Not Limited by Wavelength, OmniVision Shrinks Down to “World’s Smallest” Pixel

One of the major value propositions of each new smartphone generation today is its imaging technologies. Year after year, new phones offer better and better cameras, and this trend has placed an enormous demand for improvement in the underlying imaging hardware, specifically image sensors.

 

An overview of OmniVision's latest image sensor. Image used courtesy of OmniVision

 

This week, OmniVision made headlines when it announced the release of its newest 200 MP image sensor, which it claims incorporates the world’s smallest pixel size. In this article, we’ll discuss some tradeoffs associated with pixel size and the new sensor from OmniVision.

 

Pixel Size Tradeoffs

We tend to believe that smaller is better when we think about pixel size. However, this is not always the case, as several significant performance tradeoffs relate directly to the pixel size in a CMOS image sensor.

To start with the benefits of reducing pixel size, with a fixed-size CMOS imaging sensor, reducing pixel size is the only way to increase spatial resolution. This method is the only one because smaller individual pixels mean that we can fit more pixels into the same area for the same size die. The result is a higher spatial sampling, resulting in captured images with higher granularity and greater detail than otherwise possible.

 

Pixel well capacity versus size. Image used courtesy of Princeton Instruments

 

On the other hand, reducing pixel size is also shown to impact each pixel's performance negatively. 

The biggest impact of a decreased pixel size is that it also results in a reduced well capacity, which is the amount of light a pixel can hold before becoming saturated. This reduction is because smaller pixels have fewer photons incident at their aperture and saturate at lower photometric exposure values. 

With a reduced well capacity, we also experience a decreased dynamic range (i.e., the ability of a sensor to image highlights and shadows), a lower signal-to-noise ratio (i.e., less clear images), and less light sensitivity. 

With all that in mind, many believe there is an optimal pixel size for a given application, where designers can balance tradeoffs between spatial resolution and well capacity.

 

A New "World's Smallest" Image Sensor from OmniVision

This week, OmniVision made headlines when it announced the release of its newest image sensor, the OVB0A.

 

Functional block diagram of the OVB0AH0. Screenshot used courtesy of OmniVision

 

The OVB0A is a 200 MP image sensor designed for rear-facing cameras in high-end smartphones. The company is one of the world's smallest 200 MP image sensors thanks to its use of a 0.56 μm pixel size, which it claims is the world's smallest. 

OmniVision claims that it was able to leverage its PureCel Plus‑S stacked die technology to balance the tradeoffs between pixel size and performance in the OVB0A.

Altogether, the image sensor offers:

• An image area of 9210.88 μm x 6917.12 μm
• A 200 MP resolution
• An optical format of 1/1.395”
• A frame rate up to 120 fps at 12.5 MP resolution 

The device also features functionality such as:

• 16-cell binning
• 8K video
• 2x crop zoom
• 100% quad phase detection for autofocus improvements

 

Featured image [modified] used courtesy of OmniVision

 

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