Display device using time division modulation to display grey scale

Claim 2

A display device comprising: (a) an array of pixel elements each switchable between an "ON" state and an "OFF" state; (b) means for providing a succession of image signals each representative of successive image frames, each said image signal representing a plurality of numbers each comprising a plurality of bits, each number corresponding to a different pixel element in each image frame, each bit on each said number defining one of a plurality of different "ON" time periods for one of the pixel elements so that each number represents the total "ON" time period for a different one of the pixel elements in each image frame; (c) means for switching each pixel element "ON" in each image frame for time periods corresponding to said total "ON" time periods; and (d) means for re-ordering said "ON" time period such that the "ON" time periods for a pixel element in each image frame are in a sequence which differs from the order of the bits in the number corresponding to the pixel element, said re-ordering being such that any difference in the temporal distribution of the "ON" time periods for each pixel in successive frame intervals is less than the difference which would arise if said "ON" time periods were not re-ordered.

Claim 3

A display device according to claim 1, wherein at least one of said "ON" time periods is divided into at least two sub-periods which are temporally spaced apart from each other.

Claim 4

A display device according to claim 1, in which the means for re-ordering said "ON" time periods positions each "ON" period within the display frame period according to the change in total "ON" time for each pixel between the successive frame periods.

Claim 7

A method according to claim 4 including the step of dividing at least one of said time periods into at least two sub-periods and said step of re-ordering includes ordering said at least two sub-periods so that they are temporally spaced from each other.

Claim 8

A display system comprising: (a) a display device comprising an array of pixel elements each switchable between an "ON" state and an "OFF" state; (b) means for providing a succession of image signals each representative of successive image frames, each said image signal representing a plurality of numbers each comprising a plurality of bits, each number corresponding to a different pixel element in each image frame, each bit of each said number defining one of a plurality of different "ON" time periods for one of the pixel elements so that each number represents the total "ON" time period for a different one of the pixel elements in each image frame; (c) means for switching each pixel element "ON" in each image frame for time periods corresponding to said total "ON" time periods; (d) means for re-ordering said "ON" time periods such that the "ON" time periods for a pixel element in each image frame are in a sequence which differs from the order of the bits in the number corresponding to the pixel element, said re-ordering being such that any difference in the temporal distribution of the "ON" time periods for each pixel in successive frame intervals is less than the difference which would arise if said "ON" time periods were not re-ordered, and (e) a display screen, the display device being effective to project successive image frames onto the display screen.

Claim 9

A display system comprising: (a) a display device comprising an array of pixel elements each switchable between an "ON" state and an "OFF" state; (b) means for providing a succession of image signals each representative of successive image frames, each said image signal representing a plurality of numbers each comprising a plurality of bits, each number corresponding to a different pixel element in each image frame, each bit of each said number defining one of a plurality of different "ON" time periods for one of the pixel elements so that each number represents the total "ON" time period for a different one of the pixel elements in each image frame; (c) means for switching each pixel element "ON" in each image frame for time periods corresponding to said total "ON" time periods; (d) means for re-ordering said "ON" time periods such that the "ON" time periods for a pixel element in each image frame are in a sequence which differs from the order of the bits in the number corresponding to the pixel element, said re-ordering being such that any difference in the temporal distribution of the "ON" time periods for each pixel in successive frame intervals is less than the difference which would arise if said "ON" time periods were not re-ordered, and (e) a display screen, the display device being effective to project successive image frames onto the display screen.

Claim 10

A display device comprising: (a) an array of pixel elements each switchable between an "ON" state and an "OFF" state; (b) means for providing a succession of image signals each representative of successive image frames, each said image signal representing a plurality of numbers each comprising a plurality of bits, each number corresponding to a different pixel element in each image frame, each bit of each said number defining one of a plurality of different "ON" time periods for one of the pixel elements so that each number represents the total "ON" time period for a different one of the pixel elements in each image frame; (c) means for switching each pixel element "ON" in each image frame for time periods corresponding to said "ON" time periods; and (d) means for dividing at least one of said plurality of different "ON" time periods into at least two sub-periods effective to switch said one pixel element "ON" during time intervals which are temporally spaced apart from each other, such that any differences in at least one of the temporal distribution between successive frame intervals and the temporal distribution between adjacent pixel elements are less than the differences which would arise if said "ON" time period was not divided.

