JP2010276407A - Photodetection device and biological information measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light detection device and a biological information measurement device for detecting weak light by eliminating the influence of electromagnetic waves in a measurement environment.
A light receiver 22 (photodetector) includes a shield case 22a and an incident window 22c that are electrically grounded, and a light receiving element 22b and an amplifier 23 are accommodated in the case 22a. Thereby, propagation of the noise electric field (noise) existing outside to the light receiving element 22b and the amplifier 23 can be prevented. The amplifier 23 has a smaller output impedance than the output impedance of the light receiving element 22b, amplifies the electrical signal output from the light receiving element 22b, and outputs the amplified signal with a low impedance. Thereby, the influence of the noise electric field (noise) on the output signal can be made extremely small, and the deterioration of the S / N ratio of the output signal can be prevented.
[Selection] Figure 5

Description

  The present invention relates to a light detection device, particularly a light detection device that detects weak light by eliminating the influence of electromagnetic waves in a measurement environment, and a blood flow change in a living body, blood oxygen concentration, oxygen using this light detection device The present invention relates to a biological information measuring device that measures biological information by paying attention to the property that light propagating in a living body changes differently depending on the wavelength according to saturation, pulse, and other various biological metabolisms.

  2. Description of the Related Art In recent years, it has been widely performed to process various types of information of light using a photodetection device whose main component is a photoelectric conversion element that converts received light into an electrical signal. And as an example which applied such a photon detection apparatus, the biological information measurement apparatus which can measure the inside of a biological body simply and non-invasively can be mentioned, for example. In this biological information measuring apparatus, for example, as shown in Patent Document 1 below, light is emitted from a light source arranged on the surface of the living body to the inside of the living body, propagates while being scattered and absorbed inside the living body, and then returns to the living body surface Information (biological information) inside the living body is measured (measured) on the basis of an electrical signal that is received by a photodetection device, more specifically, a photoelectric conversion element.

  By the way, when the photoelectric conversion element receives an extremely weak light and outputs an electrical signal, a noise electric field (noise) due to an electromagnetic wave existing in the measurement environment is generated by the photoelectric conversion element. May adversely affect output. Further, in the above-described conventional biological information measuring apparatus, for example, myoelectric potential generated in association with the activity of a living body's muscle is used as a noise electric field (noise) to receive light or output an electrical signal by a photoelectric conversion element. It may have an adverse effect on it. With regard to suppressing the influence of such a noise electric field (noise), for example, it is effective to electromagnetically shield the photoelectric conversion element using an electromagnetic shield structure as shown in Patent Document 2 below. It is.

Japanese Patent No. 3623743 JP 2006-229922 A

  By the way, even if an electromagnetic shield structure as shown in Patent Document 2 is adopted, it is impossible to completely eliminate the influence of a noise electric field (noise) on the photoelectric conversion element. In general, a photoelectric conversion element using a semiconductor has high output impedance due to zero bias or reverse bias. Therefore, for example, when the photoelectric conversion element receives an extremely weak light and outputs an electrical signal in an electromagnetically shielded state, an electrical signal that is originally output corresponding to the received light is output. In addition to the signal, a noise electric field (noise) that slightly influences may be output as a noise signal due to high impedance. Thereby, for example, when it is necessary to measure information with extremely weak light, such as the above-described biological information, with extremely high precision, a decrease in measurement accuracy may be significant. Therefore, in the case of processing various information possessed by (extremely) weak light, in addition to electromagnetically shielding the photoelectric conversion element from electromagnetic waves, etc., noise signals based on the electromagnetic waves, etc. are reduced and high-quality electrical It is very important to output a typical signal.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a photodetector that detects weak light by eliminating the influence of electromagnetic waves in a measurement environment, and a living body using the photodetector. An object of the present invention is to provide a biological information measuring device that measures information.

  In order to achieve the above object, a feature of the present invention is a light detection device for detecting light, which has a conductive case grounded with conductivity and optical transparency with respect to the wavelength of light to be detected. A window portion that has electrical conductivity and is electrically connected to the conductive case to receive light, and receives light incident from the window portion received in the conductive case and electrically A photoelectric conversion element for converting into a detection signal, and an output impedance smaller than an output impedance of the photoelectric conversion element while amplifying an electrical detection signal contained in the conductive case and output from the photoelectric conversion element And an amplifier circuit for outputting the amplified electrical detection signal.

  Another feature of the present invention is a biological information measuring device that detects light propagating through a living body and measures biological information possessed by the detected light. A light emitting unit that emits near-infrared light having a different specific wavelength by emitting light from the light source based on a signal, a conductive case that is conductive and grounded, and is emitted from the light emitting unit A window portion that has optical transparency with respect to a specific wavelength and has electrical conductivity, is electrically connected to the conductive case and receives light, and is received in the conductive case and the window portion. A photoelectric conversion element that receives light incident from the photoelectric conversion element and converts the light into an electrical detection signal; amplifies the electrical detection signal that is contained in the conductive case and is output from the photoelectric conversion element; and Conversion element An amplification circuit that outputs the amplified electrical detection signal with an output impedance smaller than a force impedance, and receives and detects near-infrared light emitted from the light emitting unit and propagating through the living body. A light detection unit that outputs an electrical detection signal related to the metabolism of the living body corresponding to the light intensity of the detected near-infrared light, and the overall operation of the light emission unit and the light detection unit are controlled. And a controller that calculates biological information based on an electrical detection signal output from the light detector.

  In these cases, for example, the window portion is laminated on at least one surface side of the transparent substrate having optical transparency with respect to the wavelength of the light to be detected or the specific wavelength, and the wavelength to be measured or the It is good to comprise with the transparent conductive film which has the optical transparency with respect to a specific wavelength, and has electroconductivity.

  In this case, for example, at least one surface of the transparent base material is combined with at least one dielectric film having at least one band transmittance that selectively transmits the wavelength of the light to be detected or the specific wavelength. It is good to laminate on the side. And the transparent conductive film which comprises the said window part is good to be formed, for example with yttrium-tin oxide (ITO), zinc oxide (ZnO), or niobium oxide (NbO) as a main component.

  The amplifier circuit may include an operational amplifier having a large input impedance, for example.

  Furthermore, the photoelectric conversion element may be, for example, a photodiode or an avalanche photodiode.

  Further, in the biological information measuring device, the light source is, for example, a conductive case that is electrically conductive and grounded, and has optical transparency with respect to the specific wavelength and electrical conductivity, and is electrically conductive. A window portion that is electrically connected to the case and transmits light, and a light emitting element that is housed in the conductive case and emits near-infrared light having the specific wavelength from the window portion may be included. In this case, a plurality of the light emitting elements may be accommodated in the conductive case. Further, in this case, the window portion is laminated on at least one surface side of the transparent substrate having optical transparency with respect to the specific wavelength, for example, and has optical transparency with respect to the specific wavelength. At the same time, it may be constituted by a transparent conductive film having electrical conductivity. In this case, the transparent conductive film constituting the window portion is preferably formed, for example, with yttrium-tin oxide (ITO), zinc oxide (ZnO), or niobium oxide (NbO) as a main component. Furthermore, the light emitting element may be, for example, a semiconductor laser or a light emitting diode.

  In the biological information measuring device, the biological information calculated by the control unit includes, for example, a change in oxygenated hemoglobin concentration length combined with oxygen and a change in reduced hemoglobin concentration length not combined with oxygen in the blood vessels of the living body. It is good that it is information showing.

  Further, in the biological information measuring apparatus, the light emitting unit emits near infrared light having the specific wavelength to the head of the living body, and the light detecting unit transmits near infrared light that has propagated through the head of the living body. The light may be received and the electrical detection signal may be output, and the control unit may calculate biological information relating to activity in the brain of the living body.

  In the biological information measuring apparatus, the light emitting unit includes a spread spectrum modulation unit that performs spread spectrum modulation on the predetermined drive signal, and the light detection unit despreads the electrical detection signal. And demodulating means for demodulating. In this case, the spread spectrum modulation unit of the light emitting unit includes a spread code sequence generation unit that generates a spread code sequence for performing spread spectrum modulation on the predetermined drive signal using a first frequency, and the spread code sequence generation unit The first modulation means for spectrum-spreading the predetermined drive signal using the spreading code sequence generated by the step S1 and outputting a primary modulation signal, and the second frequency that is twice the first frequency Second modulation means for modulating the primary modulation signal output by the first modulation means and outputting a secondary modulation signal, and the demodulation means of the photodetection unit has a signal band of the electrical detection signal. Among them, signal component removing means for removing and outputting a signal component at a frequency near DC and a frequency near the second frequency and a signal component higher than the second frequency, and the near-infrared light propagates in the living body. A signal conversion means for converting the electrical detection signal output by the signal component removal means into a digital signal using a third frequency that is twice the second frequency taking into account the delay associated with First demodulating means for demodulating the digital signal converted by the signal converting means using the second frequency taking into account the delay associated with propagation of near-infrared light in the living body and outputting a primary demodulated signal And a second demodulating means for despreading the primary demodulated signal using the spread code sequence in consideration of a delay associated with the propagation of the near-infrared light in the living body and outputting a secondary demodulated signal. It is good to have. Furthermore, in this case, the second frequency may be made to coincide with, for example, an effective detection bandwidth capable of effectively detecting near-infrared light transmitted through the living body by the light detection unit.

