JPH04127036A - Optical type density difference meter - Google Patents

Abstract

PURPOSE:To enable the measuring of a density of material to be measured irrelevant to the concentration of a substance as factor causing errors by detecting the quantity of light of a three-wavelength component to compute the density of the material to be measured based on the quantity of reflected light of the wavelength component. CONSTITUTION:A light emitting circuit 35 receives an emission control signal of a CPU 30 to make a xenon flash tube 18 emit light. An object M to be inspected undergoes a digital conversion via first and second dichroic mirrors 13 and 14, optical band pass filters 15, 17 and 19, first, second and third photodetectors 16, 18 and 20 and an A/D converter 36 to be inputted into the CPU 30. A reloadable read-only-memory 39 has an absorption coefficient of bilirubin to be used for arithmetic processing of the results of measurement, absorption coefficients of substances as factor causing errors such as melanin pigment, coefficients of transmittance of subcutaneous tissue or the like and other data stored. A display control section 38 drives a display element 4 such as liquid crystal to show various display data to be outputted from the CPU 30.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to an optical densitometer, and in particular to an optical densitometer that can be applied to a jaundice meter used for early detection of jaundice in newborns. It is.

[Conventional technology] Neonatal yellow scars, which are found in most newborns, can sometimes progress to a severe stage, and there is a risk of seriously affecting the newborn's life and brain development, so it is important to detect it early. It is necessary to provide appropriate treatment. Accurate determination of the severity of jaundice should be based on the measurement of bilirubin levels in the blood serum collected from newborns, but it is difficult and may not be necessary to collect blood from all newborns for measurement. First, the necessity of blood sampling tests was determined by visually observing the skin.

For observation of the skin with the naked eye, a Gossett-type ectelometer (made of a plastic plate with a plurality of yellow standard color bands with five progressively darker tones and a transparent band between them) is used.
jaundice meter) is known.

Judgment of jaundice using an ichtelometer involves firmly pressing the zone pellucida against the tip of the newborn's nose so that the area is ischemized and the natural color of the skin appears. The status of jaundice is determined by comparing the results.

This is due to the fact that unconjugated bilirubin is fat-soluble and deposits in the fat layer of the subcutaneous tissue, yellowing the skin, so there is a certain correlation between skin color and serum bilirubin levels. Based on.

However, since the spectral reflectance of the yellow standard color band of the ichtelometer is different from the actual light absorption by bilirubin, there is a problem that it is not possible to accurately compare the skin color and the standard color under artificial lighting. Ta.

In order to deal with this problem, the applicant has developed a system that allows light to enter the skin, based on the knowledge that short wavelength light is absorbed more than long wavelength light by bilirubin deposited in the subcutaneous tissue. , calculate the reflectance of bilirubin at a first wavelength where the extinction coefficient is large and a second wavelength where the extinction coefficient is small from the reflected light that is scattered and reflected by the fat layer where bilirubin is deposited in the subcutaneous tissue and exits the skin surface. developed a yellow pox meter that uses an optical density difference detection method to measure the concentration of bilirubin deposited in the subcutaneous tissue from the difference in reflectance.
(See Publication No. 809).

[Problem to be Solved by the Invention 1] The above-mentioned jaundice meter, which measures bilirubin concentration from the difference in reflectance between the reflected light of a wavelength with a large extinction coefficient and the reflected light of a small absorption coefficient, can detect fat in the subcutaneous tissue. It has become clear that in addition to the bilirubin contained in the layer, the measured values are affected by the color of the skin, that is, the amount of melanin contained in the skin, causing measurement errors. For this reason, there has been a need for a measuring instrument that is not affected by skin color caused by racial differences, that is, error-causing substances such as melanin contained in the skin. Further, since fluctuations in the amount of light source light incident on the subject during measurement also cause measurement errors, there has been a need for a measuring instrument that is not affected by fluctuations in the amount of light source light. This invention aims to solve the above problems.

[Means to solve the problem]

This invention solves the above-mentioned problem, and consists of a first wavelength component that has a large absorption by a substance to be measured contained in a test substance and a small absorption by an error-causing substance, and a first wavelength component which has a small absorption by a substance to be measured and which causes an error. a light source light input means for making the light source light including a second wavelength component whose light absorption is large by the substance to be measured and a third wavelength component whose light absorption is small by the substance to be measured and the error factor substance enter the subject; The first step is to detect the amounts of light of the three wavelength components from the reflected light absorbed by the substance to be measured and the error-causing substance contained in the subject. Second
and a third reflected light amount detection means, and a calculation means for calculating the concentration of the substance to be measured based on a predetermined calculation formula in which the amounts of reflected light of the first, second, and third wavelength components are used as variables. Features.

