The SmoothPicture Algorithm
By David C. Hutchison, Texas Instruments and DLP TV, February 21, 2007
dThis white paper will discuss Texas Instruments (TI) SmoothPicture technology.
A diamond grid Digital Micromirror Device (DMD) is coupled with an optical actuator to
produce smooth, film-like picture in a DLP technology-based rear projection display
system while revealing the entire resolution of the input image.
Referring to Figure 4, each incoming video frame is parsed into the two separate
subframes, one subframe containing all of the odd image pixels, the other containing all of the even pixels. The 16ms video field time is subdivided into two 8ms subfield times.
During the first subfield time, the odd subframe data is displayed. At the beginning
of the second subfield time, the actuator horizontally shifts the DMD image by ½ pixel, and the even subframe data is displayed. The resulting onscreen image contains all of the
pixels in the original image frame, and is constructed within one 60Hz video field time.
Figure 4. The result of moving the offset diamond
DMD by 1/2 pixel.
Note that even though a diamond grid DMD is used, the horizontal displacement
methodology recreates the original orthogonal grid of the HD image frame. An additional
benefit of the ½ pixel displacement is that it effectively softens the pixel edges. In static
orthogonal displays (using a 1 mirror to 1 pixel display ratio) the mirror edges are distinctly visible which in some display technologies results in the familiar screen door effect. With SmoothPicture, this artifact is mitigated resulting in a seamless, more film-like image.
