Sony announces the development of the world’s first stacked CMOS image sensor technology that improves dynamic range and reduces noise
Sony has announced what it claims is the world’s first vertically stacked CMOS image sensor design, which could potentially be a breakthrough in low-light imaging. According to Sony, the breakthrough was achieved by vertically stacking a layer of pixel transistors under a layer of photodiodes, which has benefits in the form of stronger pixel saturation signals, wider dynamic range and performance. improved imaging in low light. The hardware change is, according to the company, an entirely new design for CMOS (Complementary Metal Oxide Semiconductor) image sensor design.
In a typical stacked CMOS image sensor, photodiodes and pixel transistors are stacked next to each other – parallel and in one layer itself. A photodiode is the outermost layer of an image sensor, which captures light data entering through a camera lens and converts it into electrical signals. The pixel transistors then monitor the signals and decode them into color data on the sensor itself, before relaying that signal to the image sensor’s logic chip. The logic chip then outputs the data received from the pixel transistors, passing it through an image processor to ultimately produce the end result – the photograph.
By stacking photodiodes and pixel transistors in two layers, Sony has increased the area and volume of each layer, while optimizing each layer individually. According to Sony, this helped double the typical saturation signal level – or the volume of color and luminance data each pixel can process. In turn, this higher saturation signal from each pixel represents a much wider dynamic range than a sensor of a certain size can achieve today.
The separate transistor layer also means that the amplifier transistors, which are responsible for handling image signal noise, can also be increased in size as the stacked sensor provides a full layer for the pixel transistors. This, in turn, means image noise can be significantly reduced as the image signal is amplified more than before – according to Sony.
“The expanded dynamic range and noise reduction available through this new technology will prevent underexposure and overexposure in settings with a combination of bright and low lighting (e.g. backlit settings) and enable high quality and low noise even in low light conditions (e.g. indoor, nighttime settings),” Sony said in a statement.
Sony said its two-layer stacked CMOS sensor design will come to smartphone image sensors in the future, where it could play a huge role. Mobile image sensors are limited by their size, where vertical stacking can be essential.
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