JP5239545B2 - Glucose concentration measuring device, optical device, ring-shaped light beam forming device, and glucose concentration measuring method - Google Patents

Description

  The present invention relates to a glucose concentration measuring device, an optical device used in the glucose concentration measuring device, a ring-shaped light beam forming device used in the optical device, and a glucose concentration measuring method.

  The “glucose concentration in the blood” is an important index value for determining the necessity of medication particularly for diabetic diseases, although the average level varies depending on the individual. The glucose concentration has “characteristics that fluctuate greatly in a short period of time” due to diet, exercise, disease, etc., and urgent administration is often required due to a rapid increase in blood glucose concentration.

  Recently, the “glucose concentration of the anterior chamber that fills the anterior chamber between the cornea and the lens in the human eyeball” has an “very high correlation with blood glucose concentration” although there are individual differences. It has been known.

  Furthermore, based on the finding that “the glucose concentration in the anterior chamber medium and the refractive index of the anterior chamber medium have a very high correlation”, the refractive index of the anterior chamber medium is It has been proposed to non-invasively measure the glucose concentration of the intraocular medium (Patent Document 1).

  Patent Document 1 describes as “one embodiment of a fifth glucose concentration measuring device for carrying out the fifth glucose concentration measuring method” by using a confocal optical system “single light source of a specific wavelength” It is possible to measure the glucose concentration only by "."

JP 11-239567 A

As is well known, in the eyeball, “cornea, anterior chamber, lens, and vitreous body” are arranged in order from the outside to the inside, and the retina is present in the innermost part of the vitreous body.
When the refractive index of the anterior chamber material is obtained by the glucose concentration measurement method of Patent Document 1, the condensed light beam is sequentially condensed on the boundary surface between the cornea and the anterior chamber and the boundary surface between the anterior chamber and the crystalline lens. In addition, the optical thickness of the anterior chamber is detected, but the reflected light from surfaces other than the “boundary surface where the condensed light beam is focused” (such as the corneal surface or the boundary surface between the crystalline lens and the vitreous body) is measured. It is easy to act as noise.

  An object of the present invention is to effectively reduce or prevent measurement noise and improve measurement accuracy in glucose concentration measurement.

  The glucose concentration measuring apparatus according to the present invention is “calculated by detecting the optical thickness of the anterior chamber in the eyeball by an optical method and calculating the refractive index of the anterior chamber medium based on the detected optical thickness. A device that calculates and calculates the glucose concentration of the anterior chamber medium based on a correspondence relationship between a refractive index and a glucose concentration that is set in advance, and includes an optical device and a calculation means.

  The “anterior chamber medium” is a liquid medium that fills the interior of the anterior chamber and is also called “aqueous humor”.

An “optical device” is a device that optically detects the optical thickness of the anterior chamber of the eyeball.
“Calculation means” calculates the refractive index of the anterior chamber medium based on the optical thickness detected by the optical device, and calculates the glucose concentration of the anterior chamber medium corresponding to the calculated refractive index. Has the function of

  Specifically, the optical device includes an illumination light source, a collimating lens, a condensing lens, a photodetector, an optical path separation unit, a detection lens, a pinhole plate, a condensing position displacement unit, and a ring-shaped light beam forming unit.

The “illumination light source” is a laser light source that emits illumination light. Therefore, “laser light” is emitted from the illumination light source.
Various known laser light sources can be used as the illumination light source. However, the “semiconductor laser” is one suitable because of its small size and low cost. A surface emitting laser (VCSEL) is also suitable as another laser light source.
Since the illumination light source is a laser light source, the emitted laser light is in a substantially “linear polarization state”.

The “collimating lens” converts a laser beam emitted from the illumination light source into a parallel beam. The laser beam converted into a parallel beam in this way is referred to as an “illumination beam”.
Not all of the illumination light beam is used for illumination, but as described later, “at least the remainder from which the central portion of the light beam is removed” is used for illumination.

The “condensing lens” converts the illumination light beam converted into a parallel light beam by the collimating lens into a condensed light beam that is condensed toward the eyeball.
The “photodetector” receives the measurement light beam returned from the eyeball irradiated with the illumination light beam via the condenser lens and converts it into an electrical signal. The “measurement light beam” is light that is reflected by the cornea surface of the eyeball or an internal boundary surface and passes through the condenser lens in the reverse direction.

  As the photodetector, various types of light receiving elements that have been widely known can be used.

  The “optical path separating means” is means for “separating the measurement light beam from the light path of the illumination light beam to the photodetector side”, and a semi-transparent mirror and various beam splitters can be used as appropriate. Therefore, the optical path separating means is arranged on the optical path of the illumination light beam from the collimating lens to the condenser lens.

The “detection lens” is a lens that condenses the measurement light beam separated by the optical path separation unit toward the vicinity of the light receiving surface of the photodetector.
The “pinhole plate” is (fixed) disposed at a predetermined position near the light receiving surface of the photodetector.

  That is, the pinhole plate has a pinhole with a predetermined aperture at the “image point with respect to the object point” by the condensing lens and the detection lens when the “condensing position of the illumination light beam by the condensing lens” is an object point. Have

“Condensing position displacing means” is means for displacing the condensing position of the illumination light beam by the condensing lens in the optical axis direction of the condensing lens.
The “ring-shaped light beam forming means” is arranged on the optical path between the collimating lens and the condensing lens, and the cross-sectional shape of the illumination light beam converted into a parallel light beam by the collimating lens is shaped into a ring shape to form a ring-shaped illumination. It is a means to make a luminous flux.

  The “cross-sectional shape of the illumination light beam” is a cross-sectional shape of the light beam by an imaginary plane orthogonal to the propagation direction of the illumination light beam converted into a parallel light beam by the collimator lens (the optical axis direction of the collimator lens).

  The cross-sectional shape of the illumination light beam converted into a parallel light beam by the collimator lens is generally “circular or elliptical”. Then, the illumination light beam having such a cross-sectional shape is converted into a ring shape, that is, an “annular or elliptical ring”, and used for illumination.

The “calculation means” can set the data on the anterior chamber basic data and the “correspondence relationship between the refractive index of the medium in the anterior chamber and the glucose concentration”, and the illumination light beam is the front boundary surface of the anterior chamber. And the refractive index of the chamber medium is calculated based on the “optical thickness of the anterior chamber” detected as the “displacement amount of the condensing position” when condensing on the rear boundary surface, and the calculated refraction Based on the rate, it has a function of calculating the “glucose concentration in the anterior chamber medium”.

  “Anterior chamber basic data” is personal data of a user who uses the glucose measuring device (a person to be measured for glucose concentration), and the “anterior chamber thickness” and the anterior chamber measured in advance. This is the “standard refractive index” of the inner medium. “Anterior chamber thickness” is substantially constant.

The “correspondence between the refractive index of the anterior chamber medium and the glucose concentration” is basically the correspondence between both in the measurement subject. For example, the relationship described in Patent Document 1:
n = 1.333322 + 1.6 × 10 ⁻⁶ × G (n: G: glucose concentration (mg / dl) of anterior chamber medium)
Can be used.

“Anterior boundary surface of the anterior chamber (hereinafter, simply referred to as“ anterior boundary surface ”) refers to a boundary surface between the anterior chamber and the cornea.
The “rear interface of the anterior chamber (hereinafter simply referred to as“ rear interface ”) refers to the interface between the anterior chamber and the crystalline lens.
The boundary surface between the cornea and the air is referred to as the “corneal surface” as described above, and the boundary surface between the crystalline lens and the vitreous body is referred to as the “rear lens boundary surface”.

  The “glucose concentration in the anterior chamber medium” is the concentration of glucose contained in the anterior chamber medium filling the anterior chamber. As described above, this glucose concentration has a high correlation with the blood glucose concentration.

  The “ring-shaped light beam forming means” focuses the measurement light beam on one boundary surface (the “corneal surface”, “front boundary surface”, “rear boundary surface”, “rear lens boundary surface”) of the eyeball. The inner diameter of the ring-shaped illumination light beam (ring-shaped) so that the inner diameter of the “ring image formed on the pinhole plate” is equal to or larger than the opening diameter of the pinhole. It has the function of regulating the “inner diameter of the“ ring-shaped cross-section ”” of the illumination light beam.

  Condensed light from the condensing lens is “incident while converging toward the eyeball.” For example, when the illumination light is focused on the corneal surface, the front boundary surface, the rear boundary surface, and the back of the lens The light that irradiates the side boundary surfaces is divergent, and these boundary surfaces are irradiated in a ring shape.