Claim 11

A display device comprising: (a) an array of pixel elements each switchable between an "ON" state and an "OFF" state; (b) means for providing a succession of image signals each representative of successive image frames, each said image signal representing a plurality of numbers each comprising a plurality of bits, each number corresponding to a different pixel element in each image frame, each bit of each said number defining one of a plurality of different "ON" time periods for one of the pixel elements so that each number represents the total "ON" time period for a different one of the pixel elements in each image frame; (c) means for switching each pixel element "ON" in each image frame for time periods corresponding to said "ON" time periods; and (d) means for dividing at least one of said plurality of different "ON" time periods into at least two sub-periods effective to switch said one pixel element "ON" during time intervals which are temporally spaced apart from each other, such that any differences in at least one of the temporal distribution between successive frame intervals and the temporal distribution between adjacent pixel elements are less than the differences which would arise if said "ON" time period was not divided.

Claim 12

A display device according to claim 7, including means for dynamically balancing said sub-periods in each display frame period.

Claim 13

A display device according to claim 7, in which said one "ON" time period corresponds to the longest time period of said "ON" time periods.

Claim 16

A display system comprising: (a) a display device comprising an array of pixel elements each switchable between an "ON" state and an "OFF" state; (b) means for providing a succession of image signals each representative of successive image frames, each said image signal representing a plurality of numbers each comprising a plurality of bits, each number corresponding to a different pixel element in each image frame, each bit of each said number defining one of a plurality of different "ON" time periods for one of the pixel elements so that each number represents the total "ON" time period for a different one of the pixel elements in each image frame; (c) means for switching each pixel element "ON" in each image frame for time periods corresponding to said "ON" time periods; (d) means for dividing at least one of said plurality of different "ON" time periods into at least two sub-periods effective to switch said one pixel element "ON" during time intervals which are temporally spaced apart from each other, such that any differences in at least one of the temporal distribution between successive frame intervals and the temporal distribution between adjacent pixel elements are less than the differences which would arise if said "ON" time period was not divided; and (e) a display screen, the display device being effective to project successive image frames onto the display screen.

Claim 17

A display system comprising: (a) a display device comprising an array of pixel elements each switchable between an "ON" state and an "OFF" state; (b) means for providing a succession of image signals each representative of successive image frames, each said image signal representing a plurality of numbers each comprising a plurality of bits, each number corresponding to a different pixel element in each image frame, each bit of each said number defining one of a plurality of different "ON" time periods for one of the pixel elements so that each number represents the total "ON" time period for a different one of the pixel elements in each image frame; (c) means for switching each pixel element "ON" in each image frame for time periods corresponding to said "ON" time periods; (d) means for dividing at least one of said plurality of different "ON" time periods into at least two sub-periods effective to switch said one pixel element "ON" during time intervals which are temporally spaced apart from each other, such that any differences in at least one of the temporal distribution between successive frame intervals and the temporal distribution between adjacent pixel elements are less than the differences which would arise if said "ON" time period was not divided; and (e) a display screen, the display device being effective to project successive image frames onto the display screen.

Claim 18

A display device comprising: (a) an array of pixel elements each switchable between an "ON" state and an "OFF" state; (b) a signal providing circuit arranged to provide a succession of image signals each representative of successive image frames, each said image signal representing a plurality of numbers each comprising a plurality of bits, each number corresponding to a different pixel element in each image frame, each bit on each said number defining one of a plurality of different "ON" time periods for one of the pixel elements so that each number represents the total "ON" time period for a different one of the pixel elements in each image frame; (c) a switching circuit arranged to switch each pixel element "ON" in each image frame for time periods corresponding to said total "ON" time periods; and (d) a reordering circuit arranged to re-order said "ON" time period such that the "ON" time periods for a pixel element in each image frame are in a sequence which differs from the order of the bits in the number corresponding to the pixel element, said re-ordering being such that any difference in the temporal distribution of the "ON" time periods for each pixel in successive frame intervals is less than the difference which would arise if said "ON" time periods were not re-ordered.

Claim 19

A display device comprising: (a) an array of pixel elements each switchable between an "ON" state and an "OFF" state; (b) a signal providing circuit arranged to provide a succession of image signals each representative of successive image frames, each said image signal representing a plurality of numbers each comprising a plurality of bits, each number corresponding to a different pixel element in each image frame, each bit on each said number defining one of a plurality of different "ON" time periods for one of the pixel elements so that each number represents the total "ON" time period for a different one of the pixel elements in each image frame; (c) a switching circuit arranged to switch each pixel element "ON" in each image frame for time periods corresponding to said total "ON" time periods; and (d) a reordering circuit arranged to re-order said "ON" time period such that the "ON" time periods for a pixel element in each image frame are in a sequence which differs from the order of the bits in the number corresponding to the pixel element, said re-ordering being such that any difference in the temporal distribution of the "ON" time periods for each pixel in successive frame intervals is less than the difference which would arise if said "ON" time periods were not re-ordered.

Claim 20

A display system comprising: (a) a display device comprising an array of pixel elements each switchable between an "ON" state and an "OFF" state; (b) a signal providing circuit arranged to provide a succession of image signals each representative of successive image frames, each said image signal representing a plurality of numbers each comprising a plurality of bits, each number corresponding to a different pixel element in each image frame, each bit of each said number defining one of a plurality of different "ON" time periods for one of the pixel elements so that each number represents the total "ON" time period for a different one of the pixel elements in each image frame; (c) a switching circuit arranged to switch each pixel element "ON" in each image frame for time periods corresponding to said total "ON" time periods; (d) a re-ordering circuit arranged to reorder said "ON" time periods for a pixel element in each image frame are in a sequence which differs from the order of the bits in the number corresponding to the pixel element, said re-ordering being such that any difference in the temporal distribution of the "ON" time periods for each pixel in successive frame intervals is less than the difference which would arise if said "ON" time periods were not re-ordered; and (e) a display screen, the display device being effective to project successive image frames onto the display screen.

Claim 21

A display system comprising: (a) a display device comprising an array of pixel elements each switchable between an "ON" state and an "OFF" state; (b) a signal providing circuit arranged to provide a succession of image signals each representative of successive image frames, each said image signal representing a plurality of numbers each comprising a plurality of bits, each number corresponding to a different pixel element in each image frame, each bit of each said number defining one of a plurality of different "ON" time periods for one of the pixel elements so that each number represents the total "ON" time period for a different one of the pixel elements in each image frame; (c) a switching circuit arranged to switch each pixel element "ON" in each image frame for time periods corresponding to said total "ON" time periods; (d) a re-ordering circuit arranged to reorder said "ON" time periods for a pixel element in each image frame are in a sequence which differs from the order of the bits in the number corresponding to the pixel element, said re-ordering being such that any difference in the temporal distribution of the "ON" time periods for each pixel in successive frame intervals is less than the difference which would arise if said "ON" time periods were not re-ordered; and (e) a display screen, the display device being effective to project successive image frames onto the display screen.

Claim 22

A display device comprising: (a) an array of pixel elements each switchable between an "ON" state and an "OFF" state; (b) a signal providing circuit arranged to provide a succession of image signals each representative of successive image frames, each said image signal representing a plurality of numbers each comprising a plurality of bits, each number corresponding to a different pixel element in each image frame, each bit of each said number defining one of a plurality of different "ON" time periods for one of the pixel elements so that each number represents the total "ON" time period for a different one of the pixel elements in each image frame; (c) a switching circuit arranged to switch each pixel element "ON" in each image frame for time periods corresponding to said "ON" time periods; and (d) a re-ordering circuit arranged to divide at least one of said plurality of different "ON" time periods into at least two sub-periods effective to switch said one pixel element "ON" during time intervals which are temporally spaced apart from each other, such that any differences in at least one of the temporal distribution between successive frame intervals and the temporal distribution between adjacent pixel elements are less than the differences which would arise if said "ON" time period was not divided.

Claim 23

A display device comprising: (a) an array of pixel elements each switchable between an "ON" state and an "OFF" state; (b) a signal providing circuit arranged to provide a succession of image signals each representative of successive image frames, each said image signal representing a plurality of numbers each comprising a plurality of bits, each number corresponding to a different pixel element in each image frame, each bit of each said number defining one of a plurality of different "ON" time periods for one of the pixel elements so that each number represents the total "ON" time period for a different one of the pixel elements in each image frame; (c) a switching circuit arranged to switch each pixel element "ON" in each image frame for time periods corresponding to said "ON" time periods; and (d) a re-ordering circuit arranged to divide at least one of said plurality of different "ON" time periods into at least two sub-periods effective to switch said one pixel element "ON" during time intervals which are temporally spaced apart from each other, such that any differences in at least one of the temporal distribution between successive frame intervals and the temporal distribution between adjacent pixel elements are less than the differences which would arise if said "ON" time period was not divided.

Claim 24

A display system comprising: (a) a display device comprising an array of pixel elements each switchable between an "ON" state and an "OFF" state; (b) a signal providing circuit arranged to provide a succession of image signals each representative of successive image frames, each said image signal representing a plurality of numbers each comprising a plurality of bits, each number corresponding to a different pixel element in each image frame, each bit of each said number defining one of a plurality of different "ON" time periods for one of the pixel elements so that each number represents the total "ON" time period for a different one of the pixel elements in each image frame; (c) a switching circuit arranged to switch each pixel element "ON" in each image frame for time periods corresponding to said "ON" time periods; (d) a re-ordering circuit arranged to divide at least one of said plurality of different "ON" time periods into at least two sub-periods effective to switch said one pixel element "ON" during time intervals which are temporally spaced apart from each other, such that any differences in at least one of the temporal distribution between successive frame intervals and the temporal distribution between adjacent pixel elements are less than the differences which would arise if said "ON" time period was not divided; and (e) a display screen, the display device being effective to project successive image frames onto the display screen.

Claim 25

A display system comprising: (a) a display device comprising an array of pixel elements each switchable between an "ON" state and an "OFF" state; (b) a signal providing circuit arranged to provide a succession of image signals each representative of successive image frames, each said image signal representing a plurality of numbers each comprising a plurality of bits, each number corresponding to a different pixel element in each image frame, each bit of each said number defining one of a plurality of different "ON" time periods for one of the pixel elements so that each number represents the total "ON" time period for a different one of the pixel elements in each image frame; (c) a switching circuit arranged to switch each pixel element "ON" in each image frame for time periods corresponding to said "ON" time periods; (d) a re-ordering circuit arranged to divide at least one of said plurality of different "ON" time periods into at least two sub-periods effective to switch said one pixel element "ON" during time intervals which are temporally spaced apart from each other, such that any differences in at least one of the temporal distribution between successive frame intervals and the temporal distribution between adjacent pixel elements are less than the differences which would arise if said "ON" time period was not divided; and (e) a display screen, the display device being effective to project successive image frames onto the display screen.

Claim 26

A display device according to claim 1 or 7, comprising a modulated light source which is switched synchronously with the switching of the pixel elements so as to partially display grey scales.

Claim 27

A display device according to claim 1 or 7, in which the array of pixel elements is a deflectable mirror device.

Claim 28

A display device according to claim 1 or 7, in which the display device is for a parallel color display system, each pixel element being effective to direct light of one color component.

Claim 29

A display device according to claim 1 or 7, in which the display device is for a sequential color display system, each pixel element being effective to direct light of different color components sequentially.

Claim 30

A display device according to claim 1 or 7, in which said different "ON" periods are in a binary sequence.