JP2558898B2 - Optical emission measurement device - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an optical radiation measuring device for precisely measuring an effective amount of optical radiation for growing plants such as photosynthetic effective photon flux density and growth effective amount.

Conventional technology In a plant factory that produces stable, highly efficient and high-quality plants by combining artificial lighting with appropriately controlled natural light, the light emission irradiating the plants is precisely measured according to the amount of effect on the plants. It becomes necessary to do.

The photo-radiation effective for photosynthesis of plants is represented by the amount of photons contained in the wavelength range from 400 nm to 700 nm as shown in FIG. Photosynthetic Photon Flux Density: Photosynthetic photon flux density
Hereinafter abbreviated as PPFD). In addition to the above photosynthesis, the photon flux density ratio in the two wavelength bands of 660 nm and 730 nm is an important factor for plant morphogenesis, especially for growth that influences the shape of plants, and if this ratio is large, it becomes dwarfed. It is said that there is a tendency, and when the ratio is small, there is a tendency for lengthening. In order to measure the effect amount of these light emission, conventionally, for example, in the case of PPFD, in order to adjust the spectral responsivity of the light receiver, a short wavelength cutoff sharp cut filter of 400 nm (hereinafter simply referred to as a sharp cut filter), A color temperature conversion filter and an infrared cut filter were used. This color temperature conversion filter is a filter inserted so as to form a spectral responsivity proportional to the wavelength between 400 nm and 700 nm according to the spectral responsivity of the light receiving element. In addition, the infrared cut filter is 700n
It is inserted to block the spectral responsivity above m.

FIG. 3 shows the spectral responsivity of the PPFD measuring device thus obtained. From FIG. 3, it can be seen that the spectral responsivity from wavelength 400 nm to 700 nm is not exactly proportional to the wavelength, and that the spectral responsivity at 700 nm is poor.

These are due to the fact that the spectral transmittance of the above color temperature conversion filter does not exactly compensate the spectral response of the light receiving element for each wavelength range, and the spectral transmittance of the infrared cut filter is about 600 nm. It starts to fall from the surface and still has a large transmittance even after 700 nm.

Further, regarding the measurement of the photon flux density ratio of 660 nm / 730 nm, it is possible to measure this alone, but there has been no example in which it can be accurately measured with one measuring device together with the PPFD measurement.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the above-mentioned conventional technique, the spectral responsivity of the PPFD measuring device is approximated to a predetermined action function to reduce the measurement error, and how to integrate the optical system of the PPFD measuring device. The issue is how to accurately measure the 660 nm / 730 nm photon flux density ratio using a simple optical system.

Means for Solving the Problems The present invention uses a wavelength proportional silicon photodiode having an absolute responsivity directly proportional to a wavelength at which an absolute responsivity is revealed by a self-calibration method for a light receiver, and a wavelength of 400 nm or 700 nm. By inserting a sharp cut filter in front of the photodetector and calculating the photoelectric output of the photodetector, the PPFD can be precisely measured.

Further, the above optical system is used to replace the 400 nm sharp cut filter and the 700 nm sharp cut filter with a 660 nm interference filter and a 730 nm interference filter, respectively, to calculate the photoelectric output.

By the above means, the sharp cut filter has
Excellent rising characteristics with respect to wavelength, 400 nm and 700
The measurement accuracy of PPFD could be improved by effectively utilizing both wavelengths of nm and using a silicon photodiode whose absolute responsivity was clarified. In addition, PPFD and 660nm / 730nm photon flux density ratio can be measured with high accuracy by simply switching the optical system.

