JP6939044B2 - Eyeball light measuring device and light measuring device - Google Patents

Description

The present invention relates to an eyeball light measuring device and a light measuring device.

Patent Document 1 describes a light source unit that emits measurement light having at least one wavelength for measuring a biological component contained inside the living body, and a detection unit that detects the measurement light emitted from the inside of the living body. And a measurement unit provided in at least one of the light source unit and the living body or between the living body and the detection unit and having a polarization control unit for controlling the polarization direction of the measurement light. An analysis unit that calculates the degree of luminosity based on the change in the polarization state of the measurement light using the measurement result by the measurement unit and analyzes the concentration of the biological component based on the calculated degree of luminosity. , The measuring device is described.

Japanese Unexamined Patent Publication No. 2013-126509

By the way, in light measurement performed by transmitting light to a measurement target, the change in the intensity of transmitted light due to the shaking of the measurement target, which occurs with the passage of time, and the fluctuation of ambient light and the shaking of the measurement target are combined. It was difficult to obtain accurate measured values due to the resulting changes in ambient light.
An object of the present invention is to provide an eyeball optical measuring device or the like in which measurement accuracy in optical measurement is improved as compared with the case where correction by a signal is not performed during a non-emission period.

According to the first aspect of the present invention, there is a fluctuation in the measurement environment in which the period of the light emitting portion that emits light toward the eyeball of the person to be measured and the period of emitting light and the period of not emitting light are mixed in the measurement environment. A control unit that controls the light emitting unit so as to be shorter than the period of And a correction unit that corrects the first signal by using the second signal input from the light receiving unit , and the correction unit is the first from the light receiving unit during the emission period. A plurality of the signals of It is an eyeball light measuring device characterized in that correction is made according to the second signal of the unit.
According to the second aspect of the present invention, the period of fluctuation in which the period of the light emitting unit that emits light toward the object to be measured and the period of emitting light and the period of not emitting light are mixed in the measurement environment. A control unit that controls the light emitting unit so as to be shorter, and a light receiving unit that receives light from the object to be measured and outputs a first signal during the emission period and outputs a second signal during the non-emission period. And a correction unit that corrects the first signal by the second signal input from the light receiving unit , and the correction unit is provided with the first signal from the light receiving unit during the emission period. Is input, a plurality of the second signals are input during the non-emission period, and a plurality of the first signals are input to a part of the two non-emission periods sandwiching the emission period, which are close to the emission period. It is an optical measuring device characterized by correcting according to the second signal.
The invention according to claim 3, wherein, according to claim 2, characterized in that said emission period and the non-emitting period to control the light emitting unit to repeat a predetermined number of times It is an optical measuring device.
In the invention according to claim 4 , the control unit does not emit light longer than the measurement period in which the emission period and the non-emission period are repeated a predetermined number of times, and the measurement period. The optical measuring device according to claim 2 , further comprising a detection period for detecting the above, and controlling the light emitting unit so that the measurement period and the detection period are repeated a plurality of times.
In the invention according to claim 5 , the light emitting unit includes a light source that emits light having a plurality of wavelengths, and the control unit has a predetermined emission period of the plurality of wavelengths. The optical measuring device according to claim 4 , wherein the light emitting unit is controlled so as to include an emission period for emitting light of at least two wavelengths.

According to the inventions of claims 1 and 2, the measurement accuracy in the optical measurement is improved as compared with the case where the correction by the signal is not performed during the non-emission period.
According to the invention of claim 3 , the occurrence of an error in the optical measurement is suppressed as compared with the case where the emission period and the non-emission period are not repeated.
According to the invention of claim 4 , the measurement period can be easily identified as compared with the case where the detection period is not provided.
According to the invention of claim 5 , the measurement accuracy in optical measurement is further improved as compared with the case where a plurality of wavelengths are not used.

It is a figure which shows an example of the structure of the optical measuring apparatus of the eyeball to which the 1st Embodiment is applied. It is a figure explaining the signal conversion circuit in the light receiving part of an optical system. It is a figure explaining the disturbance light in the light measurement of an eyeball. It is a figure explaining the control method of the light source of the light emitting part in 1st Embodiment. (A) is a diagram showing an example of measured values, and (b) is an enlarged view of a part of (a). It is a figure which conceptually shows the method of correcting a measured value. (A) is the intensity of the emitted light (emitted light intensity) emitted from the light source of the light emitting portion toward the anterior chamber of the eyeball, and (b) is the measured value output from the light receiving portion to the correction unit. c) is a diagram showing a correction value corrected by the correction unit and output to the calculation unit. It is a figure explaining the correction method to which the first embodiment is applied. It is a figure explaining the correction method to which the second embodiment is applied. (A) is an enlarged view of the measured value, (b) is an enlarged view of the measured value, and (c) is an enlarged view of the correction value with respect to (b). It is a figure explaining the correction method to which the third embodiment is applied. (A) is an enlarged view of the measured value, (b) is an enlarged view of the measured value, and (c) is an enlarged view of the correction value with respect to (b). It is a figure explaining the correction method to which the 4th Embodiment is applied. (A) is an enlarged view of the measured value, (b) is an enlarged view of the measured value, and (c) is an enlarged view of the correction value with respect to (b).

Hereinafter, embodiments of the invention will be described with reference to the accompanying drawings. Here, the optical measuring device will be described by taking as an example an optical measuring device of the eyeball that measures (measures) the concentration of a substance such as glucose contained in the aqueous humor of the anterior chamber of the eyeball. However, the optical measuring device described here can be applied to other optical measurements.
In the attached drawing, in order to clarify the relationship between the eyeball and the optical path, the eyeball may be described larger than other members (such as an optical system described later).

