Methods for driving bistable electro-optic displays, and apparatus for use therein

A method of driving a bistable electro-optic display having a plurality of pixels, each of which is capable of displaying at least three gray levels, the method comprising:

• storing a look-up table containing data representing the impulses necessary to convert an initial gray level to a final gray level;
• storing data representing at least an initial state of each pixel of the display;
• storing data representing at least two temporal prior states of each pixel at predetermined times prior to the initial state;
• storing data representing at least one gray level prior state of each pixel prior to a change in gray scale level to produce the initial state;
• receiving an input signal representing a desired final state of at least one pixel of the display;
• and
• generating an output signal representing the impulse necessary to convert the initial state of said one pixel to the desired final state thereof, as determined from the look-up table, the output signal being generated dependent upon said at least two temporal prior states, said at least one gray level prior state and said initial state of said one pixel.

A device controller comprising:

• storage means arranged to store a look-up table containing data representing the impulses necessary to convert an initial gray level to a final gray level, data representing at least an initial state of each pixel of the display, data representing at least one temporal prior state of each pixel of the display at a predetermined time prior to the initial state, and data representing at least two gray level prior states of each pixel prior to a change in gray scale level to produce the initial state;
• input means for receiving an input signal representing a desired final state of at least one pixel of the display;
• calculation means for determining, from the input signal, the stored data representing the initial state, the at least one temporal prior state and the at least two gray level prior states of said pixel, and the look-up table, the impulse required to change the initial state of said one pixel to the desired final state;
• and
• output means for generating an output signal representative of said impulse.

A device controller comprising:

• storage means arranged to store a look-up table containing data representing the impulses necessary to convert an initial gray level to a final gray level, data representing at least an initial state of each pixel of the display, data representing at least two temporal prior states of each pixel of the display at predetermined times prior to the initial state, and data representing at least one gray level prior state of each pixel prior to a change in gray scale level to produce the initial state;
• input means for receiving an input signal representing a desired final state of at least one pixel of the display;
• calculation means for determining, from the input signal, the stored data representing the initial state, the at least two temporal prior states and the at least one gray level prior state of said pixel, and the look-up table, the impulse required to change the initial state of said one pixel to the desired final state;
• and
• output means for generating an output signal representative of said impulse.

A method of driving a bistable electro-optic display having a plurality of pixels, each of which is capable of displaying at least three gray levels, the method comprising:

• storing a look-up table containing data representing the impulses necessary to convert an initial gray level to a final gray level;
• storing data representing at least an initial state of each pixel of the display;
• storing compensation voltage data representing a compensation voltage for each pixel of the display, the compensation voltage for any pixel being calculated dependent upon at least one impulse previously applied to that pixel;
• receiving an input signal representing a desired final state of at least one pixel of the display;
• and
• generating an output signal representing a pixel voltage to be applied to said one pixel, said pixel voltage being the sum of a drive voltage determined from the initial and final states of the pixel and the look-up table, and a compensation voltage determined from the compensation voltage data for the pixel,
• the compensation voltage for each pixel being applied to that pixel both during a period when a drive voltage is being applied to the pixel and during a hold period when no drive voltage is being applied to the pixel.

A method of driving a bistable electro-optic display having a plurality of pixels, each of which is capable of displaying at least three gray levels, the method comprising:

• storing a look-up table containing data representing the impulses necessary to convert an initial gray level to a final gray level;
• storing data representing at least an initial state of each pixel of the display;
• storing compensation voltage data representing a compensation voltage for each pixel of the display, the compensation voltage for any pixel being calculated dependent upon at least one impulse previously applied to that pixel;
• receiving an input signal representing a desired final state of at least one pixel of the display;
• and
• generating an output signal representing a pixel voltage to be applied to said one pixel, said pixel voltage being the sum of a drive voltage determined from the initial and final states of the pixel and the look-up table, and a compensation voltage determined from the compensation voltage data for the pixel,
• the compensation voltage for each pixel being updated during each superframe required for a complete addressing of the display.

A device controller comprising:

• storage means arranged to store both a look-up table containing data representing the impulses necessary to convert an initial gray level to a final gray level, data representing at least an initial state of each pixel of the display;
• and compensation voltage data for each pixel of the display;
• input means for receiving an input signal representing a desired final state of at least one pixel of the display;
• calculation means for determining, from the input signal, the stored data representing the initial state of said pixel, and the look-up table, a drive voltage required to change the initial state of said one pixel to the desired final state, the calculation means also determining, from the compensation voltage data for said pixel, a compensation voltage for said pixel, and summing the drive voltage and the compensation voltage to determine a pixel voltage;
• and
• output means for generating an output signal representative of said pixel voltage,
• the output means being arranged to apply the compensation voltage to the pixel both during a period when a drive voltage is being applied to the pixel and during a hold period when no drive voltage is being applied to the pixel.

