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AssigneePoro Technologies Ltd
InventorEdward BUCKLEY
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A method of calibrating a display device comprising a variable-wavelength LED is provided, in which the variable-wavelength LED is a pixel of the device, or one of a plurality of subpixels of a device pixel. The display device is programmed to operate using a palette of N available primary emission wavelengths λP, wherein each of the N available primaries is a wavelength emittable by the variable-wavelength LED. The pixel or plurality of subpixels are driveable to emit light at any of the N available primary emission wavelengths λP in response to N respective subfields of driving conditions. The method comprises the steps of: selecting a set of three or more discrete primary emission wavelengths λP, the set of primary emission wavelengths λP corresponding to a set of subfields of driving conditions; and driving the variable-wavelength LED with a first subfield of driving conditions for a first duty cycle to emit a first primary emission wavelength λP1 of the device, with a first luminance L1. The first primary emission wavelength λP1 is the longest of the selected primary emission wavelengths. The method comprises the steps of setting the respective duty cycles of the subfields of driving conditions for the other selected primary emission wavelengths in the set to shorter durations than the first duty cycle, and controlling the durations of the respective duty cycles of the other subfields in the set so that the primary emission wavelengths λP and luminances of all primary emission wavelengths in the set are complementary and sum to a standard illuminant point. A method of driving the display device comprises the steps of: identifying an output signal to be displayed by a pixel, or a subpixel, of the display device during a display frame; selecting a set of three or more of the N available primary emission wavelengths which are combinable to form the output signal; and driving the variable-wavelength LED to emit one or more of the set of three or more primary emission wavelengths λP within a display frame, each primary emission wavelength λP being driven by supplying a corresponding subfield of driving conditions to the pixel or subpixel; so that the light emitted at the selected primary emission wavelengths during the display frame combines to form the output signal with an output chromaticity and output luminance LO.
A method of calibrating a display device comprising a variable-wavelength LED, the variable-wavelength LED being a pixel of the device, or one of a plurality of subpixels of a device pixel, the display device being programmed to operate using a palette of N available primary emission wavelengths λP, wherein each of the N available primaries is a wavelength emittable by the variable-wavelength LED, the pixel or plurality of subpixels being driveable to emit light at any of the N available primary emission wavelengths λP in response to N respective subfields of driving conditions, the method comprising the steps of:
The method of any preceding claim, in which the step of controlling the durations of the respective duty cycles of the other subfields controls the luminances of the light emitted when those subfields of driving conditions are applied.
The method of any preceding claim, in which the respective duty cycles of the other primary emission wavelength subfields are shorter than the first duty cycle.
The method of any preceding claim, comprising the step of using the first luminance L1 as a reference luminance and the first duty cycle as a reference duty cycle, and setting the respective duty cycles of the other subfields to shorter durations than the first duty cycle so that the luminances of the other subfields fulfil, with the first luminance L1, a standard-illuminant point colour-mixing ratio at which the primary emission wavelengths λP and luminances of all selected primary emission wavelength subfields are complementary and sum to the standard illuminant point.
The method of any preceding claim, comprising the step of looking up, or calculating, the required colour-mixing ratio required to arrive at the standard illuminant point by combining the selected primary emission wavelengths.
The method of any preceding claim, comprising the steps of:
The method according to any preceding claim, in which the variable-wavelength LED is a pixel of the display device and in which the method is a method of controlling a field-sequential display device comprising a variable-wavelength LED pixel, the variable-wavelength LED pixel being driveable to emit light at N primary emission wavelengths λP in response to N respective subfields of driving conditions being provided to the variable-wavelength LED, in which the three or more primary emission wavelengths λP are selected to be within an emission wavelength range of the variable-wavelength LED, each primary emission wavelength λP corresponding to a respective subfield of driving conditions.
The method of any preceding claim, in which three primary emission wavelengths are selected, such that first, second and third primary emission wavelengths are driveable by first, second and third subfields of driving conditions, and in which the method comprises:
The method of any preceding claim, comprising the step of repeating the method for a plurality of sets of three or more primary emission wavelengths.
The method of any preceding claim, in which N is 3 or more, or 4 or more, or 5 or more, or 6 or more.
The method of any preceding claim, in which the first duty cycle is a 100% duty cycle.
The method of any preceding claim, in which the first primary emission wavelength λP1 is a red (R) wavelength.
The method of any preceding claim, in which the variable-wavelength LED has an emission wavelength range of between 100 nm and 200 nm, or between 125 nm and 185 nm, or between 150 nm and 175 nm.
The method of any preceding claim, in which the emission wavelength range extends from a lower limit, which is preferably below 500 nm or below 450 nm, to an upper limit, which is preferably above 595 nm or above 630 nm.
The method of any preceding claim, in which the variable-wavelength LED has a FWHM of 50 nm or less, or 40 nm or less, or 30 nm or less, or 20 nm or less.
The method of any preceding claim, comprising a step of selecting first, second and third primary emission wavelengths from the N available primary emission wavelengths.
The method of any preceding claim, in which the variable-wavelength LED emits red light in response to the first driving subfield, green light in response to the second driving subfield, and blue light in response to the third driving subfield.
The method of any preceding claim, in which the first subfield drives the variable-wavelength LED to emit a red primary emission wavelength, and in which the first duty cycle has a duration of 100% of the duration of a display subframe, so that the first luminance L1 is the luminance emitted at the red primary emission wavelength at 100% duty cycle.
The method of any preceding claim, in which the method comprises the step of reducing the duty cycles of the green and blue subfields until the luminances of the green and blue primary emission wavelengths fulfil the required colour-mixing ratio with the red first luminance L1.
The method of any preceding claim, in which the variable-wavelength LED is a device pixel, and in which the method is a method of calibrating the display for field-sequential driving of the variable-wavelength LED pixel to emit a plurality of primary emission wavelengths in sequential subframes of a display frame.
A method of calibrating a field-sequential display device comprising a variable-wavelength LED pixel, the display device being programmed to operate using a palette of N available primary emission wavelengths λP, wherein each of the N available primaries is a wavelength emittable by the variable-wavelength LED, the variable-wavelength LED pixel being driveable to emit light at any of the N available primary emission wavelengths λP in response to N respective subfields of driving conditions, the method comprising the steps of:
The method of any preceding claim, in which the method comprises a step of storing the calibrated duty cycles for the sets of primary emission wavelengths.
The method of any preceding claim, in which the method comprises the steps of programming a display controller with the calibrated duty cycles for the sets of primary emission wavelengths.
The method of any preceding claim, in which the method comprises the step of calibrating the luminance of the primary emission wavelengths by setting the duty cycles for each set of primary emission wavelengths so that the complementary wavelengths and their respective luminances sum to the standard illuminant point.
The method of any preceding claim, in which the method comprises the step of calibrating the luminance of the complementary primary emission wavelengths by measuring the emitted luminance as the variable-wavelength LED pixel is driven across its emission wavelength range.
A method of driving a display device comprising a variable-wavelength LED, the variable-wavelength LED being a pixel of the device, or one of a plurality of subpixels of a device pixel, the display device being programmed to operate using a palette of N available primary emission wavelengths λP, wherein each of the N available primaries is a wavelength emittable by the variable-wavelength LED, the pixel or plurality of subpixels being driveable to emit light at any of the N available primary emission wavelengths λP in response to N respective subfields of driving conditions, the method comprising the steps of:
Dependencies are inferred from the claim text.