The time when all the common electrodes (COM) apply a scanning voltage is called a frame, the frequency of how many frames are scanned in a unit time is called the frame frequency, and the ratio of the time of scanning the common electrode (COM) strobe and the frame period is called the duty ratio. Usually the duty cycle is equal to the reciprocal of the number of common electrodes N, that is, 1\/N. The driving waveform of the LCD is composed of several levels. In order to prevent the contrast from being uneven, a certain voltage is still applied to the electrode corresponding to the unlit pixel, which is important to reduce the cross interference generated by the lit pixel and prevent the contrast from being uneven.
The ratio (1\/n) of the voltage RMS of the non-lit pixel (non-selected point) to the voltage RMS of the lit pixel (selected point) in the LCD is called the bias ratio.