Conceptual design of an on-board optical processor with components

The specification of components for a spacecraft on-board optical processor was investigated. A space oriented application of optical data processing and the investigation of certain aspects of optical correlators were examined. The investigation confirmed that real-time optical processing has made significant advances over the past few years, but that there are still critical components which will require further development for use in an on-board optical processor. The devices evaluated were the coherent light valve, the readout optical modulator, the liquid crystal modulator, and the image forming light modulator

High performances monolithic CMOS detectors for space applications

During the last 10 years, research about CMOS image sensors (also called APS -Active Pixel Sensors) has been intensively carried out, in order to offer an alternative to CCDs as image sensors. This is particularly the case for space applications as CMOS image sensors feature characteristics which are obviously of interest for flight hardware: parallel or semi-parallel architecture, on chip control and processing electronics, low power dissipation, high level ofradiation tolerance... Many image sensor companies, institutes and laboratories have demonstrated the compatibility of CMOS image sensors with consumer applications: micro-cameras, video-conferencing, digital-still cameras. And recent designs have shown that APS is getting closer to the CCD in terms ofperformance level. However, the large majority ofthe existing products do not offer the specific features which are required for many space applications. ASTRI1JM and SUPAERO/CIMI have decided to work together in view of developing CMOS image sensors dedicated to space business. After a brief presentation of the team organisation for space image sensor design and production, the latest results of a high performances 512x512 pixels CMOS device characterisation are presented with emphasis on the achieved electro-optical performance. Finally, the on going and short-term coming activities of the team are discussed

Response for light scattered in the ocular fundus from double-pass and Hartmann–Shack estimations

Double-pass (DP) and Hartmann--Shack (HS) are complementary techniques based on reflections of light in the ocular fundus that may be used to estimate the optical properties of the human eye. Under conventional data processing, both of these assessment modes provide information on aberrations. In addition, DP data contain the effects of scattering. In the ocular fundus, this phenomenon may arise from the interaction of light with not only the retina, but also deeper layers up to which certain wavelengths may penetrate. In this work, we estimate the response of the ocular fundus to incident light by fitting the deviations between DP and HS estimations using an exponential model. In measurements with negligible intraocular scattering, such differences may be related to the lateral spreading of light that occurs in the ocular fundus due to the diffusive properties of the media at the working wavelength. The proposed model was applied in young healthy eyes to evaluate the performance of scattering in such a population. Besides giving a parameter with information on the ocular fundus, the model contributes to the understanding of the differences between DP and HS estimations.Postprint (author's final draft

Pixel Crosstalk and Correlation with Modulation Transfer Function of CMOS Image Sensor

The Modulation Transfer Function is a common metric used to quantify image quality but inter-pixel crosstalk analysis is also of interest. Because of an important number of parameters influencing MTF, its analytical calculation and crosstalk predetermination are not an easy task for a CMOS image sensor. A dedicated test chip (using a technology optimized for imaging applications) has been developed in order to get both MTF data and influence of the various areas of the pixel to its own response and the one of its neighbors. In order to evaluate the contribution of pixel elementary patterns (particularly the in-pixel readout circuitry), several kernels of shielded pixels have been implemented with the central pixel locally unmasked. The results obtained with pixel kernels and direct MTF measurements, performed on the same chip at different wavelengths, are analyzed and compared in order to correlate them and draw conclusions that can be applied at the design level. Additional data resulting from spotscan measurements allow us to verify our hypothesis on different pixels

Spatial-frequency response of the limb infrared monitor of the stratosphere

Measurements from the Limb Infrared Monitor of the stratosphere (LIMS) are presented and discussed. From the LIMS design model data, the modulation transfer function (MTF) was calculated for the optical system, the detector field mask, the electronics, and the overall system for each channel. The signal output performance of the instrument was predicted from the system MTF data and model input radiance data for each channel. The MTF measurements made on the flight sensor confirmed the analytical results

Advanced electro-optical imaging techniques

The papers presented at the symposium are given which deal with the present state of sensors, as may be applicable to the Large Space Telescope (LST) program. Several aspects of sensors are covered including a discussion of the properties of photocathodes and the operational imaging camera tubes

A quantitative analysis of a self-emitting thermal IR scene simulation system

A quantitative evaluation is performed in which the imaging characteristics of a selfemitting thermal infrared scene simulation system are analyzed. The simulation system is comprised of an energy source (an Argon laser), optics, a spatial light modulator for image generation in the visible wavelength energy, and an transducer for conversion of the visible wavelength energy image to a thermal IR image. After construction of the simulation system, the performance of the simulation system and its components is analyzed by measurement of : (1) the Modulation Transfer Function, (2) the temporal response, (3) the maximum thermal contrast, and (4) the Noise Equivalent Delta Temperature. Additionally, an evaluation was made of the performance of the infrared imaging system used to view the simulation system output imagesby measurement of its Modulation Transfer Function and Noise Equivalent Delta Temperature. The optimum area of concentration for overall system improvement has been identified for future developmental work

