JPH05288674A - Sacchari meter - Google Patents

Abstract

PURPOSE:To measure sugar degree accurately without damaging the body to be inspected such as vegitables and fruits. CONSTITUTION:The operating expression, which indicates the correlation of both parts for the light having the wavelength of 1,100nm or less that has the high correlation between the sugar degree and the reflectiviy for a sample to be detected, is determined beforehand. The near infrared rays having the two different wavelengths lower than the wavelength of 1,100 are cast into a body under test from LEDs 10 and 11. The reflected lights are detected with a photodiode 12. In a CPU, at first, the reflectivity is computed based on the projected light and the reflected light, and the sugar degree is farther computed based on the specified operating expression. The result is outputted into a display part 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sugar content meter, and more particularly to a sugar content meter capable of measuring the sugar content of fruits and vegetables without damaging the fruits and vegetables.

[0002]

2. Description of the Related Art The quality of fruits and vegetables is evaluated not only by appearance but also by taste. Conventionally, it has been judged by visual observation or observation by touching with a finger, but this is not sufficient, and if you actually try the sample or cut out a part of the sample and check the results of its component analysis. The taste was being evaluated. However, such an inspection cannot be 100% inspected, the inspection efficiency is low, and the inspection cost is considerable. Therefore, an inspection method that can inspect 100% without damaging the fruits and vegetables and can quickly evaluate the taste is required. It was being done.

By the way, in general, as a means for analyzing the chemical properties of a substance, the types and contents of various substances contained in the substance to be inspected are known based on the light absorption, reflection, and transmission characteristics of the substance to be inspected. The inspection method is known. On the other hand, it is empirically known that the taste of fruits and vegetables is mainly determined by the sugar content. Therefore, a quality inspection method for fruits and vegetables and a device for irradiating the fruits and vegetables with near infrared rays and measuring the sugar content of the fruits and vegetables based on the reflectance thereof have been proposed (see Japanese Patent Laid-Open No. 64-28544).

[0004]

However, in the quality inspection apparatus for fruits and vegetables described above, the measurement accuracy changes depending on the selection of the wavelength of the near-infrared rays to be used, and it is required to select an appropriate wavelength. Further, a normal halogen lamp is used as a means for irradiating near infrared rays, but since the halogen lamp has a wide wavelength range of light, it is necessary to use a filter to obtain light of a specific wavelength range suitable for irradiation. In addition, since a large-capacity power source is required, the device becomes large in size, which makes it unsuitable for portable use in fields such as fields. The present invention is intended to solve the above problems.

[0005]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems and comprises a light projecting means having a light source for projecting light onto a subject, and a light detecting means for detecting light reflected by the subject. In a sugar content meter that detects the sugar content of a subject based on the reflectance of at least two different wavelengths of light, the light projected onto the subject is at least two different wavelengths of light selected from wavelengths of 1100 nm or less. As a light source of the light projecting means, a light emitting diode or a xenon discharge tube can be used.

[0006]

By selecting the light projected onto the subject from the light having a wavelength of 1100 nm or less, the reflectance and the sugar content show a high correlation, and the sugar content can be accurately measured.
Further, by using the light emitting diode or the xenon discharge tube as the light source of the projected light, the power consumption can be reduced and the device can be made compact.

[0007]

Embodiments of the present invention will be described below.
First, the measurement principle will be described. The sugar content meter of the present invention shows that the sugar content of a subject such as fruits and vegetables and the reflectance of near-infrared rays (which may include a visible light component) of a specific wavelength with which the subject is irradiated show a certain correlation. Utilizing this method, the near-infrared light of a specific wavelength is radiated to the subject whose sugar content has been determined in advance to obtain its reflectance, and an algorithm showing the correlation between the sugar content and the reflectance is obtained in advance. The object to be measured is irradiated with near-infrared light having a specific wavelength to determine its reflectance, and the reflectance is processed according to the above algorithm to determine the sugar content.

