Automatic primary color convergence alignment system for projection television

• US 4,857,998 A
• Filed: 02/25/1988
• Issued: 08/15/1989
• Est. Priority Date: 02/26/1987
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Kataoka, Teruo, Tsujihara, Susumu
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): Svihla, Randall S.
• Application Number:
  US07/160,379
• Time in Patent Office: 537 Days
• Field of Search: 358/10, 358/56, 358/60, 358/64
• US Class Current: 348/747
• CPC Class Codes: H04N 17/04 for receivers
• CPC Class Codes: H04N 9/28 Arrangements for convergence or focusing
• CPC Class Codes: H04N 9/317 Convergence or focusing systems electronic adjustment of convergence H04N9/3185; convergence or focusing arrangements for cathode ray tubes H04N9/28; means for automatic focusing of projectors not peculiar to the presence of an electronic spatial light modulator G03B21/53
• CPC Class Codes: H04N 9/3194 including sensor feedback

Abstract

An automatic primary color component covergence alignment system for a color television display apparatus is presented whereby an alignment pattern is periodically displayed in peripheral regions of the television screen, in each of the primary colors during respective successive correction intervals, the pattern positioned such as to fall upon photo-sensitive devices disposed at the screen periphery. Adjustment of pattern position is executed during each correction interval, based on position data derived from output signals from the photo-sensitive devices, such as to align the alignment pattern with predetermined reference positions. During each period between these sets of correction intervals, the position data thus derived are held stored and are continuously utilized for controlling the deflection of respective electron beams used in generating the primary colors, to thereby implement automatic convergence alignment adjustment.

Claims

1. An automatic convergence alignment system for a color television display apparatus which displays a television picture on a screen as a combination of primary color components, comprising:

convergence alignment means operable for position adjustment of said primary color components of the television picture;

photodetection means disposed peripherally on said screen;

alignment pattern generating means for controlling said display apparatus to periodically display an alignment pattern on peripheral regions of said screen in each of said primary color components during respective successively occurring correction intervals, said alignment pattern being positioned to be incident on said photodetection means;

signal processing and memory means responsive to photoelectric transducer signals produced by said photodetection means by detection of said alignment pattern during each of said correction intervals for deriving position data for causing said convergence alignment means to align said alignment pattern with at least one predetermined reference position defined relative to said photodetection means, and for subsequently holding said position data and continuously supplying said position data to said convergence alignment means; and

detection period control means for controlling a detection period which is a repetition period of said corrections intervals.

2. An automatic convergence alignment system according to claim 1, in which said detection period control means functions to make said detection period relatively short during an initial interval of operation of said television display apparatus and to thereafter increase the duration of said detection period.

3. An automatic convergence alignment system according to claim 1, in which said detection period control means is controlled such as to vary said detection period in accordance with an anticipated amount of position deviation of said alignment pattern from said reference position.

4. An automatic convergence alignment system according to claim 1 in which said photodetection means comprises at least one photosensitive device formed of an array of photoelectric transducer elements, and in which said signal processing and memory means comprises circuit means coupled to receive photoelectric transducer signals produced from respective ones of said photoelectric transducer elements for deriving a detection output signal having a polarity and magnitude respectively representing a direction and amount of position deviation of said alignment pattern from said reference position, and in which said automatic convergence alignment system functions during each of said correction intervals to generate said position data as a data value, applied to control said convergence alignment means, which is varied until said detection output signal reaches zero and is thereafter held constant during a succeeding detection period.

5. An automatic convergence alignment system according to claim 4, in which said alignment pattern is displayed in each of successive fields of said picture during each of said correction intervals whereby said photoelectric transducer signals from said photoelectric transducer elements are generated as pulse trains, and in which said circuit means for deriving said detection output signal comprises means for deriving from said photoelectric transducer signals of said photoelectric transducer elements a deviation signal representing an amount of position deviation of said alignment pattern from said reference position, maximum amplitude detection means for detecting a maximum amplitude of said deviation signal and producing a DC signal level representing said maximum amplitude, minimum amplitude detection means for detecting a minimum amplitude of said deviation signal and producing a DC signal level representing said minimum amplitude, and signal summing means for summing said DC signal levels from said maximum amplitude detection means and minimum amplitude detection means to produce said detection output signal.

6. An automatic convergence alignment system according to claim 5, in which said deviation signal is derived as a difference signal between two signals respectively derived from photoelectric transducer signals produced by respective sets of said photoelectric transducer elements disposed symmetrically on opposing sides of said reference position.

