Optoelectronic sensor

Abstract

Examples disclose an optoelectronic sensor configured to detect the presence of an object in a predetermined region via reflection of at least one light beam, the sensor comprising: - a subtracting stage configured to generate an output voltage by subtracting a second voltage generated using a second photodiode from a first voltage generated using a first photodiode following emission of at least one beam; - a summing stage configured to generate an output voltage by adding the first voltage to the second voltage; the optoelectronic sensor is configured: - so that a difference between a first luminous flux received by the first photodiode and a second flux received by the second photodiode is positive when a beam is reflected when the object is in the predetermined region; and - to detect the object based on the output voltages of the subtracting stage and summing stage.

Description

Description Title: Optoelectronic sensor Technical field

[0001] The present disclosure relates to the field of optoelectronic sensors configured to detect the presence of an object in a predetermined detection zone by reflecting a light beam on this object. Prior art

[0002] Optoelectronic sensors are now used to detect the presence of an object in a predetermined detection zone.

[0003] These sensors emit a light beam into the predetermined detection area and monitor the electrical output signal of a photodiode in response to the emission of the light beam. In this case, the electrical output signal of the photodiode is proportional to the light flux received by the photodiode. This electrical output signal is different when the object is or is not in the predetermined detection area since the object will reflect the light beam emitted by the sensor. Therefore, monitoring the electrical output signal of the photodiode can detect the presence or absence of the object in the predetermined detection area.

[0004] However, the electrical output signal of the photodiode is generally very weak, so that this output signal is relatively sensitive to noise. In particular, the luminous flux surrounding the sensor and the intrinsic reflective nature of the object to be detected, which depends partly on its color, can sometimes alter the operation of the sensor.

[0005] This disclosure improves this situation. Summary

[0006] In this regard, an optoelectronic sensor is provided that is configured to detect the presence of an object in a predetermined detection zone by reflection of at least one light beam on said object, the optoelectronic sensor comprising: - a light source adapted to emit the at least one light beam according to a predetermined orientation; - a first photodiode configured to generate a first electric current as a function of a first light flux on the first photodiode; - a second photodiode configured to generate a second electric current as a function of a second light flux on the second photodiode; - a converter stage configured to convert the first and second electrical currents into first and second electrical voltages; - a subtractor stage configured to generate an output voltage by subtracting the second electrical voltage from the first electrical voltage; - a summing stage configured to generate an output voltage by adding the first electrical voltage to the second electrical voltage; wherein the optoelectronic sensor is configured: - such that a difference between the first luminous flux received by the first photodiode and the second luminous flux received by the second photodiode is positive when a light beam is reflected by an object positioned in the predetermined detection zone; and - to detect an object from the output voltages of the subtractor stage and the summing stage.

[0007] Optionally, the optoelectronic sensor further comprises a signal amplifier stage capable of amplifying the first and second electrical currents or capable of amplifying the first and second electrical voltages.

[0008] Optionally, the converter stage is also an amplifier stage and comprises a first transimpedance amplifier capable of amplifying and converting the first electric current into a first electric voltage and a second transimpedance amplifier capable of amplifying and converting the second electric current into a second electric voltage.

[0009] Optionally, the optoelectronic sensor further comprises an ambient light compensation stage configured to reduce the share of ambient light-induced current in the current generated by the photodiodes.

[0010] Optionally, the subtractor stage and the summing stage also include an amplifier amplifying their respective output voltage.

[0011] Optionally, the optoelectronic sensor further comprises a filtering stage configured to filter the first and second electrical voltages.

[0012] Optionally, the optoelectronic sensor further comprises: - an emission lens arranged opposite the light source so as to be crossed by the light beam emitted by the light source; and - a receiving lens arranged opposite the first and second photodiodes so as to be crossed by the fluxes received by the first and second photodiodes.

[0013] In a first option, the optoelectronic sensor is configured to detect an object in the predetermined detection zone when: a) the output voltage of the subtractor stage is positive when emitting a light beam, and b) the output voltage of the summing stage is greater than a first predetermined voltage threshold when emitting the light beam.

[0014] In the first option, the first voltage threshold is a hysteresis threshold having a lower terminal and an upper terminal, the difference between the lower terminal and the upper terminal being greater than a voltage amplitude predetermined as corresponding to a voltage amplitude due to noise on the output voltage of the summing stage.

[0015] In a second option, the optoelectronic sensor further comprises a controlled inverter stage and an integrator stage, the controlled inverter stage comprising: - a first controlled inverter connected to the subtractor stage and configured to invert the output voltage of the subtractor stage during the time intervals between the emission of two consecutive light beams of the time sequence of light beams; - a second controlled inverter connected to the summing stage and configured to invert the output voltage of the summing stage during the time intervals between the emission of two consecutive light beams of the time sequence of light beams; the integrator stage comprising: - a first integrator connected to the first controlled inverter and configured to integrate the output voltage of the subtractor stage partly inverted by the first controlled inverter stage, so as to obtain a detection signal of the subtractor;and - a second integrator connected to the second controlled inverter and configured to integrate the output voltage of the summing stage partly inverted by the second controlled inverter stage, so as to obtain a detection signal from the summing stage; and; wherein the optoelectronic sensor is configured to detect an object in the predetermined detection zone when: a) the detection signal of the subtractor is positive, and b) the detection signal of the adder is greater than a second determined voltage threshold.

[0016] The application also relates to a method for detecting an object in a predetermined detection zone by reflecting at least one light beam on the object using any of the examples of optoelectronic sensors presented in the present disclosure, the method comprising: emitting the at least one light beam in a predetermined time interval using the light source; obtaining the output voltage of the subtractor stage during the predetermined time interval, the output voltage of the subtractor stage being composed of amplitudes generated by the at least one light beam; obtaining the output voltage of the summing stage during the predetermined time interval, the output voltage of the summing stage being composed of amplitudes generated by the at least one light beam of the sequence of light beams;and detecting an object in the predetermined detection area from the obtained output voltages of the subtractor stage and the summing stage.;

[0017] Optionally, the method is implemented using an optoelectronic sensor according to the second option, and the method comprises: emitting a time sequence of light beams in a predetermined time interval using the light source; obtaining the output voltage of the subtractor stage during the predetermined time interval, the output voltage of the subtractor stage being composed of amplitudes generated by the light beams of the sequence of light beams; processing the output voltage of the subtractor stage by inverting the output voltage of the subtractor stage during the time intervals between the emission of two consecutive light beams of the time sequence of light beams and then integrating the partially rectified voltage to obtain a detection signal of the subtractor, from the first controlled inverter and the first integrator;obtaining the output voltage of the summing stage during the predetermined time interval, the output voltage of the summing stage being composed of amplitudes generated by the light beams of the light beam sequence; processing the output voltage of the summing stage by inverting the output voltage of the stage; adder during the time intervals between the emission of two consecutive light beams of the time sequence of light beams and then integrating the partially rectified voltage to obtain a detection signal of the adder, from the second controlled inverter and the second integrator; and detecting the object in the predetermined detection zone when: a) the detection signal of the subtracter is positive; and b) the detection signal of the adder is greater than a second determined voltage threshold.

[0018] The examples of optoelectronic sensor and detection method presented in the present disclosure thus make it possible to guarantee stability of the detection (object detected or not detected) by ensuring a sufficient signal-to-noise ratio, whether it is the electronic noise introduced by the different electronic components of the optoelectronic sensor, or the noise introduced by the ambient light in the generation of the current by the photodiodes. In this case, the fact that the optoelectronic sensor according to the present disclosure uses the output voltage of a summing stage adding the voltages resulting from the currents generated by the first and second photodiodes in the detection of an object in the predetermined detection zone makes it possible to guarantee stability of the detection by ensuring a sufficient signal-to-noise ratio making it possible to avoid switching from one state to another (detection or not detected) due to noise.Furthermore, in the second examples of optoelectronic sensor based on the emission of a time sequence of light beams to detect an object in the predetermined area, the influence of noise in the stability of the detection is further reduced. Indeed, the noise on the voltages is filtered by the combination of the controlled inverter stage and the integrator stage and the output voltages compared to detect or not detect an object (the detection signals) have an increased amplitude level compared to the first examples, which further increases the signal-to-noise ratio, thus improving the stability of the detection. Brief description of the drawings.

[0019] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analyzing the attached drawings, in which: Fig.1

[0020] [Fig. 1] schematically represents an example of an optoelectronic sensor configured to detect the presence of an object in a predetermined detection zone by reflection of a light beam on said object. Fig.2

[0021] [Fig.2] represents a schematic diagram of the detection of an object by triangulation from an example of an optoelectronic sensor. Fig.3

[0022] [Fig.3] schematically represents another example of an optoelectronic sensor configured to detect the presence of an object in a predetermined detection zone by reflecting a sequence of light beams on said object. Fig.4

[0023] [Fig.4] represents a flowchart of an example of a method for detecting an object in a predetermined detection zone by reflecting at least one light beam on the object using an optoelectronic sensor according to the present disclosure. Fig.5a

[0024] [Fig.5a] represents a temporal evolution of the voltage signals measured at the output of different electronic stages of an optoelectronic sensor in response to the emission of a temporal sequence of light beams when an object reflecting the light beams is positioned in a predetermined detection zone. Fig.5b

[0025] [Fig.5b] represents a temporal evolution of the voltage signals measured at the output of different electronic stages of the optoelectronic sensor in response to the emission of the same temporal sequence of light beams as that used in figure 5a when the object reflecting the light beams is positioned beyond the predetermined detection zone. Description of the embodiments

[0026] An example of an optoelectronic sensor 1 configured to detect the presence of an object 10 in a predetermined detection zone by reflection of at least one light beam on said object is now described with reference to FIGS. 1 to 3. The optoelectronic sensor 1 may correspond to a background suppression sensor (known as “background suppressing sensors”) detecting the presence of an object by triangulation.

[0027] The optoelectronic sensor 1 comprises a light source 2 adapted to emit the at least one light beam according to a predetermined orientation. In examples detailed below, the light source 2 is adapted to emit a temporal sequence of light beams. The light source 2 may for example correspond to a light-emitting diode. It is the reflection of at least one light beam on the object 10 which will make it possible to determine its presence, in particular by triangulation as explained below. Consequently, the predetermined detection zone Zd is defined according to the predetermined orientation of the light beam when using the sensor 1. A light beam may for example correspond to a red light beam or an infrared light beam.

[0028] The optoelectronic sensor 1 comprises a first photodiode 3a and a second photodiode 3b. The first photodiode 3a is configured to generate a first electric current i aas a function of a first luminous flux received by the first photodiode 3a. Similarly, the second photodiode 3b is configured to generate a second electric current ib as a function of a second luminous flux received by the second photodiode 3b. Each of the photodiodes is connected to a ground of the optoelectronic sensor, as shown in FIG. 3.