Embodiment An embodiment of the present invention will be described with reference to the drawings. First
In the figure, the incident light is separated into transmitted light and reflected light by the half mirror 1, and the transmitted light enters the silicon photodiode 3 through the 400 nm sharp cut filter 2,
It is photoelectrically converted. On the other hand, the reflected light enters the silicon photodiode 5 through the 700 nm sharp cut filter 4 and is photoelectrically converted. At this time, the apparent spectral responsivities of the silicon photodiodes 3 and 5 are as shown in FIG. As can be seen from FIG. 4, if the arithmetic unit 6 shown in FIG. 1 outputs the difference between the photoelectric outputs of the silicon photodiodes 3 and 5, the PPFD described above can be measured spectroscopically with high accuracy. Become. However, it is desirable that the spectral response of 700 nm or more (including the transmission characteristics of the sharp cut filter) of both silicon photodiodes is completely matched, and two silicon photodiodes that have exactly the same spectral response of 700 nm or more beforehand. It is necessary to prepare a combination of a diode and a sharp cut filter. As a method of reducing the measurement error due to the mismatch of the spectral response of 700 nm or more between the two silicon photodiodes, there is a method of reducing the spectral response of 700 nm or more of both photodiodes by an infrared cut filter. In this case, the infrared cut filter is not shown in FIG. 1, but may be inserted in front of the half mirror 1.

However, it is assumed that the transmittance of the infrared cut filter at a wavelength of 700 nm or less is flat with respect to the wavelength, and a filter whose transmittance starts to decrease from around 600 nm is inappropriate.

The light receiving element for PPFD measurement must have a spectral responsivity proportional to the wavelength in the wavelength range from 400 nm to 700 nm. A silicon photodiode is given as a light receiving element adapted to this.

For silicon photodiodes, a method is known in which the internal quantum efficiency and the surface reflectance are individually measured, and the absolute spectral responsivity is obtained from these measured values.

 This method is called the self-calibration method and is expressed by the following equation.

R (λ) = {1-ρ (λ)} λ ・ ε (λ) / k [A / W] where R (λ) is the absolute correspondence degree and ρ (λ) is the surface reflectance of the silicon photodiode. , Λ is the wavelength, ε (λ) is the internal quantum efficiency, and k is a constant. In this case, the surface reflectance represents the reflectance of the silicon surface of the photodiode with the incident window removed. Therefore, it is appropriate to use a silicon photodiode whose internal quantum efficiency and surface reflectance are as flat as possible in the visible region for PPFD measurement. As can be seen from the above equation, if the surface reflectance and the internal quantum efficiency have no wavelength dependence, the action function that the PPFD should have can be accurately expressed by λ in the above equation. We have confirmed that such a wavelength-proportional silicon photodiode can be realized in some samples in Japan and overseas, so we will use it as a photodetector for PPFD measurement.

By the self-calibration method, ε (λ) and ρ (λ) are measured to obtain R (λ) of the silicon photodiode, and
If the transmittances of the half mirror 1, sharp cut filters 2 and 3 are measured, PPFD for incident light is calibrated from the photoelectric output of a wavelength proportional silicon photodiode with a clear absolute response, such as an external standard light source. You can get it exactly without.

Another embodiment is shown in FIG. In FIG. 5, elements common to those in FIG. 1 are designated by the same reference numerals. The incident light enters the silicon photodiode 3 through the 700 nm sharp cut filter 4 and is photoelectrically converted. On the other hand, the reflected light reflected by the surface of the 700 nm sharp cut filter enters the silicon photodiode 5 through the 400 nm sharp cut filter 2 and is photoelectrically converted. The following operation principle is the same as that in the case of FIG. In FIG. 5, the 700 nm sharp cut filter 4 also serves as the half mirror 1 shown in FIG. 1, so that the number of optical components can be reduced. Instead of the 400 nm sharp cut filter, 7
The 00nm sharp-cut filter has the function of a half mirror because the reflected light from the sharp-cut filter is generally smaller than the transmitted light. This is because by disposing the diode 5, the photocurrents of the two silicon photodiodes are aligned and the direction of S / N during signal transmission is achieved.

Another embodiment is shown in FIG. In FIG. 6 (a), the incident light is split into two optical paths by the half mirror 10 and the mirror 11, and 400 nm and 700 nm are provided for each optical path.
The sharp photo filters 12 and 13 are inserted, and the light passing through these is received by the silicon photodiodes 14 and 15. Here, the 400 nm or 700 nm sharp cut filters 14 and 15 are mounted on one disc turret 16, and their relative positional relationship is symmetrical with respect to the center of rotation as shown in FIG. 6 (b). ing.

