Design of a MEMS-based retina scanning system for biometric authentication

Abstract

There is an increasing need for reliable authentication for a number of applications such as e commerce. Common authentication methods based on ownership (ID card) or knowledge factors (password, PIN) are often prone to manipulations and may therefore be not safe enough. Various inherence factor based methods like fingerprint, retinal pattern or voice identifications are considered more secure. Retina scanning in particular offers both low false rejection rate (FRR) and low false acceptance rate (FAR) with about one in a million. Images of the retina with its characteristic pattern of blood vessels can be made with either a fundus camera or laser scanning methods. The present work describes the optical design of a new compact retina laser scanner which is based on MEMS (Micro Electric Mechanical System) technology. The use of a dual axis micro scanning mirror for laser beam deflection enables a more compact and robust design compared to classical systems. The scanner exhibits a full field of view of 10° which corresponds to an area of 4 mm2 on the retinal surface surrounding the optical disc. The system works in the near infrared and is designed for use under ambient light conditions, which implies a pupil diameter of 1.5 mm. Furthermore it features a long eye relief of 30 mm so that it can be conveniently used by persons wearing glasses. The optical design requirements and the optical performance are discussed in terms of spot diagrams and ray fan plots. There is an increasing need for reliable authentication for a number of applications such as e commerce. Common authentication methods based on ownership (ID card) or knowledge factors (password, PIN) are often prone to manipulations and may therefore be not safe enough. Various inherence factor based methods like fingerprint, retinal pattern or voice identifications are considered more secure. Retina scanning in particular offers both low false rejection rate (FRR) and low false acceptance rate (FAR) with about one in a million. Images of the retina with its characteristic pattern of blood vessels can be made with either a fundus camera or laser scanning methods. The present work describes the optical design of a new compact retina laser scanner which is based on MEMS (Micro Electric Mechanical System) technology. The use of a dual axis micro scanning mirror for laser beam deflection enables a more compact and robust design compared to classical systems. The scanner exhibits a full field of view of 10° which corresponds to an area of 4 mm2 on the retinal surface surrounding the optical disc. The system works in the near infrared and is designed for use under ambient light conditions, which implies a pupil diameter of 1.5 mm. Furthermore it features a long eye relief of 30 mm so that it can be conveniently used by persons wearing glasses. The optical design requirements and the optical performance are discussed in terms of spot diagrams and ray fan plots

MEMS scanner mirror based system for retina scanning and in eye projection

“…The setup corresponds to the optical design illustrated in figure 3. Figure 9: Image of a highly reflective USAF 1951 test chart made with the MEMS based retina scanning demonstration [22]. Furthermore we succeeded in obtaining images of a black-and-white dia-negative of an SLO-photography with 512 x 512 pixels.…”

“…The dual axes resonantly driven MEMS mirror oscillates with a slow axis resonant frequency of 186 Hz and a fast axis resonant frequency of 1.254 kHz. Acquisition and reconstruction of the images result from a lissajous pattern [22], [24], [25].…”

“…. Figure 8: Laboratory system demonstrational setup consisting of catalog components [22]. The setup corresponds to the optical design illustrated in figure 3.…”

“…The feedback of the MEMS position information is needed for the projection by modulation of the VIS laser and the image reconstruction[22].All light sources in the left block of figure 2 consist of a laser diode with a customized beam shaping optics. The VISlaser is required for the retina display.…”