[0029] The optoelectronic sensor 1 comprises a converter stage 4 configured to convert the first and second electrical currents, generated respectively by the first 3a and the second 3b photodiode, into first va and second vb electrical voltages. The converter stage 4 thus converts the first electrical current ia, generated by the first photodiode 3a from the luminous flux that it receives into a first electrical voltage va. It also converts the second electrical current ib, generated by the second photodiode 3b from the luminous flux that it receives into a second electrical voltage vb.

[0030] The optoelectronic sensor 1 comprises a subtractor stage 5. The subtractor stage 5 is configured to generate an output voltage by subtracting the second electrical voltage vb from the first electrical voltage va. The subtractor stage 5 may also comprise an amplifier for amplifying the output voltage of the subtractor stage. In examples, the subtractor stage 5 may comprise an operational amplifier.

[0031] The optoelectronic sensor 1 comprises a summing stage 6. The summing stage 6 is configured to generate an output voltage by adding the first electrical voltage v a at the second electrical voltage v b . The summing stage 6 may also include an amplifier for amplifying the output voltage of the summing stage. In examples, the summing stage 6 may include an operational amplifier.

[0032] The optoelectronic sensor 1 is configured so that a difference between the first luminous flux received by the first photodiode and the second luminous flux received by the second photodiode is positive when the light beam is reflected by an object positioned in the predetermined detection area. In this case, a position of the photodiodes 3a and 3b relative to each other is determined so that a difference between the first light flux received by the first photodiode and the second light flux received by the second photodiode is positive when the light beam is reflected by an object positioned in the predetermined detection area. The photodiodes are arranged next to each other, contiguously, as shown in Figure 2. The arrangement of the photodiodes 3, and the predetermined detection area depend directly on the application in which the optoelectronic sensor 1 is to be used. The optoelectronic sensor 1 presented can thus be used to detect an object passing at a given position opposite the sensor on a conveyor path.For example, we think of a suitcase moving on an airport conveyor belt or a part moving on a production line.

[0033] In particular, and as illustrated in Figure 2, the presence of an object in a detection zone can be detected by triangulation from an electronic sensor 1. Figure 2 represents a schematic diagram of detection of an object by triangulation from an example of optoelectronic sensor 1 according to the present disclosure. This is a side view, perpendicular to the optical axis of the light beam emitted by the light source 2, of an example of sensor 1 when the object 10 is in the predetermined detection zone Zd (top representation), and when it is outside (bottom representation). The axis d represents the distance between the sensor 1 and the object 10 to be detected, and the predetermined detection zone Zd extends between two extrema Zd1 and Zd2.The light source 2 of the sensor 10 thus emits a light beam initially passing through an emission lens 21, the beam then being reflected by the object 10, then directed towards the photodiodes 3a and 3b by a reception lens 31, an angle θ being formed between the light beam emitted by the light source 2 and the light beam reflected by the object 10. It is understood, as illustrated by FIG. 2, that the angle θ varies as a function of the distance at which the object 10 is located relative to the sensor 1, just like the luminous flux received by the photodiodes 3 which depends on this angle. In FIG. 2, it is shown schematically that when the object 10 is located in the predetermined detection zone Zd, only the first photodiode 3a receives the reflected light beam while when the object 10 is outside the predetermined detection zone Zd, only the second photodiode 3b receives the reflected luminous flux.The object 10 is therefore detected when the first photodiode 3a receives the reflected light flux. However, this is a schematic representation allowing the detection principle used to be understood. In reality, the reflected light flux is received with more or less intensity by both. photodiodes 3 as a function of the distance at which the object 10 is located from the sensor 1. It is therefore by then comparing these light fluxes, via the currents generated by the photodiodes, that the optoelectronic sensor 1 is capable of detecting whether or not the object 10 is in the predetermined detection zone Zd. In particular, the extrema Zd2 is determined as corresponding to an equivalent received light flux between the two photodiodes 3 so that when the object 10 approaches the sensor 1 along the optical axis from this extrema Zd2, the first photodiode 3a receives more reflected light flux than the second photodiode 3b, thus signifying the presence of the object 10 in the predetermined detection zone Zd.Conversely, when the object 10 moves away from the sensor 1 along the optical axis from this extrema Zd2, the first photodiode 3a receives less reflected light flux than the second photodiode 3b, signifying the absence of the object 10 in the predetermined detection zone Zd.

[0034] In the present disclosure, the optoelectronic sensor 1 is configured to detect an object in the predetermined detection zone Zd from the output voltages of the subtractor stage 5 and the summing stage 6.

[0035] In particular, in first examples, the optoelectronic sensor 1 is configured to detect an object in the predetermined detection zone Zd when: a) the output voltage of the subtractor stage 5 is positive when a light beam is emitted, and b) the output voltage of the summing stage 6 is greater than a first predetermined voltage threshold vth1 when the light beam is emitted.

[0036] These first examples are shown in Figure 1 and can make it possible to detect an object 10 in the predetermined detection zone using the emission of a single light beam emitted by the light source 2.

[0037] Thus, in these first examples, the optoelectronic sensor 1 may comprise a comparator stage 7 comprising a first comparator 7a configured to compare the output voltage of the subtractor stage 5 to a zero voltage and a second comparator 7b configured to compare the output voltage of the summing stage 6 to the first predetermined voltage threshold vth1. The optoelectronic sensor 1 may further comprise a logic gate 8 applying an AND function, receiving as input the outputs of the first 7a and the second 7b comparators, and transmitting a logic signal to a detection unit 9 triggering a detection of an object 10 in the predetermined detection zone Zd when the logic signal of the AND gate 8 that it receives is at 1.

