JP2010136921A - Measuring apparatus - Google Patents

Abstract

In a measuring apparatus for measuring biological information using reflected light, the influence of deviation of a measuring object is reduced while reducing the number of parts as compared with the related art.
A CPU 171 causes an irradiation unit 11 in an initial arrangement to emit light and causes a light receiving unit 12 to receive reflected light. An electrical signal corresponding to the intensity of the reflected light received by each light receiving element 120 is generated by the light receiving unit 12, converted into a digital value via the amplifier circuit 177, the demodulator circuit 178 and the A / D converter 179, and sent to the CPU 171. Is output. CPU171 correct | amends each digital value according to the distance from the light source point of the irradiation part 11 to each reflection point, selects the smallest value from them, and specifies the corresponding light receiving element 120. FIG. Then, the CPU 171 moves the irradiation unit 11 so that the irradiation unit 11 approaches the identified light receiving element 120 and then causes the irradiation unit 11 to emit light. Based on the electrical signal output by the identified light receiving element 120, Measure blood oxygen saturation.
[Selection] Figure 4

Description

  The present invention relates to a measuring apparatus that measures biological information using reflected light.

As an example of a measurement device that measures biological information using reflected light, a blood sample is irradiated with light by a light emitting element, and the reflected light reflected from the blood sample is received by a light receiving element, and blood oxygen saturation level There is a device that measures the above (for example, Patent Document 1). Such an apparatus measures blood oxygen saturation of an artery of a living body by applying a light emitting element and a light receiving element to a measurement site such as a fingertip, an arm, or an ear without invading the living body. However, measurement may not be possible if the light emitting element or the light receiving element is displaced from the artery when these are applied to the measurement site. In addition, the position of the artery may change due to disturbances such as movements in daily life. Patent Document 2 describes a measurement device that responds in real time to positional deviations of sensor modules (light emitting elements and light receiving elements).
JP-A-63-92335 JP 2006-271896 A

However, the measuring device of Patent Document 2 has to be provided with a plurality of light emitting elements and light receiving elements, which increases the manufacturing cost.
The present invention has been made in view of the above-described background, and in a measurement apparatus that measures biological information using reflected light, the number of components is reduced as compared with the conventional technique, and the influence of deviation of a measurement object is reduced. For the purpose.

In order to solve the above-described problems, a measuring apparatus according to the present invention includes a movable irradiating unit that irradiates light on a surface of a living body, and a light that is arranged along the surface of the living body and irradiated by the irradiating unit A plurality of light receiving means for receiving reflected light and outputting signals corresponding to the received light intensity, and signals output from the plurality of light receiving means for receiving reflected light of the light emitted by the irradiation means Based on the received light intensity, the specifying means for specifying one light receiving means from the plurality of light receiving means, and moving the irradiation means so that the irradiation means approaches the one light receiving means specified by the specifying means Based on a signal output from the one light receiving means that receives the reflected light of the light emitted by the irradiation means moved by the movement control means and the movement control means. Characterized by comprising a biometric information generating means for generating a biometric information.
Thereby, the measuring apparatus according to the present invention can reduce the influence of the deviation of the measurement object while reducing the number of parts as compared with the related art.

Preferably, the specifying unit compares the received light intensity indicated by each signal output from the plurality of light receiving units with a threshold value, and the light receiving unit that outputs the signal indicating the received light intensity that is weaker than the threshold value, It may be specified as a light receiving means.
As a result, the measuring apparatus according to the present invention can reduce the influence of the shift of the measurement object and reduce the number of parts compared to the conventional one, and can ensure the intensity of reflected light sufficient for measurement.

Preferably, the specifying unit specifies a light receiving unit that outputs a signal indicating the weakest received light intensity among the signals output from the plurality of light receiving units as the one light receiving unit.
As a result, the measurement apparatus according to the present invention can perform measurement in a state most suitable for measurement while reducing the influence of deviation of the measurement object while reducing the number of parts as compared with the related art.

Preferably, the specifying unit corrects and corrects each signal output from the plurality of light receiving units according to a distance between each light receiving unit and the irradiation unit at the predetermined position. The one light receiving means may be specified from the plurality of light receiving means based on the respective signals.
As a result, the measuring apparatus according to the present invention reduces the influence of the deviation of the measurement object after eliminating the influence due to the difference in each distance from the irradiation means to the plurality of light receiving means while reducing the number of parts compared to the conventional one. can do.

