Optoelectronic sensor and method for operating an optoelectronic sensor

Abstract

An optoelectronic sensor (1) comprising an emitter (10), a first detector (21), a second detector (22) and a reflector (30) is described herein. The reflector (30) is arranged at a variable reflector distance (30D) from the detectors (21, 22). The emitter (10) is configured to emit a sensing radiation (100) towards the reflector (30). The first detector (21) is arranged at a first detector distance (21D) from the emitter (10) and the second detector (22) is arranged at a second detector distance (22D) from the emitter (10), wherein the first and second detector distances (21D, 22D) differ from each other. The first and second detectors (21, 22) are each configured to detect a reflection (101, 102) of the sensing radiation (100). Furthermore, a method for operating an optoelectronic sensor (1) is provided.

Description

[0001] Description

[0002] OPTOELECTRONIC SENSOR AND METHOD FOR OPERATING AN OPTOELECTRONIC SENSOR

[0003] The present application relates to an optoelectronic sensor and a method for operating an optoelectronic sensor .

[0004] It is an obj ect to provide an optoelectronic sensor with improved accuracy .

[0005] It is a further obj ect to provide a method for operating an optoelectronic sensor with improved accuracy .

[0006] These obj ects are achieved by a device and a method according to the independent patent claims . Advantageous embodiments and further developments of the device and the method are the subj ect of the dependent patent claims and furthermore result from the following description and the figures .

[0007] According to at least one embodiment , the optoelectronic sensor comprises an emitter, a first detector, a second detector and a reflector . The emitter is preferably a semiconductor emitter having a pn j unction . In particular, the emitter is a vertically-emitting laser diode . The first and second detectors are preferably semiconductor detectors , such as photodiodes .

[0008] According to at least one embodiment of the optoelectronic sensor, the reflector is arranged at a variable reflector distance from the detectors . The reflector is arranged along a lateral direction over the detectors . The lateral direction is a direction oriented parallel to a main direction of extension of the optical sensor . Preferably, the reflector can be bent and / or moved by a user toward the detectors . In other words , the reflector is , in particular, flexible and elastically deformable . For example , the distance of the reflector to the detectors can vary due to a touch force acting on the reflector . Particularly preferably, the reflector can be bent by a user and / or moved by a user, in particular towards the emitter and the first and second detectors , such that a force input can cause a change in distance of at least a part of the reflector . Preferably, the reflector can comprise a plastic or can be made of plastic, for instance ABS ( acrylonitrile butadiene styrene ) .

[0009] According to at least one embodiment of the optoelectronic sensor, the emitter is configured to emit a sensing radiation towards the reflector . In particular, a main emission direction of the emitter is oriented at least substantially parallel to a vertical direction . The vertical direction is oriented orthogonally to the lateral direction . The sensing radiation preferably comprises a global intensity peak in the infrared spectral region .

[0010] According to at least one embodiment of the optoelectronic sensor, the first detector is arranged at a first detector distance from the emitter and the second detector is arranged at a second detector distance from the emitter, wherein the first and second detector distances di f fer from each other . The first and second detector distances are measured in the lateral direction . By arranging the first and second detectors at di f ferent distances from the emitter, both detectors also have di f ferent proximity curves . A proximity curve represents the intensity of sensing radiation reflected by the reflector to a detector depending on a varying reflector distance . The first detector distance is preferably at most 300 pm and the second detector distance is at most 600 pm . A small detector distance enables the production of an optoelectronic sensor having a small footprint .

[0011] According to at least one embodiment of the optoelectronic sensor, the first and second detectors are each configured to detect a reflection of the sensing radiation . In other words , a spectral sensitivity of the first and second detectors overlaps with the emission spectrum of the sensing radiation emitted by the emitter .

[0012] According to at least one embodiment , the optoelectronic sensor comprises :

[0013] - an emitter, a first detector, a second detector and a reflector, wherein

[0014] - the reflector is arranged at a variable reflector distance from the detectors ,

[0015] - the emitter is configured to emit a sensing radiation towards the reflector,

[0016] - the first detector is arranged at a first detector distance from the emitter and the second detector is arranged at a second detector distance from the emitter, wherein the first and second detector distance di f fer from each other, and

[0017] - the first and second detectors are each configured to detect a reflection of the sensing radiation .

[0018] An optoelectronic sensor described herein is , inter alia, based on the following considerations : Optoelectronic sensors such as optical proximity sensors , for example , often use a detector to measure the intensity of radiation emitted by an emitter and reflected by a target to determine a distance between the sensor and the target . However, the output of radiation of the emitter as well as the detectors ' sensitivity can depend on temperature . Thus , a change of temperature can have an unwanted impact on the sensor readings .

