Pixel Response: Linear And Linlog Modes - Dalsa 1M28-SA User Manual

1M28, 1M75, and 1M150 User's Manual
Operating mode
LOG-Mode
LinLog2-Mode
HighGain
Linehopping
Decimation
MROI/ROI
Linepause

1.6 Pixel Response: Linear and LinLog Modes™

Three principal modes of pixel response are possible: Linear response, LinLog response for high
dynamic imaging, and logarithmic response for high dynamic imaging.
Linear Response
In the linear response mode, the camera works similar to a classical CCD camera, integrating the
photo-generated charges in each pixel during the exposure time. In this mode, the output signal is a
linear function of the number of photons accumulated in each pixel during the integration time. If
the number of photons accumulated in one pixel exceeds the pixel capacity, the pixel saturates, and
the output signal is truncated to the maximum level.
This mode is advantageous if linearity of the response is needed over the whole dynamic range,
and for applications with intrascene dynamics up to 40dB-60dB amplitude.
LinLog
In situations involving high intra-scene contrast, you can achieve compression of the upper gray
level region when you use LinLog technology. At low intensities, each pixel has a linear response;
at high intensities, the response changes to a logarithmic compression. This prevents the saturation
of the pixel response and permits an extremely high intra-scene dynamic above 120dB. The
threshold when the pixel passes from a linear to a logarithmic response is programmable by
software. Special care has been invested to keep this transition continuous and smooth. The
LinLog response is compatible with the global shutter technique (all pixels are exposed at the same
time) which prevents motion artefacts known from classical logarithmic sensors. LinLog
technology further overcomes image lag, or ghost images related to the slow response speed of
pure logarithmic sensors. The LinLog response is best suited for applications with uncontrolled
DALSA
PRELIMINARY
Description
for details.
Pure logarithmic mode: The pixels function as simple photo-diodes and are
continuously exposed to the light source.
Because of the diode characteristics, the high gain mode must be active. With
this mode, it is necessary to perform FPN correction because variations in the
pixel structures directly influence the image quality. For details, see section
1.6 Pixel Response: Linear and LinLog Modes™.
Linear-logarithmic mode: Increases the intra-scene dynamic range by up to
120dB without losing the advantages of a global shutter. For details, see
section 1.6 Pixel Response: Linear and LinLog Modes™.
Gain 4: Increases the gain in the analog path by a factor of 4, making the
camera more sensitive. See section 1.7 Gain Response for details.
Line jump: Individual lines are selectively jumped over and not output. The
maximum frame rate increases linearly. See section 1.10 Line Hopping
Mode for details.
Pixels are jumped over in the x- and y-directions while retaining the image
diagonal.
(Multiple) Region Of Interest: Selected windows of the sensor are read out,
reducing the quantity of data at constant resolution. For details, see section
1.9 Mask Mode (MROI).
A break in the clock cycles, occurring after the line has been output and
before starting readout of the next line. Improves the image quality for non-
centered ROI and allows adaptation to framegrabber requirements.
TM
Response
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