Proximity capture device

Abstract

Proximity capture device The present description relates to a proximity capture device (400) comprising:- a proximity sensor (100) comprising a light emitter (110) and a light detector (120) comprising 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) depending on 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: - pass 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 pass from the second state to a third state (S4) if the output signal is lower than the second threshold, or to pass from the second state to a fourth state (S1) if the output signal is higher than the second threshold. Figure for the abstract: Fig. 4;

Description

Title of the invention: Proximity capture device Technical field

[0001] The present description relates generally to electronic devices, more particularly to electronic devices comprising a proximity sensor, for example a proximity sensor arranged 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 light beam, for example an infrared beam, which is reflected by an object and captured in return by the detector. The detector may comprise a photodiode, or several photodiodes. The proximity sensor may be connected to, or comprise, a processing unit, configured to process a signal coming from the detector, for a proximity detection calculation. For example, the signal may have a value, for example an amplitude or a number of pulses, which varies according to the distance separating the object and the detector, and the processing unit can process this signal to deduce therefrom the presence or absence of an object in the vicinity of a proximity sensor.

[0003] The proximity sensor may be of the time of flight (ToF) sensor type, and in this case, the processing unit may 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 then being able to be deduced on the basis of this travel time.

[0004] Electronic devices are known comprising a proximity sensor arranged under a screen, for example a display screen. The display screen may be an organic light-emitting diode (OLED) type screen. A proximity sensor under the display screen of a smartphone may be used to detect the presence of a user against the screen, for example when the user presses an ear to the screen to make a phone call, which may cause the screen to turn off. The proximity sensor may be used to 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 type display screen, the proximity sensor could fail to distinguish whether the object is at a very short distance (very close object), typically a few millimeters, for example less than 2 or 3 millimeters, or at a long distance (distant object), typically more than a few centimeters, for example more than 20, 30 or even 40 millimeters, from said sensor. the user and smartphone example described above, this could compromise the display screen turning off when the user is very close to the screen and / or the screen turning back on when the user moves away from the screen. Summary of the invention

[0006] There is a need for an electronic device, comprising at least one 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 very short or long distance.

[0007] Also sought is a proximity capture device, i.e. a device comprising a proximity sensor, capable of determining whether an object is at 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 comprising 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, by weighting one of the first and second signals by a weighting coefficient; and - a control circuit adapted to receive the output signal and to: - moving 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 - comparing 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 lower than the second threshold, or to move from the second state to a fourth state if the output signal is higher than the second threshold.

[0010] One embodiment provides a method for processing an output signal delivered by a proximity sensor comprising a light emitter and a light detector comprising 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 method comprising transmitting the output signal to a control circuit which: - passes 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, applies 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 lower than the second threshold, or to move from the second state to a fourth state if the output signal is higher 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 signal weighted by the weighting coefficient, the other of the first and second signals is not weighted by the weighting coefficient and is subtracted from the signal weighted by the weighting coefficient.

[0013] According to one embodiment, the output signal is preprocessed by a processing device of the proximity sensor, 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 covering wall comprises a first opening in line with the light emitter, and a second opening in line with the light detector, for example the second opening is centered with the first photodiode, the second photodiode being positioned substantially under a non-open portion of the covering 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 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 state signal, the state 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 switching off, or its switching on, depending on whether the status signal takes the first value or the second value.

[0021] According to one embodiment, the control circuit generates a state signal, the state 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 for 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 characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:

[0024] [Fig.l] 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 off or on a display screen;

[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 embodiment of the control circuit of the proximity capture device of [Fig.4];

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

[0030] [Fig.6] represents a curve of the evolution 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 embodiments

[0031] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

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

[0033] Unless otherwise specified, when referring to two elements connected to each other, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or be connected by means of 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", "upper", "lower", 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 position of use.

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

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

[0037] [Fig.l] 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 comprises a light emitter 110 (TX) and a light detector 120 (RX) located under a covering wall 130, for example a cover (CAP), which may correspond to an upper wall of a housing containing the emitter and the detector.

