WO2015025014A1

WO2015025014A1 - Interference-compensated device for measuring an optical signal transmission path

Info

Publication number: WO2015025014A1
Application number: PCT/EP2014/067851
Authority: WO
Inventors: Rolf Melcher; Achim Stellberger; Michael Domokos
Original assignee: Elmos Semiconductor Ag
Priority date: 2013-08-22
Filing date: 2014-08-21
Publication date: 2015-02-26

Abstract

The radiation interference-compensated device for measuring an optical signal transmission path is provided with at least one measurement transmitter (H1, H2, H3) and at least one receiver (D) which is exposed to a radiation interference from the surrounding area for example. The device further has an actuating and analyzing unit (17) for actuating the at least one transmitter (H1, H2, H3) and the at least one receiver (D) for the purpose of transmitting or receiving an optical signal during a measurement phase (C) of a measurement interval and for analyzing the received optical measurement signal by processing an electric signal which is present at a first circuit node (61, 62) electrically coupled to the at least one receiver (D). A first radiation interference compensation unit (26, 27, 28, 29), which has a variable internal resistance, is coupled to the at least one first circuit node (61, 62) in order to electrically bias the at least one receiver (D) by providing a first compensation current with a level substantially equaling the level of an interference signal generated as a result of the radiation interference from the at least one receiver (D). The actuating and analyzing unit (17) sets the internal resistance of the at least one first radiation interference compensation unit (26, 27, 28, 29) to a lower first resistance value during a first preparation phase (A) prior to the measurement phase (C) of a measurement interval and to a higher second resistance value during the measurement phase (C).

Description

Störkompensierte device for measuring an optical signal transmission path

Introduction and state of the art

The invention relates to an interference radiation-compensated device for measuring an optical signal transmission path during a plurality of, in particular, intermittently successive measurement intervals, in particular for the detection of an object and / or for the detection of a movement and / or movement device of an object.

Various methods for measuring optical paths are known from the prior art.

In this case, a photodiode is typically operated in the reverse direction. It has proved to be particularly advantageous to energize the photodiode for compensation of a (for example ambient) interference radiation resulting photocurrent by a voltage-controlled current source and to keep it in a voltage predetermined operating point.

A particularly advantageous arrangement for measuring an optical transmission path or for measuring an object which is located within such a transmission path, the measurement using a compensation method, as it is known for example under the name HALIOS ^® . In this case, a compensation transmitter and a transmitter simultaneously radiate superimposed into a receiver. The signal of the compensation transmitter is complementary in time, that is selected to be 180 ° out of phase with that of the transmitter. This means that both signals are superposed at the same Einstrahlamplitude in the receiver signal to a DC signal. A control generates a control signal from the received signal. With this control signal, either the transmitter or the compensation transmitter or, according to a fixed control scheme, both transmitters are regulated. If the regulator's gain is correctly chosen, parasitic influences are eliminated. This concerns above all soiling and drift of the receiver.

Devices of the aforementioned type are described by way of example as EP-A-1 426 783 and DE-B-103 00 223.

It has been found that the use of voltage-controlled current sources for setting a compensation or bias current for photodiodes used as a receiver is particularly advantageous. This is already described, for example, in DE-A-102 56 429. However, other circuits or components for the Störstrahlungs photocurrent compensation can also be used.

A major disadvantage of an operating point adjustment of the above type with the aid of a gyrator is the low input resistance of the gyrator, which loads and attenuates the output signal of the photodiode.

This leads to a reduction in sensitivity. If such a system is used to detect three-dimensional gestures, the range of the system is reduced.

On the other hand, the sensitivity for the measurement signal can be increased. However, this happens at the expense of susceptibility to interference. It is a known problem that, for example, optical gesture recognition systems can be disturbed by fluorescent tubes. Object of the invention

It is therefore the object of the invention to provide an interference radiation compensation device with the possibility of operating point adjustment, in particular for applications in gesture recognition, which does not affect the measurement result and is robust against external disturbances.