Here, the predetermined arithmetic expression is the following expression.

However, ■ (e) Amount of reflected light at two wavelengths F (λ): Transmittance at wavelength ε of substances other than the substance to be measured and error-causing substances within the subject (e) Absorption of the substance to be measured at two wavelengths Coefficient m(e) Extinction coefficient of the error-causing substance at two wavelengths d: Effective optical path length kl, 2: Constant [Function] Error-causing substance (for example, melanin) of the substance to be measured (e.g. bilirubin) in the specimen Even if , the concentration of the substance to be measured can be measured regardless of the concentration of the error-causing substance by using an arithmetic expression that does not include a term related to the concentration of the error-causing substance.

[Examples] Examples of the present invention will be described below. First, the measurement principle will be explained.

Wavelengths λl, λ2, . When light of λ3 is incident,
When the light transmitted and scattered through the internal tissues of the subject and re-emerged on the subject's surface (hereinafter referred to as reflected light) is detected at a site far away from the incident site so as not to receive the light that is directly reflected on the skin surface, the Light quantity work (λ+), I (E2
), I (λ3) are Lambert-B
It is expressed by the following equation by applying the eer's law.

■(λ+)=Io(λ1)・F(λ,), 10-i
(λ1)°dC1-10-m(λl)aC2,,,(
1) I(12)=IO(λ2) −F(λ2)−10−
"λ2)d゛c1.10-"λ2)'d' C2,,,
(2)■(λ3): IO(λ3)・F(^3)・10″
E(λ3)°d01.10-”λ3)-cl C2,,
, (3) where Io (n): Incident light intensity at wavelength λ (e) Reflected light amount F at two wavelengths λ (e): Transmission of the substance to be measured in the subject, substances other than the difference factor substance at wavelength rate ε (e) Extinction coefficient d of the substance to be measured at two wavelengths λ : Effective optical path length cl : Concentration of the substance to be measured m (e) Extinction coefficient of the error-causing substance C2 at two wavelengths: Concentration of the error-causing substance above ( From equations 1) and (2), the optical density difference at wavelengths 1 and λ2 is expressed as follows.

-(m(^1)-m(λ2)) ・+1c2-(4)
Therefore, the first term on the right side of the equality sign in equation (4) log (F(
λ+)/F(λ2)) and the third term (+n(λ+)−+n
(λ2)) When d·C2 is constant, the concentration C2 of the substance to be measured can be determined from the optical density difference.

However, the third term is a term related to the extinction coefficient of the error-causing substance. Considering the case of a jaundice meter that measures bilirubin concentration as a substance to be measured based on the difference in optical density, the error-causing substance that causes measurement errors is melanin, which is a pigment in the skin. The amount of melanin pigment produced varies by race. Therefore, since the value of the third term of the equation (4) changes depending on the race, the concentration of bilirubin, which is a substance to be measured, cannot be accurately measured depending on the equation (4) depending on the race.

Therefore, in this invention, the above (1) and (2).

The variable related to the error-causing substance was deleted from equation (3), making it possible to measure the concentration of the substance to be measured regardless of the concentration of the error-causing substance. That is, by taking the logarithms of the left and right sides of the equal sign in equations (1), (2), and (3), the following is obtained.

Rag I(λ+) =log Io(^1)+log
F(λ1)-ε(λ+Lcl c+-m(1+)・cl
c2... (5) 1ogI(λ2) = jog Io(λ2) + l
og F(λ2)−ε(λ2)dcl−m(12)・d
c2... (6) 1o(gr(λ3) = 1og Io(λ3)+lo
gF(λ3)-ε(λ3Lcl cr-rnI upper 3)
-+1c2 (5), (6), (7) are transformed to IogI(λt)-jog F(λ1) = -t
(1+LdC1-m(^1) -cLc2+ jog
Io(λ1)■(^2) ... (8) -1ogF(λ2)=-ε(λ2)-d・C1-m(
λ2) ・+lc2+ log Io(λ2)...
(9) ■(λ3) -jogF(λ3) Knee E (13)-cl
cl-m(13) ・cLc2+ log Io(λ3
)... (lO) (8), (9), and (10) are expressed as determinants as follows.