[0039] The emitter 110 may comprise 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 comprises two openings 131, 132, a first opening 131 in line with the emitter 110 and a second opening 132 in line with the detector 120, for example more particularly centered with the first photodiode 121, the second photodiode 122 being positioned substantially under a non-open portion of the wall 130.

[0042] The two photodiodes 121, 122 are arranged next to each other, and spaced apart 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 photodiodes (SPAD).

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

[0045] Furthermore, the electronic device 10 shown comprises a display screen 12, the proximity sensor 100 being arranged under 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 comprises a processing device 140 (SPU) configured to process the signals generated by the detector 120, in the example shown the signals DNn, DNf of the photodiodes 121, 122, for a proximity detection calculation. The processing device 140 is configured to process the signals generated by the photodiodes, for example by implementing operations on these signals, and deliver an output signal DN from the proximity sensor 100.

[0047] For example, the output signal DN may have a value, for example an amplitude, a digital signal, for example a number of pulses or counts, which varies as a function of the distance separating the object 20 and the detector 120, and the processing device 140 may process this signal, for example count the pulses, to deduce therefrom the presence or absence 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 control circuit of the display screen, in order to turn off (DISPLAY OFF) or turn on (DISPLAY ON) the display screen. 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 user of the mobile phone.

[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 goes above a detection threshold (DETECT) when the object approaches the proximity sensor, this can trigger the extinction of the screen (DISPLAY OFF), as illustrated in [Fig.2A]. The screen 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 guarantee hysteresis, and for example to support different tolerances, such as electrical, optical and / or mechanical tolerances (assembly of the sensor, integration behind the screen). The gap between the detection threshold and the release threshold can be defined to obtain a stable hysteresis type operation.If the value of the DN output signal falls below the RELEASE threshold when the object moves away from the proximity sensor, this can trigger the display to turn on (DISPLAY ON), as shown in [Fig.2B].

[0051] A mode of operation of the proximity sensor 100 is explained.

[0052] In operation, the transmitter 110 emits a light signal S through the first opening 131 and the screen 12. The light signal can be reflected by an object 20 and the reflected light signal can be captured in return by the detector 120 through the screen 12 and the second opening 132. A first light signal reflected light signal 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 signal AN from the ambient light (first ambient light signal), and the second photodiode 122 detects a second signal AF from the ambient light (second ambient light signal).

[0054] Furthermore, it has been found that the presence of an LED type display screen, and more generally of a screen, or a wall, with low light transmittance, typically with a transmittance of less than 5% at the working wavelengths of the sensor, generated 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 crosstalk phenomenon, 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 which are not emitted by the object, in addition to the useful optical reflection component caused by the reflection of the emitted light signal 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, because then only the ambient light is detected, 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 performing the acquisition of several measurement samples in each configuration (emitter off and emitter on).

[0062] Thus, if we manage to remove the ambient light component from the signals, there remains for the first photodiode 121:

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

[0067] [Fig. 3] represents curves of the evolution of signals generated by the photodiodes of the proximity sensor 100 of [Fig. 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 signals generated are, for example, in the form of number of counts.

[0068] The right curves 311, 312 correspond to the signals generated by the first photodiode 121 (NEAR), while the left curves 321, 322 correspond to the signals generated by the second photodiode 122 (FAR). The upper curves 312, 322 correspond to 30 measurement samples, and the lower curves 311, 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 substantially 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 does not change anything.

[0069] In the application example described in relation to FIGS. 2A and 2B, it is understood that this problem can compromise the triggering of the turning off of the screen while the user is very close to, or even stuck to, the screen and / or the turning back on of the screen while the user is far from the screen.

[0070] In order to address this problem, it may be desired to eliminate or reduce the crosstalk components in the signals, for example by processing differently the first DNn signal generated by the first photodiode 121 and the second DNF signal generated by the second photodiode 122. One solution may 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 may be to weight the first DNn signal by a coefficient a before subtracting the second DNF signal from it, or to weight the second DNF signal by the coefficient a before subtracting the first DNn signal from it and to test several values ​​of the coefficient a to minimize the crosstalk components in the signals, or even eliminate them.

