Fig 3 - uploaded by Pierre Craen
Content may be subject to copyright.
Schematic drawing of auto focus camera for sequential acquisition of monochrome sharp images in the red (top), green (middle) and blue (bottom). LL -liquid lens, FL -fixed lens, I -Imager.
Source publication
Miniaturized camera systems are an integral part of today's mobile phones which recently possess auto focus functionality. Commercially available solutions without moving parts have been developed using the electrowetting technology. Here, the contact angle of a drop of a conductive or polar liquid placed on an insulating substrate can be influence...
Context in source publication
Context 1
... easier if the chromatic aberrations are not corrected by the optic but a somehow different algorithm. The zoom lens is based on adaptive lenses which are also used for the compensation of image shift due to different object distances (auto focus). It is therefore possible to adapt the liquid lenses to generate a sharp image in red, green or blue (Fig. ...
Similar publications
Most studies on electrowetting (EW) involve the use of AC electric fields, which cause droplets to oscillate in response to the sinusoidal waveform. Oscillation-driven mixing in droplets is the basis for multiple microfluidic applications. Presently, we study the voltage and AC frequency-dependent oscillations of electrowetted water droplets on a s...
Citations
... The moved group provided the required change in power to achieve the different focal lengths. The system had a 2.5× zoom ratio and the optical power range was 108 dioptries [93,94]. Yen et al proposed a 9× zoom imaging system by cascading two subsystem zoom groups. ...
An optical zoom imaging system that can vary the magnification factor without displacing the object and the image plane has been widely used. Nonetheless, conventional optical zoom imaging systems suffer slow response, complicated configuration, vulnerability to misalignment during zoom operation, and are incompatible for miniaturized applications. This review article focuses on state-of-the-art research on novel optical zoom imaging systems that use adaptive liquid lenses. From the aspect of the configuration, according to the amount of the adaptive liquid lenses, we broadly divide the current optical zoom imaging systems using adaptive liquid lenses into two configurations: multiple adaptive liquid lenses, and a single adaptive liquid lens. The principles and configurations of these optical zoom imaging systems are introduced and represented. Three different working principles of the adaptive liquid lens (liquid crystal, polymer elastic membrane, and electrowetting effect) adopted in the optical zoom imaging systems are reviewed. Some representative applications of optical zooming imaging systems using adaptive liquid lenses are introduced. The opportunities and challenges of the optical zoom imaging systems using adaptive liquid lenses are also discussed. This review aims to provide a snapshot of the current state of this research field for attracting more attention to put forward the development of the next-generation optical zoom imaging systems.
... The optical lens is currently an important optical component in three-dimensional (3D) imaging 1 , optocouplers 2 , and miniature cell phones 3 . To meet the demand for the miniaturization and magnification of optical components, many researchers have investigated liquid lenses 4 and membrane lenses 5 . ...
Electrical control toolkits for microlens arrays are available to some extent, but for applications in environments with strong electromagnetic fields, radiation, or deep water, non-electrical actuation and control strategies are more appropriate. An integrated digital microfluidic zoom actuating unit with a logic addressing unit for a built-in membrane lens array, e.g., a flexible bionic compound eye, is developed and studied in this article. A concave–convex membrane fluidic microvalve, which is the component element of the logic gate, actuator, and microlens, is proposed to replace the traditional solenoid valve. The functions of pressure regulation and decoding can be obtained by incorporating microvalves into fluidic networks according to equivalent circuit designs. The zoom actuating unit contains a pressure regulator to adjust the focal length of lenses with three levels, and the logic addressing unit contains a decoder to choose a typical lens from a hexagonal lens array. The microfluidic chip control system is connected flexibly to the actuating part, a membrane lens array. It is shown from a simulation and experimental demonstration that the designed and fabricated system, which is composed of a whole microfluidic zoom unit, addressing technology, and a microlens array, works well. Because these components are constructed in the same fabrication process and operate with the same work media and driving source, the system can be made highly compatible and lightweight for applications such as human-machine interfaces and soft robots.
... The liquid lens is a novel optical element which features dynamic adjustment of the lens refractive index or its surface shape to change the focal length. The liquid lens has the advantage of being able to change focal length without mechanically moving the lens, which can provide considerable power savings and can eliminate wear associated with moving parts [1], so it is widely used in a large variety of application areas, such as mobile phones [2], surgical instruments [3], miniature cameras [4], and so on. The doubleliquid lens [4][5][6][7] based on the electrowetting effect is highly regarded because of its outstanding performance [7]. ...
