Liquid Lens Technology Research Articles

Improving Iris Recognition with Liquid Lens Technology

AbstractIris identification and verification systems have become one of the most accurate biometric modalities due to the iris's unique and distinguishable features. Technical advances have significantly reduced the cost and size of these systems, leading to an increase in the value proposition for several industries. Image resolution and quality of focus are essential in deciphering the complex texture of the iris. Conventional iris recognition devices require bulky and high‐cost systems to overcome the optical constraints of mechanical lens‐based cameras. This paper describes how the use of a liquid lens device can overcome the optical limitations of traditional systems, leading to a low‐cost, smaller, and faster system.

The vehicle zoom ultra wide angle lens design by using liquid lens technology

As camera technology develops, products have improved and people have an increasing demand for visual quality. To increase the field of view, many zooming modules have been designed, which has raised the cost of optic components, increased the amount of calculation required, and complicated image processing technology. To date, dashcam lenses are primarily a compensatory design that cannot autozoom. Developing technology with various focuses for use on different roads has become a critical topic for autopilot development. Possibilities include using a short focus on general roads and using a long focus for freeways. Dashcam lens design requires the ability to cover wide angles. The concept behind wide-angle zooming lenses is that when the focal length is the shortest, the widest monitoring range is achieved. To observe a point at a far distance, we can use optical zoom to increase the focal length, thereby enabling a view into the distance. At this time, the angular field of view is sacrificed. However, a reduction of the angular field of view leads to a reduction of distortion, which subsequently reduces the complexity of back-end image processing and leads to clearer images. The design in this study references the wide-angle lens patent US.20090080093 (Ning in Compact fisheye objective lens, U.S., Patent No. 20090080093, 2011) of Alex Ning, whose optical system consists of six spherical lenses. The angular field of view reached 170°. The total system length is 18 mm, and F/# is 3. The system focus is 1.652 mm. Four groups of liquid lenses were placed in this wide-angle lens. Altering the curvature and thickness of the liquid lenses changes the course of light and forms a new angular field of view. This system consists of three zoom settings, with fields of view being 170°, 160°, and 150°, respectively. The F/# was 2.4. The modulation transfer function at a spatial frequency of 1801 p/mm reached 6%, 0%, and 27%, respectively. F-Theta was controlled within ± 10%. The spot size was smaller than 4 μm, and the field curvature was smaller than ± 0.02 mm. The liquid lenses were successfully introduced into the wide-angle lens to achieve optical zoom without using a conventional mobile mechanical structure.

Five-dimensional two-photon volumetric microscopy of in-vivo dynamic activities using liquid lens remote focusing.

Multi-photon scanning microscopy provides a robust tool for optical sectioning, which can be used to capture fast biological events such as blood flow, mitochondrial activity, and neuronal action potentials. For many studies, it is important to visualize several different focal planes at a rate akin to the biological event frequency. Typically, a microscope is equipped with mechanical elements to move either the sample or the objective lens to capture volumetric information, but these strategies are limited due to their slow speeds or inertial artifacts. To overcome this problem, remote focusing methods have been developed to shift the focal plane axially without physical movement of the sample or the microscope. Among these methods is liquid lens technology, which adjusts the focus of the lens by changing the wettability of the liquid and hence its curvature. Liquid lenses are inexpensive active optical elements that have the potential for fast multi-photon volumetric imaging, hence a promising and accessible approach for the study of biological systems with complex dynamics. Although remote focusing using liquid lens technology can be used for volumetric point scanning multi-photon microscopy, optical aberrations and the effects of high energy laser pulses have been concerns in its implementation. In this paper, we characterize a liquid lens and validate its use in relevant biological applications. We measured optical aberrations that are caused by the liquid lens, and calculated its response time, defocus hysteresis, and thermal response to a pulsed laser. We applied this method of remote focusing for imaging and measurement of multiple in-vivo specimens, including mesenchymal stem cell dynamics, mouse tibialis anterior muscle mitochondrial electrical potential fluctuations, and mouse brain neural activity. Our system produces 5 dimensional (x,y,z,λ,t) data sets at the speed of 4.2 volumes per second over volumes as large as 160 x 160 x 35 µm3.

Ten Years of Gabor-Domain Optical Coherence Microscopy.

Gabor-domain optical coherence microscopy (GDOCM) is a high-definition imaging technique leveraging principles of low-coherence interferometry, liquid lens technology, high-speed imaging, and precision scanning. GDOCM achieves isotropic 2 μm resolution in 3D, effectively breaking the cellular resolution limit of optical coherence tomography (OCT). In the ten years since its introduction, GDOCM has been used for cellular imaging in 3D in a number of clinical applications, including dermatology, oncology and ophthalmology, as well as to characterize materials in industrial applications. Future developments will enhance the structural imaging capability of GDOCM by adding functional modalities, such as fluorescence and elastography, by estimating thicknesses on the nano-scale, and by incorporating machine learning techniques.

Extended Depth-of-Field Projector by Fast Focal Sweep Projection.

A simple and cost-efficient method for extending a projector's depth-of-field (DOF) is proposed. By leveraging liquid lens technology, we can periodically modulate the focal length of a projector at a frequency that is higher than the critical flicker fusion (CFF) frequency. Fast periodic focal length modulation results in forward and backward sweeping of focusing distance. Fast focal sweep projection makes the point spread function (PSF) of each projected pixel integrated over a sweep period (IPSF; integrated PSF) nearly invariant to the distance from the projector to the projection surface as long as it is positioned within sweep range. This modulation is not perceivable by human observers. Once we compensate projection images for the IPSF, the projected results can be focused at any point within the range. Consequently, the proposed method requires only a single offline PSF measurement; thus, it is an open-loop process. We have proved the approximate invariance of the projector's IPSF both numerically and experimentally. Through experiments using a prototype system, we have confirmed that the image quality of the proposed method is superior to that of normal projection with fixed focal length. In addition, we demonstrate that a structured light pattern projection technique using the proposed method can measure the shape of an object with large depth variances more accurately than normal projection techniques.

Liquid lens technology

Liquid lens technology

Optical design of a dynamic focus catheter for high-resolution endoscopic optical coherence tomography

The optical system design of a dynamic focus endoscopic probe for optical coherence tomography is reported. The dynamic focus capability is based on a liquid lens technology that provides variable focus by changing its curvatures in response to an electric field variation. The effects of a cylindrical exit window present, in practice, for a catheter were accounted for. Degradation in image quality caused by this window was corrected to get diffraction limited imaging performance. As a result, the dynamically focusing catheter with a lateral resolution ranging from 4 to 6 mum through an approximately 5 mm imaging distance was designed without mechanically refocusing the system.