Search

Gabor wavelets are applied to develop an unsupervised novelty method for defect detection and segmentation that is fully automatic and free of any adjustable parameter. The algorithm combines the Gabor analysis of the sample image with a statistical analysis of the wavelet coefficients corresponding to each detail. The statistical distribution of the coefficients corresponding to the defect-free background texture is calculated from the coefficient's distribution of the sample under inspection. Once the background texture features are estimated, a threshold is automatically fixed and applied to all the details, whose information is merged into a single binary output image in which the defect appears segmented from the background. The method is applicable to random, nonperiodic, and periodic textures. Since all the information to inspect a sample is obtained from the sample itself, the method is proof against heterogeneities between different samples of the material, in-plane positioning errors, scale variations, and lack of homogeneous illumination. Experimental results are presented. Some results are compared with other unsupervised methods designed for defect segmentation in periodic textures.

The problem to recognizing a uniform color object placed on a color background is studied. The recognition process, based on a multichannel correlation, is divided into two steps. First, the presence of the target is determined by using two phase only filters (POF) in each channel matched to the target on a black background, and to a color square with the target in black. The background color is obtained with a classical matched filter (CMF) matched to the latter signal. From the information provided by the three filters in each channel, it is possible to obtain the presence of the target and the character-background color combination. Some simulation results are given to show the performance of the method.

A multiplexed programmable diffractive lens, displayed on a pixelated liquid crystal device under broadband illumination, is proposed to compensate for the severe chromatic aberration that affects diffractive elements. The proposed lens is based on multiplexing a set of sublenses with a common focal length for different wavelengths. We consider different types of integration of the optical information (spatial only, temporal only and hybrid spatial-temporal) combined with a proper selection of the spectral bandwidth. The properties and limits of the achromatic programmable multiplexed lens are described. Experimental results are presented and discussed.

We propose a method of fabric surface imaging and processing so that information about wrinkles can be extracted and evaluated. We consider two images of the sample obtained under orthogonal lateral illumination and apply a joint Canny edge detector to integrate the information about wrinkles of both images. The smoothed and scaled perception of wrinkle edges with the viewing distance and its influence in the evaluation of the fabric appearance is simulated, analyzed and proposed for a more realistic assessment of a fabric.

We propose a compact technique for encryption-verification that relies on the following elements: multifactor encryption, which permits the simultaneous verification of up to four factors; distortion-invariant ID tag for remote identification; near infrared (NIR) writing and readout of the ID tag signal for invisible transmission; and optical processor, based on joint transform pattern recognition by optical correlation, for automatic verification of information. A highly-reliable security system is obtained by joining the advantages of all these elements for the first time. A novel NIR ID tag is designed and built by using commonly available materials. The very ID tag content cannot be visually perceived at naked eye; it cannot be either copied, scanned, or captured by any conventional device. Experimental results based on the NIR ID tag are shown. The satisfactory results obtained demonstrate a new insight into the applications of the compact and efficient technique for high-secure identification systems.

The automatic segmentation of flaws in woven fabrics is achieved by applying Fourier analysis to the image of the sample under inspection, without considering any reference image. No prior information about the fabric structure or the defect is required. The algorithm is based on the structural feature extraction of the weave repeat from the Fourier transform of the sample image. These features are used to define a set of multiresolution bandpass filters, adapted to the fabric structure, that operate in the Fourier domain. Inverse Fourier transformation, binarization, and merging of the information obtained at different scales lead to the output image that contains flaws segmented from the fabric background. The whole process is fully automatic and can be implemented either optically or electronically. Experimental results are presented and discussed for a variety of fabrics and defects.

A new optical method to obtain multifactor image encoding and authentication is proposed. The encoded complex-amplitude image function fulfills the general requirements of invisible content, extreme difficulty in copying or counterfeiting, and real-time automatic verification. This optical technique is attractive for high-security purposes that require multifactor reliable authentication. A demonstration using a combination of biometric images and key codes is provided. Retina images, which are very effective for authentication, are used as biometric signals. To the best of our knowledge, this is the first report on combined multiple signal encoding and simultaneous AND authentications for optical security reinforcement.

