Smart eye concept

Scientists studied the human eye to inspire their design for an artificial eye sensor. (goffkein.pro/Shutterstock)

In a nutshell

  • Researchers in Japan have developed a self-powered artificial eye that mimics human vision by using solar cells to distinguish colors with high precision, down to 10 nanometers of wavelength difference.
  • The device can perform logic operations and recognize motion and color with up to 82% accuracy, thanks to its unique ability to produce both positive and negative electrical responses based on light input.
  • Because it requires no external power and filters information like a biological retina, this technology could lead to ultra-efficient machine vision systems for use in autonomous vehicles, wearable health monitors, and remote sensors.

TOKYO — Every second, your eyes process an enormous flood of visual information, yet your brain never crashes or overheats. Japanese researchers took inspiration from our eyes, creating an artificial retina that could give today’s power-hungry machine vision systems a major upgrade.

How the Artificial Eye Mimics Human Vision

The innovation, published in Scientific Reports, centers on what scientists call an “optoelectronic artificial synapse.” This is essentially a synthetic brain cell that responds to light. Just as your eye sends different electrical signals to your brain when you see red versus blue, this device generates positive or negative electrical responses depending on the wavelength of light it encounters.

Today’s machine vision systems capture and store every detail at 10 to 60 frames per second, which demands enormous computational resources. Your eyes, by contrast, are remarkably selective. They filter and compress information before sending it to your brain, making human vision incredibly energy-efficient. The researchers say modern systems struggle to work well in small, low-power devices because they need too much data and storage to function.

The research team from the Tokyo University of Science tackled this challenge by creating a device that combines two dye-sensitized solar cells. These act like tiny solar panels that have been modified to respond differently to various colors of light. One cell is designed to respond strongly to blue light, while the other prefers red. When light hits the device, it generates either a positive voltage for blue wavelengths or a negative voltage for red ones.

Woman's eye toned in rainbow colors
Your eye sends different electrical signals to your brain when it sees different colors. (New Africa/Shutterstock)

This bipolar response, the ability to produce both positive and negative signals, is what makes the device so powerful. Traditional photodetectors can only produce positive signals, limiting their ability to distinguish between different types of input. But this new system can tell the difference between wavelengths as close as 10 nanometers apart, giving it color discrimination abilities that rival human vision.

To test their creation, the researchers demonstrated that the device could perform basic logic operations, the building blocks of all computing. Unlike conventional devices that struggle with complex operations, this artificial eye handled these functions with ease, thanks to its ability to switch between positive and negative responses based on light color and intensity.

But the real test came when they used the device for what’s called “physical reservoir computing,” a brain-inspired approach to machine learning where the physical properties of a material do the heavy lifting instead of traditional computer processors. The team flashed sequences of colored light at the device, each representing a different code. It was able to tell apart patterns up to six digits long, meaning it could recognize 64 different combinations. That’s impressive for such a simple setup.

The researchers tested the device’s ability to recognize human motion in different colors. They recorded videos of six different actions—bending, waving with one hand, waving with both hands, jumping, running, and moving sideways—and converted them into sequences of red, green, and blue light pulses. The artificial eye achieved 82% accuracy in identifying both the motion and the color, a performance that approaches what you might expect from much more complex systems.

How Is It So Efficient?

The device is based on solar cell technology, meaning it generates its own electricity from the light it’s detecting. This eliminates the need for external power sources and could enable a new generation of autonomous sensors that can operate indefinitely in natural lighting conditions.

While conventional machine vision systems require constant power to process and store massive amounts of visual data, this bio-inspired design filters out extra information right in the hardware, so it doesn’t need nearly as much computing power to work.

Solar artificial eye
The top half of this image depicts the proposed artificial synapse made using dye-sensitized solar cells. The plot shows the bipolar voltage response of the synapse depending on the wavelength of light used, which mimics how our eyes perceive the world and enables logic operations. The bottom half of the image shows an experiment in which the proposed system was used to capture and classify various human movements. (CREDIT: Associate Professor Takashi Ikuno from Tokyo University of Science)

Scientists envision applications ranging from compact surveillance systems to medical devices that monitor vital signs using multiple wavelengths of light. The technology could be particularly valuable for “edge computing” applications, situations where devices need to operate independently without connection to powerful central computers. Potential examples could include security cameras in remote locations, environmental sensors in forests, or health monitors that patients wear continuously.

The researchers do mention that these possibilities would require more sophisticated signal processing to handle complex visual scenes. However, they believe these challenges can be addressed by optimizing the dye materials and device architecture.

Every device around us is constantly growing hungrier for power and processing. While we’re still years away from artificial eyes that fully match human vision, but this work takes a step toward artificial vision systems that combine the efficiency of biological sight with the precision of electronic devices.

Paper Summary

Methodology

The researchers created their device by combining two dye-sensitized solar cells, each sensitized with different light-absorbing dyes (SQ2 and D131). One cell responds primarily to blue light while the other responds to red light. The device measures the voltage difference between the two cells when exposed to light of different wavelengths. They tested the device’s responses to monochromatic light pulses ranging from 300 to 750 nanometers, measured its synaptic properties using paired-pulse experiments, and evaluated its classification capabilities using sequences of red and blue light pulses representing different bit patterns. For motion recognition tests, they recorded videos of six human actions, converted them to binary format, colorized them in red, green, and blue, and fed the resulting light sequences to the device.

Results

The device successfully demonstrated wavelength-dependent bipolar responses, producing positive voltages for blue light and negative voltages for red light, with a wavelength discrimination resolution of approximately 10 nanometers. It exhibited synaptic behavior with paired-pulse facilitation indices ranging from -3,776 to 8,075, far exceeding the range of conventional artificial synapses. The device successfully performed AND, OR, and XOR logic operations and classified input patterns up to six bits in length (64 distinct states). In motion recognition tasks involving three colors and six types of human movement, the device achieved 82% overall accuracy with 100% color classification accuracy.

Limitations

The device’s performance depends on light intensity, which could affect wavelength discrimination under varying illumination conditions. The motion recognition accuracy (82%) was slightly lower than previous single-cell devices, attributed to lower readout voltages in the current design. The study used relatively simple motion patterns and controlled laboratory conditions, and real-world applications would require more sophisticated signal processing to handle complex visual scenes. The researchers also note that practical implementation would require additional circuitry to convert the analog outputs into clear digital logic levels.

Funding and Disclosures

This work was partially supported by the JST (Japan Science and Technology Agency) and the establishment of university fellowships for the creation of science and technology innovation (Grant Number JPMJFS2144), with additional support from JST SPRING (Grant Number JPMJSP2151). The authors declare no competing interests or conflicts of interest.

Publication Information

This research was published in Scientific Reports (volume 15, article number 16488) in 2025. The paper is titled “Polarity-tunable dye-sensitized optoelectronic artificial synapses for physical reservoir computing-based machine vision” and is authored by Hiroaki Komatsu, Norika Hosoda, and Takashi Ikuno from the Department of Applied Electronics, Graduate School of Advanced Engineering, Tokyo University of Science.

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