Functional Description
Version 1.4, March 6, 2003
Proprietary to OmniVision Technologies
3
Omni ision
Image Sensor Array
The OV7640/OV7141 CAMERACHIPS has an active image
array size of 640 columns x 480 rows (307,200 pixels).
However, the full array contains 652 columns and 486
rows, with the extra 6 rows used for black-level calibration
(“Optical Black”) and color interpolation information.
Figure 3 shows a cross-section of the image sensor array.
Figure 3 Image Sensor Array
Timing Generator
In general, the timing generator controls these functions:
•
Array control and frame generation (VGA and QVGA
outputs)
•
Internal timing signal generation and distribution
•
Frame rate timing
•
Automatic Exposure Control (AEC)
•
External timing outputs (VSYNC, HREF and PCLK)
Analog Processing Block
This block performs all analog image functions including:
•
Automatic Gain Control (AGC)
•
Automatic White Balance (AWB)
•
Image quality controls including:
– Color saturation
–Hue
–Gamma
– Sharpness (edge enhancement)
– Anti-blooming
– Zero smearing
Color Filter
Microlens
Photo Diode
A/D Converters
After the Analog Processing Block, the color channel data
signal is fed to two 8-bit Analog-to-Digital (A/D) converters
via the multiplexers, one for the Y/G channel and one
shared by the CrCb/BR channels. These A/D converters
operate
at
speeds
up
to
12MHz,
and
are
fully
synchronous to the pixel rate (actual conversion rate is
related to the frame rate).
In addition to the A/D conversion, this block also has the
following functions:
•
Digital Black-Level Calibration (BLC)
•
Optional U/V channel delay
•
Additional A/D range controls
In general, the combination of the A/D Range Multiplier
and A/D Range Control sets the A/D range and maximum
value to allow the user to adjust the final image brightness
as a function of the individual application.
Output Formatter
This block controls all output and data formatting required
prior to sending the image out.
Digital Video Port
These two bits increase IOL / IOH drive current and can be
adjusted as a function of the customer’s loading:
SCCB Interface
The Serial Camera Control Bus (SCCB) interface controls
the
CAMERACHIP
operation.
Refer
to
OmniVision
Technologies Serial Camera Control Bus (SCCB)
Specification for detailed usage of the serial control port.
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