WO2010122703A1

WO2010122703A1 - Biological light measuring device

Info

Publication number: WO2010122703A1
Application number: PCT/JP2010/001202
Authority: WO
Inventors: 木口雅史; 敦森洋和; 堀田忠宏; 深作泉
Original assignee: 株式会社日立メディコ
Priority date: 2009-04-24
Filing date: 2010-02-23
Publication date: 2010-10-28
Also published as: JPWO2010122703A1

Abstract

Provided are codes with less crosstalk even in a system having band limitation or distortion, and a biological light measuring device using the codes. The biological light measuring device is characterized in that the chips of the respective codes are successively arranged using a plurality of Hadamard codes with different periodicity, whereby new codes appropriate to the measurement of biological light are obtained. Namely, codes with less inter-code crosstalk are obtained and signals can be multiplexed and separated using the codes.

Description

Biological light measurement device

The present invention relates to a biological light measurement device, and more particularly to generation of a code suitable for measurement and biological light measurement using the code.

Code multiplexing (CDM) is used to multiplex signals in fields such as communication and measurement. This is a method of performing signal separation by despreading a signal that has been modulated, that is, spectrum spread using pseudo-noise signals orthogonal to each other, after detection. For example, Non-Patent Document 1 describes that a sensor signal is multiplexed and separated using the CDM method.

Patent Document 1 discloses a biological tissue measurement apparatus that suppresses crosstalk by modulating a plurality of light beams with pseudo-noise signals orthogonal to each other and demodulating on a detector side.

Also, as an example in which the CDM method is applied to a biological information measuring device, Patent Document 2 describes a biological information measuring device that separates two wavelengths of light that irradiates a living body using a pseudo noise signal on the detector side. Here, a plurality of visible to near-infrared light is irradiated on the living body, the light passing through the living body is detected, the concentration change of the body substance such as hemoglobin and the brain blood volume change are measured and the brain activity distribution is displayed. It is written about the device to do. In this device, light sources and detectors are arranged alternately in a grid pattern, and the light emitted from different positions is separated using a single detector. CDM method is used to electrically separate light of different wavelengths.

JP-A-4-166144 JP 2002-248104 A

Compared with applications in the communication field for transmitting and receiving digital signals, crosstalk between signals may be a problem when the CDM method is used to separate analog signals, particularly in the measurement field.

In the CDM system, in principle, crosstalk can be reduced to zero by using Hadamard codes. However, in reality, there was a problem peculiar to CDM in that crosstalk occurs due to band limitation and circuit distortion.

This problem is not a big problem because a system that transmits and receives digital signals, that is, code information, as in optical communication, can eliminate the influence by setting the threshold appropriately or can reduce it extremely.

However, in the case of measurement using the signal amplitude of an analog signal as information, crosstalk is a major factor that reduces measurement accuracy. Especially when it is applied to a biological light measurement device that measures the head, the detected signal is small and the detected light amount may vary greatly depending on the light source due to the influence of hair etc., and crosstalk between signals is a problem. Become. In other words, when the light emitted from the part without hair and the light emitted from the part with hair are received by the same detector, the amount of received light of the former is several times to several tens of times larger than the latter. At this time, in order to accurately measure the latter signal, it is necessary to sufficiently reduce the crosstalk between the signals.

An object of the present invention is to provide a code for reducing crosstalk between signals and a biological light measurement device using the code.

In order to solve the above-described problems, the biological light measurement device of the present invention includes at least a plurality of light irradiation units each having a light source that irradiates light to a living body, and a plurality of detections that receive light reflected or transmitted from the living body. Each of the detector, a control means for controlling at least the light irradiating unit and the detector, a modulation composite carrier code storage unit for storing in advance a modulation composite carrier code different for each light source, and the detector And a demodulating composite carrier code storage unit for storing a demodulating composite carrier code corresponding to the light from the light source.

According to the present invention, it is possible to provide a code for reducing crosstalk between signals and a biological light measurement device using the code.

