Moire reducing apparatus

Claim 2

A moire reducing apparatus comprising: test signal generating means for generating a test signal which is synchronized with a vertical interval pulse, and suppling the test signal to a CRT; light emission detecting means for detecting a scanning position of the test signal output by said test signal generating means, at the CRT; calculation means for detecting an actual screen display height from an output of said light emission detecting means, and calculating a shift amount of scanning lines required for reducing moire; DC voltage generating means for generating a DC voltage which is synchronized with a vertical synchronizing signal, based on an output of said calculation means; vertical amplitude control means for suppling a DC voltage for adjusting the screen display height in a vertical direction; vertical deflection means for generating a saw-tooth wave for deflecting electron beams in the vertical direction, by using an output voltage of said vertical amplitude control means and the vertical synchronizing signal; and voltage adding means for adding an output of said DC voltage generating means to an output of said vertical deflection means.

Claim 3

A moire reducing apparatus according to claim 1, wherein said light emission detecting means comprises: a light emitting element which is applied to at least one portion of a shadow mask inside the CRT on the side of an electron gun, said light emitting element having a predetermined length in the vertical direction; and a light receiving element for detecting light emission of said light emitting element.

Claim 4

A moire reducing apparatus according to claim 1, wherein said test signal generating means generates a test signal which is synchronized with the vertical interval pulse and which is used for detecting at least a start and end of a video period.

Claim 5

A moire reducing apparatus according to claim 1, wherein said light emission detecting means is a light receiving element which detects light emission transmitted through a face of the CRT.

Claim 6

A moire reducing apparatus comprising: test signal generating means for generating a test signal which is synchronized with a vertical interval pulse, and suppling the test signal to a CRT; light emission detecting means for detecting a scanning position of the test signal output by said test signal generating means, at the CRT; signal system determining means for determining a signal system from a vertical synchronizing signal and a horizontal synchronizing signal; calculation means for calculating a shift amount of scanning lines required for reducing moire from an output of said light emission detecting means and an output of said signal system determining means; DC voltage generating means for generating a DC voltage which is synchronized with the vertical synchronizing signal, based on an output of said calculation means; vertical amplitude control means for suppling a DC voltage for adjusting a screen display height in a vertical direction; vertical deflection means for generating a saw-tooth wave for deflecting electron beams in the vertical direction, by using an output voltage of said vertical amplitude control means and the vertical synchronizing signal; and voltage adding means for adding an output of said DC voltage generating means to an output of said vertical deflection means.

Claim 7

A moire reducing apparatus comprising: test signal generating means for generating a test signal which is synchronized with a vertical interval pulse, and suppling the test signal to a CRT; light emission detecting means for detecting a scanning position of the test signal output by said test signal generating means, at the CRT; signal system determining means for determining a signal system from a vertical synchronizing signal and a horizontal synchronizing signal; calculation means for calculating a shift amount of scanning lines required for reducing moire from an output of said light emission detecting means and an output of said signal system determining means; DC voltage generating means for generating a DC voltage which is synchronized with the vertical synchronizing signal, based on an output of said calculation means; vertical amplitude control means for suppling a DC voltage for adjusting a screen display height in a vertical direction; vertical deflection means for generating a saw-tooth wave for deflecting electron beams in the vertical direction, by using an output voltage of said vertical amplitude control means and the vertical synchronizing signal; and voltage adding means for adding an output of said DC voltage generating means to an output of said vertical deflection means.

Claim 8

A moire reducing apparatus according to claim 5, wherein said signal system determining means detects a frequency of the horizontal synchronizing signal and a frequency of the vertical synchronizing signal, and detects a polarity of an input signal, thereby determining a signal system of the input signal.

Claim 9

A moire reducing apparatus according to claim 5, wherein said signal system determining means detects a frequency of the horizontal synchronizing signal and a frequency of the vertical synchronizing signal, and detects an interval period of a vertical interval pulse, thereby determining a signal system of an input signal.

Claim 10

A moire reducing apparatus according to claim 5, wherein said light emission detecting means comprises: a light emitting element which is applied to at least one portion of a shadow mask inside the CRT on the side of an electron gun, said light emitting element having a predetermined length in the vertical direction; and a light receiving element for detecting light emission of said light emitting element.

