JP4025176B2 - Photo-stimulator and biological light measuring device using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention includes a photostimulation device and a photostimulation device that are used to give a stimulus to a subject when measuring a stimulus response of the subject using an electroencephalograph, a biological light measurement device, or the like. The present invention relates to a living body light measurement apparatus.
[0002]
[Prior art]
2. Description of the Related Art There is known a biological light measuring device that measures biological information such as blood hemoglobin concentration by measuring light that has passed through a living body. The biological light measurement apparatus includes a light source that emits light of a specific wavelength, an irradiation optical fiber that irradiates the surface of the living body with light from the light source, a detection optical fiber that captures light that has passed through the living body, and a detection It includes a photodetector that detects light propagating through the optical fiber and an analysis device that analyzes the detection result. In such a biological light measurement device, when measuring a plurality of measurement points at the same time, the measurement light with different frequency modulation is irradiated for each measurement point, and the passing light for each measurement point is determined by the modulation frequency It has become. These are described in, for example, Patent Documents 1, 2, 3, and the like. The living body light measuring device simply arranges the tip of the light irradiating optical fiber and the tip of the light detecting optical fiber on the surface of the living body and irradiates the light, and easily applies the living body information without harming the living body. Therefore, clinical applications are expected in the field of brain science.
[0003]
On the other hand, a method for measuring the response of a living body to a light stimulus by measuring the electroencephalogram of a living body using an electroencephalograph has been known. In this case, as light stimulation, light emitted by a strobe light or pulsed light emitted continuously by a light stimulation device for an electroencephalograph at a constant cycle is used.
[0004]
Also, when measuring with a living body light measurement device, a method of performing measurement while applying a light stimulus to a living body is known. For this measurement, for example, a light stimulation device for an electroencephalograph is used.
[Patent Document 1]
Japanese Patent Laid-Open No. 09-19408 [Patent Document 2]
JP 63-275323 A [Patent Document 3]
Japanese Patent Application Laid-Open No. 09-149903
[Problems to be solved by the invention]
However, it has been found that noise is generated in the measurement results when the above-described optical stimulation device is used while performing measurement with the biological light measurement device. According to the experiments by the inventors, this noise occurs when the photostimulation device is used near the living body light measurement device, even when the living body light measurement device and the photostimulation device are not directly connected. From this, it seems that the cause of noise is caused by the light emitted from the photostimulation device entering from the tip of the detection optical fiber of the biological light measurement device. In order to prevent this noise, it is conceivable to block the light from the light stimulator by covering the tip of the optical fiber for detection of the biological optical measurement device with a black cloth together with the measurement site. The covering operation is complicated. Also, depending on the measurement site, such as the head of a living body, it may be difficult to cover with a black cloth.
[0006]
An object of the present invention is to reduce the occurrence of noise in the output of a biological light measurement device even when a photostimulation device is used near the biological light measurement device.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, means for substantially removing light having the same frequency component and / or light having the same wavelength as the measurement light used by the biological light measurement device from the stimulation light emitted by the light stimulation device. Is provided. Specifically, (1) by providing means for adjusting the ratio (duty) of the emission time to the period of the pulsed light used as the stimulation light, the biological light measurement device has the same frequency as the modulation component superimposed on the measurement light Reduce ingredients from stimulating light. Alternatively, (2) a light emitting unit that emits light from which the wavelength component of measurement light is removed is used as the light emitting unit for stimulation light. Alternatively, both (1) and (2) are performed.
[0008]
That is, the photostimulation apparatus of the present invention includes, for example, a light emitting unit that emits stimulation light for applying light stimulation to a subject, and a control unit that controls the operation of the light emitting unit and emits periodic pulsed light as stimulation light. The control unit includes a duty setting unit that receives a setting of a ratio of the emission time with respect to the period of the pulsed light in order to reduce a high-frequency component from the stimulation light, and the ratio set by the duty setting unit The pulsed light that fills the light emitting unit is configured to emit light. As a result, since the duty of the stimulation light can be set to an arbitrary size, the pulse width of the stimulation light is widened, and even when the light from the light stimulation device is detected by the biological light measurement device A high frequency component can be prevented from being included in the signal. Therefore, it is possible to reduce the noise of the biological light measurement device due to the high frequency component of the stimulation light.