  Since the cornea, the anterior chamber, the crystalline lens, and the vitreous body are composed of media having different refractive indexes, the refractive index changes discontinuously at the boundary surface, and thus reflection occurs at these boundary surfaces.

  At this time, the light that irradiates the corneal surface is focused on the corneal surface, so the reflected light from the corneal surface has the “condensing position” as an object point, and the pinhole is caused by the action of the condensing lens and the detection lens Condensed at the pinhole position of the plate. If the beam waist diameter of the condensed light beam at the pinhole position is larger than the opening diameter of the pinhole, the reflected light (measurement light beam) from the corneal surface is incident on the light receiving surface of the photodetector.

  The reflected light from the “ring-irradiated portion” of each boundary surface forms a “ring-shaped image (ring image)” in the vicinity of the pinhole plate by the condenser lens and the detection lens. Since the image forming position is “deviation” from the pinhole plate, it is “slightly blurred” on the pinhole plate.

Also, in the state where the condensed light beam from the condensing lens is focused on the front boundary surface, the corneal surface is irradiated in a ring shape by the light beam during focusing, and the rear boundary surface and the rear boundary surface of the lens are diverged. Irradiated in a ring shape.
The reflected light from the front boundary surface is collected at the pinhole position. The “reflected light from the ring-shaped irradiated portion” on the corneal surface, the rear boundary surface, and the rear surface boundary surface of the lens again irradiates the “ring-shaped” portion slightly blurred on the pinhole plate.

Similarly, in a state in which the condensed light beam from the condenser lens is “condensed on the rear boundary surface”, the corneal surface and the front boundary surface are irradiated in a ring shape by the light beam during focusing, and the rear boundary surface of the crystalline lens is in a divergent state. It is irradiated in a ring shape with the luminous flux.
The reflected light from the rear boundary surface is condensed at the pinhole position. The “reflected light from the ring-shaped irradiated portion” on the corneal surface, the front boundary surface, and the rear surface boundary surface of the lens is also irradiated in a “ring shape” slightly blurred from the pinhole plate.

  When the condensed light beam is focused on the lens rear boundary surface, the cornea surface, the front boundary surface, and the rear boundary surface are all irradiated in a ring shape by the light beam during focusing, and reflected from these irradiated portions The light irradiates a “slightly blurred ring-shaped portion (ring image)” on the pinhole plate. The reflected light at the rear boundary surface of the crystalline lens is collected at the pinhole position.

  Therefore, the opening diameter of the pinhole is larger than the “beam waist of the light beam condensed at the pinhole position” and is the smallest among the “ring-shaped irradiated portions (ring images) generated on the pinhole plate”. If it is smaller than the "inner diameter of the object", each reflected light from the "corneal surface or other boundary surface" where the condensed light beam is condensed can be properly guided to the photodetector through the pinhole, and Reflected light from the “surface irradiated in a ring shape without condensing” is effectively blocked by the pinhole plate to the photodetector and does not become noise light for measurement.

The “condensing position displacing means” used in the glucose concentration measuring device according to claim 1 or claims 2 and 3 described later can be a lens displacing device that displaces the condensing lens in the optical axis direction ( Claim 4 ).
As the condensing position displacement means, the “illumination light source, collimating lens, condensing lens, light detector, optical path separating means, detection lens, pinhole plate, ring-shaped light beam forming means” of the above-mentioned optical device are integrated. It may be configured as a displacement means that integrally displaces them in the optical axis direction of the condenser lens.

The glucose concentration measuring apparatus according to claim 1 or claim 2 described later also includes a quarter-wave plate “between the condenser lens and the optical path separating position of the optical path separating means”, and the optical path separating position 1 / A ring-shaped light beam forming means is arranged between the four-wavelength plate.

The “optical path separation position” is a position where the optical path of the measurement light beam is separated from the optical path for the illumination light beam.

In the glucose concentration measuring apparatus according to claim 1, the ring-shaped light beam forming means “shields at least the light beam central portion of the illumination light beam converted into a parallel light beam by the collimating lens, and collects the condensing lens, the quarter-wave plate, and the like from the eyeball. Is a polarization-selective light-shielding plate that transmits the measurement light beam returning through the light path to the optical path separation position side as it is.
3. The glucose concentration measuring apparatus according to claim 2, wherein the ring-shaped light beam forming means “diffracts at least the light beam central portion of the illumination light beam converted into a parallel light beam by the collimating lens and removes it from the illumination light beam, and collects the light from the eyeball. And a polarization-selective diffractive element that transmits the measurement light beam returning through the ¼ wavelength plate to the optical path separation position side as it is.

As a reference example, it is conceivable that the “ring-shaped light beam forming means” is a “diffractive element that diffracts at least the central part of the light beam and removes it from the illumination light beam” of the illumination light beam that is collimated by a collimator lens .

The “ring-shaped light beam forming means” in the glucose concentration measuring apparatus according to claim 3 is a first optical element that converts a cross-sectional shape of a light beam for illumination that has been converted into a parallel light beam by a collimating lens into a “ring-shaped divergent light”. When, and a second optical element for converting the light beam that has been converted into a ring-shaped divergent light "parallel beam having a ring-shaped light flux cross-section."

Glucose concentration measuring apparatus according to any one of the preceding claims 1 to 4, may have a "band-pass filters light of a wavelength of the illumination light flux is transmitted" to the eyeball side of the condenser lens (claim 5 ).
The “band-pass filter” may be any filter that can effectively remove external light that causes disturbance to the measurement, and may be any filter that appropriately passes light in a wavelength band including the illumination light beam.

In the glucose concentration measuring apparatus according to claim 5 , any one of the light source for illumination and the band pass filter may include a “deflection mirror for deflecting the optical path” (claim 6).

The “optical device” of the present invention is an optical device used in the glucose concentration measuring device according to any one of claims 1 to 6 ( claim 7 ).

An “ring-shaped light beam forming device ” according to claim 8 is a ring-shaped light beam forming device used as a ring-shaped light beam forming unit in the glucose concentration measuring device according to any one of claims 1 to 6 .

A glucose concentration measuring method according to claim 9 is a glucose concentration measuring method using the glucose concentration measuring device according to any one of claims 1 to 6 .

  As described above, according to the present invention, measurement noise in the glucose measuring device can be effectively reduced or prevented, and the glucose concentration can be measured with high accuracy.

  Further, the glucose measuring device of the present invention can be formed in a small size as in the embodiments described later, and can be easily carried.

Hereinafter, embodiments will be described.
FIG. 1 is a diagram for explaining a glucose concentration measuring apparatus and measurement .
In FIG. 1A, reference numeral 11 denotes a light source for illumination, reference numeral 12 denotes a collimator lens, reference numeral 13 denotes a light shielding plate, reference numeral 14 denotes a polarizing beam splitter, reference numeral 15 denotes a quarter-wave plate, reference numeral 16 denotes a condensing lens, reference numeral Reference numeral 17 denotes an eyeball, reference numeral 18 denotes a detection lens, reference numeral 19 denotes a pinhole plate, reference numeral 20 denotes a photodetector, reference numeral 21 denotes an external light cut filter, reference numeral 22 denotes a displacement means, and reference numeral 23 denotes a control / calculation display means.

  The illumination light source 11 is a laser light source, and in this example, an “edge-emitting semiconductor laser” is used. The emitted light is “invisible light region (for example, wavelength: 850 nm) laser light” in the infrared region and is invisible light, so even if this is irradiated to the eyeball, it does not “close the pupil”. Measurement can be performed.

  The laser light emitted from the illumination light source 11 is converted into parallel light by the collimator lens 12 to become the illumination light beam LA, and passes through the light shielding plate 13 disposed so as to be orthogonal to the principal ray of the illumination light beam LA.

  The light shielding plate 13 constitutes “a ring-shaped light beam forming means that shapes the cross-sectional shape of the illumination light beam LA converted into a parallel light beam by the collimator lens 12 into a ring shape to obtain a ring-shaped illumination light beam LB”.

  That is, the light shielding plate 13 is formed by forming a “light shielding pattern by metal vapor deposition, etc.” on one side of a transparent parallel flat plate, and as shown in FIG. It has light shielding parts 13b and 13c. Light shielding by the light shielding portions 13b and 13c may be performed by absorption or reflection.

  Therefore, as shown in FIG. 1D, when the illumination light beam LA passes through the light shielding plate 13, the passed light beam becomes a ring-shaped illumination light beam LB whose “beam cross-sectional shape LB1 is ring-shaped”. The center of the annular light transmitting portion 13a of the light shielding plate 13 coincides with the position of the principal ray of the illumination light beam LA.

  In other words, the light shielding plate 13 shields “at least the light flux central portion of the illumination light beam LA converted into a parallel light beam by the collimator lens 12”.