It is a figure which shows the example of a measurement of a crosstalk suppression ratio at the time of using a Hadamard code | symbol for the biological light measuring device which is an application object of this invention. It is a figure which shows the example of the relationship between the signal voltage in an Hadamard code | symbol and an actual circuit. It is a figure which shows the example of the synthetic code pattern which becomes the 1st Example of this invention. It is a figure which shows the specific example of the code | symbol synthesis | combination in a 1st Example. It is a figure which shows the example of preparation of the synthetic | combination synthetic | combination code | symbol for modulation in a 1st Example. It is a figure which shows the transmission side circuit in a 1st Example. It is a figure which shows the receiving side circuit in a 1st Example. It is a conceptual diagram of the system in a 1st Example. As a modification of the first embodiment, it is a system conceptual diagram in the case where a code storage unit is shared. It is a figure which shows the transmission side circuit structure of the bioinstrumentation apparatus which becomes 2nd Example of this invention. FIG. 10 is a schematic diagram showing multiplexing of received signals when the present invention is used for biological measurement as a third embodiment of the present invention. It is a conceptual diagram of the brain activity measuring device using light in the 3rd example.

In various wireless communication devices such as mobile phones and wireless LANs, the CDM method is adopted as the communication method.
The code used for the CDMA modulation includes a signal called Hadamard code (Wallish Hadamard code).
The features of this code are: (1) excellent correlation that other sequence codes that are Hadamard codes can be completely removed at the code level, and (2) the number of “1” and “0” forming the code is equal. The duty ratio of the signal is 50%. In principle, the crosstalk is zero from the characteristic (1), and since the average power of the signal is not changed by the code and the SN ratio is not changed from the characteristic (2), the Hadamard code is used as a code used for measurement. Is suitable.

Therefore, in the description of the embodiments of the present invention, the Hadamard code will be described as an example.

FIG. 1 shows an example of crosstalk measurement between codes when using a Hadamard code with a code length of 128 bits, which is an embodiment of the present invention. In the figure, the horizontal axis represents a code number (Code Number), and the vertical axis represents a crosstalk suppression ratio (XTalk suppress (dB)). For example, a code with a period of 64 bits concatenates two identical codes, and a code with a period of 32 bits concatenates four identical codes. Yes. The Hadamard code is generated by a generation method using a well-known Hadamard matrix.

Here, the light intensity is modulated using codes 15 and 31, and the signal received through the optical attenuator having the same attenuation rate as the head is demodulated using codes 1 to 128. The logarithm of the ratio of the detected signal amplitude when detected and the detected signal amplitude when demodulated using its own code is used as the crosstalk suppression ratio. That is, the crosstalk suppression ratio increases as the crosstalk decreases.

The Hadamard code is transmitted on a carrier wave having a frequency four times the chip rate. The cycles of the 15th and 31st codes are 16 and 32, respectively. It can be seen that the crosstalk suppression ratio is smaller between codes with the same period than between codes with different periods. The cause is as follows.

Since the Hadamard code is essentially zero in crosstalk at the code level, the crosstalk suppression ratio should be zero for its own code and infinite for other codes. However, crosstalk occurs due to bandwidth limitations in an actual circuit.

2 (a) is band-limited in an actual circuit, the signal voltage of each chip has a trailing edge in time as shown in FIG. 2 (b). For example, although the original code at the time indicated by the dotted line in FIG. 2 is 0, it does not become 0 due to the influence of the previous code 1 (in FIG. 2, an example of 0.02 is shown).

This is equivalent to superimposing a signal whose code is out of phase as a disturbing signal. When a Hadamard code is placed on a carrier wave, if the phase is shifted, another code having the same code length is generated, so that orthogonality is lost, and crosstalk occurs between codes having the same code length. Crosstalk becomes extremely large when the distance between codes is short, and the crosstalk suppression ratio decreases between codes of the same code length.

