Computer graphics processing and selective visual display system – Plural physical display element control system – Segmented display elements
Reexamination Certificate
2000-11-09
2003-09-30
Chang, Kent (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Segmented display elements
C345S046000, C345S082000, C345S083000, C257S086000, C250S552000
Reexamination Certificate
active
06628249
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a light emitting apparatus and a method for driving the light emitting LED apparatus. The present invention also relates to a display apparatus including the light emitting apparatus.
2. Description of the Related Art
FIG. 20
illustrates a conventional LED driving apparatus. In the conventional LED driving apparatus, a driving current i corresponding to an output establishment value p is applied from a power source
191
to an LED device
192
to drive the LED device
192
. The emission intensity of the LED device
192
is controlled by changing the value of the driving current i. In general, the color of light emitted from conventional LED devices does not depend on the value of a driving current. Thus, the emission intensity, of conventional LED devices is changed by control of the driving current value while maintaining the color of light emitted from the LED devices.
The emission intensity of conventional LED devices can be solely changed by control of the driving current value, since the light color of the conventional LED devices is not affected by a change in the driving current value. However, there is another type of LED device having a light color which is altered by a change in the driving current value. When such an LED device is driven by a driving apparatus as shown in
FIG. 20
, the light color of the LED device is changed along with the emission intensity control thereof. Thus, a desired emission intensity control cannot be conducted.
Conventional AlGaAs semiconductor light emitting devices have a phenomenon In which the wavelength of light emitted therefrom becomes longer as a driving current is Increased (red shift phenomenon). The red shift phenomenon occurs as follows. The light emitting device is heated by supplied power, and the temperature of the device is proportional to the average supplied power. The increased temperature causes the bandgap of the active layer to be reduced, so that the wavelength of light emitted from the device becomes longer (red shift). In other words, the emission intensity and emission wavelength of the light emitting device having the red shift phenomenon are determined by the average power applied to the device. It is not possible to separately control the emission wavelength and emission power of the AlGaAs semiconductor light emitting device using two parameters (peak value and average power) of a driving current pulse.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a light emitting apparatus comprises: a light emitting section for emitting light, a color of the light being blue shifted with a value of a driving current; and a driving section for driving the light emitting section so that the light emitting section emits light having a desired color and a desired intensity, by generating the driving current based on a signal designating the desired color and a signal designating the desired intensity and by applying the driving current to the light emitting section.
In one embodiment of this invention, the driving section comprises: a converting section for converting the color-designating signal to a signal designating a current value in accordance with current versus emission wavelength characteristics of the light emitting section: a calculating section for calculating a signal designating a duty based on the intensity-designating signal and the current value-designating signal, in such a manner that the product of a current value designated by the current value-designating signal and u duty corresponds to the intensity designated by the intensity-designating signal; and e section for generating, as the driving current, a pulse current having the current value and the duty In accordance with the respective current value-designating signal and duty-designating signal.
In one embodiment of this invention, the light emitting section is an LED device.
In one embodiment of this invention, the light emitting section is an LED bullet comprising: an LED device; and a fluorescent excited by light emitted by the LED device to emit light.
In one embodiment of this invention, when the driving current value is changed, a change in an emission wavelength of the LED bullet is larger than a change in an emission wavelength of the LED device.
In one embodiment of this invention, the light emitting apparatus comprises a plurality of the light emitting sections: and a plurality of the driving sections respectively corresponding to the plurality of the light emitting sections. A color and intensity of light emitted by each of the plurality of the light emitting sections is controlled by a corresponding one of the plurality of the driving sections.
In one embodiment of this invention, the color-designating signal is a color signal for designating a color of light to be emitted by the LED device, and the intensity-designating signal is an intensity signal for-designating an intensity of the light to be emitted by the LED device.
In one embodiment of this invention, the color-designating signal is a chromaticity signal for designating a color of light to be emitted by the LED bullet, and the intensity-designating signal is a luminance signal for designating an intensity of the light to be emitted by the LED bullet.
In one embodiment of this Invention, the LED device comprises: an InGaN active layer and an AlGaN layer having two layers, provided on the InGaN active layer. One of the two layers is a first AlGaN layer contacting the InGaN active layer, and the other of the two layers of the AlGaN layer is a second AlGaN layer provided on the first AlGaN layer, the first AlGaN layer is produced at substantially the same growth temperature as the InGaN active layer, and the second AlGaN layer is produced at a growth temperature higher than the growth temperature of the first AlGaN layer.
In one embodiment of this invention, the LED device comprises: an InGaN active layer; and an AlGaN layer having two layers, provided on the InGaN active layer. One of the two layers is a first AlGaN layer contacting the InGaN active layer, and the other of the two layers of the AlGaN layer is a second AlGaN layer provided on the first AlGaN layer, the first AlGaN layer is produced at substantially the same growth temperature as the InGaN active layer, and the second AlGaN layer is produced at a growth temperature higher than the growth temperature of the first AlGaN layer.
According to another aspect of the present invention, a method for driving a light emitting apparatus is provided. The apparatus comprises: a light emitting section for emitting light, a color of the light being blue shifted with a value of a driving current; and a driving section for driving the light emitting section. The method comprises the steps of: receiving a signal designating a desired color and a signal designating a desired intensity; generating the driving current based on the color-designating signal and the intensity-designating signal; and applying the driving current to the light emitting section so that the light emitting section emits light having the desired color and the desired intensity.
In one embodiment of this invention, the method further comprises the steps of: converting the color-designating signal to a signal designating a current value in accordance-with current versus emission wavelength characteristics of the light emitting section; calculating a signal designating a duty based on the intensity-designating signal and the current- value-designating signal, in such a manner that the product of a current value designated by the current value-designating signal and the duty corresponds to the intensity designated by the intensity-designating signal; and generating as the driving current a pulse current having the current value and the duty in accordance with the respective current value-designating signal and duty-designating signal.
In one embodiment of this invention, the light emitting section is an LED device.
In one embodiment of this invention, the
Ito Shigetoshi
Kamikawa Takeshi
Taneya Mototaka
Chang Kent
Morrison & Foerster / LLP
Sheng Tom
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