[0019] The optoelectronic sensor described herein, among other things , makes use of the idea of using at least two detectors which are arranged close to each other and calculating a di f ferential value of the signals gained from each of the detectors . Thus , the influence of a temperature change on output of radiation of the emitter and / or the detectors ' sensitivity would af fect both detectors in the same way and thus be cancelled out . Advantageously, such an optoelectronic sensor can dispense with complicated electronic circuits configured for compensating an output of radiation of the emitter and / or a detector' s sensitivity based on a measured temperature or the like .

[0020] According to at least one embodiment of the optoelectronic sensor, the first and second detectors are arranged at a detector distance from each other of at most 5 mm, preferably at most 1 mm, particularly preferably of at most 300 pm . A small detector distance is particularly advantageous for exposing both detectors to the same temperature .

[0021] According to at least one embodiment of the optoelectronic sensor, the first and second detectors and the emitter are arranged on a straight line . Such an arrangement advantageously enables a di f ferent distance of the first and second detectors relative to the emitter, while also maintaining a small distance of the first and second detector to each other . Thus , the first and second detectors can have di f fering proximity curves and still have an advantageously small temperature di f ference between them .

[0022] According to at least one embodiment of the optoelectronic sensor, the first and second detectors are based on the same material . Preferably, the first and second detectors are made with silicon . In particular, the first and second detectors are manufactured using the same method of production . This can result in the first and second detector having advantageously similar temperature characteristics .

[0023] According to at least one embodiment of the optoelectronic sensor, the first and second detectors are arranged on a common detector substrate . The detector substrate is made with silicon, for example . In particular, the first and second detectors are at least partially embedded in the detector substrate .

[0024] According to at least one embodiment of the optoelectronic sensor, the first and second detectors are monolithically integrated in a detector substrate . In particular, the first and second detectors are epitaxially grown on one single detector substrate .

[0025] According to at least one embodiment of the optoelectronic sensor, the first and second detectors are of equal lateral extension . Here and in the following, "equal" means identical within a manufacturing tolerance . An equal lateral extension of the first and second detectors can be helpful to achieve equal electrical characteristics of the first and second detectors . According to at least one embodiment of the optoelectronic sensor, the first and second detectors comprise an equal vertical layer composition . For example , the first and second detectors have an equal number of di f ferent semiconductor layers , wherein in particular each layer in the first detector has an equal thickness compared to the corresponding layer in the second detector .

[0026] According to at least one embodiment of the optoelectronic sensor, the first and second detectors have equal electrical characteristics . In particular, the first and second detectors have an equal forward voltage and / or an equal electrical capacity .

[0027] According to at least one embodiment of the optoelectronic sensor, the first and second detectors have an equal spectral sensitivity . In particular, the first and second detectors have an equal peak sensitivity wavelength, where their spectral sensitivity curve reaches a global maximum .

[0028] According to at least one embodiment of the optoelectronic sensor, an isolation element is arranged between the emitter and the first and second detectors . The isolation element is preferably a thermal insulator . A thermal insulation of the emitter and the detectors can advantageously prevent a change in temperature of the detectors . Alternatively, the emitter can be in contact with a heat sink element .

[0029] According to at least one embodiment of the optoelectronic sensor, the reflector is partially light-transmissive for the sensing radiation . In other words , at least part of the sensing radiation emitted by the emitter transmits through the reflector and exits the reflector at a side remote from the emitter as transmitted light . Transmitted light is particularly suitable for illuminating an area in front of the reflector remote from the emitter . Such an illumination can be used to detect a gesture of a hand or finger of a user without the reflector being touched . In particular, the reflector has a light-transmission of equal to or greater than 1 % and equal to or less than 25% for the sensing radiation .

[0030] According to at least one embodiment of the optoelectronic sensor, the emitter and all detectors of the sensor are arranged in such a way that the emitter cannot directly irradiate sensing radiation onto any detector . Such an arrangement advantageously reduces the noise level for the detection of a reflector distance or a gesture by reflected light .

[0031] According to at least one embodiment of the optoelectronic sensor, the reflector comprises a plate-like part or is formed as a plate . For instance , the reflector can be a cover lid arranged vertically over the emitter and the detectors , such that at least a part of the reflector can change its distance to the detectors .

[0032] According to at least one embodiment of the optoelectronic sensor, the reflector has a reflectivity of equal to or greater than 75% and equal to or less than 99% for the sensing radiation . The reflector can be di f fusively reflective or specularly reflective .

