US Patent 7809258 Camera and method for use with camera

An infrared (“IR”) camera includes first and second imaging parts for capturing an IR image and a visible light image, respectively. The field of view of the second imaging part at least partially overlaps the field of view of the first imaging part. The first imaging part includes IR optics. The second imaging part includes visible light optics. The IR camera also includes a focus motor for focusing at least one of the IR optics or the visible light optics. A sensor is operable to determine the position of the focus motor. Based on the position of the focus motor, a processor determines actual displacement for aligning the IR and visual light images. The actual displacement includes displacement due to parallax error and error due to the angle between the optical axes of the first and second imaging parts.