To achieve this object, the invention proposes an interference-radiation-compensated device for measuring an optical signal transmission path during a multitude of intermittently successive measurement intervals, in particular for detecting an object and / or for detecting a movement and / or movement device of an object

at least one measuring transmitter for transmitting an optical measuring signal, - at least one receiver for receiving an optical signal, wherein the at least one receiver of an interfering radiation, e.g. from the

Environment is exposed,

a control and evaluation unit for controlling the at least one measuring transmitter and the at least one receiver for transmitting or receiving an optical signal during a measuring phase of a measuring interval and for evaluating the received optical measuring signal by processing an electrical signal electrically connected to a first the circuit node coupled to at least one receiver is present,

at least one first interference radiation unit coupled to the first circuit node for electrically biasing the at least one receiver by providing a first compensation current having a magnitude that is substantially equal to the magnitude of a noise signal generated by the at least one receiver as a result of the interference radiation.

wherein the at least one first interference radiation compensation unit has a variable internal resistance, and

wherein the control and evaluation unit determines the internal resistance of the mini- at least a first interference radiation compensation unit during a first preparation phase before the measurement phase of a measurement interval to a lower first resistance value and during the measurement phase to a higher second resistance value.

The starting point for the considerations that led to the invention is a reduced power or energy consumption of an interference-radiation-compensated device for measuring an optical signal transmission path. The reduced power consumption is particularly advantageous when using such a device in mobile devices, which have only limited energy resources.

When measuring optical signal transmission distances, for example, the approach of an object, contamination or the like. To be able to recognize, there is always the problem that such signal transmission ^¬ distances are "disturbed" by ambient light. The further difficulty is that the interfering signals are much larger than the useful signals. So one would advance not compensate for the disorder, be ^¬ would be the risk of not being able to detect the useful signal within the noise signal easily. One could certainly work with coded payloads, and then by autocorrelation or the like. Correlation method to be able to extract the useful signal from the total signal. However, such systems, which are also known by the term spreading code method, are quite complex in their implementation.

For the interference radiation compensation of optical receivers of devices for measuring optical signal transmission paths, interference radiation compensation units are used which generate a current which is substantially equal to that current or the like in the receiver due to the reception of ambient light. Disturbing light arises. If such a noise-compensated receiver is then subjected to a useful or optical measuring signal, as is required for the measurement of the optical signal transmission track is required, then in the control and evaluation subsequently only this received measurement signal is evaluated.

The interference radiation compensation should be quite stable, so that the device provides reliable evaluations and measurements of the optical signal transmission path. This is basically no problem with permanently activated devices, ie with devices that are basically always ready to measure. However, since such a procedure also requires energy during the periods in which it is not absolutely necessary to measure, such an approach is not suitable for mobile terminals with limited energy resources. Therefore, in the invention, it is decided to keep the device ready for measurement only for individual measuring intervals. In the periods between the measurement intervals, the device then only requires a comparatively low power consumption.

The interference radiation compensation unit is like the control and evaluation unit electrically coupled to the receiver. So that a useful signal received by the receiver can also be received to almost 100% by the control and evaluation unit, the interfering radiation compensation unit should be made relatively high-impedance, so that the electrical signal present at the output of the receiver is only a very small fraction to the interference radiation compensation unit "drains" and thus can be supplied to the predominantly extent of the control and evaluation unit. However, a high-impedance interference radiation compensation unit, that is to say an interference radiation compensation unit with high internal resistance, is disadvantageous insofar as it slows down the operating point setting in advance of the provisioning of the device for the reception of useful signals. Namely, during this phase of the operation of the device, it is desirable for the disturbance radiation compensation unit to have a low internal resistance.

According to the invention, therefore, the internal resistance of the interference radiation compensation unit is now in a preparatory phase, which is before the actual Measurement phase of a measurement interval is set to a low first resistance value, while the internal resistance for the duration of the measurement phase is controlled to a higher second resistance value. By "variable" resistance it is meant in the sense of the invention that the resistor can assume one of more than two different values (impedance, ohmic, capacitive and / or inductive), wherein the resistance values are preferably each non-zero and / or unequal infinity. By "variable" is meant in particular not the case ines fixed pre- or internal resistance, which switches as needed or bridged so "activated" or "deactivated" is.

