Anamorphic Distortion Research Articles

3D Metrology Using One Camera with Rotating Anamorphic Lenses.

In this paper, a novel 3D metrology method using one camera with rotating anamorphic lenses is presented based on the characteristics of double optical centers for anamorphic imaging. When the anamorphic lens rotates -90° around its optical axis, the 3D data of the measured object can be reconstructed from the two anamorphic images captured before and after the anamorphic rotation. The anamorphic lens imaging model and a polynomial anamorphic distortion model are firstly proposed. Then, a 3D reconstruction model using one camera with rotating anamorphic lenses is presented. Experiments were carried out to validate the proposed method and evaluate its measurement accuracy. Compared with stereo vision, the main advantage of the proposed 3D metrology approach is the simplicity of point matching, which makes it suitable for developing compact sensors for fast 3D measurements, such as car navigation applications.

High-precision anamorphic lens calibration with 3D and 2D calibration targets.

This paper presents a high-precision camera calibration approach for anamorphic lenses. The distortion model for anamorphic lenses is substantially more sophisticated than the distortion model for spherical lenses for the adaption of cylindrical lenses in anamorphic lens attachments. Based on the anamorphic aberration theory and numerical experiments, a polynomial type distortion model is provided for anamorphic lenses, with which high-precision camera calibrations can be achieved using 3D calibration targets. 3D calibration targets are typically limited in size, unable to encompass the whole imaging field of anamorphic lenses. The calibration results using 3D calibration targets tend to be unstable with the increased number of distortion coefficients in the anamorphic distortion model. Thus, after the anamorphic lenses have been calibrated with 3D calibration targets, they are recalibrated with 2D calibration targets that may fill the anamorphic lenses' field of view, resulting in more dependable and exact calibration results. Two anamorphic lenses are calibrated with high precision at the end the paper, which proves the effectiveness of the proposed method.

Simplified Aberration Analysis Method of Holographic Waveguide Combiner

Generally, the diffractive waveguide combiner and computer-generated hologram (CGH) technique have the potential to achieve compact head-mounted display (HMD) with a natural 3D display function. However, the diffractive waveguide combiner will degrade the image quality because of aberration. In order to resolve this issue, the complex analysis based on the ray-tracing method is necessary. Since the major aberration of the waveguide combiners is only astigmatism and anamorphic distortion, only these two aberrations were discussed in this paper. Furthermore, two common waveguide structures were discussed here. In total, four formulas were summarized to analyze aberration and anamorphic distortion in these two structures. Finally, the simplified formulas were verified with the commercial ray-tracing software Zemax. The calculated results of the proposed method match the simulation of Zemax software well. Therefore, the aberration of an arbitrary similar diffractive waveguide can be analyzed by the proposed method. This will make the designing process simpler and faster.

“The Theater of Real Life”: Godwin’s Mandeville and Milton’s A Masque Presented at Ludlow Castle

ABSTRACTThis essay explores John Milton’s influence on William Godwin’s 1817 novel Mandeville, notably in the many citations and allusions Mandeville draws from A Masque Presented at Ludlow Castle to describe the scope and significance of his interactions with others. But the influence is a kind of anamorphic distortion because Mandeville’s allusions to A Masque do not comprise a direct hermeneutic key with which to interpret the novel. Hence, while Mandeville constructs his narrative as a kind of Miltonic masque, he does so by transforming the characters of the novel from external agents into actors within his own mind. Mandeville’s “life-masque” stages his personal traumas, but it also resonates with Godwin’s concerns about the ongoing social, cultural, and political traumas embedded in English history that remain unresolved. Mandeville’s twisted version of Milton’s A Masque in the novel suggests that his rage endures and, like Comus himself, he lies in wait to re-emerge and re-engage his enemies. His facial scar—emblematic of both emotional and physical wounds—speaks to his inconsolable mourning and sustained menace.

Calibration of geometric distortion based on a reference sheet in oblique laser interferometry

When the form deviation of curved surface is measured with oblique laser interferometry, the collected interferogram is badly distorted, and cannot be positioned on the measured surface directly. The simulated object image is employed as a bridge to solve the problem. However, the geometric distortion is ignored in the current measurement, and prevents a high accuracy of the registration result between measured surface and interferogram. This paper focuses on calibrating the geometric distortion to improve the registration accuracy. Firstly, the object image of a reference sheet is captured in the same position and measurement system with measured curved surface. Then, the object image is compared with its simulated object image to establish the geometric distortion model. Next, the geometric distortion is integrated with image foreshortening and anamorphic distortion to simulate a better object image. Finally, the experimental results are given to show the more accurate registration result, and verify the feasibility and effectiveness of the proposed method.

