JP2001013070A - Fruit component non-destructive measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lightweight small-sized fruit component non-destructive measuring device usable on the production site. SOLUTION: An LD(laser diode) 10 outputting light with a certain wavelength (or oscillation frequency), an oscillation circuit 14 applying current modulation to the LD 10 to modulate the certain wavelength (or oscillation frequency), a first beam splitter 18 for splitting the output light from the LD, a measuring photosensor 36 receiving a part of the light split by the first beam splitter 18 through fruit to be measured to detect absorbancy, at least one photosensor 22 receiving the other part of the light split by the first beam splitter 18 through at least one BPF 21 having a predetermined center wavelength, a timing circuit 30 sensing the timing receiving the light through the BPF of the photosensor to generate a timing signal, a sample holding circuit responding to the timing signal from the timing circuit 30 to hold the absorbancy detected by the measuring photosensor as a sample and an operation circuit 42 operating the absorbancy held to the sample holding circuit to calculate a fruit component are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-destructive fruit component measuring instrument, and more particularly to a fruit producer which measures a fruit component (especially, sugar content) before shipment of fruit, that is, before removing the fruit component, or a fruit component at a distribution stage. The present invention relates to a portable non-destructive measuring instrument using near infrared spectroscopy technology capable of measuring and displaying. The present invention will be described below in connection with the measurement of the sugar content because the measurement result of the sugar content among the components of the fruit is highly useful, but the present invention is not limited to the measurement of the sugar content only.

[0002]

2. Description of the Related Art Conventionally, non-destructive measurement of sugar content of fruits has been carried out by measuring the color of the skin using visible light and estimating the degree of juku from the color, or by utilizing the near-infrared absorption phenomenon. There is a diffuse reflection method in which light is projected and received in the direction and the light diffusely reflected in the fruit is measured, or a method of measuring the amount of transmitted light for a fruit having a thick skin.

[0003]

In the color measurement described above,
There is no correlation between color and sugar content.
Even if the fruit holds, the color is greatly affected by the quality, cultivation conditions, and the like, so that improvement in measurement accuracy cannot be expected.

[0004] In the diffusion method and the transmission method, the sugar content can be measured with high accuracy. However, since a halogen lamp (which generates broadband light) or the like is used as a light source for creating an absorption line, much power is consumed. It is a large-scale device from the heat generation and the power supply unit, and is used only in fruit sorting facilities.

Accordingly, an object of the present invention is to provide a light-weight and small-sized non-destructive fruit component measuring instrument which can be used in a production site.

It is another object of the present invention to provide a portable, lightweight, compact, non-destructive fruit component meter that consumes less power and is therefore battery powered.

[0007]

In order to achieve the above-mentioned object, the present invention provides an LD (laser diode) for outputting light of a certain wavelength (or oscillation frequency), and current-modulating the LD. An oscillation circuit for modulating a certain wavelength (or oscillation frequency), a first beam splitter for splitting the output light from the LD, and light received through a fruit to be measured for a part of the light split by the first beam splitter A light receiving element for measuring absorbance, and at least one light receiving element for receiving another part of the light split by the first beam splitter through at least one band pass filter (BPF) having a predetermined center wavelength. A timing circuit for sensing a timing at which the light receiving element receives light through the BPF and generating a timing signal; and a timing from the timing circuit. A sample-and-hold circuit that samples and holds the absorbance detected by the measurement light-receiving element in response to a signal, and a calculation circuit that calculates the fruit component by calculating the absorbance held by the sample-and-hold circuit. It adopts a characteristic non-destructive fruit component measuring instrument.

Further, the present invention provides a non-destructive measurement of a fruit component by measuring the absorbance of the fruit using an LD (laser diode) and measuring the fruit diameter to remove the influence of the size of the fruit. A U-shaped frame having a cross section having opposed first and second legs for holding the fruit, and an elasticity disposed on the first leg for holding a surface of the fruit. A first attachment, a light-receiving element disposed on the first leg for receiving light through fruit, and a light-receiving element disposed on the second leg and biased in a direction approaching the first leg. A movable rod, a resilient second attachment attached to a tip of the movable rod for holding a fruit surface, a potentiometer engaged with the movable rod to detect a position thereof, and a movable rod. take Vignetting in, LD to the tip of the movable rod
And a non-destructive fruit component measuring device comprising: an optical fiber for guiding output light from the fruit component.

[0009]

Next, embodiments of the present invention will be described. FIG. 1 is a graph for explaining the principle of the non-destructive measuring device of the present invention, FIG. 2 is a circuit block diagram of the non-destructive measuring device of the present invention, and FIG. It is a figure which shows the fruit contact part of a container, and a light source and a calculation part.

