Patent ID: 7327473

Claim:
A method comprising: capturing an image of a grating formed on a surface of a brightness enhancing display film; measuring a displacement Δd of a fringe from the image of the grating; and determining a slope of a deviation from flatness of the brightness enhancing display film from the displacement Δd by using the equation (I) Δ ⁢ ⁢ d ⁡ ( y , θ 2 ) = 2 ⁢ y ⁢ ⁢ sin ⁡ ( θ 1 + θ 3 - 2 ⁢ θ 2 ) [ tan ⁡ ( θ 1 + θ 3 - θ 2 - 90 ) tan ⁢ ( 90 - θ 2 ) + tan ⁡ ( θ 1 + θ 3 - θ 2 - 90 ) ] ( I ) wherein y represents a distance along the brightness enhancing display film that represents a location of the deviation from flatness; θ 1 is a light box angle; θ 2 is the slope of the deviation from flatness in the brightness enhancing display film; and θ 3 is a camera angle.