The effect of the liquid density difference on interface shape of a double-liquid lens is analyzed in detail. The expressions of interface shape of two liquids with liquid density difference are analyzed and fitted with "even asphere". The imaging analysis of the aspheric interface shape of a double-liquid lens is presented. The results show that the density difference of two liquids can cause the interface to be an aspheric surface, which can improve the image quality of a double-liquid lens. The result provides a new selection for the related further research and a wider application field for liquid lenses.
... This way, the fluids could manipulate mechanically and electrically and exploit the virtue of surface tension of the liquid [3]. When it comes to the mechanical method, the surface is displaced so as to adjust the lens' shape [4,5], whereas, in the case of the electric method, electrowetting [6,7] is the means by which the surface tension is adjusted. For some purposes, such as endoscopic medical imaging [8], fiber-optic telecommunication systems, or micro cameras, liquid lenses can be efficiently used, based on the boundary between the two fluids, thus constructing a regular and smooth surface [1,9]. ...
Extremely small cameras and many cell phones simply do not have enough room to allow users to move a rigid lens the distance required for a varying range of focal lengths. An adaptive liquid lens, however, enables small cameras to focus without needing extra room. An autofocus liquid lens provides several advantages over a traditional lens in terms of efficiency, cost, compactness, and flexibility. But one of the main challenges in these lenses is a high driving voltage requirement of around at least 1.8 kV. In this paper, we propose a new design of a liquid lens based on a dielectric elastomer stack actuator (DESA), which significantly overcomes the aforementioned existing problem. The lens consists of a frame (a thin DESA membrane with a hole in the middle), silicon oil, and water. A voltage range is applied on the membrane in order to change the hole dimension. Due to change of hole dimension, a change in meniscus occurs that changes the focal length of the lens. In this research work, various experimental results are achieved by configuring two DESA with different active areas. Depending on the active area of the membrane, the length of the laser beam on the plane varies from 6 to 35 mm, and the driving voltage is in the range of 50–750 V.
... One or more fluids are used to make an infinitely variable liquid lens without any moving parts by controlling the meniscus shape, i.e. the shape of the liquid/liquid or liquid/air interface. The fluids could manipulate mechanically and electrically which take advantage of the surface tension of the liquid[4]. In mechanical method, a mechanical displacement of surfaces is used in order to adjust the shape of the lens[5][6], while ellectrowetting[7][8] is used to change the surface tension in electric method. ...
... Using one or more fluids, unmoving, infinitely-variable liquid lenses can be produced for controlling the meniscus shape, which can be of liquid/liquid or liquid/air interface sorts. This way, the fluids could manipulate mechanically and electrically, and exploit the virtue of surface tension of the liquid [4]. When it comes to the mechanical method, the surfaced is displaced so as to adjust the lens' shape [5] [6], where in the case of electric method, ellectrowetting [7] [8] is the means by which the surface tension is adjusted. ...
Today most of applications have a small camera such as cell phones, tablets and medical devices. A micro lens is required in order to reduce the size of the devices. In this paper an auto focus system is used in order to find the best position of a liquid lens without any active components such as ultrasonic or infrared. In fact a passive auto focus system by using standard deviation of the images on a liquid lens which consist of a Dielectric Elastomer Actuator (DEA) membrane between oil and water is proposed.
... The principle of the reflective liquid lens is based on the variable mirror as a model, using mercury, and by applying centripetal forces to create a smooth reflective concavity. This approach reduces the cost ten times for such lenses, compared to the traditional way fixed on curved glass [4]. In contrast to the reflective fluid lens, the transmissive fluid lens [2] is based on an active change of the convex concave lens shape over immiscible fluids with a different refractive index. ...
... A liquid lens uses one or more fluids to create an infinitely-variable lens without any moving parts by controlling the meniscus (the surface of the liquid). There are two ways to manipulate the two fluids, electrically and mechanically, and both methods take advantage of the surface tension of the liquid [4]. The electric method uses a novel property called electro-wetting [5][6] to modify the surface tension, while the mechanical method takes advantage of surface tension to physically change the shape of the lens [7][8]. ...
The autofocus fluid lens device, as developed by Philips, is based on water/oil interfaces forming a spherical lens where the meniscus of the liquid can be switched by applying a high voltage to change from a convex to a concave divergent lens. In this work we construct a device to evaluate the performance of membrane actuators based on electro active polymers, in a design applicable for autofocus fluid lens applications. The membrane with a hole in the middle separates the oil phase from the electrolyte phase, forming a meniscus in the middle of the membrane between the oil and electrolyte. If the membrane actuator shows a certain force and displacement, the meniscus between oil and electrolyte changes form between concave and convex, applicable as a fluid lens. Ionic polymer metal composites (IPMCs) are applied in this work to investigate how the performance of the membrane actuator takes place in Milli-Q, certain electrolytes and in combination with an electrochemically deposited conducting polymer. The goal of this work is to investigate the extent of membrane displacement of IPMC actuators operating at a low voltage (±0.7 V), and the back relaxation phenomena of IPMC actuators.
