Proximity capture device

Abstract

Proximity capture device This description relates to a proximity capture device (400) comprising: - a proximity sensor (100) comprising a light emitter (110) and a light detector (120) having a first photodiode (121) generating a first signal (DNN) when it detects a first light signal (SN) emitted by the light emitter and reflected by an object (20), and a second photodiode (122) generating a second signal (DNF) when it detects a second light signal (SF) emitted by the light emitter and reflected by the object; the proximity sensor generating an output signal (DN) as a function of the first and second signals by weighting one of the first and second signals by a weighting coefficient (α);and a control circuit (410) adapted to receive the output signal and to: - transition from a first state (S2), in which the weighting coefficient has a first value (α1), to a second state (S3) when the output signal crosses a first threshold; - in the second state (S3), apply a second value (α2) to the weighting coefficient; and - compare the output signal obtained by applying the second value (α2) with a second threshold (TH1) so as to transition from the second state to a third state (S4) if the output signal is below the second threshold, or to transition from the second state to a fourth state (S1) if the output signal is above the second threshold. Figure for the abbreviation: Fig. 4;

Description

Title of the invention: Proximity capture device technical field

[0001] This description relates generally to electronic devices, more particularly to electronic devices comprising a proximity sensor, for example a proximity sensor located under a display screen. Prior art

[0002] A proximity sensor generally comprises a light emitter and a light detector. The general principle of a proximity sensor is that the emitter emits a beam of light, for example, an infrared beam, which is reflected by an object and detected by the detector. The detector may comprise one or more photodiodes. The proximity sensor may be connected to, or comprise, a processing unit configured to process a signal from the detector for a proximity detection calculation. For example, the signal may have a value, such as an amplitude or a number of pulses, that varies with the distance between the object and the detector, and the processing unit may process this signal to determine whether or not an object is present near the proximity sensor.

[0003] The proximity sensor can be of the time-of-flight (ToF) type, and in this case, the processing unit can be configured to calculate the travel time between the emission of the light beam and its reception by the detector, the distance between the object and the proximity sensor can then be deduced on the basis of this travel time.

[0004] Electronic devices comprising a proximity sensor located under a screen, for example a display screen, are known. The display screen may be an organic light-emitting diode (OLED) type screen. A proximity sensor under the display screen of a smartphone can detect the presence of a user against the screen, for example, when they press their ear against the screen to make a call, which can cause the screen to turn off. The proximity sensor can detect if the user moves away from the screen in order to cause the screen to turn back on.

[0005] It has been observed that, when a proximity sensor is positioned under a screen with low light transmittance, for example an OLED display screen, the proximity sensor may fail to distinguish whether the object is at a very short distance (very close object), typically a few millimeters away, for example less than 2 or 3 millimeters, or at a long distance (distant object), typically more than a few centimeters away, for example more than 20, 30 or even 40 millimeters, from said sensor. The example of the user and the smartphone described above, this could compromise the display turning off when the user is very close to the screen and / or the screen turning back on when they move away from the screen. Summary of the invention

[0006] There is a need for an electronic device, comprising at least a display screen and a proximity sensor under the display screen, more generally under a wall with low light transmittance, capable of determining whether an object is at a very short or long distance.

[0007] A proximity capture device is also sought, that is to say a device comprising a proximity sensor, capable of determining whether an object is at a very short or long distance with a simple solution to implement.

[0008] One embodiment overcomes all or part of the drawbacks of known proximity sensors.

[0009] One embodiment provides a proximity capture device comprising: - a proximity sensor comprising a light emitter and a light detector having at least a first photodiode adapted to generate a first signal when it detects a first light signal emitted by the light emitter and reflected by an object, and a second photodiode adapted to generate a second signal when it detects a second light signal emitted by the light emitter and reflected by the object; the proximity sensor being adapted to deliver an output signal as a function of the first and second signals, weighting one of the first and second signals by a weighting coefficient; and - a control circuit adapted to receive the output signal and to: - to move from a first state, in which the weighting coefficient has a first value, to a second state when the output signal crosses a first threshold; - in the second state, apply to the weighting coefficient a second value different from the first value; and - compare the output signal obtained by applying the second value with a second threshold so as to move from the second state to a third state if the output signal is less than the second threshold, or to move from the second state to a fourth state if the output signal is greater than the second threshold.

