Traditional Culture Encyclopedia - Photography and portraiture - Development prospect of infrared camera
Development prospect of infrared camera
When the color CCD chip came out, the infrared camera faced another problem. The color cast is serious during the day!
In order to solve this problem, optical filter (ICF) is applied to CCD, which is mainly used to filter infrared rays and trim light. At that time, the filter only allowed visible light with the wavelength of (380NM-780NM) to enter, which solved the problem of color cast during the day, but it could not receive infrared rays at night, so the camera could not work at night. So some people began to make a fuss about the filter, so that the filter can not only receive infrared rays of a certain wavelength, but also filter out most infrared rays. This is actually the practice of "closing the door and opening the small window". Where there is demand, there is market. There is a special filter in the market, which can let infrared rays with the wavelength of 850 nm to 940 nm enter the filter. This filter is called "two-pass filter". The two-pass filter is attached to the CCD, so the color cast is not very serious during the day, and it can also receive infrared rays at night.
The "infrared all-in-one machine" can also let infrared rays with a wavelength of 850NM~940NM in the daytime, and once the infrared rays enter, it will cause DSP operation errors, which determines that the infrared all-in-one machine will definitely have a color cast, but it is lighter than before. Of course, some manufacturers have the ability to adjust the RGB tone inside the chip to make up for the operation error of DSP. And cold and warm colors are also "difficult for everyone to adjust", and manufacturers only treat colors relatively truly. In fact, the "infrared all-in-one machine" is only a temporary solution, not a permanent cure.
How to make the camera not cast color during the day and receive infrared rays clearly at night? Many security companies are thinking about this problem, so color day and night cameras came into being. This kind of camera adds a mechanical device, adds a filter during the day, removes it at night, and replaces it with ordinary glass to trim the light, just like putting sunglasses on CCD, much like a gentleman wearing reading glasses. When reading and writing, his eyes pass through his glasses, but when looking at people, his eyes shoot from above the frame, which is also the prototype of "IR CUT" infrared camera.
Because the wear resistance of the mechanical device is not very high, and the infrared light is turned on in a critical state at night, people can always hear the "click" sound coming from inside the camera, and even the best raw materials can't stand the wear and tear day and night. When many camera lenses can't be switched, it goes back to the original problem of serious color cast during the day or unclear images at night. Later, the "IR CUT" camera was improved by electromagnetic switch and relay switch, but because of its mechanical accuracy, the thickness of the filter was even changed. Although "IR CUT" camera has made a contribution to the problem of color cast, it still cannot occupy the market.
There is an infrared camera on the market that can make colors realistic, which is called high color reproduction in professional terms. This is the "double CCD infrared camera".
Double CCD infrared camera, as its name implies, has two CCD boards, which are actually two cameras combined in a shell and two independent cameras. The principle of dual CCD infrared camera is actually very simple, except that the two cameras are spliced in the same shell and switched by a photosensitive resistor. A CCD used during the day is stuck with a filter that completely filters out infrared rays, and the one that is on at night has no filter, just an ordinary glass sheet to trim the light. Its principle is equivalent to "IR CUT". At the same time, two cameras work together in turn, one in day shift and one in night shift, which can prolong the service life of cameras. With the promotion of the market, the problems of dual CCD infrared cameras are also obvious. First of all, when the light intensity is at the intensity set by the photoresistor, the infrared lamp will keep flashing at the critical point, and there is still a time difference of several microseconds between the switching of current and the opening of another CCD plate for imaging. So at night, within a few minutes when the light intensity is at the critical point, this camera will always hear the sound of current switching, which will seriously cause no picture.
In order to solve this problem, Qiao 'an Technology added a delay circuit to the dual CCD infrared camera. After receiving the light change, delay for 3 seconds before switching, which can eliminate this phenomenon and fundamentally solve the problem of continuous switching caused by light change.
But according to the author's research, so far, there is at least one problem with dual CCD infrared cameras. Because the lenses of the two CCD directors are on the same plane, the shooting angles and ranges of the two directors are different. Therefore, the monitoring place of imaging on the display is different, but many users just don't pay attention!
Of course, will there be any new technological progress in infrared cameras? Will there be a substitute? In today's technological upgrading, no one can accurately predict.
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