Adaptive optical zoom sensor.

In order to solve the problem that the distortion parameter of the zoom lens varies with focal length changes, a correction method for a zoom lens based on the minimum fitting error of a vanishing point geometric constraint is proposed. In light of a calibrated image with parallel line clusters without knowing the metric, the method can quickly correct the distortion of zoom lens in full focal length by the regression fitting of parameters. Firstly, based on the radial distortion division model, the functional relationship between the vanishing point and the radial distortion coefficient is established according to the geometric constraint of the vanishing point, and the first-order radial distortion coefficient of the camera is estimated by the Levenberg–Marquardt algorithm. And then, in terms of the principle of the deviation error minimization, the least squares can be used to fit the equation of straight line of the corrected points to optimize the center-of-distortion. Finally, the variation of distortion parameters with focal length is analyzed, the distortion parameter corresponding table between distortion parameters and focal length and the empirical formula of fitting are established. The results show that the root mean square error corrected by the fitting empirical formulas and the least squares support vector regression parameter corresponding table method for three different focal lengths are 1.16 pixels and 0.83 pixels, respectively. Moreover, those two ways are about 13% and 19% faster than Zhang’s method, respectively. By mapping this method to FPGA, the application effect of photographic UAV, security monitoring and other equipment requiring rapid response can be greatly improved.

We report the design and simulation results of an adaptive GRIN lens based on multi-electrode addressed blue phase liquid crystal. A high dielectric constant layer helps to smoothen out the horizontal electric field and reduce the operating voltage. Such a GRIN lens is insensitive to polarization while keeping parabolic phase profile as the focal length changes.

We report a solid microlens with self-positioning and tuned focal length using hydrophobic effects and electrowetting. We propose a novel fabrication method aligning the centers of electrodes and hydrophobic pattern simultaneously using one photomask. The proposed fabrication method offers a solid microlens by using a UV curable polymer. The focal length of the liquid microlens can be tuned to the targeted value by applying voltage to the electrodes before UV exposure solidification. Experiments showed that the tuning range of focal length by using electrowetting is 0.43 mm. It covers the initial focal length deviation 0.21 mm of the microlens. Seven samples showed an initial distribution from 1.78 to 1.58 mm in focal length. Their focal lengths are controlled by applying voltages from 1.77 to 1.82 mm. Volume contraction and following focal length change were evaluated, and optical losses are measured to be 0.92 and 0.49 dB in red and green, respectively. The measured surface roughness is 4 nm, which is applicable to optical micro-systems.

The design and manufacture of intraocular lenses (IOLs) depend upon the identification and quantitative preclinical evaluation of key optical properties and environmental parameters. The confocal laser method (CLM) is a new technique for measuring IOL optical properties, such as dioptric power, optical quality, refractive index, and geometrical parameters. In comparison to competing systems, the CLM utilizes a fiber-optic confocal laser design that significantly improves the resolution, accuracy, and repeatability of optical measurements. Here, we investigate the impact of changing the beam diameter on the CLM platform for the evaluation of IOL dioptric powers. Due to the Gaussian intensity profile of the CLM laser beam, the changes in focal length and dioptric power associated with changes in beam diameter are well within the tolerances specified in the ISO IOL standard. These results demonstrate some of the advanced potentials of the CLM toward more effectively and quantitatively evaluating IOL optical properties.

Dielectric elastomer actuators (DEA) are smart lightweight flexible materials integrating actuation, sensing, and structural functions. The field of DEAs has been progressing rapidly, with actuation strains of over 300% reported, and many application concepts demonstrated. However many DEAs are slow, exhibit large viscoelastic drift, and have short lifetimes, due principally to the use of acrylic elastomer membranes and carbon grease electrodes applied by hand. Here a DEA‐driven tunable lens, the world's fastest capable of holding a stable focal length, is presented. By using low‐loss silicone elastomers rather than acrylics, a settling time shorter than 175 μs is obtained for a 20% change in focal length. The silicone‐based lenses show a bandwidth 3 orders of magnitude higher compared to lenses of the same geometry fabricated from the acrylic elastomer. Stretchable electrodes, a carbon black and silicone composite, are precisely patterned by pad‐printing and subsequently cross‐linked, enabling strong adhesion to the elastomer and excellent resistance to abrasion. The lenses operate for over 400 million cycles without degradation, and show no change after more than two years of storage. This lens demonstrates the unmatched combination of strain, speed, and stability that DEAs can achieve, paving the way for complex fast soft machines.

