A polarisation‐analysing CMOS image sensor for sensitive polarisation modulation detection

Abstract

In this study, a polarisation-analysing CMOS image sensor is fabricated for sensitive polarisation modulation detection. Although the image sensor with on-pixel polarisers can image the incident polarisation collectively, its sensitivity to a weak polarisation change is not high. With the proposed method, an external polariser is used to enhance the polarisation modulation sensitivity with a polarisation image sensor. The performance of this highly sensitive polarisation image sensor and imaging experiments are evaluated using a flow channel.

Polarization Image Sensor for Highly Sensitive Polarization Modulation Imaging Based on Stacked Polarizers

“…The ON-pixel polarizer was composed of the metal wiring layer of the CMOS process, as in previous chips [17]. The line and space were 0.5 and 0.45 μm, respectively.…”

“…To address these issues, we designed and fabricated a polarization image sensor with an ON-pixel polarizer and proposed a method for imaging small polarization modulation by constructing a multilayer polarizer, comprising an external polarizer and ON-pixel polarizers [17]. In a previous study, we detected weak polarization changes of 2.5 × 10 −3 • .…”

Improvement of on-pixel polarizer with 0.35 μm CMOS process for electro-optic imaging systems

“…The proposed system has a double-polarizer structure composed of signal-selective and on-pixel-analyzing polarizers. 27,28) The image sensor was fabricated using a standard CMOS process based on Si. A light source with a wavelength of 780 nm was selected, which is detectable using Si photodiodes.…”

“…In our previous work, the sensitivity of the system was sufficiently high to enable electric-field measurements even with a 0.35 μm standard CMOS process. 27,28) The extinction ratio enables polarization-separation performance in the polarizers. Obtaining a high extinction ratio with an on-pixel polarizer is more difficult compared to a uniform polarizer.…”

“…The extinction ratio of on-pixel polarizers at 780 nm was only 1.5, and there remains much room to improve the performance of the electric-field imaging system. 27,28) In this study, we compared the characteristics of on-pixel polarizers based on their structure. Additionally, we presented an enhancement in the extinction ratio by multilayering the polarizers.…”