(Background for measuring glucose concentration in the anterior chamber water)
First, the background for measuring the glucose concentration in the aqueous humor will be described.
Self-blood glucose measurement is recommended for type 1 diabetic patients and type 2 diabetic patients (measured subjects) who require insulin treatment. In self-blood glucose measurement, in order to precisely control blood glucose, the person to be measured measures his / her own blood glucose level at home or the like.
Currently available self-glucose meters measure the glucose concentration in blood by puncturing a fingertip or the like with an injection needle and collecting a small amount of blood. Self-blood glucose measurement is often recommended after each meal or before bedtime, and is required to be performed once to several times a day. Intensified insulin therapy, in particular, requires a larger number of measurements.
For this reason, the invasive blood glucose level measurement method using a puncture type self-blood glucose meter tends to cause a decrease in incentive for the self-blood glucose measurement of the person to be measured due to the pain caused by the pain when collecting blood (at the time of blood collection). .. For this reason, efficient diabetes treatment may be difficult.

Therefore, a non-invasive blood glucose measurement method that does not require puncture is being developed in place of the invasive blood glucose measurement method such as puncture.
As a non-invasive blood glucose level measurement method, near-infrared spectroscopy, photoacoustic spectroscopy, and a method using optical rotation are being studied. In these methods, the blood glucose level is estimated from the glucose concentration.
Near-infrared spectroscopy and photoacoustic spectroscopy detect light absorption spectra and acoustic vibrations in blood in the blood vessels of fingers. However, cellular substances such as red blood cells and white blood cells are present in blood. Therefore, it is greatly affected by light scattering. In addition to blood in blood vessels, it is also affected by surrounding tissues. Therefore, these methods require detecting a signal related to glucose concentration from a signal involving a huge number of substances such as proteins and amino acids, and it is difficult to separate the signals.

On the other hand, the aqueous humor in the anterior chamber has almost the same components as serum and contains protein, glucose, ascorbic acid and the like. However, unlike blood, aqueous humor does not contain cellular substances such as red blood cells and leukocytes, and is less affected by light scattering. That is, aqueous humor is suitable for optical measurement of glucose concentration.

Therefore, the concentration of a substance such as glucose can be optically measured from this aqueous humor.
Since aqueous humor is a tissue fluid for transporting glucose, it is considered that the glucose concentration in aqueous humor correlates with the glucose concentration in blood. Then, in the measurement using rabbits, it is reported that the time required for glucose transport from blood to aqueous humor (transport delay time) is within 10 minutes.
As described above, when the glucose concentration in the aqueous humor is measured, the glucose concentration in the blood can be obtained.

Here, as an example, an optical path in which light is incident at an angle close to parallel to the eyeball and the light transmitted (passed) across the anterior chamber is received, and a substance such as glucose contained in the aqueous humor is used. Suppose that the concentration is measured optically.

[First Embodiment]
FIG. 1 is a diagram showing an example of a configuration of an eyeball light measuring device 1 to which the first embodiment is applied. FIG. 1 also shows the eyeball 10 (cross-sectional view in the vertical direction) seen from above. The eyeball 10 is the left eye. Then, the inside and outside directions indicating the inside (nose side) and the outside (ear side) of the face, the front-back direction indicating the front side and the back side of the face, and the up-down direction indicating the upper side and the lower side of the face are indicated by arrows and the like. There is.

The optical measurement device 1 of the eyeball (hereinafter, referred to as an optical measurement device 1) includes an optical system 20, a correction unit 40, a calculation unit 50, a display unit 60, and a control unit 70.
The optical system 20 transmits light so as to cross the anterior chamber 13 and the light emitting portion 20A that emits (irradiates) light toward the anterior chamber 13 in the eyeball (object to be measured) 10 of the subject (subject). It includes a light receiving unit 20B that receives light.

The correction unit 40 receives a signal (measured value x) from the light receiving unit 20B of the optical system 20 and outputs a signal (correction value y) corrected by a predetermined method.
The calculation unit 50 inputs the signal (correction value y) corrected by the correction unit 40, and calculates the concentration of the substance contained in the aqueous humor.
The display unit 60 displays the line-of-sight target 61, which serves as a mark for guiding the line-of-sight of the person to be measured in a predetermined direction, and the concentration of the substance contained in the aqueous humor calculated by the calculation unit 50.
The control unit 70 controls the optical system 20, the correction unit 40, the calculation unit 50, and the display unit 60.

As an example, the light measuring device 1 measures the concentration of a substance contained in the aqueous humor from a change in the polarization state of the transmitted light transmitted through the anterior chamber 13 (aqueous humor). Glucose and the like are optically active substances. Therefore, when polarized light is transmitted through the aqueous humor, the direction of vibration of the polarized light rotates according to the concentration due to the optical rotation of the optically active substance, and the linearly polarized light changes to elliptically polarized light due to the optical anisotropy of the optically active substance. The polarization state changes, such as. By obtaining these changes in the polarization state from the signal (correction value y) from the correction unit 40, the concentration of the substance contained in the aqueous humor is calculated.
A known method may be used for calculating the concentration of the substance contained in the aqueous humor. Therefore, the description thereof will be omitted.

First, the structure of the eyeball 10 will be described.
As shown in FIG. 1, the eyeball 10 is substantially a sphere, with a glass body 11 in the center. In FIG. 1, the description of the rear half of the eyeball 10 is omitted. The crystalline lens 12, which acts as a lens, is embedded in a part of the glass body 11. The anterior chamber 13 is on the anterior side of the crystalline lens 12, and the cornea 14 is on the anterior side of the anterior chamber 13 so as to cover the anterior chamber 13. The anterior chamber 13 and the cornea 14 project convexly from the sphere.
The peripheral portion of the crystalline lens 12 is surrounded by the iris 17, and the center thereof is the pupil 15. Except for the portion in contact with the crystalline lens 12, the glass body 11 is covered with the retina 16. The retina 16 is covered with the sclera 18. That is, the outer side of the eyeball 10 is covered with the cornea 14 and the sclera 18.