In this way, the ring-shaped illumination light beam LB which is “a parallel light beam whose beam cross-sectional shape is a ring shape” enters the polarization beam splitter 14.
The laser light emitted from the illumination light source 11 is in a “substantially linear polarization state”, and the state of the polarization beam splitter 14 is adjusted so as to transmit the ring-shaped illumination light beam LB as P-polarized light.

  The ring-shaped illumination light beam LB transmitted through the polarization beam splitter 14 is then transmitted through the quarter-wave plate 15 and converted to “circularly polarized light”, converted into a condensed light beam by the condenser lens 16, and the external light cut filter 21. To the eyeball 17 through the lens.

  The external light cut filter 21 is effective in “preventing external light from acting as noise”, and it is preferable to use this, but it is not always necessary in terms of measurement.

  The light reflected by the eyeball 17 becomes “return light” and becomes “measurement light beam LC” via the external light cut filter 21 and the condenser lens 16.

  The measurement light beam LC is in a linearly polarized state when transmitted through the quarter-wave plate 15, but its polarization plane is orthogonal to the polarization plane of the ring-shaped illumination light beam LB, so It becomes a polarization state, is reflected by the polarization beam splitter 14, and is separated from the optical path of the ring-shaped illumination light beam LB.

  That is, the polarization beam splitter 14 and the quarter wavelength plate 15 constitute “optical path separating means”.

Thus, the measurement light beam LC separated from the optical path of the ring-shaped illumination light beam LB (also the optical path of the illumination light beam LA) is condensed by the detection lens 18 and directed toward the pinhole plate 19.
If the measurement light beam LC is a parallel light beam, the “condensing position of the measurement light beam LC” by the detection lens 18 is the focal position of the detection lens 18, and the pinhole plate 19 is arranged so as to coincide with the focal plane including this focal point. The position of the pinhole 19a coincides with the above "focus".
Therefore, the condensing lens 16 and the detection lens 18 constitute a “confocal optical system”.

As shown in FIG. 1 (e), the pinhole plate 19 is formed with a pinhole 19a at the center and is disposed in the vicinity of the light receiving surface of the photodetector 20, and the measurement light beam LC is emitted only at the pinhole 19a. Let it pass.
Then, only “the portion that has passed through the pinhole 19 a” of the measurement light beam LC is incident on the light receiving surface of the photodetector 20.
The opening diameter of the pinhole 19a is set to be approximately equal to the condensing diameter (beam waist diameter) collected by the detection lens 18 when the measurement light beam LC in a parallel light beam state enters the detection lens 18.

  The photodetector 20 outputs an electrical signal corresponding to the amount of light received, and this output is input to the control / calculation display device 23. The control / calculation display device 23 constitutes “calculation means” in this embodiment.

  The displacing means 22 constitutes “condensing position displacing means” and displaces the condensing lens 16 in the optical axis direction (vertical direction in FIG. 1A). As the displacing means 22, a “suitable one conventionally known” such as a motor and a guide mechanism can be used.

  Since the ring-shaped illumination light beam LB incident on the condensing lens 16 is a parallel light beam, the distance between the condensing lens 16 and the “condensing position of the ring-shaped illumination light beam LB by the condensing lens 16” is invariable. By displacing the lens 16 in the optical axis direction, the condensing position can be displaced in the optical axis direction (while keeping the distance from the condensing lens 16 constant).

  The control / calculation display device 23 constituting the “calculation means” controls the displacement of the condenser lens 16 by the displacement device 22 and determines the displacement amount of the condenser lens 16.

Here, the structure of the eyeball 17 will be described by simplifying only the “portion necessary for measurement”.
In FIG. 1B, the portion indicated by reference numeral 17a is the “cornea”, the portion indicated by reference numeral 17c is the “crystal”, and the portion indicated by reference numeral 17d is the “vitreous body”.

  A portion sandwiched between the cornea 17a and the crystalline lens 17c is an “anterior chamber” and is denoted by reference numeral 17b.

  In FIG. 1B, reference numeral R1 is a “corneal surface”, which will be simply referred to as “surface R1”.

  Reference symbol R2 is a boundary surface (“anterior boundary surface”) between the cornea 17a and the anterior chamber 17b, and is simply referred to as “surface R2”. Similarly, the reference symbol R3 is a boundary surface between the anterior chamber 17b and the crystalline lens 17c (“rear boundary surface”), hereinafter simply referred to as “surface R3”, and a reference symbol R4 is simply the boundary surface between the crystalline lens 17c and the vitreous body 17d. This is referred to as “surface R4”.

In the following description, the “surface interval in the eyeball” is the distance between adjacent surfaces on this straight line when considering the “horizontal line (eyeball optical axis) passing through the center” of the eyeball shown in FIG. Is the interval.
Speaking of the anterior chamber 17b, it is “the portion between the plane R2 and the plane R3 on the straight line”, and the “interval between the planes R2 and R3” is hereinafter referred to as the thickness of the anterior chamber 17b: d. The thickness of the anterior chamber 17b: d is an “individual amount”, but does not substantially change with the environment and time, and therefore can be treated as a “constant” in calculating the optical thickness. .

  On the other hand, the refractive index of the “anterior chamber medium” that fills the anterior chamber 17b is an amount that changes according to the physical condition, and is represented by “n”. At this time, the optical thickness of the anterior chamber 17b is “n · d”.

  The “refractive index of the anterior chamber medium” is measured in advance by the measurement subject, and the control / calculation display device uses the value when giving a reference refractive index: n0 (corresponding to an appropriate glucose concentration) as a reference value. 23 is set in advance. That is, “d” and “n0” are “anterior chamber basic data”.

  Further, the correspondence between the refractive index n of the anterior chamber medium and the glucose concentration (predetermined by measurement) is also preset in the control / calculation display device 23.

  As will be described later, the optical thickness of the anterior chamber 17b is measured as the amount of displacement of the condenser lens 16, and the refractive index n of the anterior chamber medium is controlled from the optical thickness and the anterior chamber reference data. Calculated by the calculation display device 23.

Based on the refractive index n thus calculated and the above-mentioned “refractive index of the anterior chamber medium: correspondence between n and glucose concentration”, the glucose concentration is determined by the control / calculation display device 23.
The determined glucose concentration is displayed on a “display unit (display not shown)” of the control / calculation display device 23. The display unit may be an “external device” and separate from the glucose concentration measuring device.

As described above, the glucose concentration measurement apparatus shown in FIG. 1 detects the optical thickness of the anterior chamber 17b in the eyeball 17: (n · d) by an optical method, and detects the detected optical thickness. Based on the above, the refractive index: n of the anterior chamber medium is calculated, and the calculated refractive index: n is used to set the glucose of the anterior chamber medium based on a preset “correlation between refractive index and glucose concentration”. It is a glucose concentration measuring device that calculates and calculates the concentration.

  This device is an optical device that optically detects the optical thickness of the anterior chamber 17b of the eyeball: (n · d), and the inside of the anterior chamber based on the optical thickness detected by this optical device. And calculating means 23 for calculating the refractive index of the medium and calculating the glucose concentration of the anterior chamber medium corresponding to the calculated refractive index.

  The “optical device” includes an illumination light source 11, a collimator lens 12 that collimates a laser beam emitted from the illumination light source, and an illumination beam LA that has been collimated by the collimator lens 12. A condensing lens 16 for converting to a condensing light beam that converges toward the light source, a photodetector 20 that receives the measurement light beam LC returned from the eyeball 17 via the condensing lens 16 and converts it into an electrical signal, and a measurement light beam LC. Are separated from the light path of the illumination light beam LA to the light detector 20 side, and the measurement light beam LC separated by the light path separation device is condensed toward the light receiving surface of the light detector 20. When the condensing position of the light beam LA (LB) for illumination by the condensing lens 16 is set as an object point, the condensing lens 16 and the detecting lens 1 The condensing position of the light flux for illumination by the pinhole plate 19 having the pinhole 19a having a predetermined aperture at the “image point position with respect to the object point” and the condenser lens 16 is displaced in the optical axis direction of the condenser lens 16. The cross-sectional shape of the illumination light beam LA arranged on the optical path between the condensing position displacement means 22 and the collimating lens 12 and the condensing lens 16 and converted into a parallel light beam by the collimating lens 12 is shaped into a ring shape to form a ring. And a ring-shaped light beam forming means 13 for forming a ring-shaped illumination light beam LB.

  The calculation means 23 can set data on the correspondence between the anterior chamber basic data: (d, n0) and the refractive index of the anterior chamber medium: n and the glucose concentration.