  In the biological information measuring device, the light emitting unit acquires the predetermined drive signal supplied with a predetermined time interval, and the light sources sequentially sequentially based on the acquired predetermined drive signal. It is preferable that near infrared light having different specific wavelengths is emitted sequentially with the predetermined time interval.

  Further, in the biological information measuring apparatus, the light emitting unit includes frequency division multiplexing modulation means for generating a modulation signal by frequency division multiplexing modulation of the predetermined drive signal, and the light detection unit includes the electrical detection unit. It is preferable to have a demodulating means for frequency-division multiplex demodulating the detected signal.

  According to these, in the photodetection device (the photodetection unit of the biological information measurement device), the photoelectric conversion element and the amplification circuit are electromagnetically shielded by the conductive case and the window. Thereby, it can prevent effectively that the noise electric field (noise) by the electromagnetic waves etc. which exist in a measurement environment influences a photoelectric conversion element and an amplifier circuit. Further, even when the noise electric field (noise) shielded in this way slightly affects the photoelectric conversion element and the amplification circuit, the output impedance of the amplification circuit is higher than the output impedance of the photoelectric conversion element. Since it is small, the S / N ratio of the electrical detection signal output through the amplifier circuit can be increased. Therefore, for example, even in a situation where extremely weak light is detected, a high-quality electrical detection signal corresponding to the detected light can be output.

  In the biological information measuring apparatus, the light emitting unit may be, for example, a spread spectrum modulated drive signal, a predetermined drive signal supplied with a predetermined short time interval, or a frequency division multiplex modulated drive. Based on the signal, it is possible to emit near-infrared light having a plurality of specific wavelengths toward the inside of the living body by causing the light source to emit light. On the other hand, the photodetection unit receives near-infrared light propagating through the living body in an electromagnetically shielded state, and the received near-infrared light, that is, extremely weak near-red light attenuated along with propagation inside the living body. An electrical detection signal related to the metabolism of the living body can be output with low impedance corresponding to the light intensity (light quantity) of external light. Here, the light emitting unit emits a light source based on a drive signal (modulation signal) obtained by subjecting a predetermined drive signal to spread spectrum modulation or frequency division multiplex variation, and directs near infrared light having a plurality of specific wavelengths into the living body. In this case, the light detection unit can perform spectrum despread demodulation or frequency division multiplexing modulation on the electrical detection signal. Based on the electrical detection signal, biometric information, for example, as the sum of oxygenated hemoglobin concentration length change and reduced hemoglobin concentration length change, oxygenated hemoglobin concentration length change and reduced hemoglobin concentration length change in the blood vessels of the living body A change in total hemoglobin concentration length that can be calculated, a pulse wave that changes with blood flow, or oxygen saturation can be calculated.

  Therefore, in the biological information measuring device, even if the near-infrared light attenuated by propagating through the inside of the living body, the light detection unit can generate a noise electric field (noise) due to, for example, myoelectric potential generated in the living body. Therefore, it is possible to output a high-quality electrical detection signal. Thereby, biological information can be measured (calculated) extremely accurately. In the biological information measuring device, the light source can also be electromagnetically shielded. Therefore, emission (radiation) of a noise electric field (noise) generated with the operation of the light source can be prevented, and the influence on light detection by the light detection unit can be greatly reduced. This also makes it possible to measure (calculate) biological information very accurately.

It is a block diagram which shows the outline of the common biological information measuring device which concerns on embodiment and each modification of this invention. It is a block diagram which shows schematically the structure of the light-projection part of FIG. It is a schematic sectional drawing which shows the structure of the light source of FIG. FIG. 2 is a block diagram schematically showing a configuration of a light detection unit in FIG. 1. FIG. 5 is a schematic cross-sectional view showing a configuration of a light receiver and an amplifier in FIG. 4. FIG. 6 is a schematic electrical circuit diagram of the amplifier of FIG. 5. FIG. 2 is a block diagram schematically showing a configuration of a controller in FIG. 1. It is the figure which extracted and showed a part of arrangement | sequence of the incident position and light reception position at the time of applying a biological information measuring device to the measurement of the biological information in a brain. It is a schematic diagram for explaining Lambert-Beer's law. It is the graph which showed roughly the change of the molecular extinction coefficient with respect to the wavelength of oxygenated hemoglobin and reduced hemoglobin. It is a schematic sectional drawing which shows the structure of the light source which concerns on the 1st modification of this invention. It is a schematic sectional drawing which shows the structure of the light receiver which concerns on the 2nd modification of this invention. It is a schematic sectional drawing which shows the structure of the light receiver which concerns on the 2nd modification of this invention. It is a schematic sectional drawing which shows the structure of the light receiver which concerns on the 3rd modification of this invention. FIG. 10 is a schematic cross-sectional view illustrating a configuration of an electromagnetic shield case that houses a light receiver and an amplifier according to a fourth modification of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram schematically showing the configuration of a biological information measuring device S according to an embodiment of the present invention. As shown in FIG. 1, the biological information measuring apparatus S includes a plurality of light emitting units 1 that generate light having a specific wavelength, and light emitted from the light emitting unit 1 is propagated while reflecting inside the living body. And a plurality of light detectors 2 for detecting the light of the light. In addition, the biological information measuring device S includes a microcomputer including a CPU, a ROM, a RAM, a timer, and the like as main components, and comprehensively controls the operations of the light emitting unit 1 and the light detecting unit 2 and related to the metabolism of the living body. A controller 3 that calculates and outputs biometric information to be output, and a display unit 4 that displays the calculated biometric information in a predetermined manner.

  As shown in FIG. 2, the light emitting unit 1 includes a plurality of light generators 10 that generate light having different specific wavelengths. In the following description, the light emitting unit 1 is exemplarily composed of two light generating devices 10, in other words, one light emitting unit 1 is configured to generate light having two specific wavelengths. And implement. However, the number of the light generating devices 10 constituting the light emitting unit 1, that is, the number of specific wavelengths of the emitted light is not limited to this, and the light emitting unit 1 can generate, for example, three or more lights. Needless to say, the apparatus 10 can be implemented. As described above, by providing a large number of the light generation devices 10, it is possible to sufficiently ensure the quantitativeness of the biological information obtained as described later.

  Each of these light generators 10 emits light having a specific wavelength by performing spread spectrum modulation. For this reason, each light generator 10 includes a spread code sequence generator 11 for generating a PN (Pseudorandom Noise) sequence consisting of “+1” and “−1” having a length of 65536 bits, for example, as a spread code sequence. ing. The spreading code sequence generator 11 generates, for example, a Hadamard sequence, an M sequence, or a Gold code sequence as a PN sequence.

  The Hadamard sequence, the M sequence, or the Gold code sequence described above is the same as that used for general spread spectrum modulation, and a detailed description of the generation method is omitted. Keep it. The Hadamard sequence is a sequence obtained by extracting each row or each column of the Hadamard matrix composed of “+1” and “−1”. The M series uses a shift register in which n stages of 1-bit registers for storing a state of “0” or “+1” are arranged, and an exclusive OR of a value fed back from the middle of the shift register and a value in the last stage Is a binary sequence obtained by connecting to the first stage. However, in order to make this binary sequence a PN sequence, level conversion is performed to convert the value “0” into “−1”. The Gold code sequence is basically a code sequence obtained by preparing two types of M sequences and adding them. For this reason, the Gold code sequence is a matrix that can increase the number of sequences in each stage as compared with the M sequence. As a feature of these sequences, different sequences have a property of being orthogonal to each other, and by performing a product-sum operation, the correlation becomes “0” except for self.

  The spread code sequence generator 11 receives a clock frequency 2 f supplied from a clock generator 32 (described later) provided in the controller 3. Then, based on the input clock frequency 2f, the spread code sequence generator 11 generates a PN sequence in which the generation frequency of the PN sequence, in other words, the chip rate corresponding to the minimum generation interval of the PN sequence is f or less.

