US 5,664,858 AGranted

Method and apparatus for pre-compensating an asymmetrical picture in a projection system for displaying a picture

AssigneeDaewoo Electronics Co., Ltd.

InventorSeong-Jae Woo

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Abstract

An apparatus and a method in a projector in which in order to project a clear picture onto a screen without the occurrence of the keystoning, an asymmetrical picture is pre-compensated is disclosed. In the apparatus and method for pre-compensating an asymmetrical picture in a projector, when the projection lens of the projector is arranged at an upward or a downward projection angle, regardless of the projection angle, a trapezoidal error of the picture projected on the screen is pre-compensated in response to the projection angle setting signal from the projection angle setting section, so that the picture is normally projected onto the screen (e.g., a picture in the shape of a rectangle). Consequently, the performance or structural flexibility of the projector is enhanced by using digital circuits and softwares therefor.

Claims22

Dependent claims

An apparatus for pre-compensating an asymmetrical picture in a projection system for displaying a picture, said apparatus comprising:

means for setting an projection angle and providing a projection angle setting signal when a central axis of a projection lens installed in a projector for projecting a magnified picture on a screen is arranged at an upward or downward projection angle with respect to the screen;
controlling means for providing a control signal in order to control an operation of pre-compensating an asymmetry of the picture which is to be projected on the screen on the basis of the projection angle setting signal of said projection angle setting means;
control clock generating means for providing a record/read clock signal and a data conversion output signal in accordance with the control signal from said controlling means while receiving a main clock signal and a digital signal process clock signal, the write clock signal relating to a process for deleting pixels of the picture signal data;
first switching means for switching the record/read clock signal from said control clock generating means and for providing a switched write clock signal or a switched read clock signal in accordance with the control signal from said controlling means while receiving the digital signal process clock signal, the switched write clock signal relating to the process for deleting pixels of the picture signal data;
memory section for recording the picture signal data which has pixels deleted therefrom and is provided in response to a horizontal synchronizing signal, said memory section outputting the recorded picture signal data while receiving the switched write clock signal or the switched read clock signal from said first switching means;
second switching means for switching in accordance with the control signal from said controlling means between the picture signal data outputted from said memory section in response to the switched read clock signal from said first switching means, and blanking data filled in blanking areas set prior to and after the picture signal data having pixels deleted therefrom, and for providing a switched picture signal data or a switched blanking data;
third switching means for switching the data conversion output signal from said control clock generating means and providing a switched data conversion output signal in accordance with the control signal from said controlling means while receiving the digital signal process clock signal;
and
data converting means for inputting the switched picture signal data or the switched blanking data from said second switching means in order to form the picture signal data having blanking data added thereto, and for converting the picture signal data having blanking data added thereto into an analog signal, after a first period, in response to the switched data conversion output signal from said third switching means, in order to provide a converted picture signal data.

6 more elements

A method for pre-compensating an asymmetrical picture in a projection system for displaying a picture, said method comprising the steps of:

(i) inputting a key data corresponding to a projection angle setting signal when a central axis of a projection lens installed in a projector for projecting a magnified picture on a screen is arranged at an upward or downward projection angle with respect to the screen;
(ii) calculating on the basis of the key data inputted in step (i) parameters related to an operation for pre-compensating an asymmetry of a picture which is to be projected onto the screen;
(iii) generating a write clock signal at a leading edge of a main clock signal in accordance with the amount of compensation determined in step (ii);
(iv) recording a picture signal data with pixels deleted therefrom in the line of unit in response to the write clock signal generated in step (iii) in order to generate a picture reversely shaped to the picture which is to be projected onto the screen;
(v) generating a read clock signal at a leading edge of the main clock signal after a first period multiplied by 2 in order to read out the picture signal data;
(vi) adding a blanking data to parts of the read picture signal data with pixels deleted therefrom in response to the read clock signal generated in step (v);
and
(vii) converting in response to a data conversion output signal the picture signal data having the blanking data added thereto generated in step (vi) into an analog signal and generating a converted picture signal data.

5 more elements

Dependencies are inferred from the claim text.