The outline of measurement will be described below.
In FIG. 1A, when the condensing lens 16 is displaced toward the eyeball 17 on the optical axis by the displacing means 22, first, the condensed light beam by the condensing lens 16 is a surface R1 which is the surface of the cornea 17a. Concentrate on top. FIG. 1A shows this state.

  At this time, the light reflected by the surface R1 enters the light receiving surface of the photodetector 20 as a measurement light beam, but the reflection point of the light reflected by the surface R1 and the position of the pinhole 19a are Since the confocal optical system with the detection lens 18 has a conjugate relationship, the measurement light beam passes through the pinhole 19a and enters the photodetector 20 as the maximum light amount.

  As the condensing lens 16 is further displaced toward the eyeball side, the condensing position of the condensed light beam is directed toward the inside of the eyeball 17, and the condensed light beam is sequentially condensed on the positions of the surfaces R2, R3, and R4. Each time the light is condensed, the confocal optical system has a conjugate relationship, and the amount of light incident on the light receiving surface of the photodetector 20 increases.

  FIG. 1F shows the relationship between the displacement amount of the condenser lens 16 and the output of the photodetector 20 with the “displacement amount” of the condenser lens as the horizontal axis and the “output” of the photodetector 20 as the vertical axis. Is shown. The amount of displacement on the horizontal axis is “the displacement toward the eyeball side is positive” of the condenser lens 16.

  According to the displacement of the condensing lens 16, four maxima LR1, LR2, LR3, and LR4 are sequentially generated in the output. As is clear from the above description, the maximum LR1 occurs in the state where the condensed light beam is condensed on the surface R1, and the maximum light beams LR2, LR3, and LR4 are collected on the surfaces R2, R3, and R4. Occurs when illuminated.

  At this time, the displacement amount DS shown in FIG. 1 (f) indicates that the condensed light beam is focused on the surface R3 from the state where the condensed light beam is condensed on the surface R2 (an anterior boundary surface that is a boundary surface between the cornea and the anterior chamber). This is the “displacement amount of the condensing lens 16 that is displaced until the light is focused on the rear boundary surface that is the boundary surface between the anterior chamber and the crystalline lens”. This is “the optical thickness of the anterior chamber 17b”. Is equal to n: d ”.

  The control / calculation display device 23 which is a calculation means specifies the optical amount of the anterior chamber: n · d with the displacement amount: DS.

As described above, since the anterior chamber basic data: (d, n0) is set in the control / calculation display device 23 in advance, the “reference optical thickness: d · n0” of the anterior chamber 17b is known. is there.
And, “the thickness of the anterior chamber 17b: d” in the anterior chamber basic data does not substantially change with the environment and time, and can be treated as a “constant” in calculating the optical thickness. The refractive index n of the anterior chamber medium at the time of measurement can be calculated from the known amounts d and n0 and the “measured optical thickness: n · d” specified as the displacement amount DS.

That is, if the difference between the measured optical thickness: DS and the reference optical thickness: n0 · d is “ΔD”, the difference is the refractive index at the time of measurement: n and the reference refractive index. : Difference from n0: by Δn, therefore
ΔD = Δn · d
The amount of change in refractive index: Δn is
Δn = ΔD / d
From this, the refractive index of the anterior chamber medium specified by measurement: n is
n = n0 + ΔD / d
Can be calculated as

  The control / calculation display device 23 performs the above calculation to calculate the refractive index: n of the anterior chamber medium.

  The refractive index: n calculated in this way is used, and the “refractive index: correspondence between n and glucose concentration preset in the control / calculation display device 23 (this relationship may be given as a table). And may be given in the form of an arithmetic expression.) ”), The glucose concentration is determined and displayed on the display unit. Therefore, the “calculation of glucose concentration” can be performed in the form of calculation using an arithmetic expression or in the form of reference to a table.

  The determined glucose concentration can be recorded as data using an external memory card (SD card) instead of notifying the measurement subject in real time by displaying on the display unit, or together with displaying on the display unit. It is.

  As described above, the control / calculation display device 23 which is the “calculation means” condenses the illumination light beam (LA, LB) on the front boundary surface R2 of the anterior chamber 17b and then condenses it on the rear boundary surface R3. The refractive index n of the anterior chamber medium is calculated based on the “optical thickness of the anterior chamber” detected as “displacement amount of the condensing position: DS” until the calculation is performed, and the calculated refractive index is calculated. : Has a function of calculating the glucose concentration of the anterior chamber medium based on n.

  If the opening diameter of the pinhole 19a in the pinhole plate 19 is made too small, there is a problem that the amount of the measurement light beam reaching the photodetector is reduced and the measurement accuracy is lowered or the measurement takes a long time. The “aperture diameter” needs to be larger than the so-called beam waist diameter when the measurement light beam is condensed by the detection lens 18 when “the parallel light beam”.

However, when the opening diameter of the pinhole 19a is large, a noise component included in the measurement light beam LC may be detected and the measurement accuracy may be reduced.
In the present invention, the influence of the “noise component contained in the measurement light beam” is removed or effectively reduced as follows.

  As described above, as the condensing lens 16 is displaced toward the eyeball 17 in the direction of the optical axis, the condensed light beam is sequentially condensed on the surfaces R1 to R4, and is output to the output of the photodetector 20 as shown in FIG. The maximums LR1 to LR4 shown in (f) are generated.

  As described above, when the condensed light beam is condensed on any one of the surfaces R1 to R4, for example, the surface R2, the other surfaces, that is, the surfaces R1, R3, and R4 are part of the ring-shaped illumination light beam LB. The light beam which has been “irradiated in a ring shape” and is reflected by these ring-shaped irradiation parts becomes a part of the measurement light beam, enters the detection lens 18, and converges toward the pinhole plate 19.

  As described above, when the condensed light beam collected by the condenser lens 16 is condensed on the surface Ri (i = 1 to 4), the reflected light from the other surface Rj (j ≠ i) is “one of the measurement light beams. When the light is received by the light detector 20, the output of the light detector 20 is affected as a noise component.

  The influence of such noise components broadens the width of the “maximum output” shown in FIG. 1 (f), lowers the system of displacement distance: DS, and consequently the optical thickness of the anterior chamber and the glucose concentration. Cause an error.

  In the present invention, the influence of such a noise component is eliminated or effectively reduced by adjusting the “inner diameter of the annular light beam cross section” of the ring-shaped illumination light beam LB by the ring-shaped light beam forming means 13.

  Since the condensing lens 16 and the detection lens 18 constitute a “confocal optical system” as described above, the condensing position of the condensed light beam condensed by the condensing lens 16 and the position of the pinhole 19a are: As described above, there is a conjugate relationship.

  Therefore, when the condensed light beam from the condenser lens 16 is condensed on the “certain surface Ri (i = 1 to 4)”, the reflected light from the other surface Rj (j ≠ i) is reflected on the condenser lens 16. The position where light is collected by the detection lens 18 is shifted in the “front-rear direction of the pinhole plate 19” on the optical axis of the detection lens 18.

  Reflection by the surface Rj on the rear side (the side far from the condensing lens 16) from the surface Ri in the case where the condensed light beam by the condensing lens 16 is “condensed on a certain surface Ri (i = 1 to 4)”. As shown in FIG. 2A, the “position where light is collected by the detection lens 18” is shifted to the “detection lens 18 side” from the pinhole plate 19.

  On the contrary, in the case where the condensed light beam by the condenser lens 16 is condensed on the surface Ri (i = 1 to 4), the reflection by the surface Rk on the front side (side closer to the condenser lens 16) than the surface Ri. As shown in FIG. 2B, the “position where light is collected by the detection lens 18” is shifted to the “side away from the detection lens 18” with respect to the pinhole plate 19.

  In FIG. 2, the surface indicated by the symbol P is the position where the reflected light from the surfaces Rj and Rk is collected.

  Reflected light from the surfaces Rj (j ≠ i) and Rk (k ≠ i) is a noise component included in the measurement light beam, but is “ring-shaped” on the pinhole plate 19 as shown in FIG. This is because the eyeball is illuminated with “light that has condensed the ring-shaped illumination light beam”.

  These “reflected light by Rj (j ≠ i) and Rk (k ≠ i)” are hereinafter referred to as “noise light”.

The portion where the noise light irradiates the pinhole plate 19 in a ring shape with respect to the opening diameter of the pinhole 19a (indicated by the symbol “φp” in FIG. 2). If the inner diameter of the “irradiation ring” is always increased, the influence of the noise light can be eliminated.
This is possible by restricting the “inner diameter of the annular light beam cross section” of the ring-shaped illumination light beam LB by the ring-shaped light beam forming means 13.

