Method for determining the state of a screen

Abstract

Method for Determining the State of a Display This description relates to a method for determining the state of a display (100) comprising a display panel (102) and a circuit (104). The circuit (104) controls the display panel (102) according to at least one periodic control mode, including a pulse-width modulation (PWM) control mode. The method comprises: acquiring a plurality of samples from a channel of an ambient light sensor (106) located under the display panel (102); providing the samples to a processing circuit (112, 110); detecting, by the processing circuit and based on the samples, whether the display panel (102) is controlled by pulse-width modulation; and, upon detection of a pulse-width modulation control, calculating by the processing circuit a duty cycle from said samples. Figure for the abstract: Fig. 1

Description

Title of the invention: Method for determining the state of a screen technical field

[0001] This description relates generally to electronic circuits, and, more particularly, to electronic devices comprising a screen and an ambient light sensor located under the screen. Previous technique

[0002] Devices each comprising a display, i.e. a set of a display panel and a display panel control circuit, and an ambient light sensor disposed under the display panel, i.e. opposite a rear face of the display panel opposite a front face of the display panel on which images displayed by the screen are shown, are known.

[0003] In each of these known devices, the screen constitutes a black box for the other circuits of the device, for example for a circuit comprising a microcontroller and a screen control circuit. Thus, when a command is provided to the screen, for example by the screen control circuit, for example, following a request from the microprocessor to this control circuit to adjust the brightness emitted by the screen, there are no output signals from the screen that would allow the state of the screen to be determined, that is to say, how the display panel control circuit actually controls the display panel following the command received by the screen, and, in particular, how the portion of the screen located above and opposite the ambient light sensor is actually controlled.

[0004] However, not knowing the state of the screen poses a problem for the implementation of various applications of the device. For example, when an ambient light measurement is requested from the ambient light sensor, the ambient light received by the sensor is weak due to its attenuation as it passes through the display panel before reaching the sensor pixels. Furthermore, when the display panel emits light, some of this emitted light is received by the sensor and distorts the ambient light measurement. Knowing the display panel's control mode via the display panel control circuit would allow the ambient light measurement result to be corrected and / or the duration(s) during which the sensor integrates the light it receives to be adjusted, in order to obtain a more accurate ambient light measurement result. Summary of the invention

[0005] There is a need to overcome all or part of the drawbacks of electrical devices Ironic known examples include a screen with a display panel and an ambient light sensor positioned below the display panel.

[0006] For example, there is a need, in these known devices, for a method of determining the state of the screen.

[0007] An embodiment overcomes all or part of the drawbacks of known electronic devices comprising a screen having a display panel and an ambient light sensor disposed under the display panel.

[0008] An embodiment provides a method for determining the state of a screen comprising a display panel and a display panel control circuit, wherein the display panel control circuit controls the display panel according to at least one periodic control mode, said at least one control mode comprising a pulse-width modulation control mode, and wherein the method comprises: 1) acquire a plurality of samples from at least one channel of an ambient light sensor positioned under the display panel during an initial acquisition period; 2) provide the samples to a processing circuit; 3) detect, via the processing circuit and based on said samples, whether the display panel is controlled according to the pulse-width modulation control mode; and 4) Following detection of the pulse width modulation control mode, calculate by the processing circuit a duty cycle of the pulse width modulation from said samples.

[0009] According to one embodiment: - the method further comprises, for each image displayed by the screen, the emission of a synchronization signal by the screen and the reception of the synchronization signal by a first circuit; and - in step 1), the first circuit triggers the first acquisition phase in a synchronized manner with respect to the synchronization signal.

[0010] According to one embodiment, a maximum period of the synchronization signal is known beforehand and the duration of the first acquisition phase is less than this maximum period of the synchronization signal.

[0011] According to one embodiment, the period of the pulse width modulation control mode is known beforehand and determines the duration of the first acquisition period.

[0012] According to one embodiment, a sample acquisition frequency during the first acquisition period is at least partly determined by a maximum duty cycle of the pulse-width modulation control mode and the pulse width modulation period, this maximum duty cycle and this pulse width modulation period being constant and known beforehand.

[0013] According to one embodiment, step 4) comprises, following detection of the pulse width modulation control mode, a determination by the first circuit and from said samples, of a difference between the intensity of the light received by said at least one channel when the display panel receives a pulse and is lit, and the intensity of the light received by said at least one channel when the display panel is off.

[0014] According to one embodiment, the at least one control mode further comprises a continuous control mode including, for each period of control in continuous control mode, an initialization time during which the display panel is off, step 3) further comprises detecting, by the first circuit and on the basis of said samples, whether the display panel is controlled according to the continuous control mode, and step 4) comprises, following the detection of the continuous control mode, a determination by the first circuit and from said samples, of a difference between the intensity of the light received by said at least one channel when the display panel is on, and the intensity of the light received by said at least one channel when the display panel is off.

[0015] According to one embodiment, in step 3), the detection of the continuous control mode includes a detection by the first circuit and from said samples, of the initialization time.

[0016] According to one embodiment, the frequency of sample acquisition during the first acquisition period is at least partly determined by the initialization time.

[0017] According to one embodiment, at least one control mode further includes an off control mode in which the display screen is kept off, and the method further includes a step of detecting whether the display panel is controlled according to the off control mode.

[0018] According to one embodiment, no synchronization signal is emitted in the off control mode, and detecting that the display panel's control mode is the off control mode includes detecting that no synchronization signal is emitted for a duration greater than one period of the synchronization signal.

[0019] According to one embodiment, steps 1), 2), 3) and 4) are implemented for each channel of the ambient light sensor.

[0020] According to one embodiment, the processing circuit is part of the ambient light sensor.