... (11) However, the wavelength λ1. E2. The ratio between the amounts of incident light of λ3 is almost constant, and k 2 = fog Io(12)/log
Io(λ1).

k3=ffiog Io(13)/log Io(λ1
).

Therefore, according to the areamar formula, the concentration C of the substance to be measured can be expressed by the following formula.

Here, the wavelength of the light source light suitable for measuring the bilirubin concentration while eliminating the influence of melanin contained in the skin and hemoglobin in the blood will be explained. Considering that the spectral extinction coefficients of bilirubin, hemoglobin (Hb), and oxidized hemoglobin (Hb○2) are as shown in Figure 12, the first wavelength component has a large extinction coefficient for bilirubin, and melanin, The second wavelength component is a wavelength at which the extinction coefficient of hemoglobin and oxidized hemoglobin is small, for example around 450 nm, and the second wavelength component is a wavelength at which the extinction coefficient of bilirubin is small and the extinction coefficient of melanin, hemoglobin, and oxidized hemoglobin is large,
For example, it is around 550 nm, and the third wavelength component is desirably a wavelength in the infrared region where bilirubin, melanin, hemoglobin, and oxidized hemoglobin have relatively small extinction coefficients.

In addition, in the above explanation of the principle, light is incident on the skin,
The light scattered and reflected by the subcutaneous tissue and returned to the skin surface (reflected light) is detected to determine the difference between the amount of incident light and the amount of reflected light, and based on this, the influence of the error-causing substances is removed and the measured substance is determined. The case of determining the concentration has been explained. However, instead of this, if you sandwich the object and let light enter from one side, detect the light that has passed through the object (transmitted light) on the other side, and find the difference between the amount of incident light and the amount of transmitted light. The above measurement principle and calculation formula also hold true.

Next, an optical density difference meter to which the present invention is applied will be explained.

Figure 1 is a perspective view showing the external appearance of the optical density difference meter. 1 is the main body, 2 is the power switch, 3 is the setting of the operation mode, the setting of the display mode (display unit) of the measured value, and the setting of the warning display limit value. A function setting section for setting and switching the number of displayed digits is provided with six switches 38 to 3f. The functions of these switches will be described later.

Reference numeral 4 denotes a display element, which includes a measurement value display section 4a, a measurement preparation completion display section 4b, and a unit display section 4C. Reference numeral 5 denotes a measurement probe, which is equipped with an annularly formed light projection opening 6 and a light receiving lower placed at the center of the opening. The measurement switch 5a is configured so that the measurement switch 5a is closed.

The functions set by the function setting section 3 will be explained.

Operation modes include ■Measurement mode, ■Line calibration mode,
■There are service mode 1 and service mode 2.Measurement mode is a mode to measure the optical density difference corresponding value, line calibration mode is a mode for calibration during manufacturing process and service, and service mode 1 and 2 are for repairs etc. This is the mode to be set when. The operation mode is set using switches 3a and 3.
The switch states and set operation modes are as shown in Table 1.

Table 1 Measured value display modes include ■ optical density difference corresponding value display mode and ■ serum bilirubin concentration corresponding value display mode, the former is a mode that displays the measured optical density difference corresponding value as is, and the latter is a mode that displays the measured optical density difference corresponding value Concentration differences can be calculated using a conversion formula (Y = 1.08x + 7.22) created based on the clinically confirmed correlation shown in Figure 13, or a conversion table created based on this conversion formula. In this mode, the value is converted into a value corresponding to bilirubin concentration and displayed. The display mode is set by the switch 3C, and the switch states and set display modes are as shown in Table 2.

Table 2 Warning display limit value is a value that warns of the necessity of blood sampling test when the measured optical density difference corresponding value exceeds the set limit value. The warning display limit value can be set using switches 3d and 3.
The switch states and set limit values are as shown in Table 3.

The number of digits displayed in the table is 2 digits for integers, 2 digits for integers and 1 digit after the decimal point.
Two types of display, digit display and digit display, are possible and can be switched as shown in Table 4 by switch 3f.

Table 4 FIG. 2 is a perspective view showing the optical system of the optical density difference meter.

Reference numeral 11 denotes an optical fiber bundle, one end 11a of which is formed with a rectangular cross section facing the xenon arc tube 18, and the other end 11b.
is connected to an annular light projection aperture 6 within the probe 5.

