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Instruction Manual
SK1024U3HU
shar
ed_Glossary
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Instruction Manual SK1024U3HU © 2019-07 E
Glossary
Blooming
If by overexposure too many charge carriers are produced
in one or several photosensitive elements (pixels) of the
line sensor, the transport register is „flooded“ with charge
carriers, and also the following register bins are charged
over the saturation limit. This spreading of a local overex-
posure along a line is called „blooming“. In the resulting
video signal an overexposed area includes too many
pixels. In that area the geometric mapping between
image and object is not correct.
CCD line scan cameras with anti-blooming sensors direct
the abundant charge to a ”drain gate”. Charge overflow
into adjacent, less illuminated pixels is prevented.
Depending on pixel frequency and spectral range,
overexposure up to factor of 50 can thus be handled.
Exposure period
is the illumination cycle of a line scan sensor. It is the
integration time
plus the additional time to complete
the read-out of the accumulated charges and the output
procedure. While the charges from a finished line scan
are being read out, the next line scan is being exposed.
The exposure period is a function of the pixel number and
the
pixel frequency
. The minimum exposure period of
a particular line scan camera determines the maximum
line frequency
that is declared in the specifications.
Integration control
Cameras with integration control are capable of curtailing
the
integration
time within an
exposure period
. This
performs an action equivalent to a shutter mechanism.
Integration time
The light-sensitive elements of the photoelectric sensor
accumulate the charge that is generated by the incident
light. The duration of this charge accumulation is called
the integration time. Longer integration times increase
the intensity of the line scan signal, assuming constant
illumination conditions. The complete read-out of
accumulated charges and output procedure determines
the minimum
exposure period
.
Line frequency, line scan frequency
is the reciprocal value of the
exposure period
. The
maximum line frequency is a key criterion for line scan
sensors as this is the limiting factor for the scan velocity.
Optical resolution
Two elements of a line scan camera determine the optical
resolution of the system: first, the pixel configuration of
the line sensor and, secondly, the optical resolution of
the lens. The worst value is the determining value. In a
phased set-up, both are within the same range.
The optical resolution of the line sensor is primarily
determined by the number of pixels and secondarily by
their size and spacing, the inter-pixel distance. Currently
available line scan cameras have up to 12 000 pixels,
ranging from 4 to 14 µm in size and spacing, for sensors
up to 56 mm in length and line scan frequencies up to
83 kHz.
During a scanning run, the effective resolution perpen-
dicular to the sensor orientation is determined by the
velocity of the scan and by the
line frequency
Pixel frequency
The pixel frequency for an individual sensor is the rate
of charge transfer from pixel to pixel and its ultimate
conversion into a signal.
Region of Interest
A freely programmable window (region of interest, ROI)
can be applied to the line sensor so that only the pixel
information within the ROI can reach the memory.
By only illuminating these ranges, data volume and data
processing is accelerated for both line and area scan
acquisitions.
Constraint: the ROI memory allocation must be divisible
by 8.
Shading correction
Shading Correction
, section 3.2
SCM
Shading Correction Memory,
Shading Correction Memories and API Functions
,
section 3.2
SoI (Start of Integration)
In addition to
SoS
, cameras with
Integration Control
function generate an internal SoI-signal that initiates the
integration period.
SoS (Start of Scan)
is an internally generated trigger signal for sequential
control of the camera, The signal is induced either by an
internal counter or by an external line synchronization
signal, depending on the selected line synchronization
mode.
Synchronization
Advanced Synchronization Control
, section 4.2
