Modeling and applications of the focus cue in conventional digital cameras

El enfoque en cámaras digitales juega un papel fundamental tanto en la calidad de la imagen como en la percepción del entorno. Esta tesis estudia el enfoque en cámaras digitales convencionales, tales como cámaras de móviles, fotográficas, webcams y similares. Una revisión rigurosa de los conceptos teóricos detras del enfoque en cámaras convencionales muestra que, a pasar de su utilidad, el modelo clásico del thin lens presenta muchas limitaciones para aplicación en diferentes problemas relacionados con el foco. En esta tesis, el focus profile es propuesto como una alternativa a conceptos clásicos como la profundidad de campo. Los nuevos conceptos introducidos en esta tesis son aplicados a diferentes problemas relacionados con el foco, tales como la adquisición eficiente de imágenes, estimación de profundidad, integración de elementos perceptuales y fusión de imágenes. Los resultados experimentales muestran la aplicación exitosa de los modelos propuestos.The focus of digital cameras plays a fundamental role in both the quality of the acquired images and the perception of the imaged scene. This thesis studies the focus cue in conventional cameras with focus control, such as cellphone cameras, photography cameras, webcams and the like. A deep review of the theoretical concepts behind focus in conventional cameras reveals that, despite its usefulness, the widely known thin lens model has several limitations for solving different focus-related problems in computer vision. In order to overcome these limitations, the focus profile model is introduced as an alternative to classic concepts, such as the near and far limits of the depth-of-field. The new concepts introduced in this dissertation are exploited for solving diverse focus-related problems, such as efficient image capture, depth estimation, visual cue integration and image fusion. The results obtained through an exhaustive experimental validation demonstrate the applicability of the proposed models

Body dissatisfaction and sexual distress: testing a mediation model with pregnant and non-pregnant partnered women

Orientação: Patrícia Pascoalmanidades e Tecnologias – Escola de Psicologia e Ciências da Vida 5 Resumo Introdução: A gravidez é caracterizada por mudanças físicas, hormonais e psicológicas que podem afetar a sua sexualidade daquelas que estão em um relacionamento diádico, afetando a relação sexual do casal. Objetivo: Comparar uma amostra de mulheres grávidas e não grávidas e estabelecer se as mulheres grávidas apresentam níveis mais baixos, iguais ou superiores de insatisfação corporal, distração cognitiva durante a atividade sexual e distress sexual sobre a função sexual em comparação com mulheres não gravidas e testar um modelo explicativo moderado de mediação do impacto da insatisfação corporal em sofrimento sexual, usando a gravidez como moderador. Métodos: O presente estudo teve a participação de 44 mulheres não grávidas e 43 mulheres grávidas da população geral portuguesa (n = 87), com idade compreendidas entre os 25 e 40 anos que se autoidentificam como heterossexuais e estão envolvidas em uma díada exclusiva e comprometida, e que completaram uma pesquisa on-line. Principais medidas de estudo: as mulheres completaram a medida geral validada da insatisfação corporal (Escala Global de Insatisfação Corporal), distress sexual (procedimento retirado da Pesquisa Nacional de Atitudes Sexuais e Estilo de Vida), distração cognitiva baseada na aparência do corpo durante a atividade sexual (Escala de Distração de Aparência Corporal). Resultados: Distração cognitiva com a aparência do corpo intervém na associação entre insatisfação com o corpo e dificuldades sexuais. Além disso, o efeito da insatisfação corporal sobre o distress sexual, na presença da variável mediadora, foi reduzido a não significância, revelando assim um efeito de mediação completo da distração cognitiva com base na aparência do corpo na associação entre insatisfação corporal e angústia sexual. Conclusão: Este estudo avança nossa compreensão da sexualidade durante a gravidez, avaliando o distress sexual. Como tal, os dados fornecem uma imagem mais precisa sobre o distress sexual que as mulheres experienciam durante a gravidez em relação à insatisfação corporal.Introduction: Pregnancy is characterized by physical, hormonal, and psychological changes that can affect women’s sexuality and for those who are in a dyadic relationship, it also affects couple’s sexual relationship. Aim: Compare a sample of pregnant and non-pregnant women and establish if pregnant women have lower, equal or higher levels of body dissatisfaction, body appearance cognitive distraction during sexual activity and sexual distress about their sexual function compared to non-pregnant women and to test a moderated mediation explanatory model of the impact of body dissatisfaction on sexual distress, using pregnancy as the moderator. Methods: The present study had the participation of 44 non-pregnant women and 43 pregnant women from the general Portuguese population (n = 87), aged between 25 and 40 years who self-identify as heterosexual and are involved in an exclusive and committed dyadic relationship, completed an online survey. Main Outcome Measures: Women completed validated general measure of body dissatisfaction (Global Body Dissatisfaction Scale), sexual distress (procedure taken from National Survey of Sexual Attitudes and Lifestyles), cognitive distraction based on body appearance during sexual activity (Body Appearance Cognitive Distraction Scale). Results: Cognitive distraction with the appearance of the body intervenes in the association between dissatisfaction with the body and sexual difficulties. In addition, the effect of body dissatisfaction on sexual distress, in the presence of the mediating variable was reduced to non-significance, thus revealing a full mediation effect of cognitive distraction based on the body's appearance in the association between body dissatisfaction and sexual distress. Conclusion: This study advances our understanding of sexuality during pregnancy by evaluating sexual distress. As such, the data provide a more accurate picture on the sexual distress that women experience during pregnancy in relation to body dissatisfaction