[0009]
In this case, the control unit includes a period setting unit that receives setting of the period of the pulsed light, a light amount setting unit that receives setting of the amount of light per pulse of the pulsed light, a duty setting unit, a period setting unit, and a light amount setting unit. And a calculation unit that calculates the light intensity satisfying the received duty, cycle, and light quantity by calculation, and the control unit is configured to cause the light emitting unit to emit light with the light intensity calculated by the calculation unit. Can do.
[0010]
Further, as another aspect, the photostimulation device includes a light emitting unit and a control unit that controls the operation of the light emitting unit, and the light emitting unit includes light that does not include the wavelength component of the measurement light of the biological light measurement device. Can be configured to emit light as stimulation light. Thereby, the noise of the living body light measurement apparatus resulting from the overlap of the wavelength components of the stimulation light of the light stimulation apparatus and the irradiation light of the living body light measurement apparatus can be reduced.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
A photostimulation device according to an embodiment of the present invention and a biological light measurement device connected thereto will be described with reference to the drawings.
[0012]
First, the structure of the photostimulation apparatus of this Embodiment is demonstrated using FIG. The photostimulation apparatus 100 according to the present embodiment shown in FIG. 1 includes a light emitting unit 103 that emits stimulation light for applying light stimulation, and a control unit 110 that controls the operation of the light emitting unit 103. The control unit 110 also includes a light amount setting switch 106, a frequency setting switch 105, a duty setting switch 107, and a display device for the user to set a light emission amount, a frequency, and a duty (Duty). 108 is connected. The control unit 110 includes an interface 101 that is connected to the biological light measurement device 200 and receives an input, a light source driver 102 that drives the light emitting unit 103, and the power source 104.
[0013]
The light emitting unit 103 is configured such that the wavelength band of emitted light includes the visible range and does not include the wavelength used by the biological light measurement device 200. In the present embodiment, since the wavelengths used by the biological light measurement device 200 are 780 nm and 830 nm of near infrared light, a white light emitting diode array that does not include these two wavelengths is used as the light emitting unit 103. Here, as shown in FIG. 2, a white light emitting diode having an emission spectrum in the range of 420 nm to 750 nm was used. Since this white light emitting diode does not emit light having a wavelength of 750 nm or more, light that does not include the wavelength used by the biological light measurement device 200 can be emitted as stimulation light. The number of white light emitting diodes constituting the array is designed to be a predetermined number so as to emit light that satisfies the light amount set in the light amount setting switch 106.
[0014]
The structure of the light emitting unit 103 is not limited to a structure using a white light emitting diode array, and may be a structure in which a light source such as a xenon lamp and an infrared light cut filter are combined. In this case, the filter is arranged so that the light emitted from the lamp of the light source passes through the infrared light cut filter. Thereby, the light from which the wavelength used in the biological light measurement device is removed can be irradiated to the living body as stimulation light.
[0015]
The light source driver 102 of the control unit 110 includes a CPU 102a and a switching circuit 102b to drive the light emitting unit 103 and periodically emit pulsed light as shown in FIG. The CPU 102a receives values set from the light amount setting switch 106, the frequency setting switch 105, and the duty setting switch 107, respectively, and based on this, the light intensity during light emission is calculated in advance (light intensity = light quantity / (frequency X Duty)), and how many diodes should be turned on and off based on the obtained light intensity, and the operation of the switching circuit 102b is controlled along with this. The switching circuit 102b turns on and off the current amount instructed by the CPU 102a at the instructed timing and supplies the current amount to the light emitting unit 103. As a result, the light amount, frequency and duty pulse light set by the user in the light amount setting switch 106, frequency setting switch 105 and duty setting switch 107 are emitted from the light emitting unit 103.
