Display screen comprising display pixels having light-emitting diodes

Abstract

The present description concerns a display screen comprising an array of display pixels each comprising a least one light-emitting diode, the display screen further comprising a first circuit (60) configured to receive initial video data (V_IN) and to apply a gamma decoding to the received initial video data (V_IN) to produce gamma corrected video data (V_G), a second circuit (62) configured to receive a brightness setting (B_SET ), a third circuit (64) configured to provide a decrease factor (DE) that depends on the brightness setting (B_SET), and a fourth circuit (66) configured to multiply the gamma corrected video data (V_G) by the decrease factor(DE) to provide brightness and gamma corrected video data (V_GB ).

Description

DESCRIPTIONTITLE : Display screen comprising display pixels having lightemitting diodesThis patent application claims priority from French patent application FR23 / 06905 which will be considered as an integral part of this description .Technical background

[0001] The present disclosure generally concerns display screens comprising display pixels having light-emitting diodes .Prior art

[0002] A pixel of an image corresponds to the unit element of the image displayed by a display screen . For the display of color images , a display screen generally comprises , for the display of each pixel of the image , at least three components , also called display sub-pixels , which each emit a light radiation substantially in a single color ( for example , red, green, and blue ) . The superposition of the radiations emitted by the three display sub-pixels provides the observer with the colored sensation corresponding to the pixel of the displayed image . In this case , the assembly formed by the three display sub-pixels used for the display of a pixel of an image is called display pixel of the display screen . Each display sub-pixel may comprise a light source , particularly a light-emitting diode .

[0003] The display pixels of a display screen may be distributed in an array, each display pixel being located at the intersection of a row ( also called line ) and of a column of the array . Electrodes are provided along the rows and the columns to connect each display pixels to control circuits . Generally, a selection and timing circuit isconnected to the row electrodes . Each row of display pixels is successively selected by signal transmitted along the row electrodes by the selection and timing circuit , and the display pixels of the selected row are programmed to display the desired image pixels by signals transmitted along the column electrodes .

[0004] An active array is a screen drive architecture enabling to maintain all the pixel rows active for the entire duration of an image , conversely to arrays said to be passive , where each row is only active for a time T = Tframe / M (where Tframe is the duration of the display of the whole image and M is the number of lines of the screen) . This enables to increase the luminosity of the display screen . Further, it is possible to send low voltage or current levels on the array control lines , which enables to display bigger data flows .

[0005] It is known to control a light emitting diode , by pulse-width modulation, also called PWM (English acronym for Pulse Width Modulation) . This type of control consists in circulating successive current pulses of constant intensity in the light-emitting diode , the pulses being repeated cyclically, the duty cycle determining the light intensity emitted by the light-emitting diode . Such a control advantageously makes it possible to operate the light-emitting diode at its optimum operating point where the ef ficiency of the light-emitting diode , equal to the ratio between the light power emitted by the light-emitting diode and the electrical power consumed by the lightemitting diode , is maximum . A PWM control usually requires the transmission by the selection and timing circuit of a successions of pulses on the row electrodes , the durations between the pulses depending on the image pixel to be displayed .

[0006] A display screen usually also comprises a setting to vary the global brightness of the image that is displayed . A way of decreasing the brightness of a displayed image with respect to a maximal brightness is to decrease the durations between the pulses of the transmission by the selection and timing circuit .

[0007] A drawback is that it can be di f ficult for the selection and timing circuit to provide pulses separated by short durations when the brightness is set to be low . There can be a limit to the minimum brightness that can be reached . Another drawback is that the selection and timing circuit needs to be able to provide many di f ferent successions of pulses separated by di f ferent durations according to the brightness settings .Summary of the invention

[0008] An obj ect of an embodiment is to provide a display screen comprising light-emitting diodes overcoming all or part of the disadvantages of existing display screens .

[0009] Another obj ect of an embodiment is that the selection and timing circuit provides the same succession of pulses for a PWM control regardless the brightness setting .

[0010] Another obj ect of an embodiment is that there is no limit to the minimum brightness that can be reached .