On the other hand, at the other position of the disc turret 16, the same 660n as the two sharp cut filters 12 and 13 are provided.
Narrow band transmission filters (hereinafter abbreviated as interference filters) 17 and 18 having center wavelengths at m and 730 nm are mounted as shown in FIG. 6 (b). This allows the disc turret 16
By rotating the silicon photodiodes 14 and 15
Narrow band optical radiation centered at 660 nm and 730 nm is incident on.

The silicon photodiode 14 is operated by the arithmetic unit 19.
If the ratio of the photoelectric signals of 15 and 15 is calculated, the 660 nm / 730 nm photon flux density ratio can be accurately obtained. in this way,
PP by a simple operation of rotating the disc turret
Both FD and 660 nm / 730 nm photon flux density ratio values can be measured in a short time, which is of great practical value.

In the case of the embodiment of FIG. 6 as well, the half mirror 1
If the transmittance or reflectance of 0, the mirror 11 and the interference filters 17 and 18 is measured beforehand, the 660 nm / 730 nm photon flux density for incident light can be calculated from the photoelectric output of a wavelength proportional silicon photodiode with a clear absolute response. The ratio can be accurately determined without calibration of an external standard light source or the like.

Another embodiment is shown in FIG. In FIG. 7, the incident light enters the silicon photodiode 22 through the filters installed in the plurality of filter insertion holes 21 of the disc turret 20. 400 nm or 700 nm in the filter insertion hole 21
The sharp cut filter and the interference filter of 660nm or 730nm are installed, and the stepping motor controller 23
By means of a stepping motor 24 which is rotated by means of a disk turret which is mechanically coupled to this stepping motor 24, the above filters are inserted one after the other into the incident light path.

On the other hand, the control signal from the stepping motor control unit 23 is input to the arithmetic unit 25 so that the photoelectric conversion signal can be stored in the storage unit 26 in association with the insertion of each filter into the incident optical path. Based on the data stored in the storage device 26, the computing device 25 calculates PPFD and 660 nm / 730 nm for incident light.
The photon flux density ratio is calculated and the signal is output.

With such a configuration, in the present embodiment, measurement can be performed with one silicon photodiode, the optical system is small, and the practical value is high. In the case of the embodiment shown in FIG. 7 as well, if the sharp cut filter and the interference filter transmittance are measured in advance, the photoelectric output of the wavelength proportional silicon photodiode with a clear absolute response is calculated to be 660 nm with respect to the incident light. The / 730nm photon flux density ratio can be accurately determined without calibration of an external standard light source.

In the above embodiment, the various filters are switched by rotating the disc turret, but the filters can be switched by sliding the disc turret. In this case, it goes without saying that the filter insertion holes of the disc turret are juxtaposed in the sliding direction. Further, the wavelength of the various filters described in each of the above examples may be slightly fluctuated due to future research studies on the growth effect of plants and the discovery of growth effects on specific plants, but in this case as well, It goes without saying that it is necessary to select and insert a filter that meets each condition.

Effects of the Invention As described above, it is necessary to effectively use the excellent rising characteristics with respect to wavelength of the sharp cut filter for both wavelengths of 400 nm and 700 nm, and to use a silicon photodiode whose absolute response is clear. As a result, it is possible to realize an optical emission measuring device that accurately measures the effective amount of optical emission for plant growth, such as photosynthetic effective photon flux density, and its practical value is extremely high. In addition, PPFD and 660nm / 730nm photon flux density ratio can be measured with high accuracy by simply switching the optical system.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an optical radiation measuring device according to an embodiment of the present invention,
FIG. 2 is a characteristic diagram of the action function of the photosynthetic effective photon flux density (PPFD) of the plant, FIG. 3 is a characteristic diagram showing an example of the spectral responsivity of the light receiving part of the conventional PPFD measuring device, and FIG. 4 is the present invention. FIG. 5 is a principle diagram of PPFD measurement according to the present invention, and FIG. 5 to FIG.