[0021] According to one embodiment, step 4) further includes a determination, by the processing circuit and from said samples, of a level of brightness emitted by said at least one channel. Brief description of the drawings

[0022] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the accompanying figures, among which:

[0023] Fig. 1 represents, schematically and in block form, an example of an embodiment of an electronic device of the type to which the described embodiments apply;

[0024] [Fig.2] represents, by means of a timing diagram, a control method for a display panel of a screen and steps of an implementation method for determining a state of the screen;

[0025] [Fig.3] represents, by way of a flowchart, an embodiment of the process of determining a state of the screen;

[0026] [Fig.4] illustrates, by means of chronograms, details of a method of implementation of a step in the process;

[0027] Figure 5 represents, by means of a timing diagram, another method of controlling the screen display panel and steps of an embodiment of the method for determining a screen state; and

[0028] [Fig.6] illustrates, by means of chronograms, details of an embodiment of a step in the process. Description of the embodiments

[0029] The same elements have been designated by the same reference numerals in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same reference numerals and may have identical structural, dimensional and material properties.

[0030] For the sake of clarity, only the steps and elements necessary for understanding the described embodiments have been shown and detailed. In particular, common applications, such as ambient light measurement, which require knowledge of a screen's state for their implementation, have not been detailed, as the described embodiments are compatible with these common applications.

[0031] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") together, this means that these two elements can be connected or linked through one or more other elements.

[0032] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "superior", "inferior", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures.

[0033] Unless otherwise specified, the expressions "approximately", "roughly", and "in the order of" mean within 10%, preferably within 5%.

[0034] Fig. 1 represents schematically and in block form an example of an embodiment of an electronic device 1 of the type to which the described embodiments apply.

[0035] The device 1 includes a screen 100 (block "DISPLAY"). The screen includes a display panel 102, preferably an organic light-emitting diode (OLED) display panel (block "PANEL"). The display panel 102 is controlled by a circuit 104 (block "DRIVER") of the screen 100. In other words, the circuit 104 is a control circuit for the display panel 102.

[0036] The device 1 further includes an ambient light sensor 106 (block "ALS"). The sensor 106 comprises a plurality of pixels for receiving light, this plurality of pixels being represented by a block 108 ("PIXELS") in [Fig. 1]. The sensor 106 further includes a control circuit 110 (block "ALS CTRL") for the pixels of the sensor 106.

[0037] The circuit 110 allows the pixels 108 of the sensor 106 to be controlled, for example so as to control the beginning and end of each acquisition phase where a quantity of light received by the pixels of the sensor 106 is measured.

[0038] The circuit 110 also allows to receive output signals from pixels 108, for example signals representative of, or determined by, a photo-current generated by each pixel.

[0039] The sensor 106 comprises at least one measurement channel, preferably several measurement channels corresponding to several respective wavelength ranges. The sensor 106 is configured, during an ambient light measurement, to measure the light received in each channel.

[0040] Thus, in each channel, the channel pixels provide an output signal to the circuit 110 which corresponds, for example, to a signal representative of the intensity of the light received in the channel's wavelength range by the channel pixels. For example, each channel provides an output signal corresponding to the sum of the photocurrents of the channel pixels. For example, the sensor 106 comprises three channels corresponding respectively to red light, green light, and blue light.

[0041] The circuit 110 is configured to sample, at an acquisition frequency Fa, the output signal of each sensor channel. In particular, circuit 110 includes one or more analog-to-digital converters (not shown in [Fig. 1]) configured, for each channel, to sample the channel's output signal at frequency Fa, and to convert each sample into a digital word corresponding to the value of that sample. For example, circuit 110 includes one analog-to-digital converter per channel.

[0042] During an ambient light measurement phase comprising one or more acquisition phases, the device 1 is, for example, configured to integrate the output signal of each channel over the entire duration of the measurement phase, that is, over the duration of all the acquisition phases of this ambient light measurement phase. For example, for each channel, this integration is performed on the digital samples obtained from the channel's output signal.

[0043] Although not visible in [Fig. 1], in device 1, the sensor 106, more precisely the pixels 108 of the sensor 106, are arranged under the display panel 102. Thus, the light received by the pixels 108 is attenuated compared to the ambient light, because this light has first passed through the display screen 102 before reaching the pixels 108 of the sensor 106. Furthermore, during an ambient light measurement phase comprising one or more acquisitions, depending on the start time and duration of each acquisition phase, this ambient light acquisition phase can at least partially be carried out while the display panel is emitting light. However, when the display panel emits light, some of the light is emitted towards sensor 106 and overlaps with the ambient light received by sensor 106, which reduces the signal-to-noise ratio and distorts the ambient light measurement.

[0044] The device further includes a processing and control circuit 112 (block "HOST"). The circuit 112 includes a microprocessor 114 (block "pC") enabling, for example, the processing of data, for example received from the sensor 106, and the provision of control signals, for example to the screen 100 and / or the sensor 106.

[0045] The circuit 112, for example its microprocessor 114, is configured to trigger ambient light measurements by the sensor 106. For example, for each measurement phase, the circuit 112 commands a start time for each measurement phase and / or a number of acquisition phases for the measurement phase and / or a start time for each acquisition phase and / or a duration for each acquisition phase.

[0046] According to one embodiment, the circuit 112, for example its microprocessor 114, is configured to receive the samples provided by the sensor 106. For example, for each ambient light measurement phase, the circuit 112, for example its microprocessor 114, determines an ambient light measurement result, by example the result of the ambient light measurement in each channel of the sensor 106, for example by integrating for each channel the corresponding samples over the duration of all the phase acquisition phases of ambient light measurement.

[0047] Alternatively, the circuit 112 receives only the result of the ambient light measurement, for example the result of the ambient light measurement in each channel of the sensor 106, the determination of the result of the ambient light measurement by the sensor 106 from the samples of the output signals of the channels of the sensor 106 being directly implemented in the sensor 106, for example in the circuit 110.

[0048] The circuit 112 includes a screen control circuit 116 (block "DISPLAY CTRL"). The circuit 116 is, for example, configured to receive commands from the microprocessor 114, and to provide corresponding commands to the screen 100, for example to the circuit 104 of the screen 100.

[0049] For example, a control signal sent by circuit 112 to circuit 104 determines a brightness setpoint for the display panel 102, and circuit 104 is then configured to adapt the control (or state) of the display panel according to this setpoint.