The best mode for carrying out the present invention will be described. Here, the measurement apparatus 1 which is an example of the measurement apparatus according to the present invention will be described.
[Embodiment]
(1. Configuration)
FIG. 1 is a diagram showing an external appearance of a measuring apparatus 1 according to an embodiment of the present invention in use. As shown in FIG. 1, the measuring device 1 is a rectangular parallelepiped device. In FIG. 1, the surface of the housing 10 of the measuring apparatus 1 that is farthest from the arm 3 when worn is called a front plate 101, and the surface (not shown) that faces the front plate 101 and contacts the arm 3 when worn is the back plate. 102. The measuring device 1 is connected to a band 2, and the back plate 102 of the measuring device 1 is fixed toward a predetermined measurement site of the arm 3 by winding the band 2 around the wrist of the arm 3. Moreover, when it fixes in this way, the side plate close | similar to an upper arm among the side plates of the measuring apparatus 1 is called the side plate 103, and the side plate close | similar to a finger is called the side plate 104.
The front plate 101 of the measuring apparatus 1 is provided with an operation unit 18 constituted by a plurality of buttons and the like, and a display unit 19 for displaying measurement values by a 7 segment display, a dot matrix display or the like. Details of the operation unit 18 and the display unit 19 will be described later. The positional relationship between the measuring apparatus 1 and the artery of the arm 3 varies as the band 2 wound around the wrist is displaced in the direction of the arrow D11 or the arrow D12 shown in FIG.

FIG. 2 is a diagram for explaining the internal configuration of the measuring apparatus 1. The irradiating unit 11 is an example of a movable irradiating unit that irradiates light on the surface of a living body, and two light emitting elements 110a and 110b that irradiate monochromatic light of two different wavelengths λa and λb, respectively (see FIG. 2 (not shown). These light emitting elements are, for example, LEDs (Light Emitting Diodes). The monochromatic light having the wavelength λa irradiated by the light emitting element 110a is red light, and the wavelength λa is, for example, 660 nm. The monochromatic light of wavelength λb irradiated by the light emitting element 110b is infrared, and the wavelength λb is 900 nm, for example. Here, blood oxygen saturation is defined as the ratio of hemoglobin dioxide concentration to the total hemoglobin concentration in blood. Absorbance ratio between hemoglobin dioxide, which is hemoglobin bonded to oxygen, and hemoglobin not bonded to oxygen, when receiving red light with wavelength λa = 660 nm and when receiving infrared light with wavelength λb = 900 nm Therefore, the measuring apparatus 1 calculates the blood oxygen saturation based on the difference in absorbance ratio.
In addition, when the light irradiated by the irradiation unit 11 is irradiated to a part where the artery does not pass, the degree of absorption is low compared to the case where the part where the artery passes is irradiated. Therefore, the reflected light reflected by the part where the artery does not pass becomes light whose intensity is stronger than the reflected light reflected by the part where the artery passes.

  The positions of the light sources of the light emitting element 110a and the light emitting element 110b are close enough to be considered to be substantially the same as the dimensions of the measuring device 1. The irradiation unit 11 is fixed to the pedestal 140. The pedestal 140 is moved in the direction of the arrow D2 or in the opposite direction by the power transmission unit 141 provided along the side plate 103 with the irradiation unit 11 when the driving unit 142 having a stepping motor or the like is driven. . The pedestal 140, the power transmission unit 141, and the drive unit 142 are components of the moving unit 14 that moves the irradiation unit 11. The components of the moving unit 14 may be any motion transmission mechanism. For example, the drive unit 142 may be a pulley, and the power transmission unit 141 may be a belt wound around the pulley. In this case, the belt may move as the pulley rotates, and the pedestal 140 connected to the belt may move in the direction of arrow D2 or in the opposite direction. Alternatively, a rail may be arranged instead of the power transmission unit 141, a wheel moving on the rail may be arranged on the pedestal 140, and the wheel may be rotated by the driving unit 142 built in the pedestal 140. Further, a rack may be used instead of the rail, and a pinion may be used instead of the wheel.