A device controller comprising:

• storage means arranged to store both a look-up table containing data representing the impulses necessary to convert an initial gray level to a final gray level, data representing at least an initial state of each pixel of the display;
• and compensation voltage data for each pixel of the display;
• input means for receiving an input signal representing a desired final state of at least one pixel of the display;
• calculation means for determining, from the input signal, the stored data representing the initial state of said pixel, and the look-up table, a drive voltage required to change the initial state of said one pixel to the desired final state, the calculation means also determining, from the compensation voltage data for said pixel, a compensation voltage for said pixel, and summing the drive voltage and the compensation voltage to determine a pixel voltage;
• and
• output means for generating an output signal representative of said pixel voltage,
• the calculation means being arranged to update the compensation voltage for each pixel during each superframe required for a complete addressing of the display.

A method for updating a bistable electro-optic display having a plurality of pixels arranged in a plurality of rows and columns such that each pixel is uniquely defined by the intersection of a specified row and a specified column, and drive means for applying electric fields independently to each of the pixels to vary the display state of the pixel;

• each pixel having at least three different display states, the method comprising:
• storing region data representing a defined region comprising a part but less than all of said display;
• determining for each pixel whether the pixel is within or outside the defined region;
• applying a first drive scheme to pixels within the defined region and a second drive scheme, different from the first drive scheme, to pixels outside the defined region,
• the first and second drive scheme differing in bit depth.

A method of driving a bistable electro-optic display having a plurality of pixels, each of which is capable of displaying at least three gray levels, the method comprising:

• storing a look-up table containing data representing the impulses necessary to convert an initial gray level to a final gray level;
• storing data representing at least an initial state of each pixel of the display;
• receiving an input signal representing a desired final state of at least one pixel of the display;
• and
• generating an output signal representing the impulse necessary to convert the initial state of said one pixel to the desired final state thereof, as determined from the look-up table,
• wherein for at least one transition from an initial state to a final state, the output signal comprises a DC imbalanced fine tuning sequence which:
• (a) has a non-zero net impulse;
• (b) is non-contignous;
• (c) results in a change in gray level of the pixel that is substantially different from the change in optical state of its DC reference pulse, where the DC reference pulse is a pulse of voltage V0, where V0 is the maximum voltage applied during the fine tuning sequence but with the same sign as the net impulse G of the fine tuning sequence, and the duration of the reference pulse is G/V0;
• and
• (d) results in a change in gray level of the pixel smaller in magnitude than the change in gray level caused by its time-reference pulse, where the time-reference pulse is defined as a monopolar voltage pulse of the same duration as the fine tuning sequence, but where the sign of the reference pulse is that which gives the larger change in gray level.

A method of driving a bistable electro-optic display having a plurality of pixels, each of which is capable of displaying at least three gray levels, the method comprising:

• storing a look-up table containing data representing the impulses necessary to convert an initial gray level to a final gray level;
• storing data representing at least an initial state of each pixel of the display;
• receiving an input signal representing a desired final state of at least one pixel of the display;
• and
• generating an output signal representing the impulse necessary to convert the initial state of said one pixel to the desired final state thereof, as determined from the look-up table,
• wherein for at least one transition from an initial state to a final state, the output signal comprises a DC balanced fine tuning sequence which:
• (a) has substantially zero net impulse;
• and
• (b) at no point in the fine tuning sequence, causes the gray level of the pixel to vary from its gray level at the beginning of the fine tuning sequence by more than about one third of the difference in gray level between the two extreme optical states of the pixel.

A method of driving a bistable electro-optic display having at least one pixel which comprises applying to the pixel a waveform V(t) such that:

• J
• =
• ∫
• 0
• T
• ⁢
• V
• ⁡
• (
• t
• )
• ⁢
• M
• ⁡
• (
• T
• -
• t
• )
• ⁢
• ⅆ
• t
• (where T is the length of the waveform, the integral is over the duration of the waveform, V(t) is the waveform voltage as a function of time t, and M(t) is a memory function that characterizes the reduction in efficacy of the remnant voltage to induce dwell-time-dependence arising from a short pulse at time zero) is less than about 1 volt sec.