Abstract: A graphical display includes multiple networked modules for controlling different group of pixels in the graphical display. In one embodiment, each module includes a network interface for receiving data and control signals, LED drivers for the pixels in the portion of the graphical display, and a control circuit that controls the currents in the LEDs in accordance with the control and data signals received. Memory modules may be provided to store data and programs for the control circuit. The network interfaces of the modules may comply with an industry standard computer network protocol.

Abstract: A method to be used in a light emitting diode (LED) display provides a fault-healing capability. The method is applicable to a display having pixels made up of LEDs of four or more primary colors. For each pixel, the method receives a signal specifying a light intensity and a color to be displayed and detects if a fault exists in an LED of one or more of the primary colors. When no fault is detected, the LEDs of the pixel are driven with currents to achieve the specified light intensity and color. Otherwise, the LEDs of the pixel are driven in the primary colors that are without fault, using a combination of currents to achieve the specified light intensity and color. The combination of currents is derived by finding a position of the specified color in a chromaticity diagram and, using that position, deriving the currents to drive the LEDs in the primary colors without fault.

Abstract: A method displays a single image on a graphical display for diagnostic purpose, without interrupting an observer's perception of the display of a sequence of images. Under that method, a sequence of images is displayed on a graphical display, interrupted only by the diagnostic image that is displayed for a time period not longer than 30 milliseconds. The diagnostic image may be used, for example, for calibrating colors and luminances of pixels in the graphical display. Another use of the diagnostic image may be, for example, determination of the ambient light reflected from the graphical display.

Abstract: A method maps a color specified using a smaller color gamut to a larger color gamut. Under that method, a map in a chromaticity diagram is constructed that provides a direction and a magnitude for a unit change in chroma for a specified pixel value in the chromaticity diagram. Using the magnitude and direction in the map, the specified color is mapped to a new pixel value corresponding to a predetermined shift in chromaticity. Preferably, the new pixel value preserves the hue of the specified color, and its luminance related to that of the specified color. Also, the new pixel value preferably has a greater color saturation than the specified pixel value.

Abstract: An apparatus dynamically circumvents faults in the light emitting diodes (LEDs) of a pixel in a graphical display. The LEDs are organized into groups of one or more LEDs. The apparatus includes drivers for generating a current to an associated group of LEDs of the pixel and fault detectors associated with each group of LEDs. The drivers may be driven, for example, by pulse-modulated signals specifying average currents for the groups of LEDs. The fault detectors each detect fault in an associated group of LEDs and asserts a fault signal when a fault is detected. In addition, an encoder is provided to receive the fault signals from the fault detectors and to provide signals encoding the faults detected and identifying the associated groups of LEDs. A controller that receives the encoded signals may adjust the driver signals for the groups of LEDs for which no fault is detected, in order to compensate for the detected faults.

Abstract: A method for use with an electronic signboard (e.g., an LED signboard) compensates psychovisual chromaticity shift due to ambient light. The method first measures a color of light reflected from the signboard. Based on the measurement a set of calorimetric equations defining the desired light to be perceived as being displayed by each pixel of the signboard are solved. The calorimetric equations are the additive color mixture of the ambient light and the light to be actually displayed by the pixel in the absence of ambient light. The calorimetric equations may be expressed in units of uniform color space. The solutions of the colorimetric equations are then used to control the light actually displayed by the pixel.

Abstract: A method computes drive currents for LEDs in a pixel of a signboard to achieve a desired color at a desired luminous intensity. This method is particular applicable to a signboard having pixels made up of four (4) or more primary colors. The method selects a number of colors within a color gamut, and for each selected color, the method computes drive currents for the LEDs of each basis color, such that the resulting luminous intensity of the selected color is maximum. Using the computed drive currents, the method then scales the drive currents to achieve the desired luminous intensity in the desired color. The drive currents may be computed, for example, using a constrained maximization technique, such as linear programming. In one embodiment, the drive currents for each selected color are computed subject to the constraint that none of the drive currents is negative, and that their total is less than a predetermined value.

Abstract: The present invention relates to a light-emitting diode (“LED”) display apparatus used for a display such as a type of standing signboard. The light-emitting diode display is comprised of light-emitting diodes which use a plurality of colors, including blues, reds and greens, arranged in a specific pattern such as a matrix pattern. The display is appropriate for displaying either a moving or a stationary graphical image by powering the LEDs to combine to produce specific colors.

Abstract: The present invention relates to a light-emitting diode (“LED”) display apparatus used for a display such as a type of standing signboard. The light-emitting diode display is comprised of light-emitting diodes which use a plurality of colors, including blues, reds and greens, arranged in a specific pattern such as a matrix pattern. The display is appropriate for displaying either a moving or a stationary graphical image by powering the LEDs to combine to produce specific colors.

Abstract: A method and system for protecting objects stored on network servers are presented. An object server runs computer software that designates which objects are to be protected and the security policy for that object. If the object server receives a request for a protected object, the object server creates an enhanced request containing cryptographically protected data related to the request and to the requested object; this enhanced request is redirected to a security server. The security server authenticates the request, retrieves the requested object from the object server, a file server associated with the security server, or a local cache, encrypts the object, and combines the encrypted object with mobile code, the security policy, and object controls to implement the policy. This package is then sent to the requester, which executes the mobile code, resulting in the installation of the security policy and object controls on the requester computer.

Abstract: A system and method for establishing a log file which may be used to create an audit trail are presented. A security server maintains a log file of actions performed by a requester and the security server which are related to protected objects. Object controls instantiated with the object on the requester device transmit an encrypted descriptor of the action to the security server and may prevent the requester device from taking any action (viewing, editing, printing, etc.) if there is no secure connection to the security server. The security server will record the information received from the requester device, along with other data, to the log file as well as recording a descriptor of any of the security server's actions taken which relate to the protection of objects.

Abstract: A method and system for protecting objects stored on network servers are presented. An object server runs computer software that designates which objects are to be protected and the security policy for that object. If the object server receives a request for a protected object, the object server creates an enhanced request containing encrypted data related to the request and the requested object; this enhanced request is redirected to a security server which authenticates the request, retrieves the requested object, encrypts the object using a one-time encryption key, and combines the encrypted object with mobile code, the security policy, and object controls to implement the policy. This package is then sent to the requester, which executes the mobile code, resulting in the instantiation of the security policy and object controls on the requester computer. The mobile code will execute tests to ensure proper instantiation of the object controls.