Use Pixel's Magnifier - magnifer

 2024-07-27 23:24:57

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The reflection, absorption and emission features form spectra that are closely related to the molecular composition of the material being examined. Table 1. is well known and it highlights the spectral bands in which each of the most common molecules has its electromagnetic resonance overtone.

Everyone who switches over to a diffuse coating notices that the crop grows differently. With pot plants it can result in a different appearance. The consequence of this strongly depends on the type of plant and the market. Sometimes a heavier plant is more popular with the trade. But with other crops the grower will want to adjust the cultivation period to continue to deliver the same quality. In research trials the cultivation period for anthurium was six weeks earlier; in a commercial nursery a three-week reduction was achieved. Therefore it does have consequences for the cultivation strategy within the nursery. More and more pot plant growers are becoming convinced of the benefits of diffuse light. Due to the large assortment of ornamentals we don’t yet have experience with all crops. However, it can hardly go wrong. So far, horticultural research has failed to show any disadvantages caused by diffuse light.

Figure 3. RGB, multispectral (28 bands), and hyperspectral (224 bands) images of almonds and shells (green is almond and blue is shell).

The hyperspectral camera also offers more flexibility as the user can later upgrade the machine to sort new contaminants or materials. With the Specim FX cameras, users can freely select relevant bands. In practice, the Specim FX hyperspectral cameras can transform into multispectral cameras, whereas a multispectral camera could never become hyperspectral.

Multispectralimage

To illustrate the advantages of a hyperspectral camera compared to a multispectral one, we studied the sorting of shells among almonds. It is a typical application that requires highly accurate identification between materials that look very similar.

Hyperspectral imaging involves capturing and analyzing data from a large number of narrow, contiguous bands across the electromagnetic spectrum, resulting in a high-resolution spectrum for each pixel in the image. As a result, a hyperspectral camera provides smooth spectra. The spectra provided by multispectral cameras are more like stairs or saw teeth without the ability to depict acute spectral signatures.

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In other words, because the number of spectral channels captured is limited to 28, the spectral information required to tell the difference between the almond and shell is lost.

As the table shows, the spectral range of 700 – 2500 nm is necessary for many applications. Especially for those related to food quality assessment and plastics sorting, the spectral range of 1100 – 1700 nm is mandatory. Multispectral cameras limited to 400 – 1000 nm are not applicable for those applications.

Multispectralcamera uses

Hyperspectral imaging provides more detailed data than multispectral imaging, allowing more specific analysis and accurate identification of materials and substances. Multispectral imaging may not be able to distinguish between closely related materials due to the limited spectral resolution.

In addition, some pre-processing methods are not suitable for multispectral data. For instance, derivative or smoother such as Savitzky-Golay, require continuous spectra to perform well, which are not provided by multispectral sensors.

Multispectralimaging skin

Years of experience have been gathered regarding fruit vegetables. More recently a lot of expertise has accumulated on pot plants, both in horticultural research as well as in practise. In general, pot plants grown under ReduFuse form more leaves towards the bottom of the plant. They are also more resilient to changing weather, especially in the spring. Due to the low stress level, the speed of development and quality rise. Because the plant is under less stress, the grower can allow in more light. However, it is advisable to use the usual light level when first using ReduFuse. Then, if it seems that the plant can take more, start to shade later in the day than usual. In this way you let in more light. Horticultural research has shown that many plants can handle more light than is commonly used, if the grower succeeds in maintaining the air humidity at a high enough level.

In a greenhouse without a light-diffusing roof, areas of light and shade always appear when the sun shines. This uneven light distribution is not ideal: When the light is strong, the leaves and flowers in the well-lit areas experience stress while the leaves in the shadow under-perform. They could easily assimilate more if they received more light. A diffuse coating solves both problems of stress and under-performance. The even light distribution ensures that the top of the plant does not become too hot. At the same time, the leaves lower in the leaf canopy can contribute more to production.

Multispectralcamera for drone

Spectral channels are distinct wavelength ranges within the electromagnetic spectrum that sensors in multispectral or hyperspectral imaging systems capture. Each channel represents a specific band of wavelengths, and the collection of these channels helps to identify objects or materials based on their unique spectral signatures.

Multispectralcamera for agriculture

Both multispectral and hyperspectral imaging are techniques used to capture and analyze the electromagnetic spectrum for various research, industry, and remote sensing applications. Choosing between these two complementary technologies comes down to the application requirements and the level of data already existing.

Considering the previous point, we compared almonds and shells with Specim FX17 camera data. We covered the spectral range of 900 – 1700 nm in the first data set with 224 bands. In the second data set, we used only 28 binned bands (i.e., merging consecutive spectral bands) to simulate a multispectral camera.

