Image sensing device for generating HDR image and imaging device including the same

An imaging device comprising:

• an image sensing device configured to generate image data based on each of a reference signal corresponding to a sensing node that is reset and an image signal corresponding to the sensing node in which photocharges are accumulated, in each of a high conversion gain (HCG) mode in which the sensing node has a first capacitance and a low conversion gain (LCG) mode in which the sensing node has a second capacitance greater than the first capacitance;
• and
• an image signal processor configured to generate a high dynamic range (HDR) image using image data generated in the HCG mode and image data generated in the LCG mode,
• wherein the image sensing device comprises:
• an analog-to-digital converter (ADC) configured to sequentially perform analog-to-digital conversion of the reference signal of the HCG mode, the image signal of the HCG mode, the image signal of the LCG mode, and the reference signal of the LCG mode;
• and
• a ramp generator configured to generate a first ramp signal having a negative slope, the first ramp signal being used for analog-to-digital conversion in the HCG mode and to generate a second ramp signal having a positive slope, the second ramp signal being used for analog-to-digital conversion in the LCG mode while having a waveform different from that of the first ramp signal,
• wherein the ADC comprises a comparator that has a non-inverting terminal for receiving the first ramp signal and the second ramp signal in each of the HCG mode and the LCG mode and an inverting terminal for receiving the pixel signal in each of the HCG mode and the LCG mode;
• and
• wherein the image signal processor subtracts a reference value obtained by conversion of the reference signal of the LCG mode from a sum of a signal value obtained by conversion of the image signal of the LCG mode and a margin value, and acquires image data corresponding to a voltage difference between the image signal and the reference signal in the LCG mode.

An image sensing device comprising:

• a pixel configured to output a reference signal corresponding to a sensing node that is reset and an image signal corresponding to the sensing node in which photocharges are accumulated, in each of a high conversion gain (HCG) mode in which the sensing node has a first capacitance and a low conversion gain (LCG) mode in which the sensing node has a second capacitance greater than the first capacitance;
• an analog-to-digital converter (ADC) configured to sequentially perform analog-to-digital conversion of the reference signal of the HCG mode, the image signal of the HCG mode, the image signal of the LCG mode, and the reference signal of the LCG mode;
• and
• a ramp generator configured to generate a first ramp signal that is used for analog-to-digital conversion in the HCG mode, and to generate a second ramp signal that is used for analog-to-digital conversion in the LCG mode,
• wherein each of the first ramp signal and the second ramp signal has a negative slope;
• and
• wherein a voltage level at which the second ramp signal starts to fall for readout of the image signal of the LCG mode is lower by a signal offset than a voltage level at which the second ramp signal starts to fall for readout of the reference signal of the LCG mode.