Method for operating an optoelectronic proximity sensor

Abstract

A method can be used for operating an optoelectronic proximity sensor. The proximity sensor includes a radiation-emitting component, a radiation-detecting component and a control unit. The radiation-emitting component is operated by means of a pulsed current. During each measurement period, the pulsed current of the radiation-emitting component has an on-time and an off-time. The pulsed current has a pulse current intensity during the on-time, and the control unit evaluates a detector signal of the radiation-detecting component and lowers the pulse current intensity for a subsequent measurement period, when the detector signal exceeds a threshold value during at least one measurement period.

Claims

1. A method for operating an optoelectronic proximity sensor that comprises a radiation-emitting component, a radiation-detecting component, and a control unit, the method comprising: operating the radiation-emitting component with a pulsed current that has an on-time and an off-time during one measurement period, wherein the pulsed current has a pulse current intensity during the on-time and wherein the measurement period is between 1 ms and 2000 ms; using the control unit to evaluate a detector signal from the radiation-detecting component; and reducing the pulse current intensity for a subsequent measurement period when the detector signal exceeds a threshold value during at least one measurement period.

2. The method according to claim 1, wherein the pulse current intensity for a subsequent measurement period is reduced when the detector signal exceeds the threshold value during exactly one measurement period.

3. The method according to claim 1, wherein the pulse current intensity for a subsequent measurement period is reduced when the detector signal exceeds the threshold value during a predefined number of N consecutive measurement periods, where N2.

4. The method according to claim 3, wherein N=2 or N=3.

5. The method according to claim 1, wherein the pulse current intensity is reduced for at least one additional subsequent measurement period when the detector signal continues to exceed the threshold value during at least one additional measurement period after the reducing the pulse current intensity.

6. The method according to claim 1, wherein reducing the pulse current intensity comprises reducing the pulse current intensity by at least 25%.

7. The method according to claim 6, wherein reducing the pulse current intensity comprises reducing the pulse current intensity by at least 50%.

8. The method according to claim 1, wherein the pulse current intensity for a subsequent measurement period is increased when the detector signal falls below a threshold value during at least one measurement period, and the pulse current intensity is less than a predefined maximum value for the pulse current intensity.

9. The method according to claim 8, wherein the pulse current intensity for a subsequent measurement period is increased when the detector signal falls below the threshold value during exactly one measurement period.

10. The method according to claim 8, wherein the pulse current intensity for a subsequent measurement period is increased when the detector signal falls below the threshold value during a predefined number of N consecutive measurement periods, where N2.

11. The method according to claim 10, wherein N=2 or N=3.

12. The method according to claim 8, wherein the pulse current intensity is increased to the predefined maximum value for the pulse current intensity.

13. The method according to claim 8, wherein the pulse current intensity is increased at least one additional time for at least one additional subsequent measurement period when the detector signal continues to fall below the threshold value during at least one additional measurement period after increasing the pulse current intensity.

14. The method according to claim 8, wherein increasing the pulse current intensity comprises increasing the pulse current intensity by at least 50%.

15. An optoelectronic proximity sensor, comprising: a radiation-emitting component configured to be operated via a pulsed current that has an on-time and an off-time during one measurement period, wherein the pulsed current has a pulse current intensity during the on-time and wherein the measurement period is between 1 ms and 2000 ms; a radiation-detecting component configured to generate a detector signal; and a control unit configured to evaluate the detector signal and reduce the pulse current intensity for a subsequent measurement period when the detector signal exceeds a threshold value during at least one measurement period.

16. The optoelectronic proximity sensor according to claim 15, wherein the pulse current intensity for the subsequent measurement period is reduced when the detector signal exceeds the threshold value during a predefined number of N consecutive measurement periods, where N2.

17. A method for operating an optoelectronic proximity sensor that comprises a radiation-emitting component, a radiation-detecting component, and a control unit, the method comprising: operating the radiation-emitting component with a pulsed current that has an on-time and an off-time during one measurement period, wherein the pulsed current has a pulse current intensity during the on-time; using the control unit to evaluate a detector signal from the radiation-detecting component; reducing the pulse current intensity for a subsequent measurement period when the detector signal exceeds a threshold value during at least one measurement period; and increasing the pulse current intensity by at least 50% for a subsequent measurement period when the detector signal falls below a threshold value during at least one measurement period and the pulse current intensity is less than a predefined maximum value for the pulse current intensity.