[0038] A positive output voltage of the subtractor stage 5 (condition a) corresponds to the fact that the first current i a generated is greater than the second current i b generated what, intheory, means that the luminous flux received by the first photodiode 3a is greater than the luminous flux received by the second photodiode 3b. Since the arrangement of the photodiodes 3 is determined so that a luminous flux received by the first photodiode 3a is greater than a luminous flux received by the second photodiode 3b when the object 10 is in the predetermined detection zone Zd, an object 10 should simply be detected in the predetermined detection zone when this condition is met. This is the detection principle explained above. This detection condition makes it possible to make the detection distance of an object 10 in a detection zone Zd predetermined by the optoelectronic sensor 1 independent of the reflective nature of the object 10 in question.Indeed, the detection principle used by the optoelectronic sensor 1 presented is based on a difference in luminous flux received by the photodiodes so that even when the luminous flux is reflected by an object 10 whose reflective character is weak, for example when the object is black in color, there will still be a difference in luminous flux received between each of the photodiodes 3 depending on the position of the object 10, even if the luminous fluxes received independently by each of the photodiodes are attenuated. To this extent, the optoelectronic sensor 1 presented makes it possible to detect an object 10 at a detection distance independent of the intrinsic reflective character of the object 10 considered in this detection.

[0039] However, the inventors noticed that electronic noise introduced by the photodiodes 3 and the electronic stages of the optoelectronic sensor could induce a negative output voltage of the subtractor stage while the object to be detected was still in the predetermined detection zone, after a first detection of the object, which made the detection character of the optoelectronic sensor potentially unstable. In other words, the inventors noticed that the optoelectronic sensor could detect the presence of an object in the detection zone Zd at a time t, then detect its absence at time t+1 due to noise on the output voltage of the subtractor stage 5, making the interpretation of the object detection information relatively complicated.

[0040] Therefore, in the first examples, the optoelectronic sensor 1 is also configured to check condition b) before detecting an object 10 in the predetermined detection area. As explained above, the optoelectronic sensor 1 according to the present disclosure comprises a summing stage 6 adding the first v a and the second v b electrical voltages, and the optoelectronic sensor is further configured to compare this sum to the first predetermined voltage threshold v th1 . Comparing whether the output voltage (v a + v b ) of the summing stage 6 is greater than the first predetermined voltage threshold v th1 to detect an object in the detection zone Zd predetermined allows to guarantee good stability of the detection by ensuring a sufficient signal to noise ratio.

[0041] Furthermore, checking that the sum of the first v aand the second v b output electrical voltages are greater than a threshold (v th1 ) also makes it possible to discriminate between a situation in which the object is positioned at a distance corresponding to the extrema Zd2 of the predetermined zone Zd for which the currents generated by the photodiodes are equal; and therefore the output voltage of the subtractor stage is zero; and a situation in which there is no object at all in front of the sensor, the light beam therefore not being reflected and the currents generated by the photodiodes being zero, also inducing a zero output voltage of the subtractor stage.

[0042] To this extent, the summing stage 6 makes it possible to stabilize the detection of an object in the predetermined detection zone Zd by ensuring a sufficient signal-to-noise ratio to make a detection decision and also makes it possible to discriminate a situation in which the object is positioned at a distance from the sensor corresponding to the extrema Zd2 from a situation in which no object reflects the light beam.

[0043] In the first examples, the first predetermined voltage threshold vth1 may be determined from an average output voltage of the summing stage 5 when there is no object in the detection zone Zd and / or from an average output voltage of the summing stage 5 when there is an object beyond the detection zone Zd reflecting the light beam. In particular, the first predetermined voltage threshold vth1 may for example be determined as greater than a determined percentage of the average output voltage of the summing stage 5 when there is no object in the detection zone and / or from a percentage of the average output voltage of the summing stage 5 when there is an object beyond the detection zone Zd reflecting the light beam. In these first examples, the first predetermined voltage threshold vth1 may be determined to ensure a signal-to-noise ratio greater than a determined ratio.These alternatives make it possible to guarantee the stability of the detection of an object in the predetermined detection zone Zd by ensuring a sufficient signal-to-noise ratio on the output voltage of the adder stage 6 to comply with the detection condition b) presented above.

[0044] In examples, the first predetermined voltage threshold v th1 is a hysteresis threshold having an upper terminal and a lower terminal. In these examples, the optoelectronic sensor is configured to detect the object in the predetermined detection zone Zd when the output voltage of the subtractor stage is positive and when the output voltage of the summing stage 6 is greater than the upper terminal of the first threshold predetermined voltage v th1when emitting the light beams. In these examples, the optoelectronic sensor is also configured to interrupt the detection of the object when the output voltage of the summing stage 6 is lower than the lower terminal of the hysteresis threshold of the first predetermined voltage threshold v th1during the emission of the light beams. The lower terminal of the hysteresis threshold can for example be determined from a maximum noise voltage generated by the electronic components of the sensor on the output voltage of the summing stage 6. In particular, the lower terminal of the hysteresis threshold can be determined so that a difference between the lower terminal and the upper terminal is greater than a voltage amplitude predetermined as corresponding to a voltage amplitude due to noise on the output voltage of the summing stage. This voltage amplitude due to noise on the output voltage of the summing stage can be predetermined from tests carried out on the optoelectronic sensor.

