Patent Application
20150196240
The present invention relates to a non-invasive living body measurement device that irradiates a finger of a subject with light and obtains transmitted light, captures an image of the finger by receiving the transmitted light with an imaging unit, and detects biological information regarding the subject by processing the obtained image.
A non-invasive living body measurement device is known in which a finger of a subject is irradiated with light, optical information is acquired by receiving transmitted light or reflected light therefrom with a light receiving unit, and biological information regarding the subject is obtained by analyzing the optical information (e.g., JP 2000-262496A). The noninvasive living body measurement apparatus disclosed in JP 2000-262496A includes a platform on which the finger of the subject is placed, a cover unit that covers the finger placed on the platform, two light source units attached to the cover unit, and an imaging unit. An image of the subject's finger is captured by an imaging unit receiving transmitted light that passes through the finger when light is emitted from the light source units, thus obtaining a transmission image of the subject's finger, and the hemoglobin concentration of the subject is detected by processing the image.
However, with the noninvasive living body measurement device disclosed in JP 2000-262496A, it has not been possible for the entirety of the subject's finger, which is the measurement target, to be uniformly irradiated with light from the light source units provided on the cover unit. For this reason, obtained images have locally dark and light portions, and have not been clear images.
The scope of the present invention is defined solely by the appended claims, and is not affected to any degree by the statements within this summary.
A first aspect of the present invention is a non-invasive living body measurement device includes: a platform for placement of a finger of a subject that is a measurement target; a plurality of light emitting units arranged in a line along a lengthwise direction of the finger placed on the platform; a light amount adjustment unit that adjusts a light amount of each of the plurality of light emitting units; an imaging unit that obtains an image of the finger placed on the platform by receiving transmitted light that passed through the finger when light was emitted from the light emitting units; and an information processing unit that detects biological information regarding the subject by processing the image obtained by the imaging unit, wherein the light amount adjustment unit is configured to set the light amount of a light emitting unit provided at a position closest to a joint of the finger placed on the platform lower than the light amount of other light emitting unit.
A second aspect of the present invention is a method of non-invasive living body measurement includes: (a) placing a finger of a subject that is a measurement target on a platform; (b) arranging a plurality of light emitting units in a line along a lengthwise direction of the finger placed on the platform; (c) adjusting a light amount of each of the plurality of light emitting units; (d) obtaining an image of the finger placed on the platform by receiving transmitted light that passed through the finger when light is emitted from the light emitting units; and (e) detecting a biological information regarding the subject by processing the obtained image, wherein the step (c) comprises lowering the light amount of the light emitting unit provided at a position closest to a joint of the finger placed on the platform than the light amount of other light emitting unit.
Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.
Configuration of Non-Invasive Living Body Measurement Device
The measurement unit 2 includes a platform 21 on which a finger 8 of the subject can be placed, and a cover unit 22 for covering the finger 8 placed on the platform 21. The cover unit 22 is arranged above the platform 21, and is pivotably attached to the platform 21. The cover unit 22 can open and close (cover the finger 8 and expose the finger 8) by swinging relative to the platform 21.
The subject's finger 8 can be placed on the platform 21 as described above. At this time, the subject's middle finger 8 is placed so as to be located directly above the imaging unit 4. Also, the platform 21 is formed so as to conform to the shape of the subject's middle finger 8, and is configured such that the second joint of the subject's middle finger 8 is located at the center of the imaging range of the imaging unit 4 when the subject's hand is placed over the platform 21.
When the subject's finger 8 is placed on the platform 21 and the cover unit 22 is closed, the light emitting apparatus 3 and the imaging unit 4 oppose each other so as to sandwich the subject's finger 8 from above and below. The light emitting apparatus 3 is configured so as to emit light downward, and the light emitted from the light emitting apparatus 3 passes through the subject's finger 8. This transmitted light passes through the lens system 41 and arrives at the imaging unit 4. In this way, a transmission image of the subject's finger 8 is obtained by the imaging unit 4.
The light amount adjustment unit 5 is constituted by an FPGA (Field-Programmable Gate Array). This light amount adjustment unit 5 receives an output signal from the imaging unit 4 and performs light amount adjustment on the light emitting apparatus 3 based on the output signal. The light amount adjustment performed on the light emitting apparatus 3 will be described in detail later.
As shown in
The information processing unit 7 has a CPU 71, a ROM 72, a RAM 73, an external storage apparatus 74, an input unit 75, a communication interface 76, and a display unit 77.
The CPU 71 executes computer programs stored in the ROM 72 and computer programs loaded to the RAM 73. The RAM 73 is used for the reading out of computer programs stored in the ROM 72 and the external storage apparatus 74. The RAM 73 is also used as a work area for the CPU 71 when these computer programs are executed.
The external storage apparatus 74 is constituted by a non-volatile storage device such as a hard disk or a flash memory. Various computer programs to be executed by the CPU 71, such as an operating system and application programs, are installed in the external storage apparatus 74 along with data to be used in the execution of the computer programs.
The input unit 75 is an operation unit provided with multiple keys as shown in
The following describes details of the configuration of the light emitting apparatus 3.
The LED blocks 311 to 316 respectively include three LEDs, namely LED 311A, LED 311B, and LED 311C to LED 316A, LED 316B, and LED 316C. The three LEDs included in the respective LED blocks 311 to 316, namely LED 311A, LED 311B, and LED 311C to LED 316A, LED 316B, and LED 316C, are arranged in a line along the short-side direction of the previously-described rectangular shape of the light emitting apparatus 3. In other words, 18 LEDs are arranged in a matrix in the light emitting apparatus 3.
Also, the LEDs 311A, 312A, 313A, 314A, 315A, and 316A are configured so as to emit light with a wavelength of 660 nm. This light with a wavelength of 660 nm is absorbed to a greater extent by reduced hemoglobin than oxygenated hemoglobin. The LEDs 311B, 312B, 313B, 314B, 315B, and 316B are configured so as to emit light with a wavelength of 805 nm. This light with a wavelength of 805 nm is absorbed to the same extent by oxygenated hemoglobin and reduced hemoglobin. Also, the LEDs 311C, 312C, 313C, 314C, 315C, and 316C are configured so as to emit light with a wavelength of 880 nm. The LEDs 311A, 312A, 313A, 314A, 315A, and 316A that emit light with a wavelength of 660 nm and the LEDs 311B, 312B, 313B, 314B, 315B, and 316B that emit light with a wavelength of 805 nm are used to measure a venous oxygenation index. The LEDs 311B, 312B, 313B, 314B, 315B, and 316B that emit light with a wavelength of 805 nm and the LEDs 311C, 312C, 313C, 314C, 315C, and 316C that emit light with a wavelength of 880 nm are used to measure a hemoglobin concentration.
Also, the LEDs 311A, 312A, 313A, 314A, 315A, and 316A that emit light with a wavelength of 660 nm are arranged in a column along the lengthwise direction of the light emitting apparatus 3. Similarly, the LEDs 311B, 312B, 313B, 314B, 315B, and 316B that emit light with a wavelength of 805 nm are also arranged in a column along the lengthwise direction of the light emitting apparatus 3, and the LEDs 311C, 312C, 313C, 314C, 315C, and 316C that emit light with a wavelength of 880 nm are also arranged in a column along the lengthwise direction of the light emitting apparatus 3.
The light amount adjustment unit 5 is connected to each of the drive circuits 321 to 326. This light amount adjustment unit 5 outputs a PWM signal to each of the drive circuits 321 to 326. The drive circuits 321 to 326 each supply a current that corresponds to the duty ratio of the received PWM (Pulse Width Modulation) signal to the corresponding one of the LED blocks 311 to 316. The light emission amounts of the LED blocks 311 to 316 are thus adjusted individually. In this case, current with the same value is supplied to each of the three LEDs provided in the same LED block. In other words, the three LEDs in the same LED block are subjected to light amount adjustment in an integrated manner.
Operation of Non-Invasive Living Body Measurement Device
Next, operation of the non-invasive living body measurement device 1 according to the present embodiment will be described.
The light amount adjustment unit 5 of the measurement unit 2 receives the execution instruction data and executes light amount adjustment processing.
If the average luminance is outside the intermediate range (NO in step S202), the light amount adjustment unit 5 increases or decreases the values of current to be supplied to (light amounts of) the LED blocks 311 to 316 (step S203). Specifically, if the average luminance is lower than the intermediate range, the light amounts of the LED blocks 311 to 316 are increased, and if the average luminance is higher than the intermediate range, the light amounts of the LED blocks 311 to 316 are decreased.
y=αx
3
+αβx
2
+αγx+C (1)
In the processing of step S203, the values of current to be supplied to the LED blocks 311 to 316 are adjusted by changing the parameter C in the equation 1 above. In other words, the overall light amount of the LED blocks 311 to 316 is increased or decreased while maintaining the light amount differences between the LED blocks 311 to 316.