[0050] In addition, the circuit 112, for example its circuit 116, is configured to provide the screen 100, for example to the circuit 104, with the data corresponding to each image that the screen 100 displays via its display panel 102.

[0051] According to one embodiment, as will be seen in more detail later, to avoid display problems resulting from a difference in operating frequencies between the circuit 112 and the screen 100, the screen 100, for example its circuit 104, is configured to provide a Vsync synchronization signal to the circuit 112, for example to the circuit 114. The Vsync signal, called, for example, the vertical synchronization signal, is, for example, configured to indicate to the circuit 112, for example to the processor 114, that a new image can be displayed by the screen, which triggers, for example, the sending by the circuit 112 to the screen 100 of the data corresponding to this new image to be displayed.

[0052] As previously stated in the description of known devices comprising a screen and an ambient light sensor located beneath the screen, in device 1, the screen 100 is a black box. In other words, apart from the possible Vsync signal, the screen 100 provides no output signal that would allow the state of the screen to be determined, i.e., how the circuit 104 controls the display panel 102.

[0053] For example, when the circuit 104 is configured to control the display panel 102 using pulse-width modulation, no output signal from the screen 100 allows the duty cycle of the pulse-width modulation to be determined, particularly when this duty cycle changes following a modification of The brightness setting is sent to screen 100. Knowing this duty cycle, in addition to the Vsync signal, would allow, when ambient light measurement is implemented by sensor 106, for the start time and duration of each acquisition phase of the ambient light measurement to be adjusted so that this duration corresponds to the time between two successive pulses of the pulse-width modulation (PWM) screen control, and so that each acquisition phase is fully implemented for a corresponding period. This would allow each acquisition phase to be as long as possible for a given duty cycle, thereby increasing the signal-to-noise ratio.

[0054] Thus, a method for determining the state of the screen 100 is proposed here. This method includes acquiring samples by the sensor 106 and, from these samples, determining the state of the screen. In particular, when the circuit 104 controls the display panel 102 according to a pulse-width modulation (PWM) control mode, the method includes a step of detecting that the display panel 102 is controlled by PWM and, following such detection, a step of determining the duty cycle of the PWM. These steps of detecting a control mode and determining the properties of the detected control mode are implemented, using the acquired samples, by a processing circuit. The processing circuit is, for example, part of the sensor 106 or, for example, of the circuit 110.As an alternative example, this processing circuit is part of circuit 112, and corresponds, for example, to microprocessor 114. Examples of embodiments of this process will now be described in relation to Figures 2 to 6.

[0055] Figure 2 shows, by means of timing diagrams, a control method for the display panel 102 of the screen 100 and steps of an embodiment of a method for determining a state of the screen 100. The figure illustrates the evolution of the Vsync signal described previously, the control of the screen 102 by the circuit 104 ("DISPLAY CMD" in Figure 2) and the operation of the sensor 106 ("ALS CMD" in Figure 2). In the example in Figure 2, the control method for the panel 102 by the circuit 104 is a pulse-width modulation control method, although, in practice, the circuits of the device 1 other than the screen 100 do not have prior knowledge of the control method for the display panel 102.

[0056] As illustrated in the example in [Fig.2], the DISPLAY CMD command of display panel 102 is periodic with a TVSYNC period corresponding to the period of the Vsync signal.

[0057] Furthermore, in a pulse-width modulation control mode, as in [Fig. 2], each period of the Vsync signal comprises a plurality of pulses (PWM ON in [Fig. 2]) during each of which the display panel Display panel 102 emits light, with two successive PWM ON pulses separated by a PWM OFF period during which panel 102 does not emit light. The PWM ON pulses are supplied to the display panel at a frequency FPWM = 1 / TPWM, where TPWM is the pulse width modulation period. The duty cycle of the pulse width modulation is equal to the ratio of the duration of each PWM ON pulse to the duration of each PWM OFF period.

[0058] According to one embodiment, the TPWM period is constant, known beforehand and corresponds to a characteristic of the screen 100. This TPWM period value is, for example, provided by the manufacturer of the screen 100.

[0059] According to one embodiment, a maximum value of the duty cycle of the pulse width modulation is known beforehand and corresponds to a characteristic of the screen 100, for example provided by the screen manufacturer.

[0060] A first step of the process consists of a first FAST ACQ acquisition of samples by the sensor 106, for example for at least one channel of the sensor 106, preferably for each channel of the sensor 106. For example, the FAST ACQ phase includes, for at least channel and preferably for each channel, obtaining a photocurrent output of the channel and the analog-to-digital conversion of this output signal at the acquisition frequency Fa, the samples constituting the result of this analog-to-digital conversion.

[0061] By way of example, the frequency Fa has a different, preferably higher, value than the frequency Fa during the acquisition phase(s) of an ambient light measurement phase. By way of alternative example, the frequency Fa has the same value during the acquisition phase(s) of an ambient light measurement phase and during the FAST ACQ phase.

[0062] According to one embodiment, the duration of the FAST ACQ acquisition is greater than the TPWM period so as to capture at least one TPWM period of the pulse width modulation control mode.

[0063] According to one embodiment, a maximum value for the TVSYNC period of the Vsync signal is known beforehand, and the duration of the FAST ACQ acquisition is less than this maximum TVSYNC period value. For example, the TVSYNC period is constant, and the maximum TVSYNC period value is equal to the constant TVSYNC period value. Alternatively, the TVSYNC period can be changed during the operation of device 1, and the maximum TVSYNC period value corresponds to the largest possible value for the TVSYNC period.

[0064] According to one embodiment, the maximum value of the pulse-width modulation duty cycle corresponds to a minimum value for each PWM OFF duration, and the sample acquisition frequency Fa is at least partially de terminated by this maximum duty cycle value. Indeed, to obtain at least one sample during each PWM OFF duration of the FAST ACQ phase, the frequency Fa must be greater than or equal to twice 1 / D, where D is the duration of a PWM OFF phase for the maximum duty cycle value. Furthermore, to be able to measure with sufficient accuracy the duration of each PWM OFF phase captured during the FAST ACQ phase, the frequency Fa is chosen, for example, to be greater than 10 times 1 / D, preferably greater than 100 times 1 / D.