When a digital signal is handled as in communication, the information to be detected is code information. Therefore, the influence of crosstalk can be eliminated by providing an appropriate threshold value. However, when used for analog measurement as in this specification, it is necessary to detect the signal amplitude, so crosstalk is an error in the detected value itself.

In order to avoid this, a sufficient time interval should be provided between the chips so as not to be affected by the previous chip. However, in this case, the S / N ratio is lowered because the average received light power is reduced. .

Therefore, the characteristics of both the crosstalk suppression ratio and the SN ratio can be improved by using a code in which codes having different code lengths are combined. For example, when the preceding chip affects the immediately following chip but the influence on the next two chips can be ignored, chips of two types of codes having different code lengths are alternately arranged. As a result, signals with the same code length that increase crosstalk are separated from each other by two chips, so crosstalk can be ignored, and the code length of the next chip is different, so that high orthogonality is maintained. So crosstalk will not increase. If the response time constant of the circuit is low and a chip that is more than two chips is affected, similarly, crosstalk can be reduced by combining three or more types of codes having different code lengths.

In addition, it is mathematically guaranteed that codes synthesized using orthogonal codes are orthogonal to each other. When the CDM method is used for multiplexing and demultiplexing signals for measurement purposes, the order, timing, combination, etc. of transmission and reception can all be set in advance, unlike communication applications.

Therefore, modulation codes and demodulation codes can be created and stored in advance and used as needed. For example, when the present invention is used for channel separation, a composite code may be created and assigned for each channel in advance. Furthermore, a code (modulation composite carrier code) when superimposed on a carrier wave signal may be created and stored in advance.

The reception side may perform demodulation by using the same code as the demodulation signal and multiplying the received signal with a delay if necessary. In communications, etc., the phase of the received signal cannot be predicted, so it is necessary to synchronize the phase of the demodulated signal and the received signal. However, in measurement applications as described here, the phase difference between the demodulated signal and the received signal is also designed in advance. The optimum delay time can be set in advance. Therefore, this delay time is given to the modulation composite carrier code and used as a demodulation composite carrier signal. For the delay, a well-known delay circuit can be used. Furthermore, in the modulation composite carrier code and the demodulation composite carrier code, one bit is subdivided in time, stored with an appropriate time delay, that is, a phase difference, and transmitted at the same timing. By using for reception, demodulation can be easily performed without using a delay circuit.

The time tailing of the chip that causes the above-mentioned crosstalk often occurs due to band limitation in the reception system, but may also occur in the transmission system, that is, the laser drive circuit. Even in either case or both, crosstalk can be reduced by the present invention.

The following describes the case where the intensity of light is modulated by a code, but phase modulation or frequency hopping modulation may be performed. Also, a method used in communication such as an orthogonal frequency division multiplexing method can be used. Further, here, Hadamard code is given as an example, but it can be similarly applied to a code whose orthogonality is reduced with respect to phase shift. For example, when using a Gold code or an M-sequence code having a short inter-code distance, a code synthesized with a code having a long inter-code distance may be created.

Next, a specific configuration of the biological light measurement apparatus according to the first embodiment of the present invention will be described. First, an example of the composite code pattern in the first embodiment of the present invention will be described with reference to FIG. In FIG. 3, a chip with a code of period A is a, a chip with a code of period B is b, a chip with a code of period C is c, and different codes with the same period are represented by subscripts n, k, and the like. .
The number in parentheses represents the chip number. Three new composite codes created by alternately arranging these are (a) to (c) in FIG. The code length of these composite codes is 2N.

Since the cycle is represented by a power of 2, each code can be made a code length that is an integral multiple of the maximum cycle by repeating itself.

FIG. 3D shows an example in which the signs of an and ak are the same in the first half and the second half, but different in the case where the period a is N / 2 and the period c is N. FIG. 3 (e) shows an example in which the symbols an and ak which should be alternately arranged with the symbol c are alternately used.
Further, (f) in FIG. 3 is a composite code synthesized using three codes having different periods. Here, although the synthesis method of (a) of FIG. 3 is used, three codes may be synthesized using the synthesis method of (d) and (f) of FIG.

