Patent ID: 8325331

Claim:
A method for obtaining an incident angle θ i used in a panel having at least one icon, comprising steps of: providing a panel having an icon, wherein the icon has a plurality of protrusions, each of the protrusion has a plurality of edges and a plurality of draft angles at inner and outer sides of the edges, and wherein a light-emitting source is disposed under the icon; obtaining a distance W between two centers of two bottoms of two trenches formed at two sides of one of the plurality of protrusions; obtaining a half of the distance W; obtaining a vertical distance H between the light-emitting source and a center of the distance W; performing an inverse trigonometric function operation for the half of the distance W over the vertical distance H so as to obtain the incident angle θ i ; and causing each of the draft angles to be one of angles equal to and larger than the incident angle θ i to make a light on the icon of the panel even.