DLPU048 User guide

DLPU048E August 2016 – July 2024

5.5 Smooth Illumination Transition

The main application supports smooth transitions between sequences, or illumination bins, using digital contrast adjustments over a series of frames in order to attenuate the display brightness.

This feature prevents instantaneous changes in system brightness caused by large duty cycle differences in illumination bins.Figure 5-21 demonstrates an instantaneous brightness change that would occur without the use of this feature.

DLPC230-Q1 Instantaneous Duty Cycle Change

Figure 5-21 Instantaneous Duty Cycle Change

The following commands are used for this feature:

Illumination Transition Rate - Specifies the number of frames over which the transition will occur. This effectively determines the time of transition based on the frame period multiplied by the number of frames. Changes to the brightness are calculated and applied each frame despite the step size allowed by this command.
Illumination Bin Select - Specifies the illumination bin index that will be transitioned to. This command also triggers the start of the transition.

Note that this feature is only available while displaying external video or test patterns. It is not available while displaying splash images. While a splash image is displayed, the transition rate value is ignored and the commanded illumination bin will always be applied in one step.

When an Illumination Bin Select command is received, the main application begins transitioning brightness levels from the full digital brightness of the currently displayed illumination bin to the full digital brightness of the selected illumination bin. The main application uses the latest transition rate that was received prior to the start of the transition.

If an Illumination Bin Select command is received during an ongoing transition, the main application will terminate the ongoing transition by immediately switching to the last selected illumination bin. It will then start a new transition from the previously selected illumination bin to the newly selected illumination bin.

Figure 5-22 demonstrates the procedure that the main application performs to transition from a high brightness sequence to a low brightness sequence across 8 frames. Initially the system remains in the high brightness sequence and the digital contrast is decreased each frame so that the contrast-adjusted brightness of sequence 1 approaches the full-contrast brightness of sequence 2. On the last transition frame the contrast is returned to 1x and the sequence is transitioned to sequence 2. Figure 5-23 highlights the resulting total brightness of the combination of sequence and contrast brightness.

Figure 5-22 Duty Cycle Decrease

DLPC230-Q1 Duty Cycle Decrease Total Brightness

Figure 5-23 Duty Cycle Decrease Total Brightness

Figure 5-24 demonstrates the use of this function to transition from a low brightness sequence to a high brightness sequence across 8 frames. On the first transition frame, the sequence transitions to the high brightness sequence and the contrast is decreased to approximately match the low brightness sequence. Then the contrast is increased across the transition frames until the contrast returns to 1x. Figure 5-25 highlights the resulting total brightness of the combination of sequence and contrast brightness.

Figure 5-24 Duty Cycle Increase

DLPC230-Q1 Duty Cycle Increase Total brightness

Figure 5-25 Duty Cycle Increase Total brightness