탈초점 흐림 정도의 예측 및 그 신뢰도를 이용한 깊이 맵 작성 기법

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2016. 2. 김태정.깊이 맵이란 영상 내에서 촬영 장치로부터 가깝고 먼 정도를 수치적으로 나타낸 것으로서 영상의 3차원 구조를 나타내기 위해 널리 쓰이는 표현 방식이다. 2차원 영상으로부터 깊이 맵을 예측하기 위해서는 탈초점 흐림, 장면의 기하학적 구조, 객체의 주목도 및 움직임 등 다양한 종류의 깊이 정보가 활용된다. 그 중에서도 탈초점 흐림은 널리 이용되는 강력한 정보로서 탈초점 흐림으로부터 깊이를 예측하는 문제는 깊이를 예측하는 데 있어서 매우 중요한 역할을 한다. 본 연구는 2차원 영상만을 이용하여 깊이 맵을 예측하는 것을 목표로 하며 이 때, 촬영 장치로부터 영상 내 각 영역의 거리를 알아내기 위해 탈초점 거리 예측을 이용한다. 먼저 영상을 촬영할 때 영상 내 가장 가까운 곳에 초점이 맞춰져 있다고 가정하면 촬영 장치로부터 멀어짐에 따라 탈초점 흐림의 정도가 증가하게 된다. 탈초점 거리 기반 깊이 맵 예측 방법은 이를 이용하여 탈초점 흐림의 정도를 측정함으로써 거리를 예측하는 방식이다. 본 연구에서는 탈초점 거리로부터 깊이 맵을 구하는 새로운 방법을 제안한다. 먼저 인간의 깊이 지각 방식을 고려한 지각 깊이를 정의하고 이를 이용하여 탈초점 거리 예측의 (실제) 신뢰도를 정의하였다. 다음으로 그래디언트 및 2차 미분 값에 기반한 탈초점 거리 예측 결과에 대하여 신뢰도를 예측하는 방법을 설계하였다. 이렇게 예측한 신뢰도 값은 기존의 신뢰도 예측 방법으로 예측한 것에 비하여 더 정확하였다. 제안하는 깊이 맵 작성 방법은 조각 단위 평면 모델에 기반하였으며, 비용 함수는 데이터 항과 평활도 항으로 구성되었다. 깊이 맵의 전체 비용 함수를 최적화하는 과정에서는 반복적 지역 최적화 방식을 사용하였다. 제안하는 방법을 검증하기 위한 실험에는 인공 영상 및 실제 영상들을 사용하여 제안하는 방법과 기존의 탈초점 거리 기반 깊이 맵 예측 방법들을 비교하였다. 그 결과, 제안하는 방법은 기존의 방법들보다 더 나은 결과를 보여주었다.The depth map is an absolute or relative expression of how far from a capturing device each region of an image is, and a popular representation of the 3D (three-dimensional) structure of an image. There are many depth cues for depth map estimation using only a 2D (two-dimensional) image, such as the defocus blur, the geometric structure of a scene, the saliency of an object, and motion parallax. Among them, the defocus blur is a popular and powerful depth cue, and as such, the DFD (depth from defocus) problem is important for depth estimation. This paper aims to estimate the depth map of a 2D image using defocus blur estimation. It assumes that the focus region of an image is nearest, and therefore, the blur radius of the defocus blur increases with the distance from the capturing device so that the distance can be estimated using the amount of defocus blur. In this paper, a new solution for the DFD problem is proposed. First, the perceptual depth, which is based on human depth perception, is defined, and then the (true) confidence values of defocus blur estimation are defined using the perceptual depth. Estimation methods of confidence values were designed for the gradient- and second-derivative-based focus measures. These estimated confidence values are more correct than those of the existing methods. The proposed focus depth map estimation method is based on the segment-wise planar model, and the total cost function consists of the data term and the smoothness term. The data term is the sum of the fitting error costs of each segment at the fitting process, and the confidence values are used as fitting weights. The smoothness term means the amount of decrease of total cost function by merging two adjacent segments. It consists of the boundary cost and the similarity term. To solve the cost optimization problem of the total cost function, iterative local optimization based on the greedy algorithm is used. In experiments to evaluate the proposed method and the existing DFD methods, the synthetic and real images are used for qualitative evaluation. Based on the results, the proposed method showed better performances than the existing approaches for depth map estimation.Chapter 1 Introduction 1 1.1 Focus Depth Map 1 1.1.1 Depth from Defocus Blur 2 1.1.2 Absolute Depth vs. Relative Depth 3 1.2 Focus Measure 4 1.3 Approaches of the Paper 5 Chapter 2 Blur Estimation Methods Using Focus Measures 6 2.1 Various Blur Estimation Methods 6 2.1.1 Gradient-based Methods 6 2.1.2 Laplacian-based Methods 8 2.1.3 Gaussian-filtering-based Methods 12 2.1.4 Focus Measure Based on Adaptive Derivative Filters 12 2.2 Comparison of the Blur Estimators 15 Chapter 3 Confidence Values of Focus Measures 21 3.1 True Confidence Value 21 3.1.1 Perceptual Depth by the Parallactic Angle 21 3.1.2 True Confidence Value Using the Perceptual Depth and Blur Radius 23 3.1.3 Examples of True Confidence Values 26 3.2 Confidence Value Estimation Methods for Various Focus Measures 27 3.2.1 Blur Estimator Based on the Gradient Focus Measure 27 3.2.2 Blur Estimator Based on the Second Derivative Focus Measure 29 Chapter 4 Focus Depth Map Estimation 31 4.1 Piecewise Planar Model 31 4.2 The Proposed Focus Depth Map Estimation Method 34 4.2.1 Cost Function 34 4.2.2 Depth Map Generation Algorithm 38 Chapter 5 Experimental Results 40 5.1 Comparison of the Confidences Value Estimation Methods of Focus Measures 40 5.2 Performances of the Proposed Depth Map Generation Method 70 5.2.1 Experiments on Synthetic Images 70 5.2.2 The Experiments on Real Images 73 5.2.3 Execution Time 81 Chapter 6 Conclusion 84 Bibliography 86 국문 초록 91Docto

