JP2007236855A - Photoelectric biosensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical ring sensor facilitating to detect pulse waves by suppressing noises. <P>SOLUTION: The optical ring sensor includes a photodiode and a signal processing part with an amplifier, a disturbance remover and an AD converter. In the optical ring sensor, the photodiode and the signal processing part are integrated on a semiconductor substrate. This suppresses noises applied to photoelectric current during its transmission between the photodiode and the signal processing part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a structure of a sensor that measures biological information non-invasively, and further relates to a photoelectric biological sensor that optically detects biological information.

With the growing awareness of health management and efficient use of medical institutions, the development of systems for health management and medical information obtained by obtaining biological information of subjects is being promoted. Photoelectric biosensors have been developed as means for obtaining this type of biometric information.
The structure and operating principle of a photoelectric biosensor according to the prior art will be described using a ring type.

  2A and 2B are a cross-sectional view of a general ring sensor 2 and an external view when the ring sensor 2 is attached to a finger 1. FIG.

  An abutting portion 8 having a light emitting portion 3 and a light receiving portion 7 is disposed on the inner peripheral surface of the ring sensor 2 that is molded to a dimension that allows metal or resin to be attached to a finger, and is emitted from the light emitting portion 3. The light hits the blood vessel of the finger 1 on which it is attached, and is absorbed by hemoglobin in the blood flowing through the blood vessel, and the remaining light is reflected and reaches the light receiving unit 7 to be converted into an electrical signal.

  On the other hand, on the outer peripheral surface of the ring sensor 2, there is provided a storage unit 5 that stores a circuit unit 4 that includes a signal processing unit that processes electrical signals of the light emitting unit 3 and the light receiving unit 7. In addition, an antenna 19 is provided in the storage unit 5 in order to transmit or receive data wirelessly.

  The contact portion 8 and the circuit portion 4 are wired and connected along the shape of the ring sensor 2 by a flexible substrate 6 having wiring between the surface or the thin film layers.

  When the ring sensor 2 is mounted, if a finger is pressed against the contact portion 8 of the sensor including the light emitting portion 3 and the light receiving portion 7 and a predetermined pressure is applied to the blood vessel in advance, the light is received during the vasodilatation period due to the pulse. The amount of light received by the section 7 decreases and increases during systole.

  Thus, when the light passes through the blood vessel, the amount of light is periodically modulated by the pulse, so that the pulse rate can be known by measuring the period of the amplitude change of the signal output from the light receiving unit 7.

  It is also known that among hemoglobin in blood, oxygenated hemoglobin and reduced hemoglobin have different light absorption and transmission characteristics depending on the wavelength of light. For example, the absorption characteristics of reduced hemoglobin is greater than that of oxidized hemoglobin in red light, and oxygenated hemoglobin is greater than that of reduced hemoglobin in infrared light. Therefore, since the ratio of red light and infrared light changes depending on the ratio of oxyhemoglobin and reduced hemoglobin in the blood, the blood oxygen saturation concentration can also be measured by analyzing the ratio of the respective signal intensities. By analyzing the pulse wave waveform in this way, various body states can be captured.

  FIG. 3 is a circuit block diagram of the conventional ring sensor shown in FIG.

  The circuit of the ring sensor 2 according to the prior art includes a light emitting unit 3, a light receiving unit 7, and a circuit unit 4, which are mutually connected by a flexible substrate 6. The antenna 19 and the circuit unit 4 are mounted and connected on the same substrate.

  The light emitting unit 3 irradiates the blood vessel of the attached finger 1 with light for pulse wave detection. The light emitting element driving unit 21 connected to the light emitting unit 3 generates a light emitting element driving current for driving the light emitting unit 3. This light emitting element driving current is modulated in a pulse shape by a certain driving frequency in order to remove disturbance.

  The light receiving unit 7 includes a photodiode 9 and converts incident light into a photocurrent.