  In this way, the PN sequence generated by the spread code sequence generator 11 is output to the controller 3 and also to the first multiplier 12. The first multiplier 12 takes the product of the DC signal output from the baseband output unit 13 and the PN sequence supplied from the spread code sequence generator 11 and performs spread spectrum modulation on the DC signal. In the following description, the spread spectrum modulated DC signal is referred to as a primary modulation signal.

  This primary modulation signal is output to the second multiplier 14. The second multiplier 14 receives the primary modulation signal and also receives the clock frequency 2 f supplied from the clock generator 32 of the controller 3. Then, the second multiplier 14 modulates the input primary modulation signal with the clock frequency 2f. Thus, by modulating the primary modulation signal with the clock frequency 2f, the modulated primary modulation signal has the strongest signal strength at the frequency f. In the following description, the modulated primary modulation signal is referred to as a secondary modulation signal.

  As described above, the secondary modulation signal modulated by the second multiplier 14 is output to the light source driver 15. The light source driver 15 supplies a predetermined driving voltage to the light source 16 based on the secondary modulation signal, and drives (emits light) the light source 16. As shown in FIG. 3, the light source 16 includes a light emitting element 16b accommodated in the shield case 16a and an emission window 16c that emits light from the light emitting element 16b.

  The shield case 16a is made of a material for performing electromagnetic shielding, that is, a metal material or a resin material having conductivity, and is grounded via a shield electrode 16a1 as shown in FIG. The light emitting element 16b is, for example, a semiconductor laser or a light emitting diode, and the anode electrode 16b1 and the cathode electrode 16b2 are connected to each other. The light emitting element 16b emits near infrared light (hereinafter referred to as modulated light) having a specific wavelength in the wavelength range of 600 to 1500 nm. In the following description, of the two light sources 16 constituting the light generation device 10, one light source 16 emits modulated light having a specific wavelength of 840 nm, for example, and the other light source 16 has, for example, In the following description, it is assumed that modulated light having a specific wavelength of 770 nm is emitted.

  The exit window 16c includes a transparent base material 16c1 (for example, quartz or optically transparent transparent plastic) that optically transmits modulated light having a specific wavelength by the light emitting element 16b, and a transparent base material 16c1. The transparent conductive film 16c2 is formed on at least one side. Here, as a material for forming the transparent conductive film 16c2, yttrium-tin oxide (ITO), zinc oxide (ZnO (Zinc Oxide)), or niobium oxide (NbO (Niobium Oxide)) is used. It is good to select and employ from these. The transparent conductive film 16c2 is formed on the transparent base material 16c1 by using, for example, a well-known vapor deposition method, and the formed film thickness is, for example, about 100 nm. In this way, instead of forming the emission window 16c from the transparent base material 16c1 and the transparent conductive film 16c2, it is also possible to form the emission window 16c by thinning a bulk material of ITO, ZnO, NbO, for example. It is. Further, the transparent conductive film 16c2 is electrically connected to the shield case 16a using a metal sealing material such as a conductive adhesive (for example, silver paste) or solder.

  Then, modulated light having two different specific wavelengths emitted from each light emitting unit 1 is incident toward the inside of the living body via the optical combiner 17 (for example, an optical fiber). In this case, the light combiner 17 may be omitted, and the modulated light may be directly incident from the light emitting units 1 toward the inside of the living body.

  As shown in FIG. 4, the light detection unit 2 detects extremely weak modulated light that propagates while reflecting inside the living body, and an electrical biological information signal related to biological information that the detected modulated light has. Is output. For this reason, the light detection unit 2 includes a light receiver 22 that receives the modulated light emitted from the light emitting unit 1 and propagated through the living body via a light combiner 21 (for example, an optical fiber). In this case, the light combiner 21 may be omitted and the light receiver 22 may directly receive the modulated light that has propagated through the living body.

  As shown in FIG. 5, the light receiver 22 includes a light receiving element 22b as a photoelectric conversion element housed in a shield case 22a, and an incident window 22c that transmits the modulated light propagated through the living body to the light receiving element 22b. And. The shield case 22a is made of a material for performing electromagnetic shielding, that is, a metal material or a resin material having conductivity, and is grounded via a ground terminal 22a1 as shown in FIG. The light receiving element 22b is, for example, a PIN photodiode or an Alabache photodiode whose main component is a semiconductor such as Si or InGaAs, and its effective detection bandwidth is set to 2f. The light receiving element 22b is electrically connected to an amplifier 23 that is integrally accommodated in the shield case 22a, as will be described later.

  The incident window 22c includes a transparent base material 22c1 (for example, quartz (Coltz) or optically transparent transparent plastic) that optically transmits modulated light having a specific wavelength with respect to the light receiving element 22b, and a transparent base material. And a transparent conductive film 22c2 formed on at least one side of 22c1. The transparent conductive film 22c2 is electrically connected to the shield case 22a using a metal sealing material such as a conductive adhesive (for example, silver paste) or solder. Here, the material for forming the transparent conductive film 22c2 may be selected from ITO, ZnO, and NbO as in the transparent conductive film 16c2 in the light source 16 of the light emitting section 1. Further, regarding the formation of the transparent conductive film 22c2, similarly to the transparent conductive film 16c2, for example, a well-known vapor deposition method or the like is used to form a film thickness of about 100 nm with respect to the transparent substrate 22c1. Note that the film thickness of the transparent conductive film 22c2 is not limited to this, and a larger film thickness (for example, about 500 nm) can be formed. Further, the transparent conductive film 22c2 can also form the entrance window 22c by thinning the bulk material of ITO, ZnO, and NbO.

  In the present embodiment, a Pin photodiode or an Alabane photodiode is used as the light receiving element 22b. For example, two-dimensional optical information is acquired using a photoelectric conversion element such as a CCD or a CMOS. Is also possible. In this case, a transparent insulating layer corresponding to the transparent base material 22c1 is formed on the surface of a CCD or CMOS, and a transparent conductive film 22c2 is formed through the insulating layer, and the transparent conductive film 22c2 is grounded. It is preferable to be electrically connected to the shield case 22a.

  The amplifier 23 is housed in the shield case 22a of the light receiver 22, and an amplifier circuit (amplifying the intensity of an electrical detection signal (analog signal) output from the light receiver 22 (more specifically, the light receiving element 22b)). Low noise amplifier). Therefore, as shown in FIG. 6, the amplifier 23 includes an operational amplifier 23a and a signal output terminal 23b that outputs an amplified electrical detection signal (analog signal). Although detailed illustration is omitted around the signal output terminal 23b, an electrical short circuit is prevented by insulating glass, non-conductive plastic, or the like. The signal output terminal 23b is connected to, for example, a coaxial cable, and the outer peripheral metal layer of the coaxial cable is electrically connected to the shield case 22a of the light receiver 22.

  The operational amplifier 23a has characteristics of extremely high input impedance (for example, about 40 MΩ) and low output impedance (for example, about 150Ω), and is connected to a positive power supply terminal 23a1 and a negative power supply terminal 23a2. By the way, since the light receiving element 22b of the light receiver 22 is zero or reverse biased when detecting the modulated light, its output impedance becomes a value close to mega ohms. In such a high output impedance state, a weak electromagnetic wave, that is, a current induced by a noise electric field (noise) generates a large noise voltage. Therefore, an electrical detection signal (analog signal) does not pass through the amplifier 23. ), The S / N ratio of the output electrical detection signal (analog signal) is deteriorated. Therefore, since the influence of the noise electric field (noise) is reduced if the output impedance is low, by outputting an electrical detection signal (analog signal) via the operational amplifier 23a having a low output impedance, that is, a low impedance, It is possible to output a good quality detection signal while preventing the S / N ratio from deteriorating.

  Further, by housing the amplifier 23 in the grounded shield case 22a, it is possible to effectively prevent the influence of the external noise electric field on the electrical detection signal (analog signal) output from the amplifier 23. This also prevents the deterioration of the S / N ratio in the electrical detection signal (analog signal) output via the amplifier 23 (more specifically, the operational amplifier 23a) and outputs a high-quality detection signal. . Thus, the electrical detection signal (analog signal) amplified by the amplifier 23 is output to the low-pass filter (LPF) 24 via the signal output terminal 23b.

  The LPF 24 is, for example, a Nyquist filter that realizes an impulse response waveform that satisfies the first Nyquist criterion and prevents intersymbol interference, and has a cutoff frequency set to 2f. Accordingly, the LPF 24 removes (cuts) a signal component having a frequency higher than 2f from the detection signal (analog signal) input from the amplifier 23 and outputs the signal component to the AD converter 25.

