A method of designing a backlight module for a flat panel display device having a liquid crystal display, LCD, panel, the method comprising the steps of: a) defining mechanical and optical parameters for mechanical and optical components of the display device, wherein one or more of the mechanical parameters comprises: the mechanical distances to one or more active area, AA, lines representing the border of the active area of the display panel, including the distance from an edge of a middle frame to the AA line, the distance from an edge of an optic film to the AA line, the distance from an edge of a diffuser film to the AA line, the distance from an edge of a reflector sheet to the AA line, and the distance from an edge of a front cover to the AA line; the angle of one or more edges of a back cover backlight unit forming part of a flat panel display design; and the angle of one or more edges of a reflector sheet forming part of a flat panel display design; and wherein one or more of the optical parameters comprises: the number of lenses in a predefined region; and the lens ratio of one or more lenses forming part of a flat panel display design; b) generating a model based at least in part on the defined mechanical and optical parameters, the model defining one or more relationships between a luminance of the backlight module and one or more mechanical and one or more optical parameters as one or more linear equations; c) applying constraints on the values of the mechanical and optical parameters within the model; d) solving , utilising the model and said defined constraints, said one or more linear equations on a computer system using linear iterative methods to generate a configuration of mechanical and optical components forming a design of a backlight module which is optimised for said luminance; and e) generating a design for a backlight module based on said generated configuration. a) defining mechanical and optical parameters for mechanical and optical components of the display device, wherein one or more of the mechanical parameters comprises: the mechanical distances to one or more active area, AA, lines representing the border of the active area of the display panel, including the distance from an edge of a middle frame to the AA line, the distance from an edge of an optic film to the AA line, the distance from an edge of a diffuser film to the AA line, the distance from an edge of a reflector sheet to the AA line, and the distance from an edge of a front cover to the AA line; the angle of one or more edges of a back cover backlight unit forming part of a flat panel display design; and the angle of one or more edges of a reflector sheet forming part of a flat panel display design; and wherein one or more of the optical parameters comprises: the number of lenses in a predefined region; and the lens ratio of one or more lenses forming part of a flat panel display design; b) generating a model based at least in part on the defined mechanical and optical parameters, the model defining one or more relationships between a luminance of the backlight module and one or more mechanical and one or more optical parameters as one or more linear equations; c) applying constraints on the values of the mechanical and optical parameters within the model; d) solving , utilising the model and said defined constraints, said one or more linear equations on a computer system using linear iterative methods to generate a configuration of mechanical and optical components forming a design of a backlight module which is optimised for said luminance; and e) generating a design for a backlight module based on said generated configuration. <EOS>