In the Sony FCB camera, we often see words such as dynamic range, signal-to-noise ratio, bit number, but few people can speak clearly about the meaning of these concepts and the relationship between the three, so today follow the exhibition technology to understand the mystery between these parameters.
In the Sony FCB camera, the indicator that reflects the gray quality of each pixel is the dynamic range, which is also one of the important indicators to be considered by the Sony FCB camera. Dynamic range and spatial resolution are the two main indicators of Sony FCB camera.
The dynamic range of the gray level is represented by the Signal to Noise Ratio (SNR) in the analog video portion of the Sony FCB camera. The amount of digital video after the A/D conversion of the Sony FCB camera or image capture card is expressed in bits (n).
In the real world, an image will have the brightest and darkest areas at the same time, and the gap between them can be very large, and the images captured by the Sony FCB camera should reflect this huge range of gray scale as much as possible.
In addition, small changes in the gray scale of the image in the real world may be the boundary between the target and the background that the Sony FCB camera should distinguish, so the Sony FCB camera should also reflect the subtle changes in the gray scale of the image as much as possible.
Together, these two concepts are called dynamic range. That, in turn, depends on the performance of the Sony FCB camera.
The dynamic range, sensitivity and signal-to-noise ratio of CCD are three indicators that affect each other, and they reflect the gray performance of CCD industrial cameras from three different angles.
1. Signal to noise ratio: SNR
SNR is expressed in decibels
Where S is the difference between the video voltage Vmax at the brightest and Vmin at the darkest
The maximum output voltage Vmax of the Sony FCB camera depends on its ability to accept the maximum unsaturated incident light, that is, under this maximum light, the video output voltage of the Sony FCB camera is still unsaturated, and the change of its brightness can be expressed linearly. The minimum output voltage Vmin is the ability of the industrial camera to receive the minimum light, that is, the ability to receive the darkest area of the image, it is related to the material and structure of the image sensor itself (such as CCD or CMOS industrial camera), but also related to the noise of the Sony FCB camera, the greater the noise, the worse the ability to detect the darkest image.
2, bit n: A/D conversion will convert analog video signals into binary digital signals
The accuracy and dynamic range of A/D converted digital video depends on the binary bit number n, for example, 8bits binary number expresses 0-255 gray levels, and 10bits is 0-1023 gray levels, the higher the bit n, the finer the video gray level signal, the more precise, it also means the larger the dynamic range. The smallest bit value of n binary values is the unit of A/D that divides the gray level into the smallest, called LSB. At present, the A/D conversion bits of the camera on the market have 8, 10, 12, 14, 16 or higher, and most domestic cameras are currently in 8 or 10 A/D, and rarely see more than 14 bits.