[0010] An embodiment provides a method for processing an output signal delivered by a proximity sensor comprising a light emitter and a light detector having at least a first photodiode adapted to generate a first signal when it detects a first light signal emitted by the light emitter and reflected by an object, and a second photodiode adapted to generate a second signal when it detects a second light signal emitted by the light emitter. and reflected by the object; the output signal being determined as a function of the first and second signals, by weighting one of the first and second signals by a weighting coefficient; the process comprising transmitting the output signal to a control circuit which: - goes from a first state, in which the weighting coefficient has a first value, to a second state when the output signal crosses a first threshold; - in the second state, apply to the weighting coefficient a second value different from the first value; and - compares the output signal obtained by applying the second value with a second threshold so as to move from the second state to a third state if the output signal is less than the second threshold, or to move from the second state to a fourth state if the output signal is greater than the second threshold.

[0011] According to one embodiment, the third state corresponds to a first distance between the object and the proximity sensor, and the fourth state corresponds to a second distance between the object and the proximity sensor, the second distance being greater than the first distance, or the first distance being greater than the second distance.

[0012] According to one embodiment, the output signal is obtained by subtracting the other of the first and second signals from the signal weighted by the weighting coefficient. In other words, one of the first and second signals is weighted by the weighting coefficient, forming the weighted signal, while the other of the first and second signals is not weighted by the weighting coefficient and is subtracted from the weighted signal.

[0013] According to one embodiment, the output signal is pre-processed by a proximity sensor processing device, the processing device being connected to the control circuit.

[0014] According to one embodiment, the light emitter and the light detector are positioned under a covering wall of the proximity sensor.

[0015] According to one embodiment, the first and second photodiodes are arranged next to each other, and spaced apart by a distance, in a direction substantially parallel to the plane of the covering wall.

[0016] According to one embodiment, the cover wall has a first opening at the light emitter, and a second opening at the light detector, for example the second opening is centered with the first photodiode, the second photodiode being positioned substantially under an unopened portion of the cover wall.

[0017] According to one embodiment, the first photodiode is positioned between the emitter and the second photodiode.

[0018] According to one embodiment, the proximity sensor is under a wall capable of generating a crosstalk phenomenon by reflection on said wall of light signals emitted by the light emitter and then transmitted to the light detector, for example the wall has a light transmission coefficient of less than 5% at the working wavelengths of the proximity sensor.

[0019] According to one embodiment, the control circuit is adapted to generate a status signal, the status signal comprising a first value in the third state and a second value in the fourth state.

[0020] According to one embodiment, the wall is a display screen, for example an OLED type display screen, and the status signal is adapted to be transmitted to the display screen, or a control circuit of said display screen, so as to control its extinction, or its illumination, depending on whether the status signal takes the first value or the second value.

[0021] According to one embodiment, the control circuit generates a status signal, the status signal comprising a first value in the third state and a second value in the fourth state.

[0022] According to one embodiment, the wall is a display screen, for example an OLED type display screen, and the status signal is transmitted to the display screen, or a control circuit of said display screen, so as to control its switching off or on, depending on whether the status signal takes the first value or the second value. Brief description of the drawings

[0023] 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:

[0024] [Fig.1] represents a proximity sensor included in an electronic device and positioned under a display screen of the electronic device and illustrates a mode of operation of such a proximity sensor;

[0025] Fig. 2A and Fig. 2B illustrate an application of a proximity sensor to turn a display screen on or off;

[0026] [Fig.3] represents curves of evolution of signals generated by the photodiodes of the proximity sensor of [Fig.1] as a function of the distance between the proximity sensor and an object, and for several numbers of measurement samples;

[0027] [Fig.4] represents a proximity capture device according to one embodiment, included in an electronic device and positioned under a display screen of the electronic device;

[0028] Fig. 5A represents an example of an embodiment of the control circuit of the proximity capture device of the [Fig.4];

[0029] [Fig. 5B] illustrates an example of the operation of the control circuit of [Fig. 5A]; and

[0030] [Fig.6] represents an evolution curve of the output signal of the proximity sensor of [Fig.4], and the different states of the control circuit of [Fig.5A] as a function of the distance between the proximity sensor and an object. Description of the implementation methods

[0031] 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.

[0032] For the sake of clarity, only the steps and elements necessary for understanding the described embodiments have been shown and are detailed. In particular, not all the components of an electronic device incorporating a proximity sensor under a display screen have been detailed, as the described embodiments are compatible with conventional electronic devices including a proximity sensor under a display screen. Similarly, not all the components of a proximity sensor have been detailed, as the described embodiments are compatible with conventional proximity sensors.

[0033] 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.

[0034] 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 or to a proximity sensor in a normal operating position.

[0035] Unless otherwise specified, the expressions "approximately", "roughly", and "in the order of" mean within 10%, preferably within 5%.

[0036] The light transmittance, or transmission coefficient, of an element is defined as the fraction of the light intensity passing through that element.