Digital Image Processing

This book presents several recent advances that are related or fall under the umbrella of 'digital image processing', with the purpose of providing an insight into the possibilities offered by digital image processing algorithms in various fields. The presented mathematical algorithms are accompanied by graphical representations and illustrative examples for an enhanced readability. The chapters are written in a manner that allows even a reader with basic experience and knowledge in the digital image processing field to properly understand the presented algorithms. Concurrently, the structure of the information in this book is such that fellow scientists will be able to use it to push the development of the presented subjects even further

The use of low cost virtual reality and digital technology to aid forensic scene interpretation and recording

© Cranfield University 2005. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright owner.Crime scenes are often short lived and the opportunities must not be lost in acquiring sufficient information before the scene is disturbed. With the growth in information technology (IT) in many other scientific fields, there are also substantial opportunities for IT in the area of forensic science. The thesis sought to explore means by which IT can assist and benefit the ways that forensic information can be illustrated and elucidated in a logical manner. The central research hypothesis considers that through the utilisation of low cost IT, the visual presentation of information will be of significant benefit to forensic science in particular for the recoding of crime scenes and its presentation in court. The research hypothesis was addressed by first exploring the current crime scene documentation techniques; their strengths and weaknesses, giving indication to the possible niche that technology could occupy within forensic science. The underlying principles of panoramic technology were examined, highlighting its ability to express spatial information efficiently. Through literature review and case studies, the current status of the technology within the forensic community and courtrooms was also explored to gauge its possible acceptance as a forensic tool. This led to the construction of a low cost semi-automated imaging system capable of capturing the necessary images for the formation of a panorama. This provides the ability to pan around; effectively placing the viewer at the crime scene. Evaluation and analysis involving forensic personnel was performed to assess the capabilities and effectiveness of the imaging system as a forensic tool. The imaging system was found to enhance the repertoire of techniques available for crime scene documentation; possessing sufficient capabilities and benefits to warrant its use within the area of forensics, thereby supporting the central hypothesis

Open tools for dendrochronology. Advances in sample digitization and deep learning methods for image segmentation

