No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Design of a foveated wide-angle endoscopic lens
Abstract
Recent improvements in optics miniaturization have led to the development of multiple techniques in order to perform minimally invasive endoscopic procedures. Among them, the wide-angle lens is often used for its simplicity and ability to collect a large amount of information in one capture. We report the design and analysis of two versions of a wide-angle endoscope with a full field of view of 180 deg. The difference between the two designs resides in the direct control over distortion that was used in order to achieve foveated imaging. By doing so, the local magnification at the center of the image can be controlled during the design process, allowing for a better resolution in the center of the field of view. The design is also folded in order to address certain issue concerning the region of interest during an endoscopic procedure. © 2016 Society of Photo-Optical Instrumentation Engineers (SPIE).
... In recent years, several studies of wide field-of-view endoscopic lens design have been demonstrated. Dallaire and Thibault proposed a wide-angle endoscopic lens by introducing a foveated imaging technique [13]. Coral and Leblebici presented a miniaturized multicamera system inspired by insect eyes for wide field-of-view endoscopic imaging [14]. ...
... The f-number of the optical system is defined as the ratio of effective focal length and the entrance pupil diameter, EFL/EPD. The irradiance of the lens system is proportional to 1/ f -number 2 [21,22], which means that a lens with an f-number of 2.2 can obtain 2.53 times brighter images than the one with an f-number of 3.5 and 1.62 times brighter image than the other with f-number 2.8, the typical value of recently proposed endoscopic lens designs [13]. Hence, in identical dim lighting environment and physical dimensions of the lens, minimizing a lens' f-number is important to enhance its optical performance. ...
In the past few decades, video endoscopy has become one of the primary medical devices in diverse clinical fields for examination, treatment, and early disease diagnosis of the gastrointestinal tract. For an accurate diagnosis, an endoscopic camera offering bright and wide field-of-view images is required while maintaining its compact dimensions to enter the long, narrow, and dark tract inside of the body. Recent endoscopic lenses successfully provide wide fields-of-view and have compact sizes for the system; however, their f-numbers still remain at 2.8 or higher. Therefore, further improvement in f-numbers is required to compensate for the restricted illumination system of the endoscopic probe. Here, we present a low f-number endoscopic lens design while providing wide field-of-view and high-resolution imaging. The proposed lens system achieved a low f-number of 2.2 and a field-of-view of 140 deg. The modulation transfer function (MTF) is over 20% at 180 lp/mm, and relative illumination is more than 60% in the full field. Additionally, the proposed lens is designed for a 1/4” 5-megapixel complementary metal-oxide-semiconductor (CMOS) image sensor with a pixel size of 1.4 µm. This all-plastic lens design could help develop a high-performance disposable endoscope that prevents the risk of infection or cross-contamination with mass manufacture and low cost.
... There are three advantages of the present work compared with those of the optical endoscopes system and a single-aperture camera system. First, the proposed system uses the minimum number of components to achieve distinct Lilai Tang Ref. [10] Ref. [9] Ref. [18] Ref. [19] Result of our design images. Some existing designs use 5-piece or 7-piece lenses, which will greatly affect the relative illuminance of the system and lead to a significant loss of light energy. ...
... The 140 deg FOV is quite large, but still there is room to widen and, moreover, relative illumination could be further improved during the lens design process without the specific illumination system. In the wideangle lens design, the first element of the lens inevitably becomes larger in diameter, making it difficult to reduce the overall size of the lens [6]. The side-view optical design was developed by radial imaging through the cone mirror in the front of the lens [7]. ...
Capsule endoscopes require a high-quality imaging system in terms of the wide field of view (FOV), image brightness, and resolution to provide accurate diagnostic information. However, because of the wide-angle lens design, the first element of the lens inevitably becomes larger in diameter, making it difficult to reduce the overall size of the lens. In this study, the compact wide-angle lens for a capsule endoscope is reported. The proposed system allows the first element to be compact in diameter and increases image quality by utilizing all aspheric surfaces for optical aberration control. The specification of the proposed capsule endoscope lens shows the wide FOV of 160 deg, F-number 2.8, and total track length of 5 mm. In the overall FOV, relative illumination is still over 60%. To achieve a high image quality in the proposed system, the modulation transfer function is over 30% at 180 lp/mm for a ${1920} \times {1080}$ 1920 × 1080 1/6 inch CMOS image sensor in a pixel size of 1.4 µm.
... This concept is derived from the research on human vision system in which the resolution in IA is higher than that in the peripheral field. Except for the employment of a deformable mirror [21] and liquid crystal spatial light modulator [22] , a foveated imager that utilizes the aspherical surface is developed for dynamic imaging with high magnification based on local focal length modulation [23] . These locally magnifying systems are designed in visible spectrum and are considered in numerous applications, such as video monitoring and unmanned aerial vehicles [24] . ...