First, the principle of the nondestructive measuring device of the present invention will be described. In the non-destructive measuring device of the present invention, the sugar content of the fruit is measured non-destructively.
The fruit is irradiated with near-infrared rays, which have a relatively high transmission power, in the short wavelength region, and the absorbance is obtained from the amount of transmitted light. The absorbance (or differential value) is corrected according to the size of the fruit to determine the sweetness. The index related to is calculated.

In order to obtain light of a specific narrow band wavelength,
Until now, a plurality of absorption lines required by a bandpass filter were created from a tungsten lamp or a light source having a relatively wide wavelength range having an emission spectrum also in the near-infrared region. The light source used is to create an absorption line of a required wavelength using an inexpensive laser diode (hereinafter referred to as LD).

The LD is characterized by its extremely good coherence and, when used as a light source for spectroscopic analysis, has extremely good molecular selectivity and can be reduced in weight and size. However, the oscillation wavelength is sensitive to the ambient temperature and the applied voltage, and is unstable. In other words, the oscillation wavelength is not constant but constantly changes due to the influence of the ambient temperature and the applied voltage. From this, conversely, by controlling the applied voltage, the change in the oscillation wavelength is offset, and the desired wavelength is obtained.

In the present invention, by modulating the current flowing through the LD at a certain frequency (10 KHz in this embodiment),
As shown in FIG. 1A, the desired wavelength is obtained by changing the oscillation wavelength of the LD in the range of Wλ (substantially in the range of λ1 to λ2). Note that Wλ is determined by the characteristics of the LD.

Within the range of Wλ in the LD oscillation optical path, for example,
A bandpass filter (BPF) having two transmission center wavelengths λ1 and λ2 is installed, and a light receiving element that generates a voltage when receiving light on the optical path on the opposite side of the LD is installed. In this state, it can be seen that the LD oscillation wavelength when there is a light receiving sensitivity is the wavelength of λ1 or λ2.

Next, the graph shown in FIG. 1A will be described. FIG. 1A shows the characteristics of the transmittance of the BPF with respect to the wavelength of the LD. In FIG. 1A, the horizontal axis represents the wavelength of the LD, and the vertical axis represents the transmittance of the BPF. In the embodiment shown in FIG. 1A, an LD having a center wavelength λc is used and 1
The current modulation is performed at 0 KHz. Then, L
When the light from D passes through a band-pass filter (BPF) having two transmission center wavelengths λ1 and λ2, for example, at a specific timing, the BPF converts the light from the LD into a transmittance based on the BPF characteristic of the filter. Will be transmitted.

Next, the graph shown in FIG. 1B will be described. FIG. 1b shows the spectrum of the substance, in which the horizontal axis represents the wavelength and the vertical axis represents the absorbance. A substance has a spectral distribution unique to that substance. That is, a substance has a different absorbance with respect to wavelength depending on its composition, and exhibits a specific absorbance characteristic with respect to wavelength. Taking FIG. 1b as an example, this material has a peak in absorbance at the wavelength λ1, has a valley of absorbance above λc, and again has a peak in absorbance above λ2. From this, it is possible to predict the composition of this substance and the amount of components contained in the substance.

Further, the absorbance at a specific wavelength of a substance changes depending on the amount of a specific component contained therein. For example,
If the substance was fruit melon, wavelengths 880, 910,
It has an absorption line (where the absorbance is large) in the near-infrared band at 930 nm, and the absorbance of the absorption line depends on the amount of sugar content of melon. Therefore, the sugar content of the melon can be estimated by measuring the absorbance at 880, 910, and 930 nm of the fruit melon.

Next, a circuit block of the nondestructive measuring instrument of the present invention shown in FIG. 2 will be described. In FIG. 2, an LD (laser diode) 10 is oscillated by a current supplied from a mixer (MIX) 16. In the mixer 16, the constant current supplied from the current source 12, the current from the oscillator 14, and the offset current are mixed and supplied to the LD 10.
The current source 12 supplies a current necessary for oscillating the LD, and the oscillator 14 modulates the oscillation frequency (in other words, the wavelength) within a predetermined range by applying current modulation to the oscillation frequency of the LD. The offset current is for setting the oscillation frequency to a desired frequency at an initial stage.

