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.
Two DMDs were developed oriented around 1280x720p and 1920x1080p high resolution
TV standards respectively. The new DMD diamond layout supports, in the case of the
1080p device, 1920x1080 resolution, with 960 distinct column pairs and 540 distinct row
pairs (a row pair consists of one black and one white row). This permits display of a
1920x1080 image using ½ the number of pixels in an orthogonal array, with some loss
of diagonal resolution. By using the diamond configuration, the 1080p DMD chip size
approaches that of the HD2 720p chip, creating a cost effective device which can
display additional vertical and horizontal resolution.
SmoothPicture Technology
While the diamond grid DMD effectively improves system cost, by itself it is
insufficient to display all of the original image pixels on the screen. The original image
would have to be filtered to produce an image with half the number of pixels of the
original image in order to be displayed on the DMD. TI's SmoothPicture technology
combines the diamond grid DMD, with its inherently high mirror switching speed and
an optical actuator to create a system which can display a full resolution image
onscreen containing all of the original image pixels. With SmoothPicture, the actuator
optically displaces the DMD image horizontally, coordinated with the display of two
separate subframes of data on the DMD (see Figure 3).
Figure 3. SmoothPictureTM Light Path
Utilizing the high switching speed of the DMD, both subframes of data
containing all of the original pixels in the image can be displayed within one 16ms
field time.