  The AD converter 25 converts an electrical detection signal (analog signal) that has passed through the LPF 24 into a digital signal. Specifically, the AD converter 25 inputs a clock frequency 4f appropriately delayed by a delay 33 described later from the clock generator 32 of the controller 3, and converts an electrical detection signal (analog signal) into a digital signal at the sampling frequency 4f. Convert. Here, when the AD converter 25 performs digital conversion processing at a sampling frequency 4f that is twice the effective detection bandwidth 2f of the optical receiver 22, it is also called a generally known sampling theorem (sampling theorem or Nyquist theorem). ) Holds.

  That is, according to the sampling theorem, in order to accurately reproduce the target signal, it is necessary to sample using a sampling frequency that is at least twice the frequency of the target signal. Here, the “signal for purpose” in the sampling theorem is an “electrical detection signal (analog signal)” output from the amplifier 23 corresponding to the intensity of the modulated light propagated in the living body received by the light receiver 22. Since the “frequency of the target signal” is 2f that matches the effective detection bandwidth of the light receiver 22 (or the cut-off frequency of the LPF 24), digital conversion by the AD converter 25 is performed by setting the sampling frequency to 4f. Sampling theorems hold in processing. In other words, the information (that is, the analog detection signal) included in the modulated light that matches the effective detection bandwidth 2f of the light receiver 22 (or the cut-off frequency of the LPF 24) can be accurately converted into a digital signal without causing information loss or the like. Converted.

  Thus, when the AD converter 25 converts the electrical detection signal (analog signal) into a digital signal at the sampling frequency 4f, the AD converter 25 outputs the converted digital signal to the first multiplier 26. The first multiplier 26 receives the converted digital signal and also receives the clock frequency 2 f supplied with a delay from the clock generator 32 of the controller 3 via the delay 33. The first multiplier 26 demodulates the digital signal using the clock frequency 2 f input from the clock generator 32. In the following description, the signal demodulated by the first multiplier 26 is referred to as a primary demodulated signal. When the digital signal is demodulated in this way, the first multiplier 26 outputs the primary demodulated signal to the second multiplier 27.

  The second multiplier 27 includes the primary demodulated signal input from the first multiplier 26 and the PN sequence supplied with a delay from the spread code sequence generator 11 of the light emitting unit 1 via the delay 33 of the controller 3. Take the product. Thus, by acquiring the PN sequence, the second multiplier 27 is a specific light emitting unit 1 among the plurality of light emitting units 1 and a specific light emitting unit, as will be described in detail later. The primary demodulated signal corresponding to the modulated light emitted from any one of the light generators 10 constituting the unit 1 can be demodulated by spectrum despreading. Then, the second multiplier 27 outputs an electrical detection signal (digital signal) demodulated by spectrum despreading, that is, a secondary demodulated signal, to the accumulator 28.

  The accumulator 28 adds the PN sequence generated by the spread code sequence generator 11 of the light emitting unit 1 to the supplied secondary demodulated signal over one period. Then, the accumulator 28 is a very weak light emitted from the specific light emitting unit 1 (more specifically, any one of the light generating devices 10 constituting the specific light emitting unit 1) and attenuated in the living body. The modulated light, in other words, a biological information signal corresponding to the intensity of the modulated light including biological information is output to the controller 3. Here, as shown in FIG. 4, a plurality of second multipliers 27 and accumulators 28 are provided in accordance with the number of specific wavelengths emitted from the light emitting unit 1 (one light emitting unit 1 in this embodiment). In the case where there are two or more light emitting sections 1 that can receive light, the number obtained by multiplying the number of each existing light emitting section 1) is provided. Thereby, a biological information signal corresponding to the intensity of each modulated light propagated in the living body can be obtained simultaneously.

  As shown in FIG. 7, the controller 3 includes a control unit 31 having a microcomputer including a CPU, a ROM, a RAM, a timer, and the like as main components. Further, the controller 3 is provided with the clock generator 32 and the delay 33 in order to control the operation of the light emitting unit 1 and the light detecting unit 2 as described above. As described above, the clock generator 32 matches the effective detection bandwidth of the light receiving unit 22 constituting the light detection unit 2 and is a clock as the second frequency that is twice the frequency f as the first frequency. A frequency 2f and a clock frequency 4f that is twice the clock frequency 2f are supplied to the light emitting unit 1 and the light detecting unit 2. The delay 33 is a PN sequence code generated by each spread code sequence generator 11 of each light emitting unit 1 to be described later and supplied to the light detecting unit 2 and a clock frequency 4f or clock supplied to the light detecting unit 2 by the clock generator 32. The frequency 2f is appropriately delayed. Here, in this case, since the delay characteristic may be different for each path of light propagating from the light emitting unit 1 toward the light detecting unit 2, the delay 33 is provided for each light detecting unit 2. Thus, the biological information can be obtained more accurately.

  Furthermore, the controller 3 outputs data representing the calculated biological information to the display unit 4. The display unit 4 is composed of, for example, a liquid crystal display and displays biometric information in a predetermined manner based on data supplied from the controller 3.

  Next, the operation of the biological information measuring device S configured as described above will be described. In the following description, the case of observing a blood flow change in the subject's brain will be described as an example.

  Blood flowing through living arteries and veins (hereinafter referred to as arterial blood and venous blood, respectively) is hemoglobin combined with oxygen (hereinafter referred to as oxygenated hemoglobin) and hemoglobin not combined with oxygen (hereinafter referred to as hemoglobin). Is called reduced hemoglobin). The amount of oxygenated hemoglobin and the amount of reduced hemoglobin in arterial blood and venous blood vary depending on the activity of the living body. Here, since oxygenated hemoglobin and reduced hemoglobin have different absorbances of near-infrared light, by calculating the difference in the absorbance of near-infrared light between oxygenated hemoglobin and reduced hemoglobin, a change accompanying the activity of the living body, that is, Blood flow changes can be observed. Therefore, the controller 3 of the biological information measuring device S uses, as will be described later, oxygen in arterial blood and venous blood in the brain using a biological information signal corresponding to the intensity of the modulated light propagated in the subject's brain. The hemoglobin concentration length change ΔCoxy and the reduced hemoglobin concentration length change ΔCdeoxy are calculated as biological information.

  For this reason, when operating the biological information measuring device S in the present embodiment, as shown in FIG. The light detection unit 2 is attached. Specifically, on the surface of the head T of the subject, modulated light emitted from the light emitting unit 1 is incident on positions a to f (hereinafter referred to as incident positions a to f) indicated by circles. . In addition, a very weak modulated light (hereinafter referred to as this modulated light) that propagates while reflecting in the brain (for example, around the frontal lobe) and reaches positions A to F (hereinafter referred to as light receiving positions A to F) indicated by square marks. Light is also referred to as reflected light) and is detected by the respective light detection units 2. The incident positions a to f and the light receiving positions A to F are arranged in a matrix, for example. In the following description, each light emitting section 1 that emits modulated light to incident positions a to f is referred to as light emitting sections a to f, and each light that detects reflected light that reaches light receiving positions A to F is detected. The detection part 2 is shown as light detection part AF.

  In the following description, each light emitting section 1 that emits modulated light to incident positions a to f is referred to as light emitting sections a to f, and each light that detects reflected light that reaches light receiving positions A to F is detected. The detection part 2 is shown as light detection part AF. FIG. 6 shows only a part of the biological information measuring device S. For this reason, the one-to-one combination of the incident position and the light receiving position, that is, the number of channels is not limited to the illustrated number. Therefore, it is also possible to measure biological information using biological information signals of reflected light propagated in the brain by arranging more combinations of incident positions and light receiving positions (for example, about 1000 channels) in a matrix. it can. Further, the channel arrangement is not limited to a matrix, and for example, a staggered arrangement, a light detection unit 2 is arranged around a certain light emitting unit 1, or a certain light detection unit 2 is arranged. Various arrangements such as a donut-like arrangement in which a plurality of light emitting portions 1 are arranged around the center can be employed.

  As described above, when the light emitting unit 1 and the light detecting unit 2 are attached to the subject, for example, the operator operates the biological information measuring device S by operating an input device (not shown). More specifically, the control unit 31 of the controller 3 operates the light emitting units a to f and the light detection units A to F.

  First, light emission by the light emission portions a to f will be described. When the operation of the biological information measuring device S is started, the control unit 31 of the controller 3 causes the light emitting units a to f to generate (emit) modulated light having specific wavelengths of 840 nm and 770 nm. First, the baseband output device 13 is operated. As a result, the two light generation devices 10 simultaneously start the emission of modulated light having specific wavelengths of 840 nm and 770 nm, respectively.

  That is, in each light generation device 10 of the light emitting units a to f, each spreading code sequence generator 11 generates a gold code sequence as a PN sequence, for example. The spreading code sequence generator 11 outputs the generated PN sequence to the control unit 31 of the controller 3 and also outputs it to the first multiplier 12. As a result, the first multiplier 12 takes the product of the DC signal (baseband signal) supplied from the baseband output unit 13 and the PN sequence, and performs spread spectrum modulation on the DC signal.