12 is also an optical fiber bundle, one end of which is joined to the light-receiving lower portion at the center of the probe 5, and the other end 12b facing the first dichroic mirror 13. A second dichroic mirror 14 is arranged behind the first dichroic mirror 13, and the first and second dichroic mirrors 13.14 convert the incident light into a wavelength range including the wavelength 1 and a wavelength range including the wavelength λ2. The wavelength range is divided into three wavelength ranges: a wavelength range, and a wavelength range including wavelength λ3. 15 is an optical bandpass filter that transmits light around wavelength λ1; 16 is a first light receiving element;
17 is an optical band-pass filter that transmits light around wavelength χ2; 18 is a second light-receiving element; 19 is an optical band-pass filter that transmits light around wavelength λ3; and 20 is a third light-receiving element.

The light emitted from the xenon arc tube 18 passes through the optical fiber bundle 11, reaches the annular light projection opening 6 of the probe 5, and enters the subject from there. The light that enters the subject, transmits and scatters through the subcutaneous tissue, is partially absorbed, and returns to the subject's surface (hereinafter referred to as reflected light) is captured by the light-receiving lower part at the center of the probe S. , is guided through the optical fiber bundle 12 to first and second dichroic mirrors 13, 14, and is divided into three wavelength ranges. Only light with a wavelength of around λ1 is selected by the optical bandpass filter 15 and detected by the first light receiving element 16, and only light with a wavelength around λ2 is selected by the optical bandpass filter 17 and detected by the second light receiving element 18. , only light around wavelength 3 is filtered using an optical bandpass filter]
9 and detected by the third light receiving element 20.

FIG. 3 is a block diagram showing the circuit of the optical density difference meter. In the figure, a CPU 30 performs control operations such as controlling measurement operations and calculating measurement results based on arithmetic expressions. 31 is an internal battery built into the main body, and 32 is a constant voltage circuit, which supplies power to each circuit element described below. 33 is a power storage booster circuit that boosts the voltage supplied from the internal battery and charges a main capacitor provided inside to cause the xenon arc tube 18 to emit light. 34 is a charging completion detection circuit that detects the completion of charging of the main capacitor and
A charging completion signal is output to 30.

35 is a light emitting circuit which receives a light emission control signal output from the CPU 30 and causes the xenon arc tube 18 to emit light. M is the object to be examined, 13 to 20 are the elements constituting the optical system explained in FIG. 2, and 13 and 14 are the 1. The second dichroic mirror, 15°17.19 is an optical bandpass filter, and the first dichroic mirror is 1618.20, respectively. Second. The third light-receiving element 36 is an A/D converter, which converts the outputs of the first to third light-receiving elements into digital signals and inputs them to the CPU 30. 3
Reference numeral 8 denotes a display control unit that drives the display element 4 such as a liquid crystal or LED to display various display data output from the CPU 30. 39 is a rewritable read-only memory (hereinafter referred to as
It stores the extinction coefficient of bilirubin, extinction coefficient of error-causing substances such as melanin, coefficients of transmittance of subcutaneous tissue, and other data used when calculating measurement results. There is. Further, 5a is a measurement switch that is turned on when the probe 5 is pressed against the subject M;
2 is a power switch, and 3 is a function setting section consisting of six switches 3a to 3f. 40 is a charger external to the main unit,
Used when a rechargeable battery is used as the internal battery 31.

Note that the internal battery may be removed and charged, or a non-rechargeable battery may be used.

Next, an outline of the circuit operation will be explained. It is assumed that the operation mode is set to the measurement mode by the switches 3a and 3b of the performance setting section 3. The power switch 2 is turned on, power is supplied from the constant voltage circuit 32 to each circuit element, and the power storage booster circuit 33 is activated to start charging the main capacitor. When the completion of charging is detected by the charging completion detection circuit 34, a detection signal is input to the CPU 30, and the completion of measurement preparation is displayed on the display element 4. When the operator presses the probe 5 against the subject M, the measurement switch 5a is turned on.
A light emission control signal is output from the CPU 30 to the light emitting circuit 35, and the xenon arc tube 18 emits light. xenon arc tube 18
The light emitted from enters the subject M, and the reflected light transmitted and scattered within the subcutaneous tissue is reflected by dichroic mirrors 13 and 14.
Optical bandpass filter 15, 17° 19
After that, light with a wavelength around λ1 enters the first light receiving element 16, light with a wavelength around 2 enters the second light receiving element 18, and light with a wavelength around λ3 enters the third light receiving element 20.