[0037] Fig. 1 represents a proximity sensor 100 included in an electronic device 10 and positioned under a display screen 12 (DISPLAY) of the electronic device, and illustrates a mode of operation of such a sensor.

[0038] A proximity sensor 100 includes a light emitter 110 (TX) and a light detector 120 (RX) located under a covering wall 130, for example a hood (CAP), which may correspond to a top wall of a housing containing the emitter and the detector.

[0039] The emitter 110 may include a light-emitting diode (LED) or a vertical cavity surface emitting laser (VCSEL).

[0040] The detector 120 shown comprises two photodiodes, a first photodiode 121 (PDn, NEAR) and a second photodiode 122 (PDF, FAR). The two photodiodes 121, 122 are positioned such that the first photodiode 121 is closer to the emitter 110 than the second photodiode 122. For example, the first photodiode 121 is positioned between the emitter 110 and the second photodiode 122.

[0041] The wall 130 has two openings 131, 132, a first opening 131 at the right of the emitter 110 and a second opening 132 at the right of the detector 120, for example more particularly centered with the first photodiode 121, the second photodiode 122 being positioned substantially under an unopened portion of the wall 130.

[0042] The two photodiodes 121, 122 are arranged next to each other, and separated by a first distance dl, in a direction X substantially parallel to the plane of the wall 130.

[0043] The photodiodes are adapted to detect a light signal emitted by the emitter 110, then reflected by an object 20 (TARGET), and can be pinned photodiodes, avalanche photodiodes (APD), or single photon avalanche detector (SPAD).

[0044] The first photodiode 121 can be adapted to detect more particularly a nearby object, while the second photodiode 122 can be adapted to detect more particularly a distant object.

[0045] Furthermore, the electronic device 10 shown includes a display screen 12, with the proximity sensor 100 located beneath this display screen. The display screen may be an organic light-emitting diode (OLED) type screen. The wall 130 is positioned between the emitter / detector and the display screen 12, and the display screen 12 is positioned between the proximity sensor 100 and the object 20.

[0046] The proximity sensor 100 includes a processing unit 140 (SPU) configured to process the signals generated by the detector 120, in the example shown the DNn, DNf signals from the photodiodes 121, 122, for a proximity detection calculation. The processing unit 140 is configured to process the signals generated by the photodiodes, for example by implementing operations on these signals, and deliver a DN output signal from the proximity sensor 100.

[0047] For example, the output signal DN can have a value, for example an amplitude, a digital signal, for example a number of pulses or counts, which varies according to the distance separating the object 20 and the detector 120, and the processing device 140 can process this signal, for example count the pulses, to deduce the presence or not of an object near a proximity sensor.

[0048] According to an application illustrated in Figures 2A and 2B, the output signal DN of the proximity sensor 100 can be transmitted to the display screen 12 (DISPLAY), or to a display screen control circuit, in order to turn the display screen off (DISPLAY OFF) or on (DISPLAY ON). The display screen 12 can be a display screen of a mobile phone such as a smartphone, and include the proximity sensor 100 under the display screen 12, and the object 20 can be an organ, for example an ear, of a mobile phone user.

[0049] In the example illustrated in Figures 2A and 2B, the value of the output signal DN increases when the object approaches the proximity sensor, i.e. when the distance between the object and the proximity sensor decreases (direction of the arrow in [Fig.2A]), and the value of the output signal DN decreases when the object moves away from the proximity sensor, i.e. when the distance between the object and the proximity sensor increases (direction of the arrow in [Fig.2B]).

[0050] If the value of the output signal DN exceeds a detection threshold (DETECT) when the object approaches the proximity sensor, this can trigger the display to turn off (DISPLAY OFF), as illustrated in [Fig. 2A]. The display can remain off as long as the value of the output signal remains above a release threshold (RELEASE). The release threshold RELEASE is lower than the detection threshold DECTECT, as illustrated in [Fig. 2B], to ensure hysteresis, and for example, to accommodate different tolerances, such as electrical, optical, and / or mechanical tolerances (sensor assembly, integration behind the display). The difference between the detection threshold and the release threshold can be defined to achieve stable hysteresis-type operation.If the value of the output signal DN falls below the RELEASE unlock threshold when the object moves away from the proximity sensor, this can trigger the display to turn on (DISPLAY ON), as illustrated in [Fig.2B].

[0051] One operating mode of the proximity sensor 100 is explained.

[0052] During operation, the emitter 110 emits a light signal S through the first aperture 131 and the screen 12. The light signal can be reflected by an object 20, and the reflected light signal can be received back by the detector 120 through the screen 12 and the second aperture 132. A first light signal reflected SN can be detected by the first photodiode 121, and a second reflected light signal SF can be detected by the first photodiode 122.

