CONTRAST IMPROVEMENT IN PRE-COMPENSATION OF OCULAR ABERRATIONS FOR COMPUTER USERS Jian Huang 1 , Armando Barreto 1 , Miguel Alonso Jr. 2 , Malek Adjouadi 1 1 Electrical & Computer Engineering Department, Florida International University, Miami, FL 2 School of Engineering & Technology, Miami-Dade College, Miami, FL ABSTRACT Ocular aberrations in the human eye prevent many users from interacting efficiently with Graphic User Interfaces in computers. While traditionally these aberrations are corrected by external means (e.g., spectacles, refractive surgery), there have been approaches to address them by custom pre-compensation of the displayed images, based on the characterization of the eye’s aberrations. However, the limited intensity levels of display devices reduce the contrast perceived by the user when viewing the pre-compensated images. This paper proposes a histogram side-trim correction method for the pre-compensated images that seeks to reduce the contrast loss perceived by the viewer. The proposed histogram trimming process is designed to be automatic, not requiring manual intervention. Experiments are performed using a high-resolution camera as an “artificial eye”, to evaluate the efficiency of the histogram side-trim method in improving the contrast of perceived images. Results show that the side-trim method improved the contrast of images perceived by the “artificial eye”. Keywords: Vision Correction, Contrast Enhancement, Histogram Analysis, Deconvolution, Image Enhancement. INTRODUCTION Visual perception is the primary approach for humans to interact with computers. Many computer users with severe ocular aberrations cannot easily recognize pictures, icons and text displayed on computer screens, limiting their benefit from the basic forms of information presentation used by most contemporary computer interfaces. Thus, they must use methods of vision correction to interact with computers efficiently. In general, different methods (e.g., optical lenses, contact lenses, refractive surgery, intraocular implants) have been widely used to correct common defocus and astigmatism aberrations, as well as some high order aberrations, but corrections made by these methods are static [1]- [3]. Recently, adaptive optics has also emerged as a potential technique aiming to achieve aberration- free vision, although its practical application is limited by the specialized equipment required [4] [5]. Until now, adaptive optics has mainly been used as a tool to characterize ocular aberrations and evaluate the visual performance of human eyes. The above techniques are meant for general vision correction. They are not particularly designed to aid computer users, but instead they attempt to rectify the human eye’s optical characteristics, in general. However, in the context of human-computer interaction, the correction could also be performed in the computer itself, since information to be viewed is displayed on the computer screen, and it can be manipulated before it is displayed. From this point of view, methods based on image processing have been created to manipulate the images to be displayed in order to help computer users with low vision achieve better visual performance. Peli et al., [6]-[8] proposed a conceptual pre-emphasis model of image enhancement for the visually impaired based on the contrast sensitivity function. Recently, Alonso et al., [9]-[11] proposed a software pre-compensation method to improve the perception of intended display images for computer users with impaired vision, in which the vision correction is easy to update as progress of the visual impairment requires it. Based on the measurement of the particular ocular aberration of a user’s eye, this pre-compensation method is able to present that user customized images to counteract his/her specific aberrations. The pre-compensation method has been verified to