  In other words, the ring-shaped light beam forming means receives “noise light” reflected by the other surface Rj (j ≠ i) when the focused light from the condensing lens 16 is condensed on one surface Ri of the eyeball 17. The function of regulating the inner diameter of the ring-shaped illumination light beam LB is provided so that the inner diameter of the “irradiation ring” that irradiates the pinhole plate 19 is equal to or larger than the opening diameter of the pinhole 19a: φp.

  The “deviation amount with respect to the pinhole plate 19: L” at the position where the noise light is collected by the detection lens 18 corresponds to the “distance from the surface Ri” of the surface Rj (j ≠ i) where the noise light is reflected. Change.

  More specifically, the wavelength of the laser beam emitted from the illumination light source 10: λ, the beam diameter of the illumination beam LA converted into a parallel beam by the collimator lens 12 (the outer diameter of the transmission part 13a of the light shielding plate 13): Calculation is performed using φC, the focal length of the condenser lens 16: fO, the focal length of the detection lens 18: fC, and the distance Ri between the surfaces Ri and Rj of the eyeball 17: ΔT.

(A) “Pinhole 19a diameter: φP”
The diameter (opening diameter) of the pinhole 19a: φP corresponds to the beam waist diameter when the normal measurement light beam (measurement light beam condensed and reflected on the surface Ri) is collected by the detection lens 18, and (1).

The diameter of the pinhole 19a calculated by the equation (1): φP is “the minimum diameter necessary for allowing the regular reflected light collected by the detection lens 18 to pass”, and is calculated by the equation (1). The diameter may be set to φP with a value greater than or equal to the value to be obtained.
φP = K × λ / NA = K × λ / {φC / (2 × fC)} (1)
In (1), K is “a coefficient set by the light intensity distribution of laser light”, and NA is “the numerical aperture of the detection lens 18”, which is approximated by “{φC / (2 × fC)}”.

(B) “Distance between the condensing position of the reflected light (noise light) from the other surface Rj (j ≠ i) by the detection lens 18 (position indicated by the symbol P in FIG. 2) and the pinhole plate 19: L "
Distance: L is calculated by the following near-order expression (2).

L = (2 × ΔT) × (fC / fO) ² (2)
“(FC / fO) ² ” is the vertical magnification of the “confocal optical system” formed by the condenser lens 16 and the detection lens 18, and ΔT is the surface Ri (the condensed light beam by the condenser lens 16 is condensed). And the surface Rj.

(C) “Inner diameter / outer diameter of shading plate 13”
The diameter: φS of the light shielding portion 13b of the light shielding plate 13 is calculated.

  As shown in FIGS. 2A and 2B, the “angle with respect to the optical axis of the condensed noise light” differs depending on the position of the condensing point P of the noise light, and the diameter of the light shielding portion 13b: φS is also the condensing point. It depends on the position of P.

  When the condensing point P is positioned “behind the pinhole plate 19” as shown in FIG. 2B, the “angle with respect to the optical axis” of the noise light is small and formed on the pinhole plate 19. When the inner diameter of the “irradiation ring” is “when the diameter of the pinhole 19a is smaller than φP”, the light flux portion that passes through the pinhole 19a causes noise, so this condensed light flux irradiates the pinhole plate 19. The diameter: φS of the light shielding portion 13b must be set so that the inner diameter of the irradiation ring becomes equal to or larger than the diameter: φP of the pinhole 19a.

“Diameter of the light shielding portion 13b when the condensing point position P by the detection lens 18 on the other surface Rj is on the near side of the pinhole Pa as shown in FIG. 2A: φSF”
The inner diameter of the ring irradiated with noise light from the surface Rj formed on the pinhole plate 19 through the condensing point P is the same as the pinhole diameter: φP. In this case, “in the noise light incident on the detection lens 18 When the diameter of the “light-shielded portion at the center of the light beam”, that is, the diameter of the light-shielding portion 13b is φSF, Expression (3) is established.

(ΦP / 2) / L = (φSF / 2) / (fC−L) (3)
This can be transformed as shown in equation (4).

φSF = fC × φP / L−φP (4)
In this case, since the diameter of the light shielding part 13b: φSF represents the “minimum size” of the light shielding part 13b, the diameter of the light shielding part 13b: φSF can be defined by the following equation (5).
φSF ≧ fC × φP / L−φP (5)
“The diameter of the light-shielding portion 13b when the position of the“ condensing point P by the detection lens 18 ”of the noise light from the other surface Rj is behind the pinhole 19a as shown in FIG. 2B: φSR”
In this case, a part of the noise light from the other surface Rj collected by the detection lens 18, specifically, the irradiation ring in which the noise light irradiates the peripheral portion of the pinhole 19 a of the pinhole plate 19. The “portion inside the pinhole 19 a” passes through the pinhole 19 a and is condensed behind the pinhole plate 19.

Therefore, if the diameter of the “light shielding portion at the center” of the noise light that has reached the pinhole 19 is the same as the pinhole diameter: φP, and the diameter of the light shielding portion 13b in this case is φSR, then the equation (3 The following equation (6) is established in the same manner as above, and the diameter: φSR of the light shielding portion 13b can be defined by the equation (7) based on the equation (6) as in the above.
(ΦP / 2) / L = (φSR / 2) / (fC + L) (6)
φSR ≧ fC × φP / L + φP (7)
Comparing the diameter: φSF and the diameter: φSR of the light shielding part 13b defined by the expressions (5) and (7), the diameter: φSR is always larger than the diameter: φSF.

  Therefore, it is preferable to adopt the diameter: φSR as the diameter: φS of the light shielding portion 13b.

FIG. 3 is an explanatory view showing one embodiment of the glucose concentration measuring apparatus. In order to avoid complications, the same reference numerals as in FIG. 1 are used for those that are not likely to be confused.

In this embodiment , a quarter-wave plate 15 is provided between the condenser lens 16 and the optical path separation position (the separation surface of the polarization beam splitter 14) in the optical path separation means, and the optical path separation position and the quarter-wave plate 15 are provided. The ring-shaped light beam forming means 31 is disposed between the two.
The ring-shaped light beam forming means 31 shields at least the light beam central portion of the illumination light beam LA converted into a parallel light beam by the collimator lens 12 and returns from the eyeball 17 through the condenser lens 16 and the quarter wavelength plate 15. This is a “polarization-selective light shielding plate” that transmits the light beam as it is to the optical path separation position side.

As shown in FIG. 3B, the polarization-selective light shielding plate 31 is formed with light shielding portions 31b and 31c with a ring-shaped light transmission portion 31a interposed therebetween.
The illumination beam LA emitted from the illumination light source 11 and converted into a parallel beam by the collimator lens 12 is transmitted through the polarization beam splitter 14, and the light shielding units 31b and 31c block the illumination beam LA in the linearly polarized state. Thus, the ring-shaped illumination light beam LB is obtained.

  The measurement light beam returning from the eyeball 17 is transmitted through the quarter-wave plate 15 and converted in the direction orthogonal to the forward path through the polarization plane, and is transmitted through the ring-shaped light beam forming means 31 as it is to return to the polarization beam splitter 14. , Separated from the light path of the illumination light beam LA.

  As the light-shielding portions 31b and 31c of the polarization-selective light-shielding plate 31, a polarizer, for example, a generally known “multilayer film structure using an autocloning method” or the like may be used.

  The shapes of the light-shielding portions 31b and 31c in the polarization-selective light-shielding plate 31 are set in the same manner as in the above-described embodiment of FIG.

  In the embodiment of FIG. 3, the condenser lens 16, the quarter-wave plate 15, and the polarization-selective light-shielding plate 31 are integrated by the housing HS, and the optical axis of the condenser lens 16 along with the housing HS by the displacing means 16. Displaceable in the direction.

  By doing so, the housing HS is integrally displaced by the displacement device 22, so that “variation in the positional relationship between the condenser lens 16 and the light shielding plate 31” can be reduced, and the light spot can be accurately applied to a predetermined surface of the eyeball 17. Can be formed.

For example, the polarization-selective light shielding plate and the quarter wavelength plate are formed as a light shielding film 311 and a quarter wavelength film 312 on both surfaces of the transparent parallel plate 310 as shown in FIG. May be integrated.
In this way, the operation load of the displacement device 22 can be reduced as the number of parts is reduced and the weight is reduced, and more stable “position control of the condenser lens 16” is possible.

FIG. 4 is a diagram for explaining another example of the glucose concentration measuring apparatus .
In order to avoid confusion, parts that are not likely to be confused are given the same reference numerals as in FIG.

The apparatus of FIG. 4 is obtained by replacing the light shielding plate 13 as a ring-shaped light beam forming unit with a diffraction element 32 in the configuration shown in FIG.
As shown in FIG. 4B, the diffractive element 32 is formed with a “concentric diffraction grating”.

