Two-Line Averaging; Changes To The Data Output With Two-Line Averaging - Basler L800k User Manual

3.9.4 Two-line Averaging

With the two-line averaging feature, gray values from two line captures are averaged and reported
out as a single line. The feature is designed to increase the signal-to-noise ratio for applications
that require only half of the maximum line rate.
In two-line averaging mode, the signal-to-noise ratio will typically increase by 3 dB. The feature
can be used with both single and dual pixel output.
As shown in Figure 3-14, the camera will capture two lines, add the gray values of each pixel
together, divide the sum for each pixel by two to obtain an averaged gray value for each pixel and
output one line of pixels with the averaged gray value for each pixel.
When the pixel data is transmitted from the camera to the frame grabber, decimals are truncated.
Gray Values
in First Line
Gray Values
in Next Line
Summed
Gray Values
Summed
Gray Values
Averaged
Gray Values
Figure 3-14: Two-line Averaging

3.9.4.1 Changes to the Data Output with Two-line Averaging

In two-line averaging mode, the camera outputs pixel data for every second line that is triggered
and this line is the averaged line from the last two exposures.
For example, if you are operating in two-line averaging mode and you trigger 100 line captures,
the camera will actually output 50 lines.
Figure 3-15 on page
single 10 bit or single 8 bit output are enabled:
• After the first exposure, the line valid bit will stay low. No pixel data will be output for that line.
• After the second exposure, the line valid bit will become high. The bits transmitted during the
first clock cycle will contain the averaged data from the last two lines for pixel number one.
• On the second cycle of the pixel clock, the line valid bit will be high. The bits transmitted dur-
ing this clock cycle will contain the averaged data for pixel number two.
• This pattern will continue until all of the pixel data for the line has been transmitted.
• After all of the pixels have been transmitted, the line valid will become low indicating that
valid pixel data is no longer being transmitted.
• After the third exposure, the line valid bit will stay low.
• After the fourth exposure, the line valid bit will become high, and so on.
BASLER L800
k
199 201 202 200 200 201 201 200 199 201 200 201
+ + + + +
201 200 199 201 201 200 200 201 201 199 200 200
= = = = =
400 401 401 401 401 401 401 402 400 400 400 401
400 401 401 401 401 401 401 401 400 400 400 401
:2 :2 :2 :2 :2
200 200 200 200 200 200 200 200 200 200 200 200
3-34 shows the timing diagram that applies when two-line averaging and
Draft
+ + + + + +
= = = = = =
:2 :2 :2 :2 :2 :2
Operation and Features
+ +
= =
:2 :2
3-33