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iXon 3

Features & Functionality

3.3.5.2 - Baseline Clamp

Whenacquiringdatasmallchangesintheambienttemperatureand/orintheheatgenerationofthedrivingelectronics

within the camera may cause some drift in the baseline level. This is most often observed during long kinetic series.

Any drift in the baseline level can be corrected by using the Baseline Clamp option. Baseline Clamp corrects each

individual image for any baseline drift by subtracting an average bias signal from each image pixel and then adding 100

counts to ensure that the displayed signal level is always a positive number of counts.

NOTE: Before activating Baseline Clamp, please ensure that the baseline level is above zero counts for the

cooling temperature selected.

3.3.6 - Binning and Sub Image options

Binning is a process that allows charge from two or more pixels to be combined on the EMCCD-chip prior to readout.

Summing charge on the EMCCD and doing a single readout gives better noise performance than reading out several

pixels and then summing them in computer memory. This is because each act of reading out contributes to noise. There

are two types of the binning as follows:

• Vertical Binning: Where charge from two or more rows of the EMCCD-chip are moved down into the shift

Thus, for each column of the EMCCD-chip, charge from two or more vertical elements is summed into the

corresponding element of the shift register. The charge from each of the pixels in the shift register is then

shifted horizontally to the output amplier and read out.

• Horizontal Binning: Where charge from two or more pixels in the serial register are transferred into the output

amplier and read out as one combined data value. Thus the charge from two or more of the horizontal

elements is effectively summed into the output amplier before being readout.

Combiningboththeverticalandhorizontalbinningmethodsproduces“Superpixels”.Theseconsistoftwoormore

individual pixels that are binned and read out as one large pixel. Thus the whole CCD, or a selected sub-area becomes a

matrix of Superpixels, e.g.:

Thehorizontalandverticalbinningparametersdeterminethedimensionsofanysuperpixelscreated.Ontheonehand

superpixels result in a loss of spatial resolution when compared to single pixel readout, but on the other hand they offer

the advantage of summing data on-chip prior to readout thereby producing a better signal to noise ratio and a higher

framerate.AlliXon3modelsoffercompletelyexiblebinningpatternswhichareuser-selectablefromsoftware.

For the purpose of initial focusing and alignment of the camera, or to increase the readout speed, the user may wish to

only readout a particular sub-area of the CCD to produce a Sub Image.

When a sub image has been dened, only data from the selected pixels will be digitized. Data from the remaining pixels

willbediscarded.TheexiblecongurationoftheiXon3allowstheusertosettheSub Image area to any size and

location on the CCD chip.

Andor Technology iXon3 Series User Manual

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