In the variant of the invention described above, the receiver is connected between ground and a working potential, which is defined by the interference radiation compensation unit. It is furthermore possible and encompassed by the invention that the receiver is connected between two circuit nodes, each of these circuit nodes being connected / coupled to an interference radiation compensation unit, ie the device has two interference radiation compensation units. The useful signal is tapped between these two circuit nodes and processed in the control and evaluation. Such a two-channel embodiment of the device has improved robustness to electrical and / or magnetic far-field interference. The idea is to provide two geometrically and / or electrically substantially identical measurement channels that are exposed to far-field perturbations to substantially the same extent to eliminate the perturbation signals generated by far-field perturbations in a downstream (main) subtractor. If the two sensor elements and / or measuring channels have a known inequality (also called asymmetry), this can be compensated for by a (possibly adjustable) weighting in the difference former, which takes place in particular with regard to a high suppression of electromagnetic noise. In that regard, it is thus expedient if the at least one receiver is connected between a first and a second circuit node with which it is in each case electrically coupled, wherein the at least one first interference radiation compensation unit is coupled to the first circuit node, wherein the and / or between these circuit nodes pending electrical signals of the control and evaluation unit can be supplied and wherein at least one second interference radiation compensation unit with variable internal resistance is present, which provides a second compensation current, which is substantially equal to the first Kompensa- tion current, and wherein the Control and evaluation unit controls the internal resistance of the second interference radiation compensation unit during a measurement interval in substantially the same manner as the internal resistance of the first interference radiation compensation unit. This interconnection of the receiver with two circuit nodes leads to a common-mode suppression of interference radiation.

For further compensation of disturbing influences acting on the device, it is expedient if the receiver alternately receives optical signals which are emitted alternately by the measuring transmitter and by a compensation transmitter. The compensation transmitter radiates directly into the receiver while the transmitter is radiating into the transmission path, the measurement signal being partially reflected in the presence of an object to the receiver. This concept corresponds to the measuring system according to HALIOS ^® .

In such a concept, it can be provided in an advantageous manner that the control and evaluation unit controls the at least one compensation transmitter for sending the optical compensation signal during a second preparation phase of a measurement interval which follows the first preparation phase and precedes the measurement phase, and the control and evaluation unit the internal resistance of the at least one first interference radiation compensation unit and, if present, the at least one second interference radiation compensation unit for the duration the second preparation phase of a measurement interval sets to a resistance value which is equal to the first and / or second resistance value and between these and is greater than during the measurement interval and greater than outside the second preparation phase. In this second preparatory phase, the compensation transmitter preferably transmits continuously, so that the interference radiation compensation unit or units can adjust to this situation in terms of operating point. Also in this second preparation phase, which lies between the first preparation phase and the measurement phase of a measurement interval, the or each interference radiation compensation unit has an internal resistance value which is smaller than during the measurement phase; The interference radiation compensation unit or units thus react again relatively quickly, it remains that they are switched to high impedance, if the actual measurement takes place in the measurement phase.

In an advantageous development of the invention, it can be provided that the at least one measuring transmitter and / or the at least one compensation transmitter transmits / emits modulated optical signals at least during the measuring phase.

In another advantageous embodiment of the invention can be provided that at least portions of the compensation signal complementary, that is. out of phase or 180 ° out of phase with the measurement signal. Furthermore, it is expedient that at least portions of the measurement signal and the compensation signal are superimposed on one another, in particular being added or multiplied by the at least one receiver.