[0033] Furthermore , a method for operating an optoelectronic sensor is disclosed . The method for operating an optoelectronic sensor is particularly suitable for operating an optoelectronic sensor described herein . This means that all features disclosed in connection with the optoelectronic sensor are also disclosed for the method for operating an optoelectronic sensor and vice versa .

[0034] According to at least one embodiment of the method for operating an optoelectronic sensor, an emitter, a first detector, a second detector and a reflector are provided, wherein the reflector is arranged at a variable reflector distance from the detectors , the first detector is arranged at a first detector distance from the emitter and the second detector is arranged at a second detector distance from the emitter .

[0035] According to at least one embodiment of the method for operating an optoelectronic sensor, a sensing radiation is emitted by the emitter towards the reflector .

[0036] According to at least one embodiment of the method for operating an optoelectronic sensor, a first reflection of the sensing radiation is detected in the first detector generating a first intensity signal . In particular, the first detector produces a voltage which is proportional to an intensity of the first reflection of the sensing radiation .

[0037] According to at least one embodiment of the method for operating an optoelectronic sensor, a second reflection of the sensing radiation is detected in the second detector generating a second intensity signal . In particular, the second detector produces a voltage which is proportional to the intensity of the second reflection of the sensing radiation . According to at least one embodiment of the method for operating an optoelectronic sensor, a distance signal is calculated based on the di f ference of the first intensity signal and the second intensity signal . In other words , a di f ferential signal of the first and second intensity signal is calculated . The di f ferential signal of the detectors compensates for temperature dri fts of the emitter signal and of the detectors , because all temperature-dependent variations of the emitter intensity and / or the detectors ' sensitivity are canceled out .

[0038] According to at least one embodiment , the method for operating an optoelectronic sensor comprises the following steps :

[0039] - providing an emitter, a first detector, a second detector and a reflector, wherein

[0040] - the reflector is arranged at a variable reflector distance from the detectors ,

[0041] - the first detector is arranged at a first detector distance from the emitter and the second detector is arranged at a second detector distance from the emitter,

[0042] - emitting a sensing radiation by the emitter towards the reflector,

[0043] - detecting a first reflection of the sensing radiation in the first detector generating a first intensity signal ,

[0044] - detecting a second reflection of the sensing radiation in the second detector generating a second intensity signal , and

[0045] - calculating a distance signal based on a di f ference of the first intensity signal and the second intensity signal .

[0046] According to at least one embodiment of the method for operating the optoelectronic sensor, the reflector distance , the first detector distance and the second detector distance are chosen such that , when the reflector distance is decreased, the first intensity signal increases and the second intensity signal decreases or vice versa . In particular, the first detector distance and the second detector distance are chosen such that , when the reflector distance is increased, the first intensity signal decreases and the second intensity signal increases .

[0047] Consequently, in the di f ferential signal of the first intensity signal and the second intensity signal , the changes in the first and second signal strength sum up and do not cancel each other out , so that the change in the di f ferential signal strength is greater than the changes in the first and second intensity signal strengths . Thus , a force input on the reflector that causes a distance change of the reflector or of at least a part of the reflector can be identi fied by comparing the di f ferential signal to the first and second intensity signals .

[0048] I f a gesture input occurs , which means that an obj ect is present over or on the reflector, as seen from the emitter, but does not press onto the reflector and thus does not reduce the distance of the reflector or of at least a part of the reflector, at least a part of the sensing radiation that is transmitted through the reflector can be reflected by the obj ect back through the reflector and onto the first and second detectors . Consequently, in comparison to a sensor state where the obj ect is absent , more sensing radiation is irradiated onto the first and second detectors . Thus , in the di f ferential signal of the first intensity signal and the second intensity signal , the changes in the first and second signal strength at least partly cancel each other out , so that the amplitude of the change in the di f ferential signal strength is smaller than the amplitudes of the changes in the first and second intensity signals .

[0049] According to at least one embodiment of the method for operating the optoelectronic sensor the first and second intensity signals are normali zed to 100% for the intensity measured at 20 ° C . In particular, the value of the first intensity signal measured at 20 ° C is defined as 100% and all other values of the first intensity signal are normali zed to this value by dividing them by the value of the first intensity signal measured at 20 ° C . The same procedure is carried out for the second intensity signal .

[0050] An optoelectronic sensor described herein is particularly suitable for use in optical force sensors and / or proximity sensors . In particular, the optoelectronic sensor can be used to detect gestures and / or a touch event on a mobile device .

