Infrared imaging has long been reserved for expensive, bulky equipment limited to specific military or industrial uses. However, its ability to detect heat, through smoke, at night or in opaque environments, represents a crucial issue for sectors such as security, medicine or autonomous mobility. A technological obstacle persisted: how to make this technology accessible, compact and functional at room temperature.
Researchers from the Beijing Institute of Technology, in collaboration with the Light Publishing Center of the Changchun Institute of Optics, propose a radical solution. Taking inspiration from the sensory anatomy of snakes, they designed a system capable of converting infrared into visible images in 4K resolution, without cooling. Their results, published in Light: Science & Applications, could push infrared into general public uses.
The biological model of the snake to capture the invisible
In certain species of snakes, night hunting relies on an additional sense: infrared detection. This system relies on thermosensitive structures located between the eyes and nostrils, capable of detecting infrared radiation emitted by an animal's body heat. Operating passively, without emitting a signal, these organs form a “thermal image” in response to temperature differences in the immediate environment.
This capacity arises from the membrane suspended in a hollow cavity which reacts to thermal variations. When an infrared wave hits this membrane, certain areas heat up slightly. They generate a nerve signal transmitted to the brain. The thermal information is then combined with classical vision to create a bimodal representation of the scene.
The team of researchers was inspired by this mechanism to design an artificial system capable of capturing infrared without current constraints. The objective was clear: to convert this biological ability into a miniaturizable technological solution, efficient and compatible with the materials already present in image sensors.
This biomimicry is not limited to function. It also influences the organization of the sensor layers. Where the biological membrane acts as a thermal transducer, the artificial sensor relies on semiconductor materials capable of converting infrared energy into an electrical signal, then light. This analogy guided the entire architecture of the designed system.
A miniature technology to transform heat into a visible image
To allow a camera to “see heat” without needing to be cooled, researchers designed an ultrathin structure made of nanometric materials. The central element of this sensor is based on quantum dots based on mercury telluride (HgTe). These tiny particles can detect infrared up to 4.5 microns in wavelength. Their size can be adjusted, which changes their sensitivity as needed.
But capturing infrared wasn't the hardest part. The real challenge lay in the parasitic noise generated by the heat of the sensor itself. These unwanted signals, called dark currents, can distort images. To block them, the researchers added an insulating barrier between the quantum dots and the rest of the circuit. This barrier, made of zinc oxide and a special polymer (P3HT), prevents false signals from passing through. But it lets the real ones circulate, those produced by infrared light.
© Ge Mu and Xin Tang
a) System inspired by snakes, compared to classic artificial vision. b) Superposition of optical layers on the CMOS sensor. c) The system sees through chemical vials and a silicon wafer, invisible in normal light. d) View of light sources through a silicon wafer.
Another ingenious idea: instead of letting the sensor produce a simple electric current, the researchers added a luminous layer just above it. It transforms the electrical signal into visible light using phosphorescent materials. In particular an iridium-based compound. Result: the sensor produces a stable green light, easy to read by a conventional camera. With this combination, the system achieves a photon-to-photon conversion efficiency of more than 6% in the near infrared, without requiring cooling.
A 4K image in infrared without cooling
The system uses a standard CMOS sensor. This 4K infrared sensor (3840 × 2160 pixels) constitutes a first in the field of high-resolution infrared imaging. Until then, it depended solely on cooled sensors and very expensive components, therefore inaccessible to the general public.
Tests of the sensor show that it can produce sharp and precise images, even when infrared light is very weak. In short, he manages to “see” the invisible with great finesse. The sensor remains efficient in both the near infrared (SWIR) and the mid infrared (MWIR). It generates a sufficiently bright image in these two ranges: approximately 6388 candelas per square meter for SWIR, and 1311 cd/m² for MWIR. For information: the candela measures light intensity in the International System of Units (SI), 1 candle is worth 1 candela. These figures reflect the sensor's ability to provide a clear image, even in difficult conditions.
Another important point: the quality of the image remains stable even if the quantity of light varies greatly. This is what we call good dynamics. Here, the sensor achieves a dynamic ratio of 38 decibels for SWIR, and 33 decibels for MWIR. This means it can capture both very dark and very bright areas of a scene, without saturation or loss of information.
Finally, the system remains sensitive to extremely low light levels, comparable to those found in space. It can detect signals as weak as 10⁻¹⁰ watts per square centimeter. This corresponds to the light intensity of the stars. This sensitivity makes the sensor equally effective in total darkness or in environments invisible to the naked eye.
Concrete applications and general public potential
One of the major contributions of this technology is the broadening of the spectrum visible by conventional sensors. It goes from 0.4–0.7 µm to 0.4–4.5 µm. This means that devices incorporating this system can operate in conditions where visible light fails. Namely: fog, smoke, total darkness, or highly reflective environments. The infrared spectrum becomes accessible without logistical constraints.
Immediate industrial uses include non-destructive inspection, thermal fault detection, or monitoring of hazardous environments. In agriculture, this allows plant health to be analyzed by detecting subtle heat signatures. In food safety, variations in temperature or humidity in packaging can be detected visually.
In the automotive sector, this infrared vision would allow autonomous vehicles to distinguish pedestrians or obstacles in conditions of zero visibility. For medicine, miniature cameras could detect inflammation or abnormal circulation in real time.
In the longer term, the low manufacturing cost announced by the authors opens the way to integration into smartphones, portable cameras, or home automation devices. Unlike current infrared modules (often limited to blurred images or simplified thermograms), this system would allow a high definition thermal image, visible to the naked eye.
The researchers specify that mass manufacturing is possible using existing processes, without specific infrastructure. This industrial compatibility, combined with performances previously reserved for cryogenic systems, makes this technology a real bridge between biomimicry and mass innovation.
Source: Mu, G., Lin, Y., Fu, K. et al. “Infrared visualized snakes-inspired artificial vision systems with CMOS sensors-integrated upconverters”. Light Sci Appl 14282 (2025).
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