Evaluation method of the light distribution characteristics of the light flux control member in the surface light source device, the evaluation device and evaluation program

摘要

PROBLEM TO BE SOLVED: To provide a method for evaluating luminous flux control members capable of individually evaluating light distribution characteristics of a luminous flux control member for use in a surface light source device with a light-emitting element defined as a light source.SOLUTION: The method for evaluating luminous flux control members includes the steps of: capturing an image of an exit surface of a light diffusion member 13 and acquiring a first luminance distribution on the exit surface of the light diffusion member 13; calculating, on the first luminance distribution, a polynomial approximation function corresponding to a luminance on a straight line that passes through an intersection between an optical axis of a light-emitting element 11 and the exit surface of the light diffusion member 13 and that is parallel to the exit surface of the light diffusion member 13; and evaluating the light distribution characteristics of a luminous flux control member 12 on the basis of a first order differential value and a second order differential value in a predetermined point of an approximate curve corresponding to the polynomial approximation function.