Dendrochronological techniques are paramount in forest research. The current climate change scenario and the central role of forests in biogeophysical cycles enforce the importance of novel techniques to get accurate data from trees and their relationship with the environment in faster ways. Recent technological advances and the place of open source software and hardware are making free, user-developed tools for forest research available to the research community. The aim of this Ph.D. thesis is the development of tools for image acquisition and data collection in dendrochronology based on open source software and hardware. Thus, four different tools for dendrochronological research are presented in five different chapters. The first chapter focuses on the development of a do-it-yourself tool based on open source hardware for image acquisition and wood sample digitization at high resolution. We used open hardware equipment from Arduino and Python programming to develop CaptuRING and published the entire free open source tool as: "CaptuRING: A Do-It-Yourself tool for wood sample digitization" in Methods in Ecology and Evolution, 2022; 13:1185-1191. Furthermore, the original software was registered in the Registro General de Propiedad Intelectual (00/2022/737) of Ministerio de Cultura y Deporte (Spain). The second chapter presents "How to build and install your own CaptuRING". This contribution presents a series of videos with a step-by-step guide to promote the use of CaptuRING in the research community. The manuscript and related videos have been submitted for publication. The third chapter describes ρ-MtreeRing. This free and open-source software, which is written in R, analyzes X-ray films from dendrochronological samples to get microdensity values automatically segmented through a graphical user interface. The open source tool and manuscript are published as: "ρ-MtreeRing. A graphical user interface for X-ray microdensity analysis" in Forests. 2021; 12(10):1405. The fourth chapter describes the potential of deep learning methods to automatically segment xylem vessels. We trained three different convolutional neural networks to segment vessels in stained wood microsections using the Keras framework in Python. Our results demonstrate the potential of these techniques to automatically segment xylem vessels and overcome derived problems from image illumination, which hamper segmentation using classical image segmentation methods. The manuscript is published as "Convolutional neural networks for segmenting xylem vessels in stained cross-sectional images" in: Neural Computing & Applications, 2020; 32:17927-17939. The fifth chapter develops an algorithm to delineate annual ring limits in stained wood microsections of a species with diffuse porous wood using convolutional neural networks. We used Python for image processing and the Keras framework for the algorithm training. The results show the ability of this techniques to obtain accurate tree ring segmentation for quantitative wood anatomy, reaching similar or even outperforming conventional manual delimitation in most of the evaluated cases. The results of this chapter will be presented in the manuscript "Deep Learning for ring bordering in stained cross-sectional images". This PhD Thesis presents four open source tools to get accurate information from wood features to unveil how trees respond to the environment. From digitization at macroscopic perspective, automatic data collection and the development of feature segmentation on microscopic samples. The presented four novel dendrochronological tools based on open source software facilitates forest research in the current climate change scenario.Las técnicas dendrocronológicas son fundamentales en la investigación forestal. El escenario actual de cambio climático y el papel central de los bosques en los ciclos biogeofísicos subrayan la necesidad de nuevas