[0051] Further advantages and advantageous designs and further developments of the optoelectronic sensor and the method for operating an optoelectronic sensor will become apparent from the following exemplary embodiments , which are described below in association with the figures .

[0052] In the figures :

[0053] Figures 1A and IB show schematic views of an optoelectronic sensor described herein according to a first exemplary embodiment ,

[0054] Figures 2A and 2B show a schematic view of an optoelectronic sensor described herein and a graph of proximity curves of first and second detectors of an optoelectronic sensor according to the first exemplary embodiment having a first reflector distance ,

[0055] Figures 3A and 3B show a schematic view of an optoelectronic sensor described herein and a graph of proximity curves of first and second detectors of an optoelectronic sensor according to the first exemplary embodiment having a second reflector distance ,

[0056] Figure 4 shows a graph of a first and second intensity signal and a calculated distance signal over time ,

[0057] Figures 5A and 5B show a schematic view of an optoelectronic sensor described herein and a graph of proximity curves of first and second detectors of an optoelectronic sensor according to the first exemplary embodiment at an increasing temperature ,

[0058] Figures 6A and 6B show a schematic view of an optoelectronic sensor described herein and a graph of proximity curves of first and second detectors of an optoelectronic sensor according to the first exemplary embodiment at a decreasing temperature ,

[0059] Figure 7 shows a graph of a first and second detector signal over temperature ,

[0060] Figure 8 shows a normali zed graph of a first and second detector signal over temperature , Figure 9 shows a graph of a deviation of a distance signal over temperature , and

[0061] Figures 10A and 10B show schematic views of an optoelectronic sensor described herein according to a second exemplary embodiment .

[0062] Identical , similar or equivalent elements are marked with the same reference signs in the figures . The figures and the proportions of the elements represented in the figures among each other are not to be considered as true to scale . Rather, individual elements may be oversi zed for better representability and / or comprehensibility .

[0063] Figures 1A and IB show schematic views of an optoelectronic sensor 1 described herein according to a first exemplary embodiment . The schematic view shown in figure 1A is a cross- sectional view . A lateral direction X is oriented along a main plane of extension of the optoelectronic sensor 1 and a vertical direction Y is oriented perpendicular to the lateral direction .

[0064] The optoelectronic sensor 1 comprises an emitter 10 , a first detector 21 , a second detector 22 and a reflector 30 . The emitter 10 is a semiconductor emitter having a pn j unction . In particular, the emitter 10 is a vertically-emitting laser diode . Preferably, the emitter 10 is configured to emit a sensing radiation 100 towards the reflector 30 . Preferably, the emitter 10 comprises an electrical power of less than 10 mW, particularly preferably of less than 5 mW . Less power consumption in the emitter 10 can be beneficial in saving energy and may help to prevent a temperature gradient inside the optoelectronic sensor 1 . A main emission direction of the emitter 10 is oriented at least substantially parallel to the vertical direction Y . The sensing radiation 100 preferably comprises a global intensity peak in the infrared spectral region .

[0065] The first and second detectors 21 , 22 are semiconductor detectors , such as photodiodes . Further, the first and second detectors 21 , 22 are arranged on a detector substrate 200 . In particular, the first and second detectors 21 , 22 are monolithically integrated in the detector substrate 200 . Preferably, the first and second detectors 21 , 22 are epitaxially grown on one single detector substrate 200 .

[0066] The emitter 10 and the detector substrate 200 are arranged on a mounting surface of a carrier 50 . The carrier 50 is mechanically sel f-supporting . Preferably, the carrier 50 is formed with a PCB material . The carrier 50 has a thickness of at least 100 pm, preferably of at least 300 pm . Further, the emitter 10 and detectors 21 , 22 are encapsulated in a housing body 40 . Preferably, the housing body 40 is formed with a mold material , such as epoxy or silicone . In particular, the housing body 40 is translucent for the sensing radiation .

[0067] The reflector 30 is arranged at a variable reflector distance 30D from the detectors 21 , 22 . For instance , the reflector distance 30D of the reflector 30 can be measured along the vertical direction Y from the mounting surface of the carrier 50 , onto which the emitter 10 and detectors 21 , 22 are mounted, or from an emission surface of the emitter 10 and / or from a detection surface of the detectors 21 , 22 or from an upper surface , i . e . a surface that faces the reflector 30 , of the housing body 40 . The reflector 30 extends along the lateral direction X over the detectors 21 , 22 . Preferably, the reflector 30 can be bent and / or moved by a user toward the detectors . In other words , the reflector 30 is , in particular, flexible and elastically deformable . For example , the reflector distance 30D can vary due to a touch force acting on the reflector 30 . Particularly preferably, the reflector 30 can be bent by a user and / or moved by a user, in particular towards the emitter 10 and the first and second detectors 21 , 22 , such that a force input can cause a change in distance of at least a part of the reflector 30 . Preferably, the reflector 30 comprises a plastic or can be made of plastic, for instance ABS ( acrylonitrile butadiene styrene ) .

