JPH0142027Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a chlorophyll meter that optically measures the amount of chlorophyll in fresh leaves.

The spectral characteristics of the scattered absorption of fresh leaves are almost the same regardless of the type of plant, and it is clear that the maximum absorption due to chlorophyll is around 670 nm, and the stable minimum absorption that is not affected by chlorophyll is on the longer wavelength side than 750 nm. It's getting old. (See Figure 1).

A method for measuring the amount of chlorophyll using this optical property of chlorophyll is described in
the Crop Science Society of Japan, Volume 17,
Those described on pages 158 to 162 are known.

This conventional chlorophyll meter is equipped with two interference filters whose main wavelengths are 670nm and 750nm, respectively.The light that has passed through the leaves is first separated into components in the long wavelength range through the interference filters whose main wavelength is 750nm. The amount of transmitted light of this long wavelength component is measured with a CdS photoconductive cell, and the instrument is set with this case as zero.Then, the interference filter is replaced with an interference filter whose main wavelength is 670 nm, and the transmitted light is It passes through an interference filter with a main wavelength of 670nm and separates the light into components in the short wavelength range, then measures the amount of transmitted light of the components in the short wavelength range with a CdS photoconductive cell, and displays this value on an instrument. When measuring the amount of chlorophyll in fresh leaves using this conventional chlorophyll meter, there is an advantage that the amount of chlorophyll can be measured by comparing the maximum transmitted light amount value and the minimum transmitted light amount value. The measurement has to be performed twice, which takes time, and two types of interference filters are replaceably placed on the optical axis of the light transmitted from the sample leaf to the CdS photoconductive cell. The mechanical structure is complicated because the interference filter has to be replaced, and the reproducibility is poor, and the circuit is also complicated because two measurement circuits are required to be switched when replacing this interference filter. It has some drawbacks.

Therefore, an object of the present invention is to provide a chlorophyll meter that can quickly and easily measure the amount of chlorophyll in fresh leaves and has an extremely simple structure.

In order to achieve the above objective, the present invention divides the light transmitted through the leaves into a component in the short wavelength range whose transmission amount changes depending on the chlorophyll, and a component that does not change. It was decided to measure the amount of light at the same time.

That is, the chlorophyll meter according to the present invention comprises: a sample support part for supporting plant leaves; a light source that shines light on the leaves supported by the sample support part and transmits a part of the light; The first filter transmits only components with a wavelength of 660 nm or more out of the light that passes through the leaves.
a second cut filter that transmits only components having a wavelength of 760 nm or more of the light transmitted through the leaf, and a GaAsP-based photo sensor arranged to receive only the light transmitted by the first cut filter. a first photoelectric conversion element consisting of a diode, a second photoelectric conversion element consisting of a silicon photodiode arranged to receive only the transmitted light of the second cut filter, and the first photoelectric conversion element
and the amount of light in the wavelength range of 660 to 690 nm measured simultaneously by the second photoelectric conversion element and the amount of light in the wavelength range of 760 to 690 nm.
This invention is characterized by comprising circuit means for directly deriving the amount of chlorophyll in the leaf based on the difference between the amount of light in the wavelength range of 1100 nm and the amount of light in the wavelength range of 1100 nm.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

Figure 2 shows the overall structure of the chlorophyll meter according to the present invention.As is clear from this figure, the chlorophyll meter has a pistol-shaped main body 1 to improve portability and enable one-handed operation. There is. A casing 3 of a light source 2 is attached to the front part of this pistol-shaped main body 1 so as to be able to move toward and away from the main body 1. The casing 3 is moved into and out of contact with the main body 1 by operating the trigger 4. When the trigger 4 is pulled and the casing 3 comes into close contact with the front surface 5 of the main body 1, the casing 3 acts as a sample support for supporting a leaf, which is a sample. In order to make the light source 2 compact and have sufficient light intensity, two tungsten lamps 6 and 7 are arranged vertically facing each other as shown in the figure, and the sample held between the casing 3 and the front surface 5 of the main body 1 is That is, a mirror 8 is provided to efficiently illuminate the leaves with the light from the lamps 6 and 7.

