Smartphone cameras are constantly evolving,wiht manufacturers striving to improve image quality and low-light performance. A key factor in camera performance is the size of the image sensor and lens; larger sensors capture more light and resolve finer details. However,conventional color filters,which are essential for creating color images,can block a notable portion of incoming light,reducing overall image brightness and clarity.

For decades, these filters have been arranged as grids of red, green, and blue elements over the image sensor’s pixels. But now, novel techniques are emerging to harness the physics of light, aiming to produce color images while minimizing light loss. These advancements were highlighted at the 2023 IEEE International Electron Device Meeting (IEDM), and are now transitioning from laboratory concepts to tangible technologies.

for example, Samsung will supply the front camera for Xiaomi’s upcoming phone, utilizing Samsung’s nano-prism technology to enhance low-light performance. This technology employs diffraction to gather more light in each color-specific pixel, boosting light sensitivity by 25 percent, according to the company. This approach complements rather than replaces traditional color filters.

In parallel,two startups,Eyeo and PxE Holographic Imaging,are pioneering filter-free color imaging solutions. Eyeo, an Imec spinoff, recently secured €15 million in seed funding. PxE Holographic Imaging showcased it’s technology, which integrates depth sensing and color imaging, at this year’s Consumer Electronics Show (CES).

Both PxE and Eyeo’s technologies are designed to be compatible with CMOS sensors, which are the predominant image sensors in modern cameras. According to pxe’s founder and CEO yoav Latzky, “The CMOS sensor is a very mature and strong platform to build upon. You have it in every device today,” adding that “everybody wants more photons reaching their CMOS sensors.”

Eyeo’s Innovative Approach to Filter-Free Color Capture

Eyeo is focused on commercializing research presented by Imec at IEDM 2023, targeting applications in consumer electronics, security, and other fields. By eliminating the color filter, Eyeo’s image sensor achieves three times the sensitivity of traditional CMOS sensors. Eyeo CEO See stated, “It’s as if we are finally opening the eyes of an image sensor.”

“It’s as if we are finally opening the eyes of an image sensor,”

The technology functions by directing light through vertical waveguides that separate light based on wavelength, guiding photons to the appropriate pixel. These waveguides act as funnels, enabling pixel sizes to be reduced to less than 0.5 micrometers in width, approximately half the size of a typical smartphone pixel. According to the Imec research, this technology also aligns more closely with the color sensitivity of the human eye compared to current filter-based imagers.

The color splitting technology is engineered to be manufactured using existing CMOS foundry tools and processes. Eyeo is currently focused on ensuring the sensor’s compatibility with potential customer systems, according to Hoet.

Hoet anticipates that the enhanced sensitivity and smaller size of Eyeo’s image sensors will be notably beneficial for smartphones.Though, he expects initial adoption in other sectors, such as security systems requiring low-light performance and augmented reality devices demanding ultra-compact sensors.

PxE’s 3D Integration with CMOS Technology

PxE’s underlying concept shares similarities with Eyeo’s approach. Both companies aim to replicate the function of color filters without sacrificing photons, ensuring that colors are accurately directed to the correct pixels through light manipulation, as Bertlatzky explains.