The camera capability to measure small color differences between sample pairs is evaluated by comparing the camera performance with a reference instrument. To this end, the appropriate working conditions are established, the camera spectral sensitivities and imaging noise are characterized, and the transformation to obtain a device independent representation of color is calculated considering two approaches: one, on the basis of the camera spectral sensitivity (CSS), and two, on the basis of the unified measure of goodness of the camera (UMG) that involves an imaging noise model. The camera performance is assessed from the measurement results of a large number of varied small color differences in the very pale and the dark grayish color regions, the involved uncertainty, the absolute discrepancy, and the relative discrepancy with respect to the reference instrument. In the experimental application, the three CCD camera SONY DX-9100P is assessed and compared with the spectroradiometer Photo Research PR-715 as reference instrument. The results reveal a high quality performance of the camera system, with absolute discrepancies in the estimation of color differences around the camera tolerances (CIELAB 0.5ΔE* ab or CIEDE2000 0.6 ΔE 00 ). The color uniformity in textile dying is evaluated by analyzing some pairs of extreme center fabric samples. Although the camera is more sensitive to the texture effects than the spectroradiometer, both instruments yield consistent and satisfactory Pass/Fail results.

A method to assess the discrimination capability of a camera to measure small color differences is proposed. The method helps to fix the working conditions of the camera and analyzes the reliability of the measurements through comparison with a reference instrument. Attention is paid to the camera’s performance in the nearly neutral region of color space. The color differences are calculated using the Commission Internationale de l’Eclairage L* a* b* (CIELAB) ΔEab* and CIE 2000 color-difference formula metrics. The Sony DX-9100P 3CCD camera results are very close to those obtained by the Photo Research PR-715 spectroradiometer. Their absolute discrepancy is lower than the suprathreshold of visual discrimination (0.887 CIELAB unit).

Fabrics that have superstructures of colored squares, bands, etc., superimposed upon the basic web structure can be advantageously analyzed by use of near-infrared (NIR) illumination and a conventional monochrome camera. The reduction in contrast of the superstructure signal in the NIR image facilitates inspection of the fabric's structure and defect segmentation. Underdetection and misdetection errors are noticeably reduced. This inspection takes advantage of the residual sensitivity of a monochrome camera, which can reach 1000 nm. The light source is an array of NIR LEDs emitting in a band to which the camera is still sensitive. NIR visual inspection can be performed by machines or by humans. In the latter case the observer looks at the NIR image of the fabric displayed on a TV monitor.

A Fourier-domain-based recognition technique is proposed for periodic and quasiperiodic pattern recognition. It is based on the angular correlation of the moduli of the sample and the reference Fourier spectra centered at the maximum central point. As in other correlation techniques, recognition is achieved when a high correlation peak is obtained, and this result occurs when the two spectra coincide. The angular correlation is a one-dimensional function of the rotation angle. The position of the correlation peak indicates the rotation angle between two similar patterns in the original images. Some optimizations for the discrete calculation of the Fourier-domain-based angular correlation are also proposed. Some applications of this technique to web inspection tasks, such as pattern recognition and classification, damaged web evaluation, and detection of defects, are presented and discussed.

A new technique for evaluating the point spread function of parallel hole collimators in scintillation cameras is studied. The collimator function is developed into a Fourier series and the intensity distribution in the detector plane for a point source is given by a mathematical expression that depends on the object position and on the collimator parameters. The septal penetration effect is considered. The technique is applied to obtain the general formulae for collimators with hexagonal holes and the PSF is evaluated.

A multichannel colour image recognition technique is developed. Classical matched filters and phase only filters are studied. The discrimination capabilities of these filters are compared by submitting the process to two different types of tests: objects with shape and colour variation and objects with colour variation only. For the latter objects the discrimination of a given pattern can only be achieved with the use of phase only filters.

