EP0299666A2 — Scan conversion apparatus and method

Claim 1

Independent Claim 219 words

Scan conversion apparatus for a display system for displaying target data expressed in polar coordinates on a display screen having a matrix of pixels in cartesian coordinates and a refresh memory (39) having a matrix of storage locations corresponding respectively to the pixels, the storage locations being addressable in the cartesian coordinates, the polar coordinates being quantised in a plurality of discrete polar coordinate points corresponding respectively to a plurality of cartesian coordinate points, and each polar coordinate point having a distance (R) coordinate and an angle (theta) coordinate associated therewith and each cartesian coordinate point having an X-coordinate and a Y-coordinate associated therewith, some of the storage locations having addresses not addressable by said cartesian coordinate points , characterised in that the scan conversion apparatus for converting the polar coordinate points to the cartesian coordinate points comprises, scan converter means (26) for converting each polar coordinate point to a corresponding cartesian coordinate point, an R,theta table (29) having a plurality of locations corresponding to, and addressable by, the polar coordinate points, respectively, each location storing a fill signal representative of the unaddressable storage locations in the refresh memory (39) associated therewith, and fill means (32) responsive to the fill signal for accessing each unaddressable storage location and storing therein target data corresponding to the distance coordinate associated therewith.

Claim 2

Dependent Claim 219 words

Scan conversion apparatus for a display system for displaying target data expressed in polar coordinates on a display screen having a matrix of pixels in cartesian coordinates and a refresh memory (39) having a matrix of storage locations corresponding respectively to the pixels, the storage locations being addressable in the cartesian coordinates, the polar coordinates being quantised in a plurality of discrete polar coordinate points corresponding respectively to a plurality of cartesian coordinate points, and each polar coordinate point having a distance (R) coordinate and an angle (theta) coordinate associated therewith and each cartesian coordinate point having an X-coordinate and a Y-coordinate associated therewith, some of the storage locations having addresses not addressable by said cartesian coordinate points , characterised in that the scan conversion apparatus for converting the polar coordinate points to the cartesian coordinate points comprises, scan converter means (26) for converting each polar coordinate point to a corresponding cartesian coordinate point, an R,theta table (29) having a plurality of locations corresponding to, and addressable by, the polar coordinate points, respectively, each location storing a fill signal representative of the unaddressable storage locations in the refresh memory (39) associated therewith, and fill means (32) responsive to the fill signal for accessing each unaddressable storage location and storing therein target data corresponding to the distance coordinate associated therewith.

Claim 3

Dependent Claim 35 words

Apparatus according to claim 1, characterised in that the fill signal comprises a fill count signal representative of a number of unaddressable pixels to be filled associated with the current polar coordinate point being converted.

Claim 4

Dependent Claim 42 words

Apparatus according to claim 1 or 2, characterised in that the display screen (42) is divided into sectors and in that the fill means (32) comprises means for sequentially filling said unaddressable storage locations in a fill direction dependent on said sector.

Claim 5

Dependent Claim 134 words

Apparatus according to any of the preceding claims, characterised in that the fill means comprises: accessing means (35) for incrementing or decrementing said X or Y coordinate in accordance with the fill direction, thereby accessing the unaddressable storage locations, range conversion means (34) for adding or subtracting multiples of the sine or cosine of the angle coordinate of the polar coordinate being converted to the distance coordinate of the polar coordinate being converted to provide the distance coordinate associated with the unaddressable storage location being filled, in accordance with the sector in which the polar coordinate being converted resides, and fill data generating means (27, 28) responsive to the distance coordinate associated with the storage locations being filled for providing the target data corresponding thereto for storage in the unaddressable storage location being filled.

Claim 6

Dependent Claim 60 words

Apparatus according to claim 4, characterised in that the fill data generator means comprises: range sweep buffer means (27) for storing . target data associated with a range sweep at quantised distances thereof, and selector means (28) responsive to the distance coordinate associated with the unaddressable storage location being filled for accessing the target data corresponding to the distance coordinate.

Claim 7

Dependent Claim 45 words

Apparatus according to claim 4 or 5, characterised in that fill means includes: fill counter means (33) for receiving the fill count signal for loading therein, and decrementing means (35) for decrementing the fill counter means, thereby indexing the unaddressable storage locations to be filled.

