Spot positioning control for display tubes

Claim 3

A method as defined in claim 1, in which the beam is an electron beam in a cathode ray tube and the grating extends over a part of the cathode ray tube screen.

Claim 4

A method in accordance with claim 1, in which the auxiliary line is spaced from the first grating line by at least the predetermined fraction of the grating pitch, and in which the initial progressive deflection of the beam continues until the intersection of the beam with the said auxiliary line is sensed, whereupon the progressive beam deflection is stopped and the deflection of the beam to shift its intersection with the grating by the integral multiple of the grating pitch takes place.

Claim 5

A method in accordance with claim 1, in which the initial progressive deflection of the beam continues from the beam position outside the main grating area until sensing of the intersection of the beam with the first grating line takes place, and in which the beam is thereupon deflected along the same path, backwards or forwards, by an amount such as to displace the beam from a grating line by the predetermined fraction of the grating pitch, the beam being then deflected through the integral multiple of the grating pitch.

Claim 6

A method in accordance with claim 1, including means operative when the said further progressive deflection of the beam has been stopped to deflect the beam by a required portion of a grating pitch to provide fine positioning of the beam between the grating lines.

Claim 7

A method in accordance with claim 1, including blanking the beam prior to its deflection to shift its intersection with the grating by a required integral multiple of the grating pitch and brightening the beam prior to the subsequent progressive deflection of the beam to permit its intersection with a grating line to be sensed.

Claim 8

A light-spot positioning system in which a beam is angularly deflected to cause a light spot to traverse a grating of parallel lines, the system comprising: beam-deflecting means for progressively deflecting a beam in a required direction to progressively displace the point of intersection of the beam with the grating; first beam-positioning means for adjusting the beam position, in the said direction, by an amount such that the beam intersection with the grating moves through a fraction of a grating pitch; second beam-positioning means for positioning the beam so as to displace its point of intersection with the grating in the desired direction through a distance equal to an integral multiple of the grating pitch; detecting means for sensing the intersection of the beam with a grating line; and sequencing means whereby initially the beam is positioned at least a predetermined fraction of the grating pitch from a grating line, by progressive deflection of the beam by the beam-deflecting means until the detecting means senses the intersection of the beam with an auxiliary line preceding the grating in the direction of travel of the beam and spaced therefrom by said predetermined fraction of the grating pitch, after which the second beam-positioning means adjusts the beam position in the said direction by a predetermined integral multiple of the grating pitch, and thereafter the beamdeflecting means progressively deflects the beam until stopped by the action of the detector means on sensing the next intersection of the beam with a grating line.

Claim 9

A light-spot positioning system in which a beam is angularly deflected to cause a light spot to traverse a grating of parallel lines, the system comprising: beam-deflecting means for progressively deflecting a beam in a required direction to progressively displace the point of intersection of the beam with the grating; first beam-positioning means for adjusting the beam position, in the said direction, by an amount such that the beam intersection with the grating moves through a fraction of a grating pitch; second beam-positioning means for positioning the beam so as to displace its point of intersection with the grating in the desired direction through a distance equal to an integral multiple of the grating pitch; detecting means for sensing the intersection of the beam with a grating line; and sequencing means whereby initially the beam is positioned at least a predetermined fraction of the grating pitch from a grating line, by progressive deflection of the beam by the beam-deflecting means until the detecting means senses the intersection of the beam with an auxiliary line preceding the grating in the direction of travel of the beam and spaced therefrom by said predetermined fraction of the grating pitch, after which the second beam-positioning means adjusts the beam position in the said direction by a predetermined integral multiple of the grating pitch, and thereafter the beamdeflecting means progressively deflects the beam until stopped by the action of the detector means on sensing the next intersection of the beam with a grating line.

Claim 10

A system as defined in claim 7, in which the grating is formed on the screen of a cathode ray tube and the beam is an electron beam within the cathode ray tube which traverses the grating during deflection of the beam.