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Because the plant temperature is lower under a roof that diffuses light, there are consequences for the climate control. If the grower doesn’t change the settings, the plant will warm up slower in the morning. This can be an important advantage in the summer but you certainly don’t want this in the spring. Therefore it’s important to steer the plant according to temperature, preferably plant temperature rather than air temperature. In general it’s sufficient to adjust the air vents. For sensitive crops – without a coating – it’s necessary to shade quite early in the year. If the grower is forced to frequently open and close the shade cloth, it creates a yo-yo effect and the plants suffer. When the screen is open it’s too light and when the screen is closed it’s too dark. This is no longer a problem under ReduFuse. Therefore growers with sensitive crops apply the coating in week four or five, depending on the weather. With such crops it’s possible to apply ReduSol later in the spring over the first diffuse coating, as soon as the plants need to be well shaded. In this way a grower can allow in more light during the spring while in the summer is still guaranteed of having optimal shade protection.

We find this discrepancy irrelevant and prefer to speak about spectral resolution (FWHM, Full Width Half Maximum*), highlighting the ability of a camera to separate two consecutive spectral peaks from each other.

Lastly, one aspect to consider when choosing between hyperspectral and multispectral cameras is the price. Typically hyperspectral cameras are more expensive and require more processing power than multispectral cameras. However, this is not always the case, especially if the multispectral camera needs to be custom-made with a relatively large number of bands.

For applications where the entire spectral range is unnecessary, custom-made multispectral cameras with well-chosen bands can perform equally well as hyperspectral cameras. However, this requires the user to know the selected number of spectral bands that are necessary for the inspection or analysis. If the user does not know the spectral requirements of an application or they are very complex, a hyperspectral camera provides an ideal solution to gather the data for analysis.

MultispectralCamera price

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As mentioned above, we built two models to illustrate these points related to the ability to depict acute spectral features. The hyperspectral model covering 224 bands is more accurate than the multispectral model covering only 28 bands. With the hyperspectral data, the edge effect disappears, and we can classify even the smallest pieces of shell correctly.

A standard definition states that hyperspectral cameras have more than 100 bands, whereas multispectral ones have fewer. But this definition does not consider the width of the spectral range or the sampling. That means that if a camera covers the spectral range 400 – 600 nm with 50 bands, it would not be hyperspectral, whereas if it covered 400 – 800 nm with the same sampling (meaning this time 100 bands), it would be hyperspectral.

*The full width half maximum defines the spectral resolution of a system, more precisely, in this context, its ability to separate spectral peaks from each other.

The main difference between multispectral and hyperspectral cameras is the number of bands they record and how narrow the bands are (i.e., the spectral resolution).

Since the launch of ReduHeat in 2005 users often ask us if it is possible to combine different ReduSystems coatings with one another. Just to make it clear, when we talk about combining we mean ‘layering’ one coating over another, not mixing the products because that can definitely cause problems. We...

As can be seen in Figures 1. and 2., spectra related to the 224 bands dataset are much smoother than those depicted with only 28 bands. From the hypersepctral data, we can also pick the small but crucial spectral differences that enable us to separate the almonds from the shells.

Lumiforte is continuously developing horticultural coatings. We want to offer the ideal coating for your greenhouse and crop in as many situations as possible. At the beginning of 2014 we introduced a new diffuse coating that keeps out heat: ReduFuse IR.

We selected 28 spectral bands in this study to simulate a multispectral camera. However, typical multispectral cameras can have notably fewer spectral bands, making their ability to depict fine spectral features even lower.

Multispectralvs hyperspectral

Our article about Hyperspectral imaging vs. RGB cameras shows that RGB cameras do not perform well in sorting nuts and pistachios. The Specim FX10 provided better results, and the Specim FX17 had the most accurate sorting capability.

Multispectralremote sensing

For applications that require more spectral bands and higher spectral resolution than multispectral imaging can provide, a hyperspectral camera is the natural solution.

For most of the multispectral cameras on the market, the spectral range is limited to 400 – 1000 nm and the typical number of bands is between 4 – 5. Those are crucial limitations for many applications.

Growers ask many questions about light loss in relation to applying a coating. Through smart use of ReduSystems products it is possible ‘to shade with the light’. Here are a few tips to discuss with your customers.

Figure 2. Specim FX17 spectrum of almond with 224 and 28 bands. Purple circles highlight the spectral differences due to the presence of oil in almonds but not in the shell.

A wide range of flowering and green pot plants performs better under ReduFuse. For some types the increase in productivity or acceleration of the production cycle is quite substantial. That is especially true if the grower can allow in more light. But even at an equal level of light, diffused light leads to less stress and therefore better growth and improved quality.