JPH11128184A - Reflection type photoelectric pulse wave detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection type photoelectric pulse wave detection device having good measuring accuracy by automatically arraying to an optimum depth the depths at which beams of plural kinds of wavelengths irradiated to a living body, scattered within the living body, and received by photocells are scattered. SOLUTION: Two kinds of light emitting elements which emits beams of two kinds of wavelengths are varied in emission strength by a light emitting element drive circuit 30 and are made to emit light beams, which are scattered at different depths inside a living body. The beams emitted from the surface of the body are received by a photocell. The ratio of the alternate to direct components of the emitted beams is calculated by an alternate- direct component ratio calculation means 66, and an optimum emission strength is determined by an optimum emission strength determination means 67 according to an inflection point on the curve of change of the alternate-to-direct component ratio with respect to the emission strength. Since the inflection point shows that the beams are scattered at the depth where the density of peripheral blood vessels abruptly increases, the depths at which the beams of the two wavelengths irradiated toward the living body are scattered can be arrayed automatically, resulting in enhanced measuring accuracy of a reflection type photoelectric pulse wave detection device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type photoplethysmogram which is attached to a living body and detects a photoplethysmogram including biological information obtained from a peripheral blood vessel under the epidermis such as oxygen saturation or hematocrit value. The present invention relates to a wave detection device.

[0002]

2. Description of the Related Art In order to detect biological information obtained from peripheral blood vessels under the epidermis of a living body, it is attached to a living body, and a predetermined portion of the living body epidermis is irradiated with light of a plurality of wavelengths. There is known a reflection type photoplethysmographic detector which detects backscattered light, ie, photoplethysmogram, which is irregularly reflected in the light and emitted from a predetermined portion thereof. For example, in a reflection-type photoplethysmography device used for oxygen saturation measurement, a light-emitting element that emits red light having a wavelength whose absorption coefficients of oxyhemoglobin and anoxic hemoglobin are significantly different from each other is used as a light-emitting element; Two types of light-emitting elements that emit infrared light having a wavelength at which the absorption coefficient of the modified hemoglobin is substantially the same, including light scattered from peripheral blood vessels in the dermis or subcutaneous tissue under the body surface of a living body The oxygen saturation is calculated based on the photoelectric pulse wave.

[0003]

However, the light emitted to the living body is scattered in the living body, and the photoelectric pulse wave emitted from the body surface mainly reflects the scattered light at any depth from the body surface. The inclusion depends on the penetration depth into the epidermis, and the penetration depth varies depending on the wavelength of the irradiated light and the intensity of the light. Therefore, light of a plurality of different wavelengths is irradiated on the living body, and when scattered light in the living body is received by the light receiving element, the light between the plurality of types of light emitting elements and the light receiving element in the housing. If the distances are substantially equal, information at different depths may be reflected, and measurement accuracy may not be obtained. Also,
The thickness of the epidermis and the dermis varies depending on gender, age or individual, and also varies depending on the part of the living body. Further, at what depth below the body surface the scattered light is mainly received by the light receiving element also depends on the positional relationship between the light emitting element and the light receiving element. Therefore, the biological information may not be measured by the scattered light at the optimum depth.

The present invention has been made in view of the above circumstances, and an object of the present invention is to irradiate a living body, scatter in the living body, and scatter light of a plurality of wavelengths received by a light receiving element. An object of the present invention is to provide a reflection-type photoplethysmographic detector with high measurement accuracy by automatically adjusting the depth at which light is scattered to the optimum depth.

[0005]

SUMMARY OF THE INVENTION A first aspect of the present invention to achieve the above object is to provide a housing and a plurality of wavelengths of light which are accommodated in the housing and directed toward the epidermis of a living body. A plurality of types of light-emitting elements that are illuminated, and are housed in the housing at a predetermined distance from the light-emitting elements via light-shielding walls, and light from the plurality of types of light-emitting elements is scattered under the surface of the living body. A light receiving element that receives light of a plurality of wavelengths emitted from the body surface,
A reflection-type photoplethysmogram detection device for detecting photoplethysmograms for obtaining biological information based on the plurality of types of emission lights, respectively, wherein (a) a drive current is sequentially supplied to the plurality of types of light emitting elements And a light emitting element driving circuit capable of adjusting the light emission intensity of each of the light emitting elements; and (b) determining a ratio of an AC component to a DC component of the emitted light detected by the light receiving element for each of the wavelengths. (C) a ratio between an AC component and a DC component calculated from the emitted light detected by the light receiving element by the AC / DC component ratio calculating means, and light emission driven by the light emitting element driving circuit. Means for determining the relationship with the emission intensity of the element for each wavelength, and determining the optimum emission intensity for each wavelength from the relationship, and (d) determining the optimal emission intensity prior to the detection of the photoelectric pulse wave. Departure The optimum luminous intensity adjusting means for the causing plural types of light emitting elements to emit light respectively to the light emitting element driving circuit at the optimum light emission intensity determined by the intensity determining means,
To include.

[0006]

According to the first aspect of the present invention, the light emitting element driving circuit adjusts the light emitting intensity of the light emitting element that emits light of each wavelength to cause the light emitting element to emit light.
The emitted light scattered at different depths in the living body is detected by the light receiving element by the change in the light emission intensity. For the received emitted light, the ratio between the AC component and the DC component is calculated by the AC / DC component ratio calculation means, and the optimum emission intensity determination means:
The optimum luminescence intensity is determined based on the change curve of the ratio of the AC component and the DC component to the luminescence intensity, and in the state where the photoelectric pulse wave is detected to measure the biological information, the luminescence element is adjusted by the optimum luminescence intensity adjusting means. Light is emitted at the optimum emission intensity. The change curve of the ratio of the AC component to the DC component with respect to the emission intensity changes in relation to the density of the peripheral blood vessels at the depth where the scattered light is scattered. Therefore, by determining the light emission intensity of the light emitting element based on the change curve, the depth at which the scattered light of a plurality of wavelengths that are irradiated to the living body and scattered in the living body and received by the light receiving element is scattered, respectively. The depth can be automatically adjusted to the optimum depth, and the measurement accuracy of the reflection-type photoplethysmographic detector is improved.

[0007]

According to a second aspect of the present invention, there is provided a light emitting apparatus comprising: a plurality of types of light emitting devices for irradiating light of a plurality of types of wavelengths toward an epidermis of a living body; An element and a plurality of wavelengths of light emitted from the body surface while being received at a predetermined distance from the light emitting element and scattered by the light from the plurality of light emitting elements under the surface of the living body under the skin. A reflection type photoplethysmography device for detecting a photoplethysmogram for obtaining biological information based on the light of the plurality of wavelengths, wherein (a) the plurality of types of light-emitting devices are provided. And a light receiving element are housed in a state where a light shielding wall is interposed therebetween, and a plurality of light emitting elements provided for each of a plurality of types of wavelengths are arranged such that a distance between the light receiving element and the light receiving element gradually varies. A housing provided, and (b) the housing A light emitting element driving circuit capable of selectively emitting a light emitting element to be emitted for each wavelength from a plurality of types of light emitting elements provided in a plurality of light emitting elements, and (c) detection by the light receiving element. AC / DC component ratio calculating means for calculating the ratio between the AC component and the DC component of the emitted light for each of the wavelengths; and (d) AC component calculated by the AC / DC component ratio calculating means from the emitted light detected by the light receiving element. The relationship between the DC component ratio and the distance between the light emitting element selected by the light emitting element driving circuit and the light receiving element is determined for each wavelength, and from the relationship, the optimal light emitting element is determined for each wavelength. Element determining means;
(E) prior to the detection of the photoelectric pulse wave, an optimum light emitting element selecting means for causing the light emitting element driving circuit to emit the optimum light emitting element determined for each wavelength by the optimum light emitting element determining means. .

