Computer graphics processing and selective visual display system – Data responsive crt display control
Reexamination Certificate
1997-01-15
2001-03-20
Saras, Steven (Department: 2675)
Computer graphics processing and selective visual display system
Data responsive crt display control
C381S071100, C381S071300
Reexamination Certificate
active
06204830
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the technologies of picture and sound reproduction and applies to a monitor comprising a picture tube and an audio reproduction device. The invention is applicable especially in connection with a picture tube for enhanced resolution and therefore with a fine pitch shadow mask or screen respectively.
BACKGROUND OF THE INVENTION
The coexistence of a picture tube and an audio reproduction device in the same housing can lead to visual and audible problems when the audio output power increases and if there is tight mechanical coupling between the picture tube and parts vibrating in response to the electrical audio power.
One of these mentioned problems is audible buzz. The buzzing sound is in most cases created by vibration of the shadow mask or of the shadow mask frame when the audio output level is high and when the momentary audio frequency is at or near the self-resonant frequency of the shadow mask or the mask/frame arrangement.
Another problem is the unwanted modulation of the electron beam intensity due to the vibration of the shadow mask or its components caused by insufficient mechanical decoupling from the sound reproduction equipment as described above. This leads to brightness variations and/or colour purity imperfections appearing in synchronism with the momentary audio frequency. It is obvious that this mentioned problem is worse at or near the self-resonant frequency of the mask or the mask/frame arrangement.
Unfortunately, this second problem is further increased when for a high resolution monitor a picture tube with a fine pitch is selected because the same vibration amplitude of shadow mask components, e.g. wires in case of a Trinitron® type, causes a larger relative landing error on the screen.
SUMMARY OF THE INVENTION
In the following we will call the unwanted brightness/colour variation “flicker”. The self-resonant frequency of the shadow mask or its components will be called self-resonant frequency of the picture tube because this value is fairly constant for a given type of picture tube. It is the object of this invention to reduce this secondly mentioned problem, the flicker, but naturally all measures against flicker also help against the firstly mentioned problem, i.e. buzz.
The invention relates to a monitor comprising a picture tube unit with a certain self-resonant frequency, a base and sound reproduction elements, characterized in that the picture tube unit includes a main sound reproduction element used to reproduce only audio frequencies deviating from the self-resonant frequency, and that the base has an additional sound reproduction element which is used for reproduction of sound frequencies at the self-resonant frequency.
According to the invention, sounds at or near the self-resonant frequency of the picture tube are reproduced through the base. This makes it possible to improve the decoupling between the audio sound pressure source and the picture tube.
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Nelson Alecia D.
Nokia Technology GmbH
Saras Steven
Ware Fressola Van der Sluys & Adolphson LLP
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