TDI employs a temporal method of rendering greyscale images. This involves switching each pixel rapidly between light and dark states at a specific rate such that, when integrated by the HVS, constant luminance at the required level is perceived.
For example, a 4-bit per colour (R/G/B) system would allow each pixel element to render 16 grey-levels from black to white (note that grey levels are produced when the pixel has the same intensity value in all the R/G/B subfields). This is illustrated in Figure 1.  Each colour subfield uses a binary-weighted PWM light source. The 4-bit pixel value is split into four 1-bit binary values that are ‘displayed’ (i.e. the pixel is turned ON or OFF) according to their weight in the corresponding illumination time slot.
For example, Figure 1 shows that a pixel level of 0 (black) is never switched ON for any of the illumination pulses whereas a pixel value of 6 (grey level 6) is switched ON in the t/2 and t/4 illumination pulse slots.

Image 1

Figure 1: 4-bit greyscale

Arrays of pixels are handled in the same way. In the example outlined in Figure 1, an x*y pixel array would have all the bits of same significance for each colour grouped together in ‘bit-planes’. Consequently there would be twelve 1-bit bit-planes for a 4-bit R/G/B system, 4 bit-planes for each primary colour.  These bit-planes would drive each pixel according to the binary value of that pixel in the time slot associated for that bit-plane and colour.
This concept is further illustrated in Figure 2. This shows how the picture information is stored within each colour subfield and within their respective bit-planes and how they relate to the binary weighted PWM illumination scheme.

Figure 2: 8-bit per colour RGB system