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.
Polarizer image
Source: Sony, IEDM2016, Lecture number 8.7
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Sony Semiconductor Solutions’ 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*3 in real time*4.
Fig.1. Structure
With conventional types of polarization sensors, the polarizer is attached on top of the on-chip lens layer (Fig.2), however with Sony Semiconductor Solutions’ 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*5 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 Semiconductor Solutions’ Polarization sensor is covered with an anti-reflection layer which helps to reduce reflectance and avoids poor flare and ghost characteristics.
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.
Fig.4.
Sony Semiconductor Solutions’ polarization sensor has wire-grid polarizers. Parallel light against polarizer passes through it, while perpendicular light is cut off at the polarizer.
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.
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.
Fig.5. Normal image
Fig.6. Degree of Polarization image
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.
Polarization direction provides the direction information of reflected plane of an object.
Fig.7. Normal image
Fig.8. Polarization Direction image
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).
Fig.9. HSV color mapping
Fig.10. Normal image
Fig.11. Degree of Polarization image
These examples show dents and dust on a homogenous glass plane. We can easily find scratches and stains (fingerprint and dust) due to differences in the degree of polarization. (Fig.10,11)
Fig.12. Normal image
Fig.13. Degree of Polarization image
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. (Fig.13)
Fig.14. Normal image
Fig.15. Polarization Direction image
With the information of direction of polarization, we can identify both distortions and the direction of distortion of the plane. (Fig.15)
Fig.16. Normal image
Fig.17. Removed reflection image
Polarization information can be used to remove reflections (Fig.17). Sony Semiconductor Solutions’ polarization sensor has a four-directional polarizer, which can simultaneously remove the reflections in multi planes.(Fig.17)
For more information about reflection removal for ITS use, please click here.
Our white paper about reflection removal is available here.
All images were generated by Sony Semiconductor Solutions’ polarization sensor’s evaluation board.
Polarization sensor that can capture a four directional polarization image in one shot
Together with subsequent signal processing, it can capture the polarization information in real time.
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White Paper
The Principle of Reflection Removal Utilizing Polarization
and Features of Polarization Image Sensor
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