Appeal No. 1998-1698
Application No. 08/411,033
in the imaging part 2 of the CCD 1 during the unused charge integration
period.
In FIG.10, vertical transfer pulses NI and NS substantially corresponding to
the number of vertical picture elements or rows in the imaging part 2 are
generated twice, that is, shortly before the beginning of the vertical blanking
period and shortly after the vertical blanking period, thereby obtaining the
shortened substantial integration period T . Also, the anti-blooming gate
1
pulses NABG are applied continuously during the period T and are applied
1
intermittently during the period T . In addition, in the second embodiment,
2
during the accumulation of the unwanted charges, the level of the pulses NI is
set not to the middle level 1M but instead to the low level 1L in order to
increase the efficiency of the charge elimination through the regions ABG.
This decreases the quantity of charges which remain in the picture elements
in the imaging part 2.
The reason for this level setting will be explained with reference to FIGS.
11(a) and 11(b). FIGS. 11(a) and 11(b) show potential distributions in the
imaging part 2 when the level of the pulse NI is at the level IM and IL
respectively. In FIG. 11(a), the sum of the charges Q1 accumulated in each
region CW and the charges Q2 accumulated in each region VW after the
elimination of excess charge through the regions ABG becomes the
maximum charge quantity. On the other hand, in FIG. 11(b) the sum of the
charges Q3 accumulated in each region VW after the elimination of excess
charges through the regions ABG becomes the maximum charge quantity.
Apparently, the quantity of charges which remain at the end of the unwanted
charge integration period T is decreased more in FIG. 11(b) than in FIG.
2
11(a), thus reducing the quantity of charges which are to be eliminated by
vertical transfer, and thereby decreasing the overflow of charge which takes
place during the vertical transfer period of the charges at the beginning of the
substantial integration.
Also, as is understood from the comparison between FIGS. 11(a) and 11(b),
since the storage capacity of the imaging part 2 during the period T is
2
increased, it is possible to reduce the likelihood that the excess charges
would overflow from the imaging part 2 to the storage part 3 and destroy the
signal to be read out from the storage part 3.
6
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