  The “diffraction grating” is formed in the regions 32b and 32c shown in FIG. 4C, and the region 32a is a “transmission region”.

  Therefore, as shown in FIG. 4D, when the illumination light beam LA converted into a parallel light beam by the collimator lens is incident on the diffraction element 32, the light beam incident on the region 32a (FIG. 4C) is transmitted as it is. A ring-shaped illumination light beam LB having a ring-shaped light beam cross section LB1.

  The illumination light beam LA incident on the part other than the transmission region 32a is diffracted as the diffracted light LC by the diffraction element 32 and removed from the illumination light beam LA, and is not involved in the measurement.

In the diffraction grating 32, the shapes of the regions 32b and 32c where the diffraction grating is formed are set in the same manner as in the embodiment of FIG. 1 described above.
As the groove shape of the cross section of the diffractive element, a rectangular shape may be used, and the groove depth may be selected so that the first-order diffracted light is the strongest.

  The groove pitch of the diffraction grating is “a narrow pitch structure sufficient to scatter the diffracted diffracted light LC so that the diffracted light LC does not converge on the eyeball 17 and noise light returning from the eyeball 17 does not enter the photodetector 20”. I just need it. Note that the shape of the diffraction groove is not limited to a rectangular shape, and may be a stepped shape or a sawtooth shape. In particular, the sawtooth shape is suitable as a light shielding function because it has a high diffraction efficiency.

FIG. 5 is a diagram for explaining “another embodiment” of the glucose concentration measuring apparatus .
In order to avoid confusion, parts that are not likely to be confused are given the same reference numerals as in FIGS.

This embodiment is characterized in that, in the embodiment shown in FIG. 3, a “polarization-selective diffraction element 32A” is used in place of the polarization-selective light shielding plate 31.
As shown in the figure, also in this embodiment, the light shielding plate 32A, the quarter-wave plate 15 and the condenser lens 16 are integrated by the housing HS, and the optical axis of the condenser lens 16 is displaced by the displacement means 22 together with the housing HS. It can be displaced in the direction.

  Therefore, when the housing HS is displaced by the displacement device 22, the positional relationship between the condenser lens 16 and the light shielding plate 32 </ b> A can be reduced, and a light spot can be accurately formed on the predetermined boundary surface of the eyeball 17.

  In the embodiment of FIG. 5A, a quarter-wave plate 15 is provided between the condenser lens 16 and the “optical path separating position of the optical path separating means (polarizing beam splitter 14)”. A ring-shaped light beam forming means 32A is disposed between the quarter wave plates 15, and the ring-shaped light beam forming means 32A diffracts at least the light beam central portion of the illumination light beam LA converted into a parallel light beam by the collimator lens 12. This is a “polarization-selective diffraction element 32A” that removes the light flux LA from the eyeball 17 and returns the measurement light flux returned from the eyeball 17 through the condenser lens 16 and the quarter-wave plate 15 to the optical path separation position.

  As shown in FIG. 5B, the polarization selective diffraction element 32A diffracts the central portion of the light beam LA as the diffracted light LC from the illumination light beam LA and removes it from the light beam LB for illumination. It is formed as a ring-shaped illumination light beam LB having a shape LB1.

  The measurement light beam returning from the eyeball 17 is transmitted through the quarter-wave plate 15, the polarization plane of the forward path is rotated by 90 degrees, is transmitted as it is through the polarization selective diffraction element 32 </ b> A, and is propagated to the optical path separation position side.

  The polarization selective diffraction element 32A is “a diffraction element in which a part of the illumination light beam LA is diffracted, and the light returning from the eyeball 17 passes through the quarter-wave plate 15 and the polarization direction is orthogonal to the forward light”. For example, it is possible to use an element “a polarization selective type diffraction function is developed by superimposing a fine periodic structure shorter than the wavelength on the diffraction structure”.

The form of the diffraction grating itself is the same as that of the diffraction element shown in FIGS. 4B and 4C except that it has polarization selectivity, and the shape of the region where the diffraction grating is formed is These are set in the same manner as in the embodiment described above with reference to FIG.
Further, although not shown in FIG. 5, as in the embodiment of FIG. 3, the polarization selective diffraction element 32A and the quarter wavelength plate 15 are formed on the front and back of the same substrate, These can be integrated, and by doing so, the number of parts can be reduced and the weight can be reduced, the operation load of the displacement means 22 can be reduced, and the position of the condenser lens can be controlled more stably. .

FIG. 6 is a diagram for explaining “another embodiment” of the glucose concentration measuring apparatus.
In order to avoid confusion, parts that are not likely to be confused are given the same reference numerals as in FIG.

  In the embodiment shown in FIG. 6, instead of the light shielding plate 13 in the embodiment shown in FIG. 1, the light beam cross-sectional shape of the illumination light beam LA converted into a parallel light beam by the collimator lens 12 is used as the ring-shaped light beam forming means 33. A first optical element 33A that converts the light into the ring-shaped divergent light and a second optical element 33B that converts the light beam converted into the ring-shaped divergent light into a parallel light beam having a ring-shaped light beam cross section. There is one end of the feature in the point using what it has.

  The first and second optical elements 33 </ b> A and 33 </ b> B are “axicon lenses” and have conical surfaces, the tops of the conical surfaces are opposed to each other, and each conical axis is the optical axis of the collimating lens 12. It is arranged to match.

  As shown in FIG. 6B, the illumination light beam LA is converted into a divergent light beam that diverges around the optical axis by the first optical element 33A, enters the second optical element 33B, and is again a parallel light beam. Into a ring-shaped illumination light beam LB.

  At this time, the inner diameter of the ring-shaped illumination light beam LB can be adjusted by adjusting the distance between the first and second optical elements 33A and 33b. By this adjustment, the inner diameter of the ring-shaped illumination light beam LB can be adjusted as shown in FIG. It can be set in the same manner as in the case of the form.

  Since the ring-shaped light beam forming means 33 does not have a function of regulating the outer peripheral portion of the ring-shaped illumination light beam LB, in the embodiment of FIG. 6, it has a “hollow ring-shaped light shielding portion” on one side of the transparent parallel plate. An aperture limiting element 35 is provided to form a light beam outer peripheral portion of the ring-shaped illumination light beam LB formed by the ring-shaped light beam forming means 33 so that the “ring width” of the light beam cross section of the ring-shaped illumination light beam LB is set to a desired size. Set.

  As the axicon lenses 33A and 33B, “Fresnel axicon lenses in which a conical shape is formed into Fresnel” may be used. Further, the aperture limiting element 35 may be formed as an opening in the housing HS, or may be formed by coating the lens surface of the condenser lens 16.

  By using each embodiment of the glucose concentration measuring device described above, the glucose concentration measuring method according to claim 12 is performed.

  In each of the embodiments described above, the “inner diameter” in the ring-shaped cross-sectional shape of the ring-shaped illumination light beam is restricted and the outer diameter is also restricted. The glucose measuring device of the present invention is to reduce or prevent the influence of noise light by “making the inner diameter of the ring irradiated with noise light larger than the opening diameter of the pinhole”. There is no need to regulate.

  However, if the outer diameter of the ring-shaped illumination light beam is not restricted, the beam waist diameter formed by the measurement light beam at the pinhole position becomes smaller and the pinhole plate setting accuracy becomes stricter. It is preferable to regulate the above.

In each embodiment described above, the external light cut filter 21 is used.
The external light cut filter 21 is a band-pass filter that transmits light having the wavelength of the laser light emitted from the illumination light source 11 and reflects light from outside the glucose concentration measuring apparatus.

  For example, when an illumination light source that emits light having a wavelength of λ1 (for example, 850 nm) in the near-infrared region, for example, in the range of 900 to 1400 nm, is used as the wavelength band of the laser light, the light in this wavelength region is transmitted and “visible wavelength region A band pass filter having spectral transmittance characteristics as shown in FIG. 7 may be used so as to reflect (400 to 800 nm).

  As a band-pass filter that exhibits such characteristics, a filter in which a multilayer film is formed by vacuum deposition or sputtering, or a filter in which a concavo-convex shape having a period equal to or less than a wavelength is formed can be used.

  Further, in order to prevent the return light to the semiconductor laser used as the illumination light source 11, “the laser light toward the eyeball 17 is transmitted as it is” in the optical path between the laser light source 11 and the polarization beam splitter 14. It is preferable to arrange “an element that prevents the light in the polarization direction perpendicular to the light source 11 from returning to the illumination light source 11 by any means of reflection, diffraction, and scattering”. In this way, the laser oscillation of the illumination light source can be stabilized.

