NOIV1SE5000A Datasheet, PDF (34/70 Pages) ON Semiconductor – VITA 5000 5.3 Megapixel 75 FPS Global Shutter CMOS Image Sensor

NOIV1SN5000A
Table 23. AEC SAMPLE SELECTION
Register Name
Description
192[10]
roi_aec_en-
able
When 0x0, all active windows are se-
lected for statistics calculation.
When 0x1, the AEC samples are
selected from the active pixels con-
tained in the region of interest defined
by roi_aec
253-255 roi_aec
These registers define a window from
which the AEC samples will be selec-
ted when roi_aec_enable is asserted.
Configuration is similar to the regular
region of interests.
The intersection of this window with
the active windows define the selec-
ted pixels. It is important that this win-
dow at least overlaps with one or
more active windows.
Important note for rolling shutter operation: a minimum
of 4 dummy lines is required when using the automatic
exposure controller.
Target Illumination
The target illumination value is configured by means of
register desired_intensity.
Table 24. AEC TARGET ILLUMINATION
CONFIGURATION
Register Name
161[9:0] desired_in­
tensity
Description
Target intensity value, on 10­bit scale.
For 8­bit mode, target value is con­
figured on desired_intensity[9:2]
Color Sensor
The weight of each color can be configured for color
sensors by means of scale factors. Note these scale factor are
only used to calculate the statistics in order to compensate
for (off-chip) white balancing and/or color matrices. The
pixel values itself are not modified.
The scale factors are configured as 3.7 unsigned numbers
(0x80 = unity).
Table 25. COLOR SCALE FACTORS
Register
Name
162[9:0] red_scale_factor
Description
Red scale factor for AEC statist-
ics
163[9:0] green1_scale_fa- Green1 scale factor for AEC
ctor
statistics
164[9:0] green2_scale_fa- Green2 scale factor for AEC
ctor
statistics
165[9:0] blue_scale_factor Blue scale factor for AEC stat-
istics
Configure these factors to their default value for
monochrome sensors.
AEC Filter Block
The filter block low-pass filters the gain change requests
received from the statistics block.
The filter can be restarted by asserting the restart_filter
configuration of register 160.
AEC Enforcer Block
The enforcer block calculates the four different gain
parameters, based on the required total gain, thereby
respecting a specific hierarchy in those configurations.
Some (digital) hysteresis is added so that the (analog) sensor
settings don’t need to change too often.
Exposure Control Parameters
The several gain parameters are described below, in the
order in which these are controlled by the AEC for large
adjustments. Small adjustments are regulated by digital gain
only.
• Exposure Time
In rolling shutter mode, the exposure time is the time
elapsed between resetting a particular line and reading it out.
This time is constant for all lines in a frame, lest the image
be non-uniformly exposed. The exposure time is always an
integer multiple of the line time.
In a snapshot shutter mode, the exposure is the time
between the global image array reset de-assertion and the
pixel charge transfer. The granularity of the integration time
steps is configured by the mult_timer register.
NOTE: The exposure_time register is ignored when the
AEC is enabled. The register fr_length defines
the frame time and needs to be configured
accordingly.
• Analog Gain
The sensor has two analog gain stages, configurable
independently from each other. Typically the AEC shall first
regulate the first stage. Optionally this behavior can be
inverted by setting the amp_pri register.
• Digital Gain
The last gain stage is a gain applied on the digitized
samples. The digital gain is represented by a 5.7 unsigned
number (i.e. 7 bits after the decimal point). While the analog
gain steps are coarse, the digital gain stage makes it possible
to achieve very fine adjustments.
AEC Control Range
The control range for each of the exposure parameters can
be pre-programmed in the sensor. Note that for rolling
shutter operation the maximum integration time should not
exceed the number of lines read out (i.e. the sum of black
lines, active window-defined lines and dummy lines).
Table 26 lists the relevant registers.
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