Working principle of the filter: filter is made of plastic or glass add special dye, red filter only through red light, so on.Refractive index and air originally is the same as the glass, all colours are available through, so is transparent, but after dyed the dye, molecular structure change, the refractive index changes, also through of some of the light had changed.A beam of white light through the blue filter, for example, a blue beams of light, red light and green light, very few, most is absorbed by the filter.Filter is used to filter to the light of a wavelength range, the effect of monochromator, but it can't get the monochromatic light.
The role of the filter is very big.Widely used in photography.Some photographers shooting landscapes, why accent is always so outstanding, how do you do?It is used to filter.You want to use a camera or a flower, for example, the background is the blue sky, green leaves, if the normal, will not be able to highlight the theme of "flower", because the image of chrysanthemum is not enough.However, if put a yellow filter in front of the cameras, blocking part of the green leaves of green, blue, blue sky and the chrysanthemum yellow light emitted by a large number of via, in this way, chrysanthemum is very obvious, highlighted the "flower" the master
The function of the filter: 1. The filter out infrared light. 2. Trim the light
Filter out infrared:
Color CCD can be infrared sensor, is because of induction infrared lead D.S.P can't calculate the true colors, and so must add a filter, the light in the infrared part is separated, so only color CCD need to pack filter, black and white and you don't have to.
Dressing into the light:
On CCD are photoreceptor (CELL), the light is best point-blank come in, but for fear of interference to adjacent photoreceptor, will need to be finishing to the light, so that filter is not glass, but quartz plate, using physical polarization characteristics of quartz, the incoming light, keep direct part, reflection up some of the oblique, avoid to affect beside the point.
1 filter out infrared:
Available and blue glass Coating way, Coating vacuum Coating and chemical Coating method, chemical deposition is immersed quartz plate in solvent to electroplating, the cost is low but the Coating thickness uneven and easy to fall off, vacuum Coating is by vacuum evaporation method, uniform Coating and not easy to fall off, but the cost is high. We've said above IR Coating, goal in filter out infrared, plus other so-called AR - Coating deposition, purpose is to increase the light transmittance, because when the light through different media (such as from air into the quartz plate), will produce part of the refraction and reflection, and AR - after Coating, filter can reach 98-99% penetration rate, otherwise only the penetration rate of 90-95, the influence on the CCD sensitivity of course.
Also is to use blue glass, blue glass is made of "absorb" way to filter the infrared, and IR - we use the reflection of the way to filter out infrared Coating, but reflected light is easy to cause interference, if only consider the filter out infrared, blue glass is a better choice. But said on the glass can't mend the light, so there is a piece of blue glass with a quartz piece of the so-called "two type" filter. The blue glass is used to filter infrared, and quartz cut with the light, so on quartz can do AR - Coating line.
2. Trim the light:
Said that using physical polarization characteristics of quartz, the light in, keep direct part, reflection up some of the moves, but only on one direction, usually the camera only considering the horizontal resolution, so only do horizontal finishing to the light, so stick to filter for a direction, not the opposite. What if the vertical light also want to finish what should I do?Is very simple, stick to two pieces, one piece turn 90 degrees, so this is also called "two type" filter, used in horizontal trim, used a piece in the vertical trim, one piece to do IR - Coating to infrared filter.