7. An automatic convergence alignment system for a color television display apparatus which displays a television picture of a screen as a combination of primary color components, comprising:

convergence alignment means operable for position adjustment of said primary color components of the television picture;

photodetection means disposed peripherally on said screen;

alignment pattern generating means for controlling said display apparatus to periodically display an alignment pattern on peripheral regions of said screen in each of said primary color components during respective successively occurring correction intervals, said alignment pattern being positioned to be incident on said photodetection means; and

signal processing and memory means responsive to photoelectric transducer signals produced by said photodetection means by detection of said alignment pattern during each of said correction intervals for deriving position data for causing said convergence alignment means to align said alignment pattern with at least one predetermined reference position defined relative to said photodetection means, and for subsequently holding said position data and continuously supplying said position data to said convergence alignment means;

in which said photodetection means comprises at least one photosensitive device formed of an array of successively positioned photoelectric transducer elements disposed symmetrically about said reference position, and in which a higher degree of detection sensitivity is implemented for specific ones of said photoelectric transducer elements which are positioned closely adjacent to said reference position than the detection sensitivity of the remainder of said photoelectric transducer elements of said photosensitive device.

8. An automatic convergence alignment system for a color television display apparatus which displays a television picture on a screen as a combination of primary color components, comprising:

convergence alignment means operable for position adjustment of said primary color components of the television picture;

photodetection means disposed peripherally on said screen;

alignment pattern generating means for controlling said display apparatus to periodically display an alignment pattern on peripheral regions of said screen in each of said primary color components during respective successively occurring correction intervals, said alignment pattern being positioned to be incident on said photodetection means;

signal processing and memory means responsive to photoelectric transducer signals produced by said photodetection means by detection of said alignment pattern during each of said correction intervals for deriving position data for causing said convergence alignment means to align said alignment pattern with at least one predetermined reference position defined relative to said photodetection means, and for subsequently holding said position data and continuously supplying said position data to said convergence alignment means;

detection period control means for controlling a detection period which is a repetition period of said correction intervals; and

means for detecting whether or not a total amount of light received by said photodetection means exceeds a predetermined level, for producing an output signal in accordance with results of said detection and for controlling said detection period control means by said output signal to vary said detection period in accordance with said detection results.

9. An automatic convergence alignment system for a color television display apparatus which displays a television picture on a screen as a combination of primary color components, comprising:

convergence alignment means operable for position adjustment of said primary color components of the television picture;

first photodetection means disposed peripherally on a vertically extending side of said screen and second photodetection means disposed peripherally on a horizontally extending side of said screen, each said photodetection means comprising an array of photoelectric transducer elements;

alignment pattern generating means for controlling said display apparatus to periodically display an alignment pattern on peripheral regions of said screen in each of said primary color components during respective successively occurring correction intervals, first and second predetermined portions of said alignment pattern being positioned to be respectively incident on said first and second photodetection means; and

signal processing and memory means responsive to respective photoelectric transducer signals produced by said first and second photodetection means by detection of said first and second predetermined portions respectively of said alignment pattern during each of said correction intervals for deriving position data for causing said convergence alignment means to align said first and second predetermined portions of said alignment pattern with first and second predetermined reference positions, respectively, which are defined at respective central positions of said element arrays of said first and second photodetection means, and for subsequently holding said position data and continuously supplying said position data to said convergence alignment means.

10. An automatic convergence alignment system for a color television display apparatus which displays a television picture on a screen as a combination of primary color components, comprising:

convergence alignment means operable for position adjustment of said primary color components of the television picture;

photodetection means disposed peripherally on said screen;

alignment pattern generating means for controlling said display apparatus to periodically display an alignment pattern on peripheral regions of said screen in each of said primary color components during respective successively occurring correction intervals, said alignment pattern being positioned to be incident on said photodetection means; and

signal processing and memory means responsive to first and second photoelectric transducer signals respectively produced by two portions of said photodetection means disposed symmetrically about a reference position by detection of said alignment pattern during each of said correction intervals for detecting a difference between said first and second photoelectric transducer signals and deriving position data for causing said convergence alignment means to execute position correction of said alignment pattern such as to reduce said difference to zero, for thereby aligning said alignment pattern with said reference position, and for subsequently holding said position data and continuously supplying said position data to said convergence alignment means.

11. automatic convergence alignment system for a color television display apparatus which displays a television picture on a screen as a combination of primary color components, comprising:

convergence alignment means operable for position adjustment of said primary color components of the television picture;

photodetection means disposed peripherally on said screen;

alignment pattern generating means for controlling said display apparatus to periodically display an alignment pattern on peripheral regions of said screen in each of said primary color components during respective successively occurring correction intervals, said alignment pattern being positioned to be incident on said photodetection means;

signal processing and memory means responsive to photoelectric transducer signals produced by said photodetection means by detection of said alignment pattern during each of said correction intervals for deriving position data for causing said convergence alignment means to align said alignment pattern with at least one predetermined reference position defined relative to said photodetection means, and for subsequently holding said position data and continuously supplying said position data to said convergence alignment means; and

means for detecting whether or not a total amount of light received by said photodetection means exceeds a predetermined level, for producing an output signal in accordance with results of said detection and for controlling said signal processing and memory means by said output signal to inhibit signal processing operation by said signal processing and memory means when said predetermined level is exceeded.