Photoelectric sensor

Abstract

Examples disclose a photosensor configured to detect the presence of an object within a predetermined area by reflection of at least one light beam, the sensor comprising:-a subtraction stage configured to subtract the object within the predetermined area after emission of the at least one light beam; generating an output voltage by subtracting the second voltage generated by the second photodiode from the first voltage generated by the first photodiode; an addition stage configured to generate an output voltage by adding the first voltage and the second voltage; the photosensor is configured such that the 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 object is located within the predetermined area and the light beam is reflected; and detecting the object based on the output voltages of the subtraction stage and the addition stage.

Description

Technical Field

[0001] The present disclosure relates to the field of photosensors configured to detect the presence of an object within a predetermined detection area by reflection of a light beam from the object. Background Art

[0002] Photoelectric sensors are currently used to detect the presence of an object within a predetermined detection area.

[0003] These sensors emit a light beam into a predetermined detection area and monitor the electrical output signal of a photodiode in response to the beam. In this case, the electrical output signal of the photodiode is proportional to the amount of light received by the photodiode. This electrical output signal differs when an object is present or absent from the predetermined detection area because the object reflects the light beam emitted by the sensor. Therefore, monitoring the electrical output signal of the photodiode makes it possible to detect the presence or absence of an object within the predetermined detection area.

[0004] However, the electrical output signal of a photodiode is typically very weak and therefore relatively susceptible to noise. In particular, the light flux surrounding the sensor and the inherent reflective properties of the object being detected (which depends in part on its color) can sometimes alter the sensor's operation.

[0005] The present disclosure aims to improve this situation. Summary of the Invention

[0006] To this end, a photoelectric sensor is proposed, which is configured to detect the presence of an object within a predetermined detection area by reflection of at least one light beam from the object, the photoelectric sensor comprising:

[0007] - a light source adapted to emit at least one light beam in a predetermined orientation;

[0008] - a first photodiode configured to generate a first current according to a first light flux on the first photodiode;

[0009] - a second photodiode configured to generate a second current according to a second light flux on the second photodiode;

[0010] a converter stage configured to convert the first and second currents into first and second voltages;

[0011] a subtractor stage configured to generate an output voltage by subtracting the second voltage from the first voltage;

[0012] a summing stage configured to generate an output voltage by adding the first voltage to the second voltage;

[0013] The photoelectric sensor is configured as follows:

[0014] - such that when an object located within a predetermined detection area reflects the light beam, a difference between a first light flux received by the first photodiode and a second light flux received by the second photodiode is positive; and

[0015] - Detecting an object based on the output voltages of the subtraction and addition stages.

[0016] Optionally, the photosensor further includes a signal amplification stage capable of amplifying the first and second currents, or capable of amplifying the first and second voltages.

[0017] Optionally, the conversion stage is also an amplification stage and includes a first transimpedance amplifier capable of amplifying and converting the first current into a first voltage, and a second transimpedance amplifier capable of amplifying and converting the second current into a second voltage.

[0018] Optionally, the photosensor further comprises an ambient light compensation stage configured to reduce the portion of the current generated by the photodiode caused by ambient light.

[0019] Optionally, the subtraction stage and the addition stage further include amplifiers for amplifying their respective output voltages.

[0020] Optionally, the photosensor further comprises a filtering stage configured to filter the first and second voltages.

[0021] Optionally, the photoelectric sensor further includes:

[0022] an emission lens arranged facing the light source so that the light beam emitted by the light source passes through the emission lens; and

[0023] A receiving lens is arranged facing the first and second photodiodes so that the flux received by the first and second photodiodes passes through the receiving lens.

[0024] In a first option, the photoelectric sensor is configured to detect an object within a predetermined detection area when:

[0025] a) When the beam is emitted, the output voltage of the subtraction stage is positive, and

[0026] b) When the light beam is emitted, the output voltage of the summing stage is greater than a predetermined first voltage threshold.

[0027] In a first option, the first voltage threshold is a hysteresis threshold having a lower bound and an upper bound, the difference between the lower bound and the upper bound being larger than a voltage amplitude predetermined to correspond to a voltage amplitude of noise on the output voltage of the adding stage.

[0028] In the second option, the photoelectric sensor further includes a controlled inverter stage and an integrator stage, wherein the controlled inverter stage includes:

[0029] - a first controlled inverter connected to the subtraction stage and configured to invert the output voltage of the subtraction stage during a time interval between the emission of two consecutive beams of the temporal sequence of light beams;

[0030] - a second controlled inverter connected to the adding stage and configured to invert the output voltage of the adding stage during a time interval between the emission of two consecutive beams of the temporal sequence of light beams;

[0031] The points levels include:

[0032] a first integrator connected to the first controlled inverter and configured to integrate the output voltage of the subtraction stage, which output voltage is partially inverted by the first controlled inversion stage, thereby obtaining a subtraction detection signal; and

[0033] a second integrator connected to the second controlled inverter and configured to integrate the output voltage of the adding stage, which is partially inverted by the second controlled inverting stage, thereby obtaining the added detection signal; and

[0034] The photoelectric sensor is configured to detect an object within a predetermined detection area when:

[0035] a) The subtraction detection signal is positive, and

[0036] b) The summed detection signal is greater than a determined second voltage threshold.

