LED backlight for LCD with color uniformity recalibration over lifetime
First Claim
1. A light emitting diode (LED) light source system comprising:
- a support structure;
clusters of LEDs mounted on the support structure in an array, the LEDs in each cluster including at least a first LED for emitting light of a first color, a second LED for emitting light of a second color, and a third LED emitting light of a third color,the first color, the second color, and the third color, when combined, generating light having a white point;
a plurality of current sources, a first current source being connected to at least one LED emitting light of the first color, a second current source being connected to at least one LED emitting light of the second color, a third current source being connected to at least one LED emitting light of the third color, the current sources for controlling a brightness level of each color;
at least one optical sensor connected to the support structure, the at least one optical sensor detecting a light output of a cluster when at least one LED in a cluster is energized; and
a controller having a memory, the memory storing values for controlling an output current magnitude of each of the current sources so that a light output of the light source system has characteristics set by the values stored in the memory,the controller for calibrating a white point for all clusters by energizing LEDs within selected clusters and adjusting currents through LEDs in the selected clusters to cause a light output of each cluster to more closely match a target white point for that cluster based on values stored in the memory,wherein the controller is configured to perform the calibrating at various times over a lifetime of the light source system to offset degradation in the LEDs.
6 Assignments
0 Petitions
Accused Products
Abstract
An LED light source for LCD backlighting is described that recalibrates itself over time so that color and brightness uniformity across the backlight is maintained over the life of the backlight. The backlight contains clusters of red, green, and blue LEDs, each cluster generating a white point. In one embodiment, each color in a cluster has its own controllable driver so that the brightness of each color is a cluster is separately controllable. One or more optical sensors are arranged in the backlight, and the sensor signals are detected by processing circuitry to sense the light output of any LEDs that are energized in a single cluster. The measured white point and flux are compared to a stored target white point value and flux for that cluster. The currents to the RGB LEDs are then automatically adjusted to achieve the target level for each cluster. This process is applied to each cluster in sequence until the recalibration is complete. The recalibration takes place at various times over the lifetime of the backlight to offset the effects of LED degradation over time. Variations of this technique are also described.
-
Citations
30 Claims
-
1. A light emitting diode (LED) light source system comprising:
-
a support structure; clusters of LEDs mounted on the support structure in an array, the LEDs in each cluster including at least a first LED for emitting light of a first color, a second LED for emitting light of a second color, and a third LED emitting light of a third color, the first color, the second color, and the third color, when combined, generating light having a white point; a plurality of current sources, a first current source being connected to at least one LED emitting light of the first color, a second current source being connected to at least one LED emitting light of the second color, a third current source being connected to at least one LED emitting light of the third color, the current sources for controlling a brightness level of each color; at least one optical sensor connected to the support structure, the at least one optical sensor detecting a light output of a cluster when at least one LED in a cluster is energized; and a controller having a memory, the memory storing values for controlling an output current magnitude of each of the current sources so that a light output of the light source system has characteristics set by the values stored in the memory, the controller for calibrating a white point for all clusters by energizing LEDs within selected clusters and adjusting currents through LEDs in the selected clusters to cause a light output of each cluster to more closely match a target white point for that cluster based on values stored in the memory, wherein the controller is configured to perform the calibrating at various times over a lifetime of the light source system to offset degradation in the LEDs. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
-
-
20. A calibration method performed by a liquid crystal display (LCD) system comprising:
-
energizing different color light emitting diodes (LEDs) in a plurality of clusters of LEDs, the plurality of clusters forming a backlight for the LCD; optically sensing a white point of each cluster as LEDs in each cluster are energized and generating signals corresponding to a sensed white point, the optically sensing performed by an optical sensor mounted within the LCD system; addressing a memory to obtain a previously stored target white point for each cluster being sensed; adjusting currents to energized LEDs in each cluster to cause the white point of each cluster to substantially match the target white point for that cluster stored in the memory; storing values corresponding to currents used to cause the white point of each cluster to substantially match the target white point for that cluster; and periodically optically sensing the white point of each cluster at various times over a lifetime of the light source system, adjusting currents to energized LEDs in each cluster to cause the white point of each cluster to substantially match the target white point for that cluster stored in the memory, and storing values corresponding to currents used to cause the white point of each cluster to substantially match the target white point for that cluster to offset degradation in the LEDs. - View Dependent Claims (21, 22, 23, 24, 25, 26)
-
-
27. A light emitting diode (LED) light source system comprising:
-
a support structure; clusters of LEDs mounted on the support structure in an array, the LEDs in each cluster including at least a first LED for emitting light of a first color, a second LED for emitting light of a second color, and a third LED emitting light of a third color; each cluster having at least two LEDs emitting light of the first color; a first LED emitting light of the first color in a first cluster being connected in series with a second LED emitting light of the first color in a second cluster so that an open-circuit failure of either the first LED or the second LED will not result in an energizing current being removed from one or more other LEDs emitting light of the first color in the first cluster or the second cluster. - View Dependent Claims (28, 29, 30)
-
Specification