[0068] The reflector 30 is partially light-transmissive for the sensing radiation 100 . In other words , at least part of the sensing radiation 100 emitted by the emitter 10 transmits through the reflector 30 and exits the reflector 30 at a side remote from the emitter 10 as transmitted light 103 . Transmitted light 103 is particularly suitable for illuminating an area in front of the reflector 30 remote from the emitter 10 . Such an illumination can be used to detect a gesture of a hand or finger of a user without the reflector 30 being touched . In particular, the reflector 30 has a light-transmission of equal to or greater than 1 % and equal to or less than 25% for the sensing radiation 100 .

[0069] The first detector 21 is arranged at a first detector distance 21D from the emitter 10 and the second detector 22 is arranged at a second detector distance 22D from the emitter 10 , wherein the first and second detector distances 21D, 22D di f fer from each other . The first and second detector distances 21D, 22D are measured in the lateral direction X . By arranging the first and second detectors 21 , 22 at di f ferent distances from the emitter 10 , both detectors 21 , 22 also have di f ferent proximity curves PCI , PC2 . A proximity curve represents the intensity of sensing radiation

[0070] 100 reflected by the reflector 30 to a detector depending on a varying reflector distance 30D . The first detector distance 21D is preferably at most 300 pm and the second detector distance 22D is at most 600 pm .

[0071] Furthermore , the first and second detectors 21 , 22 are arranged at a detector distance 23D from each other of at most 5 mm, preferably at most 1 mm, particularly preferably of at most 300 pm . A small detector distance 23D is particularly advantageous for exposing both detectors 21 , 22 to the same temperature .

[0072] The first and second detectors 21 , 22 are each configured to detect a reflection 101 , 102 of the sensing radiation 100 . In other words , a spectral sensitivity of the first and second detectors 21 , 22 overlaps with the emission spectrum of the sensing radiation 100 emitted by the emitter 10 . In particular, the first detector 21 detects a first reflection

[0073] 101 of the sensing radiation 100 and generates a first intensity signal S I and the second detector 22 detects a second reflection 102 of the sensing radiation 100 and generates a second intensity signal S2 .

[0074] Figure IB shows a top view of the optoelectronic sensor 1 in figure 1A. In the top view it becomes apparent that the first and second detectors 21 , 22 and the emitter 10 are arranged on a straight line XD . Preferably, the lateral center points of each of the first and second detectors 21 , 22 and the emitter 10 are arranged on the straight line XD . Such an arrangement advantageously enables a different distance 21D, 22D of the first and second detectors 21, 22 relative to the emitter 10, while also maintaining a small distance 23D of the first and second detectors 21, 22 to each other. Thus, the first and second detectors 21, 22 can have differing proximity curves PCI, PC2 and still have an advantageously small temperature difference between them.

[0075] The detector substrate 200 completely surrounds the first and second detectors 21, 22.

[0076] Figures 2A and 2B show a schematic view of an optoelectronic sensor 1 described herein and a graph of proximity curves PCI, PC2 of first and second detectors 21, 22 of an optoelectronic sensor 1 according to the first exemplary embodiment having a first reflector distance 30D1. The first reflector distance 30D1 represents an idle state of the optoelectronic sensor 1 wherein no external force is applied to the reflector 30.

[0077] Each proximity curve PCI, PC2 represents the intensity of sensing radiation 100 reflected by the reflector 30 to a detector 21, 22 depending on a varying reflector distance 30D. The first proximity curve PCI corresponds to the first intensity signal SI measured by the first detector 21 and the second proximity curve PC2 corresponds to the second intensity signal S2 measured by the second detector 22.

[0078] Both proximity curves PCI, PC2 comprise one global maximum. The maxima of the proximity curves PCI, PC2 are offset from each other. In other words, each proximity curve PCI, PC2 reaches its maximum at different values for the reflector distance 30D. In particular, the first proximity curve PCI reaches its maximum signal intensity at a smaller reflector distance 30D than the second proximity curve PC2 .