In a further advantageous embodiment of the invention may further be provided that the at least one interference radiation compensation unit is designed as a voltage-controlled current source, as a gyrator, as a variable impedance, as a variable resistor or as a variable inductance. A further variant of the invention relates to a device for measuring an optical signal transmission path intended for the detection of an object during a plurality of intermittently successive measuring intervals, in particular for detecting an object and / or for detecting a movement and / or direction of movement of an object this device is provided with

at least one measuring transmitter for transmitting an optical measuring signal, at least one receiver for receiving an optical signal and a control and evaluation unit for controlling the at least one measuring transmitter and the at least one receiver for transmitting or receiving an optical signal during a measuring phase of a measuring interval and for evaluation the received optical signal by processing an electrical signal present at a first circuit node electrically coupled to the at least one receiver;

wherein the control and evaluation unit detects on the basis of evaluation signals, whether an object is within the signal transmission path or not, and as long as no object is detected within the transmission path, performs the measurement intervals with a low first repetition frequency and

wherein the control and evaluation unit, when an object is detected in the signal transmission path, performs the measurement intervals at a high second repetition frequency. In this case, it can advantageously be provided that the execution of the measurement intervals with the high second repetition frequency from the last non-detection of an object within the signal transmission path is maintained for a predefinable period of time before it is possible to switch to the low first repetition frequency.

Furthermore, the device may be provided with a processor for further processing of the evaluation signals of the control and evaluation unit, wherein the control and evaluation unit evaluation signals that the non-existence of a Represent object, not transmitted to the processor and the processor at least informed about the first-time detection of an object within the signal transmission path. Additionally or alternatively, the processor may cause the drive and evaluation unit to switch the repetition rate of the measurement intervals from the high first repetition frequency to the low second repetition frequency. Furthermore, the operation of the device can be done either in a normal mode or in an energy-saving mode with respect to the normal mode reduced power consumption.

It may be expedient here if the device has a processor for further processing of the evaluation signals of the control and evaluation unit, wherein the processor can initiate or initiate the switchover from the normal mode to the energy-saving mode and vice versa.

Furthermore, the device may have a voltage regulator for various components of the device, the voltage regulator in the energy-saving mode supplying individual components with energy that is reduced in relation to the normal mode, in particular not at all.

Detailed description of the invention

The invention will be explained in more detail using an exemplary embodiment and with reference to the drawing. In detail, FIG. 1 is an overview of the overall system as a block circuit diagram, Fig. FIG. 2 shows the time characteristic of various signals of the overall system according to FIG. 1 during a measuring interval or during a measuring cycle and FIGS. 3 and 4

Diagrams to illustrate a (auto) calibration of the entire system.

A device according to the invention for the interference radiation-compensated control of a photodiode and for the evaluation of the photocurrent has two connections. Between them, the receiving diode D is operated. Via the circuit nodes 61, 62, the receiving diode D is energized by two controlled current sources 27, 28. In this case, two amplifiers 26, 29 detect the potentials on the input lines 30, 31 originating from the connections. If the operating point of the diode changes, for example, by permanent irradiation with sunlight, the generated photocurrent changes. The voltage drop across the receiving diode D changes and the working potentials of the input lines 30, 31 and thus at the inputs of the amplifiers 26, 29. This is registered by the amplifiers 26, 29. These compare the potentials on the input lines 30,31 each with a reference potential Refl, Ref2. The outputs of the amplifiers 26, 29 now regulate the current sources 27, 28 in such a way that the voltage values of the input lines 30, 31 again correspond to the specifications. Coupling capacitors 24, 25 form a barrier to the DC voltage levels on the input lines 30, 31 to downstream circuits. The capacitors 24,25 are connected on the side facing away from the terminals with the inputs to measuring amplifiers 18,19. The outputs 33, 34 of the measuring amplifiers 18, 19 are each fed back via adjustable capacitances 20, 21 to their inputs. A differential stage 35 forms the difference signal 63 of the two amplifier output signals. Ideally, this signal 63 should represent the useful signal of the photodiode. As described above, the control outlined above by the amplifiers 26,29 of the two voltage-controlled current sources 27 and 28 and the change in the setting of the current sources 27,28 leads to a load on the useful signal, which limits the range massively.