[0008]

According to the present invention, when the plurality of types of light emitting elements provided in such a manner that the distance from the light receiving element gradually varies by the light emitting element driving circuit, the light emitting element driving circuit sequentially emits light. The emitted light scattered at different depths in the living body due to the different distances between the light-emitting element and the light-emitting element is received by the light-receiving element. For the received emitted light, the ratio between the AC component and the DC component is calculated by the AC / DC component ratio calculating means, and the ratio of the AC component to the DC component is determined by the optimum light emitting element determining means with respect to the distance between the light emitting element and the light receiving element. The optimum light emitting element is determined based on the change curve. In the state where the photoelectric pulse wave is detected to measure the biological information,
The optimal light-emitting element selected by the optimal light-emitting element selecting means emits light. The change curve of the ratio of the AC component to the DC component with respect to the distance between the light emitting element and the light receiving element changes in relation to the density of the peripheral blood vessel at the depth where the scattered light is scattered. Therefore, by determining the light emitting element having the optimum distance to the light receiving element based on the change curve, the light is radiated to the living body, scattered in the living body, and scattered at a plurality of wavelengths received by the light receiving element. The depth at which light is scattered can be automatically adjusted to the optimum depth, and the measurement accuracy of the reflection-type photoplethysmographic detector is improved.

[0009]

In another preferred embodiment of the present invention, the optimum light emission intensity determining means according to the first aspect of the present invention comprises the light emitting element drive circuit of the ratio of the AC component to the DC component calculated by the AC / DC component ratio calculating means. A curve indicating an increase rate with respect to the light emission intensity of the light emitting element changed by the above, that is, a ratio of the AC component and the DC component, and a first derivative curve obtained by differentiating the change curve of the relationship between the light emission intensity with respect to the light emission intensity are obtained. The optimum emission intensity is determined based on the emission intensity at which the rate of increase becomes equal to or less than a certain value in a range of emission intensity higher than the emission intensity showing the maximum value of the differential curve. In this way, the maximum value of the first derivative curve indicates that the scattered light of light emitted from the light emitting element is scattered at a depth where the density of peripheral blood vessels is suddenly increased, and the first derivative thereof is The point at which the rate of increase of the curve becomes a certain value or less indicates that the scattered light of light emitted from the light emitting element is scattered at a depth where the density of peripheral blood vessels is sufficiently high, so that the living body is irradiated. The depth at which the scattered light of a plurality of wavelengths scattered in the living body and received by the light receiving element is scattered can be automatically adjusted to the optimum depth, respectively, and the measurement accuracy of the reflection type photoplethysmographic detector can be improved. improves.

Preferably, the optimum light emission intensity determining means of the first invention is changed by the light emitting element drive circuit and the ratio between the AC component and the DC component calculated by the AC / DC component ratio calculating means. A change curve of the relationship with the light emission intensity of the light emitting element is obtained, and the optimum light emission intensity is determined based on the inflection point of the change curve. In this way, the inflection point of the change curve indicates that the scattered light of the light emitted from the light emitting element is scattered at a depth where the density of the peripheral blood vessels is suddenly increased. The depth at which the scattered light of a plurality of wavelengths is scattered in the living body and received by the light receiving element can be automatically adjusted to the optimum depth, respectively. Measurement accuracy is improved.

Preferably, the optimum light-emitting element determining means of the second invention is selected by the light-emitting element drive circuit from a ratio of an AC component to a DC component calculated by the AC / DC component ratio calculating means. A curve indicating the rate of increase with respect to the distance between the light-emitting element and the light-receiving element, that is, the change curve of the relationship between the ratio of the AC component and the DC component and the distance between the light-emitting element and the light-receiving element, for the distance between the light-emitting element and the light-receiving element Find the differentiated first derivative curve, and in the range where the distance between the light emitting element and the light receiving element is farther than the light emitting element showing the maximum value of the first derivative curve, the distance between the light emitting element and the light receiving element whose increase rate is equal to or less than the reference value The optimum light emitting element is determined based on the above. In this way, the maximum value of the first derivative curve indicates that the scattered light of light emitted from the light emitting element is scattered at a depth where the density of peripheral blood vessels is suddenly increased, and the first derivative thereof is The point where the rate of increase of the curve is less than the reference value indicates that the scattered light of the light emitted from the light emitting element is scattered at a depth where the density of peripheral blood vessels is sufficiently high, so that the living body is irradiated. The depth at which the scattered light of a plurality of wavelengths scattered in the living body and received by the light receiving element is scattered can be automatically adjusted to the optimum depth, respectively, and the measurement accuracy of the reflection type photoplethysmographic detector can be improved. improves.

Preferably, the optimum light emitting element determining means of the second invention is selected by the light emitting element driving circuit and a ratio of an AC component to a DC component calculated by the AC / DC component ratio calculating means. A change curve of a relationship between a light emitting element and a light receiving element is obtained, and an optimum light emitting element is determined based on an inflection point of the change curve. In this way, the inflection point of the change curve indicates that the scattered light of the light emitted from the light emitting element is scattered at a depth where the density of the peripheral blood vessels is suddenly increased. Irradiated to
The depth at which scattered light of multiple wavelengths scattered in the living body and received by the light receiving element can be automatically adjusted to the optimum depth, respectively, improving the measurement accuracy of the reflection-type photoelectric pulse wave detector. I do.

[0013]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows a configuration of a reflection type oximeter provided with a reflection type probe 10, which is a reflection type photoplethysmography device, that is, an oxygen saturation measurement device. In FIG. 1, a reflective probe 10 is mounted in close contact with a body surface 12 such as a forehead or a finger having a relatively high density of peripheral blood vessels of a living body. The reflective probe 10 has a cylindrical housing 14 having a relatively shallow bottom and a bottom inner surface of the housing 14 for detecting backscattered light which is scattered below the body surface and emitted toward the light emitting element. And a light receiving element 16 composed of a photodiode or a phototransistor, and a light receiving element 16 alternately provided at predetermined intervals on a circumference of the same radius r centered on the light receiving element 16 on the bottom inner surface of the housing 14. (Eg, 8 in this embodiment)
A first light emitting element 18 and a second light emitting element 20, a transparent resin 22 integrally provided in the housing 14 and covering the light receiving element 16 and the light emitting elements 18 and 20 to protect the light receiving element 16 and the light emitting elements 18 and 20. Are provided between the light receiving element 16 and the light emitting elements 18 and 20,
An annular light-shielding wall 24 that shields reflected light from the body surface 12 of the light emitted from 0 toward the light-receiving element 16 is provided.

The housing 14 is integrally provided with a cap-shaped rubber member 58 so as to cover the outer peripheral surface and the bottom outer surface of the housing 14. The rubber member 58 is formed in a sponge shape using, for example, chloroprene rubber or the like as a raw material, and has a suitable heat insulating property.
The portion of the rubber member 58 located on the outer peripheral side of the housing 14 is fixed to the body surface 12 via the double-sided adhesive sheet 60, so that the open end surface of the housing 14 and the distal end surface of the light shielding wall 24 are attached to the body surface. The probe 10 is mounted on the body surface 12 in close contact with the body 12. FIG.
2, the double-sided adhesive sheet 60 is drawn much thicker than it is for convenience.

