The role of the filter
device used to select the required radiation wavelengths.A common filter, is no filter can make objects imaging more bright, because all the filter will absorb some wavelengths, making objects become more dark.
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 blue days, green leaves, if the normal, will not be able to highlight the theme of "flower", because the image of chrysanthemum is not enough.If, however, 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, highlights the theme of "flower".
Infrared filter refers to the infrared photography with a deep red filter.Color filter, even if not too deep will have corresponding effect. The infrared filter is mainly used in security monitoring, infrared gas analyzer, night vision products, infrared detectors, infrared receiver, infrared sensors, infrared communication products.Specific to the product such as: monitoring camera, remote control, infrared curtain wall products, infrared sensing toilet, faucet, hand sanitizer, infrared thermometer, infrared printer, interactive electronic whiteboard, infrared touch screen, fingerprint recognition machine, etc.
Interference filter refers to the use of light interference principle and thin-film technology to change the spectral composition of light filter.Using the interference principle only make specific spectrum of light through the optical thin film.Usually composed of multilayer film.There are many different kinds of interference filter and use different way, common interference filter cutoff filter and bandpass filter.Cut-off filter spectral range is divided into two areas, a light in the area by area (as), and the other part of light energy through fully (passband area).Typical cut-off filter has a low pass filter (only allows longer wavelengths through) and high-pass filter (only allow a short wave through), they are based on multilayer dielectric film, with a high refractive index and low refractive index layer to pay for a periodic structure.
Infrared end filter allowing visible light through and by the infrared optical filter.Its function is to prevent the CCD image sensor due to the pixel interval and the pseudo color and ripple, improve the influence of infrared CCD imaging.
Color filter is a kind of color optical filter, it can accurately through the small range of wavelengths of light waves, the reflection off other don't want to pass band.Color filter is usually installed in the front of the light source, make the human eye can receive light saturation of a color.With infrared filter, green, blue, etc.With UV filter, VD filter, compared to those who take the floorboard of color filter.Filter such as contrast, color filter, LB filter, etc.
Polarizer, also called polarizer, polaroid, PL mirror for short, is a kind of color filter.Excellent use of polarizer is selectively let light through a direction vibration, in color and black and white photography often used to eliminate or weaken non-metallic surface strong reflection, thereby eliminating reduce light spot.
Filter has two major functions:
1) filter out infrared light. (2) modification in the light
Filter out infrared:
Color cameras 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 - Coatin 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.