[0037] The present application also relates to a method for detecting the presence of an object within a predetermined detection area by using a reflection of a light beam from the object by any one of the examples of the photosensors presented in the present disclosure, the method comprising:

[0038] emitting at least one light beam at predetermined time intervals using a light source;

[0039] obtaining an output voltage of a subtraction stage during a predetermined time interval, the output voltage of the subtraction stage consisting of an amplitude generated by at least one light beam;

[0040] obtaining an output voltage of the summing stage during a predetermined time interval, the output voltage of the summing stage consisting of the amplitudes of the beam generation of the sequence of beams; and

[0041] An object within a predetermined detection area is detected based on the obtained output voltages of the subtraction stage and the addition stage.

[0042] Optionally, the method is implemented using a photosensor according to the second option, and the method includes:

[0043] emitting a time series of light beams at predetermined time intervals using a light source;

[0044] obtaining an output voltage of the subtraction stage during a predetermined time interval, the output voltage of the subtraction stage consisting of the amplitudes of beam generation of the sequence of beams;

[0045] processing the output voltage of the subtraction stage by inverting the output voltage of the subtraction stage during a time interval between the emission of two consecutive beams of the time series of light beams and then integrating the partially rectified voltage to obtain a subtraction detection signal from the first controlled inverter and the first integrator;

[0046] obtaining an output voltage of the summing stage during a predetermined time interval, the output voltage of the summing stage consisting of the amplitudes of the beam generation of the sequence of beams;

[0047] processing the output voltage of the adding stage by inverting the output voltage of the adding stage during a time interval between the emission of two consecutive beams of the time series of light beams and then integrating the partially rectified voltage to obtain a summed detection signal from the second controlled inverter and the second integrator; and

[0048] Detects objects within the predefined detection area when:

[0049] a) the subtraction detection signal is positive; and

[0050] b) The summed detection signal is greater than a determined second voltage threshold.

[0051] Therefore, the examples of the photosensor and detection method presented in the present disclosure make it possible to ensure detection stability (detection or non-detection of an object) by ensuring a sufficient signal-to-noise ratio, regardless of whether it is electronic noise introduced by the various electronic components of the photosensor or noise introduced by ambient light when the photodiode generates current. In this case, the photosensor according to the present disclosure uses the output voltage of the adder stage when detecting an object within a predetermined detection area, which adds the voltage generated by the current generated by the first and second photodiodes, thereby ensuring detection stability by ensuring a sufficient signal-to-noise ratio, thereby avoiding switching from one state to another (detection or non-detection) due to noise. In addition, in the second photosensor example that detects an object within a predetermined area based on emitting a time-series light beam, the impact of noise on detection stability is further reduced. Specifically, the noise is filtered in voltage by a combination of a controlled inverting stage and an integrating stage, and the output voltage (i.e., the detection signal) used to detect or not detect an object has an increased amplitude level compared to the first example, thereby further improving the signal-to-noise ratio and thus improving detection stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Other features, details, and advantages will become apparent upon reading the following detailed description and analyzing the accompanying drawings, in which:

[0053] Figure 1

[0054] [ Figure 1 ] schematically illustrates an example of a photosensor configured to detect the presence of an object within a predetermined detection area by reflection of a light beam from the object.

[0055] Figure 2

[0056] [ Figure 2 ] shows a basic diagram of detecting objects through triangulation using an example of using a photosensor.

[0057] Figure 3

[0058] [ Figure 3 ] schematically shows another example of a photosensor configured to detect the presence of an object within a predetermined detection area by reflection of a sequence of light beams from the object.

[0059] Figure 4

[0060] [ Figure 4 ] shows a flowchart of an example of a method of using a photosensor according to the present disclosure to detect the presence of an object within a predetermined detection area by reflection of at least one light beam from the object.

[0061] Figure 5a

[0062] [ Figure 5a ] shows the variation over time of the voltage signals measured at the outputs of the various electronic stages of the photosensor in response to the emission of a time series of light beams when an object reflecting the light beam is located within a predetermined detection area.

[0063] Figure 5b

[0064] [ Figure 5b ] shows the variation with time of the voltage signals measured at the outputs of the various electronic stages of the photosensor in response to the presence of an object reflecting the light beam outside the predetermined detection area. Figure 5a The same time sequence of the beam emission used in . DETAILED DESCRIPTION

[0065] Now refer to Figures 1 to 3An example of a photosensor 1 configured to detect the presence of an object 10 within a predetermined detection area by reflection of at least one light beam from the object is described. The photosensor 1 may correspond to a background suppression sensor that detects the presence of an object by triangulation.

[0066] Photosensor 1 includes a light source 2 designed to emit at least one light beam in a predetermined orientation. In some examples detailed below, light source 2 is designed to emit a time-series of light beams. Light source 2 may, for example, correspond to a light-emitting diode. It is the reflection of at least one light beam from object 10 that makes it possible to determine its presence, particularly through triangulation, as described below. A predetermined detection zone Zd is thus defined based on the predetermined orientation of the light beam when sensor 1 is in use. The light beam may, for example, correspond to a red or infrared beam.