[0065] In practice, for a given location of the sensor 106, and more particularly of its pixels 108, under the panel 102 of the screen 100, it is possible to determine, either empirically or mathematically, a delay time Tdelay between the start of each Vsync signal, or, in other words, each pulse of the Vsync signal, and the start, for the pixels of the display panel 102 that are arranged above the sensor 106, of the first PWM OFF period that follows this pulse of the Vsync signal. This delay time Tdelay is constant for a given location of the sensor 106 under the panel 102, and changes when the location of the sensor 106 under the panel 102 is modified, for example between two devices 1.

[0066] In the example embodiment shown in [Fig. 2], the start of the FAST ACQ phase of the process is synchronized with the Vsync signal; for example, it begins with the Vsync signal. In another example not shown, the FAST ACQ phase begins at the end of the Tdelay period.

[0067] Synchronizing the FAST ACQ phase with the Vsync signal, knowing the TPWM period beforehand, makes it possible to reduce the minimum duration required for the FAST ACQ phase to capture at least one complete TPWM period. This allows, for example, a reduction in the duration of the FAST ACQ phase, and therefore the implementation time of the process, particularly since a decrease in the duration of the FAST ACQ phase leads to a decrease in the number of samples acquired during this phase, and therefore a decrease in the processing time of these samples.

[0068] When the method for determining the state of the screen 100 is implemented and allows, following the FAST ACQ acquisition of a sample by the sensor 106, and on the basis of these samples, the detection that the display panel is controlled in pulse width modulation, the sample processing circuit, for example the microprocessor 114 or the circuit 110, determines, also from these samples, a value of the duty cycle of the pulse width modulation.

[0069] For example, according to one embodiment, the processing circuit determines the duration of the PWM OFF and PWM ON phases from the samples and calculates the duty cycle from these durations. As an alternative example, the processing circuit determines only the duration of the PWM OFF phases from the samples and calculates the duty cycle from this duration and the period TPWM known beforehand.

[0070] By way of example, once the implementation of the method has made it possible to detect that the panel 102 is controlled in pulse width modulation, the duration of the PWM OFF phases and the duty cycle of this modulation, during a subsequent ALS MES phase of ambient light measurement which includes several AL ACQ acquisition phases, the start of each AL ACQ phase can be synchronized with the start of a corresponding PWM OFF duration using the Vsync signal, the previously known Tdelay duration, and the duty cycle determined by the implementation of the method, and, furthermore, the TACQ duration of each AL ACQ phase can be chosen to be equal to or substantially less than the PWM OFF duration. For example, the first AL ACQ phase of the AL MES measurement begins at the end of the Tdelay duration elapsed since a Vsync pulse, and the end of each AL ACQ phase is separated from the beginning of the next AL ACQ phase by a Tint duration equal to TPWM - TACQ.This allows for an increase in the signal-to-noise ratio compared to a case where each AL ACQ phase would be implemented in whole or in part during a PWM ON phase, or compared to a case where each AL ACQ phase would be fully implemented during a corresponding PWM OFF phase but would have a duration equal to the minimum duration of the PWM OFF phases, i.e. the duration of the PWM OFF phases corresponding to the maximum value of the duty cycle.

[0071] Although the AL MES phase is not fully represented in [Fig. 2], at the end of this phase, the amount of light received during all the AL ACQ phases of the AL MES phase, for example in at least one channel of the sensor 106, preferably in each channel of the sensor 106, is obtained in the form of one or more sensor output signals. By way of example, each output signal of a channel of the sensor 106 corresponds to the set of digital samples obtained during each AL ACQ phase from the output photocurrent of the channel.

[0072] At the end of the AL MES phase, the output signals of the channels of sensor 106 are processed, for example by sensor 106 directly or by circuit 112, so as to obtain a result of the ambient light measurement.

[0073] The result of the ambient light measurement allows the device 1, for example the microprocessor 114, to control a modification of the brightness of the display panel 102 to adapt to the measured ambient light conditions and / or the type of ambient light (outdoor light, light from a phosphorescent tube, light from a filament bulb) determined, the type of ambient light being, for example, determined from the relative quantities of light between the channels of the sensor 106 during the AL MES phase.

[0074] Figure 3 shows, by way of a flowchart, an embodiment of the method for determining the state of the screen 100. The method is implemented, in the example of the [Fig.3], in device 1 of the [Fig. 1].

[0075] At a step 300 (block "FAST ACQ") corresponding to the first FAST ACQ acquisition described in relation to [Fig.2], an acquisition period is implemented by the sensor 106, during which the sensor 106 generates samples of the output signal from at least one channel of the sensor 106, preferably from the output signal of each channel of the sensor 106.

[0076] In a subsequent step 302 (block "GET SAMPLES"), the samples obtained at the end of step 300 are provided to a processing circuit, for example a processing circuit that is part of the sensor 106 or a processing circuit that is part of the circuit 112, for example the microprocessor 114.

[0077] In a subsequent step 304 (block "PROCESS SAMPLES"), the processing circuit processes the samples to detect which control mode of the display panel 102 is used. According to one embodiment, the display panel 102 is configured to be controlled by the circuit 104 at least in an amplitude modulation control mode and the processing circuit is configured to detect whether the panel 102 is controlled in pulse width modulation.

[0078] Still at step 304, if the processing circuit detects that the display panel 102 is controlled in pulse width modulation, the processing circuit determines, again on the basis of the samples, a duty cycle of the pulse width modulation, preferably by determining beforehand the duration of the PWM OFF phases from the samples.

[0079] In a subsequent step 306 (block "GET DISPLAY STATE"), a screen state is determined. For example, if the sample processing circuit detects in step 304 that panel 102 is controlled with pulse width modulation and calculates the duty cycle of this modulation, the screen state includes an indication of this control mode, its duty cycle, and, for example, the duration of the PWM OFF phases. As an example, the screen state is provided to circuit 112, for example to the microprocessor 114 of circuit 112, or to sensor 106, for example to circuit 110 of sensor 106.

