Optical Zoom Lens Research Articles

Design of an optical passive semi-athermalization zoom lens

Traditional zoom lenses cannot clearly image during the entire zoom process when the ambient temperature changes and needs to focus frequently at middle focal length positions. An innovative design method called the optical passive semi-athermalization (OPSA) design for zoom optical systems is proposed which, based on the difference in the focusing sensitivity of the focusing group at short and long focal length positions, seeks out sensitive groups that have a greater impact on the imaging quality at the short focal position. By changing the temperature characteristics of the temperature-sensitive lenses in these groups, an OPSA zoom optical system can be realized, which exhibits a compact structure and excellent imaging quality. Under the ambient temperature of −40∘C to +60∘C, the OPSA zoom lens needs to refocus only once at the long focal length position, which can ensure an image clearly during the entire zoom process. Remarkably, this innovative method not only mitigates the frequent focusing challenges in traditional zoom lenses, but also contributes to the diminutive size.

Optical Design of a Miniaturized 10× Periscope Zoom Lens for Smartphones.

The size of the optical zoom system is important in smartphone camera design, especially as it governs the thickness of the smartphone. We present the optical design of a miniaturized 10× periscope zoom lens for smartphones. To achieve the desired level of miniaturization, the conventional zoom lens can be replaced with a periscope zoom lens. In addition to this change in the optical design, the quality of the optical glass, which also affects the performance of the lens, must be considered. With advancements in the optical glass manufacturing process, aspheric lenses are becoming more widely used. In this study, aspheric lenses are incorporated into a design for a 10× optical zoom lens with a lens thickness of less than 6.5 mm and an eight-megapixel image sensor. Furthermore, tolerance analysis is carried out to prove its manufacturability.

Practical technique for balancing the optical aberrations among conceptual thin-lens components of optical zoom lenses.

Solving conceptual thin-lens components with balanced optical aberrations among different optical configurations is essential for lens design from scratch. This paper presents a general and practical method for building conceptual thin-lens components that can be further optimized by Code V (a well-known optical design program) to approach specific aberration targets. The conceptual component consists of a Code V's lens module and a hologram with zero diffraction order. The latter provides spaces for storing the reference data of incident marginal and chief rays, spherical aberration, central coma, and longitudinal chromatic aberration without affecting the paraxial ray tracing. Those reference data are used to evaluate the real aberrations at different optical configurations by our earlier aberration variation algorithms [Appl. Opt.55, 10363 (2016)APOPAI0003-693510.1364/AO.55.010363]. The model helps investigate the properties of lenses and solve the balanced aberrations by the optimization process. An example of solving a zoom lens with different optimization goals is given to demonstrate the usage of the method. Detailed design data are listed for verification.

Design of IR zoom lens system for long-range detection in uncooled LWIR camera

A new compact optical zoom lens system with variable focal length 100–200 mm for uncooled LWIR (8–12 μm) camera is designed. It is used for long-range detection. The optimized IR zoom lens consists of four group elements. The F/# of the zoom system is F/1.4 at all zoom positions. Its performance reaches the diffraction limit at each focal length position. Moreover, optical design and image quality are calculated by ZEMAX optical software. The imaging quality performance is steady during zoom process. In addition to the above benefits, the optimized IR zoom lens is light and compact (200 mm) with 4 lenses and only one of them has diffractive surface to lower production cost. Upon applying anti-reflection coating, the total transmittance of the optical system is enhanced from 2 to 99% at λ = 10 µm.

Optical Design of Optical Passive Half-Athermalization Zoom Lens with High Zoom Ratio

Optical Design of Optical Passive Half-Athermalization Zoom Lens with High Zoom Ratio

The Evolving Temperature Field in a 1 m Methanol Pool Fire.

Thin filament pyrometry is used to measure the time-varying temperature field in a 1 m methanol pool fire. A digital camera with optical filters and zoom lens recorded the emission intensity of an array of 12 μm Silicon-Carbide filaments oriented horizontally at various heights across the steadily burning pool fire. A 50 μm diameter thermocouple measured the temperature at locations corresponding to the filament positions. A correlation was developed between the local probability density functions of the thermocouple time series measurements corrected for radiation and thermal inertia effects and the camera grayscale pixel intensity of the filaments. A regression analysis yields the local mean temperature and its variance. The time series of the temperature field is transformed into average values during consecutive phases of the fire's puffing cycle, providing quantitative insight into the complex and dynamic structure of a turbulent fire.