[0067] The photosensor 1 includes a first photodiode 3a and a second photodiode 3b. The first photodiode 3a is configured to generate a first current i according to a first light flux received by the first photodiode 3a. a Likewise, the second photodiode 3b is configured to generate a second current i according to the second light flux received by the second photodiode 3b. b .like Figure 3 As shown, each photodiode is connected to the ground of the photosensor.

[0068] The photosensor 1 comprises a conversion stage 4 configured to convert the first and second currents generated by the first and second photodiodes 3a and 3b, respectively, into first and second voltages v a and v b The conversion stage 4 thus converts the first current i generated by the first photodiode 3a from the luminous flux received therefrom a Converted to the first voltage v a It also generates the second current i generated by the second photodiode 3b from the light flux received therefrom. b Converted to the second voltage v b .

[0069] The photosensor 1 comprises a subtraction stage 5. The subtraction stage 5 is configured to obtain a first voltage v a Subtract the second voltage v b To generate the output voltage. The subtraction stage 5 may further include an amplifier for amplifying the output voltage of the subtraction stage. In some examples, the subtraction stage 5 may include an operational amplifier.

[0070] The photosensor 1 comprises an adding stage 6. The adding stage 6 is configured to add a first voltage v a Added to the second voltage v bTo generate the output voltage. The summing stage 6 may further include an amplifier for amplifying the output voltage of the summing stage. In some examples, the summing stage 6 may include an operational amplifier.

[0071] The photoelectric sensor 1 is configured so that when an object located within a predetermined detection area reflects a light beam, the difference between the first light flux received by the first photodiode and the second light flux received by the second photodiode is positive. In this case, the positions of the photodiodes 3a and 3b are determined relative to each other so that when an object located within the predetermined detection area reflects a light beam, the difference between the first light flux received by the first photodiode and the second light flux received by the second photodiode is positive. The photodiodes are arranged side by side and adjacent to each other, as shown in FIG. Figure 2 As shown. The arrangement of the photodiodes 3 and the intended detection area depend directly on the application in which the photoelectric sensor 1 will be used. Thus, the presented photoelectric sensor 1 can be used to detect objects passing a given position relative to the sensor on a conveyor path. This could be, for example, luggage moving on an airport conveyor belt or parts moving on a production line.

[0072] In particular, Figure 2 As shown, the electronic sensor 1 can be used to detect the presence of an object within a detection area by triangulation. Figure 2 A basic diagram of the detection of an object by triangulation using an example of a photosensor 1 according to the present disclosure is shown. This is a side view of an example of the sensor 1 perpendicular to the optical axis of the light beam emitted by the light source 2 when the object 10 is located within a predetermined detection zone Zd (top diagram) and when it is located outside it (bottom diagram). 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 extremes Zd1 and Zd2. The light source 2 of the sensor 10 thus emits a light beam that passes through an emitting lens 21, which is then reflected by the object 10 and then directed by a receiving lens 31 towards the photodiodes 3a and 3b, forming an angle θ between the light beam emitted by the light source 2 and the light beam reflected by the object 10. It will be understood that, as Figure 2 As shown, the angle θ varies depending on the distance of the object 10 from the sensor 1 , as does the light flux received by the photodiode 3 , which depends on the angle. Figure 2The schematic diagram shows that when object 10 is within the predetermined detection zone Zd, only the first photodiode 3a receives the reflected light beam, while when object 10 is outside the predetermined detection zone Zd, only the second photodiode 3b receives the reflected light flux. Therefore, object 10 is detected when the first photodiode 3a receives the reflected light flux. However, this is a schematic illustration for understanding the detection principle used. In reality, depending on the distance of object 10 from sensor 1, the reflected light flux is received by both photodiodes 3 with greater or lesser intensity. Therefore, by comparing these light fluxes using the currents generated by the photodiodes, photosensor 1 is able to detect whether object 10 is within the predetermined detection zone Zd. Specifically, an extreme value Zd2 is determined to correspond to the equivalent received light flux between the two photodiodes 3. When object 10 approaches sensor 1 along the optical axis from this extreme value Zd2, first photodiode 3a receives more reflected light flux than second photodiode 3b, indicating the presence of object 10 within the predetermined detection zone Zd. In contrast, when the object 10 moves away from the sensor 1 along the optical axis from the extreme value Zd2, the reflected light flux received by the first photodiode 3a is less than that received by the second photodiode 3b, indicating that the object 10 does not exist in the predetermined detection area Zd.

[0073] In the present disclosure, the photosensor 1 is configured to detect an object within a predetermined detection area Zd based on the output voltages of the subtraction stage 5 and the addition stage 6 .

[0074] In particular, in some first examples, the photosensor 1 is configured to detect an object within a predetermined detection zone Zd when:

[0075] a) When the light beam is emitted, the output voltage of the subtraction stage 5 is positive, and

[0076] b) When the light beam is emitted, the output voltage of the summing stage 6 is greater than a predetermined first voltage threshold v th1 .

[0077] These first examples are shown in Figure 1 and can detect an object 10 within a predetermined detection area by a single light beam emitted by the light source 2.

[0078] Thus, in these first examples, the photosensor 1 may comprise a comparison stage 7 comprising a first comparator 7a configured to compare the output voltage of the subtraction stage 5 with zero voltage, and a second comparator 7b configured to compare the output voltage of the addition stage 6 with a predetermined first voltage threshold v th1The photoelectric sensor 1 may further include a logic gate 8 that applies an AND function. The logic gate 8 receives the outputs from the first comparator 7a and the second comparator 7b as inputs and sends a logic signal to the detection unit 9. When the logic signal received by the detection unit 9 from the AND gate 8 is 1, the detection unit 9 triggers the detection of the object 10 in the predetermined detection area Zd.