[0080] In an optional subsequent step 308 ("ADAPT AL SENSING"), the parameters of a subsequent AL MES phase of ambient light measurement by the sensor 106 are adapted according to the screen state. For example, the TACQ, Tint, and synchronization parameters of the AL MES phase with the Vsync signal are adapted when the screen is controlled by pulse-width modulation based on the duty cycle value of this modulation. However, in other embodiments, the screen state determined at the end of step 306 can be used for the implementation of steps other than step 308, for example, to allow, during an indirect time-of-flight measurement by an indirect time-of-flight sensor, the emission of a laser beam that used for this time-of-flight measurement is implemented during a PWM OFF phase of the pulse width modulation.

[0081] Figure 4 illustrates, by means of chronograms, details of one embodiment of a step of the process described previously. More specifically, [Fig. 4] illustrates details of an embodiment of step 304 of the process for one channel of sensor 106, it being understood that this step 104 can be implemented for each channel of sensor 106 for which samples have been obtained at the end of step 302. In [Fig. 4], the channel samples obtained by the processing circuit at the end of step 302 for one channel of sensor 106 are shown as a function of time (on the x-axis), with the value of each sample shown on the y-axis. In [Fig. 4], the samples were acquired during a FAST ACQ phase implemented while panel 102 was driven in pulse-width modulation.

[0082] Step 304 includes classifying the channel samples against a TH threshold.

[0083] By way of example, the TH threshold is determined beforehand empirically.

[0084] By way of alternative example, phase 304 includes a determination of the TH threshold, for example from the samples. For example, among the samples received for the channel, a given number of samples with the highest values ​​is used to calculate a high value H (not shown in [Fig.3]) corresponding to the average value of these highest value samples, and, similarly, the same given number of samples with the highest values ​​is used to calculate a low value L (not shown in [Fig.3]) corresponding to the average value of these highest value samples, and the threshold TH is then equal to (H+L) / 2.

[0085] The classification of the samples with respect to the threshold TH makes it possible to determine the samples having a value greater than the threshold TH which are considered to correspond to moments when the panel 102 emits light, i.e. samples acquired during a PWM ON period in a pulse width modulation control mode, and the samples having a value less than the threshold TH which are considered to correspond to moments when the panel 102 does not emit light, i.e. samples acquired during a PWM OFF period in a pulse width modulation control mode.

[0086] Thus, it is possible to determine the duration of the phases when the panel 102 does not emit light, that is, the duration of the PWM OFF phases when the panel 102 is controlled by pulse-width modulation. For example, for each group of successive samples having values ​​below the TH threshold, the duration is calculated, which is equal to the number of samples in the group multiplied by the sample acquisition period equal to 1 / Fa, and the determined value of the duration of the PWM OFF phases is then equal to an average value of these calculated durations. Similarly, it It is possible to determine a value for the duration of PWM ON phases from successive groups of samples having values ​​above the threshold.

[0087] Preferably, when step 304 is implemented for multiple channels of the sensor 106, a PWM OFF phase duration value is determined for each channel, and the PWM OFF phase duration value determined in step 304 corresponds to the average of the PWM OFF phase duration values ​​determined for those channels. This provides a more accurate PWM OFF phase duration value. Similarly, a PWM ON phase duration value can correspond to the average of the PWM ON phase duration values ​​determined for those channels.

[0088] From the determined duration of the PWM OFF phases and prior knowledge of the TPWM period and / or the determined duration of the PWM ON phases, a duty cycle value is calculated in step 304.

[0089] When the circuit 104 controls the panel 102 in pulse width modulation, the determination of the state of the screen 100 further includes, optionally, for each channel for which step 304 is implemented, the determination of the amplitude of the PWM ON pulses, or, in other words, the difference AMP between the intensity of the light received by the channel during the PWM ON pulses corresponding to phases where the panel 102 emits light and the intensity of the light received during the PWM OFF phases when the panel 102 does not emit light.

[0090] By way of example, to determine the AMP difference of a channel, an average value avgH of the channel samples having values ​​above the TH threshold of the channel is calculated, an average value avgL of the channel samples having values ​​below the TH threshold of the channel is calculated and the AMP difference is then equal to avgH minus avgL.

[0091] This step of calculating the AMP amplitude for each channel of the sensor 106 for which step 304 is implemented, for example, when, in pulse width modulation control mode, once the maximum value of the duty cycle is reached, i.e. the duration of the PWM OFF phases is equal to D, the amplitude of the PWM ON pulses applied to the panel 102 by the circuit 104 can be modified, for example increased, by the circuit 104 to modify, for example increase, the intensity of the light emitted by the screen 100. In this case, the state of the screen is partly determined by the difference AMP calculated for each channel for which step 304 is implemented.

[0092] The case where circuit 104 controls panel 102 using pulse-width modulation, with or without variable amplitude of these PWM ON pulses, has been described above in relation to Figures 1 to 4. According to one embodiment, the The process also makes it possible to detect when circuit 104 controls panel 102 in an off control mode, in which panel 102 is kept off by circuit 104.

[0093] According to one embodiment, this detection that the panel 102 is controlled according to the control mode off is implemented by detecting an absence of Vsync signal, that is to say an absence of Vsync pulses, over a period greater than the TVSYNC period of the Vsync pulses, for example over a period greater than the maximum value of the TVSYNC period when this maximum value is known beforehand.

[0094] The case where circuit 104 controls panel 102 in at least one control mode, comprising a pulse-width modulation (PWM) control mode, for example with or without variable amplitude of these PWM pulses (PWM ON), and, for example, an off control mode, has been described above with reference to Figures 1 to 4. According to one embodiment, the method also makes it possible to detect when circuit 104 controls panel 102 in a continuous control mode, as will now be described with reference to Figures 5 and 6.Indeed, although there are devices 1 in which the panel 102 is, for example, selectively controlled in off mode or in pulse width modulation only mode, there are also devices 1 in which the panel 102 is, for example, selectively controlled in off mode or in pulse width modulation or in continuous mode, and the method must then be able to detect the control mode of the panel 102.