[0053] In addition to the reflected light signals SN, SF, the first photodiode 121 detects a first AN signal from the ambient light (first ambient light signal), and the second photodiode 122 detects a second AF signal from the ambient light (second ambient light signal).

[0054] Furthermore, it has been observed that the presence of an LED display screen, and more generally of a screen, or wall, with low light transmittance, typically with a transmittance of less than 5% at the working wavelengths of the sensor, generates a crosstalk phenomenon, consisting of the transmission of light beams between the emitter and the detector by optical reflection on the screen.

[0055] Thus, the first photodiode 121 can detect a first crosstalk signal XtN, and the second photodiode 122 can detect a second crosstalk signal XTF.

[0056] The phenomenon of crosstalk, as well as ambient light, can have the disadvantage of degrading the performance of the proximity sensor, due to an undesirable optical component (noise) caused by light signals that are not emitted by the object, in addition to the useful optical reflection component caused by the reflection of the light signal emitted on the object.

[0057] Thus, in the example shown, the first signal DNn of the first photodiode 121 is equal to:

[0058] DNn = + An + XTN

[0059] And the second DNF signal of the second photodiode 122 is equal to:

[0060] DNF — SF +AF + XTF

[0061] The ambient light component for each photodiode can be compensated, for example in the processing device 140, by acquiring measurements with the emitter off, since only ambient light is then detected, and then measurements with the emitter on, and by performing a subtraction between the signal generated with the emitter on and the signal generated with the emitter off, for each photodiode. This can be achieved by acquiring several measurement samples in each configuration (emitter off and emitter on).

[0062] Thus, if we succeed in removing the ambient light component of the signals, what remains for the first photodiode 121 is:

[0063] DNn = Sn + XTn

[0064] And for the second photodiode 122:

[0065] DNF = SF + XTF

[0066] However, there remains the crosstalk component, which can explain why the proximity sensor 100, for example the processing device 140, can, based on the signals generated by photodiodes 121, 122, do not distinguish whether the object is at a very short distance, typically a few millimeters away, or at a long distance, typically more than a few centimeters away, as illustrated in [Fig.3].

[0067] Figure 3 shows the evolution curves of signals generated by the photodiodes of the proximity sensor 100 of Figure 1 as a function of the distance (in mm) between the proximity sensor and an object, and for two different quantities of measurement samples. The generated signals are, for example, in the form of a number of counts.

[0068] The right-hand curves 311 and 312 correspond to the signals generated by the first photodiode 121 (NEAR), while the left-hand curves 321 and 322 correspond to the signals generated by the second photodiode 122 (FAR). The upper curves 312 and 322 correspond to 30 measurement samples, and the lower curves 311 and 321 correspond to 6 measurement samples. It can be seen that the level of each signal, whether for the first photodiode 121 or the second photodiode 122, is essentially the same whether the distance is less than 2 or 3 millimeters (very short distance) or greater than 30 or 40 millimeters (long distance), and that the number of samples makes no difference to this.

[0069] In the application example described in relation to Figures 2A and 2B, it is understood that this problem can compromise the triggering of the screen switching off when the user is very close to, or even right next to, the screen and / or the switching on of the screen when the user is far from the screen.

[0070] To address this problem, one might want to eliminate or reduce the crosstalk components in the signals, for example by treating the first DNn signal generated by the first photodiode 121 and the second DNF signal generated by the second photodiode 122 differently. One solution could be to apply a ratio between the first DNn signal and the second DNF signal, or between the second DNF signal and the first DNn signal. Another solution could be to weight the first DNn signal by a coefficient α before subtracting the second DNF signal from it, or to weight the second DNF signal by the coefficient α before subtracting the first DNn signal and test several values ​​of the coefficient α to minimize, or even eliminate, the crosstalk components in the signals.

[0071] The second solution may consist of implementing, for example in the processing device 140 or in a dedicated compensation unit, a compensation algorithm which makes it possible to construct the following compensation equation:

[0072] DN = ax(SN + XTN)-(SF + XTF) = (a-0)xSN

[0073] where

[0074] XT F = ax XTn

[0075] and

[0076] SF = (J x 5V

[0077] Depending on the configuration of the photodiodes, for example in the configuration of [Fig.1], there may be more crosstalk component on the FAR photodiode than on the NEAR photodiode, so that a is greater than 1.

[0078] Depending on the configuration of the photodiodes and / or the positioning of the object, or even other parameters such as sensor assembly parameters and / or characteristics of the light emitter, there may be more reflected signal detected on the NEAR photodiode than on the FAR photodiode, so that [3 is less than 1, or conversely there may be more reflected signal detected on the FAR photodiode than on the NEAR photodiode, so that [3 is greater than 1.

