The SNR is also an important performance indicator of the camera. When the camera captures a brighter scene, the screen displayed on the monitor is usually brighter, and viewers cannot easily see the noise in the screen. When the camera captures a dark scene, the screen displayed by the monitor is dim. It is easy to see snowflake-like noise in the picture. The strength of interference noise (that is, the degree of influence of interference noise on the picture) is directly related to the quality of the camera signal-to-noise ratio. That is, the higher the SNR of the camera, the smaller the influence of interference noise on the picture.
The so-called "signal-to-noise ratio" refers to the ratio of the signal voltage to the noise voltage, which is usually represented by the symbol S/N. Since in general the signal voltage is much higher than the noise voltage, the ratio is very large. Therefore, the actual calculation of the camera signal-to-noise ratio is usually based on the ratio of the mean square signal voltage to the mean square noise voltage. The number is multiplied by a factor of 20 in units of dB.
The signal-to-noise ratio given by the general camera is the value when the AGC (automatic gain control) is turned off, because when the AGC is turned on, the small signal is boosted, so that the noise level is also increased accordingly. The typical signal-to-noise ratio of COMS cameras is generally 45dB~55dB. When measuring the SNR parameter, a video clutter measuring instrument should be used to connect directly to the video output terminal of the camera.
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