Conventional optical elements are based on either refractive or reflective optics theory to fulfill the design specifications via optics performance data. In refractive optical lenses, the refractive index of materials and radius of curvature of element surfaces determine the optical power and wavefront aberrations so that optical performance can be further optimized iteratively. Although gradient index (GRIN) phenomenon in optical materials is well studied for more than a half century, the optics theory in lens design via GRIN materials is still yet to be comprehensively investigated before realistic GRIN lenses are manufactured. In this paper, 3D printing method for manufacture of micro-optics devices with special features has been studied based on methods reported in the literatures. Due to the additive nature of the method, GRIN lenses in micro-optics devices seem to be readily achievable if a design methodology is available. First, derivation of ray-tracing formulae is introduced for all possible structures in GRIN lenses. Optics simulation program is employed for characterization of GRIN lenses with performance data given by aberration coefficients in Zernike polynomial. Finally, a proposed structure of 3D printing machine is described with conceptual illustration.
Contact lenses are typically measured by the wet-box method because of the high optical power resulting from the anterior central curvature of cornea, even though the back vertex power of the lenses are small. In this study, an optical measurement system based on the Shack–Hartmann wavefront principle was established to investigate the aberrations of soft contact lenses. Fitting conditions were micmicked to study the optical design of an eye model with various topographical shapes in the anterior cornea. Initially, the contact lenses were measured by the wet-box method, and then by fitting the various topographical shapes of cornea to the eye model. In addition, an optics simulation program was employed to determine the sources of errors and assess the accuracy of the system. Finally, samples of soft contact lenses with various Diopters were measured; and, both simulations and experimental results were compared for resolving the controversies of fitting contact lenses to an eye model for optical measurements. More importantly, the results show that the proposed system can be employed for study of primary aberrations in contact lenses.
Identity certification in the cyberworld has always been troublesome if critical information and financial transaction must be processed. Biometric identification is the most effective measure to circumvent the identity issues in mobile devices. Due to bulky and pricy optical design, conventional optical fingerprint readers have been discarded for mobile applications. In this paper, a digital variable-focus liquid lens was adopted for capture of a floating finger via fast focusplane scanning. Only putting a finger in front of a camera could fulfill the fingerprint ID process. This prototyped fingerprint reader scans multiple focal planes from 30 mm to 15 mm in 0.2 second. Through multiple images at various focuses, one of the images is chosen for extraction of fingerprint minutiae used for identity certification. In the optical design, a digital liquid lens atop a webcam with a fixed-focus lens module is to fast-scan a floating finger at preset focus planes. The distance, rolling angle and pitching angle of the finger are stored for crucial parameters during the match process of fingerprint minutiae. This innovative compact touchless fingerprint reader could be packed into a minute size of 9.8*9.8*5 (mm) after the optical design and multiple focus-plane scan function are optimized.
Liquid lenses based on the principle of driving two dielectric fluids via controlled electric field were investigated with an
experimental apparatus designed for analysis of wave front read from a Shack-Hartmann sensor. Due to small available
aperture and requirements in dynamic responses, wave front measurement was selected for study of optical
characteristics in dielectric lenses. With the advent of commercial electro-optics sensors in wave front measurement, the
experimental apparatus was first designed and simulated with the help of ASAP program. The simulated results proved
the conceptual design with handful of engineering insights so that less trial and error efforts could be relieved from
building the optics system on the bench. In-house built liquid lens modules with driving circuits were then set on the
apparatus for initial calibration and functional tests. Since the electric field generated for the control of liquid profile
must be alternating current, various frequency and modulation schemes were put through the liquid lens module to
further study the influences on dynamic responses in terms of optical characteristics. Furthermore, effects due to
material impurity and ambient effects were also carefully studied for established the fundamental phenomena of liquid
lenses made of dielectric fluids. More detailed observations were possible with the measured wave-front data. In
conclusion, the wave-front measurement proved to be more reliable and less expensive compared to measurement based
The high filling factor double side micro lens array (MLA) for laser beam shaping has been widely applied in optoelectrical
applications. In this paper, we demonstrated the double side MLA for the laser beam shaping process. The
point laser source has been successfully transformed into a two dimension uniformity light imaging. The ultra-precision
slow tool servo (STS) diamond shaping and plastic injection method for MLA fabrication had been studied. The
complexity micro structure of high filling factor MLA via the planning of cutting tool path is used in this research. The
high alignment accuracy of both sides MLA is obtained by artful fixture design. The form accuracy and surface
roughness are less than 0.1μm and 10nm, respectively. The alignment error of both sides MLA is less than 10μm.
Three ultra-precision machining processes namely fast tool servo, slow tool servo and diamond milling, are frequently
used to produce optical freeform surface. Slow tool servo machining has the advantages of no extra attachment and fast
setting-up, however the three dimensional tool shape compensation and tool-path generation must be conducted carefully
for getting high form accuracy and fine surface finish. This research aimed to develop a model of three dimensional tool
shape compensation for generating 3D tool path in slow tool servo diamond turning of asymmetrically toric surface for
astigmatic contact lens. The form accuracy of freeform surface was measured by ultra-high accuracy 3D profilometer
(UA3P) with user define function. After correction, the form error is less than 0.5μm both in X- and Y-direction and the
surface roughness is less than 5nm.