Internal Process Controls - Control of Color Imaging Systems: Analysis and Design - page 502

Controllable space for level 2

Actual TRC

100%

75%

Ideal TRC curve

50%

25%

25% 50% 75% 100%

% Area coverage (input)

FIGURE 9.17 Schematic diagram representing the TRC with controllable space using

process actuators (charge and development bias).

Actual TRC

100%

75%

50%

25%

Compensation or
TRC inverse

50% 75% 100%

25%

% Area coverage (input)

FIGURE 9.18 Schematic diagram representing the inverse TRC obtained to achieve the
desired reference TRC.

level 3 controls, since these higher level controls can provide extra degrees of freedom
that lower level (charge and developability) controls cannot. The level 3 control
system generates the inverse curve (Figure 9.18) for each separation [26]. This
curve can be obtained by inverting the measured TRC over a reference TRC.
In another scenario presented in Figure 9.19, it appears as though there is

suf cient actuator space to obtain the desired tone curve. However, we are still not

able to reach full inversion with three point level 2 controls because of insuf cient

sampling; sampling of only three (low, mid, and high area coverages) is suf cient for

inversion. A time-sequential sampling proposed in Ref. [15] may provide reliable
control for such systems for a given area coverage (or gray level); during each