[0079] The positive output voltage of the subtraction stage 5 (condition a) corresponds to the first generated current i a Greater than the second generated current i b This fact theoretically indicates that the light flux received by first photodiode 3a is greater than that received by second photodiode 3b. As long as the photodiodes 3 are arranged so that the light flux received by first photodiode 3a is greater than that received by second photodiode 3b when object 10 is within the predetermined detection zone Zd, object 10 should be detected within the predetermined detection zone when this condition is met. This is the detection principle described above. This detection condition enables the detection distance of an object 10 within the predetermined detection zone Zd by photosensor 1 to be independent of the reflective properties of the object 10 in question. In practice, the detection principle employed by the presented photosensor 1 is based on differences in the light flux received by the photodiodes. Even when the light flux is reflected by an object 10 with weak reflective properties, such as when the object is black, differences in the light flux received by each photodiode will still exist depending on the position of the object 10, even though the light flux received by each photodiode is attenuated. In this respect, the presented photosensor 1 enables detection of an object 10 in this detection process independent of the inherent reflective properties of the object 10 in question.

[0080] However, the inventors have noted that electronic noise introduced by the photodiode 3 and the electronic stages of the photosensor can cause the output voltage of the subtraction stage to be negative after the initial detection of an object to be detected, while the object is still within the predetermined detection zone. This can lead to unstable detection characteristics of the photosensor. In other words, the inventors have noted that the photosensor can detect the presence of an object within the detection zone Zd at time t and then detect its absence at time t+1 due to noise on the output voltage of the subtraction stage 5, making the interpretation of the object detection information relatively complex.

[0081] Therefore, in the first example, the photosensor 1 is further configured to satisfy the condition b) before detecting the object 10 within the predetermined detection area. As described above, the photosensor 1 according to the present disclosure includes the adding stage 6, which adds the first and second voltages v a and v b The photosensor is further configured to compare the sum with a predetermined first voltage threshold value v th1 In order to detect an object within a predetermined detection zone Zd, the output voltage (va +v b ) and a predetermined first voltage threshold v th1 Performing the comparison enables good detection stability to be guaranteed by ensuring a sufficient signal-to-noise ratio.

[0082] In addition, verify that the first and second output voltages v a and v b The sum of is greater than the threshold (v th1 ) also makes it possible to distinguish between the case where an object is located at a distance corresponding to an extreme value Zd2 of the predetermined zone Zd (for which the currents generated by the photodiodes are equal; therefore the output voltage of the subtraction stage is zero) and the case where there is no object facing the sensor at all (the light beam is therefore not reflected and the current generated by the photodiodes is zero, also causing the output voltage of the subtraction stage to be zero).

[0083] In this respect, the addition stage 6 makes it possible to stabilize the detection of an object within a predetermined detection zone Zd by ensuring a signal-to-noise ratio on the output voltage of the addition stage 6 sufficient for making a detection decision, and also makes it possible to distinguish between the case where an object is located at a distance from the sensor corresponding to the extreme value Zd2 and the case where no object reflects the light beam.

[0084] In a first example, the predetermined first voltage threshold v th1 The predetermined first voltage threshold v may be determined based on the average output voltage of the adding stage 5 when there is no object in the detection zone Zd and / or the average output voltage of the adding stage 5 when an object reflects the light beam outside the detection zone Zd. th1 It can be determined, for example, to be greater than a certain percentage of the average output voltage of the adding stage 5 when there is no object in the detection zone and / or greater than a certain percentage of the average output voltage of the adding stage 5 when an object reflects the light beam outside the detection zone Zd. In these first examples, the predetermined first voltage threshold v th1 These alternatives enable detection stability of objects within the predetermined detection zone Zd to be guaranteed by ensuring a sufficient signal-to-noise ratio on the output voltage of the summing stage 6, thereby satisfying the above-mentioned detection condition b).

[0085] In some examples, the predetermined first voltage threshold v th1 is a hysteresis threshold with an upper and a lower bound. In these examples, the photosensor is configured so that when the output voltage of the subtraction stage is positive and when the light beam is emitted, the output voltage of the addition stage 6 is greater than a predetermined first voltage threshold v th1 In these examples, the photoelectric sensor is further configured to detect an object within the predetermined detection zone Zd when the light beam is emitted and the output voltage of the adding stage 6 is lower than a predetermined first voltage threshold v th1The detection of an object is interrupted when the lower limit of the hysteresis threshold is reached. The lower limit of the hysteresis threshold can be determined, for example, based on the maximum noise voltage generated by the electronic components of the sensor on the output voltage of the adding stage 6. In particular, the lower limit of the hysteresis threshold can be determined so that the difference between the lower limit and the upper limit is greater than a voltage amplitude predetermined to correspond to the voltage amplitude of the noise on the output voltage of the adding stage. This voltage amplitude of the noise on the output voltage of the adding stage can be predetermined based on tests performed on the photosensor.

