Lens filter---about day and night dual-pass filter

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About Day and Night Dual Pass Filters

1. Two ways to sense infrared light

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Infrared light is a type of stray light to color surveillance cameras under visible light conditions such as during the day, reducing the clarity and color recovery of color surveillance cameras.

There are currently two methods for enabling color surveillance cameras to sense infrared light in nighttime conditions.
First, open the filter to cover the infrared with visible light.In the absence of visible light, remove the filter to let in infrared.This scheme achieves good picture quality but requires the use of a piece of hardware called a switcher.Not only will it increase the cost, but the failure rate of the switch is also high.
Second, a specific infrared channel is opened on the filter to allow the infrared light with the same wavelength as the infrared lamp to come in. This is a day and night dual-channel filter, which is composed of an optical glass substrate and a depositionThe filter film on the optical glass substrate can block the ultraviolet and infrared rays in the mixed light source, which helps the digital camera CCD or CMOS no longer be affected by the ultraviolet and infrared signals, and obtains a clearer and clearer image;The light sheet can also selectively pass part of the infrared spectrum according to the different characteristics of the infrared lamp, so as to enhance the night vision function of the digital camera.

The day and night filter can pass the infrared light of visible light 420nm-620nm and 850nm, and block the infrared light of near-infrared 920nm-1100nm. You can get true color images during the day and clear black and white images at night.Mainly used in CCD chip color cameras and CMOS imaging systems, security monitor cameras, digital cameras, network cameras, video phones, doorbells, digital binoculars, license plate recognition cameras, etc., strong resistance to strong light and stray light interference, less color distortion.

1. Day and night filters

Day/Night Filter is a specially designed color filter that filters out UV light during the day and IR or visible light at night.It is often used in studios to protect the camera from harmful light.

The principle of the day and night filter is:
The degree of influence on the subject is controlled by changing the wavelength of the incident light.Since the wavelengths of infrared and visible light are similar and different, they have different absorption characteristics; when infrared and visible light are irradiated on the day-night filter, the two different wavelengths of light will be attenuated to different degrees.In this way, the influence of the external environment on the subject can be reduced to a certain extent.

Day and night filters are divided into two categories: one is a single-layer structure;

The other type is the multi-layer structure.

Single-layer structure day and night color filter lens consists of two layers of glass, the first layer is purple transparent glass; the thickness of the second layer is the same as the thickness of the first layer or slightly thicker.The multi-layer structure of day and night color filter lenses is generally composed of three or more layers of glass.

The outermost layer is transparent colorless transparent glass; the middle layer is a colored laminated film material composed of two or more pieces of colored glass with different colors; the third innermost layer is an organic film materialmade of substrate material.