Stanley A. Klein

Professor of Vision Science and Optometry

Spatial vision modeling; Non-linear systems analysis; Corneal topography and contact lens design

Modeling of Spatial Vision and Its Application in Image Compression The visual system is assumed to consist of an enormous number of spatial filters with different positions, sizes, orientations and bandwidths. These filters are arranged in sequential stages with nonlinear interactions between and within the stages. In our laboratory, we do psychophysical experiments to learn about the multiple stages of visual processing. We are currently deve-loping models of position acuity and motion processing in normal and abnormal vision. One result of this research is that we now hold the Guinness record for position acuity.

We are actively applying our modeling research to developing a human vision based quality metric for image sequences. This research has a very important application to MPEG image compression (used by HDTV). With an improved fidelity metric we will be able to more accurately determine whether tiny regions of compressed images are visibly different from the original. By this means the sparse bits being transmitted can be reallocated more efficiently.

Nonlinear Systems Analysis with Application to Localizing VEP Sources The use of PET and MRI scans for imaging brain activity has created much excitement among brain researchers. The research of my group indicates that a recent breakthrough in applying nonlinear analysis to the visual evoked potential (VEP) should reveal the underlying neural generators with temporal resolution 1000 times better than is possible with either MRI or PET. In addition there are improvements in the signal to noise ratio. We are also applying nonlinear analysis tools to both the VEP and the electroretinogram to learn about the retinal luminance gain control and the retinal and cortical contrast gain control.

Corneal Topography, Contact Lens Design and Elimination of Aberrations I am collaborating with Bob Mandell (Optometry) and Brian Barsky (Computer Science) to make major improvements in the way corneal shape is measured and the way contact lenses are designed. Our interdisciplinary group has already developed an algorithm for measuring corneal shape that surpasses competing algorithms. We are also developing new methods for measuring the full aberrations of the eye and then correcting the aberrations with a contact lens. By this means it should be possible to more than double the observer's acuity. This capability would allow one to photograph the retina with higher resolution. It would also allow much greater control of individual cone stimulation.

Selected Publications

Slotnick, S.D., Klein, S.A., Carney, T., Sutter, E.E. & Dastmalchi, S. (1999). Using multi-stimulus VEP source localization to obtain a retinotopic map of human primary visual cortex. Clinical Neurophysiology. 110, 1793-1800. (abstract-PDF)

Slotnick, S.D., Klein, S.A., Carney, T. & Sutter, E. (2001). Electrophysiological estimate of human cortical magnification. Clin Neurophysiology, 112: 1349-1356. (abstract-PDF)

Yu, C., Klein, S.A., & Levi, D.M. (2001). Surround Modulation of perceived contrast and the role of brightness induction. Journal of Vision, 1, 18-31 (abstract-PDF)

Klein, S.A. (2001) Problems with wavefront aberrations applied to refractive surgery: Developing standards. Opthalmic Technologies XI. F Manns, PG Soderberg, & A Ho, Eds. Proc. SPIE 4245. 47-56. (abstract-PDF)

Klein, S.A. (2001). Measuring, Estimating and Understanding the Psychometric Function: A Commentary. Perception & Psychophysics. 63. 1421-1455. (abstract-PDF)

Baldo M.V., Kihara A.H., Namba J, Klein S.A. (2002). Evidence for an attentional component of the perceptual misalignment between moving and flashing stimuli. Perception, 31, 17-30. (abstract-PDF)

Klein, S.A. (2002). Libet's Temporal Anomalies: A Reassessment of the Data. Consciousness and Cognition. 11, 198-214. (abstract-PDF)

Klein, S.A., Corzine, J., Corbin, J., Wechsler, S., & Carney, T. (2002). Wide angle cornea-sclera (ocular) topography. Opthalmic Technologies XII. F Manns, PG Soderberg, & A Ho, Eds. Proc. SPIE 4611. 149-158.
(abstract-PDF)

Levi, D.M. & Klein, S.A. (2002) Classification images for detection and position discrimination in the fovea and parafovea. Journal of Vision, 2, 46-65. (abstract-PDF)

Levi, D.M., Klein S.A., & Hariharan, S. (2002). Suppressive and facilitatory spatial interactions in foveal vision: Foveal crowding is simple contrast masking. Journal of Vision, 2, 140-166. (abstract-PDF).

Links

Stanley Klein Laboratory

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