Detection signal A/D converter 3 of each light receiving element i6, 18.20
6 and is input to the CPU 30. The CPU 30 calculates according to the above-described calculation formula (12) using the manually input detection signal and the coefficients stored in the memory 39, and displays the calculation result input from the switch 3c of the function setting section 3. Depending on the mode, it is displayed on the display element 4 together with the unit display. At this time, if a warning limit value is set by the switches 3d and 3e of the function setting section 3, the set limit value and the calculation result are compared, and if the limit value is exceeded, a warning is displayed (this In the example, the calculation result is displayed in red)6
Also, the number of digits displayed in the calculation result is determined by the switch 3 in the function setting section 3.
Displayed with the number of digits specified by f.

When the operation mode is set to the line calibration mode by the switches 3a and 3b of the function setting section 3, the same operation as in the measurement mode is performed for the calibration plate 25 as shown in FIG. 4 instead of the subject. The measurement result is stored in the memory 39 as a calibration constant. The calibration plate 25 has flat spectral reflectance characteristics and has wavelengths λ1. λ2. A calibration plate “OO” with an optical density difference of 0 at λ3 and a calibration plate ゛°20°° with a wavelength of I, an optical density difference of 1 at λ2゜λ3.
It consists of In this example, the optical density difference is displayed at a magnification of 20 times, so the optical density difference "1" is
"20" on the calibration plate similarly indicates an optical density difference of 1.

Next, regarding the control calculation operation executed by the CPU, the fifth
This will be explained based on the flowcharts shown in FIGS. 11 to 11. FIG. 5 is a flowchart showing an overview of the control calculation operation. When the power switch 2 is turned on and control according to the program is started, the system is first initialized (step PL). Specifically, the initialization of the system includes initial settings within the CPU 30, initial settings for each I10 board, initial value settings for each variable, checking the operating status of the display element, etc. Next, the operation mode is determined from the states of the switches 3a and 3b (steps P2 and P3). If both the switches 3a and 3b are OFF, it is the measurement mode, and the process moves to the measurement mode processing routine shown in step P4. If the switch 3a is ON and the switch 3b is OFF, it is a line calibration mode for calibration in the manufacturing process or calibration performed by a service person, so the process moves to the line calibration mode processing routine shown in step P5. Switch 3a is OFF
, 3b are ON, and both switches 3a and 3b are OFF.
In the case of N, since the mode is a service mode for failure detection in the case of repair, etc., the process moves to the service mode process shown in step P6. Note that the service mode processing is not directly related to the present invention, so a description thereof will be omitted.

FIG. 6 is a flowchart showing details of the measurement mode process shown as step P4 in FIG. first,
Check whether the contents of the memory 39 are normal (step pH). If it is determined that the memory 39 has been destroyed and the correct coefficients are not stored, an error display (El) is displayed (step P).
17), stop. When the contents of the memory 39 are determined to be normal, charging processing (step P12), measurement processing (step P13), calculation processing (step P14), and display processing (step P15) are executed. Step P16), O
If it is not FF, the process returns to step P12 and the processes of steps P12 to P15 are repeated. Measurement switch 5
If a is turned off, the process returns to the main routine.

FIG. 7 is a flowchart showing details of the charging process shown as step P12 in FIG. First, charging of the main capacitor is started (step P21), and completion of charging is determined (step P22). Step P2 to wait for the completion of charging and terminate the charging operation of the main capacitor.
3), Step P24) to turn on the charging completion display element;
Return to main routine.

