Alt and Pleshko

An extension of this analysis to the general case of A 1 addressing scheme, where A is an arbitrary multiple of the column voltage, shows (Bigelow et al., 1974 Alt and Pleshko, 1974) that R is given by... 

The maximum number of scanned lines of a matrix display having RMS response is, according to Alt and Pleshko, equal to... 

Liquid crystal displays typically respond to the root-mean-square (rms) value of an applied voltage waveform. Applying this fact to the multiplexed addressing schemes which are conventionally used, Alt and Pleshko showed that the ratio of the voltages across selected and unselected display segments cannot exceed [ (y5ffl)/( 4 -l) where N is the number of rows in the matrix. We now ask whether some unconventional addressing scheme exists which would allow us to surpass this limit. 

In the multiplexing scheme considered by Alt and Pleshko, rectangular voltage pulses with duty ratio 1/N and a common amplitude are applied to each of the N rows in succession. These row signals Fj, which may be called strobe signals, are mutually orthogonal and have identical rms values F, i.e.. 

By substituting Eqs. (6), (7) and (8) into (4), and solving for the maximum voltage across an on-element subject to the constraint that the normalized voltage across an off-element does not exceed unity, the Alt and Pleshko result is obtained ... 

The on-voltage given by Eq. (9) constitutes the upper limit, not only for the pulsed waveforms considered by Alt and Pleshko, but also for any multiplexed addressing scheme so defined. Thus, no other set of orthogonal strobe functions, such as sinusoids of different frequencies or Walsh functions of different sequencies, can lead to better performance. We will show next that this limit can be exceeded if the functional dependence of a ) is more general than in Eq. (8). 

P. M. Alt and P. Pleshko. Scanning limitations of liquid-crystal displays. Electron Devices, IEEE Transactions on, 21(2) 146-155, 1974. 

To find the value of that maximises N, we take the derivative of N with respect to and set it equal to zero. This gives us the values of and that maximise N, along with the maximised value of N, N, for what is known as the Alt-Pleshko optimisation condition. 

Figure 26. Transmission behavior of a pixel of a slow-and a fast-responding LCD switched to the activated light state by Alt-Pleshko addressing.

L= 1, for active addressing L=A, while typically for multiline addressing the value of 2v=4... 7. AA and MLA require a different set of row and column signals from Alt-Pleshko addressing. These will be considered in the following ... 

Fig. 2.2 The optional amplitude selection technologies. Driving wave forms of a-to-1 amplitude selection, such as (a) Alt-Pleshko (AP) method and (b) amplitude selection (AS) method...

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