Next, a specific example of generating an actual Hadamard code using this will be described. (A) and (b) of FIG. 4 are the code | symbol of the code number 42, and the code | symbol number 96, respectively, The synthetic code which combined these chips | tips alternately is shown in FIG.4 (c). The period of (a) in FIG. 4 is 64, and the period of (b) is 128.

(A) in FIG. 5 shows a modulation waveform corresponding to the composite code in FIG. 4 (c), and (b) in FIG. 5 is a carrier wave having a bit rate four times that. In order to superimpose (a) in FIG. 5 on (b), exclusive OR of waveforms (a) and (b) is taken. The modulation composite carrier code thus obtained is shown in FIG.

Next, an example in which the above-described reference numeral of FIG. 5 is applied to a biological light measurement device will be described with reference to FIGS. First, FIG. 6 is a schematic diagram of a transmission-side light source and a drive circuit (light irradiation units 101 and 102), which are light irradiation units of the biological light measurement apparatus.

The modulation composite carrier code c1 shown in FIG. 5C is stored in advance in the modulation composite carrier code storage unit 111 of the light irradiation unit 101, and this code is converted into an analog signal using the DA converter 113. After that, it is input to the laser drive circuit 114, the semiconductor laser 115 as the light source is driven, and the output is intensity-modulated by the modulation composite carrier code c1.

Similarly, another modulation composite carrier code c2 stored in the modulation composite carrier code storage unit 121 of the light irradiation unit 102 is converted into an analog signal by using the DA converter 123, and then is sent to the laser drive circuit 124. The semiconductor laser 125 which is inputted and driven as another light source is driven. The modulation composite carrier code c2 is created in the same manner using the code number 43 and the code number 97.

The wavelengths of the two

semiconductor lasers

115 and 125 are different, and the two output lights are multiplexed by the transmission side optical fiber 100, guided to the living body as the subject, and irradiated. Here, the wavelength is assumed to be about 680 nm to 850 nm which is easily transmitted through the living body, but it is not necessarily within this range.

FIG. 7 is a schematic diagram of a circuit on the receiving side which is a light receiving unit of the biological light measuring device. The two wavelengths of light transmitted through the living body are guided to the photodetector 601 by the receiving side optical fiber 600, are photoelectrically converted, are amplified by the preamplifier 602, and are digitized by the AD converter 603.

Thereafter, the digitized data is multiplied by a demodulating composite carrier code c ′ 1 stored in advance in the demodulating composite carrier code storage unit 612 by a multiplier 610, and is multiplied by a predetermined number of chips by an integrator 611. Integration is performed (an integer multiple of the maximum value of the combined code length). Note that the demodulated composite carrier code storage unit 612, the multiplier 610, and the integrator 611 may be stored in the light receiving unit, or may be incorporated in the control unit 701 described later.

The signal of the output 613 of the integrator 611 obtained in this way is proportional to the light intensity emitted from the light source 115 and detected by the detector 601.
Here, the demodulation composite carrier code c′1 is obtained by replacing 0 of the corresponding modulation composite carrier code c1 with −1.

Similarly, the data digitized by the AD converter 603 is multiplied by the demodulating composite carrier code c ′ 2 stored in advance in the demodulating composite carrier code storage unit 622 by the multiplier 620, and determined in advance by the multiplier 621. Integration is performed for the number of chips obtained (an integral multiple of the maximum value of the combined code length). The signal at the output 623 of the integrator 621 is proportional to the received light intensity emitted from the light source 125 and detected by the detector 601 using the demodulating composite carrier code c'2 corresponding to the modulating composite carrier code c2.

FIG. 8 shows an overall conceptual diagram of the biological light measurement system. Modulating composite carrier codes c1 and c2 are assigned in advance to the

light sources

115 and 125 in the

light irradiation units

101 and 102, respectively, and demodulation corresponding to the photodetector 601 that should receive the light from the light sources. Composite carrier codes c′1 and c′2 are assigned and stored in modulation composite carrier

code storage units

111 and 121 and demodulation composite carrier

code storage units

612 and 622, respectively. (DA

converters

113 and 123 are not shown).