  The circuit unit 4 outputs not only the light emitting element driving unit 20 for supplying the pulsed driving current to the light emitting unit 3 but also the signal of the photodiode 9 detected by the light receiving unit 7 as biological information. A processing unit 11, a transmission unit 12 that transmits an output signal of the signal processing unit 11 to a living body management system, a medical institution, and the like, a power supply unit 20 that supplies power to the respective units of the circuit unit 4, and a light emitting element driving unit 21 are provided. The signal processing of the photocurrent is performed.

  The antenna 19 converts the high-frequency current generated by the transmission unit 12 into an electromagnetic wave and radiates it into space. This electromagnetic wave is received by a pulse wave waveform analyzer (not shown here) provided in a biological management system or the like.

  Next, the configuration of the circuit unit 4 will be described in detail.

  The signal output from the photodiode 9 is connected in the order from the upstream side to the downstream side through the flexible substrate 6d in the order of the signal processing unit 11 and the transmission unit 12, and the antenna 19 is connected to the downstream side of the transmission unit 12. ing.

  The signal processing unit 11 includes an amplification unit 13, a disturbance removal unit 14, and an AD conversion unit 15.

  The photocurrent generated in the photodiode 9 is converted into current and voltage by the amplifier 13 and amplified, and then the noise is removed by the disturbance removing unit 14.

  The disturbance removing unit 14 includes a band-pass filter that passes only a band centered on the driving frequency of the driving current of the light emitting element 3. Thereby, the frequency component of the light which the light emission part 3 radiate | emits can be selectively permeate | transmitted, and a noise is removed.

  The signal from which noise has been removed by the filter of the disturbance removal unit 14 is an analog pulse wave signal. This pulse wave signal is subsequently converted into a digital signal by the AD conversion unit 15 and transmitted to the transmission unit 12.

  The transmission unit 12 includes a carrier wave generation unit 16, a modulation unit 17, and a power amplification unit 18. The carrier wave generation unit 16 generates a carrier wave that is a high-frequency current, and the modulation unit 17 modulates the carrier wave using the digital signal. Subsequently, the carrier wave is transmitted to the power amplifier 18 and amplified.

  The biological information detected by the light receiving unit 7 is transmitted to the antenna 19 as the modulated carrier wave and is wirelessly output.

  The power supply unit 20 supplies power to each unit in the circuit unit 4.

  As described above, a ring sensor having a structure including the contact portion 8 that detects a pulse wave, the circuit portion 4 connected via the flexible substrate 6, and the antenna 19 has been proposed.

In this ring sensor 2, a signal line for connecting the photodiode 9 and the circuit unit 4 is formed on the flexible substrate 6, and a shield for suppressing noise intrusion is applied to the signal line (patent) Reference 1).
Japanese Patent Laid-Open No. 2001-070264

  However, according to the prior art, the photocurrent which is an analog signal is directly transmitted to the circuit unit 4 through the signal line on the flexible substrate 6d.

  The photocurrent of this analog signal is mostly a signal due to reflection from surrounding tissues such as muscles, and the pulsation component of arterial blood as biological information is about a few percent of the total photocurrent and is a very weak signal.

  Further, the signal lines from the photodiodes 9 are densely arranged on the flexible substrate 6d and are arranged in parallel with other wirings, so that they are particularly susceptible to noise.

  Although the flexible board 6d is shielded, it is an analog signal, so that the pulse wave waveform is distorted by the influence of noise during signal transmission. For this reason, there is a problem that it is difficult to detect a pulse wave, or an abnormal signal is transmitted. In a conventional apparatus, a process for removing these abnormal signals is performed by a circuit.

  For example, the pulse wave signal is obtained by calculating the pulse wave signal, and the amplitude value of the obtained pulse wave waveform is compared with the past amplitude value. When the amplitude value varies beyond a certain range within a certain time compared to the past amplitude value, the measurement is continued for a certain time. Thereafter, when an amplitude value within the certain range is continuously obtained, it is determined that the pulse wave signal is normal, and the signal is received. Otherwise, it is determined that the pulse wave signal is an abnormal signal that has been distorted by temporary noise, and arithmetic processing is performed to remove this signal.

