Method of reducing alignment error between user device and lenticular lenses to view glass-free stereoscopic image and user device performing the same

A method of reducing an alignment error between a user device and lenticular lenses to view a glass-free stereoscopic image includes: (a) providing an angle adjustable user interface configured to display at least one interference pattern line and a reference line in a display area of the user device where the lenticular lenses attach; (b) receiving a user input to adjust a slant angle of the interference pattern line to the reference line; and (c) displaying the interference pattern line with an changed slant angle in response to the user input and defining a slant angle of the pixel line according to the changed interference pattern line. The pixel line is configured to include multiple lines represented by multiple pixels that constitute the display area of the user device and has a specific slant. The lens line refers to a pattern of multiple lines formed by multiple convex lenses that constitute the lenticular lenses and the interference pattern line is formed by the lens line and the pixel line.