It is now assumed that fruit juices are extracted from samples A, B and C selected in advance according to the type of the subject (fruit and fruit) and the sugar contents measured by a known refractometer are SA, SB and SC. .. Next, the reflectance of near-infrared light of wavelength λ1 and wavelength λ2 with respect to sample A is RA1 and RA.
2. Wavelength λ1 and wavelength λ2 irradiated for sample B
If the reflectance of near infrared light of RB1 and RB2 and the reflectance of near infrared light of wavelength λ1 and wavelength λ2 irradiated for sample C are RC1 and RC2, sample A,
Sugar content SA, SB, SC of B and C, and reflectance R
The following relational expressions (1), (2) and (3) are established between A1, RA2, RB1, RB2, RC1 and RC2.
However, a, b, and c are coefficients.

[0009]

[Equation 1]

[0010]

[Equation 2]

[0011]

[Equation 3] Therefore, the equations (1), (2) and (3) are solved for the coefficients a, b and c to determine the coefficient values an, bn and cn.

Next, subject (fruit and fruit) whose sugar content is to be measured is irradiated with near-infrared light of wavelength λ1 and wavelength λ2, and the reflectance is RX1 and RX2. SX is represented by the following formula (4).

[0013]

[Equation 4] When the number of wavelengths to be used is k, which is more than two, and the reflectance at the wavelength i is Ri, the relationship between the sugar content S and the reflectance at each wavelength is represented by the following formula (5).

[0014]

[Equation 5] The coefficients a0, a1, and a2--ak can be determined by measuring the sugar content of at least k + 1 or more samples with a refractometer and measuring the reflectance at each wavelength. From these coefficients and the measured reflectance values at the k wavelengths of the subject, the sugar content of the subject can be obtained based on the equation (5).

Regarding the wavelength of near infrared light to be irradiated, according to the results of experiments conducted on various types of specimens (fruits and fruits), the wavelength is 600 to 2500 nm, and particularly the wavelength is 600 to 1100 nm.
Was found to be suitable.

FIG. 1 is an external view of a sugar content meter embodying the present invention. In FIG. 1, 1 is a main body, 2 is a probe, S1 is a power switch, S2 is a measurement switch, and 3 is a sugar content in five levels. A display unit for displaying, which includes LEDs 3a to 3e. Reference numeral 4 denotes an output terminal that outputs the measurement result as a digital signal. FIG. 2 is a sectional view showing the structure of the probe 2, 10 and 11 are LEDs, and the LED 10 has a wavelength λ1.
In addition, the LED 11 projects near-infrared light having a wavelength λ2.
12 is a photodiode that receives the reflected light from the subject.
Reference numerals 13, 13 and 14 denote optical fibers, one end of which is opposed to the LEDs 10 and 11 respectively, and the other end of which is arranged at a position for projecting near-infrared light onto a subject inside the detection surface 2a of the probe 2. There is. Reference numeral 15 is also an optical fiber, one end of which is arranged at a position for receiving the reflected light from the subject in the detection surface 2a, and the other end of which is opposed to the photo diode 12. The arrangement of these optical fibers in the detection surface 2a of the probe 2 is concentrically arranged as shown in FIG. 2, but the arrangement is not limited to this and may be an appropriate arrangement suitable for measurement. .. Further, the display unit may be a multi-stage display such as 5 stages using the above-mentioned LED, or may be a digital display.

FIG. 3 is a block diagram of the measuring circuit. 19
Is the CPU, controls the entire sugar content meter, and LEDs 10, 11
The reflectance is calculated from the amount of emitted light and the amount of reflected light detected by the photo diode 12, the calculation based on the equation (4) described above is performed to calculate the sugar content, and the measurement result is output to the display unit 3. Further, the measurement result is output from the output terminal 4 to an external information processing device (not shown). 16 is a light emission control circuit, CP
LED10 based on the control signal output from U19,
The LEDs 11 are alternately made to emit light. Reference numeral 17 is an amplifier, and 18 is an A / D converter, which amplifies the output of the photo diode 12, A / D converts it, and inputs it to the CPU 19. 20 is LE
D10, a memory that stores the light emission amount data of the LED 11 and the coefficient values an, bn, cn of the above formula (4), and 22 is a constant voltage circuit that stabilizes the electric power of the battery E to a constant voltage. Supply to the element.

