What is the term for the distance in millimeters between the optical center of a lens and the camera sensor when focused on infinity?

The correct term for the distance in millimeters between the optical center of a lens and the camera sensor when the lens is focused on infinity is called the focal length. Focal length is a fundamental characteristic of a lens that determines its angle of view and the magnification of the images it produces. It is essentially how far the lens needs to project light to bring it into focus on the sensor.

When a lens is designed, its focal length influences various aspects of the photographs taken, such as depth of field and perspective. A longer focal length generally provides a narrower field of view and greater magnification, while a shorter focal length offers a wider field of view.

Other terms such as F-stop relate to the aperture setting of the lens, which controls the amount of light that enters the camera, while sensor length is relevant to the size of the camera's sensor itself rather than the lens. "Distance Measurement" is not a standard term used in photography to describe this specific relationship between a lens and its focal point on the sensor.