[0079] By varying the coefficient a in the compensation equation, for example by applying several values ​​to the coefficient a, one can obtain an output signal DN with primarily the useful optical reflection component, that is to say, an output signal DN purged of crosstalk components, or at least with reduced crosstalk components. For example, at least four, or even at least eight, values ​​of the coefficient a are necessary.

[0080] However, these solutions require numerous calculations that necessitate the implementation of logic circuits, which have a significant surface area footprint on the electronic device and consume electrical power. Furthermore, these solutions may require a minimum distance dl between the two photodiodes to ensure different signal behavior between the two photodiodes NEAR and FAR. Indeed, the greater the difference in behavior between the two photodiodes NEAR and FAR, the better the detection. For example, the distance dl is greater than 0.5 mm, or even greater than 1 mm, for example, approximately 1.2 mm, which can further increase the size of the electronic device.

[0081] The inventors propose a proximity capture device, that is to say a device comprising a proximity sensor, which makes it possible to overcome all or part of the disadvantages described above, in particular to address the problem of discrimination between a very close object and a distant object, and preferably with a solution that is simple to implement, for example, a solution that avoids increasing the size of the proximity capture device and that consumes little electrical energy.

[0082] Embodiments of proximity capture devices will be described below. The embodiments described are not limiting, and various variations will become apparent to those skilled in the art based on the indications in this description.

[0083] Fig. 4 represents a proximity capture device 400 according to one embodiment, included in an electronic device 40 and positioned under a wall 12 (DISPLAY) of the electronic device 40.

[0084] The proximity sensing device 400 includes a proximity sensor that may be similar to the proximity sensor 100 of [Fig. 1], which comprises a light emitter 110 and a light detector 120 including a first photodiode 121 (NEAR) and a second photodiode 122 (FAR) under a covering wall 130, such as a hood (CAP). In the example shown, the photodiodes are arranged side by side, and separated by a second distance d2, in a direction X substantially parallel to the plane of the wall 130, but other configurations are possible. The wall 130 has two openings 131, 132, a first opening 131 at the right of the emitter 110 and a second opening 132 at the right of the detector 120, for example more particularly centered with the first photodiode 121, the second photodiode 122 being positioned substantially under an unopened portion of the wall 130.

[0085] Each photodiode is adapted to detect a light signal S emitted by the emitter 110, then reflected SN, SF by an object 20 (TARGET). By detecting the reflected light signal, and generally parasitic signals as described above, each photodiode is adapted to generate a signal DNn, DNf.

[0086] The proximity sensor 100 may also include, similarly to the proximity sensor of [Fig. 1], a processing unit 140 (SPU) configured to process the signals generated by the detector 120, in the example shown, the signals DNn, DNf generated by the two photodiodes 121, 122, for a proximity detection calculation. The processing unit 140 can generate an output signal DN, a function of the signals DNn, DNf.

[0087] The proximity sensor 100 can be of the time of flight (ToF) type sensor, and in this case, the processing device 140 can be configured to calculate the travel time between the emission of the light signal and its reception by the detector, the distance between the object and the proximity sensor can then be deduced on the basis of this travel time.

[0088] The proximity sensor 100 can operate in infrared (IR) or near-infrared (NIR) light. For example, the proximity sensor 100 can operate at wavelengths in a non-visible spectrum, for example wavelengths greater than 850 nm.

[0089] The wall 12 may be a wall with low light transmittance, or more generally, a wall capable of generating crosstalk at the operating wavelengths of the proximity sensor 100, by reflecting light signals emitted by the light emitter 110 and transmitted to the light detector 120 back onto the screen. The wall 12 may be a display screen, for example, an OLED display screen, a screen bezel (which is a non-displayed area in the border region of a display screen), or a dark protective glass. cover glass" in English).

[0090] The proximity capture device 400 further includes a control circuit 410 (SM), for example implemented by a state machine, or by a processor (CPU, "central processing unit").

[0091] The control circuit 410 is adapted to receive a signal from detector 120.

[0092] The control circuit 410 can be connected to the detector 120 via the processing device 140, which can pre-process the DNn, DNf signals acquired by the two photodiodes, so that the control circuit 410 is suitable to recover the DN output signal.

[0093] The output signal DN is preferably obtained by weighting one of the first and second signals by the weighting coefficient a, for example by weighting the first signal DNn of the first photodiode 121 by the coefficient a before subtracting the second signal DNF of the second photodiode 122 from it, or by weighting the second signal DNF by the weighting coefficient a before subtracting the first signal DNn from it.

[0094] The control circuit may be of the coprocessor type.