[0016]
The amount of light received by the light amount setting switch 106 is the amount of light emitted by the light emitting unit 103 in one pulse (that is, a value obtained by integrating the light emission intensity with the light emission time). In the present embodiment, the light amount setting switch is configured to be able to set the light amount per pulse in the range of 0.01J to 1.0J. This range includes the range of the amount of light emitted per pulse in the conventional photostimulation apparatus, and the amount of light at the same level or an arbitrary level can be set. The frequency at which the frequency setting switch 105 accepts the setting is the reciprocal of the light emission period (= the sum of the light emission time of one pulse and the non-light emission time). The duty at which the duty setting switch 107 accepts the setting is a ratio of the light emission time per light emission cycle (= (light emission time) / (light emission time + non-light emission time) × 100).
[0017]
The interface 101 is connected to a later-described control unit 31 of the biological light measurement apparatus 200 and receives an instruction to start and stop emission of stimulation light from the control unit 31. The interface 101 passes these instructions to the light source driver 102. When the light source driver 102 receives an instruction to start light emission, the light source driver 102 continuously emits pulsed light as stimulation light under the above-described conditions. When the light source driver 102 receives an instruction to end light emission, the light source driver 102 ends light emission of the stimulation light.
[0018]
Next, an outline of the structure of the biological light measurement device 200 connected to the photostimulation device 100 will be described with reference to FIG. The biological light measurement apparatus 200 includes a light source unit 10 that irradiates near-infrared light to a subject 9 that is a living body, a light measurement unit 20 that measures light that has passed through the subject 9 and converts the light into an electrical signal, and optical measurement. A signal processing unit 30 that calculates biological information, for example, blood hemoglobin concentration change based on a signal from the unit 20 and creates a topography image, and a control unit 31 that is connected to control the entire apparatus. have. Furthermore, the biological light measurement apparatus 200 includes a display unit 34 for displaying a topography image, and an input / output unit 33 for inputting instructions necessary for processing of the signal processing unit 30 and outputting signal processing results to the outside. And a storage unit 32 for storing signal processing data and the like, both of which are connected to the control unit 31. The photostimulation apparatus 100 is connected to the control unit 30.
[0019]
The light source unit 10 includes a semiconductor laser 11 that emits light of a plurality of wavelengths in the near infrared, here 780 nm and 830 nm, and a plurality of modulators that modulate these two wavelengths of light at a plurality of different frequencies. The optical module 12 and a plurality of irradiation optical fibers 13 that propagate the modulated light to the subject and emit the modulated light from the exit end face. Note that the wavelength is not limited to these two wavelengths. On the other hand, the optical measurement unit 20 includes a plurality of detection optical fibers 21 for propagating light passing through the subject 9, a photodiode 22 for detecting light propagated by the detection optical fiber 21, and a photodiode 22. A lock-in amplifier module 23 for selectively detecting a signal having a predetermined frequency from the output signal, and an A / D converter 24 for A / D converting the output of the lock-in amplifier module 23 are included.
[0020]
The exit end of the irradiation optical fiber 13 and the entrance end of the detection optical fiber 21 are alternately arranged in a matrix of a predetermined size such as 3 × 3 as shown in FIG. 40. The tips of the optical fibers 13 and 21 and the mounting tool 40 are collectively referred to as a measurement probe. By mounting the mounting tool 40 on the measurement site of the subject 9, the emission end of the irradiation optical fiber 13 and the incident end of the detection optical fiber 21 come into contact with the epithelium of the subject 9. Thereby, near infrared light modulated from the tip of the irradiation optical fiber 13 is irradiated, and the passing light of the subject 9 is taken in from the tip of the adjacent detection optical fiber 21 and detected by the photodiode 22. it can.
[0021]
For example, in the case of a 3 × 3 matrix probe, the center detection optical fiber 21 is detected as a mixture of light irradiated from four adjacent irradiation optical fibers 21 and passing through the subject 9. . Since the illumination signals irradiated from the four adjacent irradiation optical fibers 21 are superimposed with modulation signals having different frequencies, the lock-in amplifier module 23 selects four types of modulation signals included in the mixed light. Thus, information on the subject 9 can be obtained for a point (measurement point) located between the tip of the detection optical fiber 21 and the tip of the adjacent illumination optical fiber 21. Therefore, for example, in the case of a 3 × 3 matrix probe, there are 12 measurement points in total.
