Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-02-17
2002-09-03
Saras, Steven (Department: 2775)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S039000, C340S870030, C359S199200, C359S199200
Reexamination Certificate
active
06445369
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a dot matrix display system. More particularly, the invention relates to a dot matrix display system of light-emitting diodes to simultaneously display a visual image and transmit audio information from one location to another location.
BACKGROUND OF THE INVENTION
Light-emitting diodes (LEDs) are superior than incandescent lights because of LEDs' long life expectancy, high tolerance to humidity, low power consumption and minimal heat generation. LEDs are used in many message display boards, signal devices; and other means of illumination. LED array display board is a popular instrument for commercial usage. Many banks, shops and cinemas are willing to install one piece of it because of its versatility. LED array display board can be very bright and eye-catching. Thus, it is very suitable for advertising purpose. Also, unlike printed sign or logo, the message displayed on the LED array display board can be changed anytime. One can use it to tell people what is the most updated information in real-time. For example, the LED array display board is used in a bank to show the current stock market value, currency exchange rate and interests rate. It can also be used in a shop to tell people what open hours are and what the biggest bargain is today.
The features and functionality of a LED array display board also becomes more enriched. Scrolling, blinking, built-in character formats are just some basic functions. More powerful LED array display board even has a multi-color display. The resolution is enhanced by reducing the dot size and have the LED packed more closely. The size of the LED array also becomes larger and larger. The smallest LED array starts with a single line text display. But some huge LED array display boards can be taller than a man and have a multi-line text and even graphics display. Nevertheless, existing LED display board is limited only to visual message (or image) displays. It has never been used for other functions.
However, one important characteristic of LEDs is that they are semiconductor devices. and are capable of fast switching with the addition of appropriate electronics. Thus, it is possible to use a LED display system for both visual display and broadcast of audio information through LEDs if lights emitted from LEDs can be modulated and encoded.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to use LEDs as a communication device for displaying an image and transmitting audio information.
It is also an object of the present invention to provide a dot matrix display system using light-emitting diodes to display an image and to transmit audio information through light emitting diodes from one location to another location.
It is yet another object of the present invention to provide an information system for use in a wireless optical communication system.
The present invention discloses the use of LED lights for providing a visual signal in the form of visible light rays and for using the visible light rays to transmit and broadcast audio information. According to a first embodiment of the invention, a light emitting diode dot matrix display system for transmitting audio information from a first location to a second location comprises a transmitter at the first location and a receiver at the second location. The transmitter comprises at least one light emitting diode for producing the visible light rays, a power source for the light emitting diode, means for coupling the audio information to the light emitting diode and a modulator connected to the light emitting diode for modulating the frequency of ON and OFF periods of the light emitting diode. The light emitting diode dot matrix display system may further comprise an audio information source for providing the audio information. In a preferred embodiment of the invention a CD player or a cassette-player is used with the transmitter as the audio information source to provide the audio information. The modulator includes a voltage-controlled oscillator connected with the audio information source for modulating the frequency of the audio information so that a modulated carrier frequency is proportional to the amplitude of the audio information. It is preferred that a plurality of light emitting diodes are used to convert the modulated audio information into a train of ON/Off signals and to transmit thereof. The power source for the transmitter is a dc source, preferably with a voltage less than 10 volts. A buffer circuit is also used to drive the light emitting diode.
The receiver of the light emitting diode dot matrix display system comprises a photodetector for receiving the visible light rays emitted from the light emitting diode and a demodulator connected to the photodetector for demodulating the visible light rays to retrieve the audio information. The light emitting diode dot matrix display system may further comprise at the receiver a lens system for focusing the visible light rays onto the photodetector and a speaker connected to the demodulator for broadcasting the audio information. In an preferred embodiment of the invention, the photodiode is used as the photodetector for detecting the visual light rays from the transmitter and converting the same into an electrical signal. A limiting preamplifier is connected to the photodetector for amplifying the electrical signal. A virtual ground is provided with the limiting pre-amplifier for biasing and comparison. A data reproducing circuit is connected to the limiting pre-amplifier for producing rectangular pulses from the amplified electrical signal. A differentiator circuit is connected to the data reproducing circuit for producing pulses according to the rectangular pulses. A pulse generator converts the pulses from the differentiator circuit into sharp pulses, and an integrator and envelope detector thereafter demodulates the sharp pulses. A band-pass filter is connected to said integrator and envelope detector for smoothing out signal distortions therefrom to produce the audio information. Finally, a power amplifier is used to amplify the audio information from the band-pass filter.
In a second embodiment of the invention, the light emitting diode dot matrix display system for simultaneously displaying a visual signal and transmitting an audio signal comprises a dot matrix display panel having a row and a column of light emitting diodes, an interface circuit connected to the dot matrix display panel, a visual signal display controller connected to the interface circuit for controlling display of the visual signal on the display panel, an audio signal transmitter connected to the interface circuit for providing a modulated audio signal to the light emitting diodes, and a receiver for receiving light emitted from the light emitting diodes and retrieving the audio signal therefrom. The interface circuit includes a driver circuit for the light emitting diodes of the display panel. In a preferred embodiment of the invention, the visual signal display controller is an executive program executed on a computer. The interface circuit comprises a system control block connected to a parallel port of the computer for providing a timing control and maintaining a count of pulses of the modulated audio signal. An address generator is connected to the system control block for transforming frequency of the modulated audio signal to a scanning frequency for use in the row of light emitting diodes. A random access memory connected to the address generator contains design information of the visual signal to be displayed on the LED display panel. The interface circuit also has a PC data buffer connected to the parallel port of the computer, a column signal buffer connected between the address generator and the dot matrix display panel, and a row signal buffer connected between the random access memory and the dot matrix display panel. The audio signal transmitter comprises a voltage-controlled oscillator for varying the frequency of ON/OFF periods of the light emitting diode
Chan Chi-Ho
Ho Ka-Lim
Hong Michael Kin-Ming
Ko Lawrence Ming-Him
Kwan To-On
Kumar Srilakshmi K.
Pennie & Edmonds LLP
Saras Steven
The University of Hong Kong
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