[0086] In some second examples, the photoelectric sensor 1 detects whether an object is present in a predetermined detection area by considering a time sequence of light beams emitted by the light source 2. The light beam sequence means that the light source 2 emits a plurality of light beams at a certain frequency. The time sequence of the light beams is particularly shown in FIG. Figure 5a and Figure 5b In the figure, the reference sign is FL. Figure 5a It shows the temporal variation of the voltage signals measured at the output of the various electronic stages of the photosensor in response to the time sequence of emission of the light beam when an object reflecting the light beam is located within a predetermined detection zone Zd. Figure 5b For its part, it shows the variation of the same voltage signal over time when the object reflecting the light beam is outside the predetermined detection zone Zd, in response to the Figure 5a The same time sequence of the beam emission used in .

[0087] In these second examples, the photosensor 1 may comprise a controlled inversion stage 11 configured to invert the output voltage of the subtraction stage 5 and to perform the same operation on the output voltage of the addition stage 6 during the time interval between the emission of two consecutive beams of the temporal sequence of beams. The controlled inversion stage 11 acts on the output voltage (v a -v b ) output voltage is especially Figure 3 、 Figure 5a and Figure 5b Indicated by the reference symbol V-. Figure 5a and Figure 5b As can be seen from the figure, only the portion of the output voltage signal corresponding to the time interval between the emission of two beams of the sequence is inverted, while the other portions of the voltage signal are not modified. In other words, the controlled inversion stage 11 applies a gain of −1 to the output voltages of the subtraction stage 5 and the addition stage 6 during the time interval between the emission of two consecutive beams of the temporal sequence of beams, and does not modify the other portions forming these output voltages, which is equivalent to considering that the controlled inversion stage 11 applies a gain of 1 to these other portions.

[0088] The controlled inversion stage 11 may thus comprise a first controlled inverter 11 a connected to the output voltage of the subtraction stage 5 and configured to invert the output voltage (v a-v b The controlled inversion stage 11 may further comprise a second controlled inverter 11b connected to the output voltage of the adding stage 6 and configured to invert the output voltage (v a +v b The output voltage of the second controlled inverter 11b is therefore Figure 3 Indicated by the reference symbol V+.

[0089] In a second example, the photosensor 1 may include an integrating stage 14 connected to the controlled inverting stage 11 and configured to integrate the output voltages V− and V+ of the controlled inverting stage 11. The integrating stage 14 may include a first integrator 14a connected to the first controlled inverter 11a and configured to integrate the voltage V− (corresponding to the output voltage (v+) of the subtraction stage 5 partially inverted by the controlled inverting stage 11) a -v b )) is integrated to obtain the first detection signal V DIFF , referred to as the “subtraction detection signal”. The integration stage 14 may further include a second integrator 14b connected to the second controlled inverter 11b and configured to invert the voltage V+ (corresponding to the output voltage (v a +v b )) is integrated to obtain the second detection signal V SUM , called "addition detection signal".

[0090] The subtraction detection signal is a label used to refer to the output voltage of the integration stage 14 , which is associated with the subtraction stage 5 of the photosensor 1 , while the addition detection signal is another label used to refer to the output voltage of the integration stage 14 , which is associated with the addition stage 6 of the photosensor 1 .

[0091] In these second examples, the object 10 is detected within the predetermined detection zone Zd when:

[0092] a) Subtraction detection signal V DIFF is positive; and

[0093] b) Add detection signal V SUM is greater than a determined second voltage threshold v th2 .

[0094] In these second examples, the photosensor 1 may therefore comprise a comparison stage for the integration stage 12 comprising a first comparator 12a configured to compare the output voltage of the first integrator 14a of the integration stage 14 with zero voltage, and a second comparator 12b configured to compare the output voltage of the second integrator 14b of the integration stage 14 with a predetermined second voltage threshold vth2 In these examples, the photosensor 1 may further include a logic gate 8 applying an AND function, which receives the outputs of the first comparator 14 a and the second comparator 14 b as inputs and is configured to send a logic signal to the detection unit 9. When the logic signal received by the detection unit 9 from the AND gate is 1, it triggers the detection of the object 10 within the predetermined detection area.

[0095] These second examples relate to detecting whether an object is present in a predetermined detection area taking into account the temporal sequence of light beams. In this case, the amplitude of the noise on the signal generated by the photodiode and the subsequent amplification stage in response to the received light flux varies with time. Therefore, the amplitude of the noise on the signal generated by the photodiode and the subsequent electronic stage in response to the received light flux varies for each beam in the sequence of light beams emitted by the light source 2. In this respect, the voltage generated at the output of the subtraction stage 5 and / or the addition stage 6 is partially inverted and then integrated in response to the reception of a plurality of light beams emitted by the light source 2, so that the voltage at the output of the integrator is more independent of variable noise than the noise that could be generated by a single beam, since the variability of the noise is averaged by taking into account a plurality of light beams. In this respect, the comparison of these output voltages with the threshold value is less dependent on the electronic noise introduced by the individual elements of the photosensor 1. In particular, as Figure 5a and Figure 5b It is clearly shown in FIG. 1 , and it will be understood that the voltage signal V is the voltage signal V when the object is located within the predetermined detection area Zd. DIFF The voltage signal V when the object is outside the area DIFF The voltage difference between them increases with the number of beams in the temporal sequence of beams, which means that confusion between the two conditions due to electronic noise is greatly reduced.

