Display device comprising a variable-wavelength led and methods of calibrating and driving a display device comprising a variable-wavelength

The display device of any preceding claim, in which the absorptive colour filter is configured so that in use, light emitted at the first emission wavelength has a first luminance L1 prior to transmission through the absorptive colour filter, and a first transmitted luminance L1T after transmission through the absorptive colour filter, and light emitted at the second emission wavelength has a second luminance L2 prior to transmission through the absorptive colour filter, and a reduced second transmitted luminance L2T after transmission through the absorptive colour filter.

The display device of any preceding claim, in which the absorptive colour filter is configured to reduce, or modulate, the luminance of light having the second emission wavelength, so that in use, light emitted at the second emission wavelength has a second luminance L2 prior to transmission through the absorptive colour filter, and a reduced second transmitted luminance L2T after transmission through the absorptive colour filter, such that L2T<L2.

The display device of any preceding claim, in which the absorptive colour filter is configured not to reduce the luminance of light having the first emission wavelength, so that the magnitude of the first transmitted luminance L1T is at least 90%, or at least 92%, or at least 95%, or at least 98% of the magnitude of the first luminance L1.

The display device of any preceding claim, in which the absorptive colour filter is configured to absorb light emitted at the second emission wavelength to a greater degree than light emitted at the first emission wavelength, so that the ratio of L2T:L1T is lower than the ratio of L2:L1.

The display device of any preceding claim, in which the variable-wavelength LED is controllable to emit light at two or more selected primary emission wavelengths, such that in use the light transmitted out of the outlet of the display device during a display frame forms an observed signal which is the temporal combination of the primary emission wavelengths emitted by the variable-wavelength LED during the display frame.

The display device of any preceding claim, in which the display device comprises a controller programmed to drive the variable-wavelength LED to emit the first and second emission wavelengths in response to first and second respective driving conditions, the first and second emission wavelengths being wavelengths within the emission wavelength range of the variable-wavelength LED.

The display device of any preceding claim, in which the first driving condition is a first current density, and the second driving condition is a second current density greater in magnitude than the first current density.

The display device of any preceding claim, in which the first emission wavelength is a red emission wavelength of above 595 nm or above 630 nm, preferably in which the first emission wavelength is between 595 nm and 700 nm, or between 610 nm and 680 nm, preferably between 625 nm and 670 nm.

The display device of any preceding claim, in which the second emission wavelength is less than 595 nm.

The display device of any preceding claim, in which the second emission wavelength is a green emission wavelength of between 500 nm and 590 nm, or between 510 nm and 580 nm, preferably between 525 nm and 570 nm, or in which the second emission wavelength is a blue emission wavelength of below 495 nm, preferably in which the second emission wavelength is between 400 nm and 490 nm, or between 410 nm and 480 nm, preferably between 430 nm and 470 nm.

The display device of any preceding claim, in which the first and second emission wavelengths are at least 40 nm apart, or at least 50 nm apart within the emission wavelength range of the variable-wavelength LED.

The display device of any preceding claim, in which the display comprises a plurality of absorptive colour filters, each absorptive colour filter being configured to attenuate the luminance of light emitted at a respective emission wavelength.

The display device of any preceding claim, in which the variable-wavelength LED is driveable to emit light at a third emission wavelength in response to a third electrical driving condition provided to the variable-wavelength LED, the third emission wavelength being shorter than the first emission wavelength, and the first, second and third emission wavelengths being within the emission wavelength range of the variable-wavelength LED.

The display device of any preceding claim, in which the absorptive colour filter is configured to attenuate the luminance of the second emission wavelength from a second luminance L2, which is emitted by the variable-wavelength LED, to a transmitted second luminance L2T, so that the wavelengths and transmitted luminances of the first and second emission wavelengths are complementary and sum to a standard illuminant point.

The display device of any preceding claim, in which the absorptive colour filter comprises a glass, plastic or semiconductor-film substrate.

The display device of any preceding claim, in which the absorptive colour filter is a longpass filter.

The display device of any preceding claim, in which the variable-wavelength LED has an emission wavelength range with a width of between 100 nm and 200 nm, or between 125 nm and 185 nm, or between 150 nm and 175 nm, in which the variable-wavelength LED is continuously controllable over the emission wavelength range by varying the electrical driving condition provided to the variable-wavelength LED.

The display device of any preceding claim, in which the emission wavelength range of the variable-wavelength LED 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 display device 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 display device of any preceding claim, comprising an array of variable-wavelength LEDs, each variable-wavelength LED being a pixel of the device, or one of a plurality of subpixels of a device pixel.

The display device of any preceding claim, in which the absorptive colour filter is positioned over a plurality of variable-wavelength LEDs between the variable-wavelength LEDs and an outlet of the display device, such that light emitted by the plurality of variable-wavelength LEDs passes through the absorptive colour filter before passing out of the outlet of the display device.