Lag cancellation in CMOS image sensors
First Claim
1. A method of operating a pixel cell, the method comprising:
- setting a potential on a photo-conversion device to a value approximately equal to a value of a potential barrier formed between the photo-conversion device and a floating diffusion region prior to generating charge in the photo-conversion device by applying a first potential to the photo-conversion device and the floating diffusion region which fills the photo-conversion device and the floating diffusion with charge and applying a second potential to the photo-conversion device and the floating diffusion region which removes charge from the photo-conversion device and the floating diffusion region, wherein the first potential is lower than the second potential;
generating charge in response to light incident on the photo-conversion device;
applying a third potential to the floating diffusion region;
reading out the third potential from the floating diffusion region; and
transferring the generated charge from the photo-conversion device to the floating diffusion region subsequent to reading out the third potential.
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Accused Products
Abstract
A pixel cell with improved lag characteristics without increased noise. The pixel cell according to embodiments of the invention includes a photo-conversion device and a floating diffusion region switchably coupled to the photo-conversion device. The pixel cell includes a reset transistor, which has a first terminal electrically connected to the floating diffusion region and a second terminal switchably coupled to first and second voltage sources. The first voltage source is higher than the second voltage source. The pixel cell operates by returning a potential on the photo-conversion device to a value approximately equal to a value of a potential barrier between the photo-conversion device and the floating diffusion region prior to generating charge in the photo-conversion device.
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Citations
12 Claims
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1. A method of operating a pixel cell, the method comprising:
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setting a potential on a photo-conversion device to a value approximately equal to a value of a potential barrier formed between the photo-conversion device and a floating diffusion region prior to generating charge in the photo-conversion device by applying a first potential to the photo-conversion device and the floating diffusion region which fills the photo-conversion device and the floating diffusion with charge and applying a second potential to the photo-conversion device and the floating diffusion region which removes charge from the photo-conversion device and the floating diffusion region, wherein the first potential is lower than the second potential; generating charge in response to light incident on the photo-conversion device; applying a third potential to the floating diffusion region; reading out the third potential from the floating diffusion region; and transferring the generated charge from the photo-conversion device to the floating diffusion region subsequent to reading out the third potential. - View Dependent Claims (2, 3, 4)
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5. A method of operating a pixel cell, the method comprising:
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applying a first potential to a photo-conversion device and a floating diffusion region which fills the photo-conversion device and the floating diffusion with charge; applying a second potential to the photo-conversion device and the floating diffusion region which removes charge from the photo-conversion device and the floating diffusion region; wherein the first potential is lower than the second potential; generating charge in response to light incident on the photo-conversion device during an integration period; after the integration period, applying a third potential to the floating diffusion region; reading out the third potential from the floating diffusion region; and transferring the photo-generated charge from the photo-conversion device to the floating diffusion region subsequent to reading out the third potential; and reading out the photo-generated charge from the floating diffusion region. - View Dependent Claims (6, 7, 8)
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9. A method of operating an image sensor comprising an array of pixel cells, the method comprising:
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applying a first potential to a photo-conversion device in each pixel cell and a floating diffusion region which fills the photo-conversion device and the floating diffusion with charge in each pixel cell; applying a second potential to the photo-conversion device in each pixel cell and the floating diffusion region in each pixel cell which removes charge from the photo-conversion device and the floating diffusion region, wherein the first potential is lower than the second potential; in each pixel cell, generating charge in response to light incident on the photo-conversion device during an integration period; after the integration period, applying a third potential to the floating diffusion region in each pixel cell; and reading out the third potential from the floating diffusion region in each pixel cell. - View Dependent Claims (10, 11, 12)
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Specification