The transmission side circuit shown in FIG. 6 and the reception side circuit shown in FIG. 7 are controlled by the control unit 701. Specifically, the

semiconductor lasers

115 and 125 are driven using the codes c1 and c2 stored in the modulation composite carrier

code storage units

111 and 121, and also stored in the demodulation composite carrier

code storage units

612 and 622. The digitized data is demodulated using the demodulated composite carrier codes c ′ 1 and c ′ 2, and after integration, the data is displayed on the display unit 702 or stored in the data storage unit 703. Further, both data display and data storage may be executed.

Since the phase difference between the modulated signal and the demodulated signal is determined by the circuit used, codes having a phase difference can be stored in advance as c1 and c'1.

This will be explained with a simple example. The clock rate of the DA converter 113 and AD converter 603 is set to a constant multiple of the chip rate of the code, and the modulation composite carrier code and the demodulated composite carrier code are resampled at that clock rate to give a phase difference. Are stored in advance in the modulation composite carrier code storage unit 111 and the demodulation composite carrier code storage unit 612. When the chip rate of the modulation composite carrier code or the demodulation composite carrier code is 10 kbps, and the clock of the DA converter and AD converter is 100 kbps, if the modulation composite carrier code is a repetition of 01, for example, 00000000000001111111111 Save as a repeat. When a delay of 20 msec occurs in the received signal, the demodulated composite carrier code is stored as a repetition of 1100000000000011111111 which is a code provided with a phase delay of 20 msec, that is, 2 bits. As a result, it is not necessary to provide a delay circuit or the like, and demodulation operations can be sequentially performed according to a common clock.

As another method for processing the phase difference, as shown in FIG. 9, a phase difference can be provided to the modulation composite carrier code using

delay circuits

811 and 821, and used for demodulation. In this case, the modulation combined carrier code storage unit 111 and the demodulation combined carrier code storage unit 121 do not need to be provided separately, and can be made common by providing them in the control unit 701. However, the delay circuit shown here is widely known, such as one configured as hardware, one configured as software, or one that realizes a phase difference by shifting the timing of the clock read from the code storage unit. Refers to the delay method.

Using the system shown in FIG. 8 or FIG. 9, intersymbol crosstalk was measured when the preamplifier 602 was provided with a 41 kHz low-pass filter. However, the chip rate of the carrier wave was 82 kHz. When the signal level of the output 613 when the light source 115 and the light source 125 are operated is S0, the signal level of the output 613 when the light source 115 is turned off and only the light source 125 is turned on is S1, the crosstalk suppression ratio is It is expressed as 20 × LOG (S0 / S1). As a result of the experiment, a crosstalk suppression ratio of 83.4 dB was obtained.

For comparison, when one cycle of the code (b) is concatenated after two cycles of the code (a) in FIG. 4 and the crosstalk suppression ratio is measured in the same manner for the combined code obtained by repeating this, it is 35.4 dB. there were.

From these results, it was found that the crosstalk suppression ratio was improved by 48 dB by using a new composite code in which chips with different period codes were alternately stacked. Incidentally, the SN ratio at this time was 65 dB when either combination code was used. Although the S / N ratio depends on the received light amount, the S / N ratio does not change because the received light amount is the same for combination codes 1 and 2. In this way, it is possible to improve the measurement accuracy by making the high SN ratio and the high crosstalk suppression ratio compatible.

In addition, although two types of codes with different periods are combined here, when it is necessary to increase the crosstalk suppression ratio, three or more types of codes with different periods are used as shown in FIG. By using the combined code, crosstalk can be further suppressed. At this time, the combined code may be stored in advance as described above.

In the case of a Hadamard code, 64 orthogonal codes can be prepared, corresponding to half the period, such as 64 codes having a period of 128 and 32 codes having a period of 64. The number of orthogonal codes among the combination codes created using two kinds of codes having different periods is the number of codes having the maximum period.

