Introduction to CCD Filter
The CCD filter that we often refer to is actually called the correct name; Optical low-pass filter; Widely used in various microscopes, such as fluorescence microscopy, laser scanning confocal fluorescence microscopy, confocal microscopy, and internal reflection fluorescence microscopy. In this article, Ruicheng Optoelectronics will introduce two important functions of CCD filters: filtering out infrared rays and adjusting incoming light.
Filter out infrared radiation:
Color CCD is capable of sensing infrared radiation, which makes it difficult for D.S.P to calculate the correct color. Therefore, you must add a filter to separate the infrared light, so only color CCD needs to be equipped with a CCD filter, not black and white.
Trimming the incoming light:
Due to the fact that CCD is composed of many photoreceptors, the best light is direct, but in order to avoid interference with adjacent photoreceptors, the light must be pruned. Therefore, the filter is not glass, but quartz. By utilizing the physical polarization characteristics of quartz, the incident light is kept in the direct part and reflected in the oblique part to avoid interference. Affects the light spot next to it.
The basic function of CCD filter:
1. Filter out infrared radiation:
Can be coated with blue glass, vacuum coating, and chemical coating. Chemical coating is the process of electroplating quartz plates by immersing them in a solvent. Low cost, but uneven coating thickness and easy detachment. Vacuum coating is a method of vacuum evaporation, which has a uniform coating, is not easy to peel off, and has a high cost. Above, we refer to it as an infrared coating. In order to filter out infrared radiation, we also need to add an AR coating to increase transmittance. This is because when light passes through different media (such as air entering quartz), partial refraction and reflection occur. Using AR coating, the transmittance of the filter can reach 98-99%. The penetration rate is only 90-95, which affects the sensitivity of CCD.
In addition, blue glass is used for; Absorption "; Filter infrared light, while IR coating filters infrared light through reflection, but the reflected light can easily cause interference. If only infrared filtering is considered, blue glass is a better choice. But glass cannot adjust the light, so there is a blue glass with an additional one called“ Two piece style; Quartz plate for filter. Blue glass is used to filter infrared radiation, and quartz plates are used to fine tune light, so an AR coating must be applied to quartz.
2. Adjust the lighting:
By utilizing the physical polarization properties of quartz, the incident light is kept in the direct part and the oblique part is reflected off, but only one direction can be adjusted. Usually, cameras only consider horizontal resolution, so they only trim lights horizontally. Therefore, when pasting the filter, the direction should not be reversed. What if vertical light also needs to be trimmed? Just paste two pieces and rotate one piece 90 degrees. So there are two types of filters, one is a horizontal filter, the other is a vertical filter, and the other is an infrared coated filter.
How to choose a good microscope filter? The suggestion given by Ruicheng Optoelectronics is to match the excitation and emission peaks of the fuel with a small overlap; Deep cut-off depth; Low spontaneous fluorescence; Good lens shape is beneficial for the extraction of fluorescence imaging.
Filter out infrared radiation:
Color CCD is capable of sensing infrared radiation, which makes it difficult for D.S.P to calculate the correct color. Therefore, you must add a filter to separate the infrared light, so only color CCD needs to be equipped with a CCD filter, not black and white.
Trimming the incoming light:
Due to the fact that CCD is composed of many photoreceptors, the best light is direct, but in order to avoid interference with adjacent photoreceptors, the light must be pruned. Therefore, the filter is not glass, but quartz. By utilizing the physical polarization characteristics of quartz, the incident light is kept in the direct part and reflected in the oblique part to avoid interference. Affects the light spot next to it.
The basic function of CCD filter:
1. Filter out infrared radiation:
Can be coated with blue glass, vacuum coating, and chemical coating. Chemical coating is the process of electroplating quartz plates by immersing them in a solvent. Low cost, but uneven coating thickness and easy detachment. Vacuum coating is a method of vacuum evaporation, which has a uniform coating, is not easy to peel off, and has a high cost. Above, we refer to it as an infrared coating. In order to filter out infrared radiation, we also need to add an AR coating to increase transmittance. This is because when light passes through different media (such as air entering quartz), partial refraction and reflection occur. Using AR coating, the transmittance of the filter can reach 98-99%. The penetration rate is only 90-95, which affects the sensitivity of CCD.
In addition, blue glass is used for; Absorption "; Filter infrared light, while IR coating filters infrared light through reflection, but the reflected light can easily cause interference. If only infrared filtering is considered, blue glass is a better choice. But glass cannot adjust the light, so there is a blue glass with an additional one called“ Two piece style; Quartz plate for filter. Blue glass is used to filter infrared radiation, and quartz plates are used to fine tune light, so an AR coating must be applied to quartz.
2. Adjust the lighting:
By utilizing the physical polarization properties of quartz, the incident light is kept in the direct part and the oblique part is reflected off, but only one direction can be adjusted. Usually, cameras only consider horizontal resolution, so they only trim lights horizontally. Therefore, when pasting the filter, the direction should not be reversed. What if vertical light also needs to be trimmed? Just paste two pieces and rotate one piece 90 degrees. So there are two types of filters, one is a horizontal filter, the other is a vertical filter, and the other is an infrared coated filter.
How to choose a good microscope filter? The suggestion given by Ruicheng Optoelectronics is to match the excitation and emission peaks of the fuel with a small overlap; Deep cut-off depth; Low spontaneous fluorescence; Good lens shape is beneficial for the extraction of fluorescence imaging.