Image enhancement filters in CCTVs significantly improve reading performance for low-vision observers

Teri B. Lawton

doi:10.1117/12.137429

14 August 1992 Image enhancement filters in CCTVs significantly improve reading performance for low-vision observers

Teri B. Lawton

Proceedings Volume 1644, Ophthalmic Technologies II; (1992) https://doi.org/10.1117/12.137429
Event: OE/LASE '92, 1992, Los Angeles, CA, United States

Abstract

As people age, so do their photoreceptors. If the visual system has been exposed to sufficient UV radiation combined with other precursors for age-related maculopathies (ARM), then a large number of photoreceptors in central vision stop functioning when the person reaches their late sixties and early seventies. There are channels in the visual system tuned to different bands, approximately one octave, of spatial frequencies. In low vision observers with ARM, the loss of central vision causes a loss in channels sensitive to spatial frequencies above 8 to 10 cyc/deg. Therefore, for ARM observers, words must be magnified to read normal text. I have developed image enhancement filters that compensate for the low vision observer's losses in contrast sensitivity to intermediate and high spatial frequencies. These filters automatically enhance the text displayed on closed-circuit TVs (CCTVs) and render the text in shades of gray more easily perceivable than black and white text. These filters work by boosting the amplitude of the less visible intermediate spatial frequencies more than the lower spatial frequencies. Not only do these image enhancement filters reduce the magnification needed for reading by up to 70%, they also increase the speed that can be used to read text two to four times. A short summary of this research is presented.

Citation Download Citation

Teri B. Lawton "Image enhancement filters in CCTVs significantly improve reading performance for low-vision observers", Proc. SPIE 1644, Ophthalmic Technologies II, (14 August 1992); https://doi.org/10.1117/12.137429

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