[0022]
In addition, the control unit 31 passes a signal requesting the start of light stimulation and a signal indicating the end of light stimulation to the interface 101 of the light stimulation apparatus 100. In response to this, the light stimulation apparatus 100 continuously emits light pulses as stimulation light at a predetermined frequency as described above. Thereby, it is possible to perform measurement with the biological light measurement device 200 while applying a light stimulus to the subject 9.
[0023]
Next, an operation of measuring biological information with the biological light measurement device 200 while irradiating the subject 9 with stimulation light by the optical stimulation device 100 will be described. First, as shown in FIG. 5, the light emitting unit 103 of the photostimulation device 100 is arranged toward the subject 9, and the light irradiation fiber 13 and the light detection fiber 21 of the biological light measurement device 200 are disposed at the measurement site of the subject 9. Is attached with the mounting tool 40. In the example shown in FIG. 5, the measurement site is the human temporal region, and the light emitting unit 103 of the photostimulation apparatus 100 is disposed in front of the head to emit stimulation light toward the eye. In addition, the user sets arbitrary light amounts and frequency values in the light amount setting switch 106 and the frequency setting switch 105. Thereby, measurement can be performed by the biological light measurement device 200 while irradiating the subject 9 with stimulation light having a light amount and frequency desired by the user.
[0024]
At the time of this measurement, as shown in FIG. 5, depending on the positional relationship between the photostimulation device 100 and the measurement probe, the stimulation light emitted from the photostimulation device 100 is transmitted through the detection optical fiber 21 of the living body light measurement device 200. In some cases, the light reaches the tip and enters the detection optical fiber 21 through the gap with the subject 9. In the photostimulation device 100 of the present embodiment, the light pulse is the wavelength of the irradiation light of the biological light measurement device 200. Therefore, the noise level can be greatly reduced.
[0025]
On the other hand, even if stimulation light that does not include the wavelength of near infrared light is used, noise may remain slightly. According to the research by the inventors, this noise is generated when the visible light component of the stimulation light incident on the detection optical fiber 21 of the biological light measurement device 200 is measured by the optical measurement unit 20 of the biological light measurement device 200. This is due to the fact that the high frequency component included in the light pulse signal itself of the stimulus light is measured. That is, even if the stimulation light does not contain near-infrared light, if the pulse waveform is a waveform with a small duty, it contains a high-frequency component in the order of kHz. Since this high frequency component is in the same frequency band as the modulation signal of about 1 to 20 kHz superimposed on the irradiation light by the biological light measurement device 200, it is measured by the optical measurement unit 20 of the biological light measurement device 200 and becomes noise. It is considered to be. In the photostimulation apparatus 100 of the present embodiment, in order to remove this noise, a duty setting switch 107 is provided, and the duty of stimulation light, which is a fixed value in the conventional photostimulation apparatus, is set to an arbitrary magnitude. To be able to. Therefore, the duty is set so that the pulse width of the stimulation light is sufficiently larger than the period of the modulation waveform superimposed on the irradiation light of the biological light measurement device 200 while considering the frequency set in the frequency setting switch 105. Thus, the light pulse of the stimulation light can be prevented from containing a high frequency component, and noise due to the high frequency component can be removed. For example, when the frequency setting switch 105 is set to a frequency of about 10 Hz similarly to the frequency of the pulsed light of the conventional photostimulation apparatus, the biological light measurement device 200 is set by setting the duty setting switch 107 to about 50 or more. It is possible to suppress the generation of high-frequency components having a modulation frequency of 1 to 20 kHz used in the above.
[0026]
A specific example of noise reduction will be described with reference to FIGS. 6 (a), 6 (b), and 6 (c). FIGS. 6A to 6C are graphs showing output waveforms of the biological light measurement device 200 when biological light measurement is performed while applying optical stimulation, and FIG. 6A includes a conventional near-infrared wavelength. When stimulating light is used, (b) uses stimulating light that does not include near-infrared wavelengths, and when the duty is set to the same value as the stimulating light of the conventional optical stimulating device (here, about 8), (c) ) Shows the case where the stimulation light not including the near infrared wavelength is used and the duty is set to 50. In either case, the frequency set in the frequency setting switch 105 is 10 Hz. As can be seen from the graph of FIG. 6B, when visible light that does not include near-infrared wavelengths is used as the stimulation light, compared to the case where stimulation light that includes conventional near-infrared wavelengths is used (a). The noise has been greatly reduced. In this case, however, a little noise remains. As described above, this noise is caused by high frequency components included in the stimulation light. On the other hand, when the duty is set appropriately, as shown in (c), the noise can be almost completely removed.
