JAJSF42B April 2018 – June 2019 DLPC3478
Content-adaptive illumination control (CAIC) is an image processing algorithm that takes advantage of the fact that in common real-world image content most pixels in the images are well below full scale for the for the R, G, and B digital channels being input to the DLPC3478 device . As a result of this the average picture level (APL) for the overall image is also well below full scale, and the system’s dynamic range for the collective set of pixel values is not fully utilized. CAIC takes advantage of this headroom between the source image APL and the top of the available dynamic range of the display system.
CAIC evaluates images frame by frame and derives three unique digital gains, one for each of the R, G, and B color channels. During CAIC image processing, each gain is applied to all pixels in the associated color channel. CAIC derives each color channel’s gain that 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 24 and Figure 25 show an example of the application of CAIC for one color channel.
Figure 25 shows the gain that is applied to a color processing channel inside the device. CAIC also adjusts the power for the R, G, and B LED. For each color channel of an individual frame, CAIC determines the optimal combination of digital gain and LED power. The decision regarding how much digital gain to apply to a color channel and how much to adjust the LED power for that color is heavily influenced by the software command settings sent to the device for configuring CAIC.
As CAIC applies a digital gain to each color channel independently, and adjusts each LED’s power independently, CAIC also makes sure that 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.
Because the R, G, and B channels can be gained up by CAIC inside the device, the LED power can be turned down 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 26 shows an example of LED power reduction by CAIC for an image where the R and B LEDs can be turned down in power.
CAIC can alternatively be used to increase the overall brightness of an image while holding the total power for all LEDs constant. In summary, when CAIC is enabled CAIC can operate in one of two distinct modes: