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Visual Acuity and Contrast Sensitivity with compressed motion video

Author: Bijl, P. · Vries, S.C. de
Type:article
Date:2009
Publisher: Spie: The International Society for Optical Engineering.
Place: Bellingham, WA
Institution: TNO Defensie en Veiligheid
Source:Holst, G.C., Infrared Imaging Systems: Design, Analysis, Modeling, and Testing XX, 7300
Identifier: 28731
doi: doi:10.1117/12.819948
Article number: 730006
Keywords: Vision · Acuity · Contrast sensitivity target acquisition · Image compression · Performance · Sensor · TOD · Acuity · Complex background · Compression rates · Contrast loss · Contrast sensitivity · Contrast sensitivity target acquisition · Different sizes · High compression ratio · Motion video · Perception experiment · Performance · Test charts · Test method · Test Pattern · TOD · Triangle orientation discriminations · Visual acuity · Cameras · Computer control systems · Digital image storage · Image compression · Imaging systems · Infrared devices · Optoelectronic devices · Sensors · Thermography (imaging) · Vision · Testing · triangle orientation discrimination tod · contrast sensitivity · target aquisition · performance · image processing · visual acuity

Abstract

Video of Visual Acuity (VA) and Contrast Sensitivity (CS) test charts in a complex background was recorded using a CCD camera mounted on a computer-controlled tripod and fed into real-time MPEG2 compression/decompression equipment. The test charts were based on the Triangle Orientation Discrimination (TOD) test method and contained triangle test patterns of different sizes and contrasts in four possible orientations. In a perception experiment, VA and CS thresholds at the 75% correct level were obtained for three camera velocities (0, 1.0 and 2.0 deg/s or 0, 4.1 and 8.1 pix/frame) and four compression rates (no compression, 4Mb/s, 2Mb/s and 1 Mb/s). VA is shown to be rather robust to any combination of motion and compression. CS however dramatically decreases when motion is combined with high compression ratios. The data suggest that with the MPEG2 algorithm the emphasis is on the preservation of image detail at the cost of contrast loss. Keywords: sensor, image compression, performance, TOD, Acuity, Contrast Sensitivity Target Acquisition