After the processing of step S203 is performed, the light amount adjustment unit 5 returns to the processing of step S202. Accordingly, the processing of steps S202 and S203 is repeated until the average luminance falls within the intermediate range.
On the other hand, if the average luminance is within the intermediate range in step S202 (YES in step S202), the light amount adjustment unit 5 obtains an average luminance for each of a predetermined number of (two or more) columns of pixels aligned in the direction orthogonal to the lengthwise direction of the subject's middle finger 8 in the transmission image, and determines whether each of the average luminances falls within the intermediate range (step S204).
If any of the average luminances is outside the intermediate range in step S204 (NO in step S204), the light amount adjustment unit 5 obtains an average luminance for each of the columns of pixels aligned in the direction orthogonal to the lengthwise direction of the subject's middle finger 8, and calculates the difference between the maximum value and the minimum value among the average luminances (step S205). Next, the light amount adjustment unit 5 increases or decreases the values of current to be supplied to the LED blocks 311 to 316 in accordance with the calculated difference between the maximum value and minimum value among the average luminances (step S206).
y=P(x−q)2 (2)
In the processing of step S206, the values of current to be supplied to the LED blocks 311 to 316 are adjusted by changing the parameter P in the equation 2 above. Specifically, as shown in
After the processing of step S206 is performed, the light amount adjustment unit 5 returns to the processing of step S204. Accordingly, the processing of steps S204 to S206 is repeated until the average luminances fall within the intermediate range.
If all of the average luminances are within the intermediate range in step S204 (YES in step S204), the light amount adjustment unit 5 transmits data notifying the end of light amount adjustment processing to the information processing unit 7 (step S207), and ends the light amount adjustment processing.
As shown in
Next, the CPU 71 performs logarithmic transformation on a luminance distribution whose range crosses a blood vessel in the processing target region, and, based on the transformed image luminance distribution, creates a valley-shaped luminance profile whose local minimum is at the center of the blood vessel (step S305).
The following describes details of the processing of step S306.
Next, the CPU 71 sets H to a predetermined minimum value (e.g., 10% of a maximum depth Hm in the luminance profile) (step S402). The CPU 71 then clips out the portion from a valley bottom P to the depth H from the luminance profile (step S403), and converts the clipped-out portion into an absorption profile (step S404).
Next, the CPU 71 considers the absorption profile to be a distribution function (probability density function), and calculates a standard deviation a thereof and a width W at a height aH in the absorption profile (step S405).
Next, the CPU 71 determines whether 2σ and W match (step S406), and if they do not match (NO in step S406), re-sets H to a slightly higher value (step S407), and then returns to the processing of step S403.
As steps S403 to S406 are repeated, 2σ and W each change along with the increase in H, and when H reaches 75% of Hm, 2σ and W match each other, that is to say 2σ=W. The absorption profile obtained at this time is shown in
Next, the CPU 71 clips out the portion above the baseline BL in the absorption profile in
Next, the CPU 71 causes the LEDs 311B, 312B, 313B, 314B, 315B, and 316B to irradiate the subject's finger 8 with light with a wavelength of 805 nm (step S309), and causes the imaging unit 4 to capture an image of the finger 8 (step S310). The CPU 71 then searches for the same region as in step S304 in the transmission image for 805 nm wavelength light (hereinafter, referred to as “second transmission image”) captured by the imaging unit 4, and sets the found region as the processing target region (step S311).
Thereafter, in steps S312 to S315, processing similar to the processing performed on the first transmission image in steps S305 to S308 is performed on the second transmission image, and a height h2, a width W2, and an area A2 are calculated for the blood vessel profile corresponding to the wavelength of 805 nm.
The CPU 71 then calculates a depth t from the tissue surface to the blood vessel using the following equation (step S316).
t=(h2/W2n)/(h1/W1)m (3)
Note that m and n are constants.
Next, the CPU 71 calculates a blood vessel diameter φ as well as a hemoglobin concentration Hgb and a hematocrit value Hct of the blood flowing through the blood vessel using equations 4 to 6 respectively (step S317).