Building Stereoscopic Zoomer via Global and Local Warping Optimization

Magnifying left and right images by increasing focal length of optical zoom lenses is a direct way for stereoscopic zoom. However, without adjusting the baseline distance, the optical zoom may distort the three-dimensional (3D) perception. To tackle this problem, this article presents a stereoscopic zoomer that directly operates on image plane by synthesizing a virtual camera in depth direction to simulate the zoom process. Specifically, we propose a two-stage warping optimization framework for zooming, which is solved by imposing global and local energy constraints. Different from the existing 3D rendering methods, the important innovation of our method is to take content zoom, depth adaptation and user editability into account in mesh optimization. Experimental results demonstrate that our method can achieve promising zoom effect on daily person scenes and street views.

Thin Filament Pyrometry Field Measurements in a Medium-Scale Pool Fire

This paper presents the development of a thin filament pyrometry method to characterize the time-varying temperature field in a medium-scale pool fire burning in a quiescent environment. A digital camera with optical filters and zoom lens was used to record the high temperature emission intensity of 14 μm diameter, Silicon-Carbide filaments oriented horizontally at various heights above the center of a steadily burning 0.30 m diameter methyl alcohol (methanol; CH3OH) pool fire. Experiments collected 30 Hz video of the planar filament array. In a separate experiment, a 50 μm diameter thermocouple was used to acquire independent temperature measurements in the high temperature zone of the fire. A correlation was developed between the probability density functions of the radiation-corrected thermocouple measurements and the camera grayscale pixel intensity of the filaments. This arrangement enables measurement of the time-varying temperature field over a temperature range from about 1150 K to 1900 K with a spatial resolution of 160 μm, a temporal resolution of 0.033 s, and an expanded uncertainty of about 150 K (at a mean temperature of 1300 K). Measurements of the grayscale pixel intensities of the filaments were obtained. False color maps of the temperature field were produced to characterize the high temperature field as a function of time. Using statistical analysis, the local time-averaged temperatures and their variance for each location on the filaments were determined. Time-averaged temperatures were compared favorably to previously reported measurements. The dominant frequency of the puffing fire was determined. The temperature field time series was transformed to consider its character during consecutive phases of the fire's puffing cycle. The analysis emphasizes the cyclic nature of a pool fire, providing insight on its complex dynamic structure.

Displaceable and focus-tunable electrowetting optofluidic lens.

A conventional optofluidic lens usually has one liquid-liquid (L-L) interface, which can be deformed to achieve variable focal length. Such a single lens cannot be used alone to realize optical zooming because its back focal distance keeps changing. Here, we report a novel displaceable and focus-tunable electrowetting optofluidic lens. In comparison with the conventional optofluidic lens, our new lens has a different working principle and it can function as an optical zoom lens. The L-L interface can be displaced by a voltage. The object distance and image distance can be adjusted by shifting the L-L interface position to achieve the desired magnification, yet the lens can refocus the image by reshaping the L-L interface with another voltage. Under such condition, only one lens is adequate to realize the zooming functionality. To prove the concept, we fabricate an optofluidic lens whose largest displaceable distance is ~8.3 mm and the zooming ratio is ~1.31 ×. The proposed optofluidic lens greatly simplifies the zoom lens system. Widespread application of such an adaptive zoom lens is foreseeable.

Programmable Zoom Lens System with Two Spatial Light Modulators: Limits Imposed by the Spatial Resolution

In this work we present an experimental proof of concept of a programmable optical zoom lens system with no moving parts that can form images with both positive and negative magnifications. Our system uses two programmable liquid crystal spatial light modulators to form the lenses composing the zoom system. The results included show that images can be formed with both positive and negative magnifications. Experimental results match the theory. We discuss the size limitations of this system caused by the limited spatial resolution and discuss how newer devices would shrink the size of the system.

Tolerance reallocation of an optical zoom lens to meet multiperformance criteria.

This article demonstrates a method of tolerance reallocation via the Taguchi method for optical zoom lens design, which is based on the indicated specifications and corresponding tolerances derived from optical simulation in order to resolve the conventional dilemmas of performance between the modulation transfer function (MTF), relative illumination (RI), and distortion (DST) but also improve the performance without problems of tolerance. Generally speaking, the above refer to trade-offs between performance and tolerance of a kind which complicates modern optical design in high-quality products. In this paper, the Taguchi method of investigation was successfully adopted in seeking to balance MTF, DST, and RI so as to reallocate tolerance; therefore, we concluded that displays of multiperformance criteria can simultaneously give efficient help in tolerancing optimization in a way which approaches the exact manufacturing requirements. Without question, the proposed process could be copied when selecting other ways of evaluating image quality.

