ACM100
Autobrite ®
number of pixels in the top bin of a histogram (of
programmable size) falls below the specified value.
The ACM100 module includes both automatic and manual
control of both the integration period and the dynamic range.
The automatic control may be based on the entire contents of
the image, or on a user specified region of interest. The
following sections describe the control in more detail.
In addition to setting the target values, the user may limit the
maximum gamma setting available to the algorithm. This may
be useful to applications that respond poorly to extremely high
gamma values.
Region of Interest
Transition Control
The camera includes a region of interest feature that can be
used to influence the automatic control of the dynamic range
and the integration period. The user designates a region of
interest (of programmable size and position) within the full
frame. The camera automatically optimizes the exposure and
dynamic range for this region (alternatively, the region can be
ignored for exposure and dynamic range setting). The region
is defined by specifying the upper left and lower right corners
of a rectangle using pixel row and column numbers.
The camera includes features that allow the user to influence
the response of the camera to dynamic lighting conditions.
Human vision applications may desire a slow, smooth
response to changes in lighting for aesthetic reasons. Machine
vision application, not being influenced by aesthetic concerns,
may desire a faster response. The camera includes features
to allow the user to adjust the dynamic response of the camera
to suit the application.
Image Processing Fetaures
Tint Control
The camera includes a number of features that improve or
remove artifacts from the image. These features are described
in the following sections.
The camera provides for both automatic and manual control of
the integration period (exposure time). This can be specified
independently of the gamma control – that is either can be
fixed or set automatically. The Tint control algorithm attempts
to set the camera to an integration period that places the
average pixel value at a default or user specified level.
Dark Current Removal
The camera automatically senses the dark current using
inactive, or dark, columns in the sensor. The current is
measured for each row and subtracted from the image. This
feature may be disabled by the user.
In addition to setting the desired image average, the user may
bound the integration period that is available to the automatic
control. This can prevent the integration from exceeding
motion blur limits in dark environments.
Column Fixed Pattern Noise Correction
During the vertical retrace period of scanning the imager, a
fixed voltage is applied to all of the columns of the imager. This
voltage is sampled by the ADC and used to calculate offset
errors on a column basis. These errors are then removed from
the next frame. This feature may be disabled by the user.
Gamma Control
The camera provides for both automatic and manual control of
the dynamic range by selecting one of 29 response, or
gamma, curves. This can be specified independently of the
Tint control – that is either can be fixed or set automatically.
Defective Pixel Correction
Autobrite tracks two parameters to control the selection of a
gamma code: the number of saturated pixels (those at the
maximum digital value) and the number of pixels in the top
histogram bin of the image. These parameters are tracked on
a per image basis using binary counters.
The camera includes a feature to compensate for defective
pixels. A 3x3 non-linear filter is used to screen out defective
pixels. The center pixel is compared against the average of its
neighbors and if it is too high or low, the average is substituted
for the defective pixel. This feature may be disabled by the
user.
The algorithm can be tuned by setting the number of bits active
in each counter. The logic responds to the overflow of the
counter. Therefore the maximum number of saturated pixels
and minimum number of top bin pixels desired are both set as
a power of two.
Sharpening Filter
The camera includes a 3X3 sharpening filter. The user may
disable or specify the strength of the filter.
The algorithm works by increasing the dynamic range when
the number of saturated pixels (max gray level) exceeds the
saturation setting. The dynamic range is reduced when the
Detailed Specifications
The following sections outline some of the detailed
specifications of the module.
Document Number: 001-05325 Rev. **
Page 7 of 20
CYPRESS [ CYPRESS ]