[0096] Furthermore, it is no longer necessary to synchronize the comparison of the thresholds with the emission of the light beam, as proposed in the first example. In fact, the output voltage V DIFF and V SUM is continuous, meaning that once a time series of beams is emitted and before these voltages are relaxed for the emission of the next time series, the voltages can be compared with their corresponding thresholds (V DIFF is zero voltage, V SUM v th2 ) without having to accurately compare the timing of these voltages.

[0097] In these second examples, the second voltage threshold v th2 The second voltage threshold v is determined based on the number of light beams emitted by the light source 2. In particular, in some examples, the second voltage threshold v th2 is a hysteresis threshold with upper and lower bounds. In these examples, the photosensor is configured to detect the signal V when the subtraction DIFFIs positive and the addition detection signal V SUM Greater than the second voltage threshold v th2 In these examples, the photoelectric sensor is further configured to detect an object within the predetermined detection area Zd when the added detection signal V SUM Below the second voltage threshold v th2 The lower bound of the hysteresis threshold is reached when the object detection is interrupted.

[0098] In this case, the combination of the controlled inversion stage 11 and the integration stage 14 (allowing to obtain the subtraction detection signal V DIFF and the added detection signal V SUM ) forms a synchronous demodulation stage of the time series of light beams. In fact, the emission of the time series of light beams for detecting the presence of an object in the predetermined detection zone Zd can be considered as a way of modulating information about the presence or absence of the object in the predetermined detection zone Zd onto the individual light beams of the time series. Therefore, by performing controlled inversion of these voltages and integrating them, the information from each of these light beams is recombined and converted into voltages, which can be considered as synchronous demodulation of information about the presence or absence of the object. In addition, the combined use of the controlled inversion stage 11 and the integration stage 14 also provides for the first and second voltages v generated by the reflection of the light beam sequence, which may interfere with each other. a and v b In practice, the controlled inversion stage 11 applies positive or negative unity gain to the disturbance signal at the frequency of the sequence, thereby giving the disturbance signal an alternating characteristic so that its integral through the integration stage 14 is zero.

[0099] The photosensor 1 according to the present disclosure thus enables detection stability to be ensured while making negligible the difference in the detection distance of the sensor 1 to the object when the reflection characteristic of the object is not strong or weaker than the light flux.

[0100] The various examples presented in the following paragraphs can be independently combined with the first or second example described above, unless explicitly stated otherwise.

[0101] In some examples, the photosensor 1 includes a transmitting lens 21, such as Figure 2 As shown. The emission lens 21 is arranged facing the light source 2 so that the light beam emitted by the light source passes through it. It enables the rays of the light beam emitted by the light source 2 to be deflected so that they converge at the output.

[0102] In some examples, the photoelectric sensor 1 further includes a receiving lens 31, such as Figure 2 The receiving lens 31 is arranged facing the first and second photodiodes 3a and 3b so that the light fluxes received by the first and second photodiodes 3a and 3b pass through it. The receiving lens 31 enables the light fluxes to be concentrated to the photodiode 3.

[0103] In some examples, the sensor 1 includes a signal amplification stage capable of amplifying the first and second currents i a and i b , or can amplify the first and second voltages v a and v b The signal amplification stage may for example be arranged between the photodiode 3 and the conversion stage 4, in which case it will amplify the first and second currents i a and i b The signal amplification stage can also be arranged between the converter 4 and the adding stage 6 and the subtracting stage 5, in which case it will amplify the first and second voltages v a and v b In some examples, where the subtraction stage 5 and / or the addition stage 6 comprises amplifiers, there are therefore at least two signal amplifications, one applied to the current or voltage and one applied to amplify the output voltage of the subtraction stage 5 and / or the addition stage 6 .

[0104] In some examples, the conversion stage 4 is also an amplifier stage and includes a first transimpedance amplifier 41a capable of amplifying and converting the first current i a Converted to the first voltage v a , and the second transimpedance amplifier 41b, which can amplify and convert the second current i b Converted to the second voltage v b These examples make it possible to use the same electronic components to amplify and convert the current into a voltage, thereby reducing the cost of the sensor and simplifying its design. The conversion stage 4 with the first transimpedance amplifier 41a and the second transimpedance amplifier 41b can thus correspond in particular to the signal amplification stage described above.

[0105] In some examples, the photosensor 1 may include an ambient light compensation stage 13 configured to compensate for a current induced by ambient light in the current generated by the photodiode 3. In some 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 conversion stage, and a second compensation stage 13b connected in antiparallel to the second transimpedance amplifier 41b of the conversion stage 4. More precisely, the first compensation stage 13a may include a first low-pass filter 131a connected to a first amplifier 132a, which is further connected to a first voltage / current converter 133a, as shown. Figure 3 Similarly, the second compensation stage 13b may include a second low-pass filter 131b connected to a second amplifier 132b, and the first amplifier 132a is further connected to a second voltage / current converter 133b.