técnicas para obtener de un modo ágil datos precisos de los árboles y de su relación con el medio ambiente. Los recientes avances tecnológicos, además de la disponibilidad actual del software y el hardware de código abierto están poniendo a disposición de la comunidad investigadora herramientas gratuitas desarrolladas por los usuarios para la investigación forestal. El objetivo de esta tesis doctoral es el desarrollo de herramientas para la adquisición de imágenes y la recogida de datos basadas en software y hardware de código abierto para el estudio dendrocronológico. Esta tesis presenta cuatro herramientas diferentes para esta rama científica en cinco capítulos diferentes. El primer capítulo se centra en el desarrollo de una herramienta "hágalo usted mismo" basada en hardware de código abierto para la adquisición de imágenes y la digitalización de muestras de madera a alta resolución. Usamos equipos de hardware abierto de Arduino y programación de Python para desarrollar CaptuRING y publicamos la herramienta completa de código abierto como: "CaptuRING: A Do-It-Yourself tool for wood sample digitization" en Methods in Ecology and Evolution, 2022; 13:1185-1191. Además, el software original fue registrado en el Registro General de Propiedad Intelectual (00/2022/737) del Ministerio de Cultura y Deporte (España). El segundo capítulo presenta "Cómo construir e instalar su propio CaptuRING" ("How to build and install your own CaptuRING"). Esta contribución presenta una serie de vídeos con una guía paso a paso para promover el uso de CaptuRING en la comunidad investigadora. El manuscrito y los vídeos relacionados se han enviado para su publicación. El tercer capítulo describe ρ-MtreeRing. Este software gratuito y de código abierto, que está escrito en R, analiza imágenes de rayos X de muestras dendrocronológicas para obtener valores de microdensidad automáticamente segmentados a través de una sencilla interfaz gráfica de usuario. La herramienta de código abierto y el manuscrito se publicaron como: "ρ-MtreeRing. A graphical user interface for X-ray microdensity analysis" en Forests. 2021; 12(10):1405. El cuarto capítulo describe el potencial de los métodos de aprendizaje profundo para segmentar automáticamente los vasos del xilema. Entrenamos tres redes neuronales convolucionales diferentes para segmentar vasos en cortes histológicos de madera utilizando el marco Keras en Python. Nuestros resultados demuestran el potencial de estas técnicas para segmentar automáticamente los vasos del xilema y superar los problemas derivados de la iluminación de la imagen, que dificultan la labor de métodos clásicos de segmentación de imágenes. El manuscrito se publicó como "Convolutional neural networks for segmenting xylem vessels in stained cross-sectional images" en: Neural Computing & Applications. 2020; 32:17927-17939. El quinto capítulo desarrolla un algoritmo para delinear los límites anuales de los anillos en cortes histológicos de una especie con madera difuso-porosa utilizando redes neuronales convolucionales. Se utilizó Python para el procesamiento de imágenes y el marco Keras para el entrenamiento del algoritmo. Los resultados muestran la capacidad de estas técnicas para obtener una segmentación precisa de los anillos de los árboles para la anatomía cuantitativa de la madera alcanzando, en la mayoría de los casos evaluados, un rendimiento similar o incluso superior a la delimitación manual convencional. Los resultados de este capítulo se presentarán en el manuscrito "Deep Learning for ring bordering in stained cross-sectional images". Esta Tesis Doctoral presenta cuatro herramientas de código abierto para obtener información precisa de las características de la madera investigar cómo los árboles responden al entorno facilitando la investigación en el actual escenario de cambio climático.Escuela de DoctoradoDoctorado en Conservación y Uso Sostenible de Sistemas Forestale