Optical and visual characterization of multifocal contact lenses and multifocal intraocular lenses

Vision is presented and universally accepted as the most precious of the human senses.lt is structured in three main parts: the optical system {eye), the photo-sensor {eye's retina), and the data processor (brain). If one of them is affected by any disease or dysfunction, vision will be terrible or even nonexistent One of the most common dysfunction is presbyopia.lt i s an age-related disorder that is undergone by all the population s ince their mid-late-40s and it is consists in the loss of the ability to focus near objects (accommodation). A huge number of possible corrections of it can be easily found. On one hand, there are temporary corrections ,as progressive spectacle tenses or multifocal contact tenses. On the other hand, permanent corrections as multifocal i ntraocular lenses, multifocal cornea! ablation, accommodating intraocular tenses, monovision systems, or scleral modifications are also applied to correct presbyopia. Another age-related dysfunction is cataract. Cataract is the opacification of the crystalline fens and decreases the quality of the visual function. Consequently, it is one of the leading visual impairments in adults over 60 years old, affecting the half of the adults aged between 75-85 years old. The only possible solution far cataract is the extraction of the opacified fibers of the crystalline lens and the replacement of them with an intraocular lens by surgery. Due to the fact that all the patients affected by an age-related cataract are also affected by presbyopia it is totally understandable that a number of patients choose mulltifocal introcular lens to substitute their crystalline tenses .This way, only one surgery is needed to salve both age-related dysfunctions. Usually, young presbyopes choose a temporary correction as a first option to correct presbyopia. Some presbyopia corrections are based on the simultaneous vision principie, as, far example, multifocal contact or intraocular lenses. The optical design of these kind of lenses is very complex. Consequently, It is characterization is also difficult When these lenses were launched into the market, it was only possible to characterize optical quality before the implantation or the adaptation of them (characterization in vitro) and the visual quality after the surgery or the clinical adaptation was performed (characterization) .M. present and thanks to the technological advances, different new commercial instruments that are to perform characterization in vivo of the visual quality before the implantation or the adaptation of simultaneous vis ion tenses. They are based on the simulation of the vision that these tenses give to the implanted eye. Some experimental prototypes and commercial aberrometers or double­ pass systems have used to perform an optical quality characterization in vivo, but some issues have been reported. Taking into account all this information, the main goal of this thesis is the design and the assembly of a new open-field double-pass system with asymmetric focus that is suitable to characterize invivo optical quality in patients implanted or adapted with multifocal intraocular or contact lenses. In order to achieve this aim, different studies and processes were carried out Review of presbyopia corrections and the characterization of them (Clinical study about objective over-refraction wearing multifocal contact lenses); Verification of the suitability of one commerciat simulator (Clinical study with the commercial simulator VirtlOL (10lens S.l.)); Design and assembly of the double-pass system with asymmetric focus (Opto-mechanical design/ Validation of all the elements included in the system/ Optical validation of the system); Programming of the softwares to manage the system; Validation of the new prototype (Two clinical studies characterizing eyes implanted with multifocal introcular tenses by using the new system were done).La visió és entesa i, universalment acceptada, com el sentit humà més valorat .Aquesta esta estructurada en tres parts principals: el sistema òptic (l'ull), el fot-sensor (la retina ocular) iel processador (el cervell). Si una d'aquestes parts es veu afectada per una disfunció o malaltia, la visió pot arribar a ser de molt baixa qualitat i, fins hi tot, inexistent Una de les disfuncions més comunes és la presbícia. La presbícia és una disfunció lligada a l'edat que pateix tota lla població a partir dels 40 anys, aproximadament. Consisteix en la pèrdua de la capacitat d'enfocar objectes propers (acomodació). Actualment, es troba un ampli nombre de possibles correccions. Per una banda, tenim les correccions temporals, com ulleres o lents de contacte progressives, i, per l'altre, correccions permanents, com lents intraoculars multifocals , ablacions corneals multifocals, lents intraoculars acomodatives, sistemes de monovisió, o modificacions esclerals, entre altres. Una altre disfunció associada a l'edat és la cataracta, la qual crea la opacificació del cristal·lí impedint una visió nítida. Conseqüentment, la cataracta és una de la deficiències visuals més estesa a partir dels 60 anys, afectant a la meitat de la població entre els 75 i els 85 anys . La única solució per eliminar les cataractes és eliminant les fibres opacificades i substituir-les per una lent intraocular quirúrgicament. Donat que tots els pacients amb cataractes són, a la vegada, prèsbites, està justificat que un nombre de pacients decideixi implantar-se lents intraoculars multifocals per substituir el seu cristal·lí. D'aquesta manera es solucionen dues degeneracions associades a l'edat en una sola cirurgia. Els joves prèsbites acostumen a optar per correccions prèsbites temporals, mentre que molts dels prèsbites amb cataractes opten per solucions permanents. Algunes de les correccions de la presbícia, com les lents de contacte o intraoculars multifocals , estan basades en el principi de visió simultània. Els dissenys òptics d'aquest tipus de lents són molt complexos, cosa que fa que la seva caracterització sigui molt complicada. Quan aquestes lents van aparèixer al mercat, només era possible caracteritzar-les òpticament abans de la seva implantació o adaptació de manera in vitro, i de caracteritzar-les visualment després de la seva adaptació o implantació de manera in vivo. Actualment, i gracies a tots els avenços tecnològics, diferents instruments clínics han estat desenvolupats per realitzar mesures de les qualitats visuals abans de la seva implantació. Tots ells, es basen en simular-li al pacient la visió que tindria després de ser implantat. Per un altre cantó, alguns prototips experimentals iaberrometres o sistemes de doble-pas comercials han estat utilitzats per dur a terme la caracterització de la qualitat in vim en pacients implantats o adaptats amb sistemes multifocals, pero diferents problemes han estat plantejats. Tenint en compte tota aquesta informació, el principal objectiu d'aquesta tesi ha estat la de dissenyar i muntar un nou sistema de doble-pas d'enfocament asimètric de camp obert que fos capaç de fer una caracterització de la qualitat òptica in vivo de pacients implantats o adaptats amb lents de contacte o intraoculars multifocals. I per arribar a aquest objectiu, s'han dut a terme els següents passos: Revisió de les correccions per a la presbícia i caracterització d'elles (Estudi clínic de la sobre-refracció objectiva de pacients adaptats amb lents de contacte multifocals); Validació de la capacitat de mesura d'un simulador comercial (Estudi clínic amb el simulador comercial VirtlOL (1OLens S.L); Disseny i muntatge del sistema de doble-pas amb enfocament asimètric (Disseny opto-mecànic/ Validació de tots els components del sistema/ Validació òptica del sistema); Programació dels programes informàtics que gestionen el sistema i processenPostprint (published version