FIG. 8 is a flowchart showing details of the measurement process shown as step P13 in FIG. First, it is determined whether the measurement switch 5a is ON or not (step P31).
, when the measurement switch 5a is ON, the charging operation of the main capacitor is ended (step P32). In order to eliminate the influence of light (offset light) that leaks from the contact area between the probe 5 and the subject M, the wavelength is set to 1. λ2. The light quantities OB and 02.03 of the offset light at step P3 are detected by the light receiving elements 16 and 18.20, respectively, and these detection signals are charged into an integrating capacitor for a predetermined time (step P33). The detected signal charged in the integrating capacitor is A/D converted and stored in a predetermined area of the memory 39 as offset values Of, 02, 03 (steps P34 and P35). It is determined whether or not the offset value 01.02.03 is less than or equal to a predetermined value (step P36), and if it is not less than the predetermined value, the probe 5 is not in proper contact with the subject M, and external light is incident. It is determined that the error has occurred, an error display (E2) is performed (step P43), and the process moves to step P45. If it is less than a predetermined value, it is determined that the probe 5 is in proper contact, and the xenon arc tube is made to emit light (step P37).
), wavelength λ1. λ2. Light amount Ml of reflected light of λ3, M2
, M3 are detected by the light receiving elements 16, 18, and 20, and these detection signals are charged into an integrating capacitor for a predetermined time (step P38). The signal detected and charged in the integrating capacitor is A/D converted (step P39), and the exchange value Ml
, M2, M3 are the offset values 01.02 obtained previously.
, 03 to obtain the measured value S1. S2. Obtained S3 and memo 3
9 to be stored in step P40. P41), the charging completion display element is turned off (step P42), and the process returns to the main routine.

If it is determined in step P31 that the measurement switch 5a is not ON, the process moves to step P45, where it is checked whether charging of the main capacitor is completed, and if charging is completed, the charging operation is terminated, and if charging is not completed, the charging operation is restarted. (Step P
46. P47), return to step P31.

FIG. 9 is a flowchart showing the arithmetic processing shown as step P14 in FIG. First, in the line calibration mode to be described later, the wavelength λ1. λ2. Calibration constant Al in E3, A2. 2. from A3 to the value in equation (12). 3 is calculated using the following formula (step P51)
.

k+ = jog A2 /log 3 to A1 = log
A3 /log A1 Next, the measured values Sl, S2. S3
is read from the memory 39, and in equation (12) (see measurement principle section), ■ (λ1) is set to Sl, I (e2) is set to 52. Substituting S3 into I(e3), calculating the bilirubin concentration C1 (step P52), and returning to the main routine.

FIG. 10 is a flowchart showing details of the display process shown as step P15 in FIG.

First, it is determined whether the display mode set by the switch 3C of the function setting section 3 is the optical density difference display mode (step P61). In the optical density difference display mode, since the measured value is displayed as it is, the unit display element is turned off (step P62). If the optical 1 degree difference display mode is not set, the measured value is converted to a value corresponding to serum bilirubin concentration and displayed, so the unit display element is lit and the measured value is converted to a value corresponding to serum bilirubin concentration (step P
63. P64). This conversion may be performed using a conversion formula obtained based on the correlation between the optical density difference and the serum bilirubin concentration shown in FIG. 13, or a conversion table prepared based on the conversion formula.

Determine the number of display digits set by the switch 3f of the function setting section 3, and in the case of a 2-digit integer display, change the measured value to 2 integers.
Add 4 to 5 in the digit (steps P65 and P66).

Furthermore, the magnitude relationship between the warning display limit value set by the switches 3d and 3e of the function setting section 3 and the measured value is determined, and if the measured value is less than the limit value, the measured value is displayed on a green display element, When the limit value is exceeded, the measured value is displayed with a red display element (steps P67, P68, and P69), and the process returns to the main routine.

FIG. 11 is a flowchart showing the line calibration mode process shown as step P5 in FIG. In line calibration mode, wavelengths λ1°λ2. Calibration plates “00” and “20” with optical density differences O and 1 in E3 respectively.
Calibration constants are obtained by calculating the average value of eight measurements for each wavelength using
It is used to correct individual variations in measured values and displayed values due to variations such as a deviation of about m.

First, a calibration constant for an optical density difference of 0 is determined. Calibration plate “Oo”
” is set, the counter is set to 8 (steps P71 and P72), and charging processing and measurement processing (steps P73 and P74) are executed. Note that step P73
The processing contents of P74 and P74 are the same as the charging process and the measurement process described above using the flowcharts of FIGS. 7 and 8.

The measured value is taken in, 1 is subtracted from the counter, and steps P73 to P77 are repeated until the counter content becomes O. Wavelength! , λ2. For each of λ3, the average value of each of the eight measured values Al, A2, A3
is determined and stored in memory (step P78). Next, check the setting of calibration plate “20” (Step P79)
, and thereafter, the same processes as steps P72 to P77 are executed (steps P80 to P85), and the average values B+, B2. B3 is determined and stored in memory (step P86). The obtained average value A, , A2 , A
3 and Bl, B2. Find the calibration constant from B3 and store it in memory 3.
9 (step P87) and returns to the main routine.