  Subsequently, the spread spectrum modulated primary modulation signal is output to the second multiplier 14. Then, the second multiplier 14 supplies the secondary modulation signal obtained by modulating the primary modulation signal using the clock frequency 2f supplied from the clock generator 32 to the light source driver 15, whereby 2 of each of the light emitting units a to f. Each of the two light sources 16 emits modulated light having a specific wavelength to incident positions a to f.

  Here, as described above, in the light source 16, the light emitting element 16b is accommodated in the grounded shield case 16a, and the modulated light is transmitted through the emission window 16c electrically connected to the shield case 16a. Are emitted. Thereby, electromagnetic waves generated when the light emitting element 16b performs a light emission operation, that is, a noise electric field (noise) is prevented from leaking to the outside due to the conductivity of the shield case 16a, and the transparent conductive film 16c2 of the emission window 16c Leakage to the outside is prevented by being electrically connected to the shield case 16a. That is, the light source 16 emits modulated light having a specific wavelength to the incident positions a to f, but it is possible to effectively prevent a noise electric field (noise) generated due to the light emission operation from leaking to the outside. it can. Accordingly, it is possible to prevent the generated noise electric field (noise) from propagating to the light detection units A to F through the living body (human body), for example, and adversely affecting the detection of the reflected light by the light receiver 22. . Therefore, the detection accuracy of reflected light by the light detection units A to F can be improved, and as a result, the measurement accuracy of biological information can be improved.

  In this way, the modulated light emitted from the light source 16 to each of the incident positions a to f passes through the skull of the subject's head T, enters the frontal lobe, for example, and diffusely reflects in the brain. In other words, it propagates with attenuation. Then, the two modulated lights emitted by each of the light emitting parts a to f, that is, the reflected light, pass through the skull of the head T again and reach the surface of the head T.

  Next, detection of reflected light by the light detection units A to F will be described. Each reflected light that has reached the surface of the head T is detected by the light detection units A to F corresponding to the light receiving positions A to F. That is, in the light detection units A to F, each of the light receivers 22 receives all the reflected light reaching the light receiving positions A to F, and electrical detection signals (analog signals) corresponding to the received reflected light. Are output to the amplifier 23 in time series. The amplifier 23 amplifies the input electrical detection signal, and the LPF 24 cuts a signal component having a frequency higher than 2f by passing the amplified detection signal.

  Here, as described above, in the light receiver 22, the light receiving element 22b is accommodated in the grounded shield case 22a, and the reflected light is transmitted through the incident window 22c electrically connected to the shield case 22a. Is incident. Thereby, for example, a noise electric field (noise) due to a myoelectric potential generated in accordance with the movement of the subject and a noise electric field (noise) existing in the outside of the light detection units A to F propagate to the inside due to the conductivity of the shield case 22a. Is blocked, and the transparent conductive film 22c2 of the incident window 22c is electrically connected to the shield case 22a, thereby blocking propagation to the inside. Further, since the amplifier 23 is accommodated in the shield case 22a of the light receiver 22, an external noise electric field (noise) propagating to the amplifier 23 is also blocked.

  Further, since the electrical detection signal (analog signal) output from the light receiver 22 is amplified by the low impedance amplifier 23 and output via the signal output terminal 23b, the output electrical detection signal ( It is possible to prevent a noise electric field (noise) existing outside the analog signal). Furthermore, since a coaxial cable is connected to the signal output terminal 23b of the amplifier 23, noise that exists outside the electrical detection signal (analog signal) output to the LPF 24 via the signal output terminal 23b. An electric field (noise) can be prevented from riding.

  That is, in the light receiver 22, although reflected light having a specific wavelength is incident at the light receiving positions A to F, myoelectric potential and other electromagnetic waves, that is, noise electric fields (noise) are effectively blocked from propagating to the light receiving element 22b. can do. In the amplifier 23, the propagation of myoelectric potential and other electromagnetic waves, that is, the noise electric field (noise) is blocked, and the amplified electrical detection signal (analog signal) is output to the LPF 24 with low impedance. It is possible to prevent the noise electric field (noise) existing in the signal from being on the electrical detection signal (analog signal). Thereby, it is possible to prevent the noise electric field (noise) from adversely affecting the detection of the reflected light by the light receiver 22 and the output of the electrical detection signal (analog signal) by the amplifier 23. Therefore, the detection accuracy of reflected light by the light detection units A to F can be improved, and as a result, the measurement accuracy of biological information can be improved.

  Subsequently, the AD converter 25 performs a digital conversion process on the electrical detection signal (analog signal) that has passed through the LPF 24 at the sampling frequency 4f. The electrical detection signal (digital signal) subjected to the digital conversion processing is output to the first multiplier 26, and the first multiplier 26 converts the input electrical detection signal (digital signal) to the clock frequency 2f. The detected signal, that is, the primary demodulated signal is output to the second multiplier 27. By demodulating in this way, the demodulated signal becomes a signal using the entire effective detection bandwidth 2 f of the light receiver 22. In other words, it is possible to accurately convert the information that the modulated light that can be received by the optical receiver 22 has, for example, the attenuation state of the modulated light that has propagated around the frontal lobe (that is, the light intensity of the reflected light) into a digital signal. The primary demodulated signal can be output to the second multiplier 27.

  By the way, each modulated light emitted from the incident positions a to f reaches the light receiving positions A to F as reflected light. For example, at the light receiving position A, not only the modulated light emitted from the incident positions a, b, c, and d located in the periphery, but also the modulated light emitted from the incident positions e and f is reflected light. To reach. In such a situation, the control unit 31 of the controller 3 includes, for example, a living body corresponding to the reflected light of the modulated light emitted from the incident positions a, b, c, and d among the reflected light reaching the light receiving position A. The light detection unit A is controlled so that only the information signal is obtained. The control by this control part 31 is demonstrated concretely.

  As described above, the control unit 31 of the controller 3 acquires the PN sequence from the spread code sequence generator 11 of each light generation device 10. On the other hand, the second multiplier 27 of the light detection unit A acquires the PN sequence generated by the spreading code sequence generator 11 of the light emitting units a to f via the control unit 31 of the controller 3. At this time, the control unit 31 transmits the different PN sequences generated by the spread code sequence generators 11 of the light emitting units a, b, c, and d via the delay 33 to the second multiplier corresponding to the light detection unit A. 27.

  Thus, each second multiplier 27 takes the product of the primary demodulated signal output from the first multiplier 26 and the corresponding PN sequence supplied from the control unit 31 of the controller 3, in other words, spectrum despreading. The secondary demodulated signal obtained in this way is output to each accumulator 28. Each accumulator 28 adds the output secondary demodulated signal over one period or more of the PN sequence. In this way, the product-sum processing by the second multiplier 27 and the accumulator 28 corresponding to the emitted modulated light can correlate the secondary demodulated signal with the supplied PN sequence, and the light emission A plurality of biological information signals corresponding to a plurality of modulated lights emitted from the parts a, b, c, and d can be simultaneously output.

  That is, as described above, the PN sequence has the property that different sequences are orthogonal to each other, in other words, the property value of the product of different sequences is “0”. For this reason, when the PN sequence by the spreading code sequence generator 11 corresponding to the light emitting unit a is supplied to the second multiplier 27 with the control unit 31 of the controller 3, for example, the first multiplier 26. Among the primary demodulated signals output from, the product value of the primary demodulated signal other than the primary demodulated signal corresponding to the specific modulated light emitted from the light emitting part a and the PN sequence of the light emitting part a is “0”. " Therefore, the secondary demodulated signal added by the accumulator 28 over one period of the PN sequence is also “0”, and the correlation is “0”.

  Therefore, the secondary demodulated signal that does not have (or does not match) the PN sequence supplied from the control unit 31 of the controller 3, in other words, the biological information signal is selectively excluded, and the specific second multiplier 27 and the cumulative signal are accumulated. Only the biological information signal corresponding to the reflected light of the specific modulated light emitted from the light emitting unit a is output from the calculator 28 to the control unit 31 of the controller 3. Similarly, the controller 31 of the controller 3 supplies the second multiplier 27 with, for example, the PN sequence from the spread code sequence generator 11 corresponding to the other of the light emitting portions a, so that the second The biological information signal corresponding to the reflected light of the other specific modulated light emitted from the light emitting part a is simultaneously output from the 2 multiplier 27 and the accumulator 28 to the controller 3. Similarly, when the PN series of the other light emitting units b, c, d is supplied from the control unit 31 of the controller 3 to the second multiplier 27, the light emitting units b, c, Each biological information signal corresponding to the reflected light of the plurality of modulated lights emitted from d is simultaneously output to the controller 31 of the controller 3. Here, since the light detection unit A detects the modulated light emitted by the light emission units a to d, the light detection unit A and the light emission unit a, the light detection unit A and the light emission unit b, and the light detection unit A. 4 channels of the light emitting part c, the light detecting part A and the light emitting part d are formed.

