CMOS TDI image sensor with rolling shutter pixels
View Patent ↗An improved complementary metal oxide semiconductor image sensor for time delay and integration imaging is provided that utilizes rolling shutter pixels. Columns of rolling shutter pixels in the CMOS image array are provided with a space between adjacent pixels to provide synchronization with movement of the subject in the along track direction. Preferably, the physical offset between the pixels is 1/Nth of a pixel pitch for a column having N rows.
1. A CMOS image sensor for time delay integration (TDI) imaging of a subject that is moving with respect to the CMOS image sensor in an along track direction, the CMOS image sensor comprising:
a two-dimensional array of photosensitive elements each operable in a rolling shutter mode, the array having a plurality of columns of photosensitive elements aligned in the along track direction, each of the photosensitive elements in a column separated by a physical offset to compensate for integration periods of the photosensitive elements in the rolling shutter mode of operation; and
a plurality of column buses, each of the plurality of columns of photosensitive elements coupled to a corresponding one of the plurality of column buses;
wherein the two-dimensional array of photosensitive elements has N rows, the photosensitive elements have a pixel pitch, and the physical offset is 1/N th of the pixel pitch.
2. The CMOS image sensor of claim 1 , further comprising a control circuit coupled to the plurality of column buses, the control circuit configured to read the photosensitive elements from the two-dimensional array by row sequentially.
3. The CMOS image sensor of claim 2 , further comprising an integration circuit coupled to the plurality of column buses to integrate the read photosensitive elements.
4. The CMOS image sensor of claim 1 , wherein the physical offset compensates for the movement of the subject in the along track direction during readout of the two-dimensional array.
5. The CMOS image sensor of claim 1 , wherein the physical offset synchronizes the movement of the subject with the integration period of a subsequent photosensitive element in the column.
6. The CMOS image sensor of claim 1 , wherein photosensitive elements operable in rolling shutter mode have an integration period that starts at the end of the last read operation and ends at the start of a subsequent read operation.
7. An imaging device for capturing a subject in a plurality of frames, the subject moving relative to the imaging device, the imaging device comprising:
a two-dimensional array of photosensitive elements having a plurality of columns of the photosensitive elements, each of the columns coupled to a column bus, adjacent photosensitive elements in each column defining a space therebetween to compensate for synchronizing an integration period of the photosensitive elements with the subject in subsequent frames;
wherein the two-dimensional array of photosensitive elements has N rows, the photosensitive elements have a pixel pitch, and the space is 1/N th of the pixel pitch.
8. The imaging device of claim 7 , wherein the photosensitive elements are CMOS rolling shutter pixels.
9. The imaging device of claim 8 further comprising an integration circuit for summing the plurality of frames to improve a signal to noise ratio.