For example, when the maximum period of the code to be used is 128, the number is 64. That is, if a composite code is created using two codes having a period N or less, signals from a maximum of N / 2 light sources can be separated.

In this embodiment, an example of signal separation from a light source of two wavelengths combined by a fiber is shown. However, the wavelengths are not necessarily different, and light from a plurality of arbitrary light sources incident on a certain light receiver. Can be used for signal separation.

According to the present embodiment, it is possible to provide a code for reducing crosstalk between signals and a biological light measurement device using the code.

As a second embodiment of the present invention, an example in which the transmission side circuit configuration of the living body measurement apparatus according to the first embodiment is different will be described with reference to FIG. In the first embodiment, an example is shown in which a code in which a modulation composite code is placed on a carrier wave is prepared in advance.

This may be simple when the carrier frequency is low, but the circuit processing speed may be insufficient when the carrier frequency is desired to be high.

FIG. 10 shows an example of a circuit configuration on the transmission side suitable for that case. In the light irradiation unit 101, the composite code stored in the code storage unit 911 is analog-mounted on the output of the carrier wave generation circuit 912 by the mixer 913, and the semiconductor laser 115 is amplitude-modulated by the laser driving circuit 114. Similarly, in the light irradiation unit 102, the composite code stored in the code storage unit 921 is analogly placed on the output of the carrier wave generation circuit 922 by the mixer 923, and the semiconductor laser 125 is amplitude-modulated by the laser driving circuit 124. If the speed of the AD conversion and the subsequent processing circuit is insufficient on the receiving circuit side as well, it is only necessary to obtain a baseband signal, that is, a composite code, and then perform AD conversion and demodulate.
As a result, the carrier frequency can be increased while using a transmission side circuit that is inexpensive and has a slow response speed.

Next, a third embodiment of the present invention will be described with reference to FIGS. First, FIG. 11 is a schematic diagram showing multiplexing of received signals as a conceptual diagram when the present invention is used for biological measurement.

Irradiation light sources

1015, 1025, and 1035 provided in the probe portion 2003 of the probe holder are different in positions where they are brought into contact with a living body that is a subject. Lights of three wavelengths from λ1 to λ3 are emitted from the fibers of the respective irradiation light sources. The light detector 1001 is configured such that these lights are simultaneously incident. In this figure, the light from nine light sources is detected simultaneously. In order to distinguish the position and wavelength of the light source, the

irradiation light sources

1015, 1025, and 1035 are intensity-modulated by using the different codes according to the methods described in the first and second embodiments, and the detection signals are demodulated. . Since the demodulated signal is proportional to the light intensity detected when the light emitted from each light source passes through the living body, information inside the living body, such as blood dynamics, can be mapped by a spectroscopic method.

FIG. 12 is a block diagram of an apparatus for measuring a hemodynamic change accompanying brain activity using light and mapping a brain activity state. A transmission side fiber 100 and a reception side optical fiber 600 are arranged in a lattice pattern on a probe holder 1101 attached to the head of a subject. The circuits described in the first and second embodiments are accommodated in the housing 1102. The above-described control unit 701 is also stored in the casing, and computation and analysis for executing mapping and the like using a spectroscopic method are performed by the control unit 701 in the casing 1102 and the calculation / analysis is performed. The result and the like are controlled by the control unit 701 so as to be displayed on the display unit 702.

In Examples 1 and 2, light is transmitted using an optical fiber, but the present invention can also be applied to an apparatus that eliminates the optical fiber by incorporating all or part of the circuit in the probe holder. It is.

The present invention is not limited to the biological measurement apparatus described in the embodiment, and in a measurement apparatus that obtains information on a living body or a substance using a plurality of light or sound waves, a code multiplexing method is used for signal multiplexing and separation. Available when used. For example, a device that measures blood dynamics in a living body using visible to near-infrared light, a device that obtains the spatial distribution of the result, a device that observes the internal structure of a living body using ultrasound, and the sugar content of fruits A device for inspecting the outside from the outside.