The anterior chamber 13 is a region surrounded by the cornea 14 and the crystalline lens 12. The anterior chamber 13 has a circular shape when viewed from the front. The anterior chamber 13 is filled with aqueous humor.

Next, the optical system 20 will be described.
The light emitting unit 20A includes a light source 21. The light source 21 emits light toward the anterior chamber 13 of the eyeball 10.
The light source 21 is a laser and emits beam-shaped light having a narrow wavelength width. The light source 21 is configured to include a plurality of lasers that emit light having wavelengths different from each other. The light source 21 may be a light source having a wide wavelength width such as a light emitting diode (LED) or a lamp.
In addition to the light source 21, the light emitting unit 20A includes optical components such as a polarizer that sets the light emitted by the light source 21 to a predetermined polarization state. Here, these descriptions are omitted.

The light receiving unit 20B includes a light receiving element 22. The light receiving element 22 receives the light transmitted so as to cross the anterior chamber 13. The light receiving element 22 is, for example, a silicon photodiode, and the flowing current changes according to the intensity of the received transmitted light 32. Here, the light intensity means the radiant energy per unit time.
In addition to the light receiving element 22, the light receiving unit 20B uses optics such as an analyzer and a magneto-optical element that detects rotation in the vibration direction in order to detect the polarization state of the light transmitted through the anterior segment 13 of the eyeball 10. It is configured to include a component and a signal conversion circuit (see FIG. 2 to be described later) that converts the current flowing through the light receiving element 22 into a digital signal (measured value x). Here, these descriptions are omitted.

As shown in FIG. 1, the light source 21 of the light emitting unit 20A emits the emitted light 31 toward the anterior chamber 13 of the eyeball 10. The emitted light 31 enters the anterior chamber 13 from a part of the surface of the cornea 14 on the light source 21 side and travels across the anterior chamber 13. Then, the transmitted light 32 is emitted from a part of the surface of the cornea 14 on the light receiving portion 20B side. The transmitted light 32 is incident on the light receiving element 22 of the light receiving unit 20B. That is, the emitted light 31 emitted by the light source 21 is a beam-shaped light (light beam) having a diameter smaller than that of the anterior chamber 13 that passes through a part of the anterior chamber 13 of the eyeball 10.

The correction unit 40 is configured as a computer equipped with a CPU (central processing unit), RAM (random access memory), ROM (read-only memory), HDD (hard disk drive), I / O port (input / output port), and the like. , Works by software. The correction unit 40 may be composed of hardware such as an analog electronic circuit.
As will be described later, the correction unit 40 receives a digital signal (measured value x) in which the current value flowing through the light receiving element 22 is converted from the light receiving unit 20B in the optical system 20, and is corrected by a predetermined method. The signal (correction value y) is output.

Like the correction unit 40, the calculation unit 50 is configured as a computer including a CPU, RAM, ROM, HDD, I / O port (input / output port), and is operated by software. The calculation unit 50 may be composed of hardware such as an analog electronic circuit.
The calculation unit 50 receives the corrected signal (correction value y) from the correction unit 40 and calculates the concentration of the substance contained in the aqueous humor.

The display unit 60 is an electronic display such as a liquid crystal display that can electronically display an image. In this case, the line-of-sight target 61 is a point, a cross, or the like displayed on the electronic display. These may be bright and the surroundings may be dark, and they may be dark and the surroundings may be bright.
The display unit 60 does not have to be an electronic display. In this case, the line-of-sight target 61 may be any one that guides the direction (line of sight) of the eyeball 10 by the person to be measured visually. For example, it may be a member having an LED lamp, a marker (mark), a scale, and the like.

Like the correction unit 40 and the calculation unit 50, the control unit 70 is configured as a computer equipped with a CPU, RAM, ROM, HDD, I / O port (input / output port), etc., and is operated by software. May be good. Further, the control unit 70 may be configured by hardware such as an analog electronic circuit. Then, the control unit 70 controls the optical system 20, the correction unit 40, the calculation unit 50, and the display unit 60.
The correction unit 40, the calculation unit 50, and the control unit 70 may be configured as one computer in all or two of them.

FIG. 2 is a diagram illustrating a signal conversion circuit in the light receiving unit 20B of the optical system 20.
Here, the process of signal conversion in the light receiving element 22 and later is shown.
The signal conversion circuit in the light receiving unit 20B includes a current-voltage conversion circuit 23 that is connected to the light receiving element 22 and converts the current value of the light receiving element 22 into an analog voltage value (analog voltage value), and the analog voltage value into a digital value. An analog-to-digital converter (ADC: Analog Digital Converter) 24 for conversion is provided.

The current-voltage conversion circuit 23 is, for example, a resistor. When a current flows through the resistor, an analog voltage (analog voltage value) is generated between both terminals of the resistor.
The analog-to-digital conversion circuit 24 converts the analog voltage value output by the current-voltage conversion circuit 23 into a digital signal having a predetermined number of bits. The number of bits may be set according to a predetermined required resolution for the analog voltage value.

Here, in the silicon photodiode or the like used as the light receiving element 22, a minute current (dark current) constantly flows even in a state where light is not received. Therefore, the current flowing through the light receiving element 22 when the transmitted light 32 is received is a combination of the current to be measured and the dark current flowing by receiving the transmitted light 32. That is, the current due to the transmitted light 32 to be measured is raised (biased) by the dark current and flows through the light receiving element 22.

