Spiral scan display apparatus with transient suppression means

Claim 2

In display apparatus wherein display writing means traces a circular path whose radius is periodically changed so as to scan a display area, and wherein the display writing means responds to stored video data signals to produce a visual presentation on the display area, the improvement which comprises: blanking means for alternately blanking the display writing means for an interval of time immediately following each change in radius of the circular path, and then unblanking the display writing means for at least a complete revolution; deflection means for changing the radius of the circular path traced by the display writing means only at the beginning of the intervals during which the display writing means is blanked; and data means for sequentially supplying video data signals to the display writing means only during unblanked intervals and in synchronism with movement of the display writing means.

Claim 3

The display apparatus of claim 1 wherein said data means comprises memory means for storing video data, and memory access means for retrieving the video data in the required order only during unblanked intervals of the display writing means.

Claim 4

The display apparatus of claim 2 wherein said memory access means addresses locations in said memory means in a predetermined sequence, and wherein successively required video data signals are stored in successively addressed memory locations.

Claim 5

The display apparatus of claim 3 wherein: the display area is on the face of a cathode ray tube; the display writing means comprises an electron beam in the cathode ray tube; the electron beam is blanked through a predetermined angle after each complete unblanked revolution; and video data are retrieved from said memory means at a uniform rate except at the end of each complete unblanked revolution when a retrieval delay equal to the blanked interval is provided.

Claim 8

The method of claim 5 wherein the step of supplying video data comprises the further steps of: storing video data for a visual presentation in successively addressed memory locations in the order required by the unblanked display writing means; and retrieving the video data from successively addressed memory locations at a uniform rate except immediately following each change in radius of the circular path when a retrieval delay equal to the blanked interval is provided.

Claim 9

Spiral scan display apparatus for generating a visual presentation from stored video data comprising: a display device including a display area and display writing means which can be positioned at any point on the display area by appropriate deflection signals, the display writing means being responsive to video data signals to produce a visual presentation; deflection means for supplying deflection signals which cause the display writing means to trace a circular path; radius control means for changing the radius of the circular path at intervals which exceed by at least a blanking interval the time required for a complete revolution of the display writing means, whereby the display writing means scans the entire display area; blanking means for alternately preventing the display writing means from generating a visual presentation during the blanking interval immediately following each change in radius of the circular path, and then permitting generation of a visual presentation for at least a complete revolution of the display writing means; memory means including a plurality of memory locations for storing video data; data retrieval means for retrieving video data from said memory means in the order required by the display writing means, the retrieved data being only data sequentially required during unblanked intervals; and means for supplying video data signals indicative of the retrieved data to the display writing means.

Claim 10

Spiral scan display apparatus for generating a visual presentation from stored video data comprising: a display device including a display area and display writing means which can be positioned at any point on the display area by appropriate deflection signals, the display writing means being responsive to video data signals to produce a visual presentation; deflection means for supplying deflection signals which cause the display writing means to trace a circular path; radius control means for changing the radius of the circular path at intervals which exceed by at least a blanking interval the time required for a complete revolution of the display writing means, whereby the display writing means scans the entire display area; blanking means for alternately preventing the display writing means from generating a visual presentation during the blanking interval immediately following each change in radius of the circular path, and then permitting generation of a visual presentation for at least a complete revolution of the display writing means; memory means including a plurality of memory locations for storing video data; data retrieval means for retrieving video data from said memory means in the order required by the display writing means, the retrieved data being only data sequentially required during unblanked intervals; and means for supplying video data signals indicative of the retrieved data to the display writing means.

Claim 11

The spiral scan display apparatus of claim 7 wherein: said data retrieval means successively addresses the plurality of memory locations in a predetermined order for retrieving video data therefrom; and video data are stored in successively addressed memory locations in the order required by the display writing means.

Claim 12

The spiral scan display apparatus of claim 8 wherein: said display device is a cathode ray tube and the display writing means is an electron beam in the cathode ray tube; and video data are retrieved from said memory means at a uniform rate except immediately following each change in radius of the circular path when a retrieval delay equal to the blanking interval is provided.