[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.l], 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 the characteristics of the light emitter, there may be more reflected signal detected on the NEAR photodiode than on the FAR photodiode, such that [3 is less than 1, or conversely there may be more reflected signal detected on the FAR photodiode than on the NEAR photodiode, such that [3 is greater than 1.

[0079] By playing on the coefficient a in the compensation equation, for example by applying several values ​​to the coefficient a, it is possible to obtain a DN output signal with mainly the useful optical reflection component, i.e. a DN output signal expurgated of the 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 performing numerous calculations which require implementing logic circuits, which have a non-negligible surface footprint on the electronic device, and which consume electrical energy. In addition, these solutions may require having a minimum distance dl between the two photodiodes in order to guarantee different behavior of the signals between the two NEAR and FAR photodiodes. Indeed, the greater the difference in the behavior of the two NEAR and FAR photodiodes, the better the detection. For example, the distance dl is greater than 0.5 mm, or even greater than 1 mm, for example equal to approximately 1.2 mm, which may have the consequence of further increasing 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 drawbacks described above, in particular to respond to the problem of discrimination between a very close object or a distant object, and this, preferably with a solution which is simple to implement, for example, a solution which makes it possible to avoid increasing the size of the proximity capture device and which consumes little electrical energy.

[0082] Embodiments of proximity capture devices will be described below. The embodiments described are non-limiting and various variations will become apparent to those skilled in the art from the indications of the present 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 capture device 400 includes a proximity sensor that may be similar to the proximity sensor 100 of [Fig.l], 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 next to each other, and spaced apart 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 comprises two openings 131, 132, a first opening 131 in line with the emitter 110 and a second opening 132 in line with the detector 120, for example more particularly centered with the first photodiode 121, the second photodiode 122 being positioned substantially under a non-open 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 comprise, similarly to the proximity sensor of [Fig.l], a processing device 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 device 140 may generate an output signal DN, a function of the signals DNn, DNf.

[0087] The proximity sensor 100 may be of the time of flight (ToF) sensor type, and in this case, the processing device 140 may 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 then being able to be deduced on the basis of this travel time.

[0088] The proximity sensor 100 may operate with infrared (IR) or near infrared (NIR) light. For example, the proximity sensor 100 may 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, more broadly a wall capable of generating a crosstalk phenomenon at the working wavelengths of the proximity sensor 100, by reflection on said screen of the light signals emitted by the light emitter 110 and transmitted to the light detector 120. The wall 12 may be a display screen, for example an OLED type display screen, a screen outline ("bezel" in English) which is an area without display in a border region of a display screen, or a dark protective glass ("dark cover glass" in English).

[0090] The proximity capture device 400 further comprises 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 the detector 120.

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

[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 from it the second signal DNF of the second photodiode 122, or by weighting the second signal DNF by the weighting coefficient a before subtracting from it the first signal DNn.

[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 being connected to the proximity sensor 100. This is not limiting and other configurations are possible. According to one variant, the control circuit 410 may be included in the proximity sensor 100, for example in the processing device 140. According to another variant, the control circuit 410 may retrieve the data from the proximity sensor 100 without necessarily being connected to this sensor, and the retrieved data may be post-processed in 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 preprocessed.

[0097] The control circuit 410 is adapted to: - moving 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 to the processing device 140 a control signal Sa 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 control circuit switches 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 switches from the second state to a fourth state.

[0100] The control circuit 410 provides a state 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 may be an analog or digital signal, a value in a readable status register, or both. The status signal ST may also be a variable in a program that executes the state machine.

[0102] The status signal ST may comprise a first value STN corresponding to an object at a first distance from the proximity sensor, and a second value STF 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 (very close object), typically a few millimeters, for example less than 2 or 3 millimeters. The second distance may be a long distance (far object), 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 control circuit of the display screen, for example in order to control its switching off, or its maintenance in off mode, if the status signal ST takes the first value STN, or its switching on, or its maintenance in on mode, if the status signal ST takes the second value STF.

[0104] [Fig.5A] represents an exemplary embodiment of the control circuit 410 of the proximity capture device 400 of [Fig.4]. The control circuit of [Fig.5A] is implemented by a state machine. [Fig.5B] illustrates an exemplary operation of the control circuit 410 of [Fig.5A].