LOW COST SURVEYING USING AN UNMANNED AERIAL VEHICLE

Abstract. Traditional manned airborne surveys are usually expensive and the resolution of the acquired images is often limited. The main advantage of Unmanned Aerial Vehicle (UAV) system acting as a photogrammetric sensor platform over more traditional manned airborne system is the high flexibility that allows image acquisition from unconventional viewpoints, the low cost in comparison with classical aerial photogrammetry and the high resolution images obtained. Nowadays there is a necessity for surveying small areas and in these cases, it is not economical the use of normal large format aerial or metric cameras to acquire aerial photos, therefore, the use of UAV platforms can be very suitable. Also the large availability of digital cameras has strongly enhanced the capabilities of UAVs. The use of digital non metric cameras together with the UAV could be used for multiple applications such as aerial surveys, GIS, wildfire mapping, stability of landslides, crop monitoring, etc. The aim of this work was to develop a low cost and accurate methodology in the production of orthophotos and Digital Elevation Models (DEM). The study was conducted in the province of Almeria, south of Spain. The photogrammetric flight had an altitude of 50 m over ground, covering an area of 5.000 m2 approximately. The UAV used in this work was the md4-200, which is an electronic battery powered quadrocopter UAV developed by Microdrones GmbH, Germany. It had on-board a Pextax Optio A40 digital non metric camera with 12 Megapixels. It features a 3x optical zoom lens with a focal range covering angles of view equivalent to those of 37–111 mm lens in 35 mm format. The quadrocopter can be programmed to follow a route defined by several waypoints and actions and it has the ability for vertical take off and landing. Proper flight geometry during image acquisition is essential in order to minimize the number of photographs, avoid areas without a good coverage and make the overlaps homogeneous. The flight planning was done using the MdCockpit software, with the module waypoint editor. Flight route file was downloaded into the quadrocopter autonomous chip via cable. A total of twelve vertical images with a longitudinal and transversal overlapping of 60% and 50% respectively were taken. The digital camera was previously geometrically calibrated. Field control points covering the whole studied area were defined over the area of interest and their coordinates were measured by a GPS. Natural targets were used as field control points. The close range photogrammetric software Photomodeler Scanner v.7 was used in this work to calibrate the camera and to carry out the photogrammetric process. The software Golden Surfer was used to produce the DEM. The planimetric and the altimetric root mean square error (RMSE) were calculated in order to check the accuracy of the products. The RMSEx was 6 cm, the RMSEy was 4 cm and the RMSEy was 7 cm. Our preliminary results demonstrate the feasibility and accuracy of orthophotos and DEMs obtained from images captured from a quadrocopter using low cost photogrammetric software. A future work can be the comparison of the products obtained following the route used in this study where the images are taken vertically with the products obtained with an orbital route where the number of images will be diminished and the photos will be taken oblique.

X-ray stations based on cylindrical zoom lenses for nanostructural investigations using synchrotron radiation

The main results of the development of X-ray stations are presented. These stations are intended to solve problems concerning the structural biology of tissues at a high time resolution with the help of synchrotron radiation (SR) generated by the VEPP-3 storage ring (Siberian center of SR, Novosibirsk) and the Siberia-2 storage ring (National Research Centre Kurchatov Institute and the centre of nano-, bio-, information, and cognitive sciences, Moscow). The issues of selecting the optical scheme and basic parameters of X-ray optical systems are discussed. Photographs of the original designs of the constructed equipment are given. A modular approach to designing experimental facilities based on self-contained units and methods of focusing a monochromatic SR beam in the required spectral range have been developed. The technique of X-ray beam focusing by means of optical zoom lenses has been implemented. Experimental results that illustrate the possibilities of the SR-beamline hardware used for X-ray diffraction investigation of different biological objects with the help of different recording systems are presented.

Computational stereoscopic zoom

Optical zoom lenses mounted on a stereo color camera magnify each left and right two-dimensional (2-D) image increasing focal length. However, without adjusting the baseline distance, the optical zoom distorts three-dimensional (3-D) perception because the optical zoom magnifies projected 2-D images not an original 3-D object. We propose a computational approach to stereoscopic zoom that magnifies stereo images without 3-D distortion. We computationally manipulate the baseline distance and convergence angle between left and right images by synthesizing novel view stereo images based on the depth information. We suggest a volume-predicted bidirectional occlusion inpainting method for novel view synthesis. Original color image is warped to the novel view determined by the adjusted baseline and convergence angle. Rear volume of each foreground object is predicted, and the foreground portion of each occlusion region is identified. Then we apply our inpainting method to fill in the foreground and background respectively. Experimental results show that the proposed inpainting method removes the cardboard effect that significantly decreases the perceptual quality of synthesized novel view image but has never been addressed in the literature. Finally, 3-D object presented by stereo images is magnified by the proposed stereoscopic zoom method without 3-D distortion.

