Operation and Features
BASLER L304
kc 3-1
Draft
3 Operation and Features
3.1 Functional Description
The L304kc is a high resolution camera that employs a CCD sensor chip designed for color
scanning. The sensor contains three lines of photosensitive elements (pixels) with 4080 pixels per
line. One line is covered with a red filter, one line with a green filter and one line with a blue filter
to provide spectral separation.
Exposure time is normally controlled via an externally generated trigger signal (ExSync). The
ExSync signal facilitates periodic or non-periodic pixel readout.
When exposure is controlled by an ExSync signal, exposure time can be edge-controlled, level-
controlled or programmable. In edge-controlled mode, charge is accumulated over the full period
of the ExSync signal and a rising edge of ExSync triggers the readout of accumulated charges
from the sensor elements to the CCD shift registers. In level-controlled mode, charge is
accumulated when the ExSync signal is low and a rising edge of ExSync triggers the readout of
accumulated charges. In programmable mode, exposure time can be programmed to a
predetermined period. In this case, exposure begins on the rising edge of ExSync and
accumulated charges are read out when the programmed exposure time ends.
A free-run mode that allows the camera to operate without an ExSync signal is also available. In
free-run mode, the camera generates its own internal control signal and the signal is used to
control exposure and charge readout. When operating in free-run, the camera outputs lines
automatically.
At readout, accumulated charges are transported from each line of pixels to a separate shift
register (see Figure 3-1). As charges move out of the shift registers, they are converted to voltages
proportional to the amount of accumulated charge. The shifts are clocked according to the
camera’s internal data rate.
The voltages moving out of each shift register are digitized by a 14 bit analog-to-digital converter
(ADC). The camera’s gain and offset functions are performed on the pixel data using digital
means.
Depending on the spatial correction settings, the digitized data from the first two color channels is
held in a temporary memory (FIFO) until the corresponding data for the third channel arrives (see
Section 3.5). When the red, green and blue information for the first pixel is complete, the digitized
video data is transmitted from the camera to the frame grabber using a format compatible with the
Camera Link standard (see Section 2.5 for details).
When the camera is set for 3 tap output, it transmits pixels at 8 bit depth with a clock speed of 30
MHz. When the camera is set for 2 tap output depth, it can output pixels either at 10 bit or at 8 bit
depth and with a pixel clock speed of 60 MHz.
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