11.3 LED Display
241
As an ideal color point light source, LED can be integrated into an array that functions as a surface light source with uniform chromaticity. Such a technology has
been widely used in various applications. It has been noticed that the light source has
become the mainstream backlight of liquid crystal display. The main function of the
backlight module of the liquid crystal panel is to provide a uniform, high-brightness
light source. The basic principle is to convert a point or line type light source into a
high-brightness and uniform luminance surface light source through effective light
modulation.
At present, LED backlight technology can be divided into straight type and sidein type. The former is simple and without the light guiding plate, but the mixed
light distance is not easy to reduce. It generally supports the backlight area adjustment technology, which is easy to achieve brightness adjustment, and can achieve
extremely high dynamic contrast. This is very important for improving the image
quality of the television. The latter backlight method sets the LED on the side of the
specially designed light guiding plate as a backlight. The cost of such design is low.
The thickness is also easily reduced, but the light efficiency is also reduced. Different
LED backlights have their own characteristics. The LEDs also have a lot of room for
improvement in terms of the design of point light sources into planar light sources.
The technology is, therefore, continuously evolving.
11.4 LED for Plant Breeding
11.4.1 Overview
British scientist Joseph Priestley discovered photosynthesis in the 18th century. Dutch
scientist Jan Ingenhousis proved that photosynthesis could only occur under the
condition of light [18]. At the end of the 19th century, Russian researchers carried
out a variety of artificial light source irradiation experiments on different plants
such as cucumber, tomato, spinach, two gourds, broccoli, onions, winter rape, etc.
It has been noticed that the plants grown speed is fastest under orange red light
exposure, followed by blue light and green light. In 1996, Mitsubishi Chemical
developed a Western lettuce cultivation device using red LEDs as a light source,
which promotes the increase of sugar content in the plant. In 2002, Japan’s CCS
company Morimoto Miho made a plant growth system including LED light source,
growth control software, signal conditioner and data collection software.
As far as the research in China is concerned, fluorescent lamps were used for
light cultivation in the 1980s. The results showed that under red light lumination the
leaf area expanded and the photosynthetic rate was fast. The chlorophyll content,
soluble sugar and total sugar content were increased. Chlorophyll a/b value and
total nitrogen content were low. It also has been noticed that blue light can thicken
seedling stem, regulate stomatal opening, promote cell membrane permeability and
cytoplasmic circulation. Seedling growth was better under red light mixed with blue
241
As an ideal color point light source, LED can be integrated into an array that functions as a surface light source with uniform chromaticity. Such a technology has
been widely used in various applications. It has been noticed that the light source has
become the mainstream backlight of liquid crystal display. The main function of the
backlight module of the liquid crystal panel is to provide a uniform, high-brightness
light source. The basic principle is to convert a point or line type light source into a
high-brightness and uniform luminance surface light source through effective light
modulation.
At present, LED backlight technology can be divided into straight type and sidein type. The former is simple and without the light guiding plate, but the mixed
light distance is not easy to reduce. It generally supports the backlight area adjustment technology, which is easy to achieve brightness adjustment, and can achieve
extremely high dynamic contrast. This is very important for improving the image
quality of the television. The latter backlight method sets the LED on the side of the
specially designed light guiding plate as a backlight. The cost of such design is low.
The thickness is also easily reduced, but the light efficiency is also reduced. Different
LED backlights have their own characteristics. The LEDs also have a lot of room for
improvement in terms of the design of point light sources into planar light sources.
The technology is, therefore, continuously evolving.
11.4 LED for Plant Breeding
11.4.1 Overview
British scientist Joseph Priestley discovered photosynthesis in the 18th century. Dutch
scientist Jan Ingenhousis proved that photosynthesis could only occur under the
condition of light [18]. At the end of the 19th century, Russian researchers carried
out a variety of artificial light source irradiation experiments on different plants
such as cucumber, tomato, spinach, two gourds, broccoli, onions, winter rape, etc.
It has been noticed that the plants grown speed is fastest under orange red light
exposure, followed by blue light and green light. In 1996, Mitsubishi Chemical
developed a Western lettuce cultivation device using red LEDs as a light source,
which promotes the increase of sugar content in the plant. In 2002, Japan’s CCS
company Morimoto Miho made a plant growth system including LED light source,
growth control software, signal conditioner and data collection software.
As far as the research in China is concerned, fluorescent lamps were used for
light cultivation in the 1980s. The results showed that under red light lumination the
leaf area expanded and the photosynthetic rate was fast. The chlorophyll content,
soluble sugar and total sugar content were increased. Chlorophyll a/b value and
total nitrogen content were low. It also has been noticed that blue light can thicken
seedling stem, regulate stomatal opening, promote cell membrane permeability and
cytoplasmic circulation. Seedling growth was better under red light mixed with blue