[0011] Another obj ect of an embodiment is that the structure of the selection and timing circuit is simple .

[0012] An embodiment provides a display screen comprising an array of display pixels each comprising a least one lightemitting diode , the display screen further comprising a first circuit configured to receive initial digital video data and to apply a gamma decoding to the received initial digital video data to produce gamma corrected digital videodata, a second circuit configured to receive a brightness setting, a third circuit configured to provide a digital decrease factor that depends on the brightness setting, and a fourth circuit configured to multiply the gamma corrected digital video data by the digital decrease factor to provide brightness and gamma corrected digital video data . The brightness correction is applied to the video data before they are transmitted to the display pixels . Therefore , the display pixels can advantageously be operated independently from the brightness correction . Moreover, there can be advantageously no limit to the minimum brightness that can be reached .

[0013] According to an embodiment , the display pixels are arranged in rows and columns , the display screen further comprising a data driver configured to provide video data to the columns of display pixels based on the brightness and gamma corrected digital video data . Therefore , the display pixels can advantageously be operated independently from the brightness correction .

[0014] According to an embodiment , each display pixels comprises a driver circuit configured to determine a digital signal from the video data and to control the lightemitting diode based on the digital signal .

[0015] According to an embodiment , the driver circuit is configured to control the light-emitting diode by pulsewidth modulation based on the digital signal . Such a control advantageously makes it possible to operate the light-emitting diode at its optimum operating point where the ef ficiency of the light-emitting diode is maximum .

[0016] According to an embodiment , the display screen comprises a selection and timing circuit configured to provide a succession of pul ses to each row of displaypixels . The pulses supplied by selection and timing circuit are , during a display phase , advantageously the same whatever the brightness setting is . Therefore , the structure of the selection and timing circuit can be simple .

[0017] According to an embodiment , the driver circuit is configured to turn on or turn of f the light-emitting diode at the rate of the succession of pulses .

[0018] Another embodiment provides a method for displaying images by a display screen comprising an array of display pixels each comprising a least one light-emitting diode , comprising the following steps ;-receiving initial digital video data ;-applying a gamma decoding to the received initial digital video data to produce gamma corrected digital video data ; -receiving a brightness setting;-providing a digital decrease factor that depends on the brightness setting;-multiplying the gamma corrected digital video data by the digital decrease factor to provide brightness and gamma corrected digital video data .

[0019] According to an embodiment , the display pixels are arranged in rows and columns , the method further comprising the step of providing video data to the columns of display pixels based on the brightness and gamma corrected digital video data .

[0020] According to an embodiment , each display pixels comprises a driver circuit configured to determine a digital signal from the video data and to control the lightemitting diode based on the digital signal .

[0021] According to an embodiment, the driver circuit is configured to control the light-emitting diode by pulsewidth modulation based on the digital signal.

[0022] According to an embodiment, the method comprises providing a succession of pulses to each row of display pixels .

[0023] According to an embodiment, the driver circuit is configured to turn on or turn off the light-emitting diode at the rate of the succession of pulses.Brief description of the drawings

[0024] The foregoing features and advantages, as well as others, will be described in detail in the rest of the disclosure of specific embodiments given by way of illustration and not limitation with reference to the accompanying drawings, in which:

[0025] Figure 1 partially and schematically shows an example of a display screen;

[0026] Figure 2 shows an example of a block diagram of a display pixel of the display screen of Figure 1;

[0027] Figure 3 shows examples of timing diagrams of a signal used by the display pixel of Figure 2 for controlling a light-emitting diode by pulse-width modulation and of the current supplied to the light-emitting diode;

[0028] Figure 4 shows examples of timing diagrams of a timing signal and current pulses for controlling a light-emitting diode by pulse-width modulation for different brightness settings ;

[0029] Figure 5 shows an embodiment of a block diagram of a circuit of the display screen of Figure 1 for varying the brightness of the displayed images;

[0030] Figure 6 shows a curve of evolution of a decreasing factor determined by the circuit of Figure 5 with respect to brightness settings;