The first light emitting element 18 is controlled by oxygen saturation.
First wavelength λ affected by the absorption coefficient of hemoglobin₁ Was
For example, it emits red light having a wavelength of about 660 nm,
The optical element 20 has an absorption coefficient of hemoglobin depending on the oxygen saturation.
Second wavelength λ whose number is not affected _Two For example, about 910 nm
It emits infrared light having a wavelength of In addition, the first
Wavelength λ₁ And the second wavelength λ_Two Are not necessarily at these wavelengths
The absorption of oxygenated hemoglobin is not limited to
Coefficient and the extinction coefficient of anoxic hemoglobin differ greatly.
And the wavelength at which both extinction coefficients are approximately the same
Is done.

The first light emitting element 18 and the second light emitting element 20 function as a light source. The light emitting element driving circuit 30 alternates the light emitting element 18 at a relatively high frequency of about several hundred Hz to several kHz for a certain time width. Are driven to emit light. This light emitting element drive circuit 30
The driving current supplied to the first light emitting element 18 and the second light emitting element 20, that is, the light emission intensity of the first light emitting element 18 and the second light emitting element 20
It has a function to make adjustments based on commands from the two. The first wavelength λ from the first light emitting element 18 and the second light emitting element 20 toward the living tissue (vascular bed) immediately below the body surface 12.
_When the light of _{1 and} the light of the second wavelength λ ₂ are alternately irradiated,
Since the backscattered light scattered by blood cells contained in the blood in the blood capillaries of the living tissue is emitted from the body surface 12 as reflected light, the backscattered light, that is, the reflected light from the living tissue (blood vessel bed) is generated. Each of the light receiving elements 16 functioning as a common optical sensor receives light, and outputs a first optical signal SV _R indicating scattered light of the first wavelength λ ₁ and a second optical signal SV _IR indicating scattered light of the second wavelength λ _2. It is supposed to be. These first optical signal SV _R and second optical signal SV
_{The IR} includes a direct current (DC) component and an alternating current (AC) component that fluctuates in synchronization with the heart rate as illustrated in FIG.

If the luminous intensities E ₁ and E ₂ , that is, the intensity of the light irradiated on the body surface 12 of the living body are different, the depth of penetration of the irradiated light into the living body is different, and it is compared with the irradiation of weak light. It penetrates only to a depth close to (shallow) the target body surface 12, but when irradiated with intense light, it penetrates and scatters to a part relatively deep (deep) from the body surface 12. The ranges of the light emission intensities E ₁ and E ₂ of the first light emitting element 18 and the second light emitting element 20 changed by the light emitting element driving circuit 30 depend on individual differences and the part where the reflective probe 10 is mounted. Even if the thickness is different, it is experimentally determined beforehand so that the irradiated light has a sufficient range of luminescence intensity that is mainly scattered in the dermis or subcutaneous tissue where many capillaries exist. .

The light receiving element 16 generates an optical signal SV including a first optical signal SV _R indicating backscattered light having a first wavelength λ ₁ and a second optical signal SV _IR indicating backscattered light having a second wavelength λ _2. Is output to the low-pass filter 34 via the amplifier 32. The low-pass filter 34 removes noise having a frequency higher than the frequency of the pulse wave from the input optical signal SV, and outputs the optical signal SV from which the noise has been removed to the demultiplexer 36. Since the first optical signal SV _R and the second optical signal SV _IR are optical signals that periodically change in response to the pulsation of the blood volume in the vascular bed below the body surface 12,
It is also called a so-called volume pulse signal or photoelectric pulse signal.

The demultiplexer 36 outputs a switching signal S to be described later.
C, the first light emitting element 18 and the second light emitting element 20 are switched in synchronization with the light emission, so that the first wavelength λ ₁
First optical signal SV _R a sample-and-hold circuit 38 and A / D converter 40 calculation control circuit 4 through a red light
2 to the I / O port 44 in the
The second optical signal SV _IR , which is infrared light of the wavelength λ ₂ , is input to the I / O
Supply sequentially to port 44. Sample hold circuit 3
8 and 46 convert the input optical signals SV _R and SV _IR into A / D
When sequentially outputting to the converters 40 and 48, the A / D converters 40 and 48 for the previously output optical signals SV _R and SV _IR.
The optical signals SV _R and SV _IR to be outputted next are respectively held until the conversion operation in is completed.

The I / O port 44 is connected to a CPU 50, a ROM 52, a RAM 54, and a display 56 via data bus lines. The CPU 50
Using the storage function of M54, the operation of determining the optimum light emission intensity and measuring and measuring the oxygen saturation of the first light emitting element 18 and the second light emitting element 20 are executed according to a program stored in the ROM 52 in advance. That is, the arithmetic and control unit 42
, When the start button not shown is operated, first to determine the optimum luminous intensity AE ₂ of the optimum luminous intensity AE ₁ and the second light emitting element 20 of the first light emitting element 18 by the following operation.

The arithmetic and control unit 42 outputs a drive command signal SLD from the I / O port 44 to the light emitting element driving circuit 30 so that the first light emitting element 18 and the second light emitting element 2
0 is alternately emitted at a relatively high frequency of about several hundred Hz to several kHz for a certain period of time, and is set in advance as one or several beats of a pulse in order to calculate an AC component and a DC component of a pulse wave. The light emitting element drive circuit 30 sends the first light emitting element 18 and the second light emitting element 20 every time T ₀
The current output to the first light-emitting element 18 and the second light-emitting element 20 is gradually increased, so that the light-emitting intensities E ₁ and E ₂ of the first light-emitting element 18 and the second light-emitting element 20 are gradually changed. Further, by outputting the switching signal SC in synchronization with the light emission of the first light emitting element 18 and the second light emitting element 20 and switching the demultiplexer 36, the first optical signal SVR is _sent to the sample hold circuit 38 and the second light Optical signal SV
_{The IR} is distributed to the sample hold circuit 46.

The arithmetic and control unit 42 calculates the optimum light emission of the first light emitting element 18 from the first light signal SV _R and the second light signal SV _IR affected by the change of the light emission intensity in accordance with a previously stored program. The intensity AE ₁ and the optimum emission intensity AE ₂ of the second light emitting element 20 are determined.

Subsequently, the following oxygen saturation measurement operation is performed. That is, when the drive command signal SLD is output from the I / O port 44 to the light emitting element driving circuit 30, the light emitting element driving circuit 30 transmits the optimum light emitting intensity AE ₁ to the first light emitting element 18 and the second light emitting element 20. , AE ₂ is emitted, and the first light emitting element 18 and the second light emitting element 20 are alternately caused to emit light at a relatively high frequency of about several hundred Hz to several kHz for a certain time width. The optical signal SV received by the light receiving element 16 is input to the I / O port 44 in the same manner as in the operation of determining the optimum light emission intensity.

The CPU 50 operates the first optical signal SV _R and the second optical signal SV _{IR in} accordance with a program stored in advance.
The oxygen saturation SaO ₂ in the blood flowing through the peripheral blood vessels is determined based on the photoplethysmographic waveforms respectively represented by the above and the determined oxygen saturation SaO ₂ is displayed on the display 56.

FIG. 3 is a functional block diagram for explaining a main control function of the arithmetic and control unit 42. As shown in FIG. In FIG. 3, the light emission intensity changing means 62 outputs a drive command signal SLD to the light emitting element driving circuit 30 so that the first light emitting element 18 and the second light emitting element 20 are output from the light emitting element driving circuit 30.
Gradually changing the current output, the number of emission intensity E ₁ and while changing the emission intensity E ₂ of the second light emitting element 20, which first light emitting element 18 and the second light emitting element 20 of the first light emitting element 18 Light is emitted alternately at a relatively high frequency of about 100 Hz to several kHz for a certain time width.