Data presented in this paper show that there is no significant difference between plasma and serum vitam B12 activity when EDTA is used as the anticoagulant. By drawing 5 ml of blood into a tube containing EDTA, the whole blood and plasma B12 activity can be measured using Lactobacillus leichmannii for the assay as the test organism. Erythrocyte B12 levels can be obtained by difference after correcting for hematocrit. Sodium heparin appears to inhibit the growth of L. leichmannii.

An optical nonsymmetrical imaging system composed of two anamorphic spectrum analyzers in cascade is implemented. This system can provide an undistorted final image in spite of the geometrical distortion effects in the intermediate Fourier plane. The introduction of chromatic sector filters in this plane provides a real-time technique to pseudocolor encode the spatial frequency information of a black-and-white transparency. In this way, greater discrimination is achieved in the angular orientation of object details that generate the same spatial frequencies. Experimental pseudocolored images, obtained with a symmetrical system and a nonsymmetrical system, of a black-and-white transparency are shown.

A wavelength-multichannel correlation technique based on matched filtering is proposed to identify a colour object with a non uniform colour distribution. The filters are matched to the object which is illuminated with different wavelengths. This correlation gives the information of colour distribution in addition to other information usually obtained from image recognition. The theoretical study of this technique, numerical simulations and discussion are presented.

PURPOSE. The study evaluated—theoretically and experimentally—the longitudinal chromatic aberration (LCA) and through-focus energy efficiency (TF-EE) of diffractive–refractive bifocal intraocular lenses (2f-IOLs). METHODS. Four aspheric 2f-IOLs (Tecnis þ4.00 diopter [D] ZMA00, þ2.75 D ZKB00, and AcrySof þ4.0 D SN6AD3, þ2.5 D SV25T0) of same base power 30 D, but different design, additional (add) power, and different material, were tested in vitro in terms of TF-EE when illuminated by 3 red (kR ¼ 625 nm), green (kG ¼ 530 nm), and blue (kB ¼ 455 nm) lights. The LCA affecting the distance and near foci was derived theoretically and measured experimentally from the contributions of the IOLs’ refractive and diffractive powers. Longitudinal chromatic aberration was evaluated in a pseudophakic schematic eye. RESULTS. The distance focus of all 2f-IOLs showed lower energy efficiency (EE) for the blue than for the red light. AcrySof IOLs showed the largest amount of positive LCA in the distance focus that, combined with corneal LCA, would increase the resulting distance LCA in a pseudophakic eye. The near focus of all 2f-IOLs showed higher EE for the blue than for the red light. Better compensation for the LCA of a pseudophakic eye at near focus is obtained with Tecnis than with AcrySof 2f-IOLs. CONCLUSIONS. The energy distribution between the foci of diffractive 2f-IOLs depends on the lens design, the illumination wavelength, and to a lesser extent, the add power. In distance vision, 2f-IOLs’ refractive base power increases the positive LCA of prior ocular media, and the resulting LCA may even surpass the natural LCA of human eye. In near vision, however, the achromatizing effect of diffractive 2f-IOLs may compensate, in part, the natural eye’s LCA

The multifactor optical encryption authentication method [Opt. Lett., 31 721-3 (2006)] reinforces optical security by allowing the simultaneous authentication of up to four factors. In this work, the photon-counting imaging technique is applied to the multifactor encrypted function so that a sparse phase-only distribution is generated for the encrypted data. The integration of both techniques permits an increased capacity for signal hiding with simultaneous data reduction for better fulfilling the general requirements of protection, storage and transmission. Cryptanalysis of the proposed method is carried out in terms of chosen-plaintext and chosen-ciphertext attacks. Although the multifactor authentication process is not substantially altered by those attacks, its integration with the photon-counting imaging technique prevents from possible partial disclosure of any encrypted factor, thus increasing the security level of the overall process. Numerical experiments and results are provided and discussed.

