Increasing Sensitivity With Binning - Dalsa Piranha HN HN-80-08k40-R User Manual

Piranha HN RoHS User Manual

Increasing Sensitivity with Binning

Binning increases the camera's light sensitivity by decreasing horizontal and/or vertical resolution—the
charge collected by adjacent pixels is added together. Binning is also useful for increasing frame rate
(vertical binning) or increasing the pixel pitch. For example, if you set your vertical binning to 2 and your
horizontal binning to 2, your pixel size increases from 7µm x 7µm (no binning) to 14 µm x 14 µm (2 x 2
binning).
Generally, digital binning prevents sensor blooming, while analog binning is better for noise. For 2x
binning in either direction, the noise is improved by a factor of 2 in analog binning and sqrt2 in digital
binning.
EXSYNC Considerations with Binning
A line scan and TDI scan CCD both require a synchronization signal (ExSync) to track the relative motion
between the CCD and the object to be imaged. The ExSync signal is provided by the mechanical system
that controls the motion and is typically generated by a shaft encoder. The shaft encoder is configured to
provide one signal every time the relative distance travelled is equal to the "object pixel" size. The object
pixel size is determined by the magnification factor of the lens. For example, with a 7x7 um ccd pixel and
with a 0.5 x magnification, the object pixel size is 14x14 um. In other words, the smallest feature that the
CDD can distinguish is 14 um. In this system, the shaft encoder should be configured to provide a pulse
each time the object moves by 14 um. This principle applies for both a line scan (1 line) and TDI scan type
CCD.
The TDI CCD can provide the additional feature called binning in which groups of pixels can be added
together or "binned". This provides for a higher response at the expense of lower resolution. For
example, with 2x2 binning of pixels of 7x7 um each, the effective pixel size is now 14x14 um. Careful
consideration must be given to the ExSync signal when binning is enabled since binning will change the
object pixel size. With a 0.5x magnification, the new 14 um pixel provides a object pixel size of 28x28 um.
Therefore, the ExSync signal from the shaft encoder must be re-configured to provide a pulse each time
the object moves by 28 um.
Note:
That if the speed of the liner motion remains the same with no binning and with 2x2 binning, then
the ExSync frequency with 2x2 binning will then become ½ the frequency used for no binning.
The same principle applies with 4x4 binning. The shaft encoder pulse occurrence must be re-configured
for the new and bigger object pixel size.
Setting Horizontal Analog Binning
Purpose: Increases the horizontal pixel pitch and light sensitivity by decreasing horizontal
resolution. The amount of data being sent from the camera is reduced by the horizontal
Teledyne DALSA
Figure 10: 2x2 Binning in Area Mode
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