The frequency analysis unit 64, a high speed off - by performing a frequency analysis using Fourier transform method previously set predetermined interval, the first optical signal SV _R and the second light output from the light receiving element 16 from the signal SV _IR, the alternating current component AC _R and DC components D of the first optical signal SV _R for each the predetermined interval
The C _R and the AC component AC _IR and the DC component DC _{IR of} the second optical signal SV _IR are sequentially determined. AC component AC
_R and AC _IR are obtained as signal power (watt) of a frequency component corresponding to the pulse rate PR (1 / min) of the living body, that is, the pulse frequency PF (Hz), and the DC components DC _R and D
C _IR is obtained as signal power (watt) of a frequency component corresponding to DC. Figure 4 shows an example of the frequency spectrum of the first optical signal SV _R or the second optical signal SV _IR which is example by the frequency analysis are shown.

The AC / DC component ratio calculating means 66 includes a light receiving element 16
AC component AC of emission light detected by_R, AC_IRDirectly
Flow component DC_R, DC_IROf the wavelength λ₁, Λ_TwoEach time
Is calculated. That is, the frequency analysis means 64
The determined first optical signal SV_RAC component of_RAnd straight
Flow component DC_RAnd the second optical signal SV_IRAC component of_IRAnd
And DC component DC_IRFrom the first optical signal SV_RAlternation of
Component ratio (AC_R/ DC _R) And the second optical signal SV_IRAlternation of
Component ratio (AC_IR/ DC_IR) Is calculated. Toko
The peripheral blood vessels are hardly present in the epidermis,
Concentrated on the dermis and the underlying subcutaneous tissue
I have. The incident light is mainly scattered in the dermis or subcutaneous tissue.
Scattered light received by the light receiving element 16 due to the disturbance
Is affected by peripheral blood components,
Since the intensity changes in response to the pulsation of the peripheral blood vessels,
SV_R, SV_IRIs relatively large
You.

The optimum light emission intensity determining means 67 calculates the AC components AC _R and AC _IR and the DC components DC _R and D of the emission lights of the _two wavelengths λ ₁ and λ ₂ calculated by the AC / DC component ratio calculating means 66.
Respectively determined the relationship between the emission intensity of the light emitting elements 18 and 20 which are driven as the ratio of C _IR by a light emitting element driving circuit 30 for each wavelength, determined from the relation, respectively for each wavelength the optimum luminous intensity AE _1, AE ₂ I do. That is, the vertical AC to DC component ratio of the first optical signal SV _R which is sequentially calculated by the AC-DC component ratio calculating means 66 from the (AC _R / DC _R), AC-DC component ratio as shown in FIG. 5 (AC _R / DC _R) an axis, determined by the curve C ₁ depicted in a two-dimensional coordinate system in which the emission intensity E ₁ and the horizontal axis prior to the measurement of oxygen saturation SaO _2, the curve C ₁
To determine the optimal emission intensity AE ₁ based on the inflection point i ₁ of. For example, the light emission intensity that is higher than the light emission intensity indicating the inflection point i ₁ by a predetermined amount a is set to the optimum light emission intensity AE ₁
To be determined. Further, similarly, the second optical signal SV
Determine the curve C ₂ from the AC-DC component ratio of _{IR (AC IR / DC IR)} , to determine the optimal emission intensity AE ₂ based on the inflection point i ₂ of the curve C _2. For example, the light emission intensity that is higher than the light emission intensity indicating the inflection point i ₂ by a predetermined constant amount a is determined as the optimum light emission intensity AE ₂ .

The inflection points i ₁ and i ₂ indicate that the scattered light received by the light receiving element 16 is due to scattering at a depth where the density of peripheral blood vessels suddenly increases.
This is experimentally determined in advance in order to receive scattered light at a depth at which the density of the peripheral blood vessels, which is slightly deeper than that depth, is substantially constant.

The optimum light emission intensity adjusting means 68 detects the optimum light emission intensity A determined by the optimum light emission intensity determining means 67 prior to the detection of the photoelectric pulse wave for obtaining the oxygen saturation SaO _2.
The first light emitting element 18 and the second light emitting element 20 are caused to emit light by the light emitting element driving circuit 30 so that E ₁ and AE ₂ are obtained, and the light emission intensity is maintained. In the oxygen saturation calculating means 69, the first light signal SV is output in a state where the first light emitting element 18 and the second light emitting element 20 emit light at the optimum light emission intensities AE ₁ and AE ₂ by the optimum light emission intensity adjusting means 68. the ratio R of the AC-DC component ratio _R (AC _R / DC _R) and AC-DC component ratio of the second optical signal _{SV IR (AC IR / DC IR} ) [=
(AC _R / DC _R ) / (AC _IR / DC _IR )] are sequentially calculated, and the oxygen saturation SaO ₂ is calculated by one beat or a number based on the actual ratio R from the relationship stored in advance shown in FIG. It is calculated sequentially for each beat and displayed on the display 56.

FIG. 7 is a flowchart for explaining the main part of the operation for determining the optimum light emission intensities AE ₁ and AE ₂ of the control operation of the arithmetic and control circuit 42. In FIG. 7, SA1
By operating a start button (not shown), it is determined whether or not a start operation for measurement has been performed. If the determination at SA1 is denied, the process waits. If the determination is affirmed, after various counters and registers are cleared in an initial processing step (not shown),
In SA2, the current input to the first light emitting element 18 and the current input to the second light emitting element 20 via the light emitting element driving circuit 30 are each determined to be the initial value. Next, in SA3, the first light emitting element 18 and the second light emitting element 20 are alternately caused to emit light at a relatively high frequency of about several hundred Hz to several kHz for a certain period of time, and then in SA4, the first light signal SV _R. And the second optical signal SV _IR are read.

[0033] In subsequent SA5, after "1" is added to the contents of the timer counter CT, in SA6, whether the contents of the timer counter CT reaches a preset determination reference time T ₀ or more is determined . This judgment reference time T ₀
Is set to one or several beats of a pulse in order to calculate the AC and DC components of the optical signal SV.

Initially, the determination at SA6 is denied, so that the first optical signal SV _R and the second optical signal SV _IR are continuously read by repeatedly executing SA3 and subsequent steps. If the determination of SA6 is affirmative while the first optical signal SV _R and the second optical signal SV _IR are continuously read, the SA corresponding to the frequency analysis unit 64 is determined.
7, the frequency analysis processing is performed on the first optical signal SV _R and the second optical signal SV _IR in the unit section, respectively, so that the AC component A of the first optical signal SV _R
C _R (signal power value) and DC component DC _R (signal power value), and AC component AC _IR (signal power value) and DC component DC _IR (signal power value) of the second optical signal SV _IR are extracted. .

Next, in SA8 corresponding to the AC-DC component ratio calculating means 66, the first extracted in SA7 is used.
From the AC component AC _R and a DC component DC _R of the optical signal SV _R, AC-DC component ratio of the first optical signal SV _R (AC _R / DC
_R ) is calculated, and the AC component AC _IR and the DC component DC of the second optical signal SV _IR extracted in SA7 are calculated.
_{From the IR} , an AC / DC component ratio of the second optical signal SV _IR (AC _IR /
_DCIR ) is calculated.