Claim 11

A system in accordAnce with claim 8, in which the second beam positioning means includes a digital-to-analogue converter.

Claim 12

A system in accordance with claim 7, further including an intensity control means for brightening and blanking the said beam, the sequencing means being such that the intensity control means blanks the beam prior to the adjustment of the beam position by the second beam-positioning means and thereafter brightens the beam prior to its progressive deflection by the beam-deflecting means.

Claim 13

A system in accordance with claim 7, for providing coarse positioning of the beam over the tube surface, further including a fine beam-position control circuit for positioning the beam between two grating lines, the sequencing means acting to bring the fine positioning circuit into operation when the detecting means senses the intersection of the beam with a grating line at the end of the coarse positioning of the beam.

Claim 14

A light-spot positioning system in which a beam is angularly deflected to cause a light spot to traverse a grating of parallel lines, the system comprising: beam-deflecting means for progressively deflecting a beam in a required direction to progressively displace the point of intersection of the beam with the grating; first beam-positioning means for adjusting the beam position, in the said direction, by an amount such that the beam intersection with the grating moves through a fraction of a grating pitch; second beam-positioning means for positioning the beam so as to displace its point of intersection with the grating in the desired direction through a distance equal to an integral multiple of the grating pitch; detecting means for sensing the intersection of the beam with a grating line; and sequencing means whereby initially the beam is progressively deflected by the beam-deflecting means until the detecting means senses the intersection of the beam with a first grating line and the beam is then positioned a predetermined fraction of the grating pitch from the grating line, after which the second beam-positioning means adjusts the beam position in the said direction by a predetermined integral multiple of the grating pitch, and thereafter the beam-deflecting means progressively deflects the beam until stopped by the action of the detector means on sensing the next intersection of the beam with a grating line.

Claim 15

A light-spot positioning system in which a beam is angularly deflected to cause a light spot to traverse a grating of parallel lines, the system comprising: beam-deflecting means for progressively deflecting a beam in a required direction to progressively displace the point of intersection of the beam with the grating; first beam-positioning means for adjusting the beam position, in the said direction, by an amount such that the beam intersection with the grating moves through a fraction of a grating pitch; second beam-positioning means for positioning the beam so as to displace its point of intersection with the grating in the desired direction through a distance equal to an integral multiple of the grating pitch; detecting means for sensing the intersection of the beam with a grating line; and sequencing means whereby initially the beam is progressively deflected by the beam-deflecting means until the detecting means senses the intersection of the beam with a first grating line and the beam is then positioned a predetermined fraction of the grating pitch from the grating line, after which the second beam-positioning means adjusts the beam position in the said direction by a predetermined integral multiple of the grating pitch, and thereafter the beam-deflecting means progressively deflects the beam until stopped by the action of the detector means on sensing the next intersection of the beam with a grating line.

Claim 16

A system as defined in claim 12 in which the grating is formed on the screen of a cathode ray tube and the beam is an electron beam within the cathode ray tube which traverses the grating during deflection of the beam.

Claim 17

A system in accordance with claim 13, in which the second beam positioning means includes a digital-to-analogue converter.

Claim 18

A system in accordance with claim 12, further including an intensity control means for brightening and blanking the said beam, the sequencing means being such that the intensity control means blanks the beam prior to the adjustment of the beam position by the second beam-positioning means and thereafter brightens the beam prior to its progressive deflection by the beam-deflecting means.

Claim 19

A system in accordance with claim 12, for providing coarse positioning of the beam over the tube surface, further including a fine beam-position control circuit for positioning the beam between two grating lines, the sequencing means acting to bring the fine positioning circuit into operation when the detecting means senses the intersection of the beam with a grating line at the end of the coarse positioning of the beam.

Claim 20

A system in accordance with claim 13, including means for initially applying to the beam position a bias of an amount corresponding to a beam deflection at the screen of a predetermined fraction of the grating pitch, the apparatus including means for removing this bias when the detecting means indicates that it has sensed the intersection of the beam with the first grating line.