[0079] In particular, the first reflector distance 30D1 as well as the first detector distance 21D and the second detector distance 22D as described in connection with Figures 1A and IB are chosen such that the first detector distance 21D determines the first proximity curve PCI defining a dependency of the first intensity signal S I on the reflector distance 30D and the second detector distance 22D determines the second proximity curve PC2 defining a dependency of the second intensity signal S2 on the reflector distance 30D as indicated in Figure 2B . Each of the characteristic proximity curves PCI , PC2 has a maximum at a certain reflector distance 30D, which depends on the respective detector distance 21D, 22D .

[0080] For example , the first detector distance 21D is chosen such that , in the idle state , the maximum of the first proximity curve PCI is at a lower reflector distance 30D than the first height reflector distance 30D1 and, preferably, than a second reflector distance 30D2 , whereas the second detector distance 22D is chosen such that , in the idle state , the maximum of the second proximity curve PC2 is located at a greater reflector distance 30D than the first reflector distance 30D1 .

[0081] Consequently, when the reflector distance 30D is reduced, the first reflection 101 of the sensing radiation 100 that is reflected on the first detector 21 increases , whereas the second reflection 102 of the sensing radiation 100 that is reflected on the second detector 22 decreases . Figures 3A and 3B show a schematic view of an optoelectronic sensor 1 described herein and a graph of proximity curves PCI , PC2 of first and second detectors 21 , 22 of an optoelectronic sensor 1 according to the first exemplary embodiment having a second reflector distance 30D2 .

[0082] The second reflector distance 30D2 is smaller than the first reflector distance 30D1 . For example , when a force input occurs , which means that an obj ect like a user' s finger presses onto the reflector 30 such that the reflector distance 30D of at least a part of the reflector 30 decreases from the first reflector distance 30D1 to the second reflector distance 30D2 , the first reflection 101 of the sensing radiation 100 and the second reflection 102 of the sensing radiation 102 change due to the change in the geometrical relation between the reflector 30 , the emitter 10 and the detectors 21 , 22 .

[0083] When the reflector 30 , or at least a part of the reflector 30 , is at the second reflector distance 30D2 , more sensing radiation 100 is reflected onto the first detector 21 and less sensing radiation 100 is reflected onto the second detector 22 in comparison to the idle state .

[0084] Consequently, as indicated in Figure 3B, when the reflector 30 or at least a part of the reflector 30 is at the second reflector distance 30D2 , the first detector 21 outputs a first intensity signal S I ' which is increased and the second detector 22 outputs a second intensity signal S2 ' which is decreased in comparison to the first and second intensity signals ' strengths S I , S2 produced in the idle state wherein the reflector was arranged at the first reflector distance 30D1 . When a gesture input occurs , which means that an obj ect like a user' s finger or hand is present over or on the reflector 30 , as seen from the emitter 10 , but does not press onto the reflector 30 and thus does not reduce the reflector distance 30D, at least a part of the transmitted radiation 103 of the sensing radiation 100 that is transmitted through the reflector 30 can be reflected by the obj ect back through the reflector 30 and onto the detectors 21 , 22 . Consequently, in comparison to the idle state of the optoelectronic sensor 1 when the obj ect is absent , more sensing radiation 100 is irradiated onto the first detector 21 and more sensing radiation 100 is irradiated onto the second detector 22 . Therefore , both proximity curves PCI and PC2 are shi fted towards higher intensities . Thus , the first and second detectors 21 , 22 both generate first and second intensity signals S I , S2 which are both increased in comparison to the intensity signals S I , S2 generated in the idle state .

[0085] Figure 4 shows a graph of a first and second intensity signal S I , S2 and a calculated distance signal DS over time t . The first and second intensity signals S I , S2 correspond to the intensity of first and second reflections 101 , 102 of a sensing radiation 100 detected by the first and second detectors 21 , 22 of an optoelectronic sensor 1 according to the first embodiment .

[0086] A plurality of force events FE occurs over the time interval shown in figure 4 . Each force event FE causes a decrease in the reflector distance S OD . Thus , the first intensity signal S I increases and the second intensity signal decreases for the duration of the force event FE . The distance signal DS is calculated from a di f ference between the first and second intensity signals SI, S2. Advantageously, the distance signal DS shows a large sensitivity to the force events FE, which enables an easy detection of force.

[0087] Figures 5A and 5B show a schematic view of an optoelectronic sensor 1 described herein and a graph of proximity curves PCI, PC2 of first and second detectors 21, 22 of an optoelectronic sensor 1 according to the first exemplary embodiment at an increasing temperature T.