However, in a silicon photodiode or the like used as the light receiving element 22, the dark current increases as the temperature rises. That is, if the temperature of the environment in which the light receiving element 22 is placed changes, the dark current changes. Further, the temperature of the light receiving element 22 may also rise due to the incident light of the transmitted light 32. Therefore, by continuing the measurement, the temperature of the light receiving element 22 may rise with time, and the dark current of the light receiving element 22 may increase with time.
That is, the dark current of the light receiving element 22 may fluctuate with time.

FIG. 3 is a diagram illustrating disturbance light in the light measurement of the eyeball 10.
In addition to the transmitted light 32 transmitted through the anterior chamber 13 of the eyeball 10, ambient light is incident on the light receiving element 22 of the light receiving unit 20B in the optical system 20. An example of ambient light will be described below.
The light measurement environment (measurement environment) of the eyeball 10 includes external light 80 such as illumination light that illuminates a place (room) where the light measurement device 1 is installed and natural light that leaks from a window of the room. Further, on the front side of the eyeball 10, a display unit 60 for displaying the line-of-sight target 61 is provided.

A part of the illumination light and the natural light in the measurement environment becomes the light α directly incident on the light receiving element 22. Further, a part of the illumination light or the natural light in the light measurement environment becomes the light β toward the surface of the eyeball 10 (the surface of the cornea 14 (see FIG. 1)). Then, the external light 80 fluctuates (fluctuates) with time. In the case of illumination light, the intensity fluctuates periodically under the influence of the power frequency at which the illumination light is turned on. Moreover, in the case of natural light, the intensity fluctuates with time due to the influence of clouds and the like.

Further, the display unit 60 displays the line-of-sight target 61. As described above, the line-of-sight target 61 guides the line of sight of the person to be measured. Therefore, it is required that the line-of-sight target 61 is bright and the surroundings are dark, or the line-of-sight target 61 is dark and the surroundings are bright. Therefore, a part of the light from the bright portion of the display unit 60 becomes the light γ that is directly incident on the light receiving element 22. Further, a part of the light from the bright portion of the display unit 60 becomes the light δ directed to the surface of the eyeball 10 (the surface of the cornea 14).
Then, a part of the light β and the light δ is reflected on the surface of the eyeball 10 (the surface of the cornea 14) and becomes the light ε that is superimposed on the transmitted light 32 and incident on the light receiving element 22.
The light from the bright portion of the display unit 60 is also affected by the scanning forming the display of the display unit 60, and the intensity of the light fluctuates periodically.

In addition to the transmitted light 32, light α, light γ, light ε, and the like are incident on the light receiving element 22 as ambient light. That is, similarly to the dark current described above, the current due to the transmitted light 32 to be measured is raised (biased) by the current due to the ambient light and flows through the light receiving element 22.

Further, if the line of sight shifts, the position of the eyeball 10 changes. Further, even when the eyeball 10 is focused on one point (for example, the line-of-sight target 61 of the display unit 60), the eyeball 10 is finely moved due to fixed vision fine movement or the like. The position of the eyeball 10 also changes due to blinking. That is, when a living body such as the eyeball 10 is used as the object to be measured, it can be said that the object to be measured is swaying periodically.
When the object to be measured shakes, the ambient light (light ε) also shakes. That is, the ambient light incident on the light receiving element 22 fluctuates periodically.
That is, it is inevitable that the current flowing through the light receiving element 22 due to the ambient light constantly fluctuates.

As described above, when optical measurement is performed using a living body as an object to be measured, it is inevitable that the object to be measured sways (sways) periodically.
When the object to be measured fluctuates periodically, the fluctuation of the external light 80 such as illumination light and natural light over time and the periodic fluctuation of the object to be measured are combined to increase the intensity of the ambient light incident on the light receiving element 22. It fluctuates over time and periodically.
The light receiving element 22 has a change in dark current with time due to temperature.
In this way, the current due to the transmitted light 32 to be measured is raised (biased) and flows through the light receiving element 22 by the dark current that changes with time and the current that fluctuates with time and periodically due to the ambient light.

Here, the dark current and the current due to the disturbance light, which raise the current due to the transmitted light 32 to be measured, are referred to as a bias current.
The temporal and periodic fluctuations in the intensity of the ambient light incident on the light receiving element 22 and the temporal changes in the dark current generated in the light receiving element 22 are referred to as fluctuations mixed in the measurement environment.
Then, one cycle in the periodic fluctuation of the fluctuation is set as the cycle.
The period of fluctuation generated by a living body such as the eyeball 10 is around 10 Hz. On the other hand, the change over time of the dark current due to the temperature in the light receiving element 22 is longer than 10 Hz. The change with time of the dark current due to the temperature in the light receiving element 22 may be regarded as a periodic change.

As described above, in order to obtain the current value due to the transmitted light 32, it is necessary to subtract the bias current value (bias current value) from the current value flowing through the light receiving element 22 as an offset value.
When light measurement is performed using a living body as an object to be measured, the current corresponding to the intensity of the transmitted light 32 also fluctuates with time because the object to be measured fluctuates with time. The change with time of the current corresponding to the intensity of the transmitted light 32 due to the fluctuation of the object to be measured with time can be dealt with by obtaining the average value by a plurality of measurements as described later.
Hereinafter, a method of suppressing the influence of a dark current that fluctuates with time and a current (bias current) due to disturbance light, which is superimposed on the current flowing corresponding to the intensity of the transmitted light 32, will be described.