SA corresponding to the following light emission intensity changing means 62
9, the drive command signal SLD is output to the light emitting element drive circuit 30 to change the light emission intensity E ₁ , E ₂ of the first light emitting element 18 and the second light emitting element 20, whereby the first
The current input to the light emitting element 18 and the second light emitting element 20 is increased by a certain amount. In the subsequent SA10, it is determined whether or not the current input to the first light emitting element 18 and the second light emitting element 20 is a preset end current of the optimum light emission intensity determining operation. Note that the constant amount of current that is increased in SA9 is a light emission intensity E that changes with a change in current.
₁ , E ₂ and the AC / DC component ratio (AC _R / DC _R ), (AC _IR
/ DC _IR ) are set such that a point interval sufficient to determine the inflection points i ₁ and i ₂ is obtained on the curves C ₁ and C ₂ obtained by plotting the points indicating the relationship with SA10 / DC _IR ). Is set high enough so that the inflection points i ₁ and i ₂ are obtained, that is, the luminescence intensity is such that the irradiated light penetrates to a depth where the density of peripheral blood vessels suddenly increases.

While the determination in SA10 is denied,
Curve C above₁ , C_Two Is the inflection point i₁, I_Two Ten to get
Since no sufficient measurement points have been obtained, SA3 and subsequent steps are repeated.
However, if affirmed, the next SA11
And a curve C as shown in FIG.₁Is the first optical signal SV_RExchange
Direct component ratio (AC_R/ DC_R) Based on the curve C
_Two Is the second optical signal SV_IRAC-DC component ratio (AC_IR/ DC_IR)
And the curve C₁ , C_Two Inflection point i₁ ,
i_Two Are required respectively.

In the subsequent SA12, the emission intensities by a predetermined amount a are determined as the optimum emission intensities AE ₁ and AE ₂ from the emission intensities indicating the inflection points i ₁ and i ₂ obtained in SA11. Therefore, in this embodiment, SA11 and SA12 correspond to the optimum light emission intensity determining means 67.

As described above, according to this embodiment, the first light emitting device 30 emits light of the first wavelength λ _{1 by} the light emitting element driving circuit 30.
The light emission intensity E ₁ and E ₂ of the light emitting element 18 and the second light emitting element 20 that emits light of the second wavelength λ ₂ are gradually changed, and the first light emitting element 18 and the second light emitting element 20 emit light. The light emitted from the light receiving element 16 is scattered at different depths in the living body due to changes in the light emission intensities E ₁ and E _2.
Is detected by The received scattered light is converted into an AC / DC component ratio (AC _R / DC _R ) by the AC / DC component ratio calculating means 66.
(AC _IR / DC _IR ) is calculated, and the optimum luminous intensity determining means 67 calculates the AC / DC component ratio (AC _R / DC _R ),
The optimum emission intensities AE ₁ and AE ₂ are determined based on the inflection points i ₁ and i ₂ of the change curves C ₁ and C ₂ with respect to the emission intensities E ₁ and E ₂ of (AC _IR / DC _IR ). Oxygen saturation SaO ₂
In a state in which the photoelectric pulse wave is detected in order to measure the first light emitting element 18 by the optimum light emission intensity adjusting means 68 is caused to emit light at the optimum light emission intensity AE _1, the second light emitting element 20 at the optimum light emission intensity AE ₂ The light is emitted and the photoelectric pulse wave is detected. The change curves C ₁ and C ₂ change in relation to the density of the peripheral blood vessels at the depth where the scattered light is scattered, and the inflection point i
_{Both 1} and i ₂ indicate that the scattered light is scattered at a depth where the density of peripheral blood vessels suddenly increases. Therefore, the depth at which the scattered light of the two wavelengths irradiated to the living body is scattered can be automatically adjusted to the optimum depth, and the measurement accuracy of the reflective probe 10 is improved.

Next, an embodiment of the second invention will be described in detail with reference to the drawings. Note that portions having the same configuration as the above embodiment are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 8 shows a configuration of a reflection type oximeter provided with a reflection type probe 70 which is a reflection type photoplethysmogram detection device, that is, an oxygen saturation measurement device. Reflective pro
The probe 70 is attached to the body surface 12 such as a forehead or a finger having a relatively high density of peripheral blood vessels of a living body, for example, similarly to the reflective probe 10 of the above-described embodiment. The reflection type probe 70 has a relatively shallow bottomed prismatic housing 72.
A first light-emitting element 18, a second light-emitting element 20, and a light-receiving element 16 provided on the inner surface of the bottom portion of the housing 72 as in the above-described embodiment; and the light-receiving element 16 and the light-emitting element provided integrally in the housing 72. A transparent resin 74 covering the light-emitting elements 18 and 20 to protect the light-emitting elements 18 and 20;
To shield part of the irradiation light from the body, reflected light of the irradiated light from the body surface 12 toward the light receiving element 16, and part of the scattered light of the irradiated light scattered in the living body and directed to the light receiving element 16. And a light-shielding wall 76 provided in the housing 72.

FIG. 9 shows that the reflection type probe 70 is connected to the body surface 12.
FIG. 9, the light receiving element 16 is fixed to one end in the longitudinal direction of the inner surface of the bottom of the housing 72, and the distance between the plurality of first light emitting elements 18 and the second light emitting elements 20 gradually increases from the light receiving element 16 respectively. As described above, the reflection type probes 70 are fixed at equal intervals in the longitudinal direction. The light shielding wall 76 is provided between the light receiving element 16 and the first light emitting element 18 and the second light emitting element 20 closest to the light receiving element 16 and between the one set of light emitting elements 18 and 20 and the other set of light emitting elements 18 and 20. It is provided in. In the present embodiment, the first light emitting element 18 and the second light emitting element 20
Six light emitting elements are provided for convenience of drawing, however, as long as the light emitting elements 18 and 20 can be accommodated in the bottom inner surface of the housing 72, more light emitting elements 18 and 20 may be used, or the number may be smaller than six. .

Referring back to FIG. 8, when the measurement start button (not shown) is activated, the first light emitting element 18 and the second
The light emitting element 20 emits light when driven by the light emitting element drive circuit 78. This light emitting element drive circuit 7
Reference numeral 8 has a function of selectively emitting light from the light-emitting elements 18 and 20 to be emitted for each of the wavelengths λ ₁ and λ ₂ from among the plurality of first light-emitting elements 18 and second light-emitting elements. That is, the light-emitting element driving circuit 78 continuously drives the first light-emitting elements 18 from the side closest to the light-receiving element 16 to the side farthest from the light-receiving element 16 continuously for a certain period of time T ₁ according to the drive command signal SLD from the arithmetic control circuit 42. Then, the second light emitting element 20 emits light continuously for a certain time T ₁ from the side closest to the light receiving element 16 to the side farthest from the light receiving element 16.
Here, the fixed time T ₁ is a time for calculating the AC component and the DC component of the pulse wave, and the time T ₁ in the above-described embodiment.
_{As in the case of 0} , it is set to one beat or several beats of the pulse.

When the first light emitting element 18 and the second light emitting element 20 emit light, the scattered light from inside the living tissue (blood vessel bed) is received by the light receiving element 16 and the first wavelength λ _1.
Optical signal SV _R and second optical signal SV indicating the scattered light of
_IR is output. First optical signal SV _R and the second optical signal S
Optical signal SV and a V _IR includes an amplifier 32, B - pass filter 34, a demultiplexer 36, a sample-- hold circuit 38, 46, I of the arithmetic and control circuit 42 via the A / D converter 40, 48 / O port 44 are sequentially supplied.

Here, the light shielding wall 76 and the light emitting elements 18 and 20
The relationship between the distance from the light-emitting elements 18 and 20 to the light-receiving element 16 and the scattering depth of the scattered light received by the light-receiving element 16 will be described. FIG. 10 shows A in FIG.
It is sectional drawing of the -A line. The reflective probe 70 shown in FIG. 10 is shown without the transparent resin 74. In FIG. 10, the intersection P ₁ is the light emitted from the first light emitting element 18 arranged on the side closest to the light receiving element 16,
The scattered depth is shown when the light is scattered at a position closest to the body surface 12, that is, the lightest part, and is received by the light receiving element 16. Similarly, the intersection points P ₂ , P ₃ , P ₄ , P ₅ ,
P ₆ also indicates the depth at which the light emitted from each of the first light emitting elements 18 is scattered from the body surface 12 at the shallowest part and is received by the light receiving element 16.

That is, when the light receiving element 16 receives the scattered light of the light emitted by the light emitting elements 18 and 20 arranged at the closest distance to the light receiving element 16, the light from the part close to the body surface 12 (shallow). While receiving a lot of scattered light,
Light-emitting element 1 arranged farthest from light-receiving element 16
When the light receiving element 16 receives the scattered light of the light emitted by 8 and 20, the scattered light scattered at a portion near the body surface 12 is not received because it is shielded by the light shielding wall 76. Therefore, scattered light scattered at a portion relatively far (deep) from the body surface 12 is received relatively more.

The light received by the light receiving element 16 is the body surface 1
The distance from the light receiving element 16 to the light emitting elements 18 and 20 and the light emitting element 1
The distance is determined by the distance between the light-shielding wall 76 and the light-receiving element 16, and the distance between the light-emitting elements 18 and 20 and the body surface 12. The distance between the light receiving element 16 and the light emitting elements 18 and 20, the distance between the light emitting elements 18 and 20 and the light shielding wall 76, the distance between the light receiving element 16 and the light shielding wall 76, and the height of the light shielding wall 76 are scattered light. Is determined experimentally in advance so that the scattered light from the peripheral vascular bed under the body surface 12 can be sufficiently detected, for example, so that the shallowest detection depth changes in a range from 0.3 mm to 2.0 mm.

The light of the first wavelength λ _{1 and} the light of the second wavelength λ which are emitted at different distances from the light receiving element 16 respectively.
First optical signal SV _R and the second optical signal SV _IR showing the scattered light from in the _second optical vivo I / O port - the output to preparative 44, the arithmetic and control unit 42, a program stored in advance , The first light emitting element 18 and the second light emitting element 2
The optimum light emitting elements of 0 are respectively determined.

Subsequently, a drive command signal SLD is output to the light emitting element driving circuit 78 to drive the first light emitting element 18 determined as the optimum light emitting element and the second light emitting element 20 also determined as the optimum light emitting element to several hundred Hz. To a relatively high frequency of about several kHz, the oxygen saturation is continuously determined based on the scattered light at the optimum depth, and the determined oxygen saturation SaO is obtained.
₂ is displayed on the display 56.

FIG. 11 is a functional block diagram for explaining a main control function of the arithmetic and control unit 42. In FIG. 11, the light emitting element selecting means 80 outputs a drive command signal SLD to the light emitting element driving circuit 78, and the light emitting element driving circuit 78
, Based on the drive command signal SLD, the first light-emitting element 18 continuously for a predetermined time T ₁ at a time emission in order to farthest from the side closest to the light receiving element 16, then the second light emitting element 20 light-receiving element 16 continuously for a predetermined time T ₁ at a time emission in order to farthest from the side closest to the. Note that, as the distance between the light receiving element 16 and the light emitting elements 18 and 20 increases, the amount of light received by the light receiving element 16 decreases. Therefore, the light emission intensity is set to increase as the distance from the light receiving element 16 increases. Is also good.

When the scattered light is received by the light receiving element 16, the first optical signal SV output from the light receiving element 16 is output.
_R, the second optical signal SV _IR, like the above-described embodiment, the frequency analysis means 64, the alternating current component AC _R, AC _IR and DC component DC _R, DC _IR is determined, in AC-DC component ratio calculating means 66 , AC to DC component ratio of the first optical signal SV _R (a
C _R / DC _R ) and the alternating-current component ratio (A) of the second optical signal SV _IR
CIR / _DCIR ) is calculated.

The optimum light emitting element determining means 82 calculates the AC / DC component ratio.
The AC-DC component ratio (AC_R/ D
C_R), (AC_IR/ DC_IR) And the light emitting element drive circuit 78
Of the light emitting elements 18 and 20 selected from
Wavelength λ₁, Λ _TwoAsked each time, whether the relationship
The wavelength λ₁, Λ_TwoDetermine the optimal light-emitting element for each
You. That is, in the optimum light emitting element determining means 82, FIG.
(A) As shown in FIG.
Optical signal SV sequentially calculated by_RAC component ratio of
(AC_R/ DC_R) Or the second optical signal SV_IRAlternation of
Division ratio (AC_IR/ DC _IR), Light emitting elements 18 and 20 and light receiving
Curve C showing the rate of increase with respect to the distance to the element 16_ThreeBut
It is calculated in advance and its curve C_ThreeLight-emitting element 1 showing the maximum value of
The distance between the light receiving element 16 and the light receiving element 16 is larger than the distance between the light receiving element 16 and the light receiving element 16.
In a range where the distance of
The distance between the light emitting elements 18 and 20 having the quasi-value B and the light receiving element 16
The separation D is obtained, and the light receiving element
Light-emitting elements 18 and 20 whose distance from the element 16 is closest to the distance D
Is determined as the optimum light emitting element.

The reference value B is experimentally determined in advance as a relatively low value for judging that the depth at which the irradiated light is scattered is a depth at which the density of the peripheral blood vessels becomes almost constant. . FIG. 12B shows the AC / DC component ratio (AC
_R / DC _R ), (AC _IR / DC _IR ), the light emitting element 18,
12A is a curve showing the relationship between the distance between the light-emitting element 20 and the light-receiving element 16, and FIG.
It can also be obtained as a first derivative curve obtained by differentiating the distance between 8, 20 and the light receiving element 16.

The optimum light emitting element selecting means 83 is provided with a light emitting element driving circuit after the optimum light emitting element is determined by the optimum light emitting element determining means 82 prior to the collection of the photoelectric pulse wave for detecting the oxygen saturation SaO _2. Drive command signal SLD at 78
By outputting several hundred Hz to several kHz continuously.
The first light emitting element 18 and the second light emitting element 20 which are determined as the optimum light emitting elements for a certain period at a relatively high frequency are made to emit light. The oxygen saturation calculating means 69 calculates the first and second light emitting elements 18 and 20 in the state where the optimum light emitting elements of the first light emitting element 18 and the second light emitting element 20 are caused to emit light by the optimum light emitting element selecting means 83. AC-DC component ratio of the first optical signal SV _R and (AC _R / DC _R) second
Ratio R of optical signal SV _IR to AC / DC component ratio (AC _IR / DC _IR )
Based on [= (AC _R / DC _R ) / (AC _IR / DC _IR )], for example, the oxygen saturation SaO ₂ is sequentially calculated based on the actual ratio R from the relationship stored in advance shown in FIG. ,
It is displayed on the display 56.

FIG. 13 shows the operation control circuit 42 of this embodiment.
The main part of the control operation that determines the optimal light emitting element
This is a flowchart for explanation. In SB1, SA1 and
Similarly, it is determined whether or not a start operation has been performed.
If the answer is no, the game is made to wait.
In this case, after the initial processing similar to SA1 is performed,
In SB2, the light emitting element drive from the arithmetic control circuit 42
When drive command signal SLD is output to circuit 78,
The first light emitting element 18 closest to the light receiving element 16
Fixed time T₁ Only emits light continuously and smells SB3
And the first optical signal SV _RIs read.

