Image sensor including noise removing unit, image pickup device having the image sensor, and image sensing method performed in the image sensor
An image sensor including a noise removing unit may sense images accurately by measuring the amount of noise generated when the image sensor does not perform a sensing operation, storing information about the measured noise amount in each pixel, and removing photocharge corresponding to the information about the measured noise amount during image sensing.
1. An image sensor comprising:
a photo sensitive device (PSD) configured to generate photocharges;
a storage node configured to store photocharges generated by the PSD;
a transfer switch connected between the PSD and the storage node, the transfer switch configured to control transfer of the photocharges generated by the PSD to the storage node in response to a transfer control signal; and
a noise removing circuit connected to the PSD, the noise removing circuit configured to generate and store a noise signal by detecting an amount of the photocharges generated by the PSD during an inactive period, and configured to remove photocharge corresponding to a noise component from among the photocharges generated in the PSD during an active period based on the noise signal, the inactive period being a period during which the transfer switch does not transfer photocharges from the PSD, the active period being a period during which the transfer switch transfers photocharges from the PSD.
2. The image sensor of claim 1 , wherein the noise removing circuit comprises:
a storage unit configured to sample and store the photocharge corresponding to the noise component; and
a noise removing unit configured to remove the photocharge corresponding to the noise component from among the photocharges generated in the PSD based on the sampled photocharge stored in the storage unit, in response to a control signal.
3. The image sensor of claim 1 , wherein the image sensor includes a plurality of pixels,
wherein the noise removing circuit is installed in each of the plurality of pixels or is shared by pixels from among the plurality of pixels.
4. The image sensor of claim 2 , wherein the storage unit comprises at least one capacitor configured to store the photocharge corresponding to the noise component.
5. The image sensor of claim 2 , wherein the noise removing unit comprises at least one transistor that is configured to be turned on/off in response to the control signal.
6. The image sensor of claim 5 , wherein the noise removing unit comprises:
a first transistor configured to turn on/off a path between the PSD and the storage unit in response to the control signal; and
a second transistor electrically coupled to the first transistor, and configured to adjust an amount of current in response to an amplitude of a voltage applied to the storage unit.
7. The image sensor of claim 5 , wherein the control signal is configured to be enabled during a period of time that corresponds to a unit of time during which a sensing operation is performed in the image sensor.
8. An image pickup device comprising:
an image sensor comprising a plurality of pixels and a control unit configured to control the plurality of pixels;
a central processing unit (CPU) configured to control an operation of the image sensor; and
a memory device configured to store an image provided from the image sensor under the control of the CPU,
wherein each of the plurality of pixels include
a photo sensitive device (PSD) configured to generate photocharges,
a storage node configured to store photocharges generated by the PSD,
a transfer switch connected between the PSD and the storage node, the transfer switch configured to control transfer of the photocharges generated by the PSD to the storage node in response to a transfer control signal; and
a noise removing circuit connected to the PSD, the noise removing circuit configured to generate and store a noise signal by detecting an amount of the photocharges generated by the PSD during an inactive period, and configured to remove photocharge corresponding to a noise component from among the photocharges generated in the PSD during an active period based on the noise signal, the inactive period being a period during which the transfer switch does not transfer photocharges from the PSD, the active period being a period during which the transfer switch transfers photocharges from the PSD.
9. The image pickup device of claim 8 , wherein the noise removing circuit comprises:
a storage unit configured to sample and store the photocharge corresponding to the noise component; and
a noise removing unit configured to remove the noise component from among the photocharges generated in the PSD based on the sampled photocharge stored in the storage unit, in response to a control signal generated by the control unit.
10. The image pickup device claim 8 , wherein the storage unit comprises at least one capacitor configured to store the photocharge corresponding to the noise component.
11. The image pickup device of claim 8 , wherein the noise removing unit comprises at least one transistor that is configured to be turned on/off in response to the control signal.
12. The image pickup device of claim 11 , wherein the noise removing unit comprises:
a first transistor configured to turn on/off a path between the PSD and the storage unit in response to the control signal; and
a second transistor connected to the first transistor, and configured to adjust an amount of current in response to an amplitude of a voltage applied to the storage unit.
13. The image sensor of claim 11 , wherein the control signal is configured to be enabled during a period of time that corresponds to a unit of time during which a sensing operation is performed in the image sensor.