Shutter for CCD imager
View Patent ↗A CCD sensor has a shutter to prevent frame shift smear during transfer of an image from the image region to a store region. The CCD sensor has an extended dynamic range, because each integration is in two parts, the second part of which has a different sensitivity than the first part. In order to avoid an asymmetry in the uncovering and covering of the image region, a two-bladed shutter is used.
1. A combination of a shutter and a CCD having an image region, wherein the image region has a different charge capacity over a second portion of each integration from a charge capacity over a first portion, and wherein the shutter comprises a pair of blades mounted for rotation about an axis and arranged so that the image region is uncovered by a trailing edge of a second blade of the pair of blades and covered by a leading edge of a first blade of the pair of blades, to allow the first portion of integration to take place, and uncovered by a trailing edge of the first blade and covered by a leading edge of the second blade, to allow the second portion of integration to take place.
2. A combination as claimed in claim 1 , in which the edges all extend in a radial direction.
3. A combination as claimed in claim 1 , including a motor for driving the rotation of the blades.
4. A combination as claimed in claim 3 , including a counterweight.
5. A combination as claimed in claim 1 , including means to adjust the width of the gap between the blades corresponding to the second portion of the integration period.
6. A combination as claimed in claim 1 , wherein the image region comprises an array of pixels, a pair of electrodes being associated with each pixel which can be clocked to enable two-phase charge transfer to take place, an anti-blooming structure associated with the pixels, and electrode pulsing means for combining the charges collected under the pair of electrodes at each pixel under one only of the electrodes of each pair, at least once during a first portion of each integration period, but not during a second period of each integration period.