[0088] Rising temperature T lowers the efficiency of the emitter 10 and / or the detectors 21, 22. Consequently, in comparison to the room temperature state of the optoelectronic sensor 1, less sensing radiation 100 is irradiated onto the first detector 21 and less sensing radiation 100 is irradiated onto the second detector 22. Therefore, both proximity curves PCI and PC2 are shifted towards lower intensities. Thus, the first and second detectors 21, 22 both generate first and second intensity signals SI, S2 which are both decreased in comparison to the intensity signals SI, S2 generated in the room temperature state.

[0089] However, such a change in temperature T does not affect a difference between the first and second intensity signals SI, S2, because they are equally shifted towards the same direction. Thus, a distance signal calculated from a difference between the first and second intensity signals SI, S2 is not dependent from temperature T.

[0090] Figures 6A and 6B show a schematic view of an optoelectronic sensor 1 described herein and a graph of proximity curves PCI, PC2 of first and second detectors 21, 22 of an optoelectronic sensor 1 according to the first exemplary embodiment at a decreasing temperature T.

[0091] Falling temperature T improves the efficiency of the emitter 10 and / or the detectors 21, 22. Consequently, in comparison to the room temperature state of the optoelectronic sensor 1, more sensing radiation 100 is irradiated onto the first detector 21 and more sensing radiation 100 is irradiated onto the second detector 22. Therefore, both proximity curves PCI and PC2 are shifted towards higher intensities. Thus, the first and second detectors 21, 22 both generate first and second intensity signals SI, S2 which are both increased in comparison to the intensity signals SI, S2 generated in the room temperature state.

[0092] However, such a change in temperature T does not affect a difference between the first and second intensity signal SI, S2, because they are equally shifted towards the same direction. Thus, a distance signal calculated from a difference between the first and second intensity signals SI, S2 is not dependent from temperature T.

[0093] Figure 7 shows a graph of a first and second detector signal SI, S2 over temperature T. As described earlier in connection with figures 5 and 6, the detected intensity signals SI, S2 of the first and second detectors 21, 22 decrease with increasing temperature T due to lower efficiencies in the emitter 10 and / or the first and second detectors 21, 22.

[0094] Figure 8 shows a normalized graph of a first and second detector signal SI, S2 over temperature T. In other words, the intensity signal SI, S2 of each detector 21, 22 measured at a temperature of 20°C is set as a 100% value and each further value is normalized by dividing through the signal intensity SI, S2 value at 20°C. This results in two temperature dependent intensity signal graphs which are nearly exactly arranged on top of each other.

[0095] Figure 9 shows a graph of a deviation of a distance signal DS over temperature T. As described earlier, the distance signal DS is generated by calculating the difference of the first and second intensity signal SI, S2. Figure 9 shows a deviation of a differential distance signal DS of the intensity signals SI, S2 shown in figure 7. According to figure 9, the calculated distance signal DS only deviates about ±0.1% over a temperature interval of 10°C to 60°C.

[0096] Figures 10A and 10B show schematic views of an optoelectronic sensor 1 described herein according to a second exemplary embodiment .

[0097] The second embodiment is essentially equal to the first embodiment shown in figures 1A and IB. Additionally, the optoelectronic sensor 1 according to the second embodiment comprises an isolation element 30 which is arranged between the emitter 10 and the first and second detectors 21, 22. The isolation element 60 is preferably a thermal insulator. A thermal insulation of the emitter 10 and the detectors 21, 22 can advantageously prevent a change in temperature of the detectors 21, 22. Alternatively, the emitter 10 can be in contact with a heat sink element.

[0098] The invention described herein is not limited by the description given with reference to the exemplary embodiments. Rather, the invention encompasses any novel feature and any combination of features, including in particular any combination of features in the claims, even if this feature or this combination is not itself explicitly indicated in the claims or exemplary embodiments. This patent application claims the priority of the German patent application 102024101435.0, the disclosure content of which is hereby incorporated by reference.