Applied Research on the Electric Wet Effect in Optical System Design

In the past half century, the camera industry has developed very rapidly, which drove the optical lens and optical zoom technology to make great progress. The zoom lens’ technology principle of current mainstream optical zoom lens system is achieved by adjusting the relative position of the lens, objects and the focus. This paper takes the double-liquid zoom lens based on electric wet effect as the basis , the new zoom optical system is designed to achieve motor control without mechanical movement, then the vision correction is designed by using liquid lens, such as the correction of myopia and hyperopia, which can automatically identify the eyes degrees of myopia and hyperopia, avoid frequent replacement lens steps when optometry is done for eyes.

Experimental demonstration of hybrid imaging for miniaturization of an optical zoom lens with a single moving element

We experimentally demonstrate a miniaturized zoom lens with a single moving element based on the concepts and analysis described in Opt. Express 17, 6118 (2009). We show that the implementation of either a cubic or a generalized cubic phase-modulation function makes miniaturization possible in addition to providing extended-depth-of-field imaging. We present recovered images for zoom lenses employing both phase-modulation functions and conclude that the generalized-cubic-phase function yields higher image quality without the artifacts present for the pure-cubic-phase function.

Optimization of 350× optical zoom lens with diffractive optical element

Through researching and validating, a set of optical designs using a diffractive optical element (DOE) and optimization process has been derived in this paper. We put forward a set of theories to solve the numerous quality issues in imaging and applied it to an optical design. For an optical design to be successful, it must comply with the standards of the optical system. Optical designers must also take into consideration imaging quality, wherein the most influential aspects are chromatic aberration and monochromatic aberration. We complied with systemic standards such as effective focal length and total system length. Diffractive Optical Element, based on the theory of wave phase difference, takes advantage of negative Abbe number, which might significantly eliminate chromatic aberrations of optics. Following the advanced technology applied to micro lens and etching process, precisely made micro DOE element now is possible to be manufactured in a large number. A 350× zoom lens with DOE is demonstrated in the proposal. The results show that regardless of whether chromatic aberration is axial or longitudinal, issues concerning the optical lens's chromatic aberration could be significantly reduced.

Vision-Based Computing Approach and Modeling for Wireless Network

In this paper, we present a new approach to wireless network from vision based computing methods and modeling. In contrast to traditional laser/photo-diode based transceivers, our method relies on a standard chargecoupled device camera to segment bit patterns through optical image processing techniques. this paper, network packets are ‘transmitted’ via screen updates to an LCD display. In the preliminary experiments, a maximum continuous throughput of 52.0 kbps was demonstrated using a standard NTSC camera. T ransmissions over a distance of 30 ft (approximately 9m) were also achieved by employing an 183 optical zoom lens assembly. We prove that this approach provides not only a redundant, secure means for wireless communication, but also a medium for enabling networking through non-traditional devices, e.g., television monitors, widely available.

Optical design and extended multi-objective optimization of miniature L-type optics

In ordinary optical design and optimization, it is difficult to strike a balance between relative illuminance (RI) and the modulation transfer function (MTF); this is even more difficult for special fold optical zoom lenses. We propose a thinning L-type zoom lens design that exploits the reflecting and refracting surfaces that constitute a prismatic lens. However, in L-type designs, the lens RI is comparatively low compared with that in its coaxial counterparts. Attempts to improve the RI also cause MTF degradation. We propose a combination of the Taguchi method and principal component analysis to improve both the RI and MTF in L-type zoom systems. We analysed an orthogonal array L9 using the Taguchi method. The resulting experimental values of the orthogonal array L9 were used as inputs for principal component analysis to obtain the total point value. The total point value was then analysed by variance, revealing that the two most significant factors were (1) the semi-aperture of the front element and (2) the surface 7 to image length. Our proposed method increased the MTF and RI by 0.16% and 0.44%, respectively, in system wide-angle ends.

Systems, control models, and codec for collaborative observation of remote environments with an autonomous networked robotic camera

Networked robotic cameras are becoming popular in remote observation applications such as natural observation, surveillance, and distance learning. Equipped with a high optical zoom lens and agile pan-tilt mechanisms, a networked robotic camera can cover a large region with various resolutions. The optimal selection of camera control parameters for competing observation requests and the on-demand delivery of video content for various spatiotemporal queries are two challenges in the design of such autonomous systems. For camera control, we introduce memoryless and temporal frame selection models that effectively enable collaborative control of the camera based on the competing inputs from in-situ sensors and users. For content delivery, we design a patch-based motion panorama representation and coding/decoding algorithms (codec) to allow efficient storage and computation. We present system architecture, frame selection models, user interface, and codec algorithms. We have implemented the system and extensively tested our design in real world applications including natural observation, public surveillance, distance learning, and building construction monitoring. Experiment results show that our frame selection models are robust and effective and our on-demand content delivery codec can satisfy a variety of spatiotemporal queries efficiently in terms of computation time communications bandwidth.