Acquiring three-dimensional data from a pair of stereo images is called stereovision that has been studied by researchers for decades. However, most of the previous studies on this topic focused on establishment of stereovision parameter matching and made conclusions on the premise of fixed focus. With the rapid development of multimedia technology, varifocal digital cameras have been widely used in many robotic applications recently. In general, error in the depth estimate becomes bigger when the focus and aperture is unknown or not fixed. For that reason, a three-stage framework is proposed in this paper to modify the conventional stereovision model for improving accuracy of depth estimation. The first stage is to modify the computational model of conventional stereovision for varifocal cameras. Then, the spacing of depth interval in non-uniform spacing of discrete depth levels can be altered, in particular, it is unaffected by changes in focal length. Finally, with considering the affine transformation, we add the deformation coefficient into the modified stereovision model for correcting three-dimensional affine deformations. Experimental results demonstrated that the depth estimation from stereo images using the proposed scheme was more accurate than conventional method.

Controlled injection of fluid into a flexible lens chamber has previously produced tunable spherical lenses with spherical aberration problems. This paper presents a novel fluidic-controlled meniscus/biconvex lens system with relatively low distortion. The lens fabrication method is described and manufactured lenses are characterized for different processing parameters. Images captured through one of our lenses for a range of different pressures are presented. A change in focal length of five times (19.1-80.8 cm) is demonstrated. The focal length shows a quadratic relation to the applied pressure (0-5 kPa). For the simple prototype lens, distortion is less than 5% and relative illumination is above 0.74 by ZEMAX analysis.

We present a real‐time framework which allows interactive visualization of relativistic effects for time‐resolved light transport. We leverage data from two different sources: real‐world data acquired with an effective exposure time of less than 2 picoseconds, using an ultra‐fast imaging technique termed femto‐photography, and a transient renderer based on ray‐tracing. We explore the effects of time dilation, light aberration, frequency shift and radiance accumulation by modifying existing models of these relativistic effects to take into account the time‐resolved nature of light propagation. Unlike previous works, we do not impose limiting constraints in the visualization, allowing the virtual camera to explore freely a reconstructed 3D scene depicting dynamic illumination. Moreover, we consider not only linear motion, but also acceleration and rotation of the camera. We further introduce, for the first time, a pinhole camera model into our relativistic rendering framework, and account for subsequent changes in focal length and field of view as the camera moves through the scene.

The retinas of most young teleost larvae appear to lack rod photoreceptors, but rods proliferate rapidly in the latter part of the larval period. We used the optomotor response to measure scotopic thresholds throughout the larval period in red drum (Sciaenops ocellatus) and matched these values to measurements of visual morphology to investigate ontogenetic changes in the capabilities and mechanisms of scotopic vision. Scotopic thresholds decreased as larvae developed. Threshold intensity in the smallest larvae [3.4 mm total length (TL)] was 5000 times that of the largest larvae (20.8 mm TL). The ontogenetic change in thresholds was biphasic, with a faster decline for larvae larger than 8 mm total length. Corresponding changes in focal length, pupil area, densities of rods, cones, and ganglion cells, and summation ratios suggested that scotopic sensitivity of red drum larvae is mediated by cones at first. Later, when rods begin to proliferate, sensitivity is probably controlled by rod density and improved even more as multiple rods converge on individual ganglion cells. Results are discussed in relation to environmental conditions and ontogenetic habitat shifts in red drum.

In this work, we propose a theoretical model and validate it with finite element simulations for voltage-controlled hydrogel lenses made from soft materials. The model is built by examining the force equilibrium between the dielectric elastomer membrane and the hydrogel layer, allowing us to predict changes in focal length under applied voltage. Finite element simulations are used to corroborate the model, with results closely matching theoretical predictions. To ensure real-world applicability, the simulation data is also compared with experimental measurements. We observed slight deviations between the experimental lens shapes and the theoretical model due to gravitational effects on the hydrogel. To account for this, we developed a refined finite element model that accurately simulates the experimental conditions, showing strong alignment with both experimental data and theoretical predictions.

This paper describes a system that combines stereo vision with a 5-DOF robotic manipulator, to enable it to locate and reach for objects in an unstructured environment. Our system uses an affine stereo algorithm, a simple but robust approximation to the geometry of stereo vision, to estimate positions and surface orientations. It can be calibrated very easily with just four reference points. These are defined by the robot itself, moving the gripper to four known positions ( self-calibration ). The inevitable small errors are corrected by a feedback mechanism which implements image-based control of the gripper's position and orientation. Integral to this feedback mechanism is the use of affine active contour models which track the real-time motion of the gripper across the two images. Experiments show the system to be remarkably immune to unexpected translations and rotations of the cameras and changes of focal length — even after it has ‘calibrated’ itself.