Aurora Image Search With Saliency Deep Features

Although the convolutional neural networks have obtained amazing performance in the area of image search, most of the existing methods are applied for natural images collected via normal lens without anamorphic distortion. Actually, there are great amounts of images collected with a circular fisheye lens to obtain larger field-of-view (FOV), especially in the area of natural science study. This paper aims to present a novel image search method with saliency deep features for those images, especially the aurora images used in solar-terrestrial space research. Our method exploits the advanced Mask R-CNN framework to extract semantic features. To utilize the unique physical characteristics of aurora and focus on the most informative local regions, we present a saliency proposal network (SPN) to take place in the region proposal network (RPN). In our SPN, different from the conventional rectangular gridding way, the proposed anchors show spherical distortion determined by imaging principle and magnetic information. In addition, instead of the horizontal directions, our anchor boxes direct perpendicular to the physical magnetic meridian, and thus ensure them to include the auroral structures within minimum areas. We perform numerous experiments on the big aurora image dataset, and the results prove the superiority of the proposed method over the state-of-the-art methods on both search accuracy and efficiency.

The relationship between dioptric power and magnification in progressive addition lenses.

Non-uniform magnification (distortion) and dioptric blur are two major undesired optical defects affecting vision when looking through progressive addition lenses (PALs) and studying them is potentially very valuable for PAL design. The major purpose of this paper is to analyse the relationship between dioptric power and magnification and, additionally, to evaluate the expected values of distortion and dioptric blur typically present in PALs. This has not been carefully and rigorously analysed to date. We computed the local dioptric and magnification matrices (using a two-ray differential method) for different gaze directions in an archetypical model of a PAL. We used four different maps: scalar magnification and anamorphic distortion, to describe magnification, and mean power and astigmatism, to describe dioptric power. There is a good correlation between scalar magnification and mean power on the one hand, and anamorphic distortion and astigmatism on the other hand. Changes of 1 D in mean power are associated with variations in scalar magnification of around 3%. Also, 3% of anamorphic distortion is associated with increasing astigmatism up to 1 D. The directions of maximal power and maximal magnification are quite similar, though not equal (differences up to ± 1.5°). These directions strongly change from close to isotropic at the intermediate corridor to around 45° of oblique inclination for a few degrees of horizontal eye rotation. In typical PALs the level of distortion, which is unavoidably present when dioptric blurring appears, is small for usable vision zones (below 1 D of astigmatism). The combined analysis of dioptric power and magnification in PALs helps to understand their limitations as a visual aid. On the one hand, the potentials of including distortion magnitude as a target in the metric function being optimised in the PAL design are reduced; on the other hand, it seems worthwhile to explore adding the degradation orientation as an additional target.

Geometrical interpretation of dioptric blurring and magnification in ophthalmic lenses.

Blur and non-uniform magnification are two related undesired effects affecting vision when looking through eyeglasses. We propose a geometrical framework to study the relationship between both effects. Magnification and blur are locally characterized by dioptric and magnification matrices, respectively, which we compute here by using a novel two-ray numerical method. We propose a set of geometrical entities associated with the dioptric and magnification local matrices, which are analyzed in several examples. We prove that there is a strong correlation between such entities (e.g., astigmatism and anamorphic distortion), which, to a certain extent, is maintained even in highly asymmetric lenses. We also show the somewhat anti-intuitive result that the axis of maximal blurring is sometimes close to orthogonal to the axis of maximal distortion. The results provide useful clues for ophthalmic lens design.

Sharp and rectified imaging of plane test objects in diffractive grazing incidence interferometers

Fine-ground plane surfaces can be interferometrically tested in grazing incidence with laser illumination in the visible. Since the roughness of the surfaces is in the micrometer-range, the incidence angle of the probing wave front is very close to 90°, causing a strong anamorphic distortion of the length of the test sample on an imaging detector. In contrast to this the width of the sample remains undistorted in the image plane. Here, the case of a diffractive grazing incidence solution will be discussed. In particular, the rectification of the anamorphic distortion combined with sharp imaging of the whole length of the test sample will be described together with solutions for matching the illuminating and imaging beam cross section to the lateral extension of the sample.

Video-rate imaging of microcirculation with single-exposure oblique back-illumination microscopy

Oblique back-illumination microscopy (OBM) is a new technique for simultaneous, independent measurements of phase gradients and absorption in thick scattering tissues based on widefield imaging. To date, OBM has been used with sequential camera exposures, which reduces temporal resolution, and can produce motion artifacts in dynamic samples. Here, a variation of OBM that allows single-exposure operation with wavelength multiplexing and image splitting with a Wollaston prism is introduced. Asymmetric anamorphic distortion induced by the prism is characterized and corrected in real time using a graphics-processing unit. To demonstrate the capacity of single-exposure OBM to perform artifact-free imaging of blood flow, video-rate movies of microcirculation in ovo in the chorioallantoic membrane of the developing chick are presented. Imaging is performed with a high-resolution rigid Hopkins lens suitable for endoscopy.

Shield analysis and non-rigid match in positioning the actual interferogram on the tooth flank based on oblique incidence interferometry

When the oblique incidence interferometry is used to measure the form deviation of the tooth flank, because of the anamorphic distortion and image foreshortening, the collected interference fringe pattern (IFP) cannot be positioned on the tooth flank directly. Therefore a simulation tooth image (STI) is employed as a bridge to connect the collected IFP and the tooth flank. The exiting method is good enough to deal with the IFP of spur gear tooth flank, but it is inappropriate for the IFP of helical gear. This paper focuses on two improvements for positioning the IFP of helical gear on the tooth flank: (1) in the process of generating the STI, a mathematical model of helical tooth flank is proposed to judge the shielded situation of tooth flank; (2) in the process of matching the STI with the collected IFP, a non-rigid matching method is proposed to determine the relationship of the two images. The results of an experimental application are given to verify the feasibility and accuracy.