By providing this calibration mode, it is no longer necessary to remove the cover of the main body for calibration and adjust the variable resistor to change the constants of the hardware circuit, as in the conventional case.

In the embodiments of the invention described above, a xenon arc tube is used as the light source, and the optical system is composed of an optical fiber, a dichroic mirror, and an optical bandpass filter. Alternatively, a blue light emitting diode or a green light emitting diode may be used. In this case, each light emitting diode can be provided in the probe portion so that light is directly incident on the subject. Furthermore, when a light emitting diode is used as the light source, the number of light receiving elements that receive reflected light may be one, and the two light emitting diodes may be caused to emit light in a time-sharing manner.

In this embodiment, the CPU controls the light emission of the xenon arc tube, but does not control the amount of light emitted. However, since the amount of light emitted from the xenon arc tube is detected by the light receiving element for monitoring light emission, this may be used to control the light emission to stop when the amount of emitted light reaches a predetermined value. This can prevent unnecessary battery consumption.

In this embodiment, the function setting section is configured to include a plurality of switches to set various modes, but it may also be configured using a mode changeover switch and up/down keys. In this case, the set display mode is stored in memory.

In this embodiment, the light projection aperture 6 and the light receiving lower are provided integrally,
Although the structure is configured to be pressed perpendicularly to the subject, the structure is not limited to this, and any structure may be used as long as the light receiving port does not directly receive light reflected from the skin surface. . For example, the light projection aperture and the light receiving aperture may be separate bodies, and the object may be sandwiched between them from both sides. In this case, the light that passes through the object is detected.

Further, the optical density difference meter of the present invention can be used not only as a jaundice meter, but also as a measuring instrument in the beauty field, such as measuring the color of the face and other skin.

[Effects of the Invention] As explained above, according to the present invention, when measuring the concentration of a substance to be measured contained in a subject, such as bilirubin, the concentration of an error-causing substance contained at the same time, such as melanin pigment, can be measured. It is possible to measure only the concentration of the substance to be measured. When this invention is applied to a jaundice meter, jaundice symptoms can be detected accurately without being affected by differences in skin color due to racial differences.

Further, according to the present invention, accurate measurements can always be performed without being affected by fluctuations in the amount of light from the light source.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing the external appearance of the optical density difference meter according to the present invention, Fig. 2 is a perspective view showing the configuration of the optical system, Fig. 3 is a circuit block diagram, and Fig. 4 is a plan view of the calibration plate. , FIG. 5 to FIG. 11 are flowcharts explaining the control calculation operations executed by the CPU, FIG. 12 is a diagram showing the spectral extinction coefficients of bilirubin and hemoglobin, and FIG. 13 is a diagram showing the optical density difference corresponding value and serum bilirubin. FIG. 7 is a diagram showing a correlation with density corresponding values. 1: Main body, 3: Function setting section, 4: Display element, 5 Probe, 6: Light projection aperture, 7: Light receiving aperture, 11, 12: Optical fiber, 13.14: Dichroic mirror, 15, 17
, 19: Optical bandpass filter, 16, 18, 20:
Light receiving element. Applicant Minolta Camera Co., Ltd. Figure 5 Figure 10

Claims (2)

[Claims] (1) A first wavelength component that has a large absorption by the analyte contained in the test substance and a small absorption by the error-causing substance, and a second wavelength component which has a small absorption by the analyte and a large absorption by the error-causing substance. and a third wavelength component that is less absorbed by the substance to be measured and the error-causing substance. first, second and third reflected light amount detection means for respectively detecting the light amount of the three wavelength components from the reflected light absorbed by the measured substance and the error factor substance;
An optical density difference meter characterized by comprising a calculation means for calculating the concentration of a substance to be measured based on a predetermined calculation formula in which the amounts of reflected light of the first, second, and third wavelength components are used as variables. (2) In the optical density difference meter according to claim 1, the predetermined calculation formula is: ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ However, I (λ): Wavelength Amount of reflected light at λ F(λ): Transmittance at wavelength λ of a substance other than the substance to be measured and the error-causing substance in the subject ε(λ): Extinction coefficient of the substance to be measured at wavelength λ m(λ): Wavelength λ An optical density difference meter characterized in that the extinction coefficient d of an error-causing substance is a constant: effective optical path length k_1, k_2: constant.