Patent ID: 7634183

Claim:
A focus adjustable method, comprising steps of: allowing an external light beam to pass through a lens module, thereby generating an optical image; obtaining focus values UR, UL, DR and DL of said optical image at four corners thereof respectively; performing a first image analysis procedure to obtain an image diagonal spinor D according to one of the formulas: D=(DR+UL)−(UR+DL) or D=(DR+UL)−(UR+DL)/4; determining optical systematic errors of said lens module according to said image diagonal spinor D; performing a second image analysis procedure to obtain a two-dimensional geometric tilt vector T(X,Y) according to the formulas: T(X,Y)=(X 2 +Y 2 ) 1/2 , ∠ arctan(Y/X), where X=[(DR+UR)−(UL+DL)]/b, Y=[(UR+UL)−(DR+DL)]/a, or X=[(DR+UR)(UL+DL)]/(4×b), Y=[(UR+UL)−(DR+DL)]/(4×a), and a and b are correction factors for correcting an aspect ratio of said lens module; and correcting a tilt phenomenon of said lens module according to said two-dimensional geometric tilt vector T(X,Y) so as to achieve a more uniform focusing effect of said optical image.