The light from the LD 10 is directed to a first beam splitter (half mirror) 18 and split into two in the first beam splitter 18. One of the divided beams is directed to the second beam splitter 20, and is further divided into two by the second beam splitter 20. One of the divided light is input to a BPF (bandpass filter) 21 having a center wavelength of λ1. When the wavelength of the input light substantially matches λ1, the input is sensed by a photodiode 22. That is, the timing when the wavelength of the LD 10 becomes λ1 can be detected by the photodiode 22. The other is input to a BPF (Band Pass Filter) 23 having a center wavelength of λ2. When the wavelength of the input light substantially matches λ2, the input is sensed by a photodiode 24. That is, the timing when the wavelength of the LD 10 becomes λ2 can be detected by the photodiode 22.

Since the signals detected by the photodiodes 22 and 24 are weak, the signals are detected by the preamplifiers 26 and 28, respectively.
And is input to the timing circuit 30. The timing circuit 30 is configured to output a signal at the timing when light is input to the photodiodes 22 and 24. The signal is input to a data lock-in circuit 40 described later, and the light generated by the LD 10 is output. Data input to the data lock-in circuit is sampled and held at the timing when the center wavelength is λ1 or λ2.

On the other hand, the other light split by the first beam splitter 18 is guided to the surface of the fruit 50 by the optical fiber 32, and the light passes through the fruit 50. The transmitted light is received by a light receiving element (for example, a photodiode) 36 with a light amount corresponding to the absorbance of the fruit 50, converted into a voltage, and amplified by a preamplifier 38. The amplified signal is input to the data lock-in circuit 40, and the data is held at the input timing of the timing signal input from the timing circuit 30. That is, the center wavelengths λ1 and λ of light
When 2, the data is held. The held data is input to the arithmetic circuit 42, and after an arithmetic operation described later is performed, the result is output and displayed.

Next, the operation of the above-described circuit will be supplemented. LD
Reference numeral 10 generates light whose center wavelength determined by the current source 12 and the offset is modulated by current modulation by the oscillator 14. The first beam splitter 18 is provided on the optical path from the LD 10.
Is arranged, and one of the light emitted from the LD 10 is the first light.
The other of the emitted light is directed from the first beam splitter 18 to the second beam splitter 20 through the beep splitter 18 toward the fruit 50 to be measured. The light incident on the second beam splitter 20 is reflected and transmitted,
The light passes through the BPF 21 having the center wavelength λ1 and the BPF 23 having the center wavelength λ2, respectively.
Light is received at 2, 24. When the light receiving element 22 has sensitivity, it means that the LD 10 oscillates at the wavelength of λ1. Therefore, if the value of the oscillation voltage of the measuring light receiving element 36 when the light receiving element 22 has sensitivity to λ1 is locked (held), it becomes the transmitted light amount for the wavelength of λ1.

When the light receiving element 24 has sensitivity,
This means that the LD 10 oscillates at the wavelength of λ2. Therefore, if the value of the oscillation voltage of the measuring light receiving element 36 when the light receiving element 24 has sensitivity to λ2 is locked (held), it becomes the transmitted light amount for the wavelength of λ2. Actually, since the output signals from the light receiving elements 22 and 24 are extremely weak, the signals are amplified by the preamplifiers 26 and 28, respectively, and the analog data is amplified by the timing circuit 30 at the timing when the light receiving elements are sensitive. Is locked by a data lock-in (sample hold) circuit 40. This value is digitally converted by an AD converter (not shown) so as to be processed digitally.
Is input to

Although the current modulation of the LD 10 is as low as about 10 KHz, the number of times of sampling can be two with one modulation wave.
Since 20,000 samplings can be performed per second, data can be stabilized by the time integration method, and high data reliability can be obtained because the data is strong against ambient noise.

Also, since the LD changes its wavelength but its amplitude due to current modulation, the LD is affected by disturbance light such as sunlight when the measuring instrument is used outdoors. If there is a proper correlation, it is easy to identify that the measurement signal is valid, otherwise the measurement result is invalid, so that there is no problem in use.

If the transmitted light of the measuring light receiving element 36 between λ1 and λ2 is continuously measured in addition to (or in place of) the transmitted light at λ1 and λ2, a continuous transmission spectrum of the fruit during that period is also obtained. Can be

Since 100% of the transmitted light means a state where there is no absorption for the wavelength, in this state (for example, by irradiating a laser beam from the first beam splitter 18 directly to the light receiving element 36 without arranging fruits). ), Calibrate the measurement system.

Next, standardization of the fruit diameter will be described. Lambert's law shows that the absorbance is proportional to the diameter of the fruit. Therefore, for example, it is necessary to remove the component of the size (diameter) of the fruit with respect to the absorbance with respect to the obtained sugar content.