Claims (4)

(57) [Claims] 1. A light emission measuring device for measuring a photosynthetic effective photon flux density, comprising a half mirror installed obliquely with respect to an incident optical path and a 400 nm optical path installed in one of the optical paths separated by the half mirror. A short wavelength cutoff sharp cut filter, a wavelength proportional silicon photodiode having an absolute responsivity directly proportional to the wavelength, which receives light emitted through the 400 nm short wavelength cutoff sharp cut filter, and is separated by the half mirror. A 700 nm short wavelength cutoff sharp cut filter installed in the other optical path, and the light radiation that has passed through the 700 nm short wavelength cutoff sharp cut filter is received and has an absolute responsivity directly proportional to the wavelength, and the wavelength proportional type Another wavelength proportional silicon photo-diode that has the same spectral responsivity in the wavelength range of 700 nm and above Diode and the above 2
An optical radiation measuring device comprising a computing device for computing the photoelectric output of two wavelength proportional silicon photodiodes. 2. A light emission measuring device for measuring the photosynthetic effective photon flux density, which is 700 nm obliquely installed in the incident light path.
Short wavelength cutoff sharp cut filter and wavelength proportional silicon photodiode having absolute responsivity directly proportional to wavelength, which receives the optical radiation passed through the 700 nm short wavelength cutoff sharp cut filter, and 700 nm short wavelength cutoff 40 installed in the optical path of the reflected light of the sharp cut filter
0nm short wavelength cutoff sharp cut filter and 400nm
Another one that receives optical radiation that has passed through the short wavelength cutoff sharp cut filter, has an absolute responsivity directly proportional to the wavelength, and has the same spectral responsivity in the wavelength range of 700 nm or more as the wavelength proportional silicon photodiode. An optical radiation measuring device comprising a wavelength proportional silicon photodiode and a computing device for computing the photoelectric output of the two wavelength proportional silicon photodiodes. 3. A half mirror obliquely installed with respect to an incident optical path, a 400 nm short wavelength cutoff sharp cut filter installed in one of the optical paths separated by the half mirror, and the 400 nm short wavelength cutoff sharp cut. Narrow band pass filter of 660 nm where the filter and the installation position are interchanged, the light emission passing through the short wavelength cutoff sharp cut filter of 400 nm and the light emission passing through the narrow band pass filter of 660 nm are received, and the absolute proportion to the wavelength is directly proportional. The wavelength proportional silicon photodiode with responsivity and the other optical path separated by the half mirror.
700nm short wavelength cutoff sharp cut filter and 700
Short wavelength cutoff sharp cut filter of nm and installation position 730 nm narrow band pass filter that is switched according to the replacement of the narrow band pass filter of 660 nm, and light emission that has passed the short wavelength cut sharp cut filter of 700 nm and
Another wavelength that receives optical radiation that has passed through a 730 nm narrow band pass filter, has an absolute responsivity directly proportional to the wavelength, and has the same spectral responsivity in the wavelength range of 700 nm or more as the wavelength proportional silicon photodiode. Equipped with a proportional silicon photodiode and a computing device for computing the photoelectric output of the two wavelength proportional silicon photodiodes, the measurement of photosynthetic effective photon flux density and photon flux density ratio at wavelengths 660 nm and 730 nm can be switched. Optical emission measurement device. 4. A disc turret, and a short wavelength cutoff sharp cut filter of 400 nm, a short wavelength cutoff sharp cut filter of 700 nm, a narrow band pass filter of 660 nm, and a narrow band pass filter of 730 nm, which are respectively mounted on the disc turret. A stepping motor for rotating or sliding the disc turret, a stepping motor control section for controlling the rotation of the stepping motor, and an absolute responsivity proportional to a wavelength for sequentially receiving transmitted light from the four filters. And a storage device for storing a photoelectric signal of the wavelength proportional silicon photodiode, and an arithmetic device for calculating a photoelectric signal of the wavelength proportional silicon photodiode, and a photosynthetic effective photon flux. Density and
Optical emission measurement device that can switch the measurement of photon flux density ratio at wavelengths of 660 nm and 730 nm.