[0045] In second examples, the optoelectronic sensor 1 considers a time sequence of light beams emitted by the light source 2 to detect whether or not an object is present in the predetermined detection zone. The light beam sequence designates the emission, by the light source 2, of a plurality of light beams at a determined frequency. The time sequence of light beams is notably represented in FIGS. 5a and 5b by the reference FL. FIG. 5a represents a time evolution of the voltage signals measured at the output of different electronic stages of an optoelectronic sensor in response to the emission of the time sequence of light beams when an object reflecting the light beams is positioned in the predetermined detection zone Zd.Figure 5b represents a temporal evolution of the same voltage signals in response to the emission of the temporal sequence of light beams when the object reflecting the light beams is positioned beyond the predetermined detection zone Zd.

[0046] In these second examples, the optoelectronic sensor 1 may comprise a controlled inverter stage 11 configured to invert the output voltage of the subtractor stage 5 and to do the same with the output voltage of the summing stage 6 during the time intervals between the emission of two consecutive light beams of the time sequence of light beams. The output voltage of the controlled inverter stage 11 acting on the output voltage (v a - v b) of the subtractor stage is represented in particular in Figures 3, 5a and 5b by the reference V-. As can be seen in Figures 5a and 5b, only the parts of the output voltage signals corresponding to the time intervals between the emission of two light beams of the sequence are inverted, the other parts of the voltage signals are not modified. In other words, the controlled inverter stage 11 applies a gain of -1 to the output voltages of the subtractor 5 and summing 6 stages during the time intervals between two consecutive light beams of the time sequence of light beams and does not modify the other parts forming these output voltages, which amounts to considering that the controlled inverter stage 11 applies a gain of 1 to these other parts.

[0047] The controlled inverter stage 11 can thus comprise a first controlled inverter 11a connected to the output voltage of the subtractor stage 5 and configured to invert the output voltage (v a - v b ) of the subtractor stage 5 during the time intervals between the emission of two consecutive light beams of the time sequence of light beams. The controlled inverter stage 11 may also comprise a second controlled inverter 11b connected to the output voltage of the summing stage 6 and configured to invert the output voltage (va + vb) of the summing stage 6 during the time intervals between the emission of two consecutive light beams of the time sequence of light beams. The output voltage of the second controlled inverter 11b is thus represented by the reference V+ in FIG. 3.

[0048] In the second examples, the optoelectronic sensor 1 may comprise an integrator stage 14 connected to the controlled inverter stage 11 and configured to integrate the output voltages V- and V+ of the controlled inverter stage 11. The integrator stage 14 may comprise a first integrator 14a connected to the first controlled inverter 11a and configured to integrate the voltage V-, corresponding to the output voltage of the subtractor stage 5 (va - vb) partly inverted by the controlled inverter stage 11, so as to obtain a first detection signal VDIFF called the “subtractor detection signal”. The integrator stage 14 may also comprise a second integrator 14b connected to the second controlled inverter 11b and configured to integrate the voltage V+, corresponding to the output voltage of the summing stage 6 (va + vb) partly inverted by the controlled inverter stage 11, so as to obtain a second detection signal VSUM called the “summator detection signal”.

[0049] The subtractor detection signal is a label to designate the output voltage of the integrator stage 14, associated with the subtractor stage 5 of the optoelectronic sensor 1 while the adder detection signal is another label designating the output voltage of the integrator stage 14, associated with the summing stage 6 of the optoelectronic sensor 1.

[0050] In these second examples, an object 10 is detected in the predetermined detection zone Zd when: a) the detection signal of the subtractor V DIFF is positive; and b) the detection signal of the summer V SUM is greater than a second voltage threshold v th2 determined.

[0051] In these second examples, the optoelectronic sensor 1 can thus comprise a comparator stage of the integrator stage 12 comprising a first comparator 12a configured to compare the output voltage of the first integrator 14a of the integrator stage 14 to a zero voltage and comprising a second comparator 12b configured to compare the output voltage of the second integrator 14b of the integrator stage 14 to the second voltage threshold v th2 predetermined. The optoelectronic sensor 1 may further comprise in these examples the logic gate 8 applying an AND function and receiving as input the outputs of the first 14a and the second 14b comparators, which is configured to transmit a logic signal to the detection unit 9 triggering a detection of an object 10 in the predetermined detection zone when the logic signal of the AND gate that it receives is at 1.

[0052] In these second examples, it is a matter of considering a time sequence of light beams to detect whether or not an object 10 is present in the predetermined detection zone. In this case, the amplitude of the noise of the signal generated by the photodiode and the amplifier stages which follow in response to a received light flux varies over time. Consequently, the amplitude of the noise of the signal generated by the photodiode and the electronic stages which follow varies for each light beam of a sequence of light beams emitted by the light source 2.To this extent, partially inverting and then integrating the voltages generated at the output of the subtractor stage 5 and / or the summing stage 6 in response to the reception of several light beams emitted by the light source 2 makes it possible to make the output voltages of the integrators less dependent on the variable noise that a single light beam could generate since the variability of the noise is averaged by considering several beams. As such, the comparison of these output voltages with a threshold is much less dependent on the electronic noise introduced by the different elements of the optoelectronic sensor 1. In particular, and this is clearly shown in Figures 5a and 5b, it is understood that a voltage difference between a voltage signal VDIFF in a situation in which the object is positioned in the predetermined detection zone Zd (Figure 5a) and a voltage signal V. DIFFin a situation in which the object is positioned beyond this zone (figure 5b) is all the greater the more light beams there are in the time sequence of light beams so that confusion of these two situations due to electronic noise is largely reduced.