18. The method according to claim 17, wherein the pulse current intensity for a subsequent measurement period is reduced when the detector signal exceeds the threshold value during exactly one measurement period and wherein the pulse current intensity for a subsequent measurement period is increased when the detector signal falls below the threshold value during exactly one measurement period.

19. The method according to claim 17, wherein the pulse current intensity for a subsequent measurement period is reduced when the detector signal exceeds the threshold value during a predefined number of N consecutive measurement periods, wherein N=2 or N=3; and wherein the pulse current intensity for a subsequent measurement period is increased when the detector signal falls below the threshold value during a predefined number of N consecutive measurement periods, wherein N=2 or N=3.

20. The method according to claim 17, wherein the measurement period is between 1 ms and 2000 ms.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention is described in greater detail based on exemplary embodiments, with respect to FIGS. 1 to 4.

(2) FIG. 1 shows a schematic representation of an optoelectronic proximity sensor in one exemplary embodiment of the method;

(3) FIG. 2 shows a schematic graphical representation of the time profile of the current I.sub.e(t) of the radiation-emitting component, in one exemplary embodiment of the method;

(4) FIG. 3 shows a schematic graphical representation of the time profile of the current I.sub.e(t) of the radiation-emitting component, in an additional exemplary embodiment of the method; and

(5) FIG. 4 shows a schematic graphical representation of the time profile of the current I.sub.e(t) of the radiation-emitting component, in an additional exemplary embodiment of the method.

(6) The depicted component parts and the ratios of the dimensions of the component parts are not to be considered to be true to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(7) The optoelectronic proximity sensor 1 according to one exemplary embodiment which is depicted in FIG. 1 includes a radiation-emitting component 2 and a radiation-detecting component 3. The radiation-emitting component 2 and the radiation-detecting component 3 may, for example, be installed next to each other on a shared printed circuit board. The radiation-emitting component 2 is preferably a radiation-emitting semiconductor component. The radiation-emitting component 2 is, for example, a light-emitting diode, in particular an infrared light-emitting diode. In particular, the radiation-emitting component 2 may be an IR LED which, for example, has a wavelength between approximately 850 nm and 940 nm.

(8) The radiation-emitting component 2 emits electromagnetic radiation 6 in a radiation direction. If an object 5 is situated near the optoelectronic proximity sensor 1, the electromagnetic radiation 6 emitted by the radiation-emitting component 2 is reflected by it. The reflecting object 5 may in particular be a body part of a user who uses an electrical device into which the optoelectronic proximity sensor 1 is integrated. If the reflecting object 5 is situated near the optoelectronic proximity sensor 1, at least a portion of the electromagnetic radiation 7 reflected by the object 5 strikes the radiation-detecting component 3. The radiation-detecting component 3 is preferably a radiation-detecting semiconductor component, for example, a photodiode, a phototransistor, or another semiconductor component, which is suitable for the detection of the reflected radiation 7.

(9) Furthermore, the optoelectronic proximity sensor 1 includes a control unit 4 which is provided in particular for the electrical control of the radiation-emitting component 2 and the radiation-detecting component 3. The control unit 4 is also used for the evaluation of a detector signal of the radiation-detecting component 3. The control unit 4 may, for example, include an integrated circuit (IC), in particular an application-specific integrated circuit (ASIC). It is also possible that the radiation-detecting component 3 and/or the radiation-emitting component 2 is a semiconductor component which is integrated into an ASIC functioning as a control unit. For example, the radiation-detecting semiconductor component 3 may be a photodiode integrated monolithically into an ASIC.

(10) In the case of the optoelectronic proximity sensor 1, the radiation-emitting component 2 is operated at a pulsed current intensity. An exemplary time profile of the pulsed current intensity I.sub.e(t) is schematically depicted in FIG. 2. During a measurement period T.sub.m, the radiation-emitting component 2 is switched on during an on-time t.sub.on and subsequently switched off for the remaining time t.sub.off of the measurement period T.sub.m. The measurement period T.sub.m is preferably between 1 ms and 2000 ms inclusively.