[0095] Figure 5 represents, by means of timing diagrams, a control mode for the display panel 102 of the screen 100 and steps of an embodiment of a method for determining a state of the screen 100. Figure 5 illustrates the evolution of the Vsync signal described previously, the DIS PLAY CMD command of the screen 102 by the circuit 104 and the ALS CMD operation of the sensor 106. In the example of Figure 5, the control mode of the panel 102 by the circuit 104 is a continuous control mode, although, in practice, the circuits of the device 1 other than the screen 100 do not have prior knowledge of the control mode of the display panel 102.

[0096] As illustrated in the example in [Fig.5] and as already indicated in relation to [Fig.2], the DISPLAY CMD command of display panel 102 is periodic with a TVSYNC period corresponding to the period of the Vsync signal.

[0097] In continuous control mode, as illustrated in [Fig. 5], for each TVSYNC period, circuit 104 provides panel 102 with a constant DISPLAY CMD control signal throughout the entire TVSYNC period, except for a short DC OFF initialization period during which control circuit 104 commands panel 102 not to emit light. In continuous control mode, two successive DC OFF phases are therefore separated from each other by a DC ON phase where panel 102 is lit.

[0098] This DC OFF period is, for example, necessary for the proper functioning of the pixels of panel 102, and corresponds, for example, in each pixel of panel 102 to an initialization of a pixel capacity.

[0099] The duration of the DC OFF periods is preferably constant and known in advance. For example, the duration of the DC OFF periods is provided by the manufacturer of the screen 100.

[0100] In some embodiments, the duration of each DC OFF phase is less than the minimum duration D of the PWM OFF phases when the duty cycle of the pulse-width modulation is at its maximum. In an embodiment where the panel 102 is selectively controlled according to at least the continuous mode and the pulse-width modulation mode, the sample acquisition frequency Fa during the FAST AQC phase is at least partially determined by the duration of the DC OFF phases of the continuous control mode. Indeed, in order to obtain at least one sample during each DC OFF duration of the FAST ACQ phase, the frequency Fa must be greater than or equal to twice the inverse of the DC OFF duration. Furthermore, in order to measure with sufficient accuracy the duration of a DC OFF phase captured during the FAST ACQ phase, the frequency Fa is, for example, chosen to be greater than ten times the inverse of the DC OFF duration, preferably one hundred times the inverse of the DC OFF duration..

[0101] In practice, the DC OFF duration is synchronized with the Vsync signal, and, for the pixels of the panel 102 arranged above the sensor 106, each DC OFF duration begins at the end of the Tdelay period which began during a corresponding Vsync pulse.

[0102] The method includes, as described previously with reference to Figures 2 and 3, a FAST ACQ step (step 300 in [Fig. 2]) for acquiring samples by the sensor 106, for example, for at least one channel of the sensor 106, preferably for each channel of the sensor 106. This FAST ACQ step is identical to that described previously. The samples acquired during the FAST ACQ phase are then supplied to the processing circuit (step 302 in [Fig. 2]), and the processing circuit detects, from the samples, whether the panel 102 is controlled in continuous mode or whether the panel is controlled in continuous mode (step 304 in [Fig. 2]).

[0103] In the example embodiment shown in [Fig. 5], the start of the FAST ACQ phase of the process is synchronized with the Vsync signal; for example, it begins with the Vsync signal. In another example not shown, each FAST ACQ phase is synchronized with the Vsync signal and begins at the end of a corresponding Tdelay period. Thus, by ensuring that the duration of the FAST ACQ phase is at least equal to that of a TPWM period (not shown in [Fig.5], see [Fig.2]), we ensure that a complete DC OFF duration is captured during the FAST ACQ phase.

[0104] By way of example, when the duration of the FAST ACQ phase is at least equal to twice the TPWM period, the detection that the control mode of panel 102 is continuous mode consists of detecting that there is only one period during which panel 102 is off over the entire duration of the FAST ACQ phase.

[0105] As an alternative example, when the duration of the DC OFF phases is constant and less than the minimum duration D of the PWM OFF periods, the detection that the control mode of panel 102 is the continuous mode consists of detecting (step 304 in [Fig.2]), over the duration of the FAST ACQ phase and from the samples, a phase during which panel 102 is off and that the duration of this phase where panel 102 is off is less than the duration D. Indeed, this indicates that the duration during which panel 102 is off is a DC OFF duration of the continuous control mode, and not a PWM OFF duration of the pulse-width modulation control mode. In this alternative example, when the FAST ACQ phase is synchronized to the Vsync signal so that the FAST ACQ phase includes a DC OFF phase when panel 102 is driven in continuous mode, the duration of the FAST ACQ phase can be reduced to a maximum of the constant duration of one TPWM period.

[0106] When the method for determining the state of the screen 100 is implemented and allows, following the FAST ACQ acquisition of samples by the sensor 106, and on the basis of these samples, the detection that the display panel is continuously controlled, the sample processing circuit further determines, for at least one channel, and preferably for each channel, a difference between the intensity of the light received by said at least one channel when the display panel is off (DC OFF phase) and the intensity of the light received by said at least one channel when the display panel is on (DC ON phase).

[0107] By way of example, once the implementation of the method has detected that the panel 102 is continuously driven, and, for at least one channel, preferably for each channel, a difference in received light intensity between the DC ON and DC OFF phases, during a subsequent AL MES phase of ambient light measurement, one or more AL ACQ acquisition phases, preferably a single AL ACQ phase, are implemented during a corresponding DC ON phase. Although the AL MES phase is not fully shown in [Fig. 2], at the end of this AL MES phase, the value of the obtained samples can then be corrected, preferably in each channel for which step 304 was implemented, by subtracting from these samples the value of the intensity difference calculated for that channel in step 304. This amounts to correcting the result of the ambient light measurement by removing the noise resulting from the light emission by the screen 100.

