Patent ID: 7692712

Claim:
An offset compensation apparatus for use in an optical zoom lens system comprising: a lens unit including a zoom lens and a focus lens; a lens conveyance unit which conveys the zoom lens and the focus lens; an offset measurement unit which measures an offset of the zoom lens and an offset of the focus lens; an offset verifier which verifies the measured offset data of the zoom lens and the focus lens; and a controller which controls the zoom lens and the focus lens according to the verified offset data, wherein the offset measurement unit performs the measuring of the offset of the focus lens by: detecting an origin of the focus lens and an origin of the zoom lens; selecting a zoom trace curve according to a distance from a target object; resetting the offset of the focus lens, such that the focus-lens offset is to be zero “0”; moving the zoom lens in a tele-direction (T) or a wide-direction (W); increasing the number of moving steps of cycles of the focus lens in a CCW direction; measuring a focus level, and determining a high focus level (High) or a low focus level (Low); and adjusting the number of moving steps or cycles of the focus lens according to the measured focus level (High or Low), and storing the offset of the focus lens, and the offset measurement unit performs the measuring of the offset of the zoom lens by: detecting an origin of the focus lens and an origin of the zoom lens; selecting a zoom trace curve according to a distance from a target object; applying the stored focus-lens offset; moving the zoom lens in the tele-direction (T); determining the presence (YES) or absence (NO) of a coincident focus; and storing the zoom-lens offset when the presence (YES) of the coincident focus is determined, or adjusting the number of moving steps or cycles of the zoom lens when the absence (NO) of the coincident focus is determined so that the adjusted offset of the zoom lens is stored.