(11) During the on-time, the radiation-emitting component is operated at a pulse current intensity I.sub.on. The on-time t.sub.on is preferably significantly shorter than the off-time t.sub.off. The duty cycle t.sub.on/T.sub.m is advantageously less than 0.1, preferably less than 0.01, and particularly preferably less than 0.001.

(12) In the example depicted in FIG. 2, in a first measurement period T.sub.m1, a detector signal I.sub.d is detected which is smaller than the threshold value I.sub.th. Since the pulse current intensity I.sub.on1 already has a predefined maximum value I.sub.on,max, the pulse current intensity I.sub.on2 is not increased in the subsequent second measurement period T.sub.m2. In the exemplary embodiment, the detector signal I.sub.d exceeds the threshold value I.sub.th during the second measurement period T.sub.m2 because, for example, a reflecting object is situated near the optical proximity sensor. In this case, the pulse current intensity I.sub.on3 for the subsequent measurement period T.sub.m3 is advantageously reduced by the control unit to a lower value. Preferably, the pulse current intensity is reduced by at least 25%. In the exemplary embodiment, the pulse current intensity I.sub.on3 during the third measurement period T.sub.m3 is reduced by 50% with respect to the preceding measurement period T.sub.m2.

(13) In the exemplary embodiment, during the third measurement period T.sub.m3, despite the reduced pulse current intensity I.sub.on3, radiation reflected by an object near the optoelectronic proximity sensor is still sufficient for the detector signal I.sub.d to continue to exceed the threshold value I.sub.th. In this case, the pulse current intensity I.sub.on4 for the subsequent fourth measurement period T.sub.m4 is again reduced, for example, by another 50%.

(14) Since the detector signal I.sub.d also continues to be greater than the threshold value I.sub.th during the fourth measurement period T.sub.m4, the pulse current intensity I.sub.on5 for the subsequent fifth measurement period T.sub.m5 is again reduced, for example, again by 50%.

(15) Despite the additional reduction of the pulse current intensity I.sub.on5, the detector signal I.sub.d also continues to be greater than the threshold value I.sub.th during the fifth measurement period T.sub.m5.

(16) In the method, it may be provided that the pulse current intensity I.sub.on is not further reduced if it has reached a predefined minimum value I.sub.on,min. In this case, the pulse current intensity I.sub.on for the subsequent measurement period T.sub.m is also not reduced if the detector signal I.sub.d has fallen below the threshold value I.sub.th during the preceding measurement period T.sub.m.

(17) In the exemplary embodiment of FIG. 2, for example, the pulse current intensity I.sub.on5 in the fifth measurement period T.sub.m5 has reached a predefined minimum value I.sub.on,min. The control unit 4 therefore does not further reduce the pulse current intensity I.sub.on6 for the subsequent measurement period T.sub.m6, although the detector signal I.sub.d has exceeded the threshold value I.sub.th. Rather, the radiation-emitting component 2 is also operated at the predefined minimum value I.sub.on,min of the pulse current intensity during the sixth measurement period T.sub.m6.

(18) In the method, the control device 4 is preferably configured to increase the pulse current intensity I.sub.on again if the detector signal I.sub.d has fallen below the threshold value I.sub.th during at least one measurement period and the pulse current intensity I.sub.on is less than a predefined maximum value I.sub.on,max for the pulse current intensity. Such an increase of the pulse current intensity I.sub.on after falling below the threshold value I.sub.th does not necessarily have to take place for the immediately subsequent measurement period T.sub.m, but may, for example, take place only if the detector signal I.sub.d has fallen below the threshold value I.sub.th during a predefined number N of measurement periods. A very short-duration reduction of the detector signal I.sub.d, which, for example, is based on a short-duration movement of the detected object 5, thus remains unconsidered.

(19) In the exemplary embodiment of FIG. 2, it is assumed that the detector signal I.sub.d falls below the threshold value I.sub.th during the sixth measurement period T.sub.m6 because, for example, a previously detected object 5 has moved away from the optoelectronic proximity sensor 1. During the seventh measurement period T.sub.m7, the radiation-emitting component 2 is operated at a pulse current intensity I.sub.on7, which is equal to the pulse current intensity I.sub.on6 of the sixth measurement period T.sub.m6, although the detector signal I.sub.d has fallen below the threshold value I.sub.th during the sixth measurement period T.sub.m6.

