kac-9628 ETC-unknow, kac-9628 Datasheet - Page 20

• Manufacturer Part Number: kac-9628
• Description: Kodak Kac-9628 Cmos Image Sensor 648 H X 488 V High Dynamic Range 30 Fps Color Cis
• Manufacturer: ETC-unknow

IMAGE SENSOR SOLUTIONS
Functional Description
7.0
7.1
The KAC-9628 has a built-in bad pixel detection and correction
block that operates on the fly. This block can be switched off by
the user.
7.2
In addition to the programmable gain the KAC-9628 has a built
in black level compensation block as illustrated in Figure 28.
This block can be switched off.
The black level compensation block subtracts the estimated
average black level from the digital video output to compensate
for the temperature and integration time dependent dark signal
level of the pixels. Figure illustrates the black level estimation
circuit built into the KAC-9618
After optional clipping (the Clip parameter in the BLCOEFF reg-
ister) of the MSB (used to remove the signal level of hot pixel
noise, the block estimates the average of the black signal level
by means of a low-pass filter that is applied to the series of black
pixel signals of the black pixels that are included in the scan win-
dow. This low-pass filter features a programmable time-con-
stant. The estimated average black level value is then
subtracted from the pixel data. During readout of active pixels,
the running average is frozen and not updated.
The transfer function (in Z-domain) of the low-pass filter in the
black level estimation block is given by:
where the gain G is programmable through α:
An increased value of α (the Alpha parameter in the BLCOEFF
register) increases the loop gain and therefore increases its
time-constant, resulting in a slower update of the integrator.
The actual black pixels used for the black level estimation is
dependent on the user defined scan window as illustrated in fig-
ure 30. In all cases only the inner 4 rows and columns are used.
www.kodak.com/go/imagers 585-722-4385
Figure 30. Black Pixels Used For Black Level Estimation
Limit to 0-127
SIGNAL PROCESSING
Bad Pixel Detection & Correction
Black Level Compensation
Figure 28. Digital Black Level Compensation.
X(z)
Figure 29. Black Level Estimation Circuit
Y z ( )
Pixel Array
Black Level Estimation
G
=
X z ( )
G
+
=
---------------------------
z
+
-
–
2 7
Integrator
–
(
(
G
1 G
z
–
G
+
-1
α
(continued)
Display Window
)
Black Pixels
+
)
Scan Window
-
Blank negative values
Black Pixels
used for black
level estimation
Y(z)
Bypass Mux
20
8.0
8.1
The KAC-9628 is equipped with an on-board power manage-
ment system allowing the analog and digital circuitry to be
switched off (power down) and on (power up) at any time.
The sensor can be put into power down mode by asserting a
logic one on the “pdwn” pin or by writing to the power down bit in
the main configuration register via the I
interface.
To power up the sensor a logic zero can be asserted on the
“pdwn” pin or write to the power down bit in the main configura-
tion register via the I
It will take a few milliseconds for all the circuits to power up. The
power management register contains a bit indicating when the
sensor is ready for use. During this time the sensor cannot be
used for capturing images. A status bit in the power manage-
ment register will indicate when the sensor is ready for use.
9.0
The level of the offset voltage determines the black level of the
image and has a direct impact on the image quality. Too high an
offset results in a white washed or hazy looking image, while too
low of an offset results in a dark image with low contrast even
though the light conditions are good.
For maximum image quality over a wide range of light conditions
it is necessary to set an appropriate offset voltage before using
the sensor to capture images.
The offset of each part can be adjusted by programming the off-
set control register (OCR) via the I
To calibrate the offset of a given part the following procedure
should be followed:
• Disable the black level compensation block by writing a logic
• Set the sensor’s gain to 1 by writing 00Hex to registers
• Calculate the average black level by reading a full frame and
• If the calculated average black level is greater than the target
• The offset can be adjusted by running the following binary
• For n=6 to 1 step -1
• {
• Enable the black level compensation block (if desired) by writ-
1 to bit 4 of the Main Configuration Register 0 (MCFG0:
address 02Hex).
VGAIN, GGAIN, BGAIN, RGAIN.
calculating the average black level (BL
last 5 black pixels in the every row of the array.
black level then set the OffSign bit of the OCR register to a
logic 1, else set it to a logic 0.
search algorithm on the OffMag parameter in the OCR regis-
ter:
ing a logic 0 to bit 4 of the Main Configuration Register 0
(MCFG0: address 02Hex)
}
POWER MANAGMENT
Power Up and Down
OFFSET ADJUSTMENT
else
writing over the I
Read a full frame and calculate the average black level
(BL
row of the array
If (BL
Set OffMag bit n in the OCR register to a logic one by
Reset OffMag bit n in the OCR register to 0
Keep OffMag bit n set to one.
average
average
) of the first and last 5 black pixels in the every
2
< 100) then
C compatible serial interface.
2
C compatible interface.
2
C compatible serial interface.
Email:[e-mail]
average
2
C compatible serial
) of the first and