The light receiving unit 12 includes five light receiving elements 120a to 120e formed of phototransistors or the like. Hereinafter, when it is not necessary to distinguish each of the light receiving elements 120a to 120e, these are collectively referred to as “light receiving element 120”. These light receiving elements 120 are arranged at equal intervals on a side plate 104 that is a side plate facing the side plate 103. Therefore, the light receiving elements 120 are arranged along the surface of the living body. In the back plate 102 of the housing 10, irradiation ports 16 a to 16 e are provided in the vicinity of the respective light receiving elements 120. Hereinafter, when there is no need for distinction, these are collectively referred to as “irradiation port 16”.
3 is a cross-sectional view taken along line III-III in FIG. The irradiation port 16 is an opening provided in the back plate 102. The red light and infrared rays emitted from the irradiation unit 11 are reflected by the surface of the arm 3 through the irradiation ports 16 along the optical path Bm0 shown in FIG. 3, and this reflected light is reflected by the optical path Bm1 shown in FIG. Are received by the respective light receiving elements 120 arranged in the vicinity of the respective irradiation openings 16.

  The shielding plate 13 is a plate-like member that shields red light and infrared rays emitted from the irradiation unit 11 from being directly received by the light receiving element 120. The shielding plate 13 extends from the front plate 101 of the housing 10 toward the back plate 102. Thereby, as shown in FIG. 3, among the red light and the infrared rays irradiated from the irradiation unit 11, only the reflected light that passes through the irradiation port 16 and is reflected by the surface of the arm 3 is received by the light receiving element 120. Each light receiving element 120 outputs a signal corresponding to the received light intensity of the received reflected light. That is, the light receiving element 120 is an example of a plurality of light receiving units that are arranged along the surface of the living body, receive the reflected light of the light irradiated by the irradiation unit 11, and output a signal corresponding to the received light intensity. is there.

In addition to the operation unit 18 and the display unit 19 described above, the front plate 101 of the housing 10 is provided with a control unit 17 that controls them.
FIG. 4 is a block diagram for explaining the control unit 17. A CPU (Central Processing Unit) 171 of the control unit 17 controls each unit of the measuring apparatus 1 by reading a computer program stored in a ROM (Read Only Memory) 172 into a RAM (Random Access Memory) 173 and executing it. To do. The ROM 172 is a read-only nonvolatile storage device and stores the above-described computer program. The RAM 173 is a readable / writable storage device including semiconductor elements and is used as a work area when the CPU 171 executes a program. The storage unit 174 is a rewritable nonvolatile storage device such as a flash memory, for example, and stores measurement values and the like under the control of the CPU 171. In addition, when all the contents stored in the storage unit 174 are stored in the RAM 173, the storage unit 174 may be omitted.

  The timer built in the CPU 171 includes an oscillation circuit having a crystal resonator, and measures time based on a transmission signal output from the oscillation circuit. Then, the CPU 171 outputs this transmission signal to the timing generation circuit 175. The timing generation circuit 175 generates a timing signal according to a counter that stores the number of times a transmission signal has been received, a register that stores a threshold value indicated by the CPU 171, and a result of comparing these values stored in the counter and the register. A circuit having a processor that performs processing. The timing generation circuit 175 outputs the timing signal generated by the processor to the driver circuit 176 and the demodulation circuit 178. The driver circuit 176 is a drive circuit that causes the light emitting element 110a and the light emitting element 110b to alternately emit light at a predetermined timing based on the timing signal received from the timing generation circuit 175. The light emitted from each light emitting element 110 is reflected on the surface of the living body and received by each light receiving element 120 of the light receiving unit 12.

Each light receiving element 120 outputs an electrical signal corresponding to the intensity of the received reflected light to the amplification circuit 177, and the amplification circuit 177 amplifies these electrical signals and outputs them to the demodulation circuit 178. The demodulating circuit 178 receives the electrical signal output from each light receiving element 120 and amplified by the amplifying circuit 177, and applies to each light emitting element 110 irradiated at a predetermined timing based on the timing signal received from the timing generating circuit 175. The data are respectively associated with each other and output to the A / D converter 179. The A / D converter 179 converts each electrical signal output from the demodulation circuit 178 into a digital value and outputs the digital value to the CPU 171. Here, the digital value output from the A / D converter 179 is smaller as the intensity of the reflected light received by each light receiving element 120 is lower. The CPU 171 writes necessary data in the RAM 173 based on the digital value and the program and data stored in the ROM 172 or reads the data to perform an operation, and outputs the result to the display unit 19 and the storage unit 174. . Moreover, the drive part 142 of the moving part 14 is driven based on the calculation result.
The operation unit 18 receives an operation from the user and outputs a signal corresponding to the operation to the CPU 171. The CPU 171 starts or interrupts measurement in accordance with the signal received from the operation unit 18.