... Therefore, imaging systems without moving elements have attracted considerable attention in recent years because of the advantages of small size and low power consumption. Applying liquid lenses is one of the more popular solutions [1][2][3][4]. A liquid lens contains two immiscible liquids: one is electrically conducting and the other is insulating. ...
... Therefore, the focal length of the liquid lens can be controlled by varying the applied voltage. In the past few years, much work has been done to autofocus [1] and zoom camera modules [2,3] using liquid lenses. However, liquid lenses suffer from the disadvantage of chromatic aberrations because of the different refractive indices of the two liquids. ...
... Unlike relatively small variation of diopters of autofocus systems, a larger variation of diopters of a zoom system without moving parts is needed, which means more severe bending of liquid lenses, and the chromatic aberration is not well controlled for all focal lengths. Although the chromatic aberration can be corrected by an image-processing algorithm, the exposure time needs to be extended by a factor of 3 to 4 [2]. Furthermore, the limited ability to change diopters of liquid lenses causes long total track length of the whole zoom systems, a challenge for contemporary electronic devices. ...
In recent years, optical zoom functionality in mobile devices has been studied. Traditional zoom systems use motors to change separation of lenses to achieve the zoom function, but these systems result in long total length and high power consumption, which are not suitable for mobile devices. Adopting micromachined polymer deformable mirrors in zoom systems has the potential to reduce thickness and chromatic aberration. In this paper, we propose a 2 × continuous optical zoom system with five-megapixel image sensors by using two deformable mirrors. In our design, the thickness of the zoom system is about 11 mm. The effective focal length ranges from 4.7 mm at a field angle of 52° to 9.4 mm. The f -number is 4.4 and 6.4 at the wide-angle and telephoto end, respectively.
... Multi-focal lengths can be achieved by varying the applied voltages, with one focus corresponding to one applied voltage. Lenses with two coaxial focuses had been proposed and realized in liquid lenses [9,10] and LC lenses [11,12]. In the current study, they are referred to as the optical feature of coaxial bifocals (CB). ...
Liquid crystal (LC) lenses with circular hole-patterned electrodes possess the excellent capabilities of tunable focal lengths. In this paper, we demonstrate the performance of a specific LC lens with tunable coaxial bifocals (CB) synthesized via photopolymerization of LC cells. The characteristics of tunable CB are clearly exhibited when the voltage applied is continuously increased, eventually disappearing until only one focus is left when significantly higher voltages are applied. We simultaneously demonstrate two types of tunable CB LC lenses fabricated via different photocurable processes and determine their optical functions.
... Individual optical elements of these classical optical systems mainly consist of glass lenses and the change of their optical parameters is done by translation of several elements of such optical systems [6][7][8]. Recently, optical elements with a continuously variable focal length are available, which makes possible to design special optical systems with variable focus and no mechanical movement of optical elements inside the optical system [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. We performed a detailed theoretical analysis [29] of a two-element zoom lens with the variable focal length. ...
... By substitution of relations (11) and (12) into Eq. (6) we obtain a set of two equations for incidence heights h 1 and h 2 . ...
... By inserting this value into formulas (13) we can calculate the incidence height 2 h . Then, from Eqs. (11) and (10) we can calculate the powers 1 2 3 , , ϕ ϕ ϕ and distances 1 2 , d d between the individual lenses of the triplet. Our analysis is more complex and exhaustive than the analysis presented in papers [31][32][33][34]. ...
Traditional optical systems with variable optical characteristics are composed of several optical elements that can be shifted with respect to each other mechanically. A motorized change of position of individual elements (or group of elements) then makes possible to achieve desired optical properties of such zoom lens systems. A disadvantage of such systems is the fact that individual elements of these optical systems have to move very precisely, which results in high requirements on mechanical construction of such optical systems. Our work is focused on a paraxial and aberration analysis of possible optical designs of three-element zoom lens systems based on variable-focus (tunable-focus) lenses with a variable focal length. First order chromatic aberrations of the variable-focus lenses are also described. Computer simulation examples are presented to show that such zoom lens systems without motorized movements of lenses appear to be promising for the next-generation of zoom lens design.