The device according to the invention or the method according to the invention is now based on the finding that in most applications, in particular in connection with a gesture control for mobile devices, a permanent measuring operation is not necessary or desirable. Such an operation consumes energy that is extremely "precious" especially for mobile devices, because it is limited in availability.

The device should therefore be time-dependent in different system states, i. H. be operated in individual time-separated and consecutive measurement intervals, each having at least one measurement phase. In this measurement state, the readjustment by the current sources 27,28 practically switched off. Only the capacitors 24,25 hold the respective operating points. This is equivalent to a change in the internal resistance of the current sources 27, 28.

However, such a poor (because "sluggish") control prevents the adaptation to an external light irradiation. It therefore makes sense to define a further state per measurement interval, namely a (measurement) preparation phase in which the internal resistance of the current sources 27, 28 is minimal. In this state, the power sources quickly regulate. A useful signal would be heavily loaded and distorted in the preparation phase. Therefore, no measurement is performed in this preparation phase.

In a sample-and-hold circuit, not shown, the result of the respective measurement is typically buffered. However, a problem that now arises is that a disturbance that occurs during a measurement may over- or underdrive the sense amplifiers 18, 19. Such a disturbed measurement result is not usable. Therefore, it makes sense to quantitatively evaluate the measurement result.

In the simplest case, this can be done, for example, by the measuring amplifiers 18, 19 each outputting one signal for overdrive and one signal for understeer. Thus, 16 states of the system of two amplifiers 18,19 are possible with two evaluation signals. Of these, not all make sense because, for example, a simultaneously occurring over- and understeer is not realistic, but still faulty. Nevertheless, the four-bit word formed in this way forms a quantitative assessment of each measurement result.

In contrast to the prior art, therefore, no transimpedance amplifiers, but integrators, which are part of said measuring amplifiers 18, 19, are used at the input of the system.

The sequence of a measuring interval is controlled, for example, by the digital control block 4 of the (block) circuit diagram according to FIG. Through the sequence control, a measurement activation signal "Measure" (reference number 66, FIG. 2) is activated at the beginning of the measurement (reference number 67, FIG. 2). This starts the first preparation phase A. In this phase A, the current sources 27, 28 regulate the operating point of the receiving diode D at low impedance. The output of the power supply for a compensation diode K is activated. As a result, the compensation diode K already irradiates the photodiode D. The compensation diode K is initially not modulated. Due to the low resistance of the current sources 27,28 the measuring amplifiers 18,19 come quickly to their operating points. The capacitors 20,21 and coupling capacitors 24,25 are charged to their working levels. The current sources 64, 65, 66.67 for the operation of in this embodiment, three measuring transmit diodes Hl, 1-12, 1-13 (because of the multi-dimensional particular 3D Gestestenerken- tion) and the compensation diode K are set to the respective operating values.

At the end of phase A at time 69 (FIG. 2), the signal "hold" (see reference numeral 68, FIG. 2) becomes active. The voltage-controlled current sources 27, 28 go from their hitherto assumed low-impedance state into a high-resistance state. This "frozen" their work points. At this point in time, the difference signal 63 of the outputs of the measuring amplifiers 18, 19 should be constantly zero, since the operating points are adjusted.

Since switching to the high-impedance state also leads to faults, it makes sense to let some time elapse before the actual measurement begins. This time is called stabilization phase or second preparation phase B (Figure 2). It ends at time 70 (FIG. 2).

In the simplest case, the modulation signals 45, 46, 47, 48 for the compensating diode K or for the measuring transmitting diodes H1, 1-12, 1-13 are square-wave signals which are phase-shifted by 180 ° and whose amplitude can be regulated (see Measuring phase C Fig. 2)

The measurement begins by e.g. the radiation of the compensating diode is attenuated or even switched off (see reference numbers 45 and 69 in Figs. 1 and 2). At the same time, typically at least one of the transmit signals (see reference numerals 46 and / or 46 and / or 47 in Figures 1 and 2) is turned on. The typically at least one measuring transmission diode Hl and