Polarsens is a CMOS Image Sensor pixel technology that has several different angle polarizer formed on chip during the semiconductor process allowing highly accurate alignment with pixel. This allows it to solve issues faced in various industrial areas.
*) *Polarsens and logo are trademarks of Sony Group Corporation.
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Four directional polarizer is formed on the image sensor
Sony’s polarization sensor can capture a four directional polarization image in one shot by the four directional polarizer (Fig.1). It can calculate the direction and degree of polarization (DoP) based on the intensity of each directional polarization. Together with subsequent signal processing, it can capture the polarization information*1 in real time*2.
*1) Degree of Polarization and Direction of Polarization
*2) Subject to subsequent signal processing power.
Polarizer is formed on chip under the on-chip lens layer
With conventional types of polarization sensors, the polarizer is attached on top of the on-chip lens layer (Fig.2), however with Sony’s polarization sensor, the polarizer is formed on chip under the on-chip lens layer (Fig.3). A shorter distance between the polarizer and the photodiode improves the extinction ratio*3 and the incident angle dependence.
Since the polarizer is formed during the semiconductor process, form and formulation of polarizer, uniformity, mass productivity and durability are excellent compared to conventional polarization sensors. Furthermore, Sony’s Polarization sensor is covered with an anti-reflection layer which helps to reduce reflectance and avoids poor flare and ghost characteristics.
*3) Extinction ratio is a specification to measure polarization. The extinction ratio of polarization image sensor is the ratio between the sensitivity of transmission axis light and the sensitivity of extinction axis light (the sensitivity of transmission axis light / the sensitivity of extinction axis light). The higher the number, the better the specification and performance.
What is polarization?
Light has physical elements : brightness (amplitude), color (wavelength) and polarization (vibration direction). Lights from the Sun or fluorescent lamps vibrate in various directions and is called unpolarized light.
Sony’s polarization sensor has wire-grid polarizers. Parallel light against polarizer passes through it, while perpendicular light is cut off at the polarizer.
Degree of Polarization and Polarization Direction
Polarization has two physical information, which are the degree of polarization and the direction of polarization. This information can be used for various applications such as surface scratch detection, particle inspection, distortion and shape recognition which has traditional been difficult to detect.
Example of Degree of Polarization (DoP)
The light is reflected by the surface of the object in polarized and unpolarized lights. The DoP of the reflected light depends on the surface condition (material, color, roughness etc.) and the angle of reflection.
In the Degree of Polarization image (Fig.6) the white is high polarization and black is low polarization.
As example, the stitch is easily visible due to the difference in the degree of polarization of the thread and leather.
Example of Polarization Direction
Polarization direction provides the direction information of reflected plane of an object.
The direction of polarization image (Fig.8) shows the angle of the polarization direction in color using HSV color mapping (Fig.9).
In this example, the upper side of the cube is highlighted in light blue meaning that the angle of the polarization direction is 90 degree (according to Fig.9).
Plane surface fine scratch detection
To detect fine scratches on plane surfaces which are completely uniform like glass at manufacturing sites, it is necessary to distinguish between scratches and stains. Since scratches differ from stains in that they have a specific orientation, polarization image sensors can be applied to focus on those properties.
Polarization image sensors can reliably identify differences in the degree of polarization between uneven areas, accurately perceiving scratches with a specific direction and detecting them while distinguishing them from stains which have random irregularities.
Detection of scratches and stains on glass
These examples show dents and dust on a homogenous glass plane.（Left/Right） We can easily find scratches and stains (fingerprint and dust) due to differences in the degree of polarization. （Right）
Container content inspections
Differences in the degree of polarization can be utilized at manufacturing sites to detect container content. For example, in picking work for LSI chips they can be used to confirm whether chips have been placed to fit in the correct position. In pharmaceutical manufacturing, differences in the degree of polarization between tablets and aluminum sheets can be applied to confirm tablet container content.
Example of visualization of polarization difference between aluminum sheet and tablets
Thanks to the difference in the degree of polarization between the tablet and the aluminum package, it is easy to identify whether the tablets are filled in or not. (Right)
Polarization image sensors can be used for distortion inspections in various manufacturing industries. They can accurately detect the presence of distortion without becoming confused by color or reflections, and can even detect the direction of distortions.
Warping in eyeglass frame
With the information of direction of polarization, we can identify both distortions and the direction of distortion of the plane. (Right)
Confirmation of number of individuals in vehicles (reflection removal)
In observations conducted by fixed-point cameras for the enforcement of traffic regulations, light can be reflected by vehicle windshields depending on the time period and angle, making it impossible to identify individuals in the vehicle. By setting polarization image sensors as appropriate, this reflected light can be reduced or removed, allowing the number of individuals in the vehicle to be detected.
A list of cameras with polarization image sensors
Download a list of cameras that incorporate Sony's polarization image sensors
"The Principle of Reflection Removal Utilizing Polarization and Features of Polarization Image Sensor"
Introducing the details of polarization Image Sensor Technology Polarsens.
Polarization Image Sensor overview
2-page summary of Sony's polarization image sensors
Related Products & Solutions
Polarization Image Sensor
Find out more about Polarization image sensors using this technology.
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