In this work, we use a novel multifactor encryption‐authentication technique that reinforces optical security by allowing the simultaneous AND‐verification of more than one primary image. This optical technique is attractive for high‐security purposes that require multifactor reliable authentication. In the example analysed in this work, four reference primary images are scrambled together in the encrypted multifactor distribution. The encrypted multifactor function is distributed in an identification (ID) tag to allow remote readout of the ciphered information. A distortion‐invariant ID tag is used so that the verification system is able to detect and identify the information included in the tag even when it is captured rotated or at a varying distance. To make the security system even more reliable, we combine data from visible and near infrared (NIR) spectral bands, without increasing unnecessarily the system complexity. The diversification of sources from which data are gathered adds difficulties to p...

We propose two methods of fabric surface imaging and processing so that the information of wrinkles can be extracted and evaluated. In the first method, we consider fringe projection and Fourier transform profilometry. In the second method we consider two images of the same sample obtained under different lateral illumination and apply a joint edge detector to integrate the information about wrinkles from both of them. The smoothed perception of wrinkles with distance and its influence in the evaluation of the fabric appearance is also studied.

As a result of modern technological advances, cataract surgery can be seen as not only a rehabilitative operation, but a customized procedure to compensate for important sources of image degradation in the visual system of a patient, such as defocus and some aberrations. With the development of new materials, instruments and surgical techniques in ophthalmology, great progress has been achieved in the imaging capability of a pseudophakic eye implanted with an intraocular lens (IOL). From the very beginning, optical design has played an essential role in this progress. New IOL designs need, on the one hand, theoretical eye models able to predict optical imaging performance and on the other hand, testing methods, verification through in vitro and in vivo measurements, and clinical validation. The implant of an IOL requires a precise biometry of the eye, a prior calculation from physiological data, and an accurate position inside the eye. Otherwise, the effects of IOL calculation errors or misplacements degrade the image very quickly. The incorporation of wavefront aberrometry into clinical ophthalmology practice has motivated new designs of IOLs to compensate for high order aberrations in some extent. Thus, for instance, IOLs with an aspheric design have the potential to improve optical performance and contrast sensitivity by reducing the positive spherical aberration of human cornea. Monofocal IOLs cause a complete loss of accommodation that requires further correction for either distance or near vision. Multifocal IOLs address this limitation using the principle of simultaneous vision. Some multifocal IOLs include a diffractive zone that covers the aperture in part or totally. Reduced image contrast and undesired visual phenomena, such as halos and glare, have been associated to the performance of multifocal IOLs. Based on a different principle, accommodating IOLs rely on the effort of the ciliary body to increase the effective power of the optical system of the eye in near vision. Finally, we present a theoretical approach that considers the modification of less conventional ocular parameters to compensate for possible refractive errors after the IOL implant.

The imaging characteristics of programmable lenses generated by twist‐nematic liquid crystal pixelated displays are determined from the technical specifications of a commercial modulator. We calculate the ranges of power and aperture of the feasible lenses reproduced by the modulator. Simulated and experimental point spread functions (PSF) are obtained to evaluate the programmed lens behaviour for different technical constraints. Imaging features of programmable multilenses are compared for two different configurations.

A good and complete calibration is the most important step in the electrically addressed spatial light modulator (SLM) initialization. It is clear that the quality and effectiveness of the optical component addressed to the SLM strongly depends on the knowledge of the device response. In fact, the signal must be modified before addressing it to the SLM to compensate for the distortions internally introduced by the device and hence, to eventually reproduce the optical component with the desired performance. In this work we deal with the spatial calibration of reflective zero‐twist liquid‐crystal on silicon (LCoS) SLM by testing the aperture of the device to characterize the inherent phase distortion. The inherent distortion of the reflective LCoS SLM may need not only the compensation for the backplane curvature but also for other possible non‐uniformities caused by thickness variations of the liquid crystal layer across the aperture. Firstly, we build a global Look‐Up Table (LUT) of phase modulation versu...

