Patent ID: 7737937

Claim:
A scanning backlight unit (BU) for a matrix display ( 1 ), the scanning backlight unit (BU) comprising: a plurality of light sources (L 1 , . . . , Ln), a driver ( 2 ) for supplying drive signals (D 1 , . . . , Dn) to the light sources (L 1 , . . . , Ln), a controller ( 3 ) for controlling the driver ( 2 ) to separately activate the light sources (L 1 , . . . , Ln) to obtain light-emitting regions ( 5 ) being active, and a light sensor ( 4 ) being associated with a group of at least two of the light sources (L 1 , . . . , Ln) to supply a sensor signal (SES) indicating a luminance (LU) of the group to the controller ( 3 ), the controller ( 3 ) being arranged for reading the sensor signal (SES) at different instants (ts 1 , . . . , tsn) at which mutually different subsets of the light sources (L 1 , . . . , Ln) of the group are active, to control the driver ( 2 ) for supplying power levels to the light sources (L 1 , . . . , Ln) of the group for obtaining a luminance (LU 1 , . . . , LUn) of each one of the light sources (L 1 , . . . , Ln) of the group in dependence on the sensor signal (SES).