DLPS021 September 2019 DLP470TP
During a given period of time, the nominal landed duty cycle of a given pixel follows from the image content being displayed by that pixel.
For example, in the simplest case, when displaying pure-white on a given pixel for a given time period, that pixel experiences a landed duty cycle very close to 100/0 during that time period. Likewise, when displaying pureblack, the pixel experiences a landed duty cycle very close to 0/100.
Between the two extremes (ignoring for the moment color and any image processing that may be applied to an incoming image), the landed duty cycle tracks one-to-one with the gray scale value, as shown in Table 5.
|GRAYSCALE VALUE||NOMINAL LANDED DUTY CYCLE|
Accounting for color rendition (but still ignoring image processing) requires knowing both the color intensity (from 0% to 100%) for each constituent primary color (red, green, and/or blue) for the given pixel as well as the color cycle time for each primary color, where “color cycle time” is the total percentage of the frame time that a given primary must be displayed in order to achieve the desired white point.
Use Equation 1 to calculate the landed duty cycle of a given pixel during a given time period
For example, assume that the red, green, and blue color cycle times are 50%, 20%, and 30% respectively (in order to achieve the desired white point), then the nominal landed duty cycle for various combinations of red, green, blue color intensities would be as shown in Table 6 and Table 7.
|SCALE VALUE||NOMINAL LANDED DUTY CYCLE|
The last factor to account for in estimating the landed duty cycle is any applied image processing. Within the DLPC6421 controllers, the gamma function affects the landed duty cycle.
Gamma is a power function of the form Output_Level = A × Input_LevelGamma, where A is a scaling factor that is typically set to 1.
In the DLPC6421 controllers, gamma is applied to the incoming image data on a pixel-by-pixel basis. A typical gamma factor is 2.2, which transforms the incoming data as shown in Figure 11.
From Figure 11, if the gray scale value of a given input pixel is 40% (before gamma is applied), then gray scale value is 13% after gamma is applied. Therefore,because gamma has a direct impact displayed gray scale level of a pixel, it also has a direct impact on the landed duty cycle of a pixel.
Consideration must also be given to any image processing which occurs before the DLPC3439 controllers.