One embodiment of the invention provides a backlight for an LCD display. A customer propensity is determined to estimate attractiveness of a substitute product to a customer based on one or more attributes. The cam frame has a body, at least three projection members extending from the cam frame body and inserted through the through-holes, at least three cam grooves formed in the cam frame body and the projection members to guide the cam members and to movably support the lens frame with respect to the cam frame body. This structure makes it possible for components to be used in common and integrated, and for the coupling surfaces between the lens block and the optical fibers to be gathered together in one place, thereby enabling cost reduction and size reduction.