MCM20027IBMN View Datasheet(PDF) - Motorola => Freescale
Part Name
Description
Manufacturer
MCM20027IBMN Datasheet PDF : 73 Pages
| |||
MOTOROLA
SEMICONDUCTOR TECHNICAL DATA
ImageMOS
7.3 Programmable Per-Column Offset
A programmable per-column offset adjustment is avail-
able on the MCM20027. In order to reduce the risk and
have the ability to cover any mode of repetitive column
Fixed Pattern Noise (FPN), there exists 64 registers that
can be programmed with a DC offset that is added to all
columns. (Mod64 Column Offset registers; Table 29).
Each register is 6 bits, (5 bits plus 1 sign bit), providing+/
- 32 register values. The DC register values are added to
each of the 64 columns registers to provide the total off-
set value. This set of 64 values is then repeatedly ap-
plied to each bank of 64 in the sensor via the column
DOVA stage of the ASP chain.
The Column DOVA DC Register; Table 28, is used to
set the initial offset of the pixel output in a range that will
facilitate per-column offset data generation for varying
operational conditions. In most operational scenarios,
this register can be left in its default state of 00h. This is
a pre-image processing gain in comparison to the Glo-
bal DOVA Register (see section )which is a post image
processing chain gain (pre A2D gain)
sten, and halogen to cover a wide gamut of illumination
conditions.
Both DPGA designs use switched capacitors to mini-
mize accumulated offset and improve measurement ac-
curacy and dynamic range. The white balance gain
registers are 6-bits and can be programmed to allow
gain of 0.696x to 2.74x in varying steps.
The user programs the individual gain coefficients into
the MCM20027 via the Color Gain Registers (Table 10
through Table 13 ). For the default Bayer configuration
of the color filter array; Figure 4, the Color Gain Register
addresses are as follows: Reg (00h): green pixel of a
green-red row; Reg (01h): red pixel; Reg (02h): blue pix-
el; and Reg (03h): green pixel of a blue-green row.
The MCM20027 is presently available with only a Bayer
CFA. This is accomplished via the Color Tile Config-
uration Register, (Table 14), on page 37 and the Color
Tile Row Definition registers (Table 15 through Table 18).
7.4 Digitally Programmable Gain Amplifiers (DPGA)
for White Balance and Exposure Gain
Two DPGAs are available in the analog signal process-
ing chain. These are used to perform white balance and
exposure gain functions.
7.4.1 White Balance Control PGA
The sensor produces three primary color outputs, Red,
Green and Blue. These are monochrome signals that
represent luminance values in each of the primary col-
ors. When added in equal amounts they mix to make
neutral color. White balancing is a technique where the
gain coefficients of the green(0), red, blue, and green(3)
pixels comprising the Bayer pattern (see Figure 14.) are
set so as to equalize their outputs for neutral color
scenes. Since the sensitivity of the two green pixels in
the Bayer pattern may not be equal, an individual color
gain register is provided for each component of the Bay-
er pattern.
Once all color gain registers are loaded with the desired
gain coefficients, according to which gain mode (see
“Gain Modes” on page 17) has been set, white balance
is then achieved in real time and in analog space. These
gain coefficient values are then selected and applied to
the pixel output via a high speed path, the delay of
which is much shorter than the pixel clock rate. Real
time updates can be performed to any of the gain regis-
ters. However, latency associated with the I2C interface
should be taken into consideration before changes oc-
cur. In most applications, users will be able to assign
predefined settings such as daylight, fluorescent, tung-
Green (0) 6
6
Red (1)
6
6
Blue (2)
6
Green (3)
G(0) R(1)
B(2) G(3)
DPGA
0.7x-2.7x
Figure 14. Color Gain Register Selection
7.4.2 Exposure Global Gain PGA
The global gain DPGA provides a 0.67x to 7.5x (approx)
programmable gain adjustment for dynamic range. The
gain of the amplifier is linearly programmable using a six
bit gain coefficients on 2 6-bit PGA gain registers in
varying steps depending on which exposure gain mode
it is set at, i.e. RAW or LIN or LIN2 (PGA Gain Mode,
(Table 27), on page 45). The user programs the global
gain via the Exposure PGA Global Gain Register A, (Ta-
ble 25), on page 44.
MOTOROLA
Revision 8.4 - 24 Oct 2002 : MCM20027
16
Share Link: 