By suppressing the fluctuation of the temperature of the light receiving element 22, the dark current value flowing through the light receiving element 22 can be reduced or the fluctuation can be suppressed.
Further, the light α and the light β due to the illumination light and the natural light can be reduced by shading. Further, when the display unit 60 for displaying the line-of-sight target 61 is not used, or when the display of the line-of-sight target 61 on the display unit 60 is stopped during light measurement, the light γ from the display unit 60 or the light γ from the display unit 60 is emitted. The light ε in which a part of the light δ is reflected on the surface of the eyeball 10 (the surface of the cornea 14) can be reduced.

FIG. 4 is a diagram illustrating a method of controlling the light source 21 of the light emitting unit 20A according to the first embodiment. FIG. 4A is a diagram showing an example of the measured value x, and FIG. 4B is an enlarged view of a part of FIG. 4A. The horizontal axis is the time t, and the vertical axis is the measured value x which is a digital signal from the analog-to-digital conversion circuit 24 in FIG.

The light source 21 emits light having a plurality of different wavelengths in a pulsed manner in order. A series of light emission of a plurality of different wavelengths is set as a set and repeated a plurality of times.
Here, as shown in FIG. 4 (b), five wavelengths λ1 to λ5 (indicated as wavelength λ when not distinguished) are used as different wavelengths, and the set # 1 to shown in FIG. 4 (a) is used. Repeat 17 times like # 17. In this way, by repeating the set multiple times, in multiple measurements, the average value is obtained for each wavelength λ, and abnormal values such as excluding the maximum value and the minimum value are excluded. The occurrence of errors due to the fluctuation of the object to be measured over time is suppressed.
Although different wavelengths λ are set, the set may be formed by repeating one wavelength λ a plurality of times. Further, the wavelength λ may be different for each set.
Further, since the change in the polarization state of the transmitted light 32 transmitted through the anterior chamber 13 (aqueous humor) may have wavelength dependence, it is included in the aqueous humor by using a plurality of different wavelengths. The measurement accuracy for the concentration of the substance is improved.

Then, as shown in FIG. 4B, the light source 21 emits light of each wavelength λ in the emitted light 31 emitted toward the anterior chamber 13 of the eyeball 10, and is defined as the emission period P. The emission period P is the time t _P. The non-emission period S is defined as the period between two consecutive emission periods P. The non-emission period S is the time t _S.
Then, between the set and the set, a detection period W set longer than any of the emission period P and the non-emission period S is set. The detection period W is the time t _W (t _W > t _P , t _S ).
The sum of the plurality of emission periods P and the plurality of non-emission periods S in each set is defined as the measurement period M.

The detection period W is provided to detect the beginning of the emission period P of each set, here, the emission period P of the wavelength λ1. The correction unit 40 distinguishes between the non-emission period S and the detection period W by measuring the time, and identifies that the wavelength λ1 is immediately after the detection period W is detected.
The correction unit 40 may receive a control signal from the control unit 70 that controls the light source 21 in the optical system 20 to identify the wavelength λ emitted from the light source 21. In this case, the detection period W does not have to be set.

During the emission period P, the emitted light 31 having a wavelength λ of any of the wavelengths λ1 to λ5 is emitted from the light source 21 of the light emitting unit 20A in the optical system 20 toward the anterior chamber 13 of the eyeball 10. _{Then, in this emission period P, the light receiving unit 20B measures a measured value x λ} (described later) with respect to a current in which a bias current due to dark current, ambient light, or the like is added to the current flowing by the transmitted light 32 transmitted through the anterior chamber 13 of the eyeball 10. _{The measured values x λ1} and x _λ2 in FIG. 5B) are output a plurality of times.
Further, in the non-emission period S in which the emitted light 31 is not emitted from the light source 21 toward the anterior chamber 13 of the eyeball 10, the light receiving unit 20B does not include the current flowing by the transmitted light 32, and biases such as dark current and ambient light. measured values for current _{x B} (see measured value _{x B} shown in FIG. 5 (b) to be described later) to output a plurality of times.
The fluctuation of the measured value x _λ within the emission period P is due to the fact that the eyeball 10 as the object to be measured fluctuates over time.

Time _{t S} of the time _{t P} and the non-emission period S of the extraction phase P, for example each 0.8ms, the time _{t W} detection period W is, for example, 2.4 ms. At the time t _{P of the emission period P and the time t S} of the non-emission period S, the light receiving unit 20B in the optical system 20 makes a plurality of measurements. That is, a plurality of measured values x _{λ are taken out at the time t P} of the emission period P, and a plurality of measured values x _B are taken out at _{the time t S} of the non-emission period S. Therefore, although it depends on the operating speed of the light receiving unit 20B, the time t _{P of the emission period P and the time t S} of the non-emission period S are preferably set from 0.1 ms to 10 ms.
The cycle between the emission period P and the non-emission period S ( _{the time obtained by adding the time t P of the emission period P and the time t S} of the non-emission period S) is the cycle of fluctuations (bias current fluctuations) mixed in the measurement environment. Set to a shorter period. Further, the period between the emission period P and the non-emission period S is set to be shorter than 1/2 of the period of the fluctuation (bias current fluctuation) mixed in the measurement environment, so that the fluctuation (bias) mixed in the measurement environment is set. The influence of current fluctuation) is further suppressed.
As described above, the period of fluctuation (bias current fluctuation) mixed in the measurement environment is around 10 Hz. In contrast, the time _{t S} of the time _{t P} and the non-emission period S of the illustrated extraction phase P is 1/100 back and forth.