Next, the operation of the measuring circuit will be described. When the power switch S1 is turned on and the measurement switch S2 is closed after the preparation for the measurement operation is completed, a control signal is sent from the CPU 19 to the light emission control circuit 16 so that the LED 10 and the LED 11 alternately emit light at a constant cycle and the optical fiber 13 , 14, near-infrared light of wavelengths λ1 and λ2 is projected toward the subject M. The light reflected by the subject M passes through the optical fiber 15 and is detected by the photo diode 12, and the detected signal is the amplifier 1
7, through the A / D converter 18 and input to the CPU 19.
The CPU 19 is the LED 10 stored in the memory 20,
A constant indicating the amount of light emitted from the LED 11 and the photo diode 12
The reflectance RX1 of near-infrared light of wavelength λ1 and the reflectance RX2 of near-infrared light of wavelength λ2 are calculated from the output of the above equation, and the reflectances RX1 and RX2 and the coefficient values an and b are added to the equation (4).
Substituting n and cn, the sugar content SX is calculated. The detected and calculated sugar content is identified in five levels, and the LED 3a of the display unit 3 is used.
~ 3e is lit to output and output terminal 4
Is output as a digital signal, and if necessary, processed by an information processing device (not shown).

In the above embodiment, L is used as the light source of near infrared light.
ED is used, but the emission wavelength of LED is about 95
Since it is limited to within 0 nm, it is necessary to select a wavelength having a correlation with sugar content in this range. According to experiments, in the case of melon, wavelengths λ1 and λ2 are 768 nm, respectively.
And 848 nm, the correlation coefficient is 0.86
1, the standard deviation was 0.674, and the result was that it could be used sufficiently. These are the results obtained by measuring the reflectance at the equatorial part of the melon, but better correlation and standard deviation were obtained when measuring the flower scar part.

FIG. 4 is a block diagram of the measuring circuit according to the second embodiment of the present invention. In this embodiment, a xenon discharge tube is used as a light source of near infrared light instead of the LED used in the previous embodiment. Since the emission characteristics of the xenon discharge tube cover a wide wavelength range, the light receiving element side that detects the reflected light selectively receives the wavelengths λ1 and λ2. The optical fiber in the probe of the second embodiment is used.
Since the arrangement and the like are the same as those in the first embodiment, the description thereof will be omitted.

In FIG. 4, 30 is a xenon discharge tube, 3
Numerals 6 and 38 are photo diodes, and the light receiving surface thereof has a filter 3 for selectively transmitting light of wavelengths λ1 and λ2, respectively.
5, 37 are arranged. Reference numeral 31 is an optical fiber that projects the projection light emitted from the xenon discharge tube toward the subject M, and 32 and 33 are optical fibers that guide the reflected light reflected by the subject M to photo diodes 36 and 38. Also,
40 is a light emission control circuit for controlling light emission of the xenon discharge tube 30, 41 and 42 are amplifiers, 43 is a multiplexer, 44
Is an A / D converter, 46 is a memory that stores the light emission amount data of the xenon discharge tube 30 and the coefficient values an, bn, cn of the formula (4), and 45 is a CPU that controls the entire sugar content meter. ,
And the amount of light emitted from the xenon discharge tube 30 and the photo diode 3
The reflectance is calculated from the reflected light amounts detected in 6 and 38, the calculation based on the above-described formula (4) is performed to calculate the sugar content, and the measurement result is output to the display unit 3. Further, the measurement result is output from the output terminal 4 to an external information processing device (not shown). A constant voltage circuit 47 stabilizes the electric power of the battery E to a constant voltage and supplies it to each circuit element.

Next, the operation of the measuring circuit will be described. When the power switch S1 is turned on and the measurement switch S2 is closed after the preparation for the measurement operation is completed, a control signal is sent from the CPU 45 to the light emission control circuit 40, the xenon discharge tube 30 emits light, and the test object passes through the optical fiber 31. Project light toward M. The light reflected by the subject M passes through the optical fiber 32 and the filter 35, and the light of wavelength λ1 is converted into the photo diode 3
The light having the wavelength λ2 is detected by the photo diode 38 through the optical fiber 33 and the filter 37. Each detection signal is amplified by the amplifiers 41 and 42, and is input to the CPU 45 via the multiplexer 43 and the A / D converter 44.

