Image Acquisition; Theory Of Ccd - Hamamatsu Photonics C9300-201 Instruction Manual

C9300-201 Ver.1.2

9. IMAGE ACQUISITION

9-1

THEORY OF CCD

The all-pixel-readout interline transfer CCD used in this camera is arranged as shown in
Figure 9-1. Incident light at the CCD is converted by photosensors to electrical charges
which are transmitted through a shielded vertical transfer CCD (VCCD) and a horizontal
transfer CCD (HCCD) to a final output charge-voltage conversion amp. The sensor gate is
opened by the readout signal, and the charges generated by all of the photosensors are
transmitted unmixed to the VCCD, completing the exposure.
In addition, an electronic shutter signal is applied to the CCD, allowing any accumulated
charge in the photosensors to be discharged.
● Binning
Accumulated charges for a specified number of pixels in the vertical and horizontal directions
on the CCD are calculated and combined (binned), then readout from the CCD. With this
camera, binning can be set to 2×2, where two pixels in the vertical and horizontal directions are
combined, 4×4, where four vertical and horizontal pixels are combined, or 8×8, where eight
vertical and horizontal pixels are combined.
● Exposure Time
When set to the normal CCD scanning mode, this is as shown in Figure 9-2.Exposure time is
the elapsed time between one readout signal and the next; this interval is at least as long as
the time necessary for all of the charges from the CCD to be readout.
● Dual readout
The CCD has dual readout amplifiers for the half left side area of the CCD and right side as
shown in Figure 9-1. When using single readout mode, only left side amplifier is used. And
when using dual readout mode, these two amplifiers are used at the same time for readout, so
you can obtain the image data with quite high frame rate.
12H
Photo-diode
On-chip AMP
Fig. 9-1
Exposure time
CCD exposure
Readut signal
from CCD chip
Digital data
output
Fig. 9-2
AMAMATSU PHOTONICS K.K.
Vertical CCD Sensor gate
Horizontal CCD
Readout period