(2. Operation)
Next, the operation of the measuring apparatus 1 will be described.
FIG. 5 is a diagram showing the arrangement of the irradiation unit 11 and the light receiving unit 12 viewed from the front plate 101 side in the initial state. The CPU 171 controls the moving unit 14 to move the irradiation unit 11 so as to be in the arrangement shown in FIG. Then, the CPU 171 causes the two light emitting elements 110 of the irradiation unit 11 to emit light alternately and causes the light receiving unit 12 to receive the reflected light. The light receiving element 120 of the light receiving unit 12 receives the reflected light and outputs a signal corresponding to the received light intensity of the received reflected light. When there is an artery near the surface of the irradiated living body, the intensity of the reflected light increases or decreases with pulsation. Therefore, the CPU 171 causes the light receiving element 120 of the light receiving unit 12 to receive the reflected light for a sufficient time with respect to the pulse interval, and the signal output when the received light intensity of the reflected light is the weakest is the light receiving element. Used as 120 signals.
Here, the position of the light source of the irradiation unit 11 is defined as a light source point P ₀ . The reflection points reflected by the light irradiated from the light source point P ₀ through the irradiation openings 16a to 16e and hitting the surface of the arm 3 are reflected points Pa to reflection points Pe (hereinafter, when there is no need to distinguish between them). These are collectively referred to as “reflection point P”). In the initial state, as shown in FIG. 5, the irradiation unit 11 is located at a position closest to the light receiving element 120 a among the positions along the side plate 103. At this time, the distance from the light source point P ₀ to the reflection point Pa is the shortest Lmin among the optical paths. The distance from the light source point P ₀ to the reflection point Pe is the longest Lmax among the optical paths.

FIG. 6 is a diagram illustrating attenuation of light traveling in the air. In this figure, the horizontal axis indicates the distance traveled by light, and the vertical axis indicates the intensity of light at that distance. The intensity I of light having an intensity of I _{0 in} the light source draws an attenuation curve according to the following equation depending on the distance L traveled.
I = I ₀ × (10 ⁻ α ^L )
Here, α is a predetermined constant determined by the wavelength and light transmission medium (in this case, air). The ROM 172 of the control unit 17 stores the attenuation rate of the shaded part from L = Lmin to L = Lmax in this attenuation curve.

FIG. 7 is a diagram showing digital values corresponding to the electrical signals output from the respective light receiving elements 120 in the arrangement of FIG. The five points indicated by “x” in FIG. 7A are digital values output from the A / D converter 179 to the CPU 171 based on the electrical signals output from the respective light receiving elements 120. The CPU 171 reads the above-described attenuation rate stored in the ROM 172 and corrects these digital values. This correction eliminates the difference in the intensity of the electric signal due to the difference in distance from the light source point P ₀ to each reflection point P. The five points indicated by “◯” in FIG. 7B are digital values after correction. The CPU 171 selects the smallest value from the corrected digital values, and specifies the light receiving element 120 corresponding to the smallest value. That is, the CPU 171 determines whether the plurality of light receiving elements 120 are based on the received light intensity indicated by the signals output from the plurality of light receiving elements 120 that receive the reflected light of the light irradiated by the irradiation unit 11 located at a predetermined position. It is an example of the specifying means for specifying one light receiving element 120.