  Thereby, the light detection part A is the biological information corresponding to the reflected light of the modulated light emitted by the light emitting parts a to d among the modulated light having specific wavelengths emitted from the light emitting parts a to f. The signal is output to the control unit 31 of the controller 3. Similarly to the light detection unit A, the light detection units B to F are emitted from specific light emission units among the light emission units a to f by being controlled by the control unit 31 of the controller 3. A plurality of biological information signals corresponding to the reflected light of the modulated light are simultaneously output.

  When the biological information signals are output from the light detection units A to F in this way, the control unit 31 of the controller 3 uses the output biological information signals in the subject's brain (for example, around the frontal lobe). The oxygenated hemoglobin concentration length change ΔCoxy and the reduced hemoglobin concentration length change ΔCdeoxy are calculated. The calculation of the oxygenated hemoglobin concentration length change ΔCoxy and the reduced hemoglobin concentration length change ΔCdeoxy will be specifically described below, but the calculation method itself is not a feature of the present invention. That is, the oxygenated hemoglobin concentration length change ΔCoxy and the reduced hemoglobin concentration length change ΔCdeoxy are exemplarily shown as biological information that can be measured by the biological information measuring device A. For this reason, various known methods can be employed for calculating oxygenated hemoglobin concentration length change ΔCoxy and deoxyhemoglobin concentration length change ΔCdeoxy, and the following explanation will limit the calculation method. Not intended.

As described above, oxygenated hemoglobin and reduced hemoglobin in arterial blood and venous blood absorb near infrared light due to different light absorption characteristics. The absorption characteristics of near-infrared light in oxygenated hemoglobin and reduced hemoglobin can be generally expressed by the following formula 1 according to Lambert-Beer's law.
−ln (R (λ) / Ro (λ)) = εoxy (λ) × Coxy × d + εdeoxy (λ) × Cdeoxy × d + α (λ) + S (λ) Equation 1

  However, R (λ), Ro (λ), and d in the equation 1 respectively represent the detected light amount of the wavelength λ, the emitted light amount of the wavelength λ, and the optical path length of the detection region, as schematically shown in FIG. It represents. Further, εoxy (λ) in the above formula 1 represents the molecular extinction coefficient of oxygenated hemoglobin with respect to the wavelength λ, and εdeoxy (λ) represents the molecular extinction coefficient of reduced hemoglobin with respect to the wavelength λ. In the formula 1, Coxy represents the concentration of oxygenated hemoglobin, and Cdeoxy represents the concentration of reduced hemoglobin. Further, α (λ) in the above formula 1 represents the attenuation due to light absorption of a pigment other than hemoglobin in blood (for example, cytochrome aa33 reflecting the supply and demand of oxygen in mitochondria in cells). (λ) represents the attenuation due to light scattering of the living tissue.

  Thus, according to Equation 1, the oxygenated hemoglobin concentration Coxy and the reduced hemoglobin concentration Cdeoxy in the case of using near-infrared light having a wavelength of 840 nm and near-infrared light having a wavelength of 770 nm are calculated. be able to. Accordingly, the blood flow change can be calculated by calculating the ratio Coxy / Cdeoxy between the oxygenated hemoglobin concentration Coxy and the reduced hemoglobin concentration Cdeoxy.

For example, if the light absorption characteristic before blood flow change is expressed according to the above-described equation 1 for the capillary blood vessels existing in the brain, the light absorption characteristic after blood flow change can be expressed as shown in the following equation 2.
−ln (growthR (λ) / Ro (λ)) = εoxy (λ) × growthCoxy × d + εdeoxy (λ) × growthCdeoxy × d + growthα (λ) + S (λ) Equation 2
However, growthR (λ), growthCoxy, growthCdeoxy, and growthα (λ) in Equation 2 above represent values that have increased or decreased due to changes in blood flow associated with the heartbeat. It shows the amount of light detected, the concentration of oxygenated hemoglobin after the change in blood flow, the concentration of reduced hemoglobin after the change in blood flow, and the attenuation due to light absorption of pigments other than hemoglobin after the change in blood flow.

Here, since the light absorption amount of hemoglobin in the blood is extremely larger than the light absorption amount of a dye other than hemoglobin, α (λ) in the above equation 1 is expressed as α (λ) = growthα (λ). be able to. Thus, subtracting the formula 1 from the formula 2 yields the following formula 3.
−ln (growthR (λ) / R (λ)) = εoxy (λ) × ΔCoxy + εdeoxy (λ) × ΔCdeoxy Equation 3
Here, ΔCoxy and ΔCdeoxy in Formula 3 are represented by Formula 4 and Formula 5 below, respectively.
ΔCoxy = (growthCoxy−Coxy) × d Equation 4
ΔCdeoxy = (growthCdeoxy−Cdeoxy) × d (Formula 5)

  Then, as schematically shown in FIG. 10, the light absorption spectrum of hemoglobin is based on the result of measurement using near infrared light of λ = 770 nm or 840 nm as a specific wavelength where the contrast ratio of the light absorption characteristic becomes clear. By solving Equation 3, it is possible to relatively calculate oxygenated hemoglobin concentration length change ΔCoxy and reduced hemoglobin concentration length change ΔCdeoxy including the optical path length, or total hemoglobin concentration length change (ΔCoxy + ΔCdeoxy) as dimensions.

  The control unit 31 of the controller 3 calculates the calculated oxygenated hemoglobin concentration length change ΔCoxy and the reduced hemoglobin concentration length change ΔCdeoxy, that is, biological information, and outputs the calculated biological information to the display unit 4. And the display part 4 displays the blood flow change in a brain by a two-dimensional or three-dimensional aspect, for example.

  As can be understood from the above description, in the biological information measuring device S, the light receiver 22 of the light detection unit 2 is used even if it is extremely weak reflected light (modulated light) attenuated by propagating inside the living body. Is electromagnetically shielded by the shield case 22a and the incident window 22c, for example, it is possible to detect reflected light (modulated light) by eliminating the influence of noise electric field (noise) due to myoelectric potential generated in the living body. it can. Further, since the amplifier 23 is accommodated in the shield case 22a of the light receiver 22, the noise electric field (noise) propagating through the amplifier is also cut off. Further, the amplifier 23 includes an operational amplifier and can output an electrical detection signal (analog signal) with low impedance. For this reason, it is possible to prevent a noise electric field (noise) existing outside from being applied to an electrical detection signal (analog signal) to be output, and to achieve good signal output performance (good S / N ratio). Can be secured. Thereby, the control part 31 of the controller 3 can measure (calculate) biological information very accurately.

  Further, in the biological information measuring device S, the light source 16 of the light emitting unit 1 can also be electromagnetically shielded by the shield case 16a and the emission window 16c. Therefore, it is possible to prevent the emission (radiation) of the noise electric field (noise) generated with the operation of the light emitting element 16b of the light source 16, and the influence on the detection of the extremely weak reflected light by the light receiver 22 of the light detection unit 2. Can be greatly reduced. Also by this, the control part 31 of the controller 3 can measure (calculate) biological information very accurately.

a. First Modification In the above-described embodiment, the light emitting unit 1 includes two light generation devices 10, each light generation device 10 includes one light source 16, and receives modulated light having two specific wavelengths. It implemented so that it might radiate | emit. In this case, it is also possible to accommodate a plurality of light emitting elements 16b in one shield case 16a and emit modulated light having a plurality of specific wavelengths from one light source 16. Specifically, for example, when modulated light having two specific wavelengths is emitted from one light source 16, two light emitting elements 16b are provided in the shield case 16a as shown in FIG. Accommodate. Here, when two light emitting elements 16b are accommodated, as shown in FIG. 8, the anode electrode 16b1 connected to each light emitting element 16b is used as a common electrode, and the cathode electrode 16b2 connected to each light emitting element 16b. Should be connected separately. Also in this case, the shield case 16a is electrically installed via the shield electrode 16a1 as in the above embodiment.