[0095] The control circuit 410 has been shown as not being part of the sensor proximity sensor 100, but as part of the proximity capture device 400 and connected to the proximity sensor 100. This is not limiting, and other configurations are possible. In one variant, the control circuit 410 can be included within the proximity sensor 100, for example, in the processing device 140. In another variant, the control circuit 410 can retrieve data from the proximity sensor 100 without necessarily being connected to that sensor, and the retrieved data can be post-processed within the control circuit 410.

[0096] Note that the processing device 140 can be omitted in the proximity sensor of [Fig.3], and the signals generated by the two photodiodes can be directed directly to the control circuit 410 without having been pre-processed.

[0097] The control circuit 410 is adapted to: - to move from a first state, in which the weighting coefficient has a first value al, to a second state when the output signal DN crosses a first threshold; - in the second state, apply to the weighting coefficient a second value a2 different from the first value al; and - compare the output signal DN obtained by applying the second value a2 with a second threshold.

[0098] For example, in the second state, the control circuit 410 sends a control signal Sa to the processing device 140 to modify the coefficient a, so as to modify the output signal DN.

[0099] For example, if the output signal DN is less than the second threshold, then the circuit The control circuit moves from the second state to a third state, and if the output signal DN is greater than or equal to the second threshold, then the control circuit moves from the second state to a fourth state.

[0100] The control circuit 410 provides a status signal ST which is a function of the result of the comparison between the output signal and the second threshold, for example depending on whether the control circuit 410 is in the third state or the fourth state.

[0101] The status signal ST can be an analog or digital signal, a value in a readable status register, or both. The status signal ST can also be a variable in a program that executes the state machine.

[0102] The ST status signal may comprise a first STN value corresponding to an object at a first distance from the proximity sensor, and a second STF value corresponding to an object at a second distance from the proximity sensor, the second distance being greater than the first distance. The first distance may be a very short distance (object very close), typically a few millimeters, for example less than 2 or 3 millimeters. The second distance may be a long distance (object far away), typically more than a few centimeters, for example more than 20, 30 millimeters, or even more than 40 millimeters.

[0103] The status signal ST can be transmitted to the display screen 12, or a display screen control circuit, for example in order to control its switching off, or keeping it in the off mode, if the status signal ST takes the first value STN, or its switching on, or keeping it in the on mode, if the status signal ST takes the second value STF.

[0104] Figure 5A shows an example of an embodiment of the control circuit 410 of the proximity sensor 400 of Figure 4. The control circuit of Figure 5A is implemented by a state machine. Figure 5B illustrates an example of the operation of the control circuit 410 of Figure 5A.

[0105] The example in Figures 5A and 5B is described in relation to the application in Figures 2A and 2B, and may have several applications related to proximity detection under a screen or wall with low transmittance, for example in products such as smartphones, computers, tablets, earphones, virtual reality headsets...

[0106] The represented state machine comprises four states and transitions between states: - an SI state (fourth state), in which the weighting coefficient has a first value al, and the screen is on (SYNC); - a transition from the SI state to an S2 state (first state) if the output signal (PSDATA) crosses above the detection threshold (DETECT), - in state S2, the screen is off (ASYNC); - a transition from state S2 to state S3 (second state) if the output signal PSD AT A falls below the release threshold (RELEASE); - in state S3, the weighting coefficient takes a second value a2 different from the first value; - a transition from state S3 to state S4 (third state) if the PSD ATA output signal is below a threshold (TH1) (second threshold), and the screen is still off (ASYNC); - a transition from state S4 to state S2 if the PSD ATA output signal goes back above the TH1 threshold; - a transition from state S3 to state SI (fourth state) if the PSDATA output signal is above the TH1 threshold, and the screen is turned back on (SYNC).

[0107] A four-state state machine has been represented, but the state machine could include more than four states.

[0108] When the screen is on, the proximity sensor can synchronize with the screen's clock, for example, to match the times the light emitter sends the light signal with the screen's activity. This is why it can be called synchronous mode (SYNC). When the screen is off, the proximity sensor can no longer synchronize with the screen's clock. This is why it can be called asynchronous mode (ASYNC).

[0109] By way of non-limiting example, the first value al is equal to 1 and the second value a2 is equal to 0.75, but other values ​​may be suitable.

