Cat-inspired camera enhances low-light vision for drones, camouflage detection

Scientists have created a new camera that mimics the structure of a cat’s eye to tackle difficulties posed by low light and camouflage. Designed by Min Su Kim and team, the camera enhances the abilities of those used in drones and autonomous vehicles.

It replicates two key features of feline eyes: vertical pupils and the tapetum lucidum, a reflective layer behind the retina that boosts light sensitivity.

“The combination of the silver metal reflector-inspired tapetum lucidum and the fully dilated pupil greatly enhances the camera’s sensitivity, enabling it to capture clearer and more detailed images even in challenging lighting conditions,” Minseok Kim tells Interesting Engineering (IE) .

Why feline vision is superior

While software solutions can address the issues of low light and camouflage, they come with high demands on processing power and battery life. Motivated by these drawbacks, Kim and colleagues turned to hardware innovations, drawing inspiration from the natural design of cats’ eyes.

“Mimicking the eye structures of cats enhances camera performance in low-light conditions by incorporating features such as the tapetum lucidum and a vertically adjustable pupil. The tapetum lucidum, a reflective layer behind the retina in feline eyes, acts as a photonic crystal with rod-like structures that reflect incoming light back through the retina for a second absorption.“

“This mechanism increases light sensitivity compared to human eyes. Additionally, in low-light environments, a cat’s pupil can dilate to a full circular shape, allowing more light to enter. By mimicking these two features, the camera’s sensitivity in low-light conditions can be significantly improved.”

Vertical pupils also help cats control light levels in both bright and dim conditions while simultaneously creating a vertically blurred background, allowing cats to filter out excess background noise.

“First, to replicate the tapetum lucidum, a silver metal reflector is positioned behind the image sensor. This design choice eliminates the wavelength dependence inherent in biological tapetum lucidum, ensuring a more uniform reflection of light across different wavelengths,” Minseok Kim explains.

Feline-inspired camera

Inspired by the feline eye, Kim and team developed a custom vertical slit aperture and a hemispherical silicon photodetector array with silver reflectors.

As Kim explains, “Traditional cameras typically use a small circular aperture, especially in brightly lit conditions, resulting in a deep depth of field where both the background and the object are in sharp focus. This can make it difficult to distinguish the object from a complex background.”

“In contrast, the vertical pupil camera inspired by feline eyes utilizes a vertically oriented pupil, which creates an asymmetric depth of field. This vertical aperture narrows the depth of field, causing the background to appear blurred while keeping the object in sharp focus.”

“This selective focus enhances the camera’s ability to distinguish objects from their backgrounds, improving object recognition in environments with complex or cluttered backgrounds.”

To evaluate their design, they compared the performance of their “vertical pupil” camera with a standard small circular aperture camera. When tested in an object recognition model with complex backgrounds, the vertical pupil camera achieved over 10% higher accuracy than the circular aperture camera.

Limitations of the camera

The researchers acknowledge that the vertical pupil camera has limitations, particularly its relatively low pixel resolution. However, they point out that higher-quality image sensors are commercially available.

The camera also has a narrow field of view, a compromise similar to what cats and other animals with vertical pupils experience in nature.

“While the new camera design offers significant advancements in light sensitivity and object-background separation by mimicking feline eye structures, it does present certain limitations. The hemispherical shape and vertically adjustable aperture can complicate integration into existing devices, which are typically designed for flat or rectangular sensors,” says Kim.

“Additionally, the mechanical complexity of the adjustable aperture may lead to higher manufacturing costs and potential maintenance challenges. To address these limitations and enhance the camera’s versatility for real-world applications, researchers are focusing on developing more compact and adaptable designs that maintain the benefits of the hemispherical sensor while ensuring compatibility with a variety of devices, including smartphones, drones, and automotive systems,” the researcher concludes.

The study has been published in Science Advances .