Patent ID: 7956883

Claim:
A light-emitting device comprising: a plurality of light-emitting elements whose luminous energy is controlled according to a current value and a pulse width of a driving signal; a storage unit that stores first and second coefficients for every light-emitting element; a pulse width determining unit that determines the pulse width of the driving signal supplied to each light-emitting element on the basis of the first coefficient for the corresponding light-emitting element stored in the storage unit and a grayscale value designated for the corresponding light-emitting element by grayscale data; a current value determining unit that determines a current value of the driving signal supplied to each light-emitting element on the basis of the second coefficient for the corresponding light-emitting element stored in the storage unit; a driving unit that supplies the driving signal having the current value determined by the current value determining unit within the pulse width determined by the pulse width determining unit to the corresponding light-emitting element; and a coefficient determining unit that calculates the first coefficient based on a target value of a light amount of any of the light-emitting elements and a first peak light amount of one of the light-emitting elements, and calculates the second coefficient based on a second peak light amount of one of the light-emitting elements and a luminous efficiency constant, wherein a variation in the light emission characteristic of each light-emitting element when the pulse width is changed and the current value of the driving signal is fixed is different from a variation in the light emission characteristic thereof when the current value is changed and the pulse width of the driving signal is fixed, the first and second coefficients stored in the storage unit are selected so that the luminous energy of the individual light-emitting elements when the same grayscale value is designated by the grayscale data are almost equal to one another and variations in the light emission characteristics of the plurality of light-emitting elements driven by the driving signals from the driving unit are substantially equal to one another, the pulse width determining unit determines the pulse width of the driving signal by multiplying the grayscale value designated by the grayscale data by the first coefficient stored in the storage unit, and when the driving signal having the current value determined such that the peak light amount of any one of the light-emitting elements becomes a target value P 0 is supplied and one light-emitting element emits light in a peak light amount Pa, the first coefficient Ka for the one light-emitting element stored in the storage unit satisfies the following expression: Ka= ( P 0/ Pa ) m/(m−l) (where m is a real number).