Patent ID: 7605952

Claim:
An exposure control device for adjusting an amount of light received by a focusing device and a photoelectric conversion device of an image scanning apparatus, the exposure control device comprising: a control unit configured to generate a control signal according to a certain condition of said image scanning apparatus; and a light-transmission adjusting device arranged in a light path from an object to said focusing device and said photoelectric conversion device, the light-transmission adjusting device being positioned to change an effective light-transmission area thereof in response to said control signal to adjust light amount passing therethrough, the light-transmission adjusting device comprising: a driving unit controlled by said control unit to generate a driving force in response to said control signal; a first optical grid plate arranged in the light path, the first optical grid plate having a first light-transmission area; and a second optical grid plate having a second light-transmission area smaller than the first light-transmission area and selectively driven by said driving force to be aligned with the first optical grid plate so as to reduce said effective light transmission area; wherein said certain condition of said image scanning apparatus is a selected resolution of said image scanning apparatus; and wherein said effective light-transmissible area under high resolution is smaller than that under low resolution.