Patent ID: 8743235

Claim:
An automatic exposure apparatus comprising: a shutter; a shutter controller connected to the shutter to open and close the shutter; an image sensor aligned with the shutter to detect an image through the shutter whenever the shutter is open; a memory storing a set of device parameters; and a processor connected to the shutter controller, the image sensor and the memory, wherein the processor: (a) receives a current image frame from the image sensor using an exposure value (EV) for the shutter, (b) computes a current image spatial entropy (ISE) for the current image frame (c) whenever the current ISE is greater than a previous ISE, (i) sets the current ISE equal to the previous ISE, (ii) increases the EV, and (iii) repeats steps (a) and (b), and (c) whenever the current ISE is less than or equal to the previous ISE, (i) decreases the EV, (ii) receives the current image frame using the EV, and (iii) displays the current image frame, wherein the current ISE is calculated using ISE( X )= nmH ( X,Xu )+ nm/ 2( H ( Xr/X )+ H ( Xl/X )− H ( Xl,Xu )− H ( Xr,Xu )).