Method and device for encoding luminance values into subfield code words in a display device

Method for encoding the luminance value of a pixel of a picture into a subfield code word in a display device, wherein each bit of the subfield code word has a state “ON” or “OFF” and generates a light emission during an own period called subfield when its state is “ON”, the light emitted for a pixel by the pixel's subfield code word being representative of the luminance value of said pixel and the total duration of the subfields associated to the bits of the subfield code word forming the picture frame, each sub-field having a weight proportional to the subfield's duration, wherein the bits of each subfield code word are computed recursively one after the other from the bit associated to the subfield having the most significant weight to the bit associated to the subfield having the least significant weight,

• wherein
• for the bit associated to the subfield having the most significant weight, allocating a state “ON” to said bit if the luminance value of the current pixel is equal to or greater than a threshold value associated to said bit, and
• for each following bit of the subfield code word, computing a remaining luminance value to be encoded by said bit comprising
• calculating the number of bits having the bit associated with said preceding subfield being in a “ON” state in a line of pixels to which a current pixel belongs,
• estimating a subfield luminance value for said subfield on the basis of said number of pixels being in an “ON” state,
• subtracting the estimated subfield luminance value from the luminance value to be encoded and allocating a state “ON” to the bit if the remaining luminance value is equal to or greater than a threshold value associated with said bit, in order that no line load will be visible.