물 묻은 지문을 인식하기 위한 프리즘 광학계의 설계 및 실험적 고찰

본 연구는 지문 인식 시스템 중에서 프리즘을 이용한 광학계의 설계에 대한 것이다. 이는 프리즘, 렌즈, 그리고 CMOS 이미지 센서(혹은 CCD) 등으로 구성되어 있는 광학계이다. 종래의 프리즘을 이용한 지문인식 광학계에서는 지문에 물이 묻어 있는 경우에 영상의 품질이 현저히 저하되는 문제점이 있다. 이 경우에 프리즘의 굴절률을 높임으로써 영상의 품질을 충분히 높일 수 있었다. 또한 프리즘과 렌즈를 사용함으로 인하여 발생하는 비대칭 축소 왜곡(anamorphic distortion)과 상면의 지를 최소화되는 프리즘 꼭지각 <TEX>$\alpha$</TEX>를 제안한다. We propose a design and analysis of an optical system using a prism with a high enough refractive index for wet fingerprint identification. Important parameters including the tilting angle(<TEX>$\beta$</TEX>) of the <TEX>$1^{st}$</TEX> image plane, an anamorphic distortion, and a tilt of image plane are considered in terms of the apex angle of the prism(<TEX>$\alpha$</TEX>) and refractive index of the prism material. Our suggestion on refractive index and apex angle of the prism corroborates well with experimental results.

Three-dimensional particle imaging by wavefront sensing

We present two methods for three-dimensional particle metrology from a single two-dimensional view. The techniques are based on wavefront sensing where the three-dimensional location of a particle is encoded into a single image plane. The first technique is based on multiplanar imaging, and the second produces three-dimensional location information via anamorphic distortion of the recorded images. Preliminary results show that an uncertainty of 8 microm in depth can be obtained for low-particle density over a thin plane, and an uncertainty of 30 microm for higher particle density over a 10 mm deep volume.

Biblical scholarship in the age of bio-power: Albert Schweitzer and the degenerate physiology of the historical Jesus

Cinema Theory has for a long time been haunted by the question: is noir a genre of its own kind or a kind of anamorphic distortion affecting different genres? From the very beginning, noir was not limited to hard-boiled detective stories: reverberations of noir motifs are easily discernible in comedies ( Arsenic and Old Lace ), in westerns ( Pursued ), in political and social dramas ( All the King’s Men , The Lost Weekend ), etc. Do we have here a secondary impact of something that originally constitutes a genre of its own (the noir crime universe), or is the crime film only one of the possible fields of application of the noir logic? That is, is noir a predicate that entertains toward the crime universe the same relationship as toward comedy or western, a kind of logical operator introducing the same anamorphic distortion in every genre to which it is applied, so that finding its strongest application in the crime film turns on nothing but historical contingency (Žižek, Tarrying with the Negative: Kant, Hegel, and the Critique of Ideology , 1993, pp. 9-10)?

Line-of-sight treatment of distortions in computer synthesized holographic stereograms

An analysis of distortions in holographic stereograms is presented. Particular attention is paid to the effects of viewing position and the slit width on the shape of reconstructed images. The cause and effects of anamorphic distortion and image quantization are dealt with separately and guidlines for minimizing the latter are given.

The Shape of Screens to Come

The advent of compatible high-definition television {HDTV) will require specially prepared software to accommodate various image formats because excessive cropping and anamorphic distortion are an inevitable result of displaying programs in formats different from their intended design. An analysis of problem areas in film and video which suffer from excessive cropping is provided and related to the development of HDTV. The solutions offered also pertain to the development of a consumer widescreen television system, fully compatible with NTSC, which can serve as a testbed for the wide format of HDTV.

Zoom lens compensator for a cylindrical window in laser anemometer uses

In laser anemometer systems, the flow fields under study are typically enclosed by a window. Aberration of a flat window can be corrected by a shift of the object distance. A zooming correction lens eliminates the astigmatism caused by a thick cylindrical window and yields diffraction-limited performance for a monochromatic laser anemometer system. The effects of residual anamorphic distortion are discussed, and procedures for correcting these effects are presented.

Wollaston prism with large split angle

The image formation through a Wollaston prism with large split angle is studied. Formulas for the split angle, approximate calculations of aberrations, and ray tracings are used. The most important aberrations found are astigmatism and anamorphic distortion. Tilting the Wollaston with respect to the incident beam may reduce these aberrations, and if the orientation of the optical axis in the first element is varied it is possible to cancel one of the two aberrations for both images simultaneously, while the other one is substantially reduced. With an adequate adjustment of all the construction parameters the images become sharp enough to allow the use of large split angles (approximately 15 degrees).