Optical and visual characterization of multifocal contact lenses and multifocal intraocular lenses

Vision is presented and universally accepted as the most precious of the human senses.lt is structured in three main parts: the optical system {eye), the photo-sensor {eye's retina), and the data processor (brain). If one of them is affected by any disease or dysfunction, vision will be terrible or even nonexistent One of the most common dysfunction is presbyopia.lt i s an age-related disorder that is undergone by all the population s ince their mid-late-40s and it is consists in the loss of the ability to focus near objects (accommodation). A huge number of possible corrections of it can be easily found. On one hand, there are temporary corrections ,as progressive spectacle tenses or multifocal contact tenses. On the other hand, permanent corrections as multifocal i ntraocular lenses, multifocal cornea! ablation, accommodating intraocular tenses, monovision systems, or scleral modifications are also applied to correct presbyopia. Another age-related dysfunction is cataract. Cataract is the opacification of the crystalline fens and decreases the quality of the visual function. Consequently, it is one of the leading visual impairments in adults over 60 years old, affecting the half of the adults aged between 75-85 years old. The only possible solution far cataract is the extraction of the opacified fibers of the crystalline lens and the replacement of them with an intraocular lens by surgery. Due to the fact that all the patients affected by an age-related cataract are also affected by presbyopia it is totally understandable that a number of patients choose mulltifocal introcular lens to substitute their crystalline tenses .This way, only one surgery is needed to salve both age-related dysfunctions. Usually, young presbyopes choose a temporary correction as a first option to correct presbyopia. Some presbyopia corrections are based on the simultaneous vision principie, as, far example, multifocal contact or intraocular lenses. The optical design of these kind of lenses is very complex. Consequently, It is characterization is also difficult When these lenses were launched into the market, it was only possible to characterize optical quality before the implantation or the adaptation of them (characterization in vitro) and the visual quality after the surgery or the clinical adaptation was performed (characterization) .M. present and thanks to the technological advances, different new commercial instruments that are to perform characterization in vivo of the visual quality before the implantation or the adaptation of simultaneous vis ion tenses. They are based on the simulation of the vision that these tenses give to the implanted eye. Some experimental prototypes and commercial aberrometers or double­ pass systems have used to perform an optical quality characterization in vivo, but some issues have been reported. Taking into account all this information, the main goal of this thesis is the design and the assembly of a new open-field double-pass system with asymmetric focus that is suitable to characterize invivo optical quality in patients implanted or adapted with multifocal intraocular or contact lenses. In order to achieve this aim, different studies and processes were carried out Review of presbyopia corrections and the characterization of them (Clinical study about objective over-refraction wearing multifocal contact lenses); Verification of the suitability of one commerciat simulator (Clinical study with the commercial simulator VirtlOL (10lens S.l.)); Design and assembly of the double-pass system with asymmetric focus (Opto-mechanical design/ Validation of all the elements included in the system/ Optical validation of the system); Programming of the softwares to manage the system; Validation of the new prototype (Two clinical studies characterizing eyes implanted with multifocal introcular tenses by using the new system were done).La visió és entesa i, universalment acceptada, com el sentit humà més valorat .Aquesta esta estructurada en tres parts principals: el sistema òptic (l'ull), el fot-sensor (la retina ocular) iel processador (el cervell). Si una d'aquestes parts es veu afectada per una disfunció o malaltia, la visió