The requirements of surveillance for security and safety have been extremely growing over the years. Due to the outstanding capabilities of detection in the nighttime, infrared imaging has been developed for many applications, such as border defense, industrial production, and civil safety. In recent decades, a wide field of view with high resolution has been urgently called for novel surveillance in these applications. However, existing surveillance systems cannot meet the demands because of the low resolution and bulkiness. Here we present a dynamic foveated infrared imager for surveillance to capture local high-magnification images with a large field of view. Such a system is comprised of a peripheric imaging channel for monitoring the whole large field of view and a local high-magnification imaging channel for monitoring the key and/or suspected region. Notably, simulation experimental results indicate that image height has approximately 2 × magnification in foveated regions.
... Tilted optics based on Scheimpflug principle has been commonly applied for the correction of camera movements This [12]. Unfortunately 1 , this principle has not drawn considerable attention in the design of vision inspection systems. ...
... The ratio of the local magnification to the original one (ROM) was 1.4; however, the f-number was very large (nearly 16), the system volume was also large, and the deformable mirror enhanced the cost. Besides, based on distortion modulation, namely local focal length modulation, Hagen and Tkaczyk [18] and Samy and Gao [19] designed a foveated endoscopy and a foveated fisheye lens, respectively; Dallaire and Thibault [20] used the aspherical surface to modulate the local focal length of the thin beam in order to achieve different magnifications in different fields, whereas the ROM in the central field was only 1.18. Nevertheless, the local magnifying images in their systems are fixed, which is not suitable for object tracking. ...
Foveated imaging systems have the ability to capture local high-resolution or high-magnification images with wide field of view (FOV); thus, they have great potential for applications in the field of monitoring and remote sensing of unmanned aerial vehicles. Hence, foveated optical systems are in strong demand. However, the existing foveated imaging systems either are equipped with expensive modulators or require fixing the local high resolution imaging field, which is not suitable for mass production or object tracking in industrial applications. We propose a low-cost dynamic real-time foveated imaging system for extensive use in the listed applications. Specifically, we place a microlens behind the first intermediary image plane to modulate the local focal length, constructing a local high magnification imaging channel. One two-axis translation stage drives the microlens to scan in the plane perpendicular to the optical axis, resulting in dynamic local high magnifying imaging. Furthermore, the peripheral imaging channel and the foveated imaging channel focus on the same detector, and the post image fusion is unnecessary; the system consists of only a common aspherical lens and thus is very inexpensive. The experimental system has a focal length of 25 mm, a full FOV of 30°, and an entrance pupil diameter of 5 mm, while the local high magnifying imaging channel has a focal length of 35 mm and FOV of 15°. Experiment results show that the low-cost dynamic real-time foveated imaging system performs very well.
Le LETI possède un savoir-faire permettant de réaliser des micro modulateurs spatiaux de lumière (Spatial Light Modulators, SLMs) réalisés en technologie microélectronique sur silicium, ayant des très grandes résolutions et de très petits pas de pixels. Le LETI souhaite utiliser une technologie LCD particulière (la technologie IPS) dont d’une part les performances électro-optiques dans le domaine des micro-écrans ne sont pas connues mais d’autre part permet de garder des coûts réduits et de réduire le nombre d’étapes de fabrication. L’objectif de cette thèse est d’évaluer sur la base de simulations puis de réalisations techniques, les performances d’un micro-SLM IPS utilisé en modulation de phase et d’amplitude.Les recherches effectuées au cours de cette thèse portent sur 4 axes d’études. Le premier axe consiste à la recherche et à l’essai d’un logiciel spécifique (LCDMaster) permettant de simuler des cellules à cristaux liquides ainsi que des électrodes flottantes. Le second axe consiste à étudier en fonction du design du pixel et des différents modes d’alignements des cristaux liquides (Homogène, vertical et twisté) avec un pilotage de type IPS, les performances en modulation de phase. Les meilleurs résultats sont obtenus pour un alignement vertical fournissant un déphasage de 2 Pi. De plus, les performances d’un dispositif d’optique adaptative intégrant le SLM étudié ont été investiguées. Le troisième axe d’étude, consiste avec le même logiciel à investiguer sur les performances d’un SLM à cristaux liquide avec un pilotage de type IPS utilisant un alignement homogène en modulation d’amplitude (étude statique et dynamique). Cette étude permet également d’étudier les possibilités de diminution du temps de réponse de la cellule. Cette étude a aboutie à deux designs de SLM. Le premier design avec deux niveaux d’électrodes séparés par un isolant permettant de reproduire un effet type « cage de faraday ». La seconde a permis de diminuer de manière drastique le temps de réponse. Le quatrième axe de recherche consiste à tester des prototypes basés sur ces deux designs pour vérifier les performances obtenues en simulation grâce à un banc de caractérisation électro-optique. Des résultats concordants ont étés obtenus et de nouveaux types de SLM à pilotage IPS proposant un temps de rafraichissement rapides se rapprochant de l’état de l’art ont donc pu être désignés et caractérisés.
ResearchGate has not been able to resolve any references for this publication.