[0099] References

[0100] 1 optoelectronic sensor

[0101] 10 emitter

[0102] 21 first detector

[0103] 22 second detector

[0104] 200 detector substrate

[0105] 30 reflector

[0106] 40 housing body

[0107] 50 carrier

[0108] 60 isolation element

[0109] 100 sensing radiation

[0110] 101 first reflection

[0111] 102 second reflection

[0112] 103 transmitted radiation

[0113] X lateral direction

[0114] Y vertical direction

[0115] 21D first detector distance

[0116] 22D second detector distance

[0117] 23D detector distance

[0118] 30D reflector distance

[0119] 30D1 first reflector distance

[0120] 30D2 second reflector distance

[0121] XD straight line

[0122] S intensity signal

[0123] DS distance signal

[0124] PCI first proximity curve

[0125] PC2 second proximity curve

[0126] 51 , S I ' first intensity signal

[0127] 52 , S2 ' second intensity signal t time

[0128] T temperature

[0129] FE force event

Claims

Claims1. Optoelectronic sensor (1) comprising:- an emitter (10) , a first detector (21) , a second detector (22) and a reflector (30) , wherein- the reflector (30) is arranged at a variable reflector distance (30D) from the detectors (21, 22) ,- the emitter (10) is configured to emit a sensing radiation (100) towards the reflector (30) ,- the first detector (21) is arranged at a first detector distance (21D) from the emitter (10) and the second detector (22) is arranged at a second detector distance (22D) from the emitter (10) , wherein the first and second detector distances (21D, 22D) differ from each other,- the first and second detectors (21, 22) are each configured to detect a reflection (101, 102) of the sensing radiation (100) , and- the first and second detectors (21, 22) are monolithically integrated in a detector substrate (200) .

2. Optoelectronic sensor (1) according to the preceding claim, wherein- the first and second detectors (21, 22) are arranged at a detector distance (23D) from each other of at most 5 mm, preferably at most 1 mm, particularly preferably of at most 300 pm .

3. Optoelectronic sensor (1) according to one of the preceding claims, wherein- the first and second detectors (21, 22) and the emitter (10) are arranged on a straight line (XD) .

4. Optoelectronic sensor (1) according to one of the preceding claims, wherein- the first and second detectors (21, 22) are based on the same material.

5. Optoelectronic sensor (1) according to one of the preceding claims, wherein- the first and second detectors (21, 22) are arranged on a common detector substrate (200) .

6. Optoelectronic sensor (1) according to one of the preceding claims, wherein the first and second detectors ( 21 , 22) are epitaxially grown on one single detector substrate (200) .

7. Optoelectronic sensor (1) according to one of the preceding claims, wherein- the first and second detectors (21, 22) are of equal lateral extension.

8. Optoelectronic sensor (1) according to one of the preceding claims, wherein- the first and second detectors (21, 22) comprise an equal vertical layer composition.

9. Optoelectronic sensor (1) according to one of the preceding claims, wherein- the first and second detectors (21, 22) have equal electrical characteristics.

10. Optoelectronic sensor (1) according to one of the preceding claims, wherein- the first and second detectors (21, 22) have an equal spectral sensitivity.

11. Optoelectronic sensor (1) according to one of the preceding claims, wherein- an isolation element (60) is arranged between the emitter (10) and the first and second detectors (21, 22) .

12. Optoelectronic sensor (1) according to one of the preceding claims, wherein- the reflector (30) is partially light-transmissive for the sensing radiation (100) .

13. Optoelectronic sensor (1) according to one of the preceding claims, wherein- the emitter (10) and all detectors (21, 22) of the sensor (1) are arranged in such a way that the emitter (10) cannot directly irradiate sensor light (100) onto any detector (21, 22) .

14. Optoelectronic sensor (1) according to one of the preceding claims, wherein- the reflector (30) comprises a plate-like part or is formed as a plate.

15. Optoelectronic sensor (1) according to one of the preceding claims, wherein- the reflector (30) has a reflectivity of equal to or greater than 75% and equal to or less than 99% for the sensing radiation (100) .

16. Method for operating an optoelectronic sensor (1) comprising the following steps:- providing an emitter (10) , a first detector (21) , a second detector (22) and a reflector (30) , wherein- the reflector (30) is arranged at a variable reflector distance (30D) from the detectors (21, 22) ,- the first detector (21) is arranged at a first detector distance (21D) from the emitter (10) and the second detector (22) is arranged at a second detector distance (22D) from the emitter (10) ,- emitting a sensing radiation (100) by the emitter (10) towards the reflector (30) ,- detecting a first reflection (101) of the sensing radiation (100) in the first detector (21) generating a first intensity signal (SI ) ,- detecting a second reflection (102) of the sensing radiation (100) in the second detector (22) generating a second intensity signal (S2) , and- calculating a distance signal (DS) based on a difference of the first intensity signal (SI) and the second intensity signal ( S2 ) .

17. Method for operating an optoelectronic sensor (1) according to the preceding claim, wherein- the reflector distance (SOD) , the first detector distance (21D) and the second detector distance (22D) are chosen such that, when the reflector distance (SOD) is decreased, the first intensity signal (SI) increases and the second intensity signal (S2) decreases or vice versa.

18. Method for operating an optoelectronic sensor (1) according to one of the preceding claims, wherein- the first and second intensity signals (SI, S2) are normalized to 100% for the intensity measured at 20°C.

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