The function of the filter: 1. Filter out the infrared light. 2. Trim the incoming light

1. Filter out the infrared:

Color CCD can also sense infrared light, because it will induce infrared rays, which will cause the DSP to not calculate the correct color. Therefore, a filter must be added to separate the infrared part of the light, so only the color CCD needs to be equipped with filters, black and white. No need.

2. Trimming incoming light:

Because the CCD is composed of a single photoreceptor (CELL), it is best to direct the light, but in order to avoid interference with the adjacent photoreceptor, the light needs to be trimmed, so the filter is not glass, but quartz. The film, using the physical polarization characteristics of quartz, keeps the incoming light, retains the direct part, and reflects off the oblique part to avoid affecting the photosensitive spot next to it.

Understand the basic functions, then talk about how to do it.

1 Filter out the infrared:

The coating method and the blue glass can be used, and the coating is divided into a vacuum coating method and an electroless plating method. The electroless plating method is to immerse the quartz sheet in a solvent for electroplating, the cost is low, but the coating thickness is uneven and easy to fall off, and the vacuum coating is vacuum evaporation, and the coating is uniform. It is not easy to fall off, but the cost is high. Above we call IR Coating, the purpose is to filter out the infrared rays, and also add the so-called AR-Coating coating, the purpose is to increase the light transmittance, because the light is transmitted through different media (such as From the air into the quartz plate), part of the refraction and reflection will be produced. After AR-Coating, the filter can achieve a penetration rate of 98-99%, otherwise it will only have a transmittance of 90-95. Sensitivity certainly has an effect.

In addition, it uses blue glass. Blue glass filters infrared rays by means of "absorption". IR-Coating filters out infrared rays by reflection, but reflected light is easy to cause interference. If only infrared rays are filtered out, blue glass is better. The choice. But the above said that the glass can not trim the light, so there is a so-called "two-piece" filter with a piece of blue glass and a piece of quartz. The blue glass is used to filter the infrared rays, and the quartz piece is used to trim the light, so the quartz Just do AR-Coating on the chip.

2. Trimming into the light:

As mentioned above, using the physical polarization characteristics of quartz, the incoming light remains in the direct part and reflects off the oblique part, but can only be trimmed in one direction. Usually the camera only considers the horizontal resolution, so only the light is made. Horizontal trimming, so the direction should be correct when the filter is attached, can not be reversed. If the vertical light should also be trimmed, what should I do? Very simple, stick two pieces, turn one piece to 90 degrees, so there is This kind of filter, also called "two-piece", is used for horizontal trimming, one for vertical trimming, and one for IR-Coating to filter infrared.

What is more advanced? It is two pieces of quartz inter-clip blue glass, then all the advantages will be there. This kind of "three-piece type is common in Japanese imported machines.

Having said that, there is still no concept, you can make a small test, the props are very simple --- a tie, and it is a kind of fine and dense stripes will shine, a quartz type because there is no vertical plane Trimming, the camera will produce a piece of color interference, the two pieces will not be, if the horizontal tie has no color interference, but the straight line tie, haha! The filter is reversed.

Also, we often see visitors on TV, some with crossed twill ties, the camera is also a flower, not a camera, a set of hundreds of thousands! But the filter only two, only Trimming the horizontal and vertical faces, the dense twill with a 45-degree angle is not lost, unless two more pieces are trimmed to the left 45 degrees and the right 45 degrees, so that many pieces become thousands of layers of cake. Therefore, the TV station The anchor will never have a twill tie on the lens, so you have to remember if you have the chance to go to the TV!

So what is the function of the dual filter?

Today's cameras have a night vision function. What does this night vision rely on to see objects in complete darkness? It depends on the infrared light LED to emit infrared light, and then enters the CCD image after reflection. This creates a contradiction! In order to filter the infrared light generated during the daytime sun exposure, we put a blue glass with the cut-off infrared light on the front of the CCD, and at night the LED The emitted infrared light is also filtered by blue glass and cannot be imaged. How can this contradiction be solved? How to cut off the infrared light during the day to make the image clear and true, and at night, can the infrared light emitted by the LED completely enter the CCD to complete the night vision function? This is the function of the dual filter. It is a mechanical device to complete the filter that cuts off the infrared light in front of the CCD during the day. When it is switched to a fully transparent filter at night, it satisfies the infrared night vision. Camera requirements. This mechanical device is called a dual filter switcher called IR-CUT. At present, the market can achieve double-layer crystal clip blue glass during the day, and the three-layer crystal at night seems to be only a switcher of Shenzhen Weitexin Technology Co., Ltd., model ICR-V02M1. If you are interested, you can find it online, they can provide samples to the camera factory to test the results.