Polarization camera

Ricoh has developed a polarization camera that can acquire polarization information from a subject in real-time.

A polarization camera can acquire polarization information from a subject. Light contains amplitude (brightness), wavelength (color), and polarization information. Although human beings are able to sense brightness and the color of visible light, we are not able to sense polarization information. Insects with compound eyes have the ability to sense polarization, and it is said that they perceive a world quite different from our own.

Acquisition of polarization information　with a normal camera allows only changes in intensity as a polarization filter rotates in front of the camera to be viewed. Ricoh has developed a polarization camera that captures polarization images in real-time without mechanically adjusting the polarization filter or other parameters. A polarization camera makes it easier to acquire information on the surface orientation of hard-to-distinguish single-colored objects and　to recognize hard-to-distinguish differences between transparent surfaces and non-transparent surfaces. A broad range of applications is possible, including factory automation (FA), of course, but also the security, pharmaceutical, and food industries.

By precisely mounting a region-dividing, sub-wavelength structure (SWS) polarization filter on a CMOS sensor, a Ricoh polarization camera can acquire polarization information that has been difficult to capture with conventional cameras.

Usage scenario 1: capturing single-colored subjects

Until now, it has been difficult to determine the shape of a single-colored subject from a captured image in some cases.
A polarization camera, however, makes it easier to detect differences in the surface orientation of single-colored subjects. This is because the polarized state of light from a subject differs depending on the surface orientation of that subject. These differences can be captured as polarization images with a polarization camera. Potential applications include object recognition for single-colored objects in a production line.

Figure 1: Usage scenario for capturing single-colored subjects

Brightness (luma) image With a luma image, the shapes of single-colored objects cannot be determined.	Polarization image With a polarization image, distinguishing between circular and rectangular columns is possible.
Figure 2: Comparison of imaging with normal camera (left) and polarization camera (right)

Usage scenario 2: capturing transparent subjects

Until now, it has been difficult in some cases to determine the presence of transparent subjects from a captured image.
A polarization camera, however, makes it easier to detect the presence of transparent subjects. This is because when light passes through a transparent subject, its polarization changes depending on the transmittance of that subject. These differences can be captured as polarization images with a polarization camera. Potential applications include object recognition for transparent objects on a production line.

Figure 3: Usage scenario for capturing transparent subjects

Brightness (luma) image With a luma image, the ice block is invisible.	Polarization image With a polarization image, the ice block is visible.
Figure 4: Comparison of imaging with normal camera (left) and polarization camera (right)

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