At SB4, it is determined whether or not the first light emitting element 18 emitted at SB2 is the first light emitting element 18 farthest from the light receiving element 16. Initially, this determination is denied, so that SB2 and the subsequent steps are repeated after the first light emitting element 18 that is caused to emit light in SB5 is switched. That is, in SB5, the first light emitting element 18 to be emitted next time is one light receiving element 16 more than the first light emitting element 18 to be emitted last time in SB2.
After the setting of the first light emitting element 18 arranged on the side farther from SB2, SB2 and subsequent steps are repeated.

However, if the determination at SB4 is affirmative, it means that all the first light-emitting elements 18 have been made to emit light.
To SB5 are performed for the second light emitting element 20. That is, in SB6, the light receiving element 1
6 the second light emitting device 20 nearest the side is allowed to a certain time T ₁ emits, at SB7, the second optical signal SV _IR are read. Then, in SB8, it is determined whether the position of the second light emitting element 20 in SB6 is the second light emitting element 20 farthest from the light receiving element 16. If the determination in SB8 is denied, the process proceeds to SB9. The element to emit light is switched to a side farther from the light receiving element 16 by one, and SB6 and subsequent steps are repeated. In this embodiment, SB
2, SB4, SB5, SB6, SB8, and SB9 correspond to the light emitting element selection means 80.

However, if the determination in SB8 is affirmative, it means that all the second light emitting elements 20 have been lit, so that the SB
In 10, in the same manner as in SA7, for each of the light emitting elements 18 and 20, the alternating current component AC _R of the first optical signal SV _R
The DC component DC _R and the AC component AC _IR and the DC component DC _{IR of} the second optical signal SV _IR are extracted. In SB11 corresponds to the subsequent AC-DC component ratio calculating means 66, AC-DC component ratio of the first optical signal SV _R in the same manner as SA8 (AC _R / D
C _R ) and the AC / DC component ratio of the second optical signal SV _IR (AC _IR /
_DCIR ) is calculated.

[0059] In subsequent SB12, as shown in FIG. 12 (a), a first light emitting element 18 and the light receiving element 16 of the AC-DC component ratio of the first optical signal SV _R calculated in SB11 (AC _R / DC _R) Curve showing the rate of increase with respect to the distance between, and the ratio of the AC-DC component of the second optical signal SV _IR (AC _IR / DC _IR )
The curve showing the rate of increase with respect to the distance between the second light-emitting element 20 and the light-receiving element 16 is calculated.
In the calculated increase rate curves, in the range where the distance to the light receiving element 16 is farther than the distance between the light emitting elements 18 and 20 showing the maximum value and the light receiving element 16, the light emission at which the increase rate becomes the reference value B is obtained. Elements 18, 20 and light receiving element 16
Are determined respectively.

At SB14, the optimum light emitting element of the first light emitting element 18 and the optimum light emitting element of the second light emitting element 20 are determined based on the distance D determined at SB13. For example, the light emitting element 1 whose distance to the light receiving element 16 is closest to the distance D within a range where the increase rate is equal to or less than the reference value B.
8, 20 are determined as the optimum light emitting elements, respectively. Therefore, in this embodiment, SB12, SB13, and SB14 correspond to the optimum light emitting element determining means 82.

As described above, according to this embodiment, the light-emitting element driving circuit 78 causes the two types of light-emitting elements 18 and 20 provided in such a manner that the distance from the light-receiving element 16 gradually changes, respectively. When the light is emitted, the emitted light scattered at different depths in the living body is received by the light receiving element 16 due to the different distances between the light receiving element 16 and the light emitting elements 18 and 20. The received outgoing light is converted by the AC / DC component ratio calculating means 66 into AC components AC _R , AC _IR and DC components DC _R , the ratio of DC _IR (AC _R / DC _R ), (AC _IR
/ DC _IR ), and the optimum light emitting element determining means 82 calculates the ratio (AC _R / D) of the AC component to the DC component.
C _R), (the AC _IR / DC _IR), a first derivative curve of change curve with respect to the distance between the light emitting element 18 and the light receiving element 16, AC-DC component ratio _{(AC R / DC R),} (AC IR / D
A curve showing the rate of increase of C _IR ) with respect to the distance between the light-emitting elements 18 and 20 and the light-receiving element 16 is obtained, and the light-receiving amount is larger than the distance between the light-emitting elements 18 and 20 and the light-receiving element 16 showing the maximum value of the first derivative curve. The light-emitting elements 18 and 20 and the light-receiving element 16 whose increase rate is equal to or less than the reference value B in a range where the distance to the element 16 is long.
The optimum light-emitting element has been determined based on the distance from.

Accordingly, the maximum value of the first derivative curve indicates that the scattered light of the light emitted from the light emitting elements 18 and 20 is scattered at a depth where the density of the peripheral blood vessels suddenly increases. The point at which the rate of increase of the first derivative curve is equal to or less than the reference value indicates that the scattered light of the light emitted from the light emitting elements 18 and 20 is scattered at a depth where the density of peripheral blood vessels is sufficiently high. Therefore, it is possible to automatically adjust the depth at which the scattered light of the two wavelengths illuminated into the living body, scattered in the living body and received by the light receiving element is automatically adjusted to the optimum depth, respectively. -The measurement accuracy of the probe 10 is improved.

While the embodiment of the present invention has been described with reference to the drawings, the present invention can be applied to other embodiments.

For example, FIG.
In the embodiment, the optimum emission intensity AE ₁, AE_TwoAsk for
The emission intensity E₁, E_TwoAnd the AC / DC component ratio (AC_R/ D
C_R), (AC_IR/ DC_IR) And relationship curve C₁, C_TwoTo
Calculated and its curve C₁, C_TwoInflection point i₁, I_TwoBased on
And the optimal emission intensity AE₁, AE_TwoIs determined respectively
However, the optimum light emitting element is determined in the embodiment of the second invention.
Similarly, the AC-DC component ratio (AC_R/ DC_R), (A
C_IR/ DC_IR) And emission intensity E₁, E_TwoChange song with relationship
Derivative curve of the line, that is, the AC / DC component ratio (AC_R/ D
C_R), (AC_IR/ DC_IR) Emission intensity E₁, E_TwoTo
The optimum emission intensity is calculated based on the
May be determined.

Further, in the embodiment of FIG. 8 for the second invention described above, the AC / DC component ratio (AC _R / DC _R ), (AC _IR
/ DC _IR ), the optimum light emitting elements were determined based on the curve C ₃ indicating the rate of increase of the distance between the light emitting elements 18 and 20 and the light receiving element 16. Similarly, the relationship curve between the AC / DC component ratio (AC _R / DC _R ) and (AC _IR / DC _IR ) and the distance between the light emitting elements 18 and 20 and the light receiving element 16 is calculated, and the curve of the curve is calculated. The optimum light emitting element may be determined based on the inflection point.

Further, in the embodiment of FIG. 1 for the first invention described above, the optimum emission intensity determining means 68 determines the inflection point i.
_1, i ₂ emission intensity E ₁ showing a has been determined a strong emission intensity by a predetermined amount a from E ₂ as an optimum luminous intensity AE _1, AE _2, the emission intensity E showing the inflection point i _1, i _{2 1,} E ₂
May be determined as the optimum emission intensities AE ₁ and AE ₂ .

In the above two embodiments, the reflection probes 10 and 70 are used for measuring the oxygen saturation, but they may be used for a hematocrit value measuring device for measuring a hematocrit value.

In the above two embodiments, the scattered light of the light emitted from the two types of light emitting elements 18 and 20 is received by the common light receiving element 16, but only a single wavelength is received. May be provided corresponding to the respective wavelengths. In this case, the first light emitting element 18 and the second light emitting element 20 do not need to emit light alternately, but may emit light at the same time.