Statistical and perceptual properties of images and videos with applications

The visual brain is optimally designed to process images from the natural environment that we perceive. Describing the natural environment statistically helps in understanding how the brain encodes those images efficiently. The Natural Scene Statistics (NSS) of the luminance component of images is the basis of several univariate statistical models. Such models were the fundamental building blocks of multiple visual applications, ranging from the design of faithful image and video quality models to the development of perceptually optimized image enhancing techniques. Towards advancing this area, I studied the bivariate statistical properties of images and developed the first of its kind closed-form model that describes the correlation of spatially separated bandpass image samples. I found that the model was useful in tackling different problems such as blindly assessing the quality of images and assessing 3D visual discomfort of stereo images. Provided the success of NSS in tackling image processing problems, I decided to use them as a tool to tackle the blind video quality assessment (VQA) problem. First, I constructed a video quality database, the LIVE Video Quality Challenge Database (LIVE-VQC). This database is the largest across several key dimensions: number of unique contents, distortions, devices, resolutions, and videographers. For collecting the subjective scores, I constructed a new framework in Amazon Mechanical Turk. A massive number of subjects from across the globe participated in my study. Those efforts resulted in a VQA database that serves as a great benchmark for real-world videos. Next, I studied the spatio-temporal statistics of a wide variety of natural videos and created a space-time completely blind VQA model that deploys a directional temporal NSS model to predict quality. My newly created model outperforms all previous completely blind VQA models on the LIVE-VQCElectrical and Computer Engineerin

Modelling the total appearance of gonio-apparent surfaces using stereo vision

Over recent decades, the textured coating provided by metallic surfaces has been an important factor in attracting customers of the automobile industry. This has meant that quantifying the appearance of coating products is essential for product development and quality control. The appearance of these coated products strongly depends on the viewing geometry, giving rise to a variety of properties of perceptual attributes such as texture, colour and gloss. Due to the visually-complex nature of such coatings, there remains an unsatisfied demand to develop techniques to measure the total appearance of metallic coatings. This study describes which aims to define the total appearance of metallic coatings and then objectively characterise it. Total appearance here refers to the combination of three properties of perceptual attributes of the surface: glint, coarseness and brightness. A number of metallic panels were visually scaled and a computational model capable for predicting three perceptual attributes was developed. A computational model was developed to relate the results from this psychophysical experiment to data obtained from a stereo image capture system. This is a new alternative technique aimed at solving one of the most challenging problems in computer vision: stereo matching. In the system, two images are captured by a same camera under two different lighting conditions to mimic stereoscopic vision. This not only addresses the problem of stereo matching (i.e. to find the corresponding pixels between two images) but also enhances the effect of perceptual attributes. After linearisation of camera response, spatial uniformity correction was performed to minimise the effect of uneven illumination. A characterisation method was then used to transfer the RGB to device-independent values. Two images captured under different lighting conditions were merged to obtain stereo data. In glint feature extraction, the pixels in the final image were segmented into two regions: bright spots and dark background. Next, statistical analyses were applied to extract features. Finally a model was created to predict the glint attribute of the metallic coating panels based on an image captured by the stereo capture system. In coarseness feature extraction, the merged image transformed to frequency domain using a discrete Fourier Transform. An octave bandpass filter was then applied to the Fourier Spectra image and data analysis was carried out to achieve the “image variance value” for each band. In similar to final step of glint, a model was created to predict the coarseness attribute

