as pulse rate calculation are performed. In the above example, the level of the HPUL signal b is detected every time the LED emits light, but depending on the accuracy of pulse rate detection, the level may be detected at a faster cycle, or
It is also possible to consider a method in which the period excluding the time from LED off to LED off and the period thereafter excluding a specific period is detected at any time.

Next, a case in which it is implemented in hardware will be explained.

FIG. 4 is a schematic diagram of the circuit B structure including the pulse pulse detection means 22. For example, if the LED light emission cycle is 128Hz;
When the emission time is 4096 tlz, the output from the OSC 20 and the frequency divider 21 is 2048}1z, 12
8} The pulse pulse detection means 22 which uses the 1z signal as a human power outputs an LED light emitting signal C with a pulse width of 4096 Hz from the NOT circuit 26, the Frisopfurosop circuit 23, and the gate circuit 28 in synchronization with the rise of the 12811z signal, and
The circuit 27, the flipflop circuits 24, 25, and the gate circuit 29 output the HPUL detection signal f delayed by 4096 Hz from the LED light emission signal C. The relationship between the LED light emission signal C and the HP[JL detection signal f is shown in FIG. The LED light emission signal C causes the LED which is manually applied to the LED light emission switching transistor l3 to emit light, and the LED light emission signal C
The PUL detection signal f is delayed by 4096 Hz and then output to HPUL{. t
The signal is input to the clock 7 of the half latch 26 for signal generation.

Half launch 2G using HPtJL signal b output from amplifier circuit 17 as data is 4096 times from the LED light emission period.
11z Since the data is launched by the clock signal that is input with a delay, the pulse pulse generated during the LED light emission period is not used as data, and only the pulse pulse is accurately used as the pulse signal g, and a 1,000-stage operation is performed using the CPU, logic circuit, etc.27
can be output to. Further, after the half latch 26 outputs the pulse signal g, the reset h is reset by the calculation means 27 or the like.
Then, the machine waits for the next f{PUL signal.

〔Effect of the invention〕

By using the above method to detect pulse pulses during a period other than when the LED is emitting light, it is possible to prevent whisker pulses that occur when the TL source voltage fluctuates from being mistakenly recognized as pulse pulses. It will be possible to detect and display the pulse stably and accurately without being affected by the pulse.

[Brief explanation of drawings]

Fig. 1 is a flowchart of the present invention, Fig. 2 is a schematic diagram of a photoelectric pulse meter, Fig. 3 is a waveform diagram of an HPUL signal, and Fig. 4 is a circuit when the present invention is implemented in hardware. 5A and 5B are timing charts in the case of hardware implementation. 1l...Light emitting element, light receiving element, amplifier circuit, CPU, pulse pulse detection means or more

Claims (1)

[Claims] A photoelectric pulse detection circuit consisting of a light-emitting element that lights up intermittently, a light-receiving element, and an amplification circuit that amplifies the output of the light-receiving element and outputs a pulse pulse, and calculates the number of pulses per unit time, etc. from the pulse pulse. 1. A photoelectric pulse meter having a calculation means for calculating the pulse rate, further comprising a pulse pulse detection means for detecting the pulse pulse during a period other than when the light emitting element is turned on.