A light receiving section 9 is provided at a position of the main body that receives light from the light source 2 transmitted through a leaf held between the casing 3 and the front surface 5 of the main body 1, that is, at the front of the main body 1. As will be explained in detail later, in this light receiving section 9, the above-mentioned transmitted light is divided into a second component having a predetermined spectral distribution in a long wavelength range where the amount of transmission does not change due to chlorophyll, and this spectral distribution is The light intensity of two different types of light components is measured simultaneously. Behind this light receiving section 9, circuit means 10 is arranged for directly deriving the amount of chlorophyll in the leaf based on the two measured values of the amount of light. The grip portion 11 of the pistol-shaped main body 1 is a power source for the light source 2, circuit means 10, etc., and houses a battery. A power-on button is placed near this area. Also, main body 1
A display section 12 is provided at the rear of the upper surface of the
The amount of chlorophyll (or a value corresponding thereto) derived by the circuit means 10 is preferably displayed digitally.

Next, with reference to FIG. 3, the light receiving section 9 will be explained in detail.

The light receiving unit 9 has a substantially cubic casing 13, and openings 14, 15, and 16 are provided in the front, rear, and bottom surfaces of the casing 13, respectively.
is formed. An opening 14 disposed on the front surface of the casing 13 is for guiding transmitted light from a sample, ie, a leaf 17, disposed between the light source 2 and the light receiving section 9 into the casing 13. Also,
Openings 15 and 16 provided on the back and bottom
There are sharp cut filters 18 and 19 at the rear of the
and photoelectric conversion elements 20 and 21 are provided. These sharp cut filters 18,1
9 and the photoelectric conversion elements 20 and 21, the sharp cut filter 18 and the photoelectric conversion element 20
is used to measure the amount of light of components with a predetermined spectral distribution in the short wavelength range whose transmission amount changes depending on the chlorophyll in the leaf, and the sharp cut filter 1
9 and a photoelectric conversion element 21 are used to measure the amount of light of a component having a predetermined spectral distribution in a long wavelength region whose transmission amount does not change due to chlorophyll. leaf 17
The transmitted light from the sharp cut filter 18
A half mirror 22 is provided within the casing 13 as shown in the figure to split the transmitted light so as to direct it to the set of photoelectric conversion elements 20 and the set of sharp cut filters 19 and photoelectric conversion elements 21, respectively. That is, the sharp cut filter 18 and the photoelectric conversion element 20 are
The sharp cut filter 19 and the photoelectric conversion element 21 are arranged on the optical axis of the light transmitted through the half mirror 22, and the sharp cut filter 19 and the photoelectric conversion element 21 are arranged on the optical axis of the light reflected by the half mirror 22.

Here, with reference to FIG. 4, the sharp cut filters 18, 19 and the photoelectric conversion elements 20, 2
The effect of No. 1 will be explained.

In the present invention, the spectral distribution of light components in the long wavelength range is set to 760 to 1100 nm, and the spectral distribution of light components in the short wavelength range is set to 660 to 690 nm. The reason why the spectral distribution of the light components has a certain width in this way is to increase the overall amount of light and make the work more efficient and accurate.

Sharp cut filter 18 for short wavelength range
In order to define the limit D on the short wavelength side of the spectral distribution of components in the short wavelength region, a material that substantially transmits only components of 660 nm or more is used. In order to define the long wavelength limit C of this spectral distribution, the spectral characteristics of the photoelectric conversion element are used, and in reality GaAsP has a relative sensitivity of about 5% to light with a wavelength of 680 nm.
A photodiode of the same type is used. That is,
In FIG. 4, the amount of light of a light component having a spectral distribution between dashed-dotted lines C and D is measured by the photoelectric conversion element 20. In FIG.

On the other hand, the sharp cut filter 19 for the long wavelength region is used to define the limit B on the short wavelength side of the spectral distribution of the components in the long wavelength region, so that a filter that substantially transmits only components of 760 nm or more is used. In order to define the limit A on the long wavelength side of this spectral distribution, the spectral characteristics of the photoelectric conversion element are used as in the case of the short wavelength region. As a photoelectric conversion element for a long wavelength range, a silicon photodiode is used, which has a wavelength of 1050 nm at which the relative sensitivity is about 5%. That is, the fourth
In the figure, the amount of light of a light component having a spectral distribution between two-dot chain lines A and B is measured by the photoelectric conversion element 21. The following description will be made assuming that the measured value in the long wavelength range is "x" and the measured value in the short wavelength range is "y".