[0031] Figure 7 shows examples of equivalent gamma decoding functions implemented by the circuit of Figure 5; and

[0032] Figure 8 shows examples of timing diagrams of a timing signal and current pulses for controlling a light-emitting diode by pulse-width modulation for different brightness settings by using the circuit of Figure 5.Description of the embodiments

[0033] Like features have been designated by like references in the various figures. In particular, the structural and / or functional features that are common among the various embodiments may have the same references and may dispose identical structural, dimensional and material properties. For the sake of clarity, only the steps and elements that are useful for an understanding of the embodiments described herein have been illustrated and described in detail.

[0034] In the following description, when reference is made to terms qualifying absolute positions, such as terms "front", "rear", "top", "bottom", "left", "right", etc., or relative positions, such as terms "above", "under", "upper", "lower", etc., or to terms qualifying directions, such as terms "horizontal", "vertical", etc., it is referred, unless specified otherwise, to the orientation of the drawings or to a display screen in a normal position of use.

[0035] Unless indicated otherwise, when reference is made to two elements connected together, this signifies a direct connection without any intermediate elements other thanconductors, and when reference is made to two elements coupled together, this signifies that these two elements can be connected or they can be coupled via one or more other elements.

[0036] Further, there is called "binary signal" a signal which alternates between a first constant state, for example, a low state, noted "0", and a second constant state, for example, a high state, noted "1". The high and low states of different binary signals of a same electronic circuit may be different. In practice, the binary signals may correspond to voltages which may not be perfectly constant in the high or low state.

[0037] Further, unless indicated otherwise, when it is spoken of a voltage at a conductive pad, the difference between the potential at said conductive pad and a reference potential, for example, the ground, taken as equal to 0 V, is considered.

[0038] Unless specified otherwise, the expressions "around", "approximately", "substantially" and "in the order of" signify within 10%, and preferably within 5%.

[0039] Figure 1 partially and schematically shows a known example of a display screen 10. Display screen 10 comprises display pixels 12lfj , for example, arranged in M rows and in N columns, M being an integer varying from 1 to 8,000 and N being an integer varying from 1 to 16,000, i being an integer varying from 1 to M, and j being an integer varying from 1 to N. As an example, in Figure 1, M and N are equal to 6. Each display pixel 12ifj is coupled to a source of a low reference potential Gnd, for example, the ground, via an electrode 14i and to a source of a high reference potential Vcc via an electrode 16j . As an example, electrodes 14i are shown as being aligned along the rows inFigure 1 and electrodes 16j are shown as being aligned along the columns in Figure 1 , the reverse layout being possible . The power supply voltage of the display screen corresponds to the voltage between high reference potential Vcc and low reference potential Gnd, and is noted Vcc like the high reference potential . Power supply voltage Vcc particularly depends on the arrangement of the light-emitting diodes and on the technology according to which the light-emitting diodes are manufactured . As an example , power supply voltage Vcc may be in the order of from 4 V to 5 V .

[0040] For each row, the display pixels 12i fj in the row are coupled to a row electrode 18i . For each column, the display pixels 12i fj in the column are coupled to a column electrode 20j . Display screen 10 comprises a selection and timing circuit 22 coupled to row electrodes 18i and adapted to delivering a selection and timing signal Comi on each row electrode 18i . Display screen 10 comprises a data delivery circuit 24 coupled to column electrodes 20j and adapted to delivering a data signal Dataj on each column electrode 20j . Selection and timing circuit 22 and control circuit 24 are controlled by a circuit 26 , for example comprising a processor . Circuit 26 receives video data V_IN and a brightness setting B_SET . Data signal Dataj are generated from video data V_IN .