Further, the embodiment of FIG.
In the example, the drive command signal SLD from the arithmetic control circuit 42 is
The first light emitting element 18 is received by the received light emitting element drive circuit 78.
Are emitted sequentially from the side closest to the light receiving element 16 to the side farthest away.
Light, and the second light emitting element 20
Light was emitted in order from the closest side to the farthest side
Is the distance between the light emitting elements 18 and 20 and the light receiving element 16 and
Component ratio (AC_R/ DC _R), (AC_IR/ DC_IR) Is clear
If so, the light may be emitted in another order.

Also, in the embodiment of FIG. 8 for the second invention described above, the first light emitting element 1 is longitudinally attached to the reflection type probe 70 so that the distance from the light receiving element 16 is gradually different.
8 and the second light-emitting element 20 are arranged, but a plurality of light-shielding walls are provided concentrically around the light-receiving element 16, and the light-emitting element 18 is provided between the plurality of provided light-shielding walls. , 20 may be arranged in a ring shape so that the distance from light receiving element 16 gradually varies.

In the embodiment of FIG. 8 for the second invention described above, the light-shielding wall 76 is provided for each of the pair of light-emitting elements 18 and 20, but the light-receiving element 16 and the light-emitting element closest to the light-receiving element 16 are arranged. A relatively large light-shielding wall 8 between the elements 18 and 20
By providing the light-receiving element 4, the scattering depth of the scattered light received by the light-receiving element 16 may be changed. For example, a reflective probe 86 as shown in FIG.
May be used. FIG. 14 is a sectional view of the reflective probe 86 taken along a line similar to the line AA in FIG. In the case of this reflective probe 86, to obtain a detection range similar to that of the reflective probe 70 of the above-described embodiment, the entire probe 86 becomes large, but only one light shielding wall 84 is used. Thus, there is an advantage that the structure of the probe 86 is simplified. In this case, the scattered light of the light from the light emitting elements 18 and 20 farthest from the light receiving element 16 includes the scattered light from the portion shallowest from the body surface 12.

The present invention can be variously modified without departing from the gist of the present invention.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an oxygen saturation measuring apparatus provided with a reflective probe according to an embodiment of the first invention of the present invention.

FIG. 2 is a diagram illustrating a periodic fluctuation of a photoelectric pulse wave signal detected by a light receiving element.

FIG. 3 is a functional block diagram for explaining a main part of a control function of the arithmetic and control unit according to the embodiment of FIG. 1;

FIG. 4 is a diagram showing a first example analyzed by the frequency analysis means of FIG. 3;
AC component AC _{R of} optical signal SV _R or second optical signal SV _IR
Alternatively, it is a diagram showing AC _IR and DC component DC _R or DC _IR .

FIG. 5 is a diagram showing a relationship curve between the light emission intensity and the AC / DC component ratio obtained by the optimum light emission intensity determination means in FIG. 3;

FIG. 6 is a diagram showing a relationship used in the oxygen saturation calculating means of FIG. 3;

FIG. 7 is a flowchart illustrating a main part of an operation for determining an optimum light emission intensity among control operations of the arithmetic and control unit of the embodiment of FIG. 1;

FIG. 8 is a block diagram showing a configuration of an oxygen saturation measuring apparatus provided with a reflective probe according to one embodiment of the second invention of the present invention.

9 is a view of the reflective probe of FIG. 8 as viewed from a side facing a body surface of a living body.

FIG. 10 is a diagram showing a relationship between a distance between a first light emitting element and a light receiving element in the embodiment of FIG. 8 and a scattering depth of emitted light received by the light receiving element.

FIG. 11 is a functional block diagram illustrating a main part of a control function of the arithmetic and control unit according to the embodiment of FIG. 8;

FIG. 12 is a diagram showing an increasing rate of an AC / DC component ratio obtained by the optimum light emitting element determining means in FIG. 11 with respect to a distance between the light emitting element and the light receiving element.

FIG. 13 is a flowchart illustrating a main part of an operation of determining an optimal light emitting element among control operations of the arithmetic and control unit of the embodiment in FIG. 8;

FIG. 14 is a sectional view of a reflective probe according to another embodiment of the second invention, taken along a line similar to the line AA in FIG. 9;

[Description of sign]

10, 70, 86: Reflective probe (reflective photoelectric pulse wave detector) 16: Light receiving element 18: First light emitting element 20: Second light emitting element 24, 76, 84: Light shielding wall 30, 78: Light emitting element Driving circuit 62: Emission intensity changing means 66: AC / DC component ratio calculating means 67: Optimal emission intensity determining means 68: Optimal emission intensity adjusting means 80: Light emitting element selecting means 82: Optimal light emitting element determining means 83: Optimal light emitting element selecting means

Claims (2)

[Claims] 1. A housing, a plurality of types of light emitting elements housed in the housing, and irradiating light of a plurality of wavelengths toward the epidermis of a living body, and a predetermined number of light emitting elements within the housing via a light shielding wall. A light receiving element that is received at a distance and receives light of a plurality of wavelengths emitted from the body surface after light from the plurality of light emitting elements is scattered under the surface of the living body subcutaneously; A reflection-type photoelectric pulse wave detection device for detecting photoelectric pulse waves for obtaining biological information based on emission lights of different wavelengths, wherein a drive current is sequentially supplied to the plurality of types of light emitting elements, and the light emission is performed. A light emitting element driving circuit capable of adjusting the light emission intensity of each of the elements, and an AC / DC component ratio calculating means for calculating a ratio between an AC component and a DC component of the emitted light detected by the light receiving element for each of the wavelengths. The relationship between the ratio between the AC component and the DC component calculated by the AC / DC component ratio calculating means from the emission light detected by the light receiving element and the emission intensity of the light emitting element driven by the light emitting element driving circuit is obtained for each wavelength. From the relationship, an optimal emission intensity determining means for determining an optimal emission intensity for each of the wavelengths, and prior to the detection of the photoelectric pulse wave, the light emitting element with an optimal emission intensity determined by the optimal emission intensity determining means A reflection type photoelectric pulse wave detecting device, comprising: a driving circuit; and an optimum light emission intensity adjusting means for causing each of the plurality of types of light emitting elements to emit light. 2. A plurality of types of light-emitting elements for irradiating light of a plurality of types of wavelengths toward the epidermis of a living body, and light emitted from the plurality of types of light-emitting elements is housed at a predetermined distance from the light-emitting elements. A light-receiving element that receives light of a plurality of wavelengths emitted from the body surface by being scattered under the body surface subcutaneously, and a photoelectric pulse wave for obtaining biological information based on the light of the plurality of wavelengths Respectively, wherein the plurality of types of light emitting elements and the light receiving elements are housed with a light shielding wall interposed therebetween, and provided for each of a plurality of types of wavelengths. A plurality of light emitting elements, a housing provided so that the distance between the light receiving elements is gradually different, and a plurality of types of light emitting elements provided in the housing to emit light for each wavelength. Select light emitting element A light-emitting element driving circuit capable of emitting light to the light-emitting element; an AC / DC component ratio calculating means for calculating a ratio between an AC component and a DC component of the emitted light detected by the light receiving element for each of the wavelengths; The relationship between the ratio of the AC component and the DC component calculated from the emitted light by the AC / DC component ratio calculation unit and the distance between the light-emitting element and the light-receiving element selected by the light-emitting element drive circuit is determined for each wavelength, From the relationship, optimal light emitting element determining means for determining an optimal light emitting element for each wavelength, and prior to the detection of the photoelectric pulse wave, the optimal light emitting element determined for each wavelength by the optimal light emitting element determining means, Optimal light emitting element selecting means for causing the light emitting element driving circuit to emit light,
A reflection-type photoplethysmographic detector characterized by including: