Patent Application
20080068592
The present invention relates to an optical element for measuring biological information used for noninvasive measurement of glucose, cholesterol, urea, or triglycerides in a body fluid by optically measuring biological tissue, and to a biological information measuring device using the optical element.
Conventionally, there has been proposed a method for measuring biological information by using an optical element comprising a recess portion to be brought into contact with an organism surface (for example, Patent Document 1). The biological information measuring device disclosed in Patent Document 1 comprises, as shown in
When using this biological information measuring device, the surface of the contact element for detecting biological information is brought into contact with the surface of the biological tissue 66, and light from the light source 11 is allowed to enter into the biological tissue 66 that is in contact with the above-mentioned recess portions 621, 622, 623, 624, and 625 from the contact element for detecting biological information, while the above-mentioned projecting portions 631, 632, 633, 634, 635, and 636 are pressed into the biological tissue 66.
After propagating into the biological tissue 66, the light enters the contact element for detecting biological information, and is detected by the light detector 16 after exiting from the contact element for detecting biological information. By adjusting the depth of the recess portions 621, 622, 623, 624, and 625, the depth of the biological tissue 66 to be a target of the measurement can be controlled, and optical characteristics of a specific layer can be determined.
Patent Document 1: International Publication No. 01/58355
However, the conventional optical measuring method and optical measuring device as mentioned in the above had the following problems. In the above conventional method, for example, information at different depths is measured by forming the recess portion 622 deeper than the recess portion 623 at another position, among the plurality of recess portions 621, 622, 623, 624, and 625, and projecting portions 631, 632, 633, 634, 635, and 636. However, since a single contact element for detecting biological information was used, it was difficult to separate the light that passed through the recess portion 622 and the light that passed through the recess portion 623, and there was a possibility of interference between the both signals.
Thus, in view of the above situations, the present invention aims to provide an optical element for measuring biological information and a biological information measuring device, which can reduce interference between a plurality of signals based on lights that passed through different depths in an organism, and can measure a plurality of optical parameters related to biological information with high precision.
To solve the above problems, the present invention provides an optical element for measuring biological information, in which information of an organism is measured by applying light to the organism and using light returned from a biological tissue of the organism, the optical element comprising:
a first light-transmitting body comprising a first groove portion which is to be brought into contact with the organism and which applies light to the organism and receives light;
a second light-transmitting body comprising a second groove portion which is to be brought into contact with the organism and which applies light to the organism and receives light, the second groove portion being deeper than the first groove portion.
The optical element for measuring biological information in the present invention may include a plurality of first light-transmitting bodies, and may include a plurality of second light-transmitting bodies. And any of the first light-transmitting body and the second light-transmitting body may be included in plural number.
The first light-transmitting body may include a single first groove portion, or a plurality of first groove portions. Similarly, the second light-transmitting body may include a single second groove portion, or a plurality of second groove portions.
Also, the present invention provides a method for measuring biological information by using an optical element for measuring biological information comprising:
a first light-transmitting body comprising a first groove portion which is to be brought into contact with an organism and which applies light to the organism and receives light; and
a second light-transmitting body comprising a second groove portion which is to be brought into contact with the organism and which applies light to the organism and receives light, the second groove portion being deeper than the first groove portion,
the method comprising the steps of:
applying light to an organism contacting the optical element for measuring biological information;
detecting an intensity of light returned from the organism to the first groove portion;
detecting an intensity of light returned from the organism to the second groove portion; and
obtaining biological information in a dermis layer of the organism based on a difference of the detected intensity of light returned to the second groove portion and intensity of light returned to the first groove portion.
Further, the present invention provides a biological information measuring device comprising: a light source; the optical element for measuring biological information in the above; a light detector for detecting light exited the optical element; and a computing unit for calculating biological information by arithmetically processing information obtained by the light detector.
The present invention reduces the interference between a plurality of signals based on lights that passed through different depths in an organism, and can measure a plurality of optical parameters related to biological information with high precision.
An optical element for measuring biological information of the present invention comprises a first light-transmitting body including a first groove portion to be brought into contact with an organism and to emit light to the organism and receive light, and a second light-transmitting body including a second groove portion to be brought into contact with an organism and to emit light to the organism and receive light, the second groove portion being deeper than the first groove portion.
Based on such a structure, with a simple structure comprising at least two light-transmitting bodies that are different from each other, interference between a plurality of signals based on lights that passed through different depths in an organism can be reduced, and a plurality of optical parameters related to biological information can be measured with high precision.
Between the at least two light-transmitting bodies, a light-shielding body that absorbs or reflects the light is preferably provided. Based on such a structure, since the light-shielding body prevents the light that passes through the light-transmitting body from entering adjacent light-transmitting bodies, the possibility of interference between the signal detected in the light-transmitting body and other signals is eliminated, enabling a further accurate measurement.
Also, the first light-transmitting body, the second light-transmitting body, and the light-shielding body are preferably stacked so that the light-shielding body is interposed between the first light-transmitting body and the second light-transmitting body.
In the above element for measuring biological information, a groove portion for applying light to the organism and receiving the light that passed through the tissue is preferably provided at least one of the organism contacting portions, among the organism contacting portion of the first light-transmitting body and the organism contacting portion of the second light-transmitting body.
Based on such a structure, especially on the groove portion, light can be applied to a specific portion of the biological tissue to obtain exit light, and measurement can be carried out for that specific portion.
The optical element for measuring biological information in the present invention may further comprise a light-transmitting body (third light-transmitting body) for measurement of a surface of an organism.
Based on such a structure, homogeneity of the organism and surface conditions of the optical element can be evaluated further in detail, enabling detection of measurement errors and achieving measurement with further precision.
The present invention also provides a biological information measuring device comprising a light source; the optical element for measuring biological information mentioned above; a light detector for detecting light exited the optical element; and a computing unit for arithmetically processing information obtained by the light detector to calculate biological information.
Based on the biological information measuring device of the present invention, a concentration of a target component in the biological tissue can be measured reliably and noninvasively.
In the following, an embodiment of the optical element for measuring biological information and the biological information measuring device in the present invention is described in detail by referring to the drawings. However, the following embodiments are examples, and the present invention are not limited to these examples.
In the description below, same reference numerals are used for the same or corresponding part, and repetitive descriptions may be omitted.
The positional relationship between the light separating means 14 and the spectroscopic means 15 is not limited to the position shown in
For the light source 11, a light source that can emit light including a light component of a wavelength that can be absorbed by the measurement target (substance) in the biological tissue will suffice. For the light source emitting light of the mid-infrared range, for example, a Globar light source which is SiC sintered into a rod, a CO2 laser, a tungsten lamp, an infrared pulse light source, and a quantum cascade laser (QCL) light source may be used.
When a substance having a strong absorption peak in the mid-infrared region such as in the proximity of wave numbers of 1033 cm−1 and 1080 cm−1, such as glucose, without particular limitation, a Globar light source, an infrared pulse light source, and a QCL light source are preferable. When a substance having an absorption in the near-infrared range is to be measured, for example, a halogen light source, a semiconductor laser, and an LED are preferably used. Glucose is known to have an absorption peak in the near-infrared range in addition to the mid-infrared range: therefore, especially an LED is preferably used.
For the material forming the optical lens 12 and the light-transmitting body 17, known ones in the art may be used. For example, when a substance having an absorption in the mid-infrared range is to be measured, silicon, germanium, SiC, diamond, ZnSe, ZnS, and KrS may be used.
When a substance having an absorption peak in the mid-infrared range, i.e., a wave number of 1033 cm−1 or 1080 cm−1, such as glucose is to be measured, silicon or germanium is particularly preferable, in view of high transmission of an infrared wavelength of about 9 to 10 microns, and also workability and high mechanical strength. When a substance having an absorption in the near-infrared range, fused quartz, single crystal silicon, optical glass, and plastic are preferably used.
The optical element 13 for measuring biological information in this embodiment comprise a first light-transmitting body 17a and two second light-transmitting bodies 17b disposed to sandwich the first light-transmitting body. The first light-transmitting body 17a and the second light-transmitting body 17b comprises a first groove portion 18a and a second groove portion 18b, respectively. The second groove portion 18b is formed deeper than the first groove portion 18a.
With regard to the shape of the first groove portion 18a and the second groove portion 18b, in view of ease in its production, for example, V-shaped grooves as shown in
The first groove portion 18a and the second groove portion 18b may be formed by using known production technique.
For example, when a crystal of silicon or germanium is to be used as a material forming the first light-transmitting body 17a and the second light-transmitting body 18b, the first groove portion 18a and the second groove portion 18b may be formed by using an anisotropic etching technique.
When resin is used as a material forming the first light-transmitting body 17a and the second light-transmitting body 18b, the first groove portion 18a and the second groove portion 18b may be formed simultaneously with the formation of the first light-transmitting body 17a and the second light-transmitting body 18b by using a molding method.
The first light-transmitting body 17a in
Generally, accurate measurement may be difficult when sweat, soil, saliva, and the like are present in a large quantity between the organism and the measurement part, and also when the amount and quality of these change at every measurement time.
Thus, in this embodiment, second groove portions 18b are preferably provided. Presence of sweat, soil, and saliva, that are present in many cases at a skin surface, in the range of about several tens of micrometer, can thus be grasped. The depth of the groove in the second groove portion 18b is preferably several tens of micrometers or more. By using such grooves, soil on the skin, contact on the skin, and homogeneity of skin surface conditions can be easily detected. By using the detection result to detect an error, highly precise measurement can be achieved.
That is, an abnormality can be determined by measuring the spectrum of returning light from the second groove portion 18b, calculating the absorbance of a specific wavelength, and determining deviation from the standard value. For example, when sweat and saliva are present in quantity on the surface layer, it can be determined since the absorbance will be almost the same with water.
When the detection result showed a similar absorbance with water, it is preferable to stop the measurement, and wipe off the soil such as water from the skin surface, because an accurate measurement is difficult.
The abnormality in the contact with the skin and homogeneity in skin surface conditions is preferably detected by providing two second light-transmitting bodies 17b to provide two second groove portions 18b.
That is, when the signals from the two second groove portions 18b are compared and found to be greatly different, surface conditions of the skin may not be homogenous, or there may be a problem in the contacting conditions, and it is preferable to stop the measurement and wipe off the soil on the biological tissue surface. Also, even when the signals from the two second groove portions 18b are equal, if the signal shows that excessive soil on the surface layer is included, it is preferable to stop the measurement and wipe off the soil on the skin surface. The soil includes oil, other than water.
When the signals from the two second groove portions 18b are appropriate and almost equal, it is determined that the conditions of the organism surface are homogenous, and that contacting conditions are appropriate. Thus, when such determination is made, the measurement is started, and biological information is measured by the first groove portion 18a of the first light-transmitting body 17a disposed between the two second light-transmitting bodies 17b.
By thus evaluating the surface conditions of the optical element and its homogeneity with the two second groove portions 18b, further accurate measurement is achieved compared with the case in which only the light-transmitting body is used.
A space may be provided between the first light-transmitting body 17a and the second light-transmitting body 17b, for example, by interposing a spacer. Based on such a structure, light is reflected by the difference in the refractive index of air existing in the space, and the refractive index of the light-transmitting body, generating light-shielding effects.
For the light separating means 14, a known one in the art may be used without any particular limitation, as long as it separates the light that measured the respective depths, and allows the light to enter the spectroscopic means 15 and the light detecting means 16. For example, a mechanical chopper, a filter, and an acousto-optic modulator may be used.
The spectroscopic means 15, though not shown in
For the light detecting means 16, known ones in the art may be used. For example, for the mid-infrared range, a pyroelectric sensor, a thermopile, a thermistor, and an MCT detector (HgCdTe detector, a kind of quantum detector) may be mentioned. For the near-infrared range, an InGaAs detector, a photodiode, a PbS detector, an InSb detector, and an InAs detector may be mentioned.
Though not shown, by carrying out calculation with a computing means such as a computer based on the signal detected by the light detecting means 16, for example, parameters of the biological tissue such as a glucose concentration can be calculated.
An operation of the biological information measuring device 100 in this embodiment is described by using
As shown in
The thickness of the horny layer 21 varies depending on the part of the organism. For example, in the case of cheeks, the thickness of the horny layer 21 is 0.01 to 0.02 mm, the thickness of the prickly layer 22 is 0.08 to 0.28 mm, and the thickness of the dermis 25 is 2 to 3 mm.
That is, when light 31 is allowed to enter the organism through the groove portion 18, the light 31 is refracted at an interface between the horny layer 21 and the groove portion 18, and enters the horny layer 21 at a certain angle. The light being allowed to enter travels in straight lines in the organism, and after penetrating the prickly layer 22, the light 31 is refracted at an interface between the horny layer 21 and the groove portion 18 again, to reach the groove portion 18.
To refract the light 31 at the interface between the groove portion 18 and the horny layer 21 as shown in
Although the shape and the size of the groove portion 18 are not particularly limited, for example, the V-shaped groove portion as shown in the above may be used.
For light used for the measurement, for example, light in the near-infrared range with a wavelength of 1.2 μm or more and 2.5 μm or less, and in the mid-infrared range with a wavelength of 2.5 to 10 μm may be used.
Among these, the mid-infrared range is preferable in that an absorption inherent to a substance exists in the range and any component can be easily identified. Since light in the mid-infrared range is largely absorbed by an organism, the depth of penetration into an organism is about 200 μm. On the other hand, light in the near-infrared range is less absorbed by the organism, and measurement is possible even at a depth of 200 μm or more.
For the biological tissue measured by the optical element for measuring biological information and the biological information measuring device in the present invention, those parts where epidermis is present, such as an inner side of a forearm, earlobe, lip mucosa, finger, and upper arm of humans may be mentioned.
For example, lips do not include the horny layer and the dermis, and the epidermis layer has a thickness of 50 to 200 μm. Thus, when an organism component in the epidermis layer of the lips, for example a concentration of glucose, is to be measured, light in the mid-infrared range may be used. At this time, both of the shallow groove portion and the deep groove portion can be set to a depth of 200 μm or less.
Based on such, by deducting the transmission data obtained by the shallow groove from the transmission data obtained by the deep groove (that is, measurement data obtained from the transmitted light), effects from sweat, soil, and saliva present in organism surface may be restrained.
For the material of the light-transmitting body 17, for example, silicon that is transparent in the mid-infrared range is used. When silicon is used, by applying an anisotropic etching process, a known techniques in silicon crystal, the V-shape groove may be achieved easily.
For example, any of a vertex angle 33 of the groove portion 18 is processed to give 70.6°. Also, by selecting crystal processed surface of silicon, the vertex angle 33 may be processed to give 117°.
The present invention does not particularly limit the vertex angle 33 of the groove portion 18, but depending on the thickness and hardness of the epidermis of the biological tissue to be measured, it may be selected appropriately.
Also, when the measurement is to be carried out at a finger cushion, the thickness of the horny layer is about 200 μm, the thickness of the epidermis layer is about 240 μm, and the thickness of the total of the horny layer, the epidermis layer, and the dermis layer is about 2 mm. Thus, when the depths of both the shallow groove portion and the deep groove portion are set to 440 μm to 2 mm, by deducting the transmission data obtained by the shallow grooves from the transmission data obtained by the deep grooves, a component of an organism in the dermis layer can be measured, removing the effects from the horny layer and the epidermis layer.
Especially when the component of the organism is glucose, it is preferable since dermis includes glucose in quantity. For the light to be used for the measurement at this time, it is preferable to use the light in the near-infrared range with less absorption by the organism.
Silicon may be used for the material of the light-transmitting body 17, as in the case of the mid-infrared range, but it is not limited thereto and glass and resin may be used as well.
Thus, a relatively shallow portion of the biological tissue can be measured by the groove portion 18 (a shallow first groove portion 18a) in
Further, as shown in for example
As shown in FIGS. 3 to 5, light that passes through the biological tissue via the groove portion 18 and returned again exits the light-transmitting body 17 and then reaches the light separating means 14, as shown in
That is, by setting the light separating means 14 so that the opening portion 42 is aligned with any of the plurality of light-transmitting bodies 17, only the light exited the light-transmitting body 17 can be allowed to pass through. Thus, by separating the organism signal from the groove portion 18 provided in the light-transmitting body 17 and the signal from the other groove portion 10 provided in the light-transmitting body 17, the detection can be carried out with high sensitivity individually.
Additionally, although the spectroscopic means 15 shown in
The width of the opening portion 42 of the light separating means 14 is preferably the width that can receive the light exited the light-transmitting body 17 provided at the biological information measuring device 100. Without particular limitation, similarly with the thickness of the light-transmitting body 17 of the biological information measuring device 100, the same width is preferable.
The position of the light separating means 14 at the time of the measurement is preferably decided in correspondence to the light-transmitting body 17.
Although not shown, the light separating means 14 is preferably moved in correspondence to for example the transmitting body 17 as shown in
The light spectroscopically analyzed with the spectroscopic means 15 enters the light detecting means 16, and the absorbance is calculated based on the intensity of light.
Also, although not shown, the obtained absorbance is used to calculate by using the computing means, to calculate a glucose concentration in the body fluid. In the present invention, since the measurement can be carried out for both the information on the shallow surface layer tissue and on the deeper tissue, an accurate glucose concentration can be calculated.
Light passing the first light-transmitting body 17a, the second light-transmitting body 17b, and the third light-transmitting body 17c in embodiment 1 as shown in
The light-shielding body 19 is preferably provided at a portion where the light of the first light-transmitting body 17a and the second light-transmitting body 17b do not transmit. For example, when any of the first light-transmitting body 17a and the second light-transmitting body 17b is included in a plural number, the light-shielding body 19 is preferably provided between adjacent light-transmitting bodies. Therefore, the optical element for measuring biological information in the present invention may include a plurality of light-shielding bodies 19.
For the material forming the light-shielding body 19, a material that absorbs or reflects light may be used. For example, metals that can shield the light to be used, such as aluminum, tungsten, molybdenum, chromium, and copper are preferable. Further, a thin film of these metals, or a multilayer film of these metal films and dielectric films may be preferably formed on a substrate by vapor deposition and sputtering for the usage. Also, metal foils such as aluminum foil may be used as the light-shielding body 19, and the metal foil may be sandwiched by the light-transmitting body and joined. The light-shielding body 19 may be a plate-like.
The advantages of the above light-shielding body 19 are described in further detail with reference to
The first light-transmitting body 17a, the two second light-transmitting bodies 17b and the two light-shielding bodies 19 are stacked. On the part of the first light-transmitting body 17a and the second light-transmitting body 17b where the organism is brought into contact, the first groove portion 18a and the second groove portion 18b are formed, respectively.
Based on such a structure, as can be seen in
Such light can be eliminated when the light exited the light source 11 is made a parallel beam completely, and when allowed to enter the first light-transmitting body 17a and the second light-transmitting body 17b absolutely straight. However, the light source itself is a luminous body with a diameter of about 1 mm or more in many cases, it is difficult to make a complete parallel beam, and to make such ideal conditions.
On the other hand, in this embodiment, when incident angle of the light reaching the boundary of the light-shielding body 19 is smaller than the angle of the total reflection, light exits the first light-transmitting body 17a and the second light-transmitting body 17b and reaches the light-shielding body 19.
When there is no light-shielding body 19, light re-enters the adjacent light-transmitting body, and interferes with the signal detected in the light-transmitting body, and as in the present invention, when the light-shielding body 19 that can sufficiently shield light is provided in the optical element 13 for measuring biological information, since light is mostly absorbed by or reflected at the light-shielding body 19, light does not enter the adjacent light-transmitting body 17. Therefore, light exited the light-transmitting body 17 and reflected at the light-shielding body 19 can return to the same light-transmitting body 17, increasing the amount of signal and is preferable.
Although a plate-like light-shielding body is described as a form of the light-shielding body 19, it is not limited thereto.
A metal film may be coated on the light-transmitting body surface by vapor deposition and sputtering, or a metal foil such as aluminum foil may be sandwiched between the light-transmitting bodies and joined. An adhesive layer may be provided for the joining.
Other structures may be the same with the above embodiment 1.
As a further simple structure of the optical element for measuring biological information in the present invention, the one shown in
In
Other structures may be the same with the above Embodiment 1 or Embodiment 2.
The biological tissue measured by the optical element for measuring biological information and the biological information measuring device in the present invention is not particularly limited, and where epidermis is present, such as inner side of frontal arm, earlobe, lip mucosa, finger, and upper arm of humans, will suffice.
The measurement target may be a substance that is optically measurable such as a body fluid, and a body fluid component other than glucose can also be measured.
The optical element for measuring biological information and the biological information measuring device in the present invention can carry out accurate measurement on the surface layer tissue and a layer deeper than the surface layer selectively, and can carry out accurate measurement of information on the body fluid components. Additionally, not only the biological tissue, but various liquid samples can be measured as well, and the present invention is especially useful for the measurement of body fluid components for medical purposes.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-329248 | Nov 2004 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP05/20442 | 11/8/2005 | WO | 1/16/2007 |