  Thus, by emitting modulated light having a plurality of specific wavelengths from one light source 16, the number of modulated lights to be emitted (that is, the number of specific wavelengths to be emitted) is increased according to the measurement target. Even if it is necessary, the number of the light generating devices 10 included in the light emitting unit 1 can be reduced. As a result, the light emitting unit 1 itself can be reduced in size, and the light emitting unit 1 can be densely arranged with respect to the measurement site (for example, the head T of the subject). Thereby, the resolution at the time of measuring living body information can be raised, measurement accuracy can be improved, and more exact living body information can be obtained.

b. Second Modification In the above embodiment, the incident window 22c of the light receiver 22 in the light detection unit 2 is configured from the transparent base material 22c1 and the transparent conductive film 22c2. In this case, in order to further improve the detection accuracy of the reflected light, as shown in FIGS. 12 and 13, it is possible to provide an optical filter 22c3. Here, the optical filter 22c3 has an optical characteristic that transmits only a specific wavelength of reflected light. For example, the color filter shown in FIG. 12 or a cut filter that removes (cuts) short-wavelength light. Alternatively, a band-pass filter or the like in which dielectric layers having different refractive indexes shown in FIG. 13 are stacked can be employed.

  As described above, by providing the optical filter 22c3 on the incident window 22c of the light receiver 22, external light (for example, illumination light) existing in the measurement environment is incident on the light receiving element 22b via the incident window 22c. It can be reliably shut off. As a result, it is possible to remove noise components associated with the incidence of external light, and to increase the S / N ratio of the biological information signal corresponding to the light intensity of the reflected light. Therefore, measurement accuracy can be improved and more accurate biological information can be obtained.

c. Third Modification In the above-described embodiment, the incident window 22c of the light receiver 22 in the light detection unit 2 includes a flat transparent substrate 22c1 and a transparent conductive film 22c2 formed on at least one surface side of the substrate 22c1. It was composed and implemented. In this case, in order to further improve the detection accuracy of reflected light, as shown in FIG. 14, a transparent base material 22c1 is formed in a lens shape, and a transparent conductive film is formed on at least one surface side of the transparent base material 22c1 formed in this lens shape. It is also possible to carry out by forming 22c2. In FIG. 14, an optical filter 22c3 is formed on the other surface side of the transparent substrate 22c1 formed in a lens shape. In this way, by forming the incident window 22c of the light receiver 22 into a lens shape, it is possible to efficiently condense or collimate extremely weak reflected light, so that the light of the reflected light incident on the light receiving element 22b. Strength can be increased. As a result, the S / N ratio of the biological information signal corresponding to the light intensity of the reflected light can be increased, the measurement accuracy can be improved, and more accurate biological information can be obtained.

d. Fourth Modification In the above embodiment, the light receiver 22 of the light detection unit 2 includes the shield case 22a, and the light receiving element 22b and the amplifier 23 are integrally accommodated in the shield case 22a. In this case, the light receiver 22 and the amplifier 23 can be separated from each other. In this case, as shown in FIG. 15, in order to block external electromagnetic waves that affect the light receiver 22 and the amplifier 23 that are electrically connected to each other, the light detection unit 2 includes the light receiver 22 and the amplifier. 23 and an electromagnetic shielding case 29 for electromagnetic shielding. In this case, the formation of the transparent conductive film 22c2 can be omitted in the incident window 22c of the light receiver 22.

  The electromagnetic shield case 29 includes a main body 29a and an incident window 29b. The main body 29 a is made of a metal material or a conductive resin material to block external electromagnetic waves, and is grounded via the ground terminal 23 c of the amplifier 23. The incident window 29b optically transmits reflected light to the light receiver 22, and includes a transparent conductive film 29b1, a dielectric multilayer filter 29b2, and a cover glass 29b3. The transparent conductive film 29b1 is formed, for example, by thinning the bulk material of ITO, ZnO, or NbO described above. The transparent conductive film 29b1 is electrically connected to the conductive main body 29a via, for example, a conductive adhesive. The dielectric multilayer filter 29b2 is a band transmission filter in which dielectric layers having different refractive indexes are laminated, and is laminated on the transparent conductive film 29b1. The cover glass 29b3 is made of, for example, quartz (Cortz) or optically transparent transparent plastic, and is laminated on the dielectric multilayer filter 29b2.

  Thus, even when the electromagnetic shield case 29 is provided and the light receiver 22 and the amplifier 23 are accommodated in the case 29, the light receiver 22 receives the reflected light having a specific wavelength as in the above embodiment. And can block electromagnetic waves from the outside world. Further, by providing the electromagnetic shield case 29 in this way, a general-purpose light receiver (such as a photodiode or an avalanche photodiode) generally provided on the market can be adopted as the light receiver 22, thereby reducing the manufacturing cost. It can also be reduced.

  In carrying out the present invention, the present invention is not limited to the above embodiment and each of the above modifications, and various modifications can be made without departing from the object of the present invention.

  For example, in the above-described embodiment and each modified example, the light receiver 22 that integrally accommodates the amplifier 23 detects the extremely weak reflected light that has propagated through the living body and outputs an electrical detection signal with low impedance. This was applied to the biological information measuring device S. In this way, the light receiver 22 that integrally accommodates the amplifier 23 can block the electromagnetic waves in the outside world, accurately detect extremely weak light, and output a good detection signal. For this reason, it is of course possible to detect extremely weak light by using the light receiver 22 that integrally accommodates the amplifier 23 for measurement in another measurement object or other measurement environment.

  Further, in the above-described embodiment and each modified example, the baseband signal is spread with the spread spectrum and the clock frequency 2f in consideration of the fact that the light is greatly attenuated by propagating in the living body and the measurement resolution of the living body information is increased. Based on the modulated secondary modulation signal, the light emission timing of the light source 16 of each light generating device 10 was simultaneously made so that the light emitting unit 1 emits modulated light. On the other hand, the light emission timing of the light source 16 in each light generation device 10 is varied at a predetermined short time interval according to the measurement target and measurement environment, and light such as near infrared light is emitted in pulses. It is also possible to do.

  In this case, in the light emitting unit 1, the spread code sequence generator 11, the first multiplier 12, and the second multiplier 14 are omitted from the light generation device 10 of the light emitting unit 1 in the above-described embodiment and each modification. , A baseband output device 13, a light source driver 15, and a light source 16. Then, the control unit 31 of the controller 3 operates the baseband output device 13 at a predetermined timing, so that the light source driver 15 drives (emits light) the light source 16.

  In this case, the light detection unit 2 is also changed with the change of the light emission unit 1. That is, in the light detection unit 2, the first multiplier 26, the second multiplier 27, and the accumulator 28 of the light detection unit 2 in the embodiment and each modification are omitted, and the light receiver 22, the amplifier 23, It comprises an LPF 24 and an AD converter 25. As described above, even when the light emission timing of the light source 16 is varied at predetermined short time intervals and light such as near-infrared light is emitted in a pulsed manner, the same as in the above-described embodiment and each modification. Can be expected.

  In the embodiment and each modification, the light emitting unit 1 generates a secondary modulation signal obtained by modulating the baseband signal with spread spectrum and the clock frequency 2f, and the two modulated lights are emitted without interfering with each other. Was carried out. On the other hand, the baseband signal from the baseband output unit 13 is frequency-division multiplexed (FDM) modulated to generate a modulated signal, and the interference between the two modulated lights is prevented. It is also possible.

  In this case, the spread code sequence generator 11, the first multiplier 12, and the second multiplier 14 of the light emitting unit 1 in the above embodiment and each modification are omitted, and a frequency division multiplex modulator is provided. In this case, the first multiplier 26, the second multiplier 27, and the accumulator 28 of the light detection unit 2 in the above-described embodiment and each modification are omitted, and a frequency division multiplex demodulator is provided. The operation of the frequency division multiplex modulator and the frequency division multiplex demodulator can be modulated and demodulated by applying a widely known method, and detailed description thereof will be omitted. . Thus, even when the modulation signal is generated by frequency division multiplex modulation and the modulated light is emitted, the same effects as those of the above-described embodiment and each modification can be expected.

  Moreover, in the said embodiment and each modification, it implemented so that the light source 16 of the light emission part 1 might light-emit simultaneously based on the secondary modulation signal by which the spread spectrum modulation was carried out. However, it goes without saying that the light source driver 15 can sequentially cause the light source 16 to emit light based on the secondary modulation signal subjected to spread spectrum modulation.

