HIGH PRECISION CONTRAST RATIO DISPLAY FOR VISUAL STIMULUS

• US 20120236262A1
• Filed: 02/24/2012
• Published: 09/20/2012
• Est. Priority Date: 12/12/2008
• Status: Active Grant

• Current Assignee: Carl Zeiss Meditec Incorporated (Carl-Zeiss-Stiftung)
• Original Assignee: Carl Zeiss Meditec Incorporated (Carl-Zeiss-Stiftung)
• Inventors: Johansson, Göran Anders
• Granted Patent: US 8,371,696 B2
• Time in Patent Office: Days
• US Class Current: 351/224
• CPC Class Codes: A61B 3/0041 characterised by display arrangements
• CPC Class Codes: A61B 3/024 for determining the visual field, e.g. perimeter types

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.

Claims

1-28. -28. (canceled)

29. A method for controlling a backlit light valve display device during a patient vision test comprising:

determining an illumination level to be perceived;

determining a background light illumination intensity, wherein the background illumination is not modified by the light valve device;

determining a light valve backlight illumination intensity, wherein the backlight illumination is modified by the light valve device;

creating a sequence of frames, each frame composed of light from the background light at a background frame intensity and light valve backlight at a backlight frame intensity; and

displaying the sequence of frames at a rate which, when viewed by a human, is perceived to be the determined illumination level.

30-33. -33. (canceled)

34. A display apparatus comprising:

a liquid crystal element including an array of pixels with the level of transmission of each element being controllable;

a source of light located behind the liquid crystal element and directed to illuminate the pixels and with the level of brightness of the light source being controllable; and

a controller for operating both the liquid crystal element and the light source, said controller receiving information to be displayed, said controller creating a first set of transmission and brightness levels during a first frame and during a second frame, supplying uniform transmission information to all the pixels, said controller alternating between the first frame and the second frame at a rate so that they are perceived by the human eye as a common image.

35. A display as recited in claim 34, wherein the brightness of the source of light is independently adjustable for each of the two frames.

36. A display according to claim 34, wherein the frame rate is at least 10 frames per second.

37. A display according to claim 34, wherein the frame rate is at least 30 frames per second.

38. A method according to claim 34 wherein said uniform transmission corresponds to the maximum level of transmission though the pixels of the liquid crystal element.

39. A display device for use in a visual field test apparatus, said display comprising:

an array of light valve elements, with the level of transmission of each element being controllable;

a source of back light located on one side of the array and positioned so that the light generated by the source can be transmitted through the light valve elements and with the level of brightness of the back light being controllable; and

a controller for controlling the level of transmission of the light valve elements and the level of brightness of the back light source and wherein the controller creates a first set of transmission and brightness levels during a first frame and a second, different set of transmission and brightness levels during a second frame, said controller alternating between the first and second frames at least 10 times per second.

40. A display device as recited in claim 39, wherein the first and second frames are alternated at a rate of at least 30 per second.

41. A display device as recited in claim 39, wherein the set of transmission levels in one of the two sets is arranged for maximum transmission.

42. A display device as recited in claim 39, wherein the controller creates a third set of transmission and brightness levels during a third frame and first, second and third frames are displayed in sequence.

43. A display device as recited in claim 39, further comprising an additional light source, wherein the additional light source is used to expand the available range of transmission and brightness levels.

44. A visual field test apparatus comprising:

a display having a plurality of pixel elements for generating a background and a plurality stimuli for observation by a patient; and

a controller for supplying drive signals to the pixel elements, wherein said pixel elements have 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 the slope of the gamma curve near the brightness level corresponding to the background is less than the slope of the gamma curve at the opposed ends thereof.

45. A visual field test apparatus as recited in claim 44, wherein the stimuli are frequency doubling technology (FDT) stimuli.

46. A visual field test apparatus as recited in claim 44, wherein the stimuli are standard automated perimetry (SAP) stimuli.

47. A visual field test apparatus as recited in claim 44, wherein the plurality of pixel elements are light emitting elements.

48. A visual field test apparatus as recited in claim 47, wherein the light emitting elements are light-emitting diodes (LEDs).

49. A visual field test apparatus as recited in claim 47, wherein the light emitting elements are organic light-emitting diodes (OLEDs).

50. A visual field test apparatus as recited in claim 44, wherein the gamma curve is symmetric about the brightness level corresponding to the background.