Electrophoretic display drive techniques
Techniques for updating an electrophoretic display or other integrating display are provided. A first image data representing the current optical state of the display is combined with a second image data representing the desired next optical state of the display along with a third data representing the charge history of the display to form a compact intermediate representation of the electrical drive signals required to transition the display. Such compact intermediate representations can be provided for each pixel of the display and stored in flash memory. Once determined, these representations of the drive signals can be rapidly replayed from flash memory and further processed to drive the display and affect the desired optical transition from current image to next image while correcting for DC imbalances.
1. A display driving system, comprising:
a memory configured to store:
a first memory structure containing a representation of a current optical state of a display;
a second memory structure containing a representation of a next optical state of the display; and
a third memory structure containing a look-up table that encodes a target set of electrical drive signals in an intermediate representation for transitioning the display from the current optical state to the next optical state, the target set of electrical drive signals forming a multipart drive signal, and the intermediate representation of the target set of electrical drive signals includes a plurality of look-up table indices, each look-up table index indicating a polarity and duration for a distinct part of the multipart drive signal to be applied to the display in three distinct passes, wherein each distinct pass corresponds to a distinct part of the multipart drive signal, thereby providing a multi-pass display update process; and
a controller configured to:
combine content of the first memory structure with content of the second memory structure to form an index;
use the index to look-up the intermediate representation of the target set of electrical drive signals in the look-up table; and
drive the display based at least in part on the target set of electrical drive signals, thereby updating the display from the current optical state to the next optical state.
2. The display driving system of claim 1 wherein the memory is further configured to store an additional memory structure containing a cumulative charge history of drive signals applied to the display.
3. The display driving system of claim 2 wherein the controller is further configured to use at least partial content of the additional memory structure to form the index.
4. The display driving system of claim 2 wherein the controller is further configured to update the additional memory structure each time the display is updated, so as to maintain the cumulative charge history.
5. The display driving system of claim 1 wherein the controller is configured to form an index for each of at least multiple pixels of the display, and to use each of those indices to look-up a corresponding intermediate representation of a target set of electrical drive signals for an associated pixel, and to drive the display based at least in part on each target set of electrical drive signals.
6. The display driving system of claim 1 wherein the memory comprises flash memory.
7. The display driving system of claim 1 wherein the display is an electrophoretic display.
8. A mobile computing device comprising the display driving system of claim 1 .
9. The mobile computing device of claim 8 wherein the mobile computing device is an e-reader or tablet computer.
10. An electrophoretic display driving system, comprising:
a flash memory configured to store:
a first memory structure containing a representation of a current optical state of a display;
a second memory structure containing a representation of a next optical state of the display; and
a third memory structure containing a look-up table that encodes a target multipart drive signal in an intermediate representation for transitioning the display from the current optical state to the next optical state, the intermediate representation of the target multipart drive signal includes a plurality of look-up table indices, each look-up table index indicating a polarity and duration for a distinct part of the target multipart drive signal to be applied to the display in three distinct passes, wherein each distinct pass corresponds to a distinct part of the multipart drive signal, thereby providing a multi-pass display update process; and
a controller configured to:
combine content of the first and second memory structures to form an index;
use the index to look-up the intermediate representation of the target multipart drive signal in the look-up table, wherein the intermediate representation comprises a plurality of look-up table indices, each look-up table index associated with a polarity and duration for a distinct part of the target multipart drive signal to be applied to the display in corresponding distinct passes, thereby providing a multi-pass display update process; and
drive the display based at least in part on the target multipart drive signal, thereby updating the display from the current optical state to the next optical state.
11. The display driving system of claim 10 wherein the controller is configured to form an index for each of at least multiple pixels of the display, and to use each of those indices to look-up a corresponding intermediate representation of a target multipart drive signal for an associated pixel, and to drive the display based at least in part on each target multipart drive signal.
12. A mobile computing device comprising the display driving system of claim 10 .
13. An electrophoretic display driving system, comprising:
a flash memory configured to store:
a first memory structure containing a representation of a current optical state of a display;
a second memory structure containing a representation of a next optical state of the display;
a third memory structure containing a cumulative charge history of drive signals applied to the display; and
a fourth memory structure containing a look-up table that encodes a set of electrical drive signals in an intermediate representation for transitioning the display from the current optical state to the next optical state, the set of electrical drive signals forming a multipart drive signal, and the intermediate representation of the set of electrical drive signals includes a plurality of look-up table indices, each look-up table index indicating a polarity and duration for a distinct part of the multipart drive signal to be applied to the display in three distinct passes, wherein each distinct pass corresponds to a distinct part of the multipart drive signal, thereby providing a multi-pass display update process; and
a controller configured to:
combine content of the first, second, third, and fourth memory structures to form an index for accessing the look-up table;
use the index to look-up the intermediate representation of the set of electrical drive signals in the look-up table, wherein the intermediate representation comprises a plurality of look-up table indices, each look-up table index associated with drive signal polarity and duration to be applied to the display in distinct passes, thereby providing a multi-pass display update process; and
drive the display based at least in part on the set of electrical drive signals, thereby updating the display from the current optical state to the next optical state.
14. The display driving system of claim 13 wherein the controller is further configured to update the third memory structure each time the display is updated, so as to maintain the cumulative charge history.
15. The display driving system of claim 13 wherein the controller is configured to form an index for each of at least multiple pixels of the display, and to use each of those indices to look-up a corresponding intermediate representation of a set of electrical drive signals for an associated pixel, and to drive the display based at least in part on each set of electrical drive signals.
16. The display driving system of claim 13 wherein each pass of the multi-pass display update process is associated with a maximum frame count with respect to all pixels, and in response to the drive signal duration for a given pixel and a given pass being less than the maximum frame count, the controller is further configured to set the drive signal polarity to a neutral value for any remaining frames of that pass until the maximum frame count is reached.
17. The display driving system of claim 13 wherein the controller is further configured to commence the drive signal polarity at the beginning of a given pass rather than later in a given pass.
18. A mobile computing device comprising the display driving system of claim 13 .