OV6630 Datasheet, PDF (4/29 Pages) List of Unclassifed Manufacturers – SINGLE-CHIP CMOS CIF COLOR DIGITAL CAMERA

SINGLE IC CMOS COLOR AND B/W DIGITAL CAMERAS
1.2 Analog Processor Circuits
1.2.1 Overview
The image is captured by the 356 x 292 pixel image array and routed
to the analog processing section where the majority of signal
processing occurs. This block contains the circuitry that performs
color separation, color correction, automatic gain control (AGC),
gamma correction, color balance, black level calibration, “knee”
smoothing, aperture correction, controls for picture luminance and
chrominance, and anti-alias filtering. The analog video signals are
based on the following formula:
Y = 0.59G + 0.31R + 0.11B
U=R–Y
V=B–Y
Where R,G,B are the equivalent color components in each
pixel.
YCrCb format is also supported, based on the formula below:
Y = 0.59G + 0.31R + 0.11B
Cr = 0.713 (R – Y)
Cb = 0.564 (B – Y)
The YCrCb/RGB data signal from the analog processing section is
fed to two on-chip 8-bit analog-to-digital (A/D) converters: one for
the Y/RG channel and one shared by the CrCb/BG channels. The
converted data stream is further conditioned in the digital formatter.
The processed signal is delivered to the digital video port through the
video multiplexer which routes the user-selected 16-, 8-, or 4-bit
video data to the correct output pins.
The on-chip 8-bit A/D operates up to 9 MHz, and fully synchronous
to the pixel rate. Actual conversion rate is related to the frame rate.
A/D black-level calibration circuitry ensures:
⇒ The black level of Y/RGB is normalized to a value of 16
⇒ The peak white level is limited to 240
⇒ CrCb black level is 128
⇒ CrCb Peak/bottom is 240/16
⇒ RGB raw data output range is 16/240
(Note: Values 0 and 255 are reserved for sync flag)
1.2.2 Image Processing
The algorithm used for the electronic exposure control is based on the
brightness of the full image. The exposure is optimized for a “normal”
scene that assumes the subject is well lit relative to the background. In
situations where the image is not well lit, the automatic exposure
control (AEC) white/black ratio may be adjusted to suit the needs of
the application.
Additional on-chip functions include
⇒ AGC that provides a gain boost of up to 24dB
⇒ White balance control that enables setting of proper color
temperature and can be programmed for automatic or manual
operation.
⇒ Separate saturation, brightness, contrast, and sharpness
adjustments allow for further fine-tuning of the picture quality
and characteristics.
The OV6630 image sensor also provides control over the White
Balance ratio for increasing/decreasing the image field Red/Blue
component ratio. The sensor provides a default setting that may be
sufficient for many applications.
1.2.3 Windowing
The windowing feature of the OV6630/OV6130 image sensors allows
user-definable window sizing as required by the application. Window
size setting (in pixels) ranges from 2 x 2 to 356 x 292, and can be
positioned anywhere inside the 356 x 292 boundary. Note that
modifying window size and/or position does not change frame or data
rate. The OV6630/OV6130 imager alters the assertion of the HREF
signal to be consistent with the programmed horizontal and vertical
region. The default output window is 352 x 288.
1.2.4 Zoom Video Port (ZV)
The OV6630/OV6130 image sensor includes a Zoom Video (ZV)
function that supports standard ZV Port interface timing. Signals
available include VSYNC, CHSYNC, PCLK and 16-bit data bus:
Y[7:0] and UV[7:0]. The rising edge of PCLK clocks data into the ZV
port. See Figure 3. Zoom Video Port Timing below.
March 4, 2000
Version 1.0
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