  However, the arithmetic processing has a problem that the detection of the pulse wave signal is stopped during the period in which the signal is removed.

  The light emitting element driving current is modulated in a pulse shape, and the current value is relatively large with respect to the photocurrent for measurement. When such a wiring through which the light emitting element driving current flows is provided integrally with the signal line, the influence of the noise due to coupling by electromagnetic induction is significant.

  Further, since the antenna 19 is attached to the ring sensor, the signal line is easily affected by noise due to electromagnetic waves radiated from the antenna 19.

  In view of the above problems, an object of the present invention is to provide a photoelectric biosensor capable of facilitating detection of pulse waves and obtaining highly accurate biometric information by suppressing the influence of the noise.

  In order to achieve the above object, the present invention provides a detection unit for measuring biological information, an amplification unit to which an output signal of the detection unit is given, a disturbance removal unit, an AD conversion unit, and a signal processing unit. A biosensor including a transmitter that modulates a carrier wave according to a biometric information output of the biosensor, wherein at least the detection unit and the signal processing unit are integrally formed on a single semiconductor substrate.

  In addition, it is preferable that the photoelectric biosensor is configured by integrally forming the transmission unit, the detection unit, and the signal processing unit on a single semiconductor substrate.

  Furthermore, the detection unit includes a light receiving element, and the biological information is photoelectrically measured.

  It is a photoelectric biosensor in which the biological information measured by the detection unit is a pulse wave or an oxygen saturation concentration.

  Further, the photoelectric biosensor is a ring sensor mounted on a finger-shaped ring surface.

  According to the biological sensor of the present invention, the signal processing unit is configured to be concentrated at a position close to the output derived from the light receiving unit, and the transmission unit is located downstream in a digitally converted signal form in a relatively stable state. The circuit is configured in such a manner that it is transferred to Further, the signal processing unit includes an amplification unit, a disturbance removal unit, and an AD conversion unit. With such a configuration, the signal obtained from the detection unit is amplified, disturbed, and AD converted, and then transmitted to the signal line, so that the influence of noise during signal transmission is suppressed.

  Therefore, even when the signal line is provided on the flexible substrate that is easily affected by noise as described above, the effect of suppressing the influence of noise is high.

  Further, since noise is suppressed, even when an antenna is attached to the ring sensor, signal deterioration due to electromagnetic waves radiated from the antenna is suppressed.

(Embodiment of the Invention)
Embodiments of the present invention will be described below with reference to the drawings, taking a ring sensor as an example. The description of the same configuration as that of the conventional technology is omitted, and a different configuration is described.

  FIG. 1 is a circuit block diagram of a ring sensor according to the present embodiment.

  The circuit according to the present embodiment includes a light receiving unit 107 in which element circuits are concentrated, and preferably configured by integrally integrating circuit elements on a single semiconductor substrate. In addition to the light receiving unit 107, a circuit unit 104, a light emitting unit 103, and an antenna 119 are provided. In particular, since the light emitting unit 103 is a photoelectric biosensor, detection of biological information is not limited by the installation position of the light receiving unit 107. Are respectively connected to each other by a flexible substrate 106.

  The light receiving unit 107 is integrally provided on a single semiconductor substrate in the order of the signal processing unit 111 and the transmission unit 112 in the downstream direction from the output signal of the photodiode 109. Each of the signal processing unit 111 and the transmission unit 112 is configured in the same circuit as the conventional circuit illustrated in FIG. 3 except that the signal processing unit 111 and the transmission unit 112 are configured on a single semiconductor substrate.

  An antenna 119 is connected to the downstream side of the transmission unit 112 via the flexible substrate 106a.