[0041] Figure 2 shows an example of a block diagram of a display pixel 12l fj of display screen 10 . For a color di splay screen, display pixel 12l fj comprises a light-emitting circuit comprising at least three light-emitting diodes LED emitting radiations of di f ferent colors , a single lightemitting diode LED being shown in Figure 2 . Each lightemitting diode LED is series-coupled to a controllable current source CS , for example comprising a MOS transistor in series with a current source providing a constantcurrent . In the present example , for each light-emitting diode LED, the anode of light-emitting diode LED receives high reference potential Vcc and the cathode o f lightemitting diode LED is for example coupled to a terminal of controllable current source CS , the other terminal of controllable current source CS receiving low reference potential Gnd . In case of a monochrome display screen, each display pixel 12i fj can comprise a light-emitting circuit comprising a single light-emitting diode LED .

[0042] Display pixel 12i fj further comprises a driver circuit 40 for driving controllable current source CS . Driver circuit 40 may particularly comprise electronic components such as MOS transistors . Driver circuit 40 comprises a storage circuit 48 ( Color Data registers ) clocked by a clock signal Clk configured to store digital color signals R, G, B based on received digital data Data . Digital color signals R, G, B comprise each a number NB of bits , from the most signi ficant bit , called MSB, to the least signi ficant bit , called LSB, and are representative of the image pixel color components to be displayed . Driver circuit 40 comprises a circuit 50 ( LED driver ) configured to control the controllable current sources CS coupled to lightemitting diodes LED with signals I_red, I_green, and I_blue , obtained from digital color signals R, G, B, and from a signal PWM . Data Data can correspond to signal Dataj transmitted to the display pixel 12l fj on column electrode 20j during a selection phase . Signal PWM can correspond to selection and timing signal Comi transmitted to the display pixel 12i fj on row electrode 18i during a display phase .

[0043] Figure 3 shows a timing diagrams of signal PWM and signals I_red_l , I_red_2 , I_red_3 , and I_red_4 corresponding to signal I_red provided by circuit 50 of display pixel 12i fj of Figure 2 for the display of fourdi f ferent digital color signals R . According to an embodiment , light-emitting diodes LED of display pixel 12l fj are controlled by pulse-width modulation . For this purpose , during a display phase , signal PWM exhibits a succession of pulses at logical state " 1" which rates the operation of circuit 50 for the control of light-emitting diodes LED by pulse-width modulation . The number of pulses in the succession of pulses can correspond to the number NB+ 1 .

[0044] As an example , when current source CS corresponds to current source providing a constant current in series with a MOS transistor, the MOS transistor is turned on or is turned of f according to the logical value " 0" or " 1" of each bit of color signal R, G, or B, from the most signi ficant bit MSB to the least signi ficant bit LSB , at the rate of the pulses of signal PWM, the MOS transistor being maintained on or of f until the next pulse of signal PWM . Therefore , the current source CS is switched on or of f during NB successive durations according to the logical values of the bits of the digital signal R, G, or B . For example , current source CS can be switched on during a duration when the bit of the color digital data associated with this time interval is at logical value " 1" and can be switched of f during a duration when the bit of the color digital data associated with this time interval is at logical value " 0" . The duration between two successive pulses of signal PWM is divided each time by two , so that the total duration for which the light-emitting diode is on depends on the value of color signal R, G, or B . The succession of pulses of signal PWM can be repeated until the display of another image pixel . In that case , the succession of pulses of signal PWM forms a display cycle and the display phase comprises more than one display cycle .

[0045] In Figure 3 , as an example , number NB is equal to 7 and only one display cycle is shown . Signal I_red_l is obtained for the display of an image pixel color component corresponding to color signal R equal to " 1010101" . Signal I_red_2 is obtained for the display of an image pixel color component corresponding to color signal R equal to " 0101010" . Signal I_red_3 is obtained for the display of an image pixel color component corresponding to color signal R equal to " 1111111" . Signal I_red_4 is obtained for the display of an image pixel color component corresponding to color signal R equal to " 0000000" .

[0046] Circuit 26 of display screen 10 usually also receives a setting B_SET to vary the global brightness of the image that is displayed . This setting B_SET can be distinct from the video data received by circuit 26 . As an example , the brightness setting can be controlled by the person watching the display screen 10 . A way of decreasing the brightness of a displayed image with respect to a maximal brightness is to decrease the duration of a display cycle with respect to the maximal duration Tmax of a display cycle used for the maximal brightness , the light emitting diode LED being switched of f during the rest of duration Tmax .