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

[0106] The state machine represented comprises four states and transitions between the states: - a state SI (fourth state), in which the weighting coefficient has a first value al, and the screen is on (SYNC); - a transition from state SI to state S2 (first state) if the output signal (PSDATA) passes 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 returns above the threshold TH1; - 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 comprise more than four states.

[0108] When the screen is on, the proximity sensor can synchronize with a screen clock, for example to adapt the times when the light emitter emits the light signal with the activity of the screen. This is why we can speak of synchronous mode (SYNC). When the screen is off, the proximity sensor can no longer synchronize with the screen clock. This is why we can speak of asynchronous mode (ASYNC).

[0109] As a 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 represented in relation to curves of evolution of the output signal of the proximity sensor as a function of the distance between the object and the proximity sensor (in millimeters). The first curve 510 corresponds to an 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 an 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 SI, 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 output signal PSDATA exceeds the detection threshold DETECT. The screen then turns off, and we move 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 go below the RELEASE unlocking threshold either when the distance decreases (point 521), or when the distance increases (point 522). We have then moved into state S3 and we are still following the second curve 520. In other words, the screen could turn back on as desired while the distance between the object and the sensor increases, but it could also turn back on while the distance between the object and the sensor decreases further, which is not desired. 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 if it is getting closer to it.

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

[0114] We therefore see with this exemplary embodiment that the embodiments make it possible to respond to the problem of discrimination between a very close object or a distant object, with a simple solution to implement, for example a state machine with four states, three thresholds (two could be sufficient if we start from state S2), and two values ​​of a weighting coefficient, and preferably with a displacement of the object or the proximity sensor. Such a solution can make it possible to respond to a constraint of limiting the size of a proximity capture device, and of limiting the consumption of electrical energy.

[0115] [Fig.6] represents a curve of the 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 intermediate 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 (state) of the control circuit 410. These lines correspond to several values ​​of each state S1-S4, which explains the line shape and not the single point shape.

[0117] [Fig.6] shows that when the output signal PSDATA is below the detection threshold DETECT, the control circuit is in the fourth state S1, then when the output signal PSDATA passes above the detection threshold DETECT, the control circuit goes into the first state S2. In the example shown, the output signal PSDATA also passes above the unlocking threshold RELEASE. Then, when the output signal PSDATA passes below the unlocking threshold RELEASE, the control circuit goes into the second state S3, in which the weighting coefficient goes from the first value a1 to the second value a2. The control circuit then compares the generated output signal with the threshold TH1. If the output signal PSDATA is below the threshold TH1, then the control circuit goes from the second state S3 to the third state S4.Although not shown, starting from S3, if the output signal PSDATA goes above the threshold TH1, then the control circuit goes into the fourth state SL If, starting from S4, the output signal PSDATA goes back above the threshold TH1, 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 approximately 250 pm.

[0119] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art.

[0120] Finally, the practical implementation of the embodiments and variants described is within the reach of those skilled in the art from the functional indications given above.

Claims

Claims

1. A proximity capture device (400) comprising: - a proximity sensor (100) comprising a light emitter (110) and a light detector (120) comprising 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 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: - moving 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 - comparing 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 lower than the second threshold, or to move from the second state to a fourth state (SI) if the output signal is higher 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) comprising 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 method comprising transmitting the output signal (DN) to a control circuit (410) which: - passes 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 pass from the second state to a third state (S4) if the output signal is lower than the second threshold, or to pass from the second state to a fourth state (SI) if the output signal is higher 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. A 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 preprocessed by a processing device (140) of the proximity sensor (100), the processing device being connected to the control circuit (410).

6. A 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 covering wall (130) of the proximity sensor (100).

7. Device according to claim 6, in which 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 covering wall (130).

8. Device according to claim 6 or 7, in which the covering wall (130) comprises a first opening (131) at the level of the light emitter (110), and a second opening (132) at the level of 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 covering wall.

9. A 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, in which 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) 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 state signal (ST), the state 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 on, depending on whether the status signal takes the first value or the second value.

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

14. Method according to claim 13, in which 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) 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 type 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 extinction, or its ignition, depending on whether the status signal takes the first value or the second value.

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