Then, the CPU 171 controls the drive unit 142 of the moving unit 14 so that the irradiation unit 11 approaches the identified light receiving element 120. That is, the CPU 171 and the drive unit 142 are an example of a movement control unit that moves the irradiation unit 11 so that the irradiation unit 11 approaches the identified light receiving element 120. For example, the CPU 171 specifies the light receiving element 120c in the example illustrated in FIG. The identified light receiving element 120c means that the weakest reflected light among the light receiving elements 120 is received when there is no distance difference from the light source point P ₀ , and therefore corresponds to the light receiving element 120c. There is a high possibility that an artery passes through the reflection point Pc. Therefore, the measuring apparatus 1 obtains a more accurate electrical signal from the light receiving element 120c by bringing the irradiation unit 11 closer to the light receiving element 120c.

  FIG. 8 is a diagram illustrating the arrangement of the irradiation unit 11 and the light receiving unit 12 as viewed from the front plate 101 side after the moving operation. Under the control of the CPU 171, the irradiation unit 11 is moved in the direction of the arrow D8 by the moving unit 14, and moved to the position closest to the light receiving element 120c specified by the CPU 171. When this moving operation ends, the CPU 171 causes the light emitting element 110 of the irradiation unit 11 to emit light again. Then, based on the electrical signal output from the identified light receiving element 120c, the blood oxygen saturation is measured. That is, the CPU 171 generates biological information related to the living body based on the signal output from the identified light receiving element 120 that receives the reflected light of the light irradiated by the moved irradiation unit 11. It is an example of a means.

  Even if the irradiation unit 11 and the light receiving unit 12 of the measuring device 1 applied to the surface of the arm 3 by the band 2 are placed at positions shifted from the artery of the arm 3 by the above operation, the measuring device 1 Moves the irradiation unit 11 to the position most suitable for measurement and specifies the light receiving element 120 most suitable for measurement, so that measurement can be performed without any influence.

[Modification]
The above is the description of the embodiment, but the contents of this embodiment can be modified as follows. Further, the following modifications may be combined as appropriate.
(1) In the above-described embodiment, the CPU 171 selects the smallest value from the corrected digital values and specifies the light receiving element 120 corresponding to the smallest value. The light receiving intensity indicated by each signal output from the signal may be compared with a threshold value stored in advance in the storage unit 174 or the ROM 172, and the light receiving element 120 that outputs a signal indicating the light receiving intensity weaker than the threshold value may be specified. Here, when there are a plurality of signals indicating the received light intensity that is weaker than the threshold value, one signal is selected from the plurality of signals, and the light receiving element 120 corresponding to the selected one signal may be specified. In this case, as a method of selecting one signal, for example, the light receiving element 120 closest to the current irradiation unit 11 or the light receiving element 120 farthest from the current irradiation unit 11 may be selected, or selection may be performed using a random number. Also good.

(2) In the embodiment described above, the CPU 171 reads the attenuation rate corresponding to the distance traveled by the light stored in the ROM 172 and corrects the digital value corresponding to the received light intensity, but does not perform the correction. Also good. When the distance from the light source point P ₀ to the reflection point P hardly changes or when it is recognized that there is almost no influence of the distance, there is no influence even if the above correction is omitted. This is because the operation speed increases.

(3) In the above-described embodiment, among the side plates of the measuring apparatus 1, the side plate close to the upper arm is the side plate 103 and the side plate close to the fingers is the side plate 104. The arrangement may be reversed.
In the above-described embodiment, the housing 10 of the measuring apparatus 1 is a rectangular parallelepiped, but the shape of the housing 10 is not limited to this. For example, it may be cylindrical or elliptical. Moreover, the housing | casing 10 is the box shape curved along the circumference | surroundings of an arm, Comprising: You may have the shape which divided | segmented the cylinder in the surface parallel to an axis | shaft. In this case, the surface corresponding to the outer side plate in the cylinder described above is the front plate 101, and the surface corresponding to the front plate 101 and corresponding to the inner side plate in the cylinder described above is the back plate 102. Then, the back plate 102 and the arm 3 may be brought into close contact with each other by curving the fixed back plate 102 in a concave shape along the forearm surface of the arm 3.
In the above-described embodiment, the light receiving elements 120 are arranged along one side plate in the rectangular parallelepiped housing 10, and the irradiation unit 11 moves along the other side plate facing the side plate. However, the arrangement of the light receiving element 120 and the movement mode of the irradiation unit 11 are not limited thereto. For example, when the bottom surface of the cylindrical housing is applied to the arm 3, the light receiving elements 120 may be arranged along the cylindrical side surface, or the irradiation unit 11 moves along the cylindrical side surface. You may make it do.