[0027]
In order to reduce noise due to high frequency components, the pulse width of the stimulation light needs to be sufficiently larger than the period of the modulation waveform superimposed on the irradiation light of the biological light measurement device 200 as described above, and the duty The duty value to be set in the setting switch 107 depends on the frequency used for the modulation of the irradiation light in the biological light measurement device 200 and the frequency set in the frequency setting switch 105 of the photostimulation device 100. Therefore, based on the combination of the modulation frequency of the biological light measurement device 200 known in advance and the frequency within the range that can be set in the frequency setting switch 105, the range of the duty that is desirably set for noise reduction is calculated in advance. It can be configured to be obtained by experiments and displayed on the display device 108 as a recommended duty range to notify the user. Alternatively, the configuration of the duty setting switch 107 can be configured to accept only this desirable duty value.
[0028]
Further, when the frequency range that can be set in the frequency setting switch 105 is wide, a minimum duty value to be set is calculated in advance for each settable frequency value, and the frequency value and the duty value are calculated. Can be stored in a memory (not shown) arranged in the light source driver 102. When the frequency is set in the frequency setting switch 105, the CPU 102a captures this, reads the duty value corresponding to the captured frequency from the memory, and sets the duty value higher than this. It is possible to adopt a configuration in which a display prompting the user is displayed on the display device 108.
[0029]
Further, the CPU 102a performs communication via the interface 101, receives the modulation frequency of the biological light measurement device 200 from the connected biological light measurement device 200, and calculates the minimum value of the duty to be set as described above. It can also be configured to ask for and inform the user.
[0030]
In this embodiment, since the light amount per pulse can be set by the light amount setting switch 106, the light amount per pulse is constant even when the pulse width is widened by the duty setting switch 107. Can be. In general, it is said that the stimulus response generated in the subject by the light stimulus depends on the light amount of the stimulus light, so that the light amount is set to a desired constant value by the light amount setting switch 106 as in the light stimulus device 100 of the present embodiment. By adopting a configuration that can be set to, even when the duty is changed, measurement can be performed while giving a constant stimulus.
[0031]
As described above, the photostimulation apparatus 100 according to the present embodiment is configured not to cause noise in the biological light measurement apparatus 200 even when the stimulation light reaches the measurement probe of the biological light measurement apparatus 200. Has been. Therefore, even when the measurement site of the biological light measurement device 200 is at a position where the stimulation light from the light stimulation device 100 reaches, measurement can be performed with high accuracy.
[0032]
In addition, the above-described photostimulation device 100 includes (1) a configuration using visible light stimulation light that does not include the near infrared wavelength used by the biological light measurement device 200, and (2) a duty setting switch that increases the duty of the light pulse. However, it is not always necessary to have both at the same time, and the photostimulation apparatus 100 includes either the configuration (1) or the configuration (2). Is also possible. Even if it is the structure provided with either one, the effect of noise reduction can be acquired.
[0033]
As another aspect, the configuration of the photostimulation device 100 is configured to emit visible light that does not include the wavelength used by the biological light measurement device 200 as stimulation light, and the photodiode 22 of the biological light measurement device 200 It is possible to adopt a configuration in which a visible light cut filter is inserted in front. In this case, since the stimulus light of visible light is cut by the visible light cut filter, it is not detected by the photodiode 22, and the generation of noise due to the stimulus light can be prevented. The visible light cut filter can be inserted, for example, between the detection optical fiber 21 and the photodiode 22 or in the middle of the detection optical fiber 21. It is also possible to attach a visible light cut filter so as to cover the incident end face of the detection optical fiber 21.