Claim 11

A moire reducing apparatus comprising: test signal generating means for generating a test signal which is synchronized with a vertical interval pulse, and suppling the test signal to a CRT; light emission detecting means for detecting a scanning position of the test signal output by said test signal generating means, at the CRT; gate means for selectively outputting an output of said light emission detecting means; calculation means for detecting an actual screen display height from an output of said gate means, and calculating a shift amount of scanning lines required for reducing moire; moire correcting waveform generating means for generating a correction voltage signal which is synchronized with a vertical synchronizing signal, based on an output of said calculation means; vertical amplitude control means for suppling a DC voltage for adjusting the screen display height in a vertical direction; vertical deflection means for generating a saw-tooth wave for deflecting electron beams in the vertical direction, by using an output voltage of said vertical amplitude control means and the vertical synchronizing signal; and voltage adding means for adding an output of said moire correcting waveform generating means to an output of said vertical deflection means, and wherein said light emission detecting means has: light emitting elements which are applied to at least two different positions of a shadow mask inside the CRT on the side of an electron gun; and light receiving elements for detecting light emission of said light emitting elements.

Claim 12

A moire reducing apparatus comprising: test signal generating means for generating a test signal which is synchronized with a vertical interval pulse, and suppling the test signal to a CRT; light emission detecting means for detecting a scanning position of the test signal output by said test signal generating means, at the CRT; gate means for selectively outputting an output of said light emission detecting means; calculation means for detecting an actual screen display height from an output of said gate means, and calculating a shift amount of scanning lines required for reducing moire; moire correcting waveform generating means for generating a correction voltage signal which is synchronized with a vertical synchronizing signal, based on an output of said calculation means; vertical amplitude control means for suppling a DC voltage for adjusting the screen display height in a vertical direction; vertical deflection means for generating a saw-tooth wave for deflecting electron beams in the vertical direction, by using an output voltage of said vertical amplitude control means and the vertical synchronizing signal; and voltage adding means for adding an output of said moire correcting waveform generating means to an output of said vertical deflection means, and wherein said light emission detecting means has: light emitting elements which are applied to at least two different positions of a shadow mask inside the CRT on the side of an electron gun; and light receiving elements for detecting light emission of said light emitting elements.

Claim 13

A moire reducing apparatus according to claim 9, wherein said gate means selectively outputs only even-numbered pulses or only odd-numbered pulses among pulses in a pulse string which is supplied from said light emission detecting means in one vertical scanning period, in accordance with a control signal supplied from an outside.

Claim 14

A moire reducing apparatus comprising: test signal generating means for generating a test signal which is synchronized with a vertical interval pulse, and suppling the test signal to a CRT; light emission detecting means for detecting a scanning position of the test signal output by said test signal generating means, at the CRT; mask means which, in accordance with a mask control signal, masks an output of said light emission detecting means in a predetermined time period; calculation means for detecting an actual screen display height from an output of said mask means, and calculating a shift amount of scanning lines required for reducing moire; moire correcting waveform generating means for generating a correction voltage signal which is synchronized with a vertical synchronizing signal, based on an output of said calculation means; vertical amplitude control means for suppling a DC voltage for adjusting the screen display height in a vertical direction; vertical deflection means for generating a saw-tooth wave for deflecting electron beams in the vertical direction, by using an output voltage of said vertical amplitude control means and the vertical synchronizing signal; and voltage adding means for adding an output of said moire correcting waveform generating means to an output of said vertical deflection means, and wherein said test signal generating means generates a test signal obtained by synthesizing a first test signal which is synchronized with at least the vertical interval pulse and which is used for detecting a start and end of a video period, with one set of second test signals which are synchronized with the vertical interval pulse, time intervals of said second test signals being shorter than said first test signal.

Claim 15

A moire reducing apparatus comprising: test signal generating means for generating a test signal which is synchronized with a vertical interval pulse, and suppling the test signal to a CRT; light emission detecting means for detecting a scanning position of the test signal output by said test signal generating means, at the CRT; mask means which, in accordance with a mask control signal, masks an output of said light emission detecting means in a predetermined time period; calculation means for detecting an actual screen display height from an output of said mask means, and calculating a shift amount of scanning lines required for reducing moire; moire correcting waveform generating means for generating a correction voltage signal which is synchronized with a vertical synchronizing signal, based on an output of said calculation means; vertical amplitude control means for suppling a DC voltage for adjusting the screen display height in a vertical direction; vertical deflection means for generating a saw-tooth wave for deflecting electron beams in the vertical direction, by using an output voltage of said vertical amplitude control means and the vertical synchronizing signal; and voltage adding means for adding an output of said moire correcting waveform generating means to an output of said vertical deflection means, and wherein said test signal generating means generates a test signal obtained by synthesizing a first test signal which is synchronized with at least the vertical interval pulse and which is used for detecting a start and end of a video period, with one set of second test signals which are synchronized with the vertical interval pulse, time intervals of said second test signals being shorter than said first test signal.

Claim 16

A moire reducing apparatus according to claim 11, wherein said light emission detecting means has: a light emitting element which is applied to at least one portion of a shadow mask inside the CRT on the side of an electron gun, said light emitting element having a predetermined length in the vertical direction; and a light receiving element for detecting light emission of said light emitting element.