Claim 8

Dependent Claim 62 words

Apparatus according to any of the preceding claims, characterised in that the scan converter means comprises: means (31) for repetitively accumulating the cosine of the angle coordinate of the polar coordinate being converted to provide the corresponding Y-coordinate, and means (31) for repetitively accumulating the sine of the angle coordinate of the polar coordinate being converted to provide the X-coordinate corresponding thereto.

Claim 9

Dependent Claim 62 words

Apparatus according to any of the preceding claims, characterised in that at least two polar coordinate points convert into the same cartesian coordinate point, thereby resulting in a multiaddressed storage location in the refresh memory (39), each location of R,theta table (29) storing a peak detect signal representative of whether or not the associated storage location of the refresh memory is multiaddressed.

Claim 10

Dependent Claim 66 words

Apparatus according to claim 8, characterised in that it further includes peak detection means (36) responsive to the peak detect signal for providing to the storage location of the refresh memory (39) being updated the maximum of the target data from the buffer (27) or from the refresh memory in accordance with coordinates currently being processed when the peak detect signal indicates a multiaddressed storage location.

Claim 11

Dependent Claim 59 words

Apparatus according to claim 9, characterised in that the location in the R,theta table (29) corresponding to the first multiaddressing polar coordinate point stores a peak detect signal representative of no peak detection and the locations in the R.theta table corresponding to the second and subsequent multiaddressing polar coordinate points store peak detect signals representative of performing peak detection.

Claim 12

Independent Claim 69 words

A method for displaying data expressed in polar coordinates by converting the polar coordinates to cartesian coordinates for display in a system with a display screen (42) having pixels arranged in cartesian coordinates and a refresh memory (39) arranged in a matrix of storage locations corresponding respectively to the pixels, some of the storage locations having addresses not addressable by converted cartesian coordinates, the method comprising the steps of:-

Claim 13

Independent Claim 69 words

A method for displaying data expressed in polar coordinates by converting the polar coordinates to cartesian coordinates for display in a system with a display screen (42) having pixels arranged in cartesian coordinates and a refresh memory (39) arranged in a matrix of storage locations corresponding respectively to the pixels, some of the storage locations having addresses not addressable by converted cartesian coordinates, the method comprising the steps of:-

Claim 14

Dependent Claim 9 words

converting each polar coordinate to a corresponding cartesian coordinate,

Claim 15

Dependent Claim 9 words

converting each polar coordinate to a corresponding cartesian coordinate,

Claim 16

Dependent Claim 25 words

addressing a R, theta table (21) having addresses corresponding to polar coordinates of the data, each address storing fill signals for the refresh memory (39),

Claim 17

Dependent Claim 25 words

addressing a R, theta table (21) having addresses corresponding to polar coordinates of the data, each address storing fill signals for the refresh memory (39),

Claim 18

Dependent Claim 10 words

accessing each unaddressable storage location with the fill signals; and

Claim 19

Dependent Claim 10 words

accessing each unaddressable storage location with the fill signals; and

Claim 20

Dependent Claim 11 words

storing fill data in storage locations accessed by the fill signals.

Claim 21

Dependent Claim 11 words

storing fill data in storage locations accessed by the fill signals.

Claim 22

Dependent Claim 35 words

A method according to claim 11, characterised in that it further includes the steps of:- dividing the display screen into sectors, and filling the unaddressable storage locations sequentially in a direction determined by the sector.

Claim 23

Dependent Claim 87 words

A method according to claim 11 or 12, characterised in that the filling step includes the steps of:- incrementing or decrementing the cartesian coordinates in accordance with the fill direction, thereby accessing the unaddressable storage locations, adding or subtracting multiples of sine or cosine functions of angular ordinates of the polar coordinates to establish range ordinates associated with the unaddressable storage locations, and generating fill data in response to the range ordinate associated with the storage location, and filling the unaddressable storage location with the fill data.

Claim 24

Dependent Claim 39 words

A method according to claim 13, characterised in that the step of generating fill data includes the steps of:- storing target data associated with a range sweep at quantised distances thereof, and accessing data corresponding to each range ordinate.

Scan conversion apparatus and method

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