  A “ND filter for reducing the amount of light” may be disposed in the optical path between the illumination light source 11 and the external light cut filter 21. As a result, “the intensity of the ring-shaped illumination light beam incident on the eyeball 17 is set to a predetermined value (MPE value that is allowed to enter the eye (JIS C-6802: 1/10 of the level at which the failure rate due to laser radiation is 50%). The intensity of the ring-shaped illumination light beam can be regulated to a value lower than the value that defines the laser light intensity.

  It should be noted that the ND filter is preferably disposed in the optical path between the laser light source 11 and the polarization beam splitter 14 in order to obtain the measurement light beam reflected from the eyeball 17 with high efficiency.

  The ND filter may be formed by coating the surface of “any optical element” disposed on the optical path from the illumination light source 11 to the external light cut filter 21. In this way, the ND function can be added without increasing the number of parts.

When a semiconductor laser is used as the illumination optical system 11, the far field pattern of the laser light emitted from the semiconductor laser is elliptical.
Since the ring-shaped illumination light beam LB has an annular cross-sectional shape, in order to obtain such a light beam cross-sectional shape from an elliptical light beam cross-section, the NA of the collimating lens 12 is increased to obtain a large-area elliptical light beam cross-section. The annular light beam section may be cut out by the ring-shaped light beam forming means, but the light utilization efficiency is poor and the collimating lens is likely to be enlarged.

  In order to avoid this, a “beam shaping unit” may be provided between the collimating lens 12 and the polarization beam splitter 14 to shape the beam cross-sectional shape from an elliptical shape to a circular shape.

  For example, as shown in FIG. 8A, the beam shaping means transmits a “laser beam having an elliptical incident beam cross section” and a “laser beam having a circular emission side beam cross section” via a wedge-shaped prism PL. Or a diffraction element RL having two diffractive surfaces extending in one direction (vertical direction in the figure) shown in FIG. 8B, or shown in FIG. 8C. In this manner, a combination of the concave cylinder lens L1 and the convex cylinder lens L2 coaxially may be used.

  In the above-described embodiment, the polarization beam splitter 14 that transmits and reflects the laser light according to the polarization direction of the laser light emitted from the illumination light source 11 is used. Other optical elements may be used as long as they are optical elements that can guide light to the eyeball 17 and guide reflected light from the eyeball 17 to the photodetector 20.

  For example, instead of the polarization beam splitter 14, a half mirror that transmits half of incident light and reflects half of the incident light may be used.

A “means for correcting spherical aberration” may be disposed in the optical path from the illumination light source 11 to the condenser lens 16.
Generally, the “condensing lens is designed to condense a parallel light beam at a specific position in the eyeball”.

Then, spherical aberration occurs at a position deviated from the condensing position.
Therefore, by providing spherical aberration correcting means for generating spherical aberration that cancels the spherical aberration generated on the condensing spot according to the lens position of the condensing lens, each surface to be condensed (the aforementioned surfaces R1 to R4) is provided. It becomes possible to form a good condensing spot.

  As spherical aberration correcting means, a method of changing the position of the collimating lens 12 in the optical axis direction to change the divergence state of the light incident on the condenser lens 16, or 2 comprising a concave lens L 10 and a convex lens L 11 as shown in FIG. A method of changing the interval between the group lenses to change the divergence state of the ring-shaped illumination light beam incident on the condenser lens 16 or a liquid crystal capable of adding a predetermined spherical aberration to the passing beam by generating an optical path difference according to the pupil radial position. An element or the like can be used.

  In addition, a deflection mirror can be arranged in the optical path from the illumination light source 11 to the external light cut filter 21 so that the optical path can be appropriately bent. For example, as shown in FIG. 10, a reflection prism or the like in which the external light cut filter 21 and the deflection mirror ML are integrated may be configured.

FIG. 11 is an explanatory view showing an example of the appearance and usage of the glucose concentration measuring apparatus.
An external light cut filter 21 is disposed on the front surface of the apparatus main body indicated by reference numeral 100 in FIG.

  Since the external light cut filter 21 has spectral transmittance characteristics as shown in FIG. 7 and reflects light in the visible region (external light), it can be used as a mirror.

  An alignment mark ALM is formed on the external light cut filter 21 as shown in FIG. 11C, and when the alignment mark ALM is visually observed as shown in FIG. The image of The measurer can adjust the position of the eyeball 17 by adjusting the position of the eyeball 17 that moves to the external light cut filter 21 with respect to the alignment mark ALM.

  FIG. 11D shows a state in which the pupil of the eyeball 17 is correctly positioned on the optical axis of the condenser lens 16 of the glucose concentration measuring apparatus but is not in an appropriate position on the optical axis. This is known that the size of the “image 17I by the external light cut filter 21” of the pupil is smaller than the “circular mark of the alignment mark ALM”.

  Accordingly, with the center of the pupil image 17I aligned with the center of the alignment mark ALM, the position of the eyeball 17 and the apparatus main body is adjusted in the direction of the optical axis of the condenser lens, as shown in FIG. An appropriate measurement state is realized in a state where the center of the pupil image 17I coincides with the center of the alignment mark ALM and the size of the pupil image 17I matches the size of the circular mark of the alignment mark ALM. Thus, the three-dimensional alignment of the eyeball with respect to the glucose concentration measuring device can be easily performed while viewing the alignment mark ALM.

In the above, the case of measurement with the naked eye has been described, but the glucose concentration measurement method of the present invention can be applied to a “measurer wearing a contact lens”.
When a contact lens is used, the surface of the cornea and the back surface of the contact lens are in contact with each other, and the surface of the contact lens is in contact with air.

  Accordingly, the glucose concentration measuring device is provided with a “switch function that can select whether or not a contact lens is attached”, and a photodetector 20 for obtaining “an anterior chamber refractive index” according to an input signal from the switch. “3rd and 4th” are selected as output peaks.

  That is, since the output of the photodetector 20 has five peaks, the “third and fourth peak intervals are the optical path length of the anterior chamber”. Since spherical aberration occurs at this time, the above-described aberration correcting means may be changed to a predetermined state in accordance with an external input signal. It is also possible to configure a glucose concentration measuring device dedicated to contact lenses on the premise of the output of five reflection peaks without providing an external input device.

It is a figure for demonstrating a glucose concentration measuring apparatus . It is a figure for demonstrating the characterizing part of invention. It is a figure for demonstrating one Embodiment of the glucose concentration measuring apparatus. It is a figure for demonstrating the other example of a glucose concentration measuring apparatus. It is a figure for demonstrating the other form of implementation of the glucose concentration measuring apparatus. It is a figure for demonstrating the other form of implementation of the glucose concentration measuring apparatus. It is a figure for demonstrating an external light cut filter. It is a figure for demonstrating a beam shaping means. It is a figure for demonstrating an aberration correction means. It is a figure for demonstrating an example in the case of making an optical path bend using a deflection | deviation mirror. It is a figure for demonstrating the external shape and use condition of a glucose concentration measuring apparatus.

Explanation of symbols

11 Illumination light source
12 Collimating lens
14 Polarizing beam splitter
15 1/4 wave plate
16 Condensing lens
17 Eyeball
18 Detection lens
19 Pinhole plate
20 Photodetector
22 Displacement device

Claims (9)

The optical thickness of the anterior chamber in the eyeball is detected by an optical method, the refractive index of the medium in the anterior chamber is calculated based on the detected optical thickness, and the calculated refractive index is used. A glucose concentration measuring device that calculates and calculates the glucose concentration of the anterior chamber medium based on a correspondence relationship between the refractive index and the glucose concentration set in advance;
An optical device that optically detects the optical thickness of the anterior chamber of the eyeball, and calculates the refractive index of the anterior chamber medium based on the optical thickness detected by the optical device, and the calculated refraction Calculating means for calculating the glucose concentration of the anterior chamber medium corresponding to the rate,
The optical device comprises:
A light source for illumination, and a collimating lens for collimating the laser light beam emitted from the light source for illumination;
A condensing lens that converts the illumination light beam converted into a parallel light beam by the collimator lens into a condensing light beam that converges toward the eyeball;
A photodetector for receiving a measurement light beam returning from the eyeball via the condenser lens and converting it into an electrical signal;
An optical path separating means for separating the measurement light beam from the light path of the illumination light beam toward the photodetector;
A detection lens for condensing the measurement light beam separated by the optical path separating means toward the vicinity of the light receiving surface of the photodetector;
The image point position with respect to the object point by the condenser lens and the detection lens, when the condenser lens and the detection lens are arranged at a predetermined position in the vicinity of the light receiving surface of the photodetector, A pinhole plate having a pinhole with a predetermined opening diameter;
Condensing position displacing means for displacing the condensing position of the light beam for illumination by the condensing lens in the optical axis direction of the condensing lens;
Forming a ring-shaped light beam that is arranged on the optical path between the collimating lens and the condenser lens, and that shapes the cross-sectional shape of the illumination light beam converted into a parallel light beam by the collimating lens into a ring shape to form a ring-shaped illumination light beam Means,
The arithmetic means can set anterior chamber basic data and data about the correspondence between the refractive index of the medium in the anterior chamber and the glucose concentration, and the illumination light beam is an anterior boundary surface of the anterior chamber. And calculating the refractive index of the anterior chamber medium based on the optical thickness of the anterior chamber detected as the amount of displacement of the condensing position when condensing on the posterior boundary surface. Having the function of calculating the glucose concentration of the anterior chamber medium based on the refractive index;
The ring-shaped light beam forming means has an inner diameter of a ring image formed on the pinhole plate by the return light reflected by the other boundary surface when the measurement light beam is condensed on one boundary surface of the eyeball. It has a function of regulating the inner diameter of the ring-shaped illumination light beam so as to be equal to or larger than the opening diameter of the pinhole ,
Having a quarter-wave plate between the condensing lens and the optical path separating position of the optical path separating means;
Between the optical path separation position and the quarter-wave plate, a ring-shaped light beam forming means is disposed,
The ring-shaped light beam forming means shields at least the light beam central portion of the illumination light beam that has been collimated by the collimator lens, and returns the measurement light beam that returns from the eyeball through the condenser lens and the quarter-wave plate. A glucose concentration measuring apparatus, which is a polarization-selective light-shielding plate that transmits light toward the optical path separation position . The optical thickness of the anterior chamber in the eyeball is detected by an optical method, the refractive index of the medium in the anterior chamber is calculated based on the detected optical thickness, and the calculated refractive index is used. A glucose concentration measuring device that calculates and calculates the glucose concentration of the anterior chamber medium based on the correspondence between the refractive index and the glucose concentration set in advance,
An optical device that optically detects the optical thickness of the anterior chamber of the eyeball, and calculates the refractive index of the anterior chamber medium based on the optical thickness detected by the optical device, and the calculated refraction Calculating means for calculating the glucose concentration of the anterior chamber medium corresponding to the rate,
The optical device comprises:
A light source for illumination, and a collimating lens for collimating the laser light beam emitted from the light source for illumination;
A condensing lens that converts the illumination light beam converted into a parallel light beam by the collimator lens into a condensing light beam that converges toward the eyeball;
A photodetector for receiving a measurement light beam returning from the eyeball via the condenser lens and converting it into an electrical signal;
An optical path separating means for separating the measurement light beam from the light path of the illumination light beam toward the photodetector;
A detection lens for condensing the measurement light beam separated by the optical path separating means toward the vicinity of the light receiving surface of the photodetector;
The image point position with respect to the object point by the condenser lens and the detection lens, when the condenser lens and the detection lens are arranged at a predetermined position in the vicinity of the light receiving surface of the photodetector, A pinhole plate having a pinhole with a predetermined opening diameter;
Condensing position displacing means for displacing the condensing position of the light beam for illumination by the condensing lens in the optical axis direction of the condensing lens;
Forming a ring-shaped light beam that is arranged on the optical path between the collimating lens and the condenser lens, and that shapes the cross-sectional shape of the illumination light beam converted into a parallel light beam by the collimating lens into a ring shape to form a ring-shaped illumination light beam Means,
The arithmetic means can set anterior chamber basic data and data about the correspondence between the refractive index of the medium in the anterior chamber and the glucose concentration, and the illumination light beam is an anterior boundary surface of the anterior chamber. And calculating the refractive index of the anterior chamber medium based on the optical thickness of the anterior chamber detected as the amount of displacement of the condensing position when condensing on the posterior boundary surface. Having the function of calculating the glucose concentration of the anterior chamber medium based on the refractive index;
The ring-shaped light beam forming means has an inner diameter of a ring image formed on the pinhole plate by the return light reflected by the other boundary surface when the measurement light beam is condensed on one boundary surface of the eyeball. It has a function of regulating the inner diameter of the ring-shaped illumination light beam so as to be equal to or larger than the opening diameter of the pinhole,
Having a quarter-wave plate between the condenser lens and the optical path separating position of the optical path separating means;
A ring-shaped light beam forming means is disposed between the optical path separation position and the quarter-wave plate,
The ring-shaped light beam forming means diffracts and removes at least the light beam central portion of the illumination light beam converted into a parallel light beam by the collimating lens from the illumination light beam, and removes the condenser lens and the quarter-wave plate from the eyeball. A glucose concentration measuring device, which is a polarization-selective diffractive element that transmits the measurement light beam returned through the optical path as it is toward the optical path separation position . The optical thickness of the anterior chamber in the eyeball is detected by an optical method, the refractive index of the medium in the anterior chamber is calculated based on the detected optical thickness, and the calculated refractive index is used. A glucose concentration measuring device that calculates and calculates the glucose concentration of the anterior chamber medium based on the correspondence between the refractive index and the glucose concentration set in advance,
An optical device that optically detects the optical thickness of the anterior chamber of the eyeball, and calculates the refractive index of the anterior chamber medium based on the optical thickness detected by the optical device, and the calculated refraction Calculating means for calculating the glucose concentration of the anterior chamber medium corresponding to the rate,
The optical device comprises:
A light source for illumination, and a collimating lens for collimating the laser light beam emitted from the light source for illumination;
A condensing lens that converts the illumination light beam converted into a parallel light beam by the collimator lens into a condensing light beam that converges toward the eyeball;
A photodetector for receiving a measurement light beam returning from the eyeball via the condenser lens and converting it into an electrical signal;
An optical path separating means for separating the measurement light beam from the light path of the illumination light beam toward the photodetector;
A detection lens for condensing the measurement light beam separated by the optical path separating means toward the vicinity of the light receiving surface of the photodetector;
The image point position with respect to the object point by the condenser lens and the detection lens, when the condenser lens and the detection lens are arranged at a predetermined position in the vicinity of the light receiving surface of the photodetector, A pinhole plate having a pinhole with a predetermined opening diameter;
Condensing position displacing means for displacing the condensing position of the light beam for illumination by the condensing lens in the optical axis direction of the condensing lens;
Forming a ring-shaped light beam that is arranged on the optical path between the collimating lens and the condenser lens, and that shapes the cross-sectional shape of the illumination light beam converted into a parallel light beam by the collimating lens into a ring shape to form a ring-shaped illumination light beam Means,
The arithmetic means can set anterior chamber basic data and data about the correspondence between the refractive index of the medium in the anterior chamber and the glucose concentration, and the illumination light beam is an anterior boundary surface of the anterior chamber. And calculating the refractive index of the anterior chamber medium based on the optical thickness of the anterior chamber detected as the amount of displacement of the condensing position when condensing on the posterior boundary surface. Having the function of calculating the glucose concentration of the anterior chamber medium based on the refractive index;
The ring-shaped light beam forming means has an inner diameter of a ring image formed on the pinhole plate by the return light reflected by the other boundary surface when the measurement light beam is condensed on one boundary surface of the eyeball. It has a function of regulating the inner diameter of the ring-shaped illumination light beam so as to be equal to or larger than the opening diameter of the pinhole,
The ring-shaped light beam forming means converts a light beam cross-sectional shape of the illumination light beam converted into a parallel light beam by a collimating lens into a ring-shaped divergent light, and a light beam converted into the ring-shaped divergent light And a second optical element that converts the light into a parallel light beam having a ring-shaped light beam cross section . In the glucose concentration measuring apparatus according to any one of claims 1 to 3,
The glucose concentration measuring device, wherein the condensing position displacing means is a lens displacing device that displaces the condensing lens in the optical axis direction . In the glucose concentration measuring apparatus according to any one of claims 1 to 4,
  An apparatus for measuring glucose concentration, comprising: a band-pass filter that transmits light having a wavelength of an illumination light beam on an eyeball side of a condenser lens. The glucose concentration measuring device according to claim 5, wherein
  A glucose concentration measuring apparatus, wherein either the illumination light source or the bandpass filter includes a deflection mirror that deflects the optical path. The optical apparatus used for the glucose concentration measuring apparatus of any one of Claims 1-6. A ring-shaped light beam forming device used as a ring-shaped light beam forming unit in the glucose concentration measuring device according to any one of claims 1 to 6. A glucose concentration measuring method using the glucose concentration measuring device according to any one of claims 1 to 6.

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