[0106] In some examples, the photosensor 1 may include a filter stage F configured to filter the first and second voltages v a and vb Filtering is performed before these voltages are subtracted by the subtraction stage 5 or before they are added by the addition stage 6. Thus, the filtering stage F comprises two filters. The filtering stage comprises a filter for filtering the first voltage v a Filter to obtain the filtered voltage v aF The first filter F1, such as Figure 3 The filter stage F includes a filter for the second voltage v b Filter to obtain the filtered voltage v bF The second filter F2, such as Figure 3 As shown. The first and second filters are bandpass filters. These filters are essentially centered on the frequency of the light beam sequence in the second example. Thus, the contribution of spectral components caused by light sources other than the light source 2 of the photosensor 1 to the first and second voltages v is reduced. a and v b Since the detection of the object 10 in the predetermined detection area is based on the first and second voltages v a and v b The use of the bandpass filter makes it possible to substantially filter out the electronic components used in the sensor at the first voltage v a and the second voltage v b The noise introduced on the voltage is not limited to the noise introduced by the photodiode 3, in particular the noise introduced by the photodiode 3, the noise introduced by the conversion stage 4 and, where applicable, the noise introduced by the amplification stage or the ambient light compensation stage 13. In practice, the noise can be considered to be substantially constant over all the frequencies of the signal, so applying a bandpass filter to the voltage makes it possible to suppress the spectral components of the noise which, outside the frequency band considered, are weak compared to the set of frequency bands constituting the signal.

[0107] Now refer to Figure 4 An example of a method 100 for detecting the presence of an object 10 within a predetermined detection area through reflection of a light beam from the object 10 using the photosensor 1 according to the present disclosure is introduced.

[0108] like Figure 4 As shown, the method 100 includes an operation 110 of emitting at least one light beam within a predetermined time interval using a light source 2 .

[0109] like Figure 4 As shown, the method 100 comprises an operation 120 of obtaining, during a predetermined time interval, the output voltage of the subtraction stage 5. The output voltage of the subtraction stage 5 is thus composed of the amplitude generated by the at least one light beam emitted by the light source 2.

[0110] like Figure 4 As shown, the method 100 comprises an operation 130 of obtaining the output voltage of the summing stage 6 during a predetermined time interval. The output voltage of the summing stage 6 also consists of the amplitudes of the beam generation of the beam sequence.

[0111] like Figure 4 As shown, the method 100 includes an operation 140 of detecting the object 10 within a predetermined detection zone Zd based on the obtained output voltages of the subtraction stage 5 and the addition stage 6 .

[0112] In particular, in some first examples of the method 100 that can be performed using the photosensor 1 of the first example described above, the object 10 can be detected within the predetermined detection area when:

[0113] a) When the beam is emitted, the output voltage of the subtraction stage is positive, and

[0114] b) When the light beam is emitted, the output voltage of the summing stage is greater than a predetermined first voltage threshold.

[0115] In some second examples of method 100 that may be performed using the second example photosensor 1 , emitting at least one light beam operation 110 may include emitting a time sequence of light beams within a predetermined time interval using light source 2 111 .

[0116] In a second example of these methods 100 , the output voltage of the subtraction stage 5 and the output voltage of the addition stage 6 comprise amplitudes generated by the beams of the sequence of beams.

[0117] In a second example of these methods 100, the method 100 may further comprise an operation 131 of processing the output voltage of the subtraction stage 5 by inverting the output voltage (v a -v b ), and then integrate the partially rectified voltage (V-) to obtain the subtraction detection signal V DIFF . Subtraction detection signal V DIFF It thus depends on the number of beams in the time sequence. It can come from the first controlled inverter 11 a of the controlled inversion stage 11 and the first integrator 14 a of the integration stage 14 .

[0118] In a second example of these methods 100, the method 100 may further comprise an operation 132 of processing the output voltage of the adding stage 6 by inverting the output voltage (v a +v b ), and then integrate the partially rectified voltage (V+) to obtain the added detection signal V SUM . Addition detection signal V SUM It thus depends on the number of beams in the time sequence. It can come from the second controlled inverter 11 b of the controlled inversion stage 11 and the second integrator 14 b of the integration stage 14 .

[0119] Finally, in a second example of these methods 100, the operation 140 of detecting the object 10 within the predetermined detection area may further include the operation 141 of detecting the object 10 within the predetermined detection area when:

[0120] a) Subtraction detection signal V DIFF is positive; and

[0121] b) The added detection signal is greater than a determined second voltage threshold v th2 .

[0122] Therefore, the examples of the photosensor 1 and the detection method 100 presented in the present disclosure make it possible to guarantee detection stability (detection or non-detection of an object) by ensuring a sufficient signal-to-noise ratio, regardless of whether it is electronic noise introduced by the various electronic components of the photosensor 1 or noise introduced by ambient light when the photodiode generates current. In this case, the photosensor 1 according to the present disclosure uses the output voltage of the addition stage 6 when detecting the object 10 within the predetermined detection area, and the addition stage 6 adds the voltage generated by the current generated by the first and second photodiodes 3a and 3b, thereby ensuring detection stability (detection or non-detection) by ensuring a sufficient signal-to-noise ratio, thereby avoiding switching from one state to another due to noise. In addition, in the second example of the photosensor 1 that detects the object 10 within the predetermined area Zd based on the emission of a time-series light beam, the influence of noise on detection stability is further reduced. Specifically, the noise is filtered in voltage by the combination of the controlled inversion stage 11 and the integration stage 14, and the output voltage (i.e., the detection signal V) used for detecting or not detecting the object is filtered. DIFF and V SUM ) has an increased amplitude level compared to the first example, thereby further improving the signal-to-noise ratio and thus improving detection stability.

