Sony announces a “new pixel structure for mobile image sensors”
This isn’t strictly related to Alpha gear but it’s nice t see Sony pushing boundaries on their mobile sensor tech:
2×2 On-Chip Lens Solution
A new pixel structure for mobile image sensors
The 2×2 On-Chip Lens (OCL) solution is a new image sensor technology for achieving high-speed focus, high-resolution, high-sensitivity, and high dynamic range.
In conventional technologies, the variance in sensitivity per pixel caused by the structure (described below), which places an on-chip lens that spans four pixels, was a major issue. However, we have successfully developed a high-performance image sensor with high image quality through optimization of the device structure and the development of a new signal processing technology.
Pixel structure
A condenser lens called an “on-chip lens” is placed on top of the image sensor pixels.
Conventional on-chip lenses were placed on each pixel. However, four adjacent pixels with the same color share one on-chip lens in 2×2 OCL.
The following benefits are realized as a result:
Phase differences can be detected across all pixels
Since conventional methods for detecting phase differences used dedicated pixels with no imaging functionality, only a small number of pixels could be used as detection pixels.
Due to the fact that the imaging pixels can be used as detection pixels in the 2×2 OCL method, phase differences can be detected across all pixels. As a result, the sensor can focus on even small objects with high accuracy.
Improved phase difference detection performance (focus performance)
Focus performance at low light intensity
To achieve stable focus performance at low light intensity, the information obtained from multiple phase difference detection pixels must be integrated and the impact of the noise eliminated.
As mentioned above, 2×2 OCL is able to detect phase differences across all pixels, which makes it possible to integrate more information and achieve a stable focus performance.
-
Conventional technology
-
2×2 OCL
Focus performance that does not depend on the object shape or pattern
Since conventional phase difference detection methods separated the pixels laterally for detection, they were not very good at detecting objects which lacked pattern change in the horizontal direction (ex: objects composed of edges in the horizontal direction).
However, 2×2 OCL is able to detect vertically in addition to horizontally, which enables high-speed auto focus using phase differences in every situation.
The figures below show the phase difference detection characteristics of objects with edges at various angles:
Color filter array with a Quad Bayer structure
Adopting a color filter array with a Quad Bayer structure that places four pixels with the same color next to each other addresses the needs of both high sensitivity and high resolution. In addition, it also supports High Dynamic Range (HDR) imaging.
High resolution
Array conversion through a unique signal processing function enables high resolution imaging.
High sensitivity
Bright images and videos with low noise can be captured by adding together the four adjacent pixels with the same color. Moreover, improved sensitivity is realized through the design and production technology of the 2×2 OCL which increases the efficiency of light utilization.
High Dynamic Range (HDR)
Real-time HDR output is possible through a unique exposure control technology and signal processing function.