Therefore, a mechanism for measuring the diameter of the fruit and others will be described with reference to FIG. FIG. 3 is a diagram showing a fruit contact portion (a portion for measuring the diameter of the fruit) and a light source / calculating portion (portable portion) in the destructible measuring instrument of the present invention. FIG. 3a shows the fruit contact portion, and FIG. Indicates a light source / arithmetic unit.

In FIG. 3a, the fruit contact portion has a frame 52 having a U-shaped cross section. A light receiving element 36 is attached to one leg (right side in the figure) of the frame 52 so as to protrude toward the other leg.
A rubber attachment 53 is attached to the leg so as not to disturb the light reception. The rubber attachment 53 is formed in a concave shape so as to match the spherical shape of the surface of the fruit whose diameter is to be measured.

The light receiving element 36 is connected to a preamplifier 38, and the preamplifier 38 is connected via a cable 54 to an operation unit (not shown in FIG. 3) disposed inside the portable unit 56.

The other leg of the frame 52 (left side in the figure)
, A hollow movable rod 51 provided with a rack is movably disposed toward one leg or away from the leg. A rubber attachment 57 is attached to the tip of the movable rod 51, and the rubber attachment 57 is the same as the rubber attachment 5 described above.
Similarly to 3, it is formed in a concave shape so as to match the spherical shape of the surface of the fruit whose diameter is to be measured.

The tip of the movable rod 51 and the frame 5
A spring 55 is arranged between the insides of the two legs, and urges the movable rod 51 toward the other leg. When measuring the diameter of the fruit 50, the movable rod 51 is pulled by hand against the force of the spring 55, and the fruit 50 is sandwiched between the two rubber attachments 53 and 57. The fruit 50 is held between the rubber attachments 53 and 57 by the urging force of the spring by releasing the hand.

The pinion of the potentiometer 34 is engaged with the rack of the movable rod 51, and the position of the movable rod 51 can be determined from the measured value of the potentiometer. Therefore, the diameter of the fruit 50 sandwiched between the fixed rubber attachment 53 and the movable rubber attachment 57 is obtained from the position of the movable rod 51 to which the movable rubber attachment 57 is attached, that is, the measured value of the potentiometer 34. Can be

An optical fiber, for example, a silica-based fiber 32 is guided to the tip of the movable rod 51 through the hollow interior. The quartz fiber 32 is connected to the first beam splitter 18 disposed inside the portable unit 56 via a cable 54.
(See FIG. 2, not shown in FIG. 3).

The portable section 56 has a display section 5 on the surface of the case.
The display unit 8 can display, for example, the sugar content of fruits. A shoulder belt 60 is attached to the portable unit 56, and when used in a portable manner, the measuring instrument can be used by hanging it on the shoulder. Since the measuring instrument of the present invention can reduce power consumption, a battery can be used as a power supply.

Next, an index indicating sweetness will be described.
The center wavelengths are λ1, λ2,..., And the absorbance corrected at that time (ie, divided by the fruit diameter) is L (λ1), L
(Λ2),..., The index C indicating sweetness is expressed as follows. C = K0 + K1L (λ1) + K2L (λ2),... (1) Here, K0, K1, K2,.
(Λ1) is the corrected absorbance log at wavelength λ1 nm
(1 / T). Here, T = It / Io, where It is the amount of transmitted light, and Io is the amount of incident light.

The calibration curve and the proportionality constant to be used are determined depending on the kind of fruit, respectively. A typical method for obtaining the calibration curve is to obtain the absorbance at the wavelength expected from the sample, and to correct the value by excluding the size component. The sweetness C is calculated from the absorbance using the above equation obtained by the multiple regression analysis. An equation having the smallest error between the estimated value and the actually measured value (that is, the wavelength of the absorption line) is defined as a calibration curve. The result can be output in real time by incorporating the obtained calibration curve into the calculation unit of the measuring instrument.

The actual calibration curve is the absorbance log (1
/ Tλ) as well as the first derivative of the absorbance dlo
g (1 / Tλ) or the second derivative d2log (1 / Tλ)
λ) may be used.

[0040]

As described above, according to the present invention,
A light and small fruit component non-destructive measuring instrument that can be used in production sites can be obtained.

In addition, a portable light-weight, compact, non-destructive fruit component measuring instrument that consumes less power and is battery-operated can be obtained.

[Brief description of the drawings]

FIG. 1 is a graph for explaining the principle of a nondestructive measuring instrument according to the present invention.

FIG. 2 is a circuit block diagram of the nondestructive measuring device of the present invention.