A method to study the relative influences of the collimator and the detector on the final image of a scintillation camera is proposed. The collimator response is studied by applying a technique based on the Fourier analysis for evaluating the point spread function (PSF) of parallel holes collimators. A mathematical expression for the PSF is obtained and from it the collimator MTF and plane sensitivity are evaluated. The scintillation camera response is obtained from the LSF measured experimentally. The detector response is obtained from these results. The method is applied to a Toshiba GCA 102 scintillation camera and from the results obtained the relative influences of the collimator and the detector on the image deterioration as a function of the object distance are discussed.

Joint-transform correlator (JTC) architecture presents some advantages, such as no requirement of interferometric recording of the phase distribution or complex conjugation of the key phase mask, in order to optically implement the well-known double random phase encryption (DRPE) method. In addition, a practical optical realization was proposed in a way that the whole information (primary image and two random phase masks) was easily introduced in the same input plane of the JTC system. However, poor image quality was obtained in the decryption stage. Cryptanalysis of JTC-based encryption systems demonstrated that they were vulnerable to certain intruder attacks, similarly to the original DRPE method. In this work, we review recent modifications of encryption algorithms based on JTC architecture that permit, on the one hand, to significantly increase the quality of the retrieved image after information decryption, and on the other hand, to achieve a high security level against a variety of system attacks. The modifications, which were firstly introduced in the Fourier-based JTC system, have been also adapted to be used in the Fresnel and Fractional Fourier domains as well as in the Gyrator domain. Nonlinear operations have been also introduced in multifactor encryption-authentication.

This work aims to build an algorithm to sharpen a color digital image based on S‐CIELAB extension. We use this method to segment the optic cup inside the optic disc, and the optic disc from the rest of the eye fundus image of glaucomatous eyes. S‐CIELAB involves a series of smoothing spatial filters in the opponent color space to approximate the contrast sensitivity functions of the human vision system. The filters are linear combinations of Gaussian masks. We combine these spatial filters with the Laplacian operator in each opponent channel to obtain the sharpened image. The resulting image is then subtracted from the original image in each opponent channel and back transformed to the device independent representation space (XYZ) to obtain the final sharpened image. The application developed to segment the optic cup and the optic disc is intended to give assistance in the cup to disc ratio estimation of glaucomatous eyes. Often the contours of both the optic cup and disc are faint and intersected by entangled veins that make it difficult to draw their silhouettes. The method is based on the information of color, the color differences between neighbor pixels and the geometry of the areas involved. It includes the spatial filtering proposed in the S‐CIELAB extension and uses the color image sharpening algorithm.

The optical quality of a set of IOLs (modeling set: one monofocal and two bifocals) was assessed through focus by the area under the modulation transfer function (MTFa) metric and related to the visual acuity (VA) defocus curves of pseudophakic patients implanted with said IOLs. A non-linear relationship between the MTFa and clinical VA was obtained with an asymptotic limit found to be the best VA achievable by the patients. Two mathematical fitting functions between clinical VA and MTFa were derived with high correlation coefficients (R-2 >= 0.85). They were applied to the MTFa obtained from a different set of IOLs with advanced designs (trial set: one extended range of vision -ERV-, one trifocal ERV and one trifocal apodized) to predict VA versus defocus of patients implanted with these IOLs. Differences between the calculated VA and the clinical VA for both fitting models were within the standard deviation of the clinical measurements in the range of -3.00 D to 0.00 D defocus. thus proving the suitability of the MTFa metric to predict clinical VA performance of new IOL designs. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Two proposals to compensate chromatic aberration of a programmable phase Fresnel lens displayed on a liquid crystal device and working under polychromatic illumination are presented. They are based on multiplexing a set of lenses, designed with a common focal length for different wavelengths, and a multicolor filter that makes each sublens work almost monochromatically. One proposal uses spatial multiplexing with mosaic aperture. The other uses a rotating scheme, a color filter against an array of lens sectors, and hybrid spatial-time integration. The central order focalization has a unique location at the focal plane. We have drastically reduced the transversal chromatic aberration of the polychromatic point spread function by properly adjusting the pupil size of each sublens. Depth of focus curves have been made coincident too for the selected wavelengths.