[0110] In [Fig. 5B], the states, transitions, and thresholds are shown in relation to curves representing the evolution of the proximity sensor's output signal as a function of the distance between the object and the proximity sensor (in millimeters). The first curve 510 corresponds to the evolution of the PSDATA output signal when the weighting coefficient has the first value al and the screen is on (first configuration). The second curve 520 corresponds to the evolution of the PSDATA output signal when the weighting coefficient has the first value al and the screen is off: in this second configuration, the number of measurement samples can be higher than in the first configuration, for example, to increase the signal-to-noise ratio, which explains why the RELEASE threshold is above the DETECT threshold in the example shown.The third curve 530 corresponds to an evolution of the PSDATA output signal when the weighting coefficient has the second value a2 and the screen is off (third configuration).

[0111] In state S1, the output signal of the proximity sensor follows the first curve 510. It can be seen that when the distance decreases, in the example when the distance falls below approximately 18 mm (point 511), then the PSDATA output signal exceeds the DETECT detection threshold. The screen then turns off, and the system transitions to state S2.

[0112] In state S2, the output signal of the proximity sensor follows the second curve 520, while the screen is off. Starting from state S2, we see that we can fall below the RELEASE unlock threshold either when the distance decreases (point 521) or when the distance increases (point 522). We have then moved into state S3 and are still following the second curve 520. In other words, the screen could turn back on as desired when the distance between the object and the sensor increases, but it could also turn back on when the distance between the object and the sensor decreases further, which is undesirable. Thus, in state S2 or in state S3 following the second curve 520, the output signal of the proximity sensor does not allow us to know whether the object is moving away from the sensor or moving towards it.

[0113] Therefore, in state S3, the weighting coefficient takes a second value a2 different from the first value, so that the PSD AT A output signal is modified. This second value a2 is preferably chosen to make the output signal asymmetrical between short and long distances, and to allow determination of whether the object is at a short or long distance from the sensor. The PSD ATA output signal then follows the third curve 530. In the example shown, if the PSDATA output signal is below the threshold TH1 (below point 531), then the system enters state S4, and the screen can remain off; and if the PSDATA output signal is above the threshold TH1, then the system enters state SI, and the screen can be turned back on. In the example shown, the threshold TH1 is between the DETECT and RELEASE thresholds, but this is not a limiting factor.Alternatively, we could switch to state SI if the PSDATA output signal was below the TH1 threshold, and to state S4 if the PSDATA output signal was above the TH1 threshold.

[0114] This example demonstrates that the embodiments address the problem of discriminating between a very close object and a distant object with a simple implementation solution, for example, a state machine with four states, three thresholds (two would suffice if starting from state S2), and two values ​​of a weighting coefficient, preferably involving the displacement of the object or the proximity sensor. Such a solution can address the constraints of limiting the size of a proximity capture device and limiting electrical energy consumption.

[0115] Fig. 6 represents a curve of evolution of the output signal of the proximity sensor 100 of Fig. 4, and the different states of the control circuit 410 of Fig. 5A as a function of the distance between the proximity sensor and an object.

[0116] Curve 610 in the upper part of [Fig. 6] represents the distance between the object and the proximity sensor (Distance). Curve 620 in the middle part of [Fig. 6] represents the evolution curve of the output signal (PSDATA) of the proximity sensor 100. Lines 630 in the lower part of [Fig. 6] represent the different states of the control circuit 410. These lines correspond to several values ​​of each state S1-S4, which explains the line shape and not a single point.

[0117] Figure 6 shows that when the PSDATA output signal is below the DETECT detection threshold, the control circuit is in the fourth state S1. When the PSDATA output signal rises above the DETECT detection threshold, the control circuit moves to the first state S2. In the example shown, the PSDATA output signal also rises above the RELEASE release threshold. Then, when the PSDATA output signal falls below the RELEASE release threshold, the control circuit moves to the second state S3, in which the weighting coefficient changes from the first value a1 to the second value a2. The control circuit then compares the generated output signal with the TH1 threshold. If the PSDATA output signal is below the TH1 threshold, the control circuit moves from the second state S3 to the third state S4.Although not shown, starting from S3, if the PSDATA output signal goes above the TH1 threshold, then the control circuit goes into the fourth state SL. If, starting from S4, the PSDATA output signal goes back above the TH1 threshold, then the control circuit goes into the first state S2.

[0118] The embodiments allow the second distance d2 between the photodiodes of [Fig.4] to be reduced compared to the first distance dl between the photodiodes of [Fig.l], for example the distance d2 can be less than 500 pm, for example equal to about 250 pm.

[0119] 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.