[0053] Furthermore, it is no longer necessary to synchronize the threshold comparisons with the emission of a light beam as proposed in the first examples. effect, the output voltages V DIFF and V SUM of the integrator stage are continuous so that once the time sequence of light beams has been emitted, and before the release of these voltages for the emission of the next time sequence, the comparison of these voltages with their respective threshold (zero voltage for V DIFF and v th2 for V SUM ) can be performed without the need to be precise about when these voltages are compared.

[0054] In these second examples, the second voltage threshold v th2 is determined from the number of light beams emitted by the light source 2. In particular, in examples, the second voltage threshold v th2 is a hysteresis threshold having an upper limit and a lower limit. In these examples, the optoelectronic sensor is configured to detect the object in the predetermined detection zone Zd when the detection signal of the subtractor VDIFF is positive and when the detection signal of the adder VSUM is greater than the upper limit of the second voltage threshold vth2. In these examples, the optoelectronic sensor is also configured to interrupt detection of the object when the detection signal of the adder VSUM is less than the lower limit of the hysteresis threshold of the second voltage threshold vth2.

[0055] In this case, the combination of the controlled inverter stage 11 and the integrator stage 14 allowing the detection signals of the subtractor VDIFF and the adder VSUM to be obtained forms a stage for synchronous demodulation of the time sequence of light beams. Indeed, the emission of a time sequence of light beams allowing the presence of an object to be detected in the predetermined detection zone Zd can be considered as a way of modulating the information of presence or absence of the object in the predetermined detection zone Zd on the different beams of the time sequence. Consequently, the fact of recombining the information from each of these beams and translated onto the voltages by operating a controlled inversion of these voltages and their integration can be considered as a synchronous demodulation of the information of presence or absence of the object.Furthermore, the combined use of the controlled inverter stage 11 and the integrator stage 14 also acts as a filter on a continuous external signal or one having a low frequency which would disturb the first va and second vb electrical voltages generated by the reflected light beams of the sequence. Indeed, the controlled inverter stage 11, applying a positive or negative unit gain to the frequency of the sequence, therefore makes the disturbing signal alternating, so that its integration by the integrator stage 14 is zero.

[0056] The optoelectronic sensor 1 according to the present disclosure thus makes it possible to guarantee the stability of the detection while making negligible the difference in detection distance of an object by the sensor 1 when this object is not very reflective or very reflective to the luminous flux.

[0057] The various examples presented in the following paragraphs of this disclosure may be independently combined with the first or second examples described above unless expressly indicated otherwise.

[0058] In examples, the optoelectronic sensor 1 comprises an emission lens 21, as shown in FIG. 2. The emission lens 21 is arranged opposite the light source 2 so as to be traversed by the light beam emitted by the light source. It makes it possible to deflect the light rays of the light beam emitted by the light source 2 so as to make them converge at the output.

[0059] In examples, the optoelectronic sensor 1 also comprises a receiving lens 31, as shown in FIG. 2. The receiving lens 31 is arranged opposite the first 3a and second 3b photodiodes so as to be crossed by the fluxes received by the first 3a and second 3b photodiodes. The receiving lens 31 makes it possible to concentrate these light fluxes towards the photodiodes 3.

[0060] In examples, the sensor 1 comprises a signal amplifier stage capable of amplifying the first ia and second ib electrical currents or capable of amplifying the first va and second vb electrical voltages. The signal amplifier stage may for example be arranged between the photodiodes 3 and the converter stage 4, in which case it will amplify the first ia and second ib electrical currents. The signal amplifier stage may also be arranged between the converter 4 and the summing 6 and subtracting 5 stages, in which case it will amplify the first va and second vb electrical voltages. In examples in which the subtracting stage 5 and / or the summing stage 6 comprise an amplifier, there are therefore at least two signal amplifications, one applied to the currents or voltages, and one applied to amplify the output voltage of the subtracting 5 and / or summing 6 stages.

[0061] In examples, the converter stage 4 is also an amplifier stage and comprises a first transimpedance amplifier 41a capable of amplifying and converting the first electric current ia into a first electric voltage va and a second transimpedance amplifier 41b capable of amplifying and converting the second electric current ib into a second electric voltage vb. These examples make it possible, by using the same electronic element, to amplify and convert a current into a voltage, which makes it possible to reduce the cost of the sensor and simplify its design. In particular, the converter stage 4 having the first transimpedance amplifier 41a and the second transimpedance amplifier 41b can therefore correspond to the signal amplifier stage mentioned above.

[0062] In examples, the optoelectronic sensor 1 may include an ambient light compensation stage 13 configured to compensate for ambient light-induced current in the current generated by the photodiodes 3. In examples, the ambient light compensation stage 13 may include a first compensation stage 13a connected in antiparallel to the first transimpedance amplifier 41a of the converter stage and a second compensation stage 13b connected in antiparallel to the second transimpedance amplifier 41b of the converter stage 4. More specifically, the first compensation stage 13a may include a first low-pass filter 131a connected to a first amplifier 132a, the first amplifier 132a being further connected to a first voltage-to-current converter 133a, as illustrated in FIG.Similarly, the second compensation stage 13b may comprise a second low-pass filter 131b connected to a second amplifier 132b, the first amplifier 132a also being connected to a second voltage-current converter 133b.