Small Particle Transport in Fibrin Gels and High Throughput Clot Characterization

The formation, function, and lysis of blood clots is largely governed by the transport of nano- and micro-scale particles. Yet there is not fully established physics that relates clot structure to transport phenomena such as fluid permeation and particle diffusion. This dissertation explores small particle transport in fibrin. I report on the size-dependence of particle mobility in fibrin, and discuss the implications of these results for fibrinolytic drug design. I measure the relationship between fibrin permeability and diffusion of 0.2--2.8 micron particles in fibrin gels, then determine the time and length scales at which small particle diffusion is directly related to bulk gel permeability. This result implies that one could develop a high throughput clot characterization assay that provides more detail than turbidity, the predominant high throughput measurement. I also present my work designing and developing systems to perform these and other experiments in high throughput, which include novel technologies for optical microscopy and magnetic force application.Doctor of Philosoph

Diurnal Fluctuations and Developmental Changes in Ocular Dimensions and Optical Aberrations in Young Chicks

PURPOSE. To investigate further the emmetropization process in young chicks by studying the diurnal fluctuations and developmental changes in the ocular dimensions and optical aberrations, including refractive errors, of normal eyes and eyes that had the ciliary nerve sectioned (CNX). METHODS. The ocular dimensions and aberrations in both eyes of eight CNX (surgery on right eyes only) and eight normal chicks were measured with high-frequency A-scan ultrasonography and aberrometry, respectively, four times a day on five different days from posthatching day 13 to 35. A fixed pupil size of 2 mm was used to analyze aberration data. Repeatedmeasures ANOVA was applied to examine the effects of age, time of day, and surgery. RESULTS. Refractive errors and most higher-order aberrations decreased with development in both normal and CNX eyes. However, although normal eyes showed a positive shift in spherical aberration with age, changing from negative spherical aberration initially, CNX eyes consistently exhibited positive spherical aberration. Anterior chamber depth, lens thickness, vitreous chamber depth, and thus optical axial length all increased with development. Many of these ocular parameters also underwent diurnal changes, and mostly these dynamic characteristics showed no age dependency and no effect of CNX. Anterior chamber depth, vitreous chamber depth, and optical axial length were all greater in the evening than in the morning, whereas the choroids were thinner in the evening. Paradoxically, eyes were more hyperopic in the evening, when they were longest. Although CNX eyes, having enlarged pupils, were exposed to larger higher-order aberrations, their growth pattern was similar to that of normal eyes. CONCLUSIONS. Young chicks that are still emmetropizing, show significant diurnal fluctuations in ocular dimensions and some optical aberrations, superimposed on overall increases in the former and developmental decreases in the latter, even when accommodation is prevented. The possibility that these diurnal fluctuations are used to decode the eye's refractive error status for emmetropization warrants investigation. That eyes undergoing ciliary nerve section have more higher-order aberrations but do not become myopic implies a threshold for retinal image degradation below which the emmetropization process is not affected. I t has become increasingly apparent that the eye cannot be viewed as a static system, optically, anatomically, or physiologically. A number of ocular parameters, including refractive errors, ocular dimensions and intraocular pressure (IOP), undergo dynamic changes on both short (seconds) and longer time scales. One interesting manifestation of these dynamics is the various diurnal rhythms that have been reported in conjunction with ocular function. For example, rhythms in melatonin production, IOP, pupil size, and corneal epithelial thickness have been reported. 13,14 The cues used to decode the sign of defocus during emmetropization are not known. Plausibly, the eye could use odd-error cues from astigmatism and higher-order aberrations to decode the sign of defocus (Hunter J, et al. IOVS 2003;44: ARVO E-Abstract 4341). 15 Drawing on an analogy with accommodation in humans where accommodative microfluctuations play a role in decoding the sign of defocus, 16 diurnal fluctuations in refractive errors and/or higher order optical aberrations could play a similar role in emmetropization. Short-term fluctuations in higher-order aberrations 17 as well as changes on the scale of days, weeks, and months have been reported in young adult humans