Image pickup elements, light detection elements, and electronic devices
By acquiring multiple images under different camera conditions and setting a randomly changing threshold on the input side of the analog-to-digital converter, the problem of pseudo-images in dynamic range expansion is solved, achieving high-quality images while reducing circuit size and power consumption.
Patent Information
- Application Number
- CN202080072433.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Priority Date
- 2019-11-13
- Filing Date
- 2020-10-19
- Publication Date
- 2025-09-16
- Estimated Expiration
- 2040-10-19
AI Technical Summary
In the prior art, pseudo images are generated due to the periodicity of random numbers in dynamic range expansion, resulting in degradation of image quality and increases in circuit scale and power consumption.
A single-slope analog-to-digital converter is used to acquire multiple images under different camera conditions. A randomly changing threshold is set on the input side of the analog-to-digital converter, and a comparison unit and a selection unit are used to select the appropriate digital pixel signal to avoid periodic effects.
Effectively prevent the generation of pseudo images, reduce circuit scale and power consumption, and improve image quality.
Smart Images
Figure CN114600447B_ABST
Abstract
Claims
1. An imaging element, comprising: an analog-to-digital converter configured to convert a plurality of analog pixel signals acquired under a plurality of imaging conditions different from one another and output from the pixels into a plurality of digital pixel signals; a threshold setting unit configured to set a randomly varying threshold on an input side of the analog-to-digital converter; a comparing unit configured to use the threshold value set by the threshold value setting unit as a comparison threshold value and compare the comparison threshold value with one of the plurality of analog pixel signals; as well as A selection unit is configured to select and output one of the plurality of digital pixel signals output from the analog-to-digital converter based on a comparison result from the comparison unit.
2. The imaging element according to claim 1, wherein The analog-to-digital converter includes a single-slope type analog-to-digital converter configured to perform analog-to-digital conversion by using a ramp waveform reference signal having a voltage value varying with time.
3. The imaging element according to claim 2, wherein The single-slope analog-to-digital converter comprises: a comparator configured to compare the plurality of analog pixel signals output from the pixels with the ramp waveform reference signal, and A counter is configured to measure a time period from a start time when the comparator starts a comparison operation to an end time when the comparator ends the comparison operation.
4. The imaging element according to claim 3, wherein The threshold setting unit sets the randomly varying threshold by controlling an auto-zero period during which an input terminal and an output terminal of the comparator are short-circuited.
5. The imaging element according to claim 3, wherein The threshold setting unit sets the randomly varying threshold by controlling a bias current in the comparator. The imaging element according to claim 3 , wherein: The threshold setting unit sets the randomly varying threshold by changing a size ratio of a channel width to a channel length of a differential pair transistor included in the comparator.
7. The imaging element according to claim 1, wherein The imaging element sequentially images the same object using a single pixel while changing imaging conditions to obtain a plurality of the analog pixel signals, or simultaneously images the same object using a plurality of pixels with different imaging conditions to obtain a plurality of the analog pixel signals.
8. The imaging element according to claim 7, wherein The imaging conditions include the exposure amount, exposure time, and charge-to-voltage conversion efficiency or sensitivity of the pixel.
9. The imaging element according to claim 8, wherein When the plurality of imaging conditions include high conversion efficiency and low conversion efficiency, and When the pixel sequentially outputs a P-phase signal at a reset level when the floating diffusion (FD) is reset and a D-phase signal at a signal level based on photoelectric conversion performed by the light receiving element, The single-slope analog-to-digital converter acquires a count value of the P-phase signal with low conversion efficiency from a counter to temporarily hold the count value, and returns the count value to the counter before counting the D-phase signal with low conversion efficiency.
10. The imaging element according to claim 9, wherein The single-slope analog-to-digital converter includes two sets of comparators and counters arranged in parallel in each pixel column. The imaging element according to claim 10 , wherein: The single-slope ADC includes an adaptive attenuation ADC configured to attenuate the amplitude of each analog pixel signal output from the pixel by a predetermined amount to compress a dynamic range when the amplitude of the analog pixel signal is relatively large.
12. The imaging element according to claim 11, wherein The adaptive attenuation type analog-to-digital converter includes a sample-and-hold circuit on an input side of the comparator, the sample-and-hold circuit being configured to sample and hold the P-phase signal having low conversion efficiency.
13. The imaging element according to claim 1, wherein When the imaging conditions include an analog gain of the analog-to-digital converter, a single analog-to-digital converter sequentially performs analog-to-digital conversion while changing the analog gain, or a plurality of the analog-to-digital converters having different analog gains simultaneously perform analog-to-digital conversion.
14. The imaging element according to claim 13, wherein When the plurality of imaging conditions include a high analog gain and a low analog gain, and When the pixel sequentially outputs a P-phase signal at a reset level when the floating diffusion (FD) is reset and a D-phase signal at a signal level based on photoelectric conversion performed by the light receiving element, The single-slope analog-to-digital converter acquires a count value of the P-phase signal with a low analog gain from a counter to temporarily hold the count value, and returns the count value to the counter before counting the D-phase signal with a low analog gain.
15. The imaging element according to claim 14, wherein The single-slope analog-to-digital converter includes two sets of comparators and counters arranged in parallel in each pixel column.
16. The imaging element according to claim 1, wherein When the pixel sequentially outputs a P-phase signal at a reset level when the floating diffusion (FD) is reset and a D-phase signal at a signal level based on photoelectric conversion performed by a light receiving element, the threshold setting unit sets the threshold of the random change by using the potential change of the P-phase signal and the D-phase signal of each of the pixels.
17. The imaging element according to claim 16, wherein When the plurality of imaging conditions include high conversion efficiency and low conversion efficiency, the single slope type analog-to-digital converter includes an analog-to-digital converter for high conversion efficiency and an analog-to-digital converter for low conversion efficiency, and The high conversion efficiency analog-to-digital converter and the low conversion efficiency analog-to-digital converter each include: D phase count value latch, a comparison unit for determining the output level of the latch, and A selector is configured to select an output of the high-conversion-efficiency analog-to-digital converter or an output of the low-conversion-efficiency analog-to-digital converter based on a comparison result from the comparison unit.
18. The imaging element according to claim 16, wherein When the plurality of imaging conditions include a high analog gain and a low analog gain, the single slope type analog-to-digital converter includes an analog-to-digital converter for high analog gain and an analog-to-digital converter for low analog gain, and The high analog gain analog-to-digital converter and the low analog gain analog-to-digital converter respectively include: D phase count value latch, a comparison unit for determining the output level of the latch, and A selector is configured to select an output of the high analog gain analog-to-digital converter or an output of the low analog gain analog-to-digital converter based on a comparison result from the comparison unit. 19 . A light detection element comprising the imaging element according to claim 1 .
20. An electronic device comprising the imaging element according to any one of claims 1 to 18.
Citation Information
Patent Citations
Image pickup device
JP1992172086A
Image pickup apparatus
CN101719972A
Solid-state imaging device and camera system
CN102209209A