Improved Monte Carlo model for multiple scattering calculations

Cai, Weiwei; Ma, Lin

doi:10.3788/col201210.012901

Cited by 12 publications

(1 citation statement)

References 16 publications

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“…Thus, we simulated the parameters of the grating to optimize the diffraction efficiency using a finite difference time domain (FDTD Solutions, Lumerical). In order to rigorously illustrate the model and verify the feasibility of the proposed structure, we built a 3D geometric model of the fingerprint system using the commercial software LightTools, which traces the light beams based on the Monte Carlo method [17,18] . We will illustrate the procedures separately.…”

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Slim OFRS based on a grating input coupler and a microprism sensing surface

Cui

Zheng³

et al. 2016

中国光学快报

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A slim optical fingerprint recognition sensor (OFRS) based on a grating input coupler and a microprism sensing surface is proposed. By using a subwavelength grating coupler, input light is coupled into the planar waveguide and the propagation angle is well engineered to avoid image overlap, thus an undistorted fingerprint is captured. For maintaining a thin structure, a microprism array is utilized to facilitate the breaking of total internal reflection under a large diffraction angle from the grating. The feasibility, efficiency, and image quality of the proposed structure are verified and discussed. The device has the advantages of a slim structure, a high image contrast, and a compact architecture, suitable for mobile devices.Fingerprint recognition technology plays an important role in information security, especially for access controllers and mobile devices. There have been a variety of sensing approaches to capturing fingerprints that have advantages and weaknesses [1] . Capacitive fingerprint sensors [2] are widely used in mobile phones owing to their thin structure, but the cost is rather high because of the small size of the sensing units. Also, the opaqueness of the sensing area brings about more difficulties for the capacitive type to be embedded on a display screen, such as the Apple Touch ID [3] , which places the capacitive sensors on the nontransparent "home" button. Although ultrasonic types [4] can capture a 3D fingerprint image with a high image quality, their cost is even higher due to the need for piezoelectric materials. Optical sensors are more attractive in view of the economic concerns as well as their superb durability. As an example of the mature application of an optical fingerprint recognition sensor (OFRS) in an access control system, usually a right angle prism is used to reflect laser beams by total internal reflection (TIR) and then the fingerprints put on the hypotenuse are obtained [5] . However, the bulky prism makes it impossible to be integrated into smart devices. Consequently, several types of OFRS were reported to meet the growing demand of device miniaturization as well as the veracity and fidelity of the fingerprint image. Ni proposed a sensor based on an optical waveguide to obtain a thinner system [6] , but the uniformity of the fingerprint image was limited. Although many researchers have made some specific improvements [7][8][9] recently, it is still very challenging to make a low cost, high image contrast, and compact structure OFRS.In this work, we demonstrate an OFRS with both a high image contrast and slim structure. Our structure comprises a grating to in couple light beams into a planar waveguide and a microprism array to assist out coupling of the waveguide light. Through integrating the micro prism array into the fingerprint detection region on the surface of the planar waveguide, the normal direction on the contact surface is changed. This appropriate change not only helps the finger ridge frustrate the TIR, but also deflects the scattering light of the fing...

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confidence: 99%