[0120] 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

Demands

1. Proximity capture device (400) comprising: - a proximity sensor (100) comprising a light emitter (110) and a light detector (120) having at least one first photodiode (121) adapted to generate a first signal (DNn) when it detects a first light signal (SN) emitted by the light emitter and reflected by an object (20), and a second photodiode (122) adapted to generate a second signal (DNF) when it detects a second light signal (SF) emitted by the light emitter and reflected by the object; the proximity sensor being adapted to deliver an output signal (DN) as a function of the first and second signals, by weighting one of the first and second signals by a weighting coefficient (a); and - a control circuit (410) adapted to receive the output signal (DN) and to: - to move from a first state (S2), in which the weighting coefficient has a first value (al), to a second state (S3) when the output signal crosses a first threshold (RELEASE); - in the second state (S3), apply to the weighting coefficient a second value (a2) different from the first value; and - compare the output signal obtained by applying the second value (a2) with a second threshold (TH1) so as to move from the second state to a third state (S4) if the output signal is less than the second threshold, or to move from the second state to a fourth state (SI) if the output signal is greater than the second threshold.

2. Method for processing an output signal (DN) delivered by a proximity sensor (100) comprising a light emitter (110) and a light detector (120) having at least a first photodiode (121) adapted to generate a first signal (DNn) when it detects a first light signal (SN) emitted by the light emitter and reflected by an object (20), and a second photodiode (122) adapted to generate a second signal (DNF) when it detects a second light signal (SF) emitted by the light emitter and reflected by the object; the output signal (DN) being determined as a function of the first and second signals, by weighting one of the first and second signals by a weighting coefficient (a); the process comprising the transmission of the output signal (DN) to a control circuit (410) which: - goes from a first state (S2), in which the weighting coefficient has a first value (al), to a second state (S3) when the output signal crosses a first threshold (RELEASE); - in the second state (S3), applies to the weighting coefficient a second value (a2) different from the first value; and - compares the output signal obtained by applying the second value (a2) with a second threshold (TH1) so as to go from the second state to a third state (S4) if the output signal is less than the second threshold, or to go from the second state to a fourth state (SI) if the output signal is greater than the second threshold.

3. Device according to claim 1, wherein the third state (S4) corresponds to a first distance between the object (20) and the proximity sensor (100), and the fourth state (SI) corresponds to a second distance between the object and the proximity sensor, the second distance being greater than the first distance.

4. Device according to claim 1 or 3, wherein the output signal (DN) is obtained by subtracting the other of the first and second signals from the signal weighted by the weighting coefficient (a).

5. Device according to any one of claims 1, 3, 4, wherein the output signal (DN) is pre-processed by a processing device (140) of the proximity sensor (100), the processing device being connected to the control circuit (410).

6. Device according to any one of claims 1, 3 to 5, wherein the light emitter (110) and the light detector (120) are positioned under a cover wall (130) of the proximity sensor (100).

7. Device according to claim 6, wherein the first and second photodiodes are arranged next to each other, and spaced apart by a distance (d2), in a direction (X) substantially parallel to the plane of the cover wall (130).

8. Device according to claim 6 or 7, wherein the cover wall (130) has a first opening (131) at the light emitter (110), and a second opening (132) at the light detector (120), for example the second opening is centered with the first photodiode (121), the second photodiode (122) being positioned substantially under an unopened portion of the cover wall.

9. Device according to any one of claims 1, 3 to 8, wherein the first photodiode (121) is positioned between the emitter (110) and the second photodiode (122).

10. Device according to any one of claims 1, 3 to 9, wherein the proximity sensor (100) is under a wall (12) capable of generating a crosstalk phenomenon by reflection on said wall of light signals emitted by the light emitter (110) and then transmitted to the light detector (120), for example the wall has a light transmission coefficient of less than 5% at the working wavelengths of the proximity sensor (100).

11. Device according to any one of claims 1, 3 to 10, wherein the control circuit (410) is adapted to generate a status signal (ST), the status signal comprising a first value (STN) in the third state (S4) and a second value (STF) in the fourth state (SI).

12. Device according to claim 11 in combination with claim 10, wherein the wall is a display screen, for example an OLED type display screen, and the status signal (ST) is adapted to be transmitted to the display screen (12), or a control circuit of said display screen, so as to control its switching off or switching on, depending on whether the status signal takes the first value or the second value.

13. A method according to claim 2, wherein the control circuit (410) generates a status signal (ST), the status signal comprising a first value (STN) in the third state (S4) and a second value (STF) in the fourth state (SI).

14. A method according to claim 13, wherein the proximity sensor (100) is under a wall (12) capable of generating a crosstalk phenomenon by reflection on said wall of light signals emitted by the light emitter (110) and then transmitted to the light detector (120), for example the wall has a light transmission coefficient of less than 5% at the working wavelengths of the proximity sensor (100), the wall is a display screen, for example an OLED display screen, and the status signal (ST) is transmitted to the display screen (12), or a control circuit of said display screen, so as to control its switching off, or its switching on, depending on whether the status signal takes the first value or the second value.

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