CMOS image sensors convert light into electrical signals through photodiodes paired with pixel transistors, and three vendors' disclosures show how that base design has been extended: Sony Semiconductor Solutions' stacked architecture separates pixel and logic chips to roughly double saturation signal level, OmniVision's backside-illuminated OS04D10 raises sensitivity 40% while cutting power 40%, and Samsung Semiconductor's 0.7μm ISOCELL Slim GH1 uses pixel-merging to recover sensitivity equivalent to a 1.4μm sensor in low light.
How do CMOS pixels convert light into an electrical signal?
Within Sony Semiconductor Solutions' pixel chip design, photodiodes convert light into electrical signals while pixel transistors control those signals, with both components placed side by side on the same layerCITE:E1. This co-location of the light-sensing element and the signal-control element on a single layer is the baseline pixel structure that the backside-illuminated and stacked designs described below build on.
How do backside-illuminated (BSI) pixels improve sensor performance?
OmniVision's OS04D10 sensor, which uses a high-performance backside-illuminated pixel, delivers 40% higher sensitivity, more than 30% improvement in signal-to-noise ratio, and 40% lower power consumption compared with its predecessorCITE:E4. Because the light-sensing layer sits closer to the incoming light path in a BSI design, OmniVision reports all three gains — sensitivity, SNR, and power — moving together in the same generation-over-generation comparisonCITE:E4.
How does stacked CMOS architecture improve on conventional sensors' dynamic range and integration?
Sony Semiconductor Solutions' stacked CMOS architecture, announced December 16, 2021, stacks a pixel chip made of backside-illuminated pixels on top of a separate logic chip dedicated to signal-processing circuitsCITE:E2. By moving signal processing off the pixel chip and onto its own logic chip, this structure raises saturation signal level to roughly double that of conventional image sensors, which in turn widens dynamic rangeCITE:E3.
How do sensors maintain light sensitivity as pixel size shrinks to the limit?
Samsung Semiconductor's ISOCELL Slim GH1 became the industry's first mobile image sensor to adopt a 0.7μm pixel, the smallest pixel size in the industryCITE:E5. In low-light environments, the GH1 applies Tetrapixel pixel-merging technology to combine multiple pixels, reaching light sensitivity equivalent to a sensor built with 1.4μm pixelsCITE:E6.
The numbers side by side
| Metric | Value | Entity |
|---|
| Saturation signal level, stacked vs. conventional sensors | ~2x | Sony Semiconductor SolutionsCITE:E3 |
| OS04D10 sensitivity vs. predecessor | +40% | OmniVisionCITE:E4 |
| OS04D10 signal-to-noise ratio vs. predecessor | +30%+ | OmniVisionCITE:E4 |
| OS04D10 power consumption vs. predecessor | -40% | OmniVisionCITE:E4 |
| ISOCELL Slim GH1 pixel size | 0.7μm | Samsung SemiconductorCITE:E5 |
| GH1 low-light sensitivity, pixel-merged | equivalent to 1.4μm pixel | Samsung SemiconductorCITE:E6 |
What this means
Lined up together, these disclosures trace one continuous engineering path rather than three unrelated products. The base pixel keeps the photodiode and the pixel transistor on the same layerCITE:E1; moving to backside illumination is credited with a 40% sensitivity gain and a 40% power reductionCITE:E4; separating the pixel chip from a dedicated logic chip is credited with roughly doubling saturation signal levelCITE:E2CITE:E3; and shrinking the pixel to 0.7μm is paired with Tetrapixel merging to claw sensitivity back to a 1.4μm-equivalent levelCITE:E5CITE:E6. Each disclosed technique addresses a tradeoff introduced by the one before it — signal separation, then light capture, then dynamic range, then pixel density.
FAQ
How do CMOS pixels convert light into an electrical signal?
Within Sony Semiconductor Solutions' pixel chip design, photodiodes convert light into electrical signals while pixel transistors control those signals, with bo…
How do backside-illuminated (BSI) pixels improve sensor performance?
OmniVision's OS04D10 sensor, which uses a high-performance backside-illuminated pixel, delivers 40% higher sensitivity, more than 30% improvement in signal-to-n…
How does stacked CMOS architecture improve on conventional sensors' dynamic range and integration?
Sony Semiconductor Solutions' stacked CMOS architecture, announced December 16, 2021, stacks a pixel chip made of backside-illuminated pixels on top of a separa…
How do sensors maintain light sensitivity as pixel size shrinks to the limit?
Samsung Semiconductor's ISOCELL Slim GH1 became the industry's first mobile image sensor to adopt a 0.7μm pixel, the smallest pixel size in the industryCITE:E5.
Author's Take・EffectStory 編輯部
What stands out across these three disclosures is that pixel shrinkage and image-quality preservation are being solved by separate engineering levers rather than one technique doing double duty. Sony's fix for dynamic range is structural — moving signal processing onto a dedicated logic chip and stacking it under the pixel chip, which is what nearly doubles saturation signal level, not a smaller or bigger pixel. OmniVision's 40% sensitivity and power gains come from repositioning the light-sensing layer via backside illumination, a placement change rather than a pixel-count change. Samsung's 0.7μm pixel paired with Tetrapixel merging back to a 1.4μm-equivalent shows the same pattern at the density end: shrink first, then recover sensitivity computationally. The figure worth watching next is whether any vendor discloses saturation signal level or SNR at sub-0.7μm pixel pitches — that would show whether stacking and pixel-merging can compound rather than simply substitute for each other.