US Patent No. 9,277,149

METHOD FOR DRIVING IMAGE PICKUP DEVICE, METHOD FOR CORRECTING DIGITAL SIGNAL, IMAGE PICKUP DEVICE, METHOD FOR DRIVING IMAGE CAPTURING SYSTEM, AND IMAGE CAPTURING SYSTEM


Patent No. 9,277,149
Issue Date March 01, 2016
Title Method For Driving Image Pickup Device, Method For Correcting Digital Signal, Image Pickup Device, Method For Driving Image Capturing System, And Image Capturing System
Inventorship Takashi Muto, Kawasaki (JP)
Seiji Hashimoto, Yokohama (JP)
Daisuke Yoshida, Ebina (JP)
Yasushi Matsuno, Fujisawa (JP)
Assignee CANON KABUSHIKI KAISHA, Tokyo (JP)

Claim of US Patent No. 9,277,149

1. A method for driving an image pickup device, the image pickup device comprising:
a pixel configured to output a pixel signal, and
an analog-to-digital conversion unit configured to convert an analog signal into a digital signal, the analog-to-digital conversion
unit comprising:

a comparison unit configured to output a comparison result signal obtained by comparing an analog signal with a reference
signal whose potential changes with time, and

a counting unit configured to generate a count value by counting a clock signal,
the method comprising:
generating, a first digital signal having the count value generated by the counting unit as a result of counting the clock
signal during a period from when the counting unit starts counting the clock signal in response to a timing at which a potential
of a first reference signal (Vr1) starts changing at the counting unit by a first amount per unit time, to when a signal value
of the comparison result signal obtained by comparing a first test signal being the analog signal with the first reference
signal changes;

generating, a second digital signal having the count value generated by the counting unit as a result of counting the clock
signal during a period from when the counting unit starts counting the clock signal in response to a timing at which a potential
of a second reference signal (Vr2) starts changing at the counting unit by a second amount per unit time which is greater
than the first amount, to when a signal value of the comparison result signal obtained by comparing the first test signal
with the second reference signal changes; and

generating, a third digital signal having the count value generated by the counting unit as a result of counting the clock
signal during a period from when the counting unit starts counting the clock signal in response to a timing at which a potential
of at least one of the first reference signal and the second reference signal starts changing, to when a signal value of the
comparison result signal obtained by comparing a signal of the analog signal based on the pixel signal with at least one of
the first reference signal and the second reference signal changes, wherein

the third digital signal is corrected on the basis of the first digital signal and the second digital signal, so as to reduce
an offset which is included in the third digital signal, and arises from a difference between the timing at which the potential
of at least one of the first reference signal (Vr1) and the second reference signal (Vr2) starts changing with time, and the
timing at which the counting unit starts counting the clock signal.