Image sensor and operating method
An image sensor includes unit pixels of a first pixel group sharing a first floating diffusion region and associated with a single color filter, and unit pixels of a second pixel group sharing a second floating diffusion region and associated with the single color filter. Control logic may generate an image by obtaining capacitance having a first value from the first floating diffusion region at a first time, and obtaining capacitance having a second value different from the first value from the second floating diffusion region at a second time following the first time. The first pixel group and the second pixel s group have different sensitivity levels.
1. An image sensor comprising:
a pixel array including:
a first pixel group including a first unit pixel and a second unit pixel sharing a first floating diffusion region and associated with a color filter, and
a second pixel group including a third unit pixel and a fourth unit pixel sharing a second floating diffusion region and associated with the color filter;
a sampling circuit configured to:
detect at least one reset voltage and at least one pixel voltage from at least one of the first pixel group and the second pixel group, and
provide a difference between the reset voltage and the pixel voltage as an analog signal;
an analog-to-digital converter configured to compare the analog signal with a ramp voltage to generate a comparison result, convert the comparison result into a digital signal, and provide the digital signal as image data; and
a signal processing circuit configured to generate an image using the image data, wherein:
the signal processing circuit is further configured to:
detect a first reset voltage and a first pixel voltage from the first floating diffusion region;
detect a second reset voltage and a second pixel voltage from the second floating diffusion region;
take an average of the first reset voltage and the second reset voltage to calculate a reset average value; and
take an average of the first pixel voltage and the second pixel voltage to calculate a pixel average value,
the first pixel voltage of the first pixel group corresponds to charges generated by the first unit pixel and the second unit pixel in response to incident light and simultaneously summed in the first floating diffusion region, and
the second pixel voltage of the second pixel group corresponds to charges generated by the third unit pixel and the fourth unit pixel in response to incident light and simultaneously summed in the second floating diffusion region.
2. The image sensor of claim 1 , wherein the first pixel group and the second pixel group have different sized light receiving areas.
3. The image sensor of claim 1 , wherein a frame rate is higher than a frame rate in which an image is generated using image data from all unit pixels individually.
4. The image sensor of claim 1 , wherein:
each one of the first unit pixel, the second unit pixel, the third unit pixel, and the fourth unit pixel includes a photodiode and a transfer transistor connected to the photodiode,
the first unit pixel and the second unit pixel are connected to a first pixel circuit, and
the third unit pixel and the fourth unit pixel are connected to a second pixel circuit.
5. The image sensor of claim 4 , wherein the first pixel circuit includes:
a first driving transistor configured to generate a voltage corresponding to charge accumulated in the first floating diffusion region,
a first select transistor configured to provide a voltage generated by the first driving transistor to the sampling circuit, and
a first reset transistor configured to reset the first floating diffusion region.
6. The image sensor of claim 5 , wherein the second pixel circuit includes:
a second driving transistor configured to generate a voltage corresponding to charge accumulated in the second floating diffusion region,
a second select transistor configured to provide a voltage generated by the second driving transistor to the sampling circuit, and
a second reset transistor configured to reset the second floating diffusion region.
7. The image sensor of claim 1 , wherein the image sensor:
adjusts ON/OFF timing of respective transfer transistors of the first pixel group to be the same, and
adjusts ON/OFF timing of respective transfer transistors of the second pixel group to be different.
8. The image sensor of claim 7 , wherein unit pixels of the first pixel group provide a first subgroup exhibiting a first sensitivity level and a second subgroup exhibiting a second sensitivity level different from the first sensitivity level, depending on ON/OFF timing of the respective transfer transistors of the first pixel group.
9. The image sensor of claim 8 , wherein the first subgroup and the second subgroup have different incident light receiving areas.
10. An image sensor comprising:
a pixel array including unit pixels, wherein:
the unit pixels include a first unit pixel and a columnar-adjacent second unit pixel sharing a first floating diffusion region, associated with a single color filter, and forming a first pixel group, and
the unit pixels include a third unit pixel and a columnar-adjacent fourth unit pixel sharing a second floating diffusion region, associated with the single color filter, and forming a second pixel group different from the first pixel group; and
control logic configured to generate an image by:
obtaining capacitance having a first value from the first floating diffusion region at a first time, and
obtaining capacitance having a second value different from the first value from the second floating diffusion region at a second time following the first time, wherein:
the control logic is further configured to:
detect a first reset voltage and a first pixel voltage from the first floating diffusion region,
detect a second reset voltage and a second pixel voltage from the second floating diffusion region,
take an average of the first reset voltage and the second reset voltage to calculate a reset average value, and
take an average of the first pixel voltage and the second pixel voltage to calculate a pixel average value,
the first pixel voltage corresponds to a first capacitance value of the first floating diffusion region at the first time, and
the second pixel voltage corresponds to a second capacitance value of the second floating diffusion region at the second time.
11. The image sensor of claim 10 , wherein among unit pixels having a color different from a color of the single color filter and sharing another color filter adjacent to the single color filter, at least a portion of the unit pixels shares the second floating diffusion region with the second pixel group.
12. The image sensor of claim 10 , wherein the control logic is further configured to generate:
first image data from the capacitance having the first value,
generate second image data from the capacitance having the second value, and
generate the image using the first image data and the second image data.
13. The image sensor of claim 12 , wherein the control logic is further configured to take an average of the first image data and the second image data to calculate an average value and generate the image using the average value.
14. The image sensor of claim 12 , wherein:
the control logic is further configured to generate the image by obtaining capacitance having a third value from the second floating diffusion region at a third time following the second time,
generate third image data from the capacitance having the third value, and
generate image data using the third image data in addition to first image data and the second image data.
15. The image sensor of claim 10 , wherein the unit pixels provide:
a first subgroup that adjusts capacitance of the first floating diffusion region to have the first value, and
a second subgroup that adjusts capacitance of the second floating diffusion region to have the second value.
16. The image sensor of claim 15 , wherein the first subgroup and the second subgroup have different sensitivity levels.
17. The image sensor of claim 10 , wherein the control logic is further configured to:
generate a difference between the reset average value and the pixel average value as an analog signal,
compare the analog signal with a ramp voltage to generate a comparison result,
convert the comparison result into a digital signal,
provide the digital signal as image data, and
generate the image using the image data.
18. The image sensor of claim 10 , wherein:
the control logic is further configured to:
obtain capacitance having a third value from the second floating diffusion region at a third time following the second time,
detect a third reset voltage and a third pixel voltage from the second floating diffusion region,
take an average of the first reset voltage, the second reset voltage, and the third reset voltage to calculate a reset average value, and
take an average of the first pixel voltage, the second pixel voltage, and the third pixel voltage to calculate a pixel average value, and
the third pixel voltage corresponds to capacitance having a third value of the second floating diffusion region.