φ=A1p/h1=W1×f1(t) (4)
Hgb=(h1/A1q)×f2(t)×g(φ) (5)
Note that p and q are constants, and the functions f1, f2, and g are functions determined experimentally.
Hct=k·h1/h2+L (6)
Note that k and L are constants.
After the blood vessel depth, blood vessel diameter, hemoglobin concentration, and hematocrit value are obtained as described above, the CPU 71 returns to the call address of hemoglobin concentration detection processing in the main routine.
When the hemoglobin concentration detection processing ends, as shown in
Next, the CPU 71 causes the LEDs 311A, 312A, 313A, 314A, 315A, and 316A to irradiate the subject's finger 8 with light with a wavelength of 660 nm (step S502), and causes the imaging unit 4 to capture an image of the finger 8 (step S503). The CPU 71 then acquires a transmission image for 660 nm wavelength light (hereinafter, referred to as “third transmission image”) captured by the imaging unit 4 (step S504), and extracts an absorbance Ab3 for 660 nm wavelength light from the acquired third transmission image (step S505).
The CPU 71 then calculates a venous oxygenation index VOI using the following equation 7 (step S506).
VOI=−Ab3/Ab2 (7)
After the venous oxygenation index is obtained as described above, the CPU 71 returns to the call address of venous oxygenation index detection processing in the main routine.
When venous oxygenation index detection processing ends, as shown in
Note that although the above embodiment describes a configuration in which the light amounts of the LED blocks 311 to 316 provided in the light emitting apparatus 3 are independently controlled by the light amount adjustment unit 5, there is no limitation to this. A configuration is possible in which the light amounts of all of the LED blocks 311 to 316 are increased or decreased in an integrated manner. In this case, the LED blocks 311 to 316 are set such that the light amount increases with increasing distance from the LED blocks 313 and 314 that are the closest to the joint of the subject's finger, and the overall light amount of the LED blocks 311 to 316 is increased or decreased while maintaining the light amount differences between the LED blocks 311 to 316.
Also, although the above embodiment describes a configuration in which the light amounts of the LED blocks 311 to 316 are adjusted such that the light amount increases non-linearly with increasing distance from the joint of the finger placed on the platform 21, there is no limitation to this. A configuration is possible in which the light amounts of the LED blocks 311 to 316 are adjusted such that the light amount increases linearly with increasing distance from the joint of the finger placed on the platform 21.
Also, although the above embodiment describes a configuration in which the light amounts of the LED blocks 311 to 316 are adjusted such that the light amount increases with increasing distance from the joint of the finger placed on the platform 21, there is no limitation to this. For example, if a joint is not present at the measurement target site, there is no limitation to a configuration in which the light amounts of the LED blocks 311, 312, 315, and 316 are determined such that the light amounts of the central LED blocks 313 and 314 are low, and the light amount increases with increasing distance from the center, and it is sufficient that the light amounts of the LED blocks are adjusted such that the transmitted light amount is uniform in the imaging range.
Also, although the above embodiment describes a configuration in which the light amount adjustment unit 5 that performs light amount adjustment and the CPU 71 of the information processing unit 7 that performs image processing are provided separately, there is no limitation to this. A configuration is possible in which light amount adjustment processing and image processing are executed by one arithmetic processing unit.
Also, although the above embodiment describes a configuration provided with the LED blocks 311 to 316 arranged in a column, there is no limitation to this, and a configuration is possible in which the LED blocks are arranged in a zigzag line, for example.
Also, although the above embodiment describes a configuration in which a finger of the subject is the imaging target, there is no limitation to this. A configuration is possible in which a toe of the subject is imaged, and the hemoglobin concentration of the subject is detected based on the thus-obtained image.
The foregoing detailed description and accompanying drawings have been provided by way of explanation and illustration, and are not intended to limit the scope of the appended claims. Many variations in the presently preferred embodiments illustrated herein will be obvious to one of ordinary skill in the art, and remain within the scope of the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-217216 | Sep 2012 | JP | national |
This application claims priority from prior International Patent Application No. PCT/JP2013/076013, filed on Sep. 26, 2013, entitled “NON-INVASIVE LIVING BODY MEASUREMENT DEVICE”, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2013/076013 | Sep 2013 | US |
| Child | 14671591 | US |