The integration of photon-counting imaging techniques and optical encryption systems can improve information authentication robustness against intruder attacks. Photon-counting imaging generates distributions with far fewer photons than conventional imaging and provides substantial bandwidth reduction by generating sparse encrypted data. We show that photon-limited encrypted distributions have sufficient information for successful decryption, authentication and signal retrieval. Additional compression of the encrypted distribution is applied by limiting the number of phase values used to reproduce the phase information of the complex-valued encrypted data. The validity of this technique—with and without phase compression—is probed through simulated experiments for two types of input images: alphanumerical signs and dithered natural scenes.

Two descriptions of the image of a web structure, a convolution model and an additive model, in both the spatial and frequency domains, are combined in the design of a method to extract information about the fabric structure by image analysis. The method allows the extraction of the conventional and also the minimal weave repeats, their size in terms of number of threads, their interlacing patterns, and their patterns of repetition. It is applicable to fabrics with square and nonsquare conventional weave repeat. Experimental results with images of real samples are presented and discussed.

Purpose: To compare objective image quality at distant, intermediate, and near foci with the corresponding visual acuity (VA) in patients symmetrically implanted with 5 different diffractive multifocal intraocular lenses (IOLs) (ReSTOR SV25T0, Tecnis ZKB00, Tecnis ZLB00, AT LISA 809, and AT LISA Tri 839MP) and a monofocal lens (Tecnis ZA9003) 3 months after cataract intervention. Methods: Objective image quality, measured as the area under the modulation transfer function curve (AMTF), was tested in vitro in an eye model. In addition, corrected distance visual acuity and distance-corrected intermediate and near visual acuities (DCIVA and DCNVA) were assessed in a group of 79 patients, randomly implanted with one of the lenses. Results: Image quality and VA at the distant focus was good for all lens designs, but was similarly compromised at the intermediate focus, where the best DCIVA corresponded to the low add ZKB00. At the near focus, the monofocal lens and the distance dominant SV25T0 had the worst AMTF values, with the ZLB00 presenting the best DCNVA. The relationship between AMTF and VA was found not to be linear, with VA being similarly good for AMTF values over a certain threshold. Conclusions: Visual acuity of pseudophakic patients reflected the optical quality of the specific IOL design within a certain range of measurements, beyond which maximum VA is limited by other ocular, optical, and neuropsychophysical factors.

Pixelated liquid crystal displays have been widely used as spatial light modulators to implement programmable diffractive optical elements (DOEs), particularly diffractive lenses. Many different applications of such components have been developed in information optics and optical processors that take advantage of their properties of great flexibility, easy and fast refreshment, and multiplexing capability in comparison with equivalent conventional refractive lenses. In this paper, we explore the application of programmable diffractive lenses displayed on the pixelated screen of a liquid crystal on silicon spatial light modulator (LCoS-SLM) to ophthalmic optics. In particular, we consider the use of programmable diffractive lenses for the visual compensation of some refractive errors (myopia, hyperopia). The theoretical principles of compensation are described and sketched using geometrical optics and paraxial ray tracing. A series of experiments with artificial eye in optical bench are conducted to analyze the compensation accuracy in terms of optical power and to compare the results with those obtained by means of conventional ophthalmic lenses. Practical considerations oriented to feasible applications are provided.

We propose a new optical method to obtain multifactor image encoding and authentication. The encoded complex‐amplitude image function fulfils the general requirements of invisible content, extreme difficulty in copying or counterfeiting and real‐time automatic verification. This paper describes both the encoded information contained in the ID tag and the optoelectronic processor that validates an identity on a basis of multiple signal recognition. This optical technique is attractive for high‐security purposes that require multifactor reliable authentication. A demonstration using a combination of biometric images, alphanumeric signatures and key codes is provided. Retina images, which are very effective for authentication, are used as biometric signals.