The CPU 45 uses the constant indicating the amount of light emitted from the xenon discharge tube 30 stored in the memory 46 and the outputs of the photodiodes 36 and 38 to determine the reflectance RX1 of near infrared light of wavelength λ1 and the near red of wavelength λ2. The reflectance RX2 of external light is calculated, and the reflectances RX1 and RX2 and the coefficient values an, bn, cn are further substituted into the equation (4) to calculate the sugar content SX. The calculated and calculated sugar content is identified in five stages, and one of the LEDs 3a to 3e of the display unit 3 is turned on and output,
Further, it is output as a digital signal from the output terminal 4, and is processed by an information processing device (not shown) as necessary.

5 to 7 show a third embodiment of the present invention. This embodiment also uses a xenon discharge tube as a light source for near infrared light, and when detecting reflected light,
It is configured to detect the average value of reflected light using an integrating sphere.

FIG. 5 is an external view of a sugar content meter embodying the present invention. In the figure, 51 is a main body, 52 is a probe, 53 is a connection cable, and 54 is a display section for digitally displaying the sugar content.
It is composed of a liquid crystal display element. S1 is a power switch, S2 is a measurement switch, and 55 is an output terminal for outputting the measurement result as a digital signal.

FIG. 6 is a sectional view showing the structure of the probe 52. Reference numeral 61 is a xenon discharge tube, 62 is a reflection mirror, and 6 is a reflection mirror.
3 and 65 are photo diodes for monitoring the light emission amount of the xenon discharge tube, and 64 and 66 are photo diodes 63 and 65.
Of the filter, which transmits light of wavelength λ1 and wavelength λ2, respectively. 67 is an integrating sphere, 68,
Reference numeral 70 is a photo diode for detecting reflected light provided on the integrating sphere 67, and 69 and 71 are photo diodes 68 and 70.
In the filter disposed on the light receiving surface of the filter, the filter 69 has a characteristic of selectively transmitting near infrared light of wavelength λ1 and the filter 71 has a characteristic of selectively transmitting near infrared light of wavelength λ2.

FIG. 7 shows a block diagram of the measuring circuit of the third embodiment. Since the portion of the probe 52 shown by the broken line in the figure has the configuration shown in FIG. 6, its explanation is omitted. 75 to 7
8 are photo diodes 63, 65, 68, and 70, respectively.
, 79 is a multiplexer, 80
Is an A / D converter, 82 is a light emission control circuit for controlling the light emission of the xenon discharge tube 61, and 83 is the coefficient value a of the formula (4).
Memory storing n, bn, cn, etc., 81 is a CPU
Then, the control of the whole sugar content meter and the photo diode 63, 6
5, the reflectance is calculated from the amount of light emitted from the xenon discharge tube 61 detected in 5 and the amount of reflected light detected in the photodiodes 68 and 70, and the sugar content is calculated by performing the calculation based on the equation (4) described above. Then, the measurement result is output to the display unit 54.
In addition, the measurement result is output from the output terminal 55 to an external information processing device (not shown). A constant voltage circuit 84 stabilizes the electric power of the battery E to a constant voltage and supplies it to each circuit element.

Next, the operation of the measuring circuit will be described. When the power switch S1 is turned on and the measurement switch S2 is closed after the preparation for the measurement operation is completed, a control signal is sent from the CPU 81 to the light emission control circuit 82, the xenon discharge tube 61 emits light, and the subject passes through the integrating sphere 67. It is projected on M. At this time, the amount of light emitted from the xenon discharge tube 61 is
Detected by the amplifiers 63 and 65, and the amplifiers 75 and 76,
CP via multiplexer 79 and A / D converter 80
Input to U81. The reflected light reflected by the subject M is diffusely reflected in the integrating sphere 67, and the near infrared light having the wavelength λ1 is filtered by the filter 6
9 and is detected by the photo diode 68, and the wavelength λ
The near-infrared light of No. 2 passes through the filter 71 and the photodiode-
The signal is detected by the mode 70 and is input to the CPU 81 via the amplifiers 77 and 78, the multiplexer 79, and the A / D converter 80, respectively.

