Patent ID: 7859577

Claim:
An automatic exposure (AE) controlling method, comprising: receiving an analog image signal from an image sensor; converting the analog image signal into a digital image signal using an analog front end; and controlling an exposure time of the image sensor and an analog gain of the analog front end, wherein controlling the exposure time of the image sensor and the analog gain of the analog front end comprises: calculating an electric shutter (ES) value of the digital image signal through a proportional integral control method; calculating an analog gain control (AGC) value of the digital image signal through the proportional integral control method; and performing AE compensation on a present image frame using the calculated ES value and the calculated AGC value, wherein the calculated ES value controls the exposure time of the image sensor and the calculated AGC value controls the analog gain of the analog front end, wherein calculating the ES value and calculating the AGC value comprises using a feedback delay variable for compensation in feedback of a brightness value of an image frame, and wherein the feedback delay variable is calculated using the following equation: CFD n = FD n + ∑ k = 0 1 ⁢ ⁢ UD n - k - ∑ K = 0 1 ⁢ ⁢ DD n - k , where CFD represents a final feedback value, FD represents a resent feedback value, UD represents a brightness change value when a frame brightness value increases, and DD represents a brightness change value when a frame brightness value decreases.