The outputs y and x of the photoelectric conversion elements 20 and 21 are inputted to a division circuit 23 and divided into a value of y/x. The output of this division circuit 23 is the logarithmic conversion circuit 2
4, and is converted into a log value by the logarithmic conversion circuit 24.
gy/x. Since logy/x=logy-logx, the output logy/x of the logarithmic conversion circuit 24 has a value corresponding to the amount of chlorophyll in the leaf. In other words, the amount of chlorophyll is calculated based on the difference between the light amount of the short wavelength component of the light transmitted from the leaf, whose transmission amount changes depending on the chlorophyll, and the light amount of the long wavelength component, whose transmission amount does not change depending on the chlorophyll. This means that it can be measured directly. Division circuit 23
and the logarithmic conversion circuit 24 are included in the circuit means 10 shown in FIG.

The output terminal of the logarithmic conversion circuit 24 is connected to the display section 12, and the value corresponding to logy/x is displayed. This value allows the operator to know the amount of chlorophyll in the leaf.

Note that, as shown in the figure, it is desirable to arrange a diffuser plate 25 and an aperture 26 between the leaf 17 and the light source 2.

Next, with reference to FIG. 5, another modification of the light receiving section 9 will be described.

In the modified example of the light receiving section 9 shown in FIG. 5, two sets of sharp cut filters and photoelectric conversion elements 18B and 2 as shown in FIG.
0B, 19B, and 21B are arranged in parallel vertically or horizontally on the back surface of the casing 13. Therefore, the openings 15 and 16 are also arranged in front of the sharp cut filter and the photoelectric conversion element. In addition, the light transmitted through the leaf 17 is transferred to the casing 1.
A diffusion plate 28 is disposed at the rear of the opening 14 for guiding the light into the photoelectric conversion elements 3, so that the transmitted light sufficiently reaches the two photoelectric conversion elements 20B and 21B. With such a structure, a half mirror is not required, so the structure becomes extremely simple and manufacturing becomes easy.

According to the chlorophyll meter of the present invention, after turning on the power, just by supporting the sample leaf on the support part, the value corresponding to the amount of chlorophyll in the leaf can be directly read on the display part. Quantities can be determined very quickly and easily. Furthermore, since the light being compared is the spectrum from the same light, changes in the leaf over time due to exposure to light will not affect the measurement, so accurate measurements can be made. Furthermore, since the short wavelength and long wavelength spectra used for measurement have a relatively wide spectral distribution, measurements can be made in bright conditions, and the transmission density
It has the advantage of being able to measure up to around 2.0.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the wavelength of transmitted light and the transmitted density of leaves, Figure 2 is a side view of the external appearance of a chlorophyll meter according to an embodiment of the present invention, and Figure 3 is an embodiment of the present invention. A schematic diagram of a chlorophyll meter by
A graph similar to FIG. 1 for explaining the spectral characteristics of the spectroscopic optical means used in the chlorophyll meter shown in the figure, and FIG. It is a schematic diagram showing a modification. 2...Light source, 10...Circuit means, 12...Display section, 13...Casing, 14, 15, 16...
Aperture, 17... Leaf, 18, 19... Sharp cut filter, 20, 21... Photoelectric conversion element.

Claims (1)

[Scope of utility model registration request] A sample support part for supporting plant leaves, a light source that illuminates the leaves supported by this sample support part and transmits a portion of the light, and a wavelength of 660 nm or more of the light transmitted through the leaves. a first cut-off filter that transmits only the component of the light transmitted through the leaf, a second cut-off filter that transmits only the component with a wavelength of 760 nm or more of the light transmitted through the leaf, and a second cut-off filter that transmits only the light transmitted by the first cut-off filter. arranged in
a first photoelectric conversion element made of a GaAsP-based photodiode; a second photoelectric conversion element made of a silicon photodiode arranged to receive only the light transmitted through the second cut filter; The amount of light in the wavelength range of 660 to 690 nm measured simultaneously by two photoelectric conversion elements.
A chlorophyll meter comprising circuit means for directly deriving the amount of chlorophyll in the leaf based on the difference between the amount of light in the wavelength range of 760 and 1100 nm.