FIG. 5 is a diagram conceptually showing a method of correcting the measured value x. FIG. 5A shows the intensity of the emitted light 31 emitted from the light source 21 of the light emitting unit 20A toward the anterior chamber 13 of the eyeball 10 (outgoing light intensity L), and FIG. 5B shows the light receiving unit 20B. The measured value x output to the correction unit 40 and FIG. 5C is a diagram showing the correction value y corrected by the correction unit 40 and output to the calculation unit 50. Here, the horizontal axis is time t. In FIGS. 5A, 5B, and 5C, the number of wavelengths λ is set to 2 (wavelengths λ1 and λ2) for the sake of simplicity.

As shown in FIG. 5 (a), the outgoing light 31 emitted toward the anterior chamber 13 of the eye 10 from the light source 21 is out of the output light intensity L ₁ and the wavelength λ2 of the wavelength λ1 in each emission period P The emission intensity L _{2 is} the same (L ₁ = L ₂ ).

As shown in FIG. 5 (b), the measured value x _B (t) due to the bias current in the non-emission period S increases (increases) with time t. _{That is, the measured value x B} (t) due to the bias current in the non-emission period S _{becomes an offset value x O} (t) when extended to the emission period P. Here, the offset value x _O (t) also increases (increases) with time t. _{Therefore, the measured value x λ1} (t) actually measured with respect to the emitted light 31 having the wavelength λ1 in the emission period P also increases (increases) with time t. _{Similarly, the measured value x λ2} (t) actually measured with respect to the transmitted light 32 having the wavelength λ2 also increases (increases) with time t.

_{From the measured value x B} (t) in the non-emission period S, the _{offset value x O} (t) due to the bias current in the emission period P can be obtained by using the correction method described later. _{Here, the measured value x B} (t) in the non-emission period S is used, _{and the offset value x O} (t) is the amount raised by the bias current in the emission period P obtained from the _{measured value x B (t).} In FIG. 5B, the offset value x _{O (λ1)} (t) is set with respect to the wavelength _{λ1 and the offset value x O (λ2)} (t) is shown with respect to the wavelength λ2.
Here, the measured values x _λ1 (t) and x _λ2 (t) in the emission period P are examples of the first signal, and the measured values x _B (t) in the non-emission period S are the second signals. This is an example. _{The measured values x λ1} (n) and x _λ2 (n) in the emission period P, which will be described later, are also examples of the first signal, and the measured values x _B (n) in the non-emission period S are also the second signals. This is an example.

Therefore, as shown in FIG. 5 (c), the correction unit 40 increases the _{offset value x O (λ1)} due to the bias current from the _{measured value x λ1 (t) for the emitted light 31 of the wavelength λ1 shown in FIG. 5 (b).} By subtracting (correcting) (t) at each time, the influence of the bias current (offset value x _{O (λ1)} (t)) is corrected so as to be removed. The corrected correction value y _λ1 (t) is a true value to be obtained with respect to the transmitted light 32 having the wavelength λ1. Similarly for the wavelength λ2, the corrected correction value y _λ2 (t) is obtained.
In FIG. 5C, the _{difference in magnitude between the corrected correction value y λ1} (t) and the correction value y _λ2 (t) is due to the interaction between the substance contained in the aqueous humor and light. This is to show that it differs depending on the wavelength λ.

As shown in FIG. 5B, the period between the emission period P (time t _P ) and the non-emission period S (time t _S ) is the period of fluctuations mixed in the measurement environment (offset value x _O due to bias current). It is set shorter than the fluctuation cycle). By doing so, it is possible to prevent the _{offset value x O} from fluctuating significantly in each emission period P. That is, in each non-emission period S, the measured value x _B due to the bias current may change monotonically. In each non-emission period S, _{even if the measured value x B} has an inflection point, it is preferable that there is at most one inflection point.
This facilitates correction by the correction unit 40, as will be described later.

_{In FIG. 5C, the correction value y λ1} in the light emission period P of the two wavelengths λ1 was set to be the same, but as shown in FIG. 4B, the eyeball 10 as the object to be measured It may fluctuate due to fluctuations over time.

(Correction method)
Then, by using the measured values x _B in the measurement value x _lambda and the non-emitting period S in the extraction phase P output from the light receiving unit 20B to the correction unit 40, a method for correcting the measured value x _lambda in the extraction phase P This will be described in detail.
FIG. 6 is a diagram illustrating a method of correction to which the first embodiment is applied. The horizontal axis is the measurement number n, and the vertical axis is the measurement value x output from the light receiving unit 20B to the correction unit 40. Here, the measurement number n is used instead of the time t. As described above, the measured value x is output a plurality of times in each emission period P and each non-emission period S. That is, since the measured value x is output for each measurement, the measurement number n corresponding to the measured value x is used. As the time t elapses, the measurement number n becomes larger. Therefore, the measurement number n and the time t are synonymous.
Then, the in the measurement number _{n (n a ≦ n <n} b), includes a plurality of measurement number n. The same applies to other cases such as the measurement number n (n _b ≤ n <n _c).

The case shown in FIG. 6 is a case where the change in the bias current with respect to the measurement number n (time t) is small. _{Therefore, the change of the measured value x B} with respect to the bias current with respect to the measurement number n is small. For example, in a temperature-controlled dark room, at least when the measurement is performed without displaying the line-of-sight target 61 on the display unit 60, there is no or extremely little ambient light from the external light 80 or the like, and the light receiving unit 20B This is a case where the temperature change of the light receiving element 22 is small or the change in dark current due to the temperature change is small.