[0108] Figure 6 illustrates, by means of timing diagrams, details of an embodiment of a step in the process described above. More specifically, Figure 6 illustrates details of an embodiment of step 304 of the process for one channel of sensor 106, it being understood that this step 104 can be implemented for each channel of sensor 106 for which samples have been obtained at the end of step 302. In Figure 6, the channel samples obtained by the processing circuit at the end of step 302 for one channel of sensor 106 are shown as a function of time (on the x-axis), with the value of each sample shown on the y-axis. In Figure 6, the samples were acquired during a FAST ACQ period implemented while panel 102 was continuously controlled.

[0109] Step 304 ([Fig.3]) includes the ranking of the channel samples with respect to at the TH threshold.

[0110] By way of example, the TH threshold is determined beforehand empirically as has already been indicated in relation to [Fig.4].

[0111] By way of alternative example, step 304 includes a determination of the TH threshold, for example from the samples. For example, among the samples received for the channel, a given number of samples with the highest values ​​is used to calculate a high value H (not shown in [Fig. 6]) corresponding to the average value of these highest-value samples, and, similarly, the same given number of samples with the highest values ​​is used to calculate a low value L (not shown in [Fig. 6]) corresponding to the average value of these highest-value samples, and the TH threshold is then equal to (H+L) / 2.Preferably, the given number of samples used to calculate the H and L values, and therefore the TH threshold, is less than or equal to the number of samples that can be acquired at frequency Fa during a DC OFF time, so that the samples with the lowest values ​​correspond only to samples acquired during a DC OFF time when panel 102 is continuously controlled as in [Fig.6].

[0112] The classification of the samples with respect to the threshold TH makes it possible to determine the samples having a value above the threshold TH which are considered to correspond to times when the panel 102 emits light, i.e. samples acquired during a DC ON period in a continuous control mode, and the samples having a value below the threshold TH which are considered to correspond to times when the panel 102 does not emit light, i.e. samples acquired during a DC OFF period in a continuous control mode.

[0113] Thus, it is possible to determine the duration of the phases when the panel 102 does not emit light, that is to say, the duration of a DC OFF phase when the panel is continuously controlled. For example, for each group of successive samples having values ​​below the TH threshold, the duration is calculated, which is equal to the number The number of samples in the group multiplied by the sample acquisition period equals 1 / Fa, and the determined value for the duration of the phases where the panel does not emit light is then equal to an average value of these calculated durations. Similarly, it is possible to determine a value for the duration of the phases where panel 102 emits light from successive groups of samples having values ​​above the threshold.

[0114] Preferably, when step 304 is implemented for several channels of the sensor 106, a value for the duration of the phases during which the panel 102 does not emit light is determined for each channel, and the value for the duration of the phases during which the panel does not emit light determined in step 304 corresponds to the average of the values ​​for the durations determined for these channels. This allows for a more accurate value for the duration of the phases during which the panel does not emit light. Similarly, a value for the duration of the phases during which the panel 102 emits light can correspond to the average of the values ​​for the durations of the phases during which the panel 102 does not emit light that were determined for these channels.

[0115] When the panel 102 is controlled according to a control mode selected from the pulse width modulation control mode and the continuous control mode, step 304 includes detecting which of the two above modes is currently being used to control the panel 102.

[0116] By way of example, when the FAST ACQ phase has a duration greater than twice TPWM, this detection includes counting the number of successive sample groups that are below the TH threshold, i.e., the number of phases where panel 102 does not emit light during the duration of the FAST ACQ phase. If this number is equal to 1, it means that the control mode is continuous control mode. If this number is greater than 1, it means that the control mode is pulse-width modulation control mode.

[0117] By way of alternative example, in an embodiment where the duration of the DC OFF phases is shorter than the duration D of the PWM OFF phases when the pulse-width modulation duty cycle is at its maximum, once the duration of the phase(s) during which the panel 102 does not emit light has been determined as described above, the detection of the control mode of the screen 102 includes comparing this determined duration with the duration D. If the determined duration is greater than or equal to the duration D, this means that the panel 102 is controlled by pulse-width modulation, and the previously determined duration corresponds to the duration of the PWM OFF phases. Conversely, if this determined duration is less than the duration D, this means that the panel 102 is controlled continuously, and the previously determined duration corresponds to the duration of the DC OFF phases.

[0118] When, in step 304, it is detected that panel 102 is continuously controlled, the Determining the state of screen 100 further includes, for each channel for which step 304 is implemented, determining the amplitude of the DC ON command, or, in other words, the AMP difference between the intensity of the light received by the channel during a DC ON phase and the intensity of the light received during a DC OFF phase. This step of determining the AMP difference for a channel from the samples acquired for that channel is implemented in the same way as in [Fig. 4], for example, by determining the values ​​avgH and avgL and calculating the AMP difference equal to avgH minus avgL.

[0119] Embodiments in which the panel 102 is controlled according to a control mode selected from at least one control mode, for example from at least the pulse width modulation control mode, or, for example, from the pulse modulation control mode and the continuous control mode.

[0120] Embodiments and variant embodiments in which the FAST ACQ phase is synchronized with the Vsync signal have been described previously. In variant embodiments, in addition to the Vsync synchronization signal comprising one Vsync pulse per displayed image, the screen 100, for example its circuit 104, provides an additional Hsync synchronization signal comprising one Hsync pulse per displayed image line, and the FAST ACQ phase is further synchronized to the Hsync signal. This Hsync signal is, for example, called the horizontal synchronization signal.