pot arribar a ser de molt baixa qualitat i, fins hi tot, inexistent Una de les disfuncions més comunes és la presbícia. La presbícia és una disfunció lligada a l'edat que pateix tota lla població a partir dels 40 anys, aproximadament. Consisteix en la pèrdua de la capacitat d'enfocar objectes propers (acomodació). Actualment, es troba un ampli nombre de possibles correccions. Per una banda, tenim les correccions temporals, com ulleres o lents de contacte progressives, i, per l'altre, correccions permanents, com lents intraoculars multifocals , ablacions corneals multifocals, lents intraoculars acomodatives, sistemes de monovisió, o modificacions esclerals, entre altres. Una altre disfunció associada a l'edat és la cataracta, la qual crea la opacificació del cristal·lí impedint una visió nítida. Conseqüentment, la cataracta és una de la deficiències visuals més estesa a partir dels 60 anys, afectant a la meitat de la població entre els 75 i els 85 anys . La única solució per eliminar les cataractes és eliminant les fibres opacificades i substituir-les per una lent intraocular quirúrgicament. Donat que tots els pacients amb cataractes són, a la vegada, prèsbites, està justificat que un nombre de pacients decideixi implantar-se lents intraoculars multifocals per substituir el seu cristal·lí. D'aquesta manera es solucionen dues degeneracions associades a l'edat en una sola cirurgia. Els joves prèsbites acostumen a optar per correccions prèsbites temporals, mentre que molts dels prèsbites amb cataractes opten per solucions permanents. Algunes de les correccions de la presbícia, com les lents de contacte o intraoculars multifocals , estan basades en el principi de visió simultània. Els dissenys òptics d'aquest tipus de lents són molt complexos, cosa que fa que la seva caracterització sigui molt complicada. Quan aquestes lents van aparèixer al mercat, només era possible caracteritzar-les òpticament abans de la seva implantació o adaptació de manera in vitro, i de caracteritzar-les visualment després de la seva adaptació o implantació de manera in vivo. Actualment, i gracies a tots els avenços tecnològics, diferents instruments clínics han estat desenvolupats per realitzar mesures de les qualitats visuals abans de la seva implantació. Tots ells, es basen en simular-li al pacient la visió que tindria després de ser implantat. Per un altre cantó, alguns prototips experimentals iaberrometres o sistemes de doble-pas comercials han estat utilitzats per dur a terme la caracterització de la qualitat in vim en pacients implantats o adaptats amb sistemes multifocals, pero diferents problemes han estat plantejats. Tenint en compte tota aquesta informació, el principal objectiu d'aquesta tesi ha estat la de dissenyar i muntar un nou sistema de doble-pas d'enfocament asimètric de camp obert que fos capaç de fer una caracterització de la qualitat òptica in vivo de pacients implantats o adaptats amb lents de contacte o intraoculars multifocals. I per arribar a aquest objectiu, s'han dut a terme els següents passos: Revisió de les correccions per a la presbícia i caracterització d'elles (Estudi clínic de la sobre-refracció objectiva de pacients adaptats amb lents de contacte multifocals); Validació de la capacitat de mesura d'un simulador comercial (Estudi clínic amb el simulador comercial VirtlOL (1OLens S.L); Disseny i muntatge del sistema de doble-pas amb enfocament asimètric (Disseny opto-mecànic/ Validació de tots els components del sistema/ Validació òptica del sistema); Programació dels programes informàtics que gestionen el sistema i processe

Speckle reduction in double-pass retinal images using variable-focus lenses

Speckle arises in double-pass images when coherent light is scattered by the retina. Since this noise degrades the images that are used to characterize the eye, there is special attention in reducing speckle when working with instruments based on retina reflections. In this work, we present a method for speckle reduction in double-pass retinal images by producing minor periodic variations in the vergence of the beam entering the eye with a variable-focus lens during image recording. Measurements in an artificial and a real eye following the implementation of the method corroborate the speckle reduction.Postprint (published version