Content Adaptive Illumination control (CAIC) is part of the IntelliBright™ suite of advanced image processing algorithms that adaptively enhances brightness and reduces power. In common real-world image content most pixels in the images are well below full scale for the for the R (red), G (green), and B (blue) digital channels input to the DLPC34xx. As a result of this, the average picture level (APL) for the overall image is also well below full scale, and the dynamic range for the collective set of pixel values is not fully used. CAIC takes advantage of the headroom between the source image APL and the top of the available dynamic range of the display system.
CAIC evaluates images on a frame-by-frame basis and derives three unique digital gains, one for each of the R, G, and B color channel. During image processing, CAIC applies each gain to all pixels in the associated color channel. The calculated gain is applied to all pixels in that channel so that the pixels as a group collectively shift upward and as close to full scale as possible. To prevent any image quality degradation, the gains are set at the point where just a few pixels in each color channel are clipped. Figure 20 and Figure 21 show an example of the application of CAIC for one color channel.
Figure 21 shows the gain that is applied to a color processing channel inside the DLPC34xx. Additionally, CAIC adjusts the power for the R, G, and B LED by commanding different LED currents. For each color channel of an individual frame, CAIC intelligently determines the optimal combination of digital gain and LED power. The user configurable CAIC settings heavily influence the amount of digital gain that is applied to a color channel and the LED power for that color.
As CAIC applies a digital gain to each color channel and adjusts the power to each LED, CAIC ensures the resulting color balance in the final image matches the target color balance for the projector system. Thus, the effective displayed white point of images is held constant by CAIC from frame to frame.
CAIC can be used to increase the overall image brightness while holding the total power for all LEDs constant, or CAIC can be used to hold the overall image brightness constant while decreasing LED power. In summary, CAIC has two primary modes of operation:
In power reduction mode, since the R, G, and B channels can be gained up by CAIC inside the DLPC34xx, the LED power can be reduced for any color channel until the brightness of the color on the screen is unchanged. Thus, CAIC can achieve an overall LED power reduction while maintaining the same overall image brightness as if CAIC was not used. Figure 22 shows an example of LED power reduction by CAIC for an image where the red and blue LEDs can consume less power.
In enhanced brightness mode the R, G, and B channels can be gained up by CAIC with LED power generally being held constant. This results in an enhanced brightness with no power savings.
While there are two primary modes of operation described, the DLPC34xx actually operates within the extremes of pure power reduction mode and enhanced brightness mode. The user can configure which operating mode the DLPC34xx will more closely follow by adjusting the CAIC gain setting as described in the software programmer's guide.