In such a case, first, as shown in equation (1), the measurement number _{n (n a ≦ n <n} b, n c ≦ n <n d, n e ≦ n <n f, n g ≦ n The number (measured number) N of the measured values x in each non-emission period S of <n _h , _ni ≦ n <n _{j) is obtained.} Next, as shown in equation (2), the offset value _{x O,} measurement number _{n (n a ≦ n <n} b, n c ≦ n <n d, n e ≦ n <n f, n g ≦ n It is obtained by dividing the sum of the measured values x (measured value x _B , but expressed as measured value x) in each non-emission period S of <n _h , _ni ≤ n <n _{j) by the measured number N.} That is, the number of times to obtain the _{offset value x O is once.} That is, the offset value x _O does not depend on the measurement number n.
Then, the correction value y _.lambda.1 after correction for the wavelength .lambda.1, by Equation (3), the correction value y _.lambda.2 after correction with respect to the wavelength .lambda.2, determined by equation (4).

[Second Embodiment]
FIG. 7 is a diagram illustrating a method of correction to which the second embodiment is applied. 7 (a) is an enlarged view of the measured value x, FIG. 7 (b) is an enlarged view of the measured value x, and FIG. 7 (c) is an enlarged view of the correction value y with respect to FIG. 7 (b). The horizontal axis is the measurement number n. Since the other configurations are the same as those of the first embodiment, the description thereof will be omitted.
In the second embodiment, the offset value x _O (n) is obtained by a moving average.
For example, it is effective when the change in dark current due to the ambient light from the external light 80 or the like or the temperature change of the light receiving element 22 of the light receiving unit 20B is gentle and linear.
The offset value x _{O (n) is obtained from the measured value x B} (n) of the non-emission period S immediately before the emission period P. Further, it may be obtained by the non-emission period S immediately after the emission period P. The offset value x _O (n) is obtained for each measured value x.

As shown in FIG. 7 (b), when obtaining the moving average of the measured number _{n (n a ≦ n <n} b), when the measured number of the moving average of the object and _{n 0,} the measurement number n _{(n a} The number of measurements of ≦ n <n _b ) decreases _{by n 0-1.} The same is true for the rest.
Then, as shown in FIG. 7 (c), from the measured value x of less since measurement number _{n (n b ≦ n <n} c), the moving average value of the measurement number _{n (n a ≦ n <n} b) By subtracting the offset value x _O , the correction value y of the measurement number n (n _b ≤ n <n _{c) is obtained.} At this time, by adding the measurement number _{n (n a ≦ n <n} b) a _(n b -n _a), to correspond to the measurement number _{n (n b ≦ n <n} c).

That is, the equation (5), the moving average function SMA measurement number _{n (n a ≦ n <n} b), that is, the offset value _{x O.} The same applies to others.
Then, at the measurement number n (n _{b −} n ₀ ≦ n <n _{c −} n ₀ ), the correction value y _λ1 for the wavelength λ1 is obtained by the equation (6), and the measurement number n (n _f −n ₀ ≦ n <n) is obtained. _{At g} −n ₀ ), the correction value y _λ1 for the wavelength λ1 is obtained by the equation (7).
Similarly, in the measurement number _{n (n d -n 0 ≦ n} <n e -n 0), by Equation (8) the correction value y _.lambda.2 for the wavelength .lambda.2, measurement number _{n (n h -n 0 ≦ n} < in n _i -n _0), we obtain the correction value y _.lambda.2 for the wavelength .lambda.2 by the formula (9).

[Third Embodiment]
FIG. 8 is a diagram illustrating a method of correction to which the third embodiment is applied. 8 (a) is an enlarged view of the measured value x, FIG. 8 (b) is an enlarged view of the measured value x, and FIG. 8 (c) is an enlarged view of the correction value y with respect to FIG. 8 (b). The horizontal axis is the measurement number n. Since the other configurations are the same as those of the first embodiment, the description thereof will be omitted.
In the third embodiment, the offset value x _O (n) is obtained by the interpolation function INTERP.
_{This is effective when the change in the offset value x O} (n) due to the bias current with respect to the measurement number n is larger than in the case of the second embodiment.
The offset value x _O (n) is obtained by two non-emission periods S before and after the emission period P. The offset value x _O (n) is obtained for each measured value x.

Here, as shown in FIG. 8 (b), the extraction phase P (measurement number _{n (n b ≦ n <n} c)) two non-emitting period sandwiching the S (measurement number _{n (n a ≦ n <n} b It was determined from the measured value x in _{n c ≦ n <n d)} ), the interpolation function INTERP for extraction phase P and offset value _x O (n). That is, the offset value x _O (n) with respect to the measurement number n (n _b ≦ n <n _c ) is expressed by the equation (10).

Then, as shown in FIG. 8C and equation (11), the corrected correction value y _{λ1 of the measurement number n (n b} ≤ n <n _c ) is the interpolation function INTERP from the measurement value x (n). It is obtained by _{subtracting the offset value x O} (n) obtained in.
In the case of another measurement number n, another wavelength λ2 can be obtained in the same manner.
The interpolation function INTERP is not limited to linear interpolation, and other interpolation functions may be used.

The cycle of change of the offset value x _O , that is, the cycle of change of the measured value x in the non-emission period S may be longer than _{the time t P of the emission period P and the time t S of the non-emission period S.}

[Fourth Embodiment]
FIG. 9 is a diagram illustrating a method of correction to which the fourth embodiment is applied. 9 (a) is an enlarged view of the measured value x, FIG. 9 (b) is an enlarged view of the measured value x, and FIG. 9 (c) is an enlarged view of the correction value y with respect to FIG. 9 (b). The horizontal axis is the measurement number n. Since the other configurations are the same as those of the first embodiment, the description thereof will be omitted.
_{In the fourth embodiment, the average value of a part of the measured values x (measured values x B} ) in the non-emission period S close to the emission period P is set as the offset value x _O.
This is effective when the change in ambient light is random and difficult to estimate, or when the change in the offset value x _O with respect to the measurement number n (time t) is shorter than the measurement period M (see FIG. 4B). be.