[0063] In examples, the optoelectronic sensor 1 may comprise a filtering stage F configured to filter the first va and the second vb electrical voltages. The filtering is carried out before these voltages are subtracted by the subtractor stage 5 or summed by the summing stage 6. The filtering stage F therefore comprises two filters. The filtering stage comprises a first filter F1 for filtering the first electrical voltage va in order to obtain a filtered voltage vaF as shown in FIG. 3. The filtering stage F comprises a second filter F2 for filtering the second electrical voltage vb in order to obtain a filtered voltage vbF as shown in FIG. 3. The first and second filters are bandpass filters. These filters are substantially centered around the frequency of the sequence of the light beam in the second examples.In this way, the impact of spectral components induced by light sources other than the light source 2 of the optoelectronic sensor 1 on the first va and second vb electrical voltages is reduced. Since the detection of an object 10 in the predetermined detection zone is based on the exploitation of the first va and second vb electrical voltages, the detection is made more precise. Furthermore, the bandpass filter also makes it possible to largely filter out the noise introduced by the electronic components used in the sensor on the first electrical voltage v. a and the second electrical voltage v b, in particular the noise introduced by the photodiodes 3, the noise introduced by the converter stage 4 and the noise introduced by the amplifier stage or the ambient light compensation stage 13 where appropriate. Indeed, the noise can be considered as substantially constant over all the frequencies of the signal so that the application of a band-pass filter on the voltages makes it possible to eliminate the spectral components noise outside the frequency band considered, low compared to the set of frequencies making up the signal.

[0064] An example of a method 100 for detecting an object 10 in a predetermined detection zone by reflecting at least one light beam on the object 10 using an optoelectronic sensor 1 according to the present disclosure is now presented with reference to FIG. 4.

[0065] As illustrated by FIG. 4, the method 100 comprises an operation 110 of emitting at least one light beam in a predetermined time interval using the light source 2.

[0066] As illustrated in FIG. 4, the method 100 comprises an operation 120 of obtaining the output voltage of the subtractor stage 5 during the predetermined time interval. The output voltage of the subtractor stage 5 is thus composed of amplitudes generated by the at least one light beam emitted by the light source 2.

[0067] As illustrated in FIG. 4, the method 100 comprises an operation 130 of obtaining the output voltage of the summing stage 6 during the predetermined time interval. The output voltage of the summing stage 6 is also composed of amplitudes generated by the at least one light beam.

[0068] As illustrated in FIG. 4, the method 100 comprises an operation 140 of detecting an object 10 in the predetermined detection zone Zd from the output voltages of the subtractor stage 5 and the summing stage 6 obtained.

[0069] In particular, in first examples of method 100 in which the optoelectronic sensor 1 with which the method 100 can be carried out corresponds to the optoelectronic sensor 1 according to the first examples described above, an object 10 can be detected in the predetermined detection zone when: a) the output voltage of the subtractor stage is positive when the light beam is emitted, and b) the output voltage of the summing stage is greater than the first predetermined voltage threshold when the light beam is emitted.

[0070] In second examples of method 100 in which the optoelectronic sensor 1 with which the method 100 can be carried out corresponds to the optoelectronic sensor 1 according to the second examples described above, the operation 110 of emitting at least one light beam may comprise an operation 111 of emitting of a time sequence of light beams in a predetermined time interval using the light source 2.

[0071] In these second method examples 100, the output voltage of the subtractor stage 5 and the output voltage of the summing stage 6 comprise amplitudes generated by the light beams of the sequence of light beams.

[0072] In these second examples of method 100, the method 100 may further comprise an operation 131 of processing the output voltage of the subtractor stage 5 by inverting the output voltage (v a - v b) of the subtractor stage 5 during the time intervals between the emission of two consecutive light beams of the time sequence of light beams and then integrating the partially rectified voltage (V-) to obtain the detection signal of the subtractor VDIFF. The detection signal of the subtractor VDIFF is therefore dependent on the number of light beams of the time sequence. It can be obtained from the first controlled inverter 11a of the controlled inverter stage 11 and the first integrator 14a of the integrator stage 14.

[0073] In these second examples of method 100, the method 100 may further comprise an operation 132 of processing the output voltage of the summing stage 6 by inverting the output voltage (va + vb) of the summing stage 6 during the time intervals between the emission of two consecutive light beams of the time sequence of light beams and then integrating the partially rectified voltage (V+) to obtain the detection signal of the summing stage VSUM. The detection signal of the summing stage VSUM is therefore dependent on the number of light beams of the time sequence. It may be obtained from the second controlled inverter 11b of the controlled inverter stage 11 and the second integrator 14b of the integrator stage 14.

[0074] Finally, in these second examples of method 100, the operation 140 of detecting an object 10 in the predetermined detection zone may further comprise an operation 141 of detecting an object 10 in the predetermined detection zone when: a) the detection signal of the subtractor VDIFF is positive, and b) the detection signal of the adder is greater than the second determined voltage threshold vth2.

[0075] Therefore, the examples of optoelectronic sensor 1 and detection method 100 presented in the present disclosure make it possible to guarantee the stability of the detection by ensuring a sufficient signal-to-noise ratio, whether it is the electronic noise introduced by the various electronic components of the optoelectronic sensor, or the noise introduced by the ambient light in the generation of the current by the photodiodes. In this case, the fact that the optoelectronic sensor 1 according to the present disclosure uses the output voltage of a summing stage 6 adding the voltages from the currents generated by the first 3a and the second 3b photodiodes in the detection of an object 10 in the predetermined detection zone makes it possible to guarantee the stability of the detection (object detected or not detected) by ensuring a sufficient signal-to-noise ratio making it possible to avoid switching from one state to another due to noise. Furthermore, in the second examples of optoelectronic sensor 1 based on the emission of a time sequence of light beams to detect an object 10 in the predetermined zone Zd, the influence of noise in the stability of the detection is further reduced.Indeed, the noise on the voltages is filtered by the combination of the controlled inverter stage 11 and the integrator stage 14 and the output voltages compared to detect or not an object, that is to say the detection signals VDIFF and VSUM, have an increased level compared to the first examples, which further increases the signal to noise ratio, thus improving the stability of the detection.

