Back to results
US 8,797,410 B2Granted
Image pickup apparatus, image pickup system, and method for driving image pickup apparatus
AssigneeCanon Kabushiki Kaisha
InventorDaisuke Yoshida
Life of this patent
Estimating the term…
Abstract
There are provided an image pickup apparatus, an image pickup system, and a method for driving the image pickup apparatus which perform correction of a reference potential used in an operation performed by a successive approximation AD conversion circuit and correction of a digital signal, into which a pixel signal which is output by a pixel is converted.
Claims16
A method for driving an image pickup apparatus including
- a pixel configured to output a pixel signal, and
- an AD conversion unit configured to convert the pixel signal into a digital signal, the AD conversion unit including a comparator configured to compare a reference signal with a signal based on the pixel signal and output a comparison result signal,
- the method comprising:
- determining signal values of higher-order bits of the digital signal based on the pixel signal by operating the AD conversion unit as one of a successive approximation AD conversion circuit and a ramp AD conversion circuit;
- and
- after the signal values of the higher-order bits are determined, determining signal values of lower-order bits of the digital signal based on the pixel signal by operating the AD conversion unit as the other one of the successive approximation AD conversion circuit and the ramp AD conversion circuit,
- wherein, when the AD conversion unit is operated as the ramp AD conversion circuit,
- the AD conversion unit generates a first digital signal on the basis of the comparison result signal which is output by the comparator supplied with a first ramp signal as the reference signal and a comparison signal and comparing the first ramp signal with the comparison signal,
- the AD conversion unit generates a second digital signal on the basis of the comparison result signal which is output by the comparator supplied with a second ramp signal as the reference signal and the comparison signal and comparing the second ramp signal with the comparison signal, the second ramp signal having a ramp start potential different from a ramp start potential of the first ramp signal,
- the image pickup apparatus generates a correction value on the basis of the first digital signal and the second digital signal,
- a first correction operation of correcting a reference potential on the basis of the correction value is performed, the reference potential being used when the AD conversion unit is operated as the successive approximation AD conversion circuit, and
- a second correction operation of correcting the digital signal based on the pixel signal on the basis of the correction value is performed.
9 more elements
An image pickup apparatus comprising:
- a pixel configured to output a pixel signal;
- an AD conversion unit configured to convert the pixel signal into a digital signal, the AD conversion unit including a comparator configured to compare a reference signal with a signal based on the pixel signal and output a comparison result signal;
- and
- a control circuit,
- wherein the control circuit
- determines signal values of higher-order bits of the digital signal based on the pixel signal by operating the AD conversion unit as one of a successive approximation AD conversion circuit and a ramp AD conversion circuit, and
- then determines signal values of lower-order bits of the digital signal based on the pixel signal by operating the AD conversion unit as the other one of the successive approximation AD conversion circuit and the ramp AD conversion circuit,
- wherein, when the control circuit causes the AD conversion unit to operate as the ramp AD conversion circuit,
- the AD conversion unit generates a first digital signal on the basis of the comparison result signal which is output by the comparator supplied with a first ramp signal as the reference signal and a comparison signal and comparing the first ramp signal with the comparison signal, and
- the AD conversion unit generates a second digital signal on the basis of the comparison result signal which is output by the comparator supplied with a second ramp signal as the reference signal and the comparison signal and comparing the second ramp signal with the comparison signal, the second ramp signal having a ramp start potential different from a ramp start potential of the first ramp signal,
- wherein the image pickup apparatus further includes a signal processing circuit supplied with the first digital signal and the second digital signal, and
- wherein the signal processing circuit includes
- a circuit configured to generate a correction value on the basis of the first digital signal and the second digital signal, and
- a circuit configured to perform a first correction operation of correcting a reference potential used when the AD conversion unit is operated as the successive approximation AD conversion circuit, on the basis of the correction value, and a second correction operation of correcting the digital signal, into which the pixel signal is converted, on the basis of the correction value.
11 more elements
An image pickup system comprising:
- an image pickup apparatus including
- a pixel configured to output a pixel signal,
- an AD conversion unit configured to convert the pixel signal into a digital signal, the AD conversion unit including a comparator configured to compare a reference signal with a signal based on the pixel signal and output a comparison result signal, and
- a control circuit;
- and
- an output signal processor,
- wherein the control circuit
- determines signal values of higher-order bits of the digital signal based on the pixel signal by operating the AD conversion unit as one of a successive approximation AD conversion circuit and a ramp AD conversion circuit, and
- then determines signal values of lower-order bits of the digital signal based on the pixel signal by operating the AD conversion unit as the other one of the successive approximation AD conversion circuit and the ramp AD conversion circuit,
- wherein, when the control circuit causes the AD conversion unit to operate as the ramp AD conversion circuit,
- the AD conversion unit generates a first digital signal on the basis of the comparison result signal which is output by the comparator supplied with a first ramp signal as the reference signal and a comparison signal and comparing the first ramp signal with the comparison signal, and
- the AD conversion unit generates a second digital signal on the basis of the comparison result signal which is output by the comparator supplied with a second ramp signal as the reference signal and the comparison signal and comparing the second ramp signal with the comparison signal, the second ramp signal having a ramp start potential different from a ramp start potential of the first ramp signal,
- wherein the output signal processor is supplied with the first digital signal and the second digital signal, and
- wherein the output signal processor includes
- a circuit configured to generate a correction value on the basis of the first digital signal and the second digital signal, and
- a circuit configured to perform a first correction operation of correcting a reference potential used when the AD conversion unit is operated as the successive approximation AD conversion circuit, on the basis of the correction value, and a second correction operation of correcting the digital signal, into which the pixel signal is converted, on the basis of the correction value.
13 more elements
Dependencies are inferred from the claim text.