Claims

1. A photoelectric sensor (1) configured to detect the presence of an object (10) within a predetermined detection zone (Zd) by reflection of at least one light beam from the object (10), the photoelectric sensor (1) comprising: - a light source (2) adapted to emit at least one light beam in a predetermined orientation; - a first photodiode (3a) configured to generate a first current (i a ); - a second photodiode (3b) configured to generate a second current (i b ); The positions of the first (3a) and second (3b) photodiodes are determined so that when an object (10) located within a predetermined detection zone (Zd) reflects a light beam, a difference between a first light flux received by the first photodiode (3a) and a second light flux received by the second photodiode (3b) is positive; - a conversion stage configured to convert the first (i a ) and the second (i b ) current is converted to the first (v a ) and the second (v b )Voltage; - a subtraction stage (5) configured to obtain a voltage from a first voltage (v a ) minus the second voltage (v b ) to generate the output voltage; - an adding stage (6) configured to add a first voltage (v a ) is applied to the second voltage (v b ) to generate the output voltage; The photoelectric sensor further comprises a controlled inverting stage (11) and an integrating stage (14), wherein the controlled inverting stage (11) comprises: a first controlled inverter (11a) connected to the subtraction stage (5) and configured to invert the output voltage of the subtraction stage (5) during the time interval between the emission of two consecutive beams of the temporal sequence of light beams; a second controlled inverter (11b) connected to the adding stage (6) and configured to invert the output voltage of the adding stage (6) during the time interval between the emission of two consecutive beams of the temporal sequence of light beams; The integral level (14) includes: - a first integrator (14a) connected to the first controlled inverter (11a) and configured to integrate the output voltage of the subtraction stage (5), which is partially inverted by the first controlled inversion stage (11a), thereby obtaining a subtraction detection signal (V DIFF );as well as - a second integrator (14b) connected to the second controlled inverter (11b) and configured to integrate the output voltage of the adding stage (6), which is partially inverted by the second controlled inverting stage (11b), thereby obtaining the added detection signal (V SUM );as well as The photoelectric sensor is configured to detect an object (10) within a predetermined detection zone (Zd) when: a) Subtraction detection signal (V DIFF ) is positive, and b) Addition detection signal (V SUM ) is greater than the determined second voltage threshold (v th2 ).

2. The photosensor according to claim 1, comprising a signal amplification stage capable of amplifying the first and second currents or capable of amplifying the first and second voltages.

3. The photoelectric sensor according to any one of the preceding claims, characterized in that The conversion stage (4) is also an amplifier stage and includes a first transimpedance amplifier (41a) and a second transimpedance amplifier (41b). The first transimpedance amplifier is capable of amplifying and converting the first current (i a ) is converted to the first voltage (v a ), the second transimpedance amplifier can amplify and convert the second current (i b ) is converted into a second voltage (v b ).

4. The photosensor according to the preceding claim, further comprising an ambient light compensation stage (13) configured to reduce the portion of the current generated by the photodiode caused by ambient light.

5. The photoelectric sensor according to any one of the preceding claims, characterized in that The subtraction stage (5) and the addition stage (6) further include amplifiers for amplifying their respective output voltages.

6. The photosensor according to any one of the preceding claims, further comprising a filtering stage (F) configured to filter the first (v a ) and the second (v b ) voltage is filtered.

7. The photosensor according to any one of the preceding claims, further comprising: - an emission lens (21), which is arranged facing the light source (2) so that the light beam emitted by the light source passes through the emission lens; as well as A receiving lens (31) arranged facing the first (3a) and second (3b) photodiodes such that the flux received by the first and second photodiodes passes through the receiving lens.

8. Method for detecting the presence of an object (10) within a predetermined detection zone (Zd) using a photosensor (1) according to any one of the preceding claims by reflection of at least one light beam from the object (10), the method comprising: - using a light source to emit (110) a temporal sequence of light beams at predetermined time intervals; - obtaining (120) an output voltage of the subtraction stage (5) during a predetermined time interval, the output voltage of the subtraction stage (5) consisting of the amplitudes of the beam generation of the sequence of beams; - processing (131) the output voltage of the subtraction stage (5) by inverting the output voltage of the subtraction stage (5) during the time interval between the emission of two consecutive beams of the temporal sequence of beams and then integrating the partially rectified voltage, thereby obtaining a subtraction detection signal (V) from the first controlled inverter (11a) and the first integrator (14) DIFF ); - obtaining (130) an output voltage of the adding stage (6) during a predetermined time interval, the output voltage of the adding stage (6) consisting of the amplitudes of the beam generation of the beam sequence; - processing (132) the output voltage of the adding stage (6) by inverting the output voltage of the adding stage (6) during the time interval between the emission of two consecutive beams of the temporal sequence of beams and then integrating the partially rectified voltage, thereby obtaining a summed detection signal (V) from the second controlled inverter (11b) and the second integrator (14b) SUM );as well as - detecting (140) an object within a predetermined detection area when: a) Subtraction detection signal (V DIFF ) is positive; and b) Addition detection signal (V SUM ) is greater than the determined second voltage threshold (v th2 ).

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