  Moreover, in the above-mentioned modification, although the measuring apparatus 1 was the shape which divided | segmented the cylinder, the cylindrical shape which is not divided | segmented may be sufficient. For example, the measurement may be performed by passing the cylindrical measuring device 1 through the arm 3. In this case, the irradiation unit 11 may be configured to be able to irradiate by moving the entire circumference of the arm 3. The light receiving element 120 may be disposed along the entire circumference of the arm 3. Although the light receiving elements 120 are arranged on the straight line at equal intervals, the arrangement of the light receiving elements 120 is not limited to such an arrangement, and may be an arbitrary arrangement. For example, when arranged along the surface of the arm 3 and along the circle, the light receiving elements 120 may be arranged so that the angles with respect to the center point of the circle are equal.

(4) In the above-described embodiment, the measuring device 1 is applied to the arm 3, but may be applied anywhere as long as it is the surface of a living body. For example, the measuring device 1 may be applied to an ankle or an ear. In the above-described embodiment, the measuring device 1 measures the blood oxygen saturation level of the living body. However, if the living body information related to the living body is measured, biological information other than the blood oxygen saturation level of the living body is obtained. You may measure. For example, the measuring device 1 may measure the blood glucose level of the living body.

It is a figure which shows the external appearance of the use condition of the measuring apparatus which concerns on embodiment of this invention. It is a figure for demonstrating the internal structure of a measuring apparatus. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. It is a block diagram for demonstrating a control part. It is the figure which showed arrangement | positioning of the irradiation part and light-receiving part seen from the front plate side in the initial state. It is a figure which shows attenuation | damping of the light which progresses in the air. FIG. 6 is a diagram illustrating digital values corresponding to the respective light receiving elements in the arrangement of FIG. 5. It is the figure which showed arrangement | positioning of the irradiation part and light-receiving part which were seen from the front board side after moving operation | movement.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Measuring apparatus, 10 ... Housing | casing, 101 ... Front plate, 102 ... Back plate, 103 ... Side plate, 104 ... Side plate, 11 ... Irradiation part, 110 ... Light emitting element, 12 ... Light receiving part, 120 ... Light receiving element, DESCRIPTION OF SYMBOLS 13 ... Shielding plate, 14 ... Moving part, 140 ... Base, 141 ... Power transmission part, 142 ... Drive part, 16 ... Irradiation port, 17 ... Control part, 171 ... CPU, 172 ... ROM, 173 ... RAM, 174 ... Memory 175: Timing generation circuit, 176: Driver circuit, 177: Amplification circuit, 178: Demodulation circuit, 179 ... A / D converter, 18 ... Operation unit, 19 ... Display unit, 2 ... Band, 3 ... Arm.

Claims (4)

Movable irradiation means for irradiating light on the surface of the living body;
A plurality of light receiving means arranged along the surface of the living body, receiving reflected light of the light irradiated by the irradiation means, and outputting a signal corresponding to the received light intensity;
A specifying means for specifying one light receiving means from the plurality of light receiving means based on the received light intensity indicated by each signal output from the plurality of light receiving means receiving the reflected light of the light emitted by the irradiation means;
A movement control means for moving the irradiation means so that the irradiation means approaches the one light receiving means specified by the specification means;
Biological information generation means for generating biological information related to the living body based on a signal output by the one light receiving means that receives reflected light of the light irradiated by the irradiation means moved by the movement control means; A measuring apparatus comprising: The specifying unit compares the received light intensity indicated by each signal output from the plurality of light receiving units with a threshold value, and uses the light receiving unit that outputs a signal indicating the received light intensity that is weaker than the threshold value as the one light receiving unit. The measuring device according to claim 1, wherein the measuring device is specified. The identification unit identifies a light receiving unit that outputs a signal indicating the weakest light reception intensity among the signals output from the plurality of light receiving units as the one light receiving unit. The measuring device described. The specifying unit corrects each signal output from the plurality of light receiving units according to a distance between each light receiving unit and the irradiation unit at the predetermined position, and based on each corrected signal. The measuring device according to claim 1, wherein the one light receiving unit is specified from the plurality of light receiving units.

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