New lensless camera design improves image focus for both foreground and background

Researchers at Osaka University have recently published a study in IEEE Transactions on Computational Imaging, unveiling an innovative approach to achieving sharp images without the need for traditional camera lenses. Instead, they rely on a specialized mask placed in front of the image sensor to capture clear images, with a particular focus on extending the depth of field.

The traditional limitation of camera design has been the size, shape, and distance of the lens required to focus light onto the image sensor. However, lensless cameras take a different approach. They capture initially blurry images and use reconstruction software to “focus” the image post-capture. This is possible because the necessary image information is encoded in the interaction between light and the mask in front of the sensor, known as the point spread function.

One of the key advantages of lensless cameras is the flexibility to alter their characteristics by modifying the mask intentionally. In this study, the researchers aimed to enhance the camera’s depth of field, enabling it to focus on objects both in the foreground and background simultaneously. In conventional lensless cameras, the point spread function changes depending on the subject’s distance, limiting the camera’s ability to capture subjects at varying distances in a single reconstruction process.

The Osaka University research team sought to develop a lensless camera with an extended depth of field, and they achieved this by designing a mask with sections radiating from the center, resembling the rays of a starburst. They discovered that the number and thickness of these sections played a crucial role in shaping the camera’s characteristics. More and thinner sections emphasized fine details, while fewer and thicker sections focused on smoother regions. Through an optimization process, the researchers identified the ideal combination of thin and thicker sections to achieve the best results.

The effectiveness of these masks was confirmed through simulations and the creation of a physical prototype, demonstrating an extended depth of field. Lensless cameras offer advantages in terms of their compact size, slim profile, and reduced weight compared to traditional cameras. Extending the depth of field is a significant step forward in making lensless cameras applicable in fields like medicine and industrial inspection. Additionally, there is room for further exploration of various mask types and arrangements, which could pave the way for lensless cameras to become common and practical devices in the future.

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