High precision contrast ratio display for visual stimulus
AssigneeCarl Zeiss Meditec AG
InventorGöran Anders Johansson
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Abstract
Embodiments of the present invention include approaches for controlling light valve devices to improve the range and precision of the contrast ratio and the grayscale levels of a display used for visual field tests. In one embodiment, two or more illumination devices are used to enable the display device to display a wide range of contrast stimuli at precise illumination intensities over a fixed background illumination level. In another embodiment, the gamma curves of the display elements are adjusted to allow greater variations in the brightness of the display.
Claims25
A method of displaying images during a visual field test using a display device with a plurality of pixel elements, said elements generating a level of brightness which varies in response to the level of the drive signal supplied to the elements in accordance with a gamma curve, the method comprising:
- determining a first desired contrast and first range of brightness values for the images displayed during a first portion of the field test;
- setting the gamma curve to produce said first desired contrast and first range of brightness values in response to variations in the drive signals during said first portion of the field test;
- determining a second desired contrast and second range of brightness values for the images displayed during a second portion of the field test;
- and
- changing the gamma curve to a new setting to produce said second desired contrast and second range of brightness values in response to variations in the drive signals during said second portion of the field test.
An apparatus for performing visual field testing comprising:
- a display having a plurality of pixel elements,
- a controller for supplying drive signals to the pixel elements, wherein said pixel elements generate an image having a level of brightness that varies in response to the level of the drive signal supplied to the elements in accordance with a gamma curve and wherein said controller operates such that during a first portion of the field test, the gamma curve is set to produce a first desired contrast and first range of brightness values in response to variations in the drive signals and a second portion of the field test, the gamma curve is reset to produce a second desired contrast and second range of brightness values in response to variations in the drive signals.
Dependencies are inferred from the claim text.