FIG. 3 is a diagram showing a fruit contact portion and a light source / calculation portion of the nondestructive measuring device of the present invention.

[Explanation of symbols]

Reference Signs List 10 LD (laser diode) 12 Current source 14 Oscillator 16 Mixer 18, 20 First and second beam splitter (half mirror) 21, 23 BPF 22, 24 Light receiving element 26, 28 Preamplifier 30 Timing circuit 32 Optical fiber 34 Potentiometer 36 Measurement Light receiving element for 38 38 Preamplifier 40 Data lock-in circuit 42 Arithmetic circuit 50 Fruit 52 Frame 51 Movable rod 53, 57 Attachment 54 Optical fiber 56 Portable section 58 Display section 60 Shoulder belt

Claims (9)

[Claims] An LD (laser diode) for outputting light of a certain wavelength (or oscillation frequency), an oscillation circuit for applying current modulation to the LD to modulate a certain wavelength (or oscillation frequency), and the LD A first beam splitter for splitting the output light from the first beam splitter; a light receiving element for measurement for receiving a part of the light split by the first beam splitter through a fruit to be measured and detecting an absorbance; and the first beam splitter. At least one light receiving element for receiving another part of the light divided by the above through at least one BPF (band-pass filter) having a predetermined center wavelength, and detecting a timing at which the light receiving element receives the light through the BPF; And a absorbance detected by the light receiving element for measurement in response to a timing signal from the timing circuit. A sample hold circuit for sample holding, fruit components nondestructive measuring instrument and having a an arithmetic circuit for calculating a component of the fruit by calculating the hold absorbance in the sample and hold circuit. 2. The fruit component nondestructive measuring device according to claim 1, wherein the fruit component to be measured is a sugar content, and the transmission band of the BPF is a band related to the absorbance of the sugar content. Non-destructive measuring instrument. 3. The non-destructive fruit component measuring device according to claim 1, wherein a second beam splitter splits another part of the light split by the first beam splitter, and light split by the second beam splitter. A first light receiving element that receives a part of the light through a first BPF (bandpass filter) having a first center wavelength, and another part of the light that is split by the second beam splitter has a second center wavelength. A second light receiving element for receiving light through a 2BPF (bandpass filter). 4. The non-destructive fruit component measuring device according to claim 3, wherein the timing circuit is connected to the first light receiving element and the second light receiving element.
A non-destructive fruit component measuring device, wherein a timing signal is generated from each timing detected by a light receiving element. 5. The nondestructive fruit component measuring device according to claim 3, further comprising at least one beam splitter, BPF, and light receiving element in addition to the second beam splitter, the second BPF, and the second light receiving element. A non-destructive fruit component measuring device for detecting at least one other timing. 6. The non-destructive fruit component measuring device according to claim 1, wherein the LD, the oscillation circuit, the first beam splitter, the light receiving element for measurement, and the sample hold circuit are used to reduce the absorbance of the fruit. A non-destructive fruit component measuring instrument characterized by sampling over time and obtaining an almost continuous transmission spectrum of the fruit. 7. An LD (laser diode) for outputting light of a certain wavelength (or oscillation frequency), an oscillation circuit for applying current modulation to the LD and modulating a certain wavelength (or oscillation frequency), and the LD A light receiving element for receiving light from the fruit to be measured, and detecting the absorbance, and a sample and hold circuit for sampling and holding the absorbance detected by the light receiving element for measurement at short time intervals. A non-destructive fruit component measuring instrument characterized by obtaining a substantially continuous spectrum from the absorbance held in the sample hold circuit. 8. A fruit component non-destructive measuring instrument for measuring the absorbance of fruit using an LD (laser diode) and measuring the fruit diameter to remove the influence of the size of the fruit. A frame having a U-shaped cross section having first and second legs opposed to each other, and an elastic first attachment arranged on the first leg to hold a surface of the fruit. A light-receiving element disposed on the first leg for receiving light through fruit; a movable rod disposed on the second leg and biased in a direction approaching the first leg; A resilient second attachment attached to the tip of the movable rod for holding a fruit surface; a potentiometer engaging with the movable rod to detect its position; An optical fiber for guiding output light from an LD to a tip of a rod; and a non-destructive fruit component measuring device, characterized in that: 9. The non-destructive fruit component measuring device according to claim 8, further comprising a portable unit including an optical system and an electric system therein, wherein the portable unit electrically connects the light receiving element and the optical fiber through a cable. A non-destructive fruit component measuring device wherein transmission and optical transmission are performed.