  Furthermore, in the above-described embodiment and each modification, the biological information measuring device S uses the light absorption characteristic of blood in the living body to calculate the oxygenated hemoglobin concentration length change ΔCoxy and the reduced hemoglobin concentration length change ΔCdeoxy in the subject's brain. Measurement (calculation) was performed as biological information, and blood flow changes in the brain were observed. However, by appropriately changing the specific wavelength of the near-infrared light generated by the light generator 10 constituting the light emitting unit 1, other light absorption characteristics such as the density of the living body, moisture, and glucose concentration in blood ( Needless to say, it is possible to measure light absorption characteristics associated with changes in blood glucose level, lipid content, or pulse, such as oxygen saturation. In this way, even when other light absorption characteristics are used, the biological information can be measured (calculated) more accurately by using the biological information measuring device S according to the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Light emission part, 10 ... Light generator, 11 ... Spread code sequence generator, 12 ... 1st multiplier, 13 ... Baseband output device, 14 ... 2nd multiplier, 15 ... Light source driver, 16 ... Light source, DESCRIPTION OF SYMBOLS 2 ... Light detection part, 22 ... Light receiver, 22a ... Shield case, 22b ... Light receiving element, 22c ... Incident window, 22c1 ... Transparent base material, 22c2 ... Transparent conductive film, 23 ... Amplifier, 23a ... Operational amplifier, 24 ... LPF, 25 ... AD converter, 26 ... first multiplier, 27 ... second multiplier, 28 ... accumulator, 29 ... electromagnetic shield case, 3 ... controller, 31 ... control unit, 32 ... clock generator, 33 ... delay, 4 ... Display unit, S ... Biometric information measuring device

Claims (24)

A light detection device for detecting light,
A conductive case that is conductive and grounded;
A window portion that has optical transparency with respect to the wavelength of light to be detected and has electrical conductivity, is electrically connected to the conductive case, and receives light;
A photoelectric conversion element that is received in the conductive case and receives light incident from the window and converts it into an electrical detection signal;
The electrical detection signal received in the conductive case and output from the photoelectric conversion element is amplified, and the amplified electrical detection signal is output with an output impedance smaller than the output impedance of the photoelectric conversion element. An optical detection device comprising: The photodetection device according to claim 1,
The window portion,
A transparent substrate having optical transparency for the wavelength of the light to be detected;
A photodetecting device comprising: a transparent conductive film which is laminated on at least one surface side of the transparent base material and has optical transparency with respect to a wavelength to be measured and electrical conductivity. The photodetection device according to claim 2,
The transparent conductive film,
A photodetecting device, wherein the transparent base material is laminated on at least one surface side together with at least one dielectric layer having a band transmission property that selectively transmits a wavelength of light to be detected. The photodetection device according to claim 2,
The transparent conductive film constituting the window is
A photodetection device comprising yttrium-tin oxide (ITO), zinc oxide (ZnO) or niobium oxide (NbO) as a main component. The photodetection device according to claim 1,
The amplifier circuit is
An optical detection device comprising an operational amplifier having a large input impedance. The photodetection device according to claim 1,
The photoelectric conversion element is
A photodetection device which is a photodiode or an avalanche photodiode. In a biological information measuring device that detects light propagating through a living body and measures biological information of the detected light,
A light emitting unit that has at least two light sources, emits the light sources based on a predetermined drive signal, and emits near-infrared light having different specific wavelengths into the living body;
A conductive case that is electrically conductive and grounded, and has optical transparency with respect to a specific wavelength emitted from the light emitting part and has electrical conductivity and is electrically connected to the conductive case. A window portion for receiving light, a photoelectric conversion element that is received in the conductive case and receives light incident from the window portion and converts it into an electrical detection signal, and is received in the conductive case. An amplification circuit for amplifying an electrical detection signal output from the photoelectric conversion element and outputting the amplified electrical detection signal with an output impedance smaller than an output impedance of the photoelectric conversion element, An electrical detection signal related to the metabolism of the living body corresponding to the light intensity of the near-infrared light detected and received from near-infrared light emitted from the light emitting part and propagated inside the living body A light detection unit for outputting,
A control unit that controls the operations of the light emitting unit and the light detection unit in an integrated manner and calculates biological information based on an electrical detection signal output from the light detection unit. Biological information measuring device. The biological information measuring device according to claim 7,
The window portion,
A transparent substrate having optical transparency for the specific wavelength;
A biological information measuring device, comprising: a transparent conductive film which is laminated on at least one surface side of the transparent substrate and has optical transparency with respect to the specific wavelength and electrical conductivity. In the biological information measuring device according to claim 8,
The transparent conductive film,
A biological information measuring device, wherein the transparent substrate is laminated on at least one surface side together with at least one dielectric film having band transmission property that selectively transmits the specific wavelength. In the biological information measuring device according to claim 8,
The transparent conductive film constituting the window is
A biological information measuring device formed of yttrium-tin oxide (ITO), zinc oxide (ZnO) or niobium oxide (NbO) as a main component. The biological information measuring device according to claim 7,
The amplifier circuit is
A biological information measuring device comprising an operational amplifier having a large input impedance. The biological information measuring device according to claim 7,
The photoelectric conversion element is
A biological information measuring device which is a photodiode or an avalanche photodiode. The biological information measuring device according to claim 7,
The light source is
A conductive case that is conductive and grounded;
A window portion having optical transparency with respect to the specific wavelength and having electrical conductivity and electrically connected to the conductive case and transmitting light;
A biological information measuring device comprising: a light emitting element housed in the conductive case and emitting near infrared light having the specific wavelength from the window portion. The biological information measuring device according to claim 13,
A biological information measuring apparatus comprising a plurality of the light emitting elements accommodated in the conductive case. The biological information measuring device according to claim 13,
The window portion,
A transparent substrate having optical transparency for the specific wavelength;
A biological information measuring device, comprising: a transparent conductive film which is laminated on at least one surface side of the transparent substrate and has optical transparency with respect to the specific wavelength and electrical conductivity. The biological information measuring device according to claim 15,
The transparent conductive film constituting the window is
A biological information measuring device formed of yttrium-tin oxide (ITO), zinc oxide (ZnO) or niobium oxide (NbO) as a main component. The biological information measuring device according to claim 13,
The light emitting element is
A biological information measuring device characterized by being a semiconductor laser or a light emitting diode. The biological information measuring device according to claim 7,
The biological information calculated by the control unit is:
The biological information measuring apparatus, which is information representing a change in oxygenated hemoglobin concentration length combined with oxygen in a blood vessel of the living body and a change in reduced hemoglobin concentration length not combined with oxygen. The biological information measuring device according to claim 7,
The light emitting unit emits near infrared light having the specific wavelength to the head of a living body,
The light detection unit receives near infrared light propagated through the head of the living body and outputs the electrical detection signal,
The living body information measuring device, wherein the control part calculates living body information about activity in the brain of the living body. The biological information measuring device according to claim 7,
The light emitting part is
Spread spectrum modulation means for performing spread spectrum modulation on the predetermined drive signal;
The light detection unit is
A biological information measuring apparatus comprising demodulating means for demodulating the electrical detection signal by despreading the spectrum. The biological information measuring device according to claim 20,
Spread spectrum modulation means of the light emitting part,
A spread code sequence generating means for generating a spread code sequence for performing spread spectrum modulation on the predetermined drive signal with a first frequency, and the predetermined drive using the spread code sequence generated by the spread code sequence generating means The primary modulation signal output by the first modulation means is modulated using a first modulation means for spectrum-spreading the signal and outputting a primary modulation signal, and a second frequency that is twice the first frequency. And second modulation means for outputting a secondary modulation signal.
The demodulating means of the light detection unit is
Of the signal band of the electrical detection signal, signal component removing means for removing and outputting a signal component at a frequency near DC and a frequency near DC and a signal component at or above the second frequency, and the near infrared light A signal for converting the electrical detection signal output by the signal component removing means into a digital signal using a third frequency that is twice the second frequency, taking into account the delay associated with propagation in the living body. A primary demodulated signal is output by demodulating the digital signal converted by the signal converting means using the second frequency taking into account the delay associated with the propagation of the near-infrared light in the living body. The first demodulated signal and the spread code sequence taking into account the delay associated with the propagation of the near-infrared light in the living body to despread the primary demodulated signal to obtain a secondary demodulated signal. The biological information measuring apparatus characterized by a second demodulating means for outputting. The biological information measuring device according to claim 21,
The biological information measuring apparatus according to claim 1, wherein the second frequency is matched with an effective detection bandwidth in which the light detection unit can effectively detect near-infrared light propagating in the living body. The biological information measuring device according to claim 7,
The light emitting part is
The predetermined drive signal supplied with a predetermined time interval is acquired, the light sources sequentially emit light based on the acquired predetermined drive signal, and near infrared light having a different specific wavelength is obtained. A biological information measuring device which emits sequentially with a predetermined time interval. The biological information measuring device according to claim 7,
The light emitting part is
Frequency division multiplexing modulation means for generating a modulation signal by frequency division multiplexing modulation of the predetermined drive signal;
The light detection unit is
A biological information measuring apparatus comprising demodulating means for frequency-division multiplex demodulating the electrical detection signal.

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