Retinal images are essential clinical resources for the diagnosis of retinopathy and many other ocular diseases. Because of improper acquisition conditions or inherent optical aberrations in the eye, the images are often degraded with blur. In many common cases, the blur varies across the field of view. Most image deblurring algorithms assume a space-invariant blur, which fails in the presence of space-variant (SV) blur. In this work, we propose an innovative strategy for the restoration of retinal images in which we consider the blur to be both unknown and SV. We model the blur by a linear operation interpreted as a convolution with a point-spread function (PSF) that changes with the position in the image. To achieve an artifact-free restoration, we propose a framework for a robust estimation of the SV PSF based on an eye-domain knowledge strategy. The restoration method was tested on artificially and naturally degraded retinal images. The results show an important enhancement, significant enough to leverage the images' clinical use. © 2014 Society of Photo-Optical Instrumentation Engineers. Ministerio de Educación, Cultura y Deporte Ministerio de Ciencia e Innovación, MICINN: TEC2010-09834-E, TEC2010-20307, DPI2009-08879 Grantová Agentura České Republiky: 13-29225S This research has been partly funded by the Spanish Ministerio de Ciencia e Innovación y Fondos FEDER (project DPI2009-08879) and projects TEC2010-09834-E and TEC2010-20307. Financial support was also provided by the Grant Agency of the Czech Republic under project 13-29225S. Authors are grateful to Juan Luís Fuentes from the Miguel Servet University Hospital (Zaragoza, Spain) for providing images. The first author also thanks the Spanish Ministerio de Educación for an FPU doctoral scholarship.

PURPOSE. To determine the energy distribution between the distance and near images formed in a model eye by spherical and aspheric apodized diffractive multifocal intraocular lenses (IOLs). METHODS. The IOL was inserted in a model eye with an artificial cornea with positive spherical aberration (SA) similar to that of the human cornea. The energy of the distance and near images, as a function of the pupil size, was experimentally obtained by image analysis. The level of SA on the IOL, which is pupil-size‐ dependent, was determined from simulations. The influence of the SA was deduced from results obtained in monofocal IOLs and by comparison of the experimentally obtained energy efficiency to theoretical results based solely on the diffractive profile of the IOL. RESULTS. In contrast with theoretical predictions, the energy efficiency of the distance image strongly decreased for large pupils, because of the high level of SA in the IOL. The decrease was smaller in the apodized diffractive multifocal lens with aspheric design. As for the near image, since the diffractive zone responsible for the formation of this image was the same in the spherical and aspheric lenses and the apertures involved were small (and so the level of SA), the results turned out to be similar for both designs. CONCLUSIONS. For large pupils, the energy efficiency of the distance image is strongly affected by the level of SA, although aspheric IOLs perform slightly better than their counterparts with a spherical design. For small pupils, there are no differences between the spherical and aspheric IOLs. (Invest Ophthalmol Vis Sci. 2011;52:5695‐5701) DOI:10.1167/iovs.10-7123

The light distribution among the far, intermediate and near foci of a new trifocal intraocular lens (IOL) is experimentally determined, as a function of the pupil size, from image analysis. The concept of focus energy efficiency is introduced because, in addition to the theoretical diffraction efficiency of the focus, it accounts for other factors that are naturally presented in the human eye such as the level of spherical aberration (SA) upon the IOL, light scattering at the diffractive steps or the depth of focus. The trifocal IOL is tested in-vitro in two eye models: the aberration-free ISO model, and a so called modified-ISO one that uses an artificial cornea with positive spherical SA in instead. The SA upon the IOL is measured with a Hartmann-Shack sensor and compared to the values of theoretical eye models. The results show, for large pupils, a notorious reduction of the energy efficiency of the far and near foci of the trifocal IOL due to two facts: the level of SA upon the IOL is larger than the value the lens is able to compensate for and there is significant light scattering at the diffractive steps. On the other hand, the energy efficiency of the intermediate focus for small pupils is enhanced by the contribution of the extended depth of focus of the near and far foci. Thus, while IOLs manufacturers tend to provide just the theoretical diffraction efficiency of the foci to show which would be the performance of the lens in terms of light distribution among the foci, our results put into evidence that this is better described by using the energy efficiency of the foci.