(20) The pulse current intensity I.sub.on8 is increased for the subsequent eighth measurement period T.sub.m8 by the control unit 4 only after the detector signal I.sub.d has again fallen below the threshold value I.sub.th during the seventh measurement period T.sub.m7. In the exemplary embodiment, the pulse current intensity I.sub.on8 for the eighth measurement period T.sub.m8 is increased to a predefined maximum pulse current intensity I.sub.on,max which was the initial value during the first measurement period T.sub.m1. Alternatively, it would also be possible to increase the pulse current intensity incrementally in the direction of the maximum value I.sub.on,max, as was also carried out during the reduction of the pulse current intensity in the case of falling below the threshold value I.sub.th.

(21) FIG. 3 schematically depicts another exemplary embodiment of the time profile of the pulsed current I.sub.e(t) of the radiation-emitting component. Unlike the preceding exemplary embodiment, in this exemplary embodiment, a reduction of the pulse current intensity is not already carried out if the detector signal I.sub.d has fallen below the threshold value I.sub.th during exactly one measurement period T.sub.m, but rather, only if the detector signal I.sub.d has exceeded the threshold value I.sub.th during an established number of N=3 measurement periods T.sub.m.

(22) In the exemplary embodiment, for example, during each of the first three measurement periods T.sub.m1, T.sub.m2, T.sub.m3, the threshold value I.sub.th is exceeded by the detector signal I.sub.d. Thus, there is a reduction of the pulse current intensity I.sub.on4 for the subsequent fourth measurement period T.sub.m4. This may, for example, be a halving of the pulse current intensity I.sub.on2=I.sub.on3. In the exemplary embodiment, during the fourth, fifth, and sixth measurement periods T.sub.m4, T.sub.m5, T.sub.m6, the threshold value I.sub.th continues to be exceeded by the detector signal I.sub.d. Since the threshold value I.sub.th has therefore again been exceeded N=3 times, the pulse current intensity I.sub.on7 for the subsequent seventh measurement period T.sub.m7 is again reduced, for example, again halved.

(23) As in the first exemplary embodiment, in the further progression, the pulse current intensity may again be increased in one step or in multiple steps up to a maximum pulse current intensity I.sub.on,max if the threshold value I.sub.th was undershot during a predefined number of N measurement periods T.sub.m.

(24) In one embodiment of the optoelectronic proximity sensor 1, during the on-time t.sub.on, the radiation-emitting component 2 does not emit a single pulse, but rather a pulse sequence. In this embodiment, the time profile of the pulsed current I.sub.e(t) is schematically depicted in FIG. 4 for two measurement periods T.sub.m1, T.sub.m2.

(25) The pulsed current I.sub.e(t) includes a sequence of rectangular pulses during the on-time t.sub.on. During a measurement period T.sub.m, the radiation-emitting component is switched off after the pulse sequence for an off-time t.sub.off. In this embodiment, the on-time t.sub.on may be understood to be the duration of the pulse sequence. The pulse sequence has a period T.sub.ps which is preferably significantly shorter than the measurement period T.sub.m. For example, T.sub.ps/T.sub.m< 1/10, preferably, T.sub.ps/T.sub.m< 1/100, or even T.sub.ps/T.sub.m< 1/1000. The short-period modulation of the pulsed current I.sub.e(t) of the radiation-emitting component 2 during the on-time t.sub.on is also advantageously ascertainable in the detector signal I.sub.d and is used in particular for reducing the signal-noise ratio. By evaluating the detector signal, for example, non-modulated components of the detector signal which, for example, result via the influence of ambient light, may be filtered out. In this embodiment, the pulse current intensity I.sub.on1, I.sub.on2 is understood to be the amplitude of the pulses of the pulse sequence. In the exemplary embodiment of FIG. 4, the pulse current intensity I.sub.on2 is halved in comparison to I.sub.on1, since the detector signal I.sub.d has exceeded the threshold value during the first measurement period T.sub.m1.

(26) The present invention is not limited by the description based on the exemplary embodiments. Rather, the present invention comprises any new feature and any combination of features, which in particular includes any combination of features in the patent claims, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.