Claims

Claims

1. Optoelectronic sensor (1) configured to detect the presence of an object (10) in a predetermined detection zone (Zd) by reflection of at least one light beam on said object (10), the optoelectronic sensor (1) comprising: - a light source (2) adapted to emit the at least one light beam according to a predetermined orientation; - a first photodiode (3a) configured to generate a first electric current (ia) as a function of a first light flux on the first photodiode (3a); - a second photodiode (3b) configured to generate a second electric current (ib) as a function of a second light flux on the second photodiode (3b);a position of the first (3a) and the second (3b) photodiodes is determined so that a difference between the first luminous flux received by the first photodiode (3a) and the second luminous flux received by the second photodiode (3b) is positive when the light beam is reflected by an object (10) positioned in the predetermined detection zone (Zd); - a converter stage configured to convert the first (ia) and second (ib) electric currents into first (va) and second (vb) electric voltages; - a subtractor stage (5) configured to generate an output voltage by subtracting the second electric voltage (vb) from the first electric voltage (va); - a summing stage (6) configured to generate an output voltage by adding the first electric voltage (va) to the second electric voltage (vb);wherein the optoelectronic sensor further comprises a controlled inverter stage (11) and an integrator stage (14), the controlled inverter stage (11) comprising: - a first controlled inverter (11a) connected to the subtractor stage (5) and configured to invert the output voltage of the subtractor stage (5) during the time intervals between the emission of two consecutive light beams of the time sequence of light beams; - a second controlled inverter (11b) connected to the summing stage (6) and configured to invert the output voltage of the summing stage (6) during the; time intervals between the emission of two consecutive light beams of the time sequence of light beams; the integrator stage (14) comprising: - a first integrator (14a) connected to the first controlled inverter (11a) and configured to integrate the output voltage of the subtractor stage (5) partly inverted by the first controlled inverter stage (11a), so as to obtain a subtractor detection signal (V DIFF); and - a second integrator (14b) connected to the second controlled inverter (11b) and configured to integrate the output voltage of the summing stage (6) partly inverted by the second controlled inverter stage (11b), so as to obtain a summing detection signal (VSUM); and and wherein the optoelectronic sensor is configured to detect an object (10) in the predetermined detection zone (Zd) when: a) the subtractor detection signal (VDIFF) is positive, and b) the summing detection signal (VSUM) is greater than a second determined voltage threshold (vth2).

2. Optoelectronic sensor according to the preceding claim, comprising a signal amplifier stage capable of amplifying the first and second electrical currents or capable of amplifying the first and second electrical voltages.

3. Optoelectronic sensor according to any one of the preceding claims, wherein the converter stage (4) is also an amplifier stage and comprises a first transimpedance amplifier (41a) capable of amplifying and converting the first electric current (ia) into a first electric voltage (va) and a second transimpedance amplifier (41b) capable of amplifying and converting the second electric current (ib) into a second electric voltage (vb).

4. Optoelectronic sensor according to the preceding claim, further comprising an ambient light compensation stage (13) configured to reduce the share of the current induced by ambient light in the current generated by the photodiodes.

5. Optoelectronic sensor according to any one of the preceding claims, wherein the subtractor stage (5) and the summing stage (6) also comprise an amplifier amplifying their respective output voltage.

6. An optoelectronic sensor according to any preceding claim, further comprising a filtering stage (F) configured to filter the first (v a ) and the second (v b) electrical voltages.

7. Optoelectronic sensor according to any one of the preceding claims, further comprising: - an emitting lens (21) arranged opposite the light source (2) so as to be crossed by the light beam emitted by the light source; and - a receiving lens (31) arranged opposite the first (3a) and second (3b) photodiodes so as to be crossed by the fluxes received by the first and second photodiodes.

8. Method for detecting an object (10) in a predetermined detection zone (Zd) by reflecting at least one light beam on the object using an optoelectronic sensor (1) according to any one of the preceding claims, the method comprising: - emitting (110) a time sequence of light beams in a predetermined time interval using the light source;- obtaining (120) the output voltage of the subtractor stage (5) during the predetermined time interval, the output voltage of the subtractor stage (5) being composed of amplitudes generated by the light beams of the sequence of light beams; - processing (131) the output voltage of the subtractor stage (5) by inverting the output voltage of the subtractor stage (5) during the time intervals between the emission of two consecutive light beams of the time sequence of light beams and then integrating the partially rectified voltage to obtain a subtractor detection signal (VDIFF), from the first controlled inverter (11a) and the first integrator (14a); - obtaining (130) the output voltage of the summing stage (6) during the predetermined time interval, the output voltage of the summing stage (6) being composed of amplitudes generated by the light beams of the sequence of light beams;- processing (132) the output voltage of the summing stage (6) by inverting the output voltage of the summing stage (6) during the time intervals between the emission of two consecutive light beams of the time sequence of light beams and then integrating the partially rectified voltage to obtain a signal; of the summing detection (V SUM ), from the second controlled inverter (11b) and the second integrator (14b); and - detecting (140) the object in the predetermined detection zone when: a) the detection signal from the subtractor (V DIFF ) is positive; and b) the detection signal of the adder (V SUM ) is greater than a second determined voltage threshold (v th2 ).

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