Long-focus lenses are often called telephoto lenses, but this name should be restricted to those objectives which comprise a positive front component spaced apart from a negative rear component, such that the total length from front vertex to film plane is less than the focal length of the whole objective. In 1891, telephoto lenses were made by mounting a negative achromat behind a normal objective, making possible a very long focal length even with a relatively short camera bellows extension; however, the low aperture, field curvature and distortion were such that by 1905 manufacturers started making fixed-focus telephoto lenses with a moderate aperture and field. The simple thin-lens theory of the telephoto lens shows that the negative lens will be as weak as possible if it is situated midway between the positive lens and the focal plane. Telephoto lenses are currently popular for the longer focal lengths on single-lens reflex cameras. A survey of the principal types of telephoto lens is given, with examples of some actual lenses currently available.

A zoom objective lens for a multi-layer optical rec ording has been designed. A newly proposed optical power arrangement enables varying back focal length while focal length invariant by a linear movement of sin gle zooming component. The zoom lens is implemented into multi- layer and multi-bit holographic recording system em ploying 405 nm blue lasers. 1. INTRODUCTION Recently, multilayer micro holographic optical disc systems have been investigated to attain high capa city and high data transfer rate [1,2]. In the multilayer recordi ng, micro-holograms are recorded throughout the vol ume of recording material by changing the recording depth. For such multilayer recording systems, objective l ens accesses to multiple recording layers. The design of objecti ve lens needs to satisfy couple of constraints. Fir st, working distance, air spacing between objective lens and re cording disc, is unchanged while changing the recor ding layer. Numerical aperture (NA) must be an invariant for th e range of recording depth to equalize transverse s ize and modulation of index of refraction of the micro holo grams. Ideally, the number of moving elements shoul d be a minimum. Also, a linear relation between zooming of the element and recording depth is preferable. Typical way to design such optics is depicted in Fi g. 1. First, an intermediate image, a virtual or re al one, is formed by a movable zooming optics. Then, the inter mediate image is relayed to a final focal point ins ide a recording medium by a secondary optics consisting o f high NA objective elements. Moving the first opti cs along optical axis alters conjugate ratio between the int ermediate image and final image, therefore, the fin al image position also moves, which ends up with selection of writing depth. The approach is rather a simple one however we immediately notice several drawbacks of the approac h if we recall the design requirement for optical d ata storage applications. First, the system focal length varies as the writing depth changes. Consequently, NA va ries as selection of recording layers. As a result, a varia ble aperture and tuning of laser power is needed to equalize the transverse size and modulation of index of refracti on of the micro holograms. Second, the location of the final image nonlinearly moves with respect to the movement of t he zooming element. This would impose an additional requirement on actuators for selection of writing d epth. To overcome such issues, we propose an optica l power arrangement having constant focal length as well as linear movement of zooming element. Note that, eve n being able to implement such additional features, the pro posed optical power arrangement requires only one m oving component. Thus, our approach inherits the simple i mplementation of the conventional approach. Importa ntly, such a minimum optical power arrangement is possible onl y if specific combination of power is adopted for t he zooming optical component. In this paper, first analysis of the proposed power arrangement is described. Based on the power arrangement, we discuss design of all off-the-shelf write/read optics having a constant numerical aper ture (NA) of 0.4 for a range of writing depth of 0.2 mm. Design and implementation of multi-layer and multi-bit mic ro holographic recording system employing blue lasers will be addressed.

This paper presents the optical design and experimental demonstration of a compact, foveated, wide field-of-view (FOV) imaging system using two lenses and a liquid crystal spatial light modulator (SLM). The FOV of this simple doublet system is dramatically improved by the SLM, which can be programmed to correct all the geometrical aberrations at any particular field angle. The SLM creates a variation in the image quality across the entire FOV, with a diffraction-limited performance at the field angle of interest (similar to the foveated human vision). The region of interest can be changed dynamically, such that any area within the FOV of the system can be highly resolved within milliseconds. The wide FOV, compactness, and absence of moving parts make this system a good candidate for tracking and surveillance applications. We designed an f/7.7 system, with a 60° full FOV, and a 27 mm effective focal length. Only two lenses and a beam splitter cube were used along with a reflective SLM. The theoretical wavefront aberration coefficients were used to program the SLM, which was placed in the pupil plane of the system. A prototype was built and the system was experimentally demonstrated using monochromatic light and a CCD camera.

The characteristics of an optical system vary depending on wavelength and ambient temperature. Based on the thin-lens approximation, we investigate the conditions for stabilizing an optical system against wavelength and temperature variations at the same time. The conditions are applied to designing a laser scanning system consisting of two lenses. The change in the effective focal length of the scanning system against wavelength and temperature variations is very small, as expected.Keywords: Optical system design, Stabilized optical system, Laser scanning system, Achromatization, AthermalizationOCIS codes: (080.2740) Geometric optical design; (080.3630) Lenses; (220.3620) Lens system design