[0034]
In the embodiment described above, the case where measurement is performed by connecting the photostimulation device 100 and the biological light measurement device 200 has been described. However, the photostimulation device 100 and the biological light measurement device 200 are not necessarily connected. In both cases, the noise reduction effect of the biological light measurement apparatus 200 can be obtained. For example, the photostimulation device is used in another measuring device such as an electroencephalograph, and even if it is not connected to the living body light measuring device, as long as the photostimulating device and the living body light measuring device are used in the vicinity. Conventionally, there is a risk of noise. Even in this case, the noise of the biological optical measurement device 200 can be reduced by using the photostimulation device 100 of the present embodiment.
[0035]
【The invention's effect】
As described above, according to the present invention, it is possible to reduce the occurrence of noise in the output of the biological light measurement device even when the photostimulation device is used near the biological light measurement device. .
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a photostimulation apparatus according to an embodiment of the present invention.
FIG. 2 is a graph showing an emission spectrum of a white light emitting diode used in a light emitting unit in the photostimulation apparatus according to the embodiment of the present invention.
FIG. 3 is a graph showing a waveform of stimulation light emitted from the photostimulation apparatus according to the embodiment of the present invention.
FIG. 4 is a block diagram showing a schematic configuration of a biological light measurement device to which the photostimulation device according to the embodiment of the present invention is connected.
FIG. 5 is an explanatory diagram illustrating a state in which measurement is performed with the biological light measurement device while applying light stimulation with the light stimulation device according to the embodiment of the present invention.
FIG. 6A is an output waveform of a biological light measurement device to which a conventional photostimulation device is connected, and FIG. 6B is a diagram using the photostimulation device according to the embodiment of the present invention, with a duty equal to that of the conventional device. (C) is an output waveform of the living body light measuring device when the high frequency component is reduced by setting the duty widely and using the photostimulation device according to the embodiment of the present invention. It is an output waveform.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 9 ... Test object, 10 ... Light source part, 11 ... Semiconductor laser, 12 ... Optical module, 13 ... Optical fiber for irradiation, 20 ... Optical measuring part, 21 ... Optical fiber for detection, 22 ... Photodiode, 23 ... Lock-in amplifier Module, 24 ... A / D converter, 30 ... Signal processing unit, 31 ... Control unit, 32 ... Storage unit, 33 ... Input / output unit, 34 ... Display unit, 40 ... Mounting unit, 100 ... Photostimulator, 101 ... Reference numeral 102: Light source driver 103: Light emitting unit 104: Power source 105: Frequency setting switch 106: Light amount setting switch 107 Duty setting switch 110: Control unit 200: Biological light measurement device

Claims (4)

In a photostimulation device that emits stimulation light for photostimulating a subject,
An optical stimulation apparatus comprising: means for reducing, from the stimulation light, light having the same frequency component and / or light having the same wavelength component as measurement light used by the biological optical measurement apparatus. A light emitting unit that emits stimulation light for optically stimulating a subject, and a control unit that controls the operation of the light emitting unit and emits periodic pulsed light as the stimulation light,
The control unit includes a duty setting unit that receives a setting of a ratio of a light emission time with respect to a cycle of the pulsed light, a cycle setting unit that receives a setting of a cycle of the pulsed light, and a setting of a light amount per pulse of the pulsed light. A light amount setting unit to be received, and a calculation unit for calculating the light intensity that satisfies the duty, the cycle, and the light amount received by the duty setting unit, the cycle setting unit, and the light amount setting unit, respectively, A light stimulating device characterized in that the light emitting unit emits light with light intensity.   3. The photostimulation apparatus according to claim 2, further comprising a connection unit that is connected to the biological light measurement device and receives an instruction signal, wherein the light emission unit is irradiated with the biological light measurement device connected to the connection unit. A light stimulator that emits light containing no wavelength component used as the stimulating light. In order to stimulate the subject connected to the living body light measuring device and the living body light measuring device that measures the internal information of the living body by irradiating the subject with measuring light and detecting the passing light from the subject A biological light measurement system having a light stimulation device that emits the stimulation light of
The photostimulation device has a light emitting unit that emits the stimulation light, and a control unit that controls the operation of the light emitting unit based on an instruction signal from the biological light measurement device,
The biological light measurement system, wherein the light emitting unit emits light that does not include a wavelength component of the measurement light of the biological light measurement device as the stimulation light.

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