Glossary of Terms
96
Y directions producing one “super” pixel equivalent to the total charge of the four
original pixels. It should be noted that binning does reduce resolution capability;
however, it increases sensitivity and improves (i.e. lowers) the overall CCD readout
time. End-users are cautioned that there is a limit to the effectiveness of hardware
binning as a result of the horizontal serial shift register and output node not having
infinite capacity to store charge. This physical limitation is best exemplified for
applications that have a very small signal superimposed on a large background. In
practice, the pixels associated with the horizontal register have twice the full well
capacity of their light sensitive counterparts, while the output node usually can hold
four times that of the photosensitive area. Thus, experiments where the summed
charge exceeds either the full well capability of the horizontal shift register and/or the
output node will be lost from a data processing point of view.
Charge Coupled Device
A Charge Coupled Device (CCD) is a light sensitive silicon chip that is used as a two-
dimensional photo-detector in digital cameras for both imaging and spectroscopic
applications. With respect to spectroscopic applications, the CCD simultaneously
measures intensity, X-position (wavelength) and Y-position (slit height) differences
projected along the spectrograph image plane.
CCD sensors are offered by a number of manufacturers and come in a variety of
sizes, chip architectures and performance grades to best meet the application at hand.
Charge Transfer Efficiency (CTE)
The percentage of charge moved from one pixel to the next is the charge transfer
efficiency. The CCD has a high CTE if the pixels are read out slowly. As the speed at
which the charge is transferred is increased, increasing amounts of the charge is left
behind. The residual charge combines with the charge of the next pixel as it is moved
into the cell. Therefore, using too high a transfer rate deforms the image shape; it
smears the charge over the pixels that follow in the readout cycle. Temperature also
affects CTE. Under normal operation the CTE is approximately 99.9995%. Below –
140 °C the movement of the charges becomes sluggish, and, again, the image
becomes smeared.
Correlated Double Sampling (CDS)
This sampling method utilizes a differential measurement technique to achieve a
higher precision measurement for each pixel processed during the CCD readout cycle.
This difference measurement (B-A) is accomplished by making two voltage
measurements for each pixel processed as follows:
•
Measurement A: Residual output amplifier charge during CCD reset time
•
Measurement B: Real charge plus the residual associated with the current
pixel being processed
Electronic circuitry that employs this CDS measurement technique is especially
important to properly characterize pixel response at low signals levels, since a minute
Summary of Contents for JOBIN YVON SYNAPSE
Page 1: ...SYNAPSE CCD Detection System User Manual Part Number 81100 Revision 2...
Page 10: ...Preface x...
Page 14: ...System Description and Specifications 4...
Page 28: ...Detector System Installation 18...
Page 38: ...Initial Power up and Operation 28...
Page 48: ...Temperature Control 38...
Page 72: ...Appendix A Dimensional Drawings 62 Figure 17 Distance from Focal Plane to CCD Chip...
Page 73: ...Appendix A Dimensional Drawings 63 Figure 18 Synapse Power Supply Unit...
Page 74: ...Appendix A Dimensional Drawings 64...
Page 86: ...Appendix C Performing Routine Procedures with SynerJY 76...
Page 100: ...Appendix E Accessories 90...
Page 104: ...Warranty 94...
Page 113: ...103 Notes...
Page 114: ...104 Notes...