Image sensing device using a single analog to digital conversion operation on pixel signals and operating method thereof

Patent metadata

Field	Value
Publication number	US-12166949-B2
Application number	US-202117535927-A
Country	US
Kind code	B2
Filing date	Nov 26, 2021
Priority date	Apr 13, 2021
Publication date	Dec 10, 2024
Grant date	Dec 10, 2024

Abstract

An image sensing device includes a first sampling circuit suitable for sampling a reference ramp signal as a ramp signal; a switching circuit suitable for sequentially outputting first and second pixel signals to a common node based on first and second control signals; a second sampling circuit suitable for sampling the first and second pixel signals, which are sequentially outputted through the common node, as a measurement signal; a comparison circuit suitable for comparing the ramp signal with the measurement signal and generating a comparison signal corresponding to a comparison result; and a count circuit suitable for generating a count signal, which corresponds to a voltage level of the measurement signal, based on the comparison signal and a clock signal.

First claim

What is claimed is:

1. An image sensing device comprising:
a pair of pixels suitable for generating first and second pixel signals; and
a signal converter suitable for generating a depth information signal, which corresponds to a voltage level difference between the first and second pixel signals, through a single analog to digital conversion operation, wherein the single analog to digital conversion operation compares at least one reference ramp signal with a signal which corresponds to the voltage level difference between the first and second pixel signals.

2. The image sensing device of claim 1 , wherein the signal converter comprises:
a first sampling circuit suitable for sampling a reference ramp signal as a ramp signal;
a switching circuit suitable for sequentially outputting the first and second pixel signals to a common node based on first and second control signals;
a second sampling circuit suitable for sampling the first and second pixel signals, which are sequentially outputted through the common node, as a measurement signal;
a comparison circuit suitable for comparing the ramp signal with the measurement signal and generating a comparison signal corresponding to a comparison result; and
a count circuit suitable for generating a count signal, which corresponds to a voltage level of the measurement signal, as the depth information signal based on the comparison signal and a clock signal.

3. The image sensing device of claim 2 , wherein the measurement signal has a voltage level corresponding to the voltage level difference between the first and second pixel signals.

4. The image sensing device of claim 2 , wherein the switching circuit comprises:
a first switching element suitable for outputting any one of the first and second pixel signals to the common node during an auto-zeroing period of a single rolling readout period, based on the first control signal; and
a second switching element suitable for outputting the other one of the first and second pixel signals to the common node during a conversion period of the single rolling readout period, based on the second control signal.

5. The image sensing device of claim 2 , wherein the comparison circuit comprises:
a non-inverting input terminal suitable for receiving the ramp signal;
an inverting input terminal suitable for receiving the measurement signal; and
an output terminal suitable for outputting the comparison signal.

6. The image sensing device of claim 1 , wherein the signal converter comprises:
a first sampling circuit suitable for sampling a first reference ramp signal as a first ramp signal;
a second sampling circuit suitable for sampling a second reference ramp signal as a second ramp signal;
a first switching circuit suitable for outputting the first and second pixel signals to a first common node according to a first order based on first and second control signals;
a third sampling circuit suitable for sampling the first and second pixel signals, which are outputted through the first common node, as a first measurement signal;
a second switching circuit suitable for outputting the first and second pixel signals to a second common node according to a second order, which is opposite to the first order, based on third and fourth control signals;
a fourth sampling circuit suitable for sampling the first and second pixel signals, which are outputted through the second common node, as a second measurement signal;
a comparison circuit suitable for simultaneously comparing the first and second ramp signals with the first and second measurement signals and generating a comparison signal corresponding to the comparison result; and
a count circuit suitable for generating, as the depth information signal, a count signal corresponding to a voltage level of the first measurement signal and a voltage level of the second measurement signal based on the comparison signal and a clock signal.

7. The image sensing device of claim 6 ,
wherein the first measurement signal has a first voltage level obtained by subtracting a voltage level of the first pixel signal from a voltage level of the second pixel signal, and
wherein the second measurement signal has a second voltage level obtained by subtracting the voltage level of the second pixel signal from the voltage level of the first pixel signal.

8. The image sensing device of claim 6 ,
wherein the first switching circuit comprises:
a first switching element suitable for outputting any one of the first and second pixel signals to the first common node during an auto-zeroing period of a single rolling readout period, based on the first control signal; and
a second switching element suitable for outputting the other one of the first and second pixel signals to the first common node during a conversion period of the single rolling readout period, based on the second control signal, and
wherein the second switching circuit comprises:
a third switching element suitable for outputting the other one of the first and second pixel signals to the second common node during the auto-zeroing period of the single rolling readout period, based on the third control signal; and
a fourth switching element suitable for outputting the any one of the first and second pixel signals to the second common node during the conversion period of the single rolling readout period, based on the fourth control signal.

9. The image sensing device of claim 6 , wherein the comparison circuit comprises:
a first non-inverting input terminal suitable for receiving the first ramp signal;
a first inverting input terminal suitable for receiving the first measurement signal;
a second non-inverting input terminal suitable for receiving the second measurement signal;
a second inverting input terminal suitable for receiving the second ramp signal; and
an output terminal suitable for outputting the comparison signal.

10. The image sensing device of claim 6 , wherein the first and second ramp signals ramp in opposite directions within the same ramping range.

11. The image sensing device of claim 1 , wherein the single analog to digital conversion operation includes a single comparison operation.

12. An operating method of an image sensing device, the operating method comprising:
sampling a reference ramp signal as a ramp signal;
sequentially sampling, as a measurement signal, a pair of pixel signals indicating a depth from a subject;
generating, based on the ramp signal and the measurement signal, a comparison signal corresponding to a voltage difference between the pair; and
generating a depth information signal based on the comparison signal.

Assignees

• Sk Hynix Inc

Inventors

• Song Jeong Eun
• Kwon Oh Jun
• Park Yu Jin
• Seo Sung Uk
• Shin Min Seok
• Lee Sun Young

Classifications

• H04N25/78

  Readout circuits for addressed sensors, e.g. output amplifiers or A/D converters · CPC title

• H04N25/40

  Extracting pixel data from image sensors by controlling scanning circuits, e.g. by modifying the number of pixels sampled or to be sampled · CPC title

• H04N25/616

  involving a correlated sampling function, e.g. correlated double sampling [CDS] or triple sampling · CPC title

• H04N25/581

  acquired simultaneously · CPC title

• H04N13/218

  using spatial multiplexing · CPC title