A/D converter, solid-state image sensing device, and camera system
An A/D converter includes: a first comparator that compares an input signal, with a first reference signal which is a ramp wave having a predetermined polarity, and that when the input signal matches the first reference signal, reverses an output signal thereof; a second comparator that compares the input signal, with a second reference signal which is a ramp wave having a different polarity from the first reference signal, and that when the input signal matches the second reference signal, reverses an output signal thereof; and a counter capable of counting up so as to measure the comparison times taken by the first comparator and second comparator, wherein when either of the output signal of the first comparator and the output signal of the second comparator is first reversed, the counter ceases a counting action.
1. A solid-state image sensing device comprising:
a pixel array having a plurality of pixels, which performs photoelectric conversion, arrayed in the form of a matrix; and
pixel signal reading circuits that read pixel signals from the pixel array in units of a plurality of pixels, wherein the pixel signal reading circuits each include, correspondingly to columns of pixels,
a first comparator that compares an input signal with a first reference, signal, which is a ramp wave having a predetermined polarity, and, when the input signal matches the first reference signal, reverses an output signal thereof,
a second comparator that compares the input signal with a second reference signal, which is a ramp wave having a different polarity from the first reference signal, and, when the input signal matches the second reference signal, reverses an output signal thereof, and
a counter configured to measure comparison times taken by the first comparator and second comparator, and
when either the output signal of the first comparator or the output signal of the second comparator is reversed, the counter ceases a counting action, wherein
the solid-state image sensing device further comprises a reference voltage production unit configured to produce, together with the first reference signal, the second reference signal whose slope is vertically opposite to the slope of a standard voltage of the first reference signal, wherein
during P-phase level processing, during which a reset level attained in a pixel is read, the reference voltage production unit produces the first reference signal but not the second reference signal; and
during D-phase level processing, during which a photoelectrically converted signal level is read, the reference voltage production unit produces the first reference signal and the second reference signal.
2. The solid-state image sensing device according to claim 1 , wherein each of the pixels includes:
an output node;
a photoelectric converter that converts a light signal into an electric signal and accumulates signal charge;
a transfer element that is turned on or off with a driving signal and that when being turned on, transfers the charge in the photoelectric converter to the output node; and
a reset element that resets the output node with a reset signal.
3. A camera system comprising:
a solid-state image sensing device; and
an optical system that forms a subject image on the solid-state image sensing device, wherein
the solid-state image sensing device includes
a pixel array having a plurality of pixels, which performs photoelectric conversion, arrayed in the form of a matrix, and
pixel signal reading circuits that read pixel signals from the pixel array in units of a plurality of pixels, wherein
the pixel signal reading circuits each include, correspondingly to columns of pixels,
a first comparator that compares an input signal with a first reference signal, which is a ramp wave having a predetermined polarity, and, when the input signal matches the first reference signal, reverses an output signal thereof,
a second comparator that compares the input signal with a second reference signal, which is a ramp wave having a different polarity from the first reference signal, and, when the input signal matches the second reference signal, reverses an output signal thereof, and
a counter configured to count to measure the comparison times taken by the first comparator and second comparator; and
when either the output signal of the first comparator or the output signal of the second comparator is reversed, the counter ceases a counting action, wherein
the solid-state image sensing device further comprises a reference voltage production unit configured to produce, together with the first reference signal, the second reference signal whose slope is vertically opposite to the slope of a standard voltage of the first reference signal, wherein
during P-phase level processing during which a reset level attained in a pixel is read, the reference voltage production unit produces the first reference signal but not the second reference signal; and
during D-phase level processing during which a photoelectrically converted signal level is read, the reference voltage production unit produces the first reference signal and the second reference signal.
4. A solid-state image sensing device comprising:
a pixel signal reading circuit corresponding to a column of pixels,
a first comparator that compares an input signal with a first reference signal, which is a ramp wave having a predetermined polarity, and, when the input signal matches the first reference signal, reverses an output signal thereof;
a second comparator that compares the input signal with a second reference signal, which is a ramp wave having a different polarity from the first reference signal, and, when the input signal matches the second reference signal, reverses an output signal thereof;
a counter configured to count to measure the comparison times taken by the first comparator and second comparator, and when either the output signal of the first comparator or the output signal of the second comparator is reversed, the counter ceases a counting action; and
the solid-state image sensing device further comprises a reference voltage production unit configured to produce, together with the first reference, signal, the second reference signal whose slope is vertically opposite to the slope of a standard voltage of the first reference signal, wherein
during P-phase level processing, during which a reset level attained in a pixel is read, the reference voltage production unit produces the first reference signal but not the second reference signal.
5. The solid-state image sensing device according to claim 4 , wherein
during D-phase level processing, during which a photoelectrically converted signal level is read, the reference voltage production unit produces the first reference signal and second reference signal.
6. The solid-state image sensing device according to claim 5 , wherein each pixel of the column of pixels includes:
an output node.
7. The solid-state image sensing device according to claim 6 , wherein each pixel of the column of pixels includes:
a photoelectric converter that converts a light signal into an electric signal and accumulates signal charge.
8. The solid-state image sensing device according to claim 7 , wherein each pixel of the column of pixels includes:
a transfer element that is turned on or off with a driving signal and that when being turned on, transfers the charge in the photoelectric converter to the output node.
9. The solid-state image sensing device according to claim 8 , wherein each pixel of the column of pixels includes:
a reset element that resets the output node with a reset signal.
10. A camera system comprising a solid-state image sensing device according to claim 4 .
11. A camera system comprising a solid-state image sensing device according to claim 5 .
12. A camera system comprising a solid-state image sensing device according to claim 9 .