Introduction to Color Filters
Concept of Color Filter
A filter operating in the visible light range is called a color filter, which can reflect or transmit colored light within a certain wavelength range, thus presenting different colors. Color filters are commonly used in color related and monochromatic applications, such as color printing, projection displays, LCD displays, photography and video recording, color decoration, etc.
At present, the widely used color filters are colored glass absorption filters and reflective optical thin film filters. There are also color filters designed using gratings and photonic crystals, but they are still in the experimental stage. The following will examine these different color filter technologies:
1、 Absorption type color filter
Absorption type color filters use the absorption effect of materials on visible light to achieve filtering. Common camera filters are actually colored glasses mixed with pigments, which utilize the selective absorption of light by pigments. They can help achieve or disrupt white balance, making the color of the image normal or biased towards a certain color. This type of filter can also be used in microscopes to help correct color differences or improve resolution. There are also neutral filters that uniformly reduce light intensity without changing spectral composition. They rely on a high absorption metal layer to work and are generally used to attenuate incident light intensity. Due to the decomposition of some pigments after prolonged exposure to ultraviolet radiation, their ability to absorb light decreases. Therefore, some absorption type color filters are not durable. Absorption type color filters used in flat panel displays have a 60% light loss, which reduces their light energy utilization efficiency.
2、 Optical thin film color filter
Optical thin film filters adjust the phase or amplitude of light propagating through a multi-layer thin film structure, causing the polarization state of light within a certain wavelength band to be changed or the intensity to be redistributed. Optical thin film filters generally include bandpass filters, cutoff filters, and other filters for special purposes, commonly used in fields such as spectroscopy instruments, spectral correction, optical communication, laser systems, etc. Optical thin film color filters have the following advantages:
1. Stable in nature and not easily faded
2. High reflection or transmittance, bright colors
3. Environmentally friendly materials and minimal pollution during the production process
Optical thin film color filters used for visible light filtering are widely used, including filters made as detachable components installed in front of light sources, as well as filter films embedded on surfaces such as optical lenses. The widely used color separation and combination film in projection display systems is a typical representative of this type of filter: it uses a cut-off filter structure to decompose white light into red, green, and blue colors or synthesize white light from red, green, and blue colors.
A filter operating in the visible light range is called a color filter, which can reflect or transmit colored light within a certain wavelength range, thus presenting different colors. Color filters are commonly used in color related and monochromatic applications, such as color printing, projection displays, LCD displays, photography and video recording, color decoration, etc.
At present, the widely used color filters are colored glass absorption filters and reflective optical thin film filters. There are also color filters designed using gratings and photonic crystals, but they are still in the experimental stage. The following will examine these different color filter technologies:
1、 Absorption type color filter
Absorption type color filters use the absorption effect of materials on visible light to achieve filtering. Common camera filters are actually colored glasses mixed with pigments, which utilize the selective absorption of light by pigments. They can help achieve or disrupt white balance, making the color of the image normal or biased towards a certain color. This type of filter can also be used in microscopes to help correct color differences or improve resolution. There are also neutral filters that uniformly reduce light intensity without changing spectral composition. They rely on a high absorption metal layer to work and are generally used to attenuate incident light intensity. Due to the decomposition of some pigments after prolonged exposure to ultraviolet radiation, their ability to absorb light decreases. Therefore, some absorption type color filters are not durable. Absorption type color filters used in flat panel displays have a 60% light loss, which reduces their light energy utilization efficiency.
2、 Optical thin film color filter
Optical thin film filters adjust the phase or amplitude of light propagating through a multi-layer thin film structure, causing the polarization state of light within a certain wavelength band to be changed or the intensity to be redistributed. Optical thin film filters generally include bandpass filters, cutoff filters, and other filters for special purposes, commonly used in fields such as spectroscopy instruments, spectral correction, optical communication, laser systems, etc. Optical thin film color filters have the following advantages:
1. Stable in nature and not easily faded
2. High reflection or transmittance, bright colors
3. Environmentally friendly materials and minimal pollution during the production process
Optical thin film color filters used for visible light filtering are widely used, including filters made as detachable components installed in front of light sources, as well as filter films embedded on surfaces such as optical lenses. The widely used color separation and combination film in projection display systems is a typical representative of this type of filter: it uses a cut-off filter structure to decompose white light into red, green, and blue colors or synthesize white light from red, green, and blue colors.