DESCRIPTION OF SYMBOLS 100 ... Transmission side optical fiber, 111, 121 ... Modulation synthetic | combination conveyance code memory | storage part, 113, 123 ... DA converter, 114, 124 ... Laser drive circuit, 115, 125 ... Semiconductor laser, 600 ... Reception side optical fiber, 60 ... 1 photodetector, 602 ... preamplifier, 603 ... AD converter, 610, 620 ... multiplier, 611, 621 ... integrator, 612, 622 ... demodulated composite carrier code storage unit, 613, 614 ... output, 701: Control unit, 702: Display unit, 703: Data storage unit, 811, 821 ... Delay circuit, 911, 921 ... Code storage unit, 912, 922 ... Carrier wave generation circuit, 913, 923 ... Mixer, 1001 ...

Photodetector

1015, 1025, 1035... Irradiation light source, 1101... Probe holder, 1102.

Claims

A plurality of light irradiation units each having a light source for irradiating light to a living body;
A plurality of detectors for receiving light reflected or transmitted in the living body;
Control means for controlling at least the light irradiation unit and the detector;
A modulation composite carrier code storage unit that stores in advance a different modulation composite carrier code for each light source;
A demodulating composite carrier code storage unit for storing a demodulating composite carrier code corresponding to the light from the light source to be received by each of the detectors;
A biological light measurement apparatus comprising: a multiplier that multiplies a detection signal detected by the detector with the demodulated composite carrier code; and an integrator that integrates the multiplied detection signal.
The biological light measurement device according to claim 1,
Each of the plurality of light irradiation units is
The light source, the modulation composite carrier code storage unit, a DA converter and a light source driving circuit are provided inside,
Based on the control signal from the control means, the modulation composite carrier code corresponding to the light source stored in the modulation composite carrier code storage unit is converted into an analog signal by the DA converter, and the converted analog A biological light measuring device, wherein a signal is input to the light source driving circuit, and the light emitted from the light source is intensity-modulated by the driving signal based on a modulation composite carrier code.
The biological light measurement device according to claim 1,
The biological light measurement apparatus, wherein the control means includes the demodulation composite carrier code storage unit, the multiplier, and the multiplier.
The biological light measurement device according to claim 1,
The light source is a semiconductor laser;
The biological light measurement apparatus, wherein the light irradiation unit further includes an optical fiber.
The biological light measurement device according to claim 1,
The biological light measuring device, wherein the detector has a light receiving optical fiber.
The biological light measurement device according to claim 1,
A biological light measurement apparatus comprising a display unit capable of displaying the detection signals integrated by the integrator.
The biological light measurement device according to claim 1,
The biometric optical measurement apparatus, wherein the modulation composite carrier code is a code obtained by combining two or more kinds of codes having different periods.
The biological light measurement device according to claim 7,
The biological light measuring device, wherein the code is a Hadamard code.
A plurality of light irradiation units each having a light source for irradiating light to a living body;
A plurality of detectors for receiving light reflected or transmitted in the living body;
Control means for controlling at least the light irradiation unit and the detector;
The control means includes
A modulation composite carrier code storage unit that stores in advance a different modulation composite carrier code for each light source;
A demodulating composite carrier code storage unit for storing a demodulating composite carrier code corresponding to the light from the light source to be received by each of the detectors;
A biological light measurement apparatus comprising: a multiplier that multiplies a detection signal detected by the detector with the demodulated composite carrier code; and an integrator that integrates the multiplied detection signal.
The biological light measurement device according to claim 9,
A biological light measuring device comprising a delay circuit for providing a phase difference between a modulating synthetic carrier code and a demodulating synthetic carrier code in the control means.
The biological light measurement device according to claim 9,
The biometric optical measurement apparatus, wherein the modulation composite carrier code storage unit and the demodulation composite carrier code storage unit are common.