Optical differentiator developed with full differentiation and adjustable edge detection
Optical differentiator developed with full differentiation and adjustable edge detection lead image
Optical differentiators used for image edge detection have applications in the rapidly advancing field of analog optical computing and image processing. However, most optical differentiators can only achieve partial differentiation and are wavelength dependent and doesn’t allow for easy control of the edge detection, a key requirement for high speed image processing applications. While there exist wave independent differentiators based on specific nanostructures, those devices are often expensive and complex to manufacture.
He et al. demonstrated an optical differentiator with full differentiation by harnessing the polarization freedom of the incident beam. Unlike previous optical differentiators, the author’s prototype is based on two polarizers and an air-glass interface, with a geometric configuration that enables full differentiation.
“Based on the designed differentiator, for any input image, its edge information could be obtained directly,” said author Hailu Luo.
By taking advantage of the purely geometric nature of spin-orbit interaction of light, the device can fully differentiate any wavelength of the incident light and process a complete image in one shot. According to the authors, the simplicity of their design means that their differentiator is easier and cheaper to manufacture compared to graphene-based differentiators that requires complex nanofabrication processes.
The authors successfully tested their differentiator on wavelength-independent image processing of edge detection.
“Compared with the development bottleneck of traditional digital signal processing technology, optical analog signal processing technology has the advantages of low power consumption, high throughput, and ultra-fast parallel,” said Luo. “The proposed optical differentiator may find important applications in autonomous driving, pattern recognition, and microscopic imaging.”
Future applications of the technique may be applied to microscopic imaging to observe pure phase objects such as transparent biological cells.
Source: “Wavelength-independent optical fully differential operation based on the spin-orbit interaction of light,” by Shanshan He, Junxiao Zhou, Shizhen Chen, Weixing Shu, Hailu Luo, and Shuangchun Wen, APL Photonics (2020). The article can be accessed at https://doi.org/10.1063/1.5144953 .