[0047] Figure 4 shows timing diagrams of signal PWM and signal I_red provided by circuit 50 of display pixel 12l fj of Figure 2 for the display of the same color digital signal " 1010101" for three value of a brightness setting . The upper signals corresponds to the signal PWM and signal I_red when the cycle duration is equal to a maximal display cycle duration Tmax . The middle signal corresponds to the signal PWM and signal I_red when the cycle duration is equal substantially to 50% of maximal display cycle duration Tmax . The lower signal corresponds to the signalPWM and signal I_red when the cycle duration is equal substantially to 10% of maximal PWM cycle duration Tmax .

[0048] The decrease of the duration of a PWM cycle with respect to the maximal display cycle duration Tmax leads to the decrease of each duration associated with each bit of the color digital signal . This means that the pulses of the selection and timing signal Comi need to be generated closer by selection and timing circuit 22 .

[0049] A di f ficulty is to generate the pulses for providing the shortest duration associated with the LSB . Indeed, the propagation time of selection and timing signal Comi between display pixel 12i rj and timing circuit 22 varies with respect to the position of display pixel 12i fj on display screen 10 . In the arrangement shown in Figure 1 , the propagation time on row electrodes 18i is the shortest for the display pixels 12i fj on the first column that is the closest to selection and timing circuit 22 and is the longest for the display pixels 12i fj on the last column that is the furthest from timing circuit 22 . It is neces sary to take into account of these di f ferent propagation times to make sure that , for each row, all the pulses of selection and timing signal Comi during a display cycle are correctly transmitted to all the display pixels of the row . This can result in an upper limit as regards the operation speed of the display screen .

[0050] Moreover, as shown in Figure 4 , di f ferent signals PWM need to be sent to the display pixels according to the brightness setting . This can result in a selection and timing circuit 22 having a complex structure to be able to generate many di f ferent signals PWM .

[0051] Moreover, there is a limitation of minimum brightness control range . As an example , let us consider a displayscreen where the refresh frequency is equal to 120 Hz , the minimum pulse duration is equal to 50 ns , and NB is equal to 16 . The minimum possible display cycle duration is equal to 50 ns times 216, that is equal to 3 , 28 ms . This corresponds to a minimum brightness equal to 39% of the maximum brightness .

[0052] Figure 5 shows a block diagram of an embodiment of a part of circuit 26 of display screen 10 .

[0053] Circuit 26 comprises :-a circuit 60 configured to receive video data V_IN, to receive a gamma setting GAMMA and to apply to the received video data V_IN a gamma correction in order to provide successive gamma corrected video data V_G;-a circuit 62 configured to receive brightness setting B_SET and to store the received brightness setting B_SET ; -a circuit 64 configured to receive brightness setting B_SET stored in circuit 62 and to provide a decreasing factor DE; and-a circuit 66 configured to multiply each successive gamma corrected video data V_G with decreasing factor DE and to provide successive brightness and gamma corrected video data V_GB .

[0054] Each received video data V_IN comprise NB bits . Each gamma corrected video data V_G comprises NB+a bits . The additional number of bits " a" depends on the type of gamma correction that is performed by circuit 60 . The brightness setting comprises K bits . The decreasing factor DE is in the range from 0 to 1 . Each brightness and gamma corrected video data V_GB comprises NB+a bits . Data signal Dataj can correspond to brightness and gamma corrected video data V GB .

[0055] Figure 6 shows a curve of evolution of decreasing factor DF with respect to brightness setting B_SET. In the example shown in Figure 6, the decreasing factor DF varies linearly with brightness setting B_SET.

[0056] The human eyes are much more sensitive to changes in dark tones than they are to similar changes in bright tones. A photodetector usually provides an analog electric image pixel signal that has a substantially linear relationship with the number of photons hitting the sensor. If the display system was operated with a digital driving method such as pulse-width modulation operation, a high number of bits would need to be used for the digital image pixel signals for the dark tones to be described with enough precision. A digitalization with a low number of bits results in a posterization of the displayed image for the dark tones.

