c15bc1 aptina, c15bc1 Datasheet - Page 37

• Manufacturer Part Number: c15bc1
• Description: Mt9d014 1/4-inch 2mp Cmos Digital Image Sensor
• Manufacturer: aptina

Features
Shading Correction (SC)
The Correction Function
Image Acquisition Modes
PDF: 0526161444/Source:6112702771
MT0D014_DS - Rev. J 5/10 EN
Pcorrected row, col
1. Set R0x3780–1 = 0x0000.
2. Load SC coefficients.
3. Set R0x3780–1 = 0x8000.
Lenses tend to produce images whose brightness is significantly attenuated near the
edges. There are also other factors causing fixed pattern signal gradients in images
captured by image sensors. The cumulative result of all these factors is known as image
shading. The MT9D014 has an embedded shading correction module that can be
programmed to counter the shading effects on each individual Red, GreenB, GreenR,
and Blue color signal.
Color-dependent solutions are calibrated using the sensor, lens system, and an image of
an evenly illuminated, featureless grey calibration field. From the resulting image the
color correction functions can be derived.
The correction functions can then be applied to each pixel value to equalize the
response across the image as follows:
where P are the pixel values and f is the color-dependent correction function for each
color channel.
Each function includes a set of color-dependent coefficients defined by registers
R0x3600–3726. The function's origin is the center point of the function used in the
calculation of the coefficients. Using an origin near the central point of symmetry of the
sensor response provides the best results.
The correct sequence to write to the SC registers is as follows:
To read the SC coefficients, SC should be disabled (set R0x3780–1 = 0x0000) before
reading the register values.
The MT9D014 supports ERS mode. When the MT9D014 is streaming, it generates frames
at a fixed rate, and each frame is integrated (exposed) using the ERS. Timing and control
logic within the sensor sequences through the rows of the array, resetting and then
reading each row in turn. In the time interval between resetting a row and subsequently
reading that row, the pixels in the row integrate
incident light. The integration (exposure) time is controlled by varying the time between
row reset and row readout. For each row in a frame, the time between row reset and row
readout is fixed, leading to a uniform integration time across the frame. When the
integration time is changed (by using the two-wire serial interface to change register
settings), the timing and control logic controls the transition from old to new integration
time in such a way that the stream of output frames from the MT9D014 switches cleanly
from the old integration time to the new while only generating frames with uniform inte-
gration.
(
)= Psensor(row,col) * f(row,col)
37
MT9D014: 1/4-Inch 2Mp CMOS Digital Image Sensor
Aptina reserves the right to change products or specifications without notice.
©2007 Aptina Imaging Corporation. All rights reserved.
Preliminary
Features
(EQ 5)