User`s manual

Acquisition Control AW00049313000

74 Basler runner

8.1.2 Defining a Frame on Color Cameras

As with any other line scan camera, the sensor in a Gigabit Ethernet (GigE) camera is used to

perform a series of line acquisitions as an object passes the camera. But unlike many other

cameras, GigE line scan cameras do not transmit the pixel data from each individual line to a host

PC immediately after the line acquisition is complete. Instead, GigE cameras accumulate acquired

lines in a buffer and assembles them into a "frame". When enough line acquisitions have been

accumulated to constitute a complete frame, the frame is transmitted via an Ethernet network to a

host PC. An acquired frame, therefore, represents a single complete image acquired by the camera.

When a line acquisition is triggered on a color camera, all three physical lines in the camera’s

sensor are exposed at the same time. If the spatial correction feature on the color camera is

disabled, the pixel data collected by the sensor’s red line, green line, and blue line is combined to

form a single line with red, green, and blue data available for each pixel in the line. This single line

is then added to the frame buffer.

With the spatial correction feature enabled, the camera operates differently. When a line acquisition

is performed, all three physical lines are exposed at the same time and the pixel data acquired by

the sensor’s red line, green line, and blue line is stored in a line memory. Based on the spatial

correction settings, the camera then retrieves stored red line, green line, and blue line data. It

combines this "spatially corrected" data to form a single line with red, green, and blue data available

for each pixel in the line. This single, spatially corrected line is then added to the frame buffer.

For more information about spatial correction, see Chapter 9 on page 131.

Three camera parameters, X Offset, Width, and Height are used to define what will constitute a

frame.

The X Offset and Width parameters determine which pixels in the camera’s sensor lines will be used

for each line acquisition. The X Offset determines the first pixel to be used and the Width determines

the number of pixels to be used. The pixels in the sensor lines are numbered starting with 0.

Assume, for example, that you are working with a camera that has 2098 pixels in each sensor line,

that the X Offset parameter is set to 0, and that the Width parameter is set to 2098. In this case, all

of the pixels in each line would used in each line acquisition.

As another example, assume that the X Offset parameter is set to 10 and the Width parameter is

set to 25. With these settings, pixels 10 through 34 in each of the three lines would be used in each

line acquisition as shown in Figure 29.

Fig. 30: Pixels Used for Each Line Acquisition

123456789101112131415 192021 2822 23 24 25 26 27 3429 30 31 32 33 35 36 37 38 39 4016 17 180

X Offset

Width

= red pixels included in each acquisition

= green pixels included in each acquisition

= blue pixels included in each acquisition