[0057] To optimize the usage of bits when encoding an image and / or to optimize the bandwidth used to transport an image, a non-linear operation, generally called gamma encoding or gamma compression, is applied to image pixel signal provided by the photodetector to redistribute native image sensor tonal levels into ones which are more perceptually uniform for the human eyes. Gamma encoding is for example defined by the following power-law expression:

[0058] [Math 1] Vout = Vinvcwhere the non-negative real input value Vin is raised to the power yc to get the output value Vout, with, for example, Vin and Vout in the range 0-1. The exponent yc usually is equal to 1 / 2.2.

[0059] To display the image pixel, the inverse non-linear operation, called gamma decoding or gamma expansion, isapplied to the image pixel signal to effectively convert it back into light from the original scene. Gamma decoding is for example defined by the following power-law expression :

[0060] [Math 2]Vout = Vinvdwhere the non-negative real input value Vin is raised to the power yd to get the output value Vout, with, for example, Vin and Vout in the range 0-1. The exponent yd usually is equal to 1 / yd, that is for example equal to 2.2.

[0061] The gamma decoding operation is performed by circuit 60. Gamma setting GAMMA can correspond to exponent yd, that is for example equal to 2, 2.2, or 2.4.

[0062] The multiplication of each gamma corrected video data V_G by decreasing factor DF is equivalent to resize the gamma decoding function that is applied to received video data V_IN.

[0063] Figure 7 shows the equivalent gamma decoding function IgamlOO, Igam50, Igam25 applied to the received video data V_IN for different brightness settings B_SET corresponding to a brightness equal to 100% (curve IgamlOO) , 50% (Igam50) , and 25% (Igam25) . In Figure 7, the y-axis indicates the number of levels of the brightness and gamma corrected video data V_GB and the x-axis indicates the number of levels of the received video data V_IN. To make tones appear smooth and continuous in an image, it is usually enough to be able to code at least 256 different levels of luminance, which should theoretically only require 8 bits.

[0064] As an example, Table 1 below comprises:-in the first column entitled "Gray Scale (8-bit)", the 256 gray scale values in decimal notation that can be codedwith 8 bits;-in the second column entitled "Ideal Linear (16-bit)", the corresponding ideal obtained values in decimal notation after a linear conversion that can be coded with 16 bits; -in the third column entitled "Ideal 2.2 (16-bit)", the corresponding ideal obtained values in decimal notation after a gamma conversion with yd equal to 2.2 that can be coded with 16 bits;-in the fourth column entitled "100% brightness", the corresponding real values in decimal notation after a multiplication by a decrease factor equal to 1;-in the fifth column entitled "50% brightness", the corresponding real values in decimal notation after a multiplication by a decrease factor equal to 0,5; and-in the sixth column entitled "25% brightness", the corresponding real values in decimal notation after a multiplication by a decrease factor equal to 0,25.

[0065] [Table 1]

[0066] Figure 8 shows examples of timing diagrams of signal PWM and signals I_red_100, I_red_50, and I_red_25 provided by circuit 50 of display pixel 12ifj of Figure 2 for the display of the same initial video data V_IN for three values of a brightness setting. The gamma corrected video data V_G for initial video data V_IN corresponds to the digital signal "1010101". Signal I_red_100 corresponds to a brightness equal to 100%, that is a decrease factor DF equal to 1, so that the brightness and gamma corrected video data V_GB also corresponds to the digital signal "1010101". Signal I_red_50 corresponds to a brightness equal to 50%, that is a decrease factor DF equal to 0.5, so that the brightness and gamma corrected video data V_GB corresponds to the digital signal "0101010". Signal I_red_25 corresponds to a brightness equal to 25%, that is a decrease factor equal DF to 0.25, so that the brightness and gamma corrected video data V_GB corresponds to the digital signal "0010101".

