“Scanning squid” does not refer to a unique species but describes a visual behavior some squid use to perceive their environment in three dimensions. This behavior is a biological workaround for accurately judging distances. Scanning is an active process of movement and visual adjustment that unlocks a 3D understanding of their surroundings. It represents a different approach to depth perception compared to the methods used by humans.
The Visual Anatomy of the Longfin Inshore Squid
The creature known for this visual strategy is the longfin inshore squid, or Doryteuthis pealeii. This species is found along the eastern coastline of North America. To understand how it “scans,” one must first look at its unique eyes.
The squid’s visual system is distinguished by an unusually shaped pupil, which resembles the letter ‘W’. This W-shaped pupil is a piece of biological hardware. The shape allows light to enter the eye from various angles and focal points simultaneously, forming the foundation for its method of depth perception.
The longfin inshore squid’s vision is effectively colorblind. Its eyes contain only a single type of photoreceptor, the cells responsible for detecting light. While this might seem like a disadvantage, this characteristic is perfectly adapted for its specific method of seeing the world in 3D.
Scanning as a Method for Depth Perception
The scanning behavior is a physical action. To judge the distance of an object, the squid rhythmically rocks its body from side to side. As it does this, it also moves its eyes, allowing it to view the target from slightly different perspectives.
This process exploits a physical principle known as chromatic aberration, the failure of a lens to focus all colors at the same point. A simple lens does something similar to a prism, causing different colors of light to have slightly different focal points. A red object and a blue object at the same distance will create images that are focused at slightly different depths within the eye.
The squid’s brain leverages this phenomenon. As the squid moves, the image of an object shifts on its retina, and the degree of blur caused by chromatic aberration changes. Because the squid is colorblind and has only one photoreceptor type, it is not distracted by the colors themselves. Its brain is finely tuned to interpret the specific amount of blur to calculate an object’s distance.
This method stands in stark contrast to the stereoscopic vision used by humans. We perceive depth because our two forward-facing eyes each see a slightly different image of the world. Our brain combines these two images to create a single, three-dimensional picture. The longfin inshore squid achieves a similar outcome with a system that relies on motion and the physics of light.
Applications in Robotics and Imaging
The squid’s visual system provides a blueprint for technological development, a field known as biomimicry. By copying the principles of the squid’s scanning behavior, researchers aim to create new and more efficient imaging systems.
A primary application is in the development of compact, single-lens 3D cameras. The squid’s method demonstrates that depth perception is possible without two separate lenses. A single-lens system based on this principle would be smaller, lighter, and less mechanically complex, making it ideal for use in small drones or other autonomous robots where space and weight are constraints.
In medicine, miniature 3D cameras could be incorporated into endoscopic devices, giving surgeons a better sense of depth while performing minimally invasive procedures. The core benefit of the squid-inspired approach is its ability to achieve 3D perception from a streamlined design. This circumvents the engineering challenges associated with aligning and calibrating two-camera systems.