Datasheet

PDF: 09005aef8202ec2e/Source: 09005aef8202ebf7 Micron Technology, Inc., reserves the right to change products or specifications without notice.
MT9D111__7_REV5.fm - Rev. B 2/06 EN
173 ©2004 Micron Technology, Inc. All rights reserved.
MT9D111 - 1/3.2-Inch 2-Megapixel SOC Digital Image Sensor
General Purpose I/O
Micron Confidential and Proprietary
filters are user-programmable within the following constraints: each can have 8 or 9
integer coefficients with values from -15 to 15, can be symmetric or antisymmetric, and
can be multiplied by a power-of-2 weight factor ranging from 1/512 to 32. By default,
both are programmed to detect sharp edges, but the first filter is more high-pass than
the second. Each filter is applied to successive locations in a window row, starting at the
first pixel and ending at the last. This requires using Y values from outside the window,
specifically from the 4 columns to the left and 4 columns to the right of the window.
Hence, when programming the size and position of the AF window grid, one should
make sure that every AF window intended to have non-zero weight is at least than 4 col-
umns away from the left and right side of the frame.
Figure 46: Auto Focus Windows
Figure 46 shows an array of 16 equal-size AF windows configured to work like a centered
quincunx pattern of 5 windows.
As the convolution of each AF filter with Y progresses along a window row, then to the
next row, and so on, absolute values of its successive results are added to a sum that ulti-
mately becomes a sum over the whole portion of the window located inside the frame. At
the same time, the pixels in the window are counted and their Y values are added up to
get the average Y for the window.
In this way, schematically depicted in Figure 47, each AF window not located fully out-
side the frame yields 2 sharpness scores (the sums of convolution results from the 2 AF
filters) and 1 average Y. The number of window rows processed to obtain these results
can be equal to or less than the common AF window height programmed into the regis-
ter R65:2. If and only if the window row count matches that height, the results are output
to registers. This never happens for AF windows positioned like W41 or W44 in
Figure 46—hence these windows are inactive. Results from each active AF window are
output immediately after its last row is processed.
W11 W12 W13 W14
W21 W22 W23 W24
W31 W32 W33 W34
W41 W42 W43 W44
Used active window (programmable weight > 0)
Unused active window (programmable weight = 0)
Inactive window (partly outside the frame, no sharpness score calculated)
FRAME
h
w
Programmable (x,y)
Programmable
window size (w,h)