The lens has two meanings in film and television. One refers to the optical components used by movie cameras and projectors to generate images and is composed of multiple lenses. Different lenses have different appearance characteristics, and their use in photographic appearance constitutes a visual expression.
The second refers to a continuous picture taken from power-on to power-off, or the segment between two splicing points called a shot. The first meaning and the double meaning are two completely different concepts. To distinguish the differences between the two, the first one refers to the optical lens, and the second one refers to the lens image.
The main function of the lens is to collect the reflected light from the illuminated object and focus it on the CCD. The image projected on the CCD is inverted. The camera circuit has the function of reversing it, and its imaging principle is opposite to that of the human eye.
In a surveillance environment that does not require infrared light assistance, ordinary lenses can be used; in a surveillance environment with infrared light supplementary light, if you want to have an ideal imaging effect, you must use an IR filter lens;
Of course, you can also see the picture under the infrared supplement light with a standard lens, but the image will become blurry. I believe everyone has a deep understanding of this.
The price of professional or lenses is several times that of ordinary lenses. Why? Because the lenses are evident during the day and night, the effect is good and is naturally expensive.
The professional IR lenses adopt special lenses, which can gather light in the 430-900nm or even more extended wavelength range on the same plane, so their ir filter lens is clear regardless of daytime or night vision. Due to the unique lens material of their filter lens, the cost is naturally high.
The cost of professional IR lenses are high, and the new problem is coming again. The price of the machine that everyone makes is high, and the profit is low. What to do now? The coating on the lens and correcting the light, the cheap IR lens comes out. And no matter good or bad, they are all called IR lenses!
Because glass has different refractive indices for the light of different wavelengths, the position of the focal point will be different. At present, ordinary lenses on the market can gather light with a wavelength difference of about 250nm into the same stereo.
That is to say, the light in the swir wavelength range of 430-650nm or 650-900nm can be focused successfully and present a clear image. This is why the ordinary lens is clear and clear in the daytime, and the night vision is blurred, or the night vision is clear and the day is blurred.