As illustrated in FIG. 9A, the emission period P (measurement number n ( _nd ≤ n < _ne )) is defined as two non-emission periods S (measurement number n (n _c ≦)) sandwiching the emission period P. _{n <n d, n e ≦} n <n f)) were difficult supplemented by.
Therefore, as shown in FIG. 9 (b), the extraction phase P (measurement number _{n (n b ≦ n <n} c)) two non-emitting period sandwiching the S (measurement number _{n (n a ≦ n <n} b, In n _c ≤ n <n _d )), the average value of some measured values x close to the emission period P (measurement number n (n _b ≤ n <n _{c )) is defined as the offset value x O. Then, the value obtained by subtracting the offset value x O} from the measured value x of the emission period P (measurement number n (n _b ≤ n <n _c )) is defined as the corrected correction value y.
Therefore, as shown in FIG. 9C, _{the corrected correction value y at the measurement number n (n b} ≦ n <n _c ) inherits the fluctuation of the measurement value x with respect to the measurement number n as it is.
Here, the number of times to obtain the offset value x _O is once with respect to the emission period P (measurement number n (n _b ≤ n <n _c)). That is, the offset value x _O is obtained for each emission period P.

For example, suppose that the average value is obtained by using 1/2 of the number of measured values x in the two non-emission periods S. In this case, in the measurement number _{n (n a ≦ n <n} b), the correction value y _.lambda.1 with respect to the wavelength .lambda.1 a (n), determined by equation (12). Similarly, at the measurement number n (n _f ≦ n < _ng ), the correction value y _λ1 (n) for the wavelength λ1 is obtained by the equation (13).
Further, in the measurement number _{n (n d ≦ n <n} e), the correction value y _.lambda.2 for the wavelength .lambda.2 a (n), determined by equation (14). Similarly, in the measurement number _{n (n h ≦ n <n} i), the correction value y _.lambda.2 for the wavelength .lambda.2 a (n), determined by Equation (15).

In the above, the average value is obtained by using 1/2 of the measured numbers in the two non-emission periods S, but other measured numbers such as 1/3 may be used.

In the above, the light measuring device 1 has been described assuming that light is transmitted across the anterior chamber 13 of the eyeball 10 and the concentration of a substance contained in the anterior chamber 13 is measured. However, the light measuring device 1 may measure the cornea 14 by transmitting light so as to cross the cornea 14 of the eyeball 10.
Further, the light measuring device 1 can be applied to a flare device that measures the reflected light from the eyeball 10.
As described above, the optical measuring device 1 is preferably used when fluctuations are mixed in the measuring environment, such as when a living body is targeted for measurement.

Further, the present disclosure is not limited to the above-described embodiment, and can be implemented in various forms without departing from the gist of the present disclosure.

1 ... optical measuring device, 10 ... eyeball, 11 ... glass body, 12 ... crystalline lens, 13 ... anterior atriosphere, 14 ... cornea, 15 ... pupil, 16 ... retina, 17 ... iris, 18 ... strong membrane, 20 ... optical system , 20A ... light emitting unit, 20B ... light receiving unit, 21 ... light source, 22 ... light receiving element, 31 ... emitted light, 32 ... transmitted light, 40 ... correction unit, 50 ... calculation unit, 60 ... display unit, 61 ... line-of-sight target , 70 ... Control unit, 80 ... External light

Claims (5)

A light emitting part that emits light toward the eyeball of the person to be measured,
A control unit that controls the light emitting unit so that the period between the light emitting period and the non-light emitting period is shorter than the period of fluctuations mixed in the measurement environment.
A light receiving unit that receives light from the eyeball during the emission period and outputs a first signal, and outputs a second signal during the non-emission period.
The input from the light receiving unit, and a correction section that corrects the first signal using the second signal,
The correction unit
A plurality of the first signals are input from the light receiving unit during the emission period, and a plurality of the second signals are input during the non-emission period.
The plurality of the first signals are corrected according to a part of the second signals close to the emission period in the two non-emission periods sandwiching the emission period.
An eyeball light measuring device characterized by this. A light emitting part that emits light toward the object to be measured,
A control unit that controls the light emitting unit so that the period between the light emitting period and the non-light emitting period is shorter than the period of fluctuations mixed in the measurement environment.
A light receiving unit that receives light from the object to be measured during the emission period and outputs a first signal, and outputs a second signal during the non-emission period.
The input from the light receiving unit, and a correction section that corrects the first signal by said second signal,
The correction unit
A plurality of the first signals are input from the light receiving unit during the emission period, and a plurality of the second signals are input during the non-emission period.
The plurality of the first signals are corrected according to a part of the second signals close to the emission period in the two non-emission periods sandwiching the emission period.
An optical measuring device characterized by this. The control unit
The optical measuring device according to claim 2 , wherein the light emitting unit is controlled so that the emission period and the non-emission period are repeated a predetermined number of times. The control unit
The measurement period includes a measurement period in which the emission period and the non-emission period are repeated a predetermined number of times, and a detection period in which light is not emitted longer than the non-emission period and the measurement period is detected. The optical measuring device according to claim 2 , wherein the light emitting unit is controlled so that the detection period is repeated a plurality of times. The light emitting part is
Equipped with a light source that emits light of multiple wavelengths
The control unit
The light emitting unit is controlled so that the emission period repeated a predetermined number of times includes an emission period for emitting light of at least two wavelengths among the plurality of wavelengths. The optical measuring device according to claim 4.

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