Curved Sensor for Improved Camera Quality

Before the era of digital cameras, the incorporation of a certain type of film was responsible for producing photos once they were taken. Today, image sensors have replaced the need for such camera films, as they capture and convert light to produce an image that can subsequently be seen through a viewfinder or LCD monitor once the photo has been taken.

With sensor variations that are responsible for determining the size of the produced image, its resolution, depth of field, dynamic range, and even the overall size of the camera and its lenses, image sensors play a key role in determining the quality of your image¹.

To further advance camera image sensors to produce increasingly sharp and clear pictures, a team of researchers from Microsoft Research, in collaboration with researchers from HRL Laboratories LLC, have looked at how to manufacture curved sensors to do just that.

Most digital cameras are incorporated with flat panel complementary metal-oxide semiconductor (CMOS) sensors, which are located behind the lens of the camera, are must manipulate the captured image to be detected by the specific shape of the sensor.

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Due to the flat nature of these sensors, cameras are often limited in their ability to capture the full amount of light that is present within a given field of view, thereby also limiting the resolution and clarity of the image.

While such cameras are incorporated with certain optical elements that reduce the production of such aberrations that can be produced by such the need to manipulate the image to accommodate the flat sensor, the development of a curved lens could hold a promising future for eliminating the need of adding such optical components.

This concept of developing of a curved sensor for imaging purposes has been introduced in the past, however, the physical manipulation of such sensors has not been successful until now². Previously, researchers have attempted to push the center of a flat image sensor while the ends were glued down, however, in this method, sensors often shattered before they could reach their desired curvature.

In their newly developed pneumatic bending process, the Microsoft research team a method to bend average camera imaging sensors without altering any of its electrical or imaging characteristics.

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Through the use of their forming-mold design, the researchers placed a thin CMOS image-sensor wafer to the mold while simultaneously holding the edges of the sensor down without applying too much mechanical stress or constraints to the sensor.

By forming an unconstrained die through this pressurized membrane, the center of the die moves downward, as the edges move inward, thereby releasing radial tension without affecting the curving movement of the die to accommodate the exact shape of the mold.

This gradual contraction of the die allows for the sensor to smoothly conform to the spherical shape of the mold without introducing wrinkling instabilities to the sensor. In their comparison of the newly developed curved sensor through this method, with the same camera’s sensor remaining in its flattened shape, the Microsoft researchers found that the curved sensor was capable of producing images whose resolution almost doubled that of its flattened predecessor².

Furthermore, the curved image sensor lost almost no light in its produced image, which is a significant improvement as compared to traditional SLR cameras often experience a 90% reduction of light detection at its sensor edges.

By taking the sensor of an average camera and easily manipulating its shape to create such a dramatic improvement in its optical performance, the Microsoft and HRL Laboratories LLC research teams found that this process was also extremely cost effective².

The researchers are hopeful that their demonstration of the feasibility of producing such curved sensors could be possible on a much larger scale in order to mass produce curved sensors for imaging purposes. They are hopeful that the future of curved imaging sensors could be applied in mobile phones, infrared (IR) cameras for aeronautic purposes, and much more.

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Sources:

1. “Demystifying digital camera sensors once and for all” – TechHive
2. “Highly curved image sensors: a practical approach for improved optical performance” B. Guenter, N. Joshi, et al. Optical Society of America. (2017). DOI: 10.1364/OE.25.013010.
3. Shutterstock.com/Triff