A random access addressing of field emission lamp for local dimming lighting applications

In recent, field emission lamp (FEL) with carbon nanotube (CNT) field emitters was intensively studied for a high performance back light unit (BLU) in LCD. The CNT-FEL can give a local dimming BLU increasing contrast ratio, reducing motion blur and saving power consumption. The local FE blocks, in general, are arranged in a matrix format and addressed by voltage pulse signals. In this method the row bus selects a row line of local blocks consecutively and the column bus delivers a dimming signal to each block in the selected row line and vice versa as in a conventional matrix addressing, which is common and easy in CNT-FELs [1-3]. However, it has disadvantages of a high addressing voltage depending on the operation voltage of CNT emitters and a shortened duty as the increase in the number of local blocks. If the image is refreshed by a frequency of f and the number of row lines of local blocks is N then the duty time to each row line is given by 1/fN, which limits the whole luminance and the number of local blocks for a given panel size. Another demerit of conventional voltage driving is that it hardly makes up for the degradation of CNT emitters and so the lifetime of CNT-FEL may be solved by only the improvement in intrinsic property of CNT emitters.