  The circuit unit 104 includes a power supply unit 120 and a light-emitting element driving unit 121. The light-emitting unit 103 needs to be installed at an optimum position for measuring biological information. The circuit unit 104 is integrated with the signal processing unit 107. It can also be formed.

  The power supply unit 120 also supplies power to the light receiving unit 107 via the flexible substrate 106b. In addition, a light emitting element driving current is supplied to the light emitting part 103 installed on the inner peripheral finger pad side of the ring sensor via the flexible substrate 106c on the output side of the light emitting element driving unit 121.

  According to such a configuration, since the photodiode 109 and the amplifying unit 113 are connected by a minute metal wiring provided in the same semiconductor substrate, the influence of noise received by the photocurrent is suppressed. Further, since the photocurrent is amplified, disturbed, and AD converted in the same semiconductor substrate and then transmitted to the transmission unit 112, the influence of noise is suppressed compared to the case where the photocurrent is transmitted as an analog signal.

  Further, it is necessary to integrate at least the photodiode 109 and the signal processing unit 111 that converts the output signal of the photodiode 109 into a digital signal having high stability and outputs the digital signal. Therefore, the transmission unit 112 may be provided on another semiconductor substrate, and both may be connected by a flexible substrate. Also with this configuration, since the digitized pulse wave signal is transmitted to the flexible substrate, an effect of suppressing noise can be obtained.

  A high-frequency current flows through the flexible substrate 106a connecting the transmitter 112 and the antenna 119.

  Further, since a pulsed light emitting element driving current flows through the flexible substrate 106c connecting the light emitting element driving unit 121 and the light emitting unit 103, noise is easily emitted.

  However, according to the present embodiment, the influence of noise received by the photocurrent is suppressed, so that the disturbance of the pulse wave signal waveform is suppressed.

  In particular, in the case of a ring sensor, the antenna 119 is integrally attached to a small housing, and thus the above configuration is preferable.

  In addition, since the influence of noise is suppressed by the above configuration, the flexible substrates 106a, 106b, and 106c can be provided close to each other, and the ring sensor can be easily downsized.

  An arbitrary sensor can be provided on the upstream side of the signal processing unit 111.

  For example, an acceleration sensor may be provided to detect the wearer's movement, or a pressure sensor may be provided to detect the wearer's blood pressure.

  The sensors may be formed on the same semiconductor substrate as the signal processing unit 111 by a fine processing technique.

It is a circuit block diagram of the ring sensor concerning this Embodiment. It is sectional drawing of the ring sensor by a prior art, and an external view when mounting | wearing with a finger. It is a circuit block diagram of the ring sensor by a prior art.

Explanation of symbols

3, 103 Light emitting unit 4, 104 Circuit unit 6, 106 Flexible substrate 7, 107 Light receiving unit 9, 109 Photodiode 11, 111 Signal processing unit 12, 112 Transmitting unit 13, 113 Amplifying unit 14, 114 Disturbance removing unit 15, 115 AD conversion unit 16, 116 Carrier generation unit 17, 117 Modulation unit 18, 118 Power amplification unit 19, 119 Antenna 20, 120 Power supply unit 21, 121 Light emitting element driving unit

Claims (5)

  A detection unit that measures biological information, an amplification unit to which an output signal of the detection unit is given, a disturbance removal unit, an AD conversion unit, and a transmission that modulates a carrier wave by the biological information output of the signal processing unit A biosensor comprising: a biosensor, wherein at least the detection unit and the signal processing unit are integrally formed on a single semiconductor substrate.   The biosensor according to claim 1, wherein the transmission unit, the detection unit, and the signal processing unit are integrally formed on a single semiconductor substrate.   The photoelectric biosensor according to claim 1, wherein the detection unit includes a light receiving element and photoelectrically measures biological information.   The biological sensor according to claim 1, wherein the biological information is a pulse wave or an oxygen saturation concentration. A ring sensor in which the biological sensor according to claim 1 is mounted on a finger-shaped ring surface.

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