[0067] A brightness setting in the range from 0% to 100% can be achieved without requiring the generation of a very short time intervals . The gamma decoding operation is independent from the brightness command . The only additional circuit that is required to implement the brightness command in the previously disclosed embodiment is the use of a multiplier 66 . The selection and timing signal Comi supplied by selection and timing circuit 22 is , during a display phase , advantageously the same whatever the brightness setting is . Therefore , the structure of the selection and timing circuit 22 can be simple .

[0068] Various embodiments and variants have been described . Those skilled in the art will understand that certain features of these various embodiments and variants may be combined, and other variants will occur to those skilled in the art . In particular, the PWM modulation may be internally generated in the driver circuit 40 of display pixel 12i fj to avoid using signal Comi to generate it . Other embodiments may also use other electro-optical components such as organic light-emitting diodes .

[0069] Finally, the practical implementation of the described embodiments and variations is within the abilities of those skilled in the art based on the functional indications given hereabove .

Claims

CLAIMS1. Display screen (10) comprising an array of display pixels (12ifj) each comprising a least one light-emitting diode (LED) , the display screen further comprising a first circuit (60) configured to receive initial digital video data (V_IN) and to apply a gamma decoding to the received initial digital video data (V_IN) to produce gamma corrected digital video data (V_G) , a second circuit (62) configured to receive a brightness setting (B_SET) , a third circuit (64) configured to provide a digital decrease factor (DE) that depends on the brightness setting (B_SET) , and a fourth circuit (66) configured to multiply the gamma corrected digital video data (V_G) by the digital decrease factor (DE) to provide brightness and gamma corrected digital video data (V_GB) .

2. Display screen according to claim 1, wherein the display pixels (12ifj) are arranged in rows and columns, the display screen further comprising a data driver (24) configured to provide video data (Dataj) to the columns of display pixels (12ifj) based on the brightness and gamma corrected digital video data (V_GB) .

3. Display screen according to claim 2, wherein each display pixels (12ifj) comprises a driver circuit (40) configured to determine a digital signal (R, G, B) from the video data (Dataj) and to control the light-emitting diode (LED) based on the digital signal.

4. Display screen according to claim 3, wherein the driver circuit (40) is configured to control the light-emitting diode (LED) by pulse-width modulation based on the digital signal (R, G, B) .

5. Display screen according to any of claims 2 to 4, comprising a selection and timing circuit (24) configured to provide a succession of pulses to each row of display pixels (12ifj) .

6. Display screen according to claims 3 and 5, wherein the driver circuit (40) is configured to turn on or turn off the light-emitting diode (LED) at the rate of the succession of pulses.

7. Method for displaying images by a display screen (10) comprising an array of display pixels (12lfj) each comprising a least one light-emitting diode (LED) , comprising the following steps;-receiving initial digital video data (V_IN) ;-applying a gamma decoding to the received initial digital video data (V_IN) to produce gamma corrected digital video data (V_G) ;-receiving a brightness setting (B_SET) ; -providing a digital decrease factor (DE) that depends on the brightness setting (B_SET) ; -multiplying the gamma corrected digital video data (V_G) by the digital decrease factor (DE) to provide brightness and gamma corrected digital video data (V_GB) .

8. Method according to claim 7, wherein the display pixels (12lfj ) are arranged in rows and columns, the method further comprising the step of providing video data (Dataj) to the columns of display pixels (12lfj ) based on the brightness and gamma corrected digital video data (V_GB) .

9. Method according to claim 8, wherein each display pixels (12ifj) comprises a driver circuit (40) configured to determine a digital signal (R, G, B) from the video data (Dataj) and to control the light-emitting diode (LED) based on the digital signal.

10. Method according to claim 9 , wherein the driver circuit (40) is configured to control the light-emitting diode (LED) by pulse-width modulation based on the digital signal (R, G, B) .

11. Method according to any of claims 8 to 10, comprising providing a succession of pulses to each row of display pixels ( 121 , j ) .

12. Method according to claims 9 and 11, wherein the driver circuit (40) is configured to turn on or turn off the light-emitting diode (LED) at the rate of the succession of pulses.

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