The CPU 81 uses the photo diodes 63 and 6
From the outputs of 5, 68 and 70, the reflectance RX1 of the near infrared light having the wavelength λ1 and the reflectance RX2 of the near infrared light having the wavelength λ2 are calculated, and the reflectances RX1 and RX2, and The sugar values SX are calculated by substituting the coefficient values an, bn, and cn. The calculated and calculated sugar content is output to the display unit 54 and digitally displayed, and is also output as a digital signal from the output terminal 55, and is processed by an information processing device (not shown) as necessary.

When a xenon discharge tube is used as a light source, the xenon discharge tube has a wider emission wavelength range than an LED and can be used up to 1100 nm. Therefore, the selection range of the wavelength used for detection is widened and more accurate. It becomes possible to detect high.

Further, in the embodiment shown here, two detection lights having different wavelengths are used as the detection light, but by using a large number of detection lights having different wavelengths, detection with higher accuracy can be performed. Becomes In other words, for 32 melons, 2 points per 1 point, total 64 points, were detected by near-infrared light, and fruit juice was extracted from the flesh under the epidermis at the same measurement point as this and measured with a refractometer. The correlation coefficient with the measured sugar content is as follows. The wavelength selected was a wavelength with a high correlation coefficient by trial and error.

When using two wavelengths: wavelength λ1 = 742 nm, wavelength λ2 = 750 nm, correlation coefficient = 0.828 When using three wavelengths, wavelength λ1 = 750 nm, wavelength λ2 = 766 nm, wavelength λ3 = 958 nm, correlation coefficient = 0.8486 When wavelength is used: wavelength λ1 = 734 nm wavelength λ2 = 830 nm wavelength λ3 = 838 nm wavelength λ4 = 910 nm wavelength λ5 = 926 nm wavelength λ6 = 1030 nm correlation coefficient = 0.924

[0033]

As described above, according to the present invention, since near infrared light is projected onto fruits and vegetables and the sugar content of the fruits and vegetables is measured from the reflectance, all fruits and vegetables can be inspected without damaging them. In this case, since the near-infrared light having a wavelength of 600 to 1100 nm is used as the light source of the near-infrared light, the sugar content can be accurately measured. Moreover, since a light emitting diode or a xenon discharge tube is used for the light source,
The device can be made small so that it can be carried, and can be easily used in a field such as a field.

[Brief description of drawings]

FIG. 1 is a perspective view showing the outer appearance of a first embodiment to which the present invention is applied.

FIG. 2 is a sectional view showing the structure of the probe of the first embodiment.

FIG. 3 is a block diagram of the measurement circuit according to the first embodiment.

FIG. 4 is a block diagram of the measurement circuit of the second embodiment.

FIG. 5 is a perspective view showing an appearance of a third embodiment to which the invention is applied.

FIG. 6 is a sectional view showing the structure of the probe of the third embodiment.

FIG. 7 is a block diagram of the measurement circuit of the third embodiment.

[Explanation of symbols]

10, 11: Light emitting diode 13, 14, 15, 31, 32, 33: Optical fiber 12, 36, 38, 63, 65, 68, 70: Photodiode 30, 61: Xenon discharge tube 35, 37 , 64, 66, 69, 71: Filter 67: Integrating sphere 3, 54: Display unit M: Subject

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Kosuke Nagai 1087-188 Futaba-cho, Ono City, Hyogo Prefecture (72) Masamichi Oshiro 1-5 Dojimahama, Kita-ku, Osaka Osaka Sanryo Building Mitsubishi Corporation (72) Inventor Satoshi Aoyama 2-3-13 Azuchi-cho, Chuo-ku, Osaka City Osaka International Building Minolta Camera Co., Ltd.

Claims (3)

[Claims] 1. A light projecting means having a light source for projecting light onto a subject, and a light detecting means for detecting light reflected by the subject, wherein the light is projected based on the reflectance of at least two different wavelengths of light. A sugar content meter for detecting the sugar content of a sample, wherein the light projected onto the object is light having at least two wavelengths different in wavelength selected from wavelengths of 1100 nm or less. 2. The sugar content meter according to claim 1, wherein the light source of the light projection means is a light emitting diode. 3. The sugar content meter according to claim 1, wherein the light source of the light projection means is a xenon discharge tube.