[0121] In yet other embodiments, the FAST ACQ phase is implemented asynchronously with the Vsync signal and any Hsync signal, for example in a device 1 where this Vsync signal is not supplied by the screen 100 to the other circuits of device 1. In this case, the duration of the FAST ACQ phase is at least equal to the maximum duration of the TVSYNC period, so that, in continuous control mode, at least one DC OFF phase is captured during the FAST ACQ phase. Those skilled in the art will be able to adapt the above description in relation to Figures 1 to 6 to this asynchronous operation.In this asynchronous operation, determining whether the control mode is continuous control mode or pulse-width modulation control mode is then implemented, based on the samples, for example by calculating the shortest of the captured durations where panel 102 does not emit light during the FAST ACQ phase and comparing this shortest duration with the minimum duration D of the PWM OFF phases. Furthermore, in this asynchronous operation, detecting that the control mode is the off control mode, i.e., a control mode where panel 102 is kept off for the entire duration of each TVSYNC period, can include detecting the value difference between the... samples with the lowest values ​​and samples with the highest values ​​is less than threshold, this threshold being determined for example by the minimum amplitude of the PWM ON pulses and the constant DC ON control.

[0122] In all the embodiments and variants described above, according to one embodiment, determining the state of the screen 100 (step 306 of [Fig. 2]) includes determining the brightness emitted by the display panel 102, for example, the average brightness emitted by the panel 102 during a TVSYNC control period of the panel 102. This emitted brightness can be calculated for each channel of the sensor 106 for which the method is implemented. By way of example, the brightness emitted by the panel 102 is calculated, in each channel, from the calculated AMP difference for that channel, the detected control mode, and the modulation duty cycle and the TPWM period when the detected control mode is pulse-width modulation control mode, or from the duration of the DC OFF phase and the TVSYNC period when the detected control mode is continuous control mode.

[0123] Various embodiments and variations have been described. A person skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will become apparent to a person skilled in the art.

[0124] Finally, the practical implementation of the embodiments and variants described is within the reach of a person skilled in the art, based on the functional indications given above.

Claims

Claims

1. A method for determining a state of a screen (100) comprising a display panel (102) and a circuit (104) for controlling the display panel, wherein the circuit (104) for controlling the display panel controls the display panel (102) according to at least one periodic control mode (TVSYNC), said at least one control mode comprising a pulse width modulation control mode (PWM ON, PWM OFF), and wherein the method comprises: 1) acquiring a plurality of samples of at least one channel of an ambient light sensor (106) arranged under the display panel (102) during a first acquisition period (FAST ACQ, 300); 2) providing (302) the samples to a processing circuit (112, 110); 3) detecting (304), by the processing circuit and on the basis of said samples, whether the display panel (102) is controlled according to the pulse width modulation control mode;and 4) following detection of the pulse width modulation control mode, calculating (304) by the processing circuit a duty cycle of the pulse width modulation from said samples.;

2. Method according to claim 1, in which: - the method further comprises, for each image displayed by the screen (100), the transmission of a synchronization signal (Vsync) by the screen (100) and the reception of the synchronization signal by a first circuit (110; 112, 114); and - in step 1), the first circuit (110; 112, 114) triggers the first acquisition phase (FAST ACQ) in a synchronized manner with respect to the synchronization signal (Vsync).

3. Method according to claim 2, in which a maximum period (TVSYNC) of the synchronization signal (Vsync) is previously known and the duration of the first acquisition phase (FAST ACQ) is less than this maximum period of the synchronization signal.

4. Method according to claim 2 or 3, in which the period (TPWM) of the pulse width modulation control mode (PWM ON, PWM OFF) is previously known and determines the duration of the first acquisition period (FAST ACQ).

5. A method according to any one of claims 1 to 4, wherein a frequency of acquisition of the samples during the first acquisition period (FAST ACQ) is at least partly determined by a maximum duty cycle of the pulse width modulation control mode (PWM ON, PWM OFF) and the period (TPWM) of the pulse width modulation, this maximum duty cycle and this period of the pulse width modulation being constant and known beforehand.

6. Method according to any one of claims 1 to 5, in which step 4) comprises, following the detection of the pulse width modulation control mode (PWM ON, PWM OFF), a determination by the first circuit (110; 112, 114) and from said samples, of a difference (AMP) between the intensity of the light received by said at least one channel when the display panel (102) receives a pulse (PWM ON) and is switched on, and the intensity of the light received by said at least one channel when the display panel (102) is switched off (PWM OFF).

7. A method according to any one of claims 1 to 6, wherein said at least one control mode further comprises a continuous control mode (DC ON, DC OFF) comprising, for each period (TVSYNC) of control in continuous control mode (DC ON, DC OFF), an initialization duration (DC OFF) where the display panel (102) is switched off, step 3) further comprises detecting, by the first circuit (110; 112, 114) and on the basis of said samples, whether the display panel (102) is controlled according to the continuous control mode (DC ON, DC OFF), and step 4) comprises, following detection of the continuous control mode, a determination by the first circuit (110;112, 114) and from said samples, a difference (AMP) between the intensity of the light received by said at least one channel when the display panel (102) is on (DC ON), and the intensity of the light received by said at least one channel when the display panel (102) is off (DC OFF).;

8. Method according to claim 7, wherein, in step 3), the detection of the continuous control mode (DC ON, DC OFF) comprises a detection by the first circuit (110; 112, 114) and from said samples, of the initialization duration (DC OFF).

9. Method according to claim 7 or 8 taken in its dependence on claim 5, in which the frequency of acquisition of the samples during the first acquisition period (FAST ACQ) is at least in part determined by the initialization duration (DC OFF).

10. The method of any one of claims 1 to 9, wherein said at least one control mode further comprises an off control mode in which the display screen (102) is kept off, and the method further comprises a step of detecting whether the display panel (102) is controlled according to the off control mode.

11. The method of claim 10 as dependent on claim 2, wherein no synchronization signal (Vsync) is output in the off-drive mode, and detecting that the drive mode of the display panel (102) is the off-drive mode comprises detecting that no synchronization signal (Vsync) is output for a duration greater than one period (TVSYNC) of the synchronization signal.

12. A method according to any one of claims 1 to 11, wherein steps 1), 2), 3) and 4) are implemented for each channel of the ambient light sensor (106).

13. A method according to any one of claims 1 to 12, wherein the processing circuit (110) is part of the ambient light sensor (106).

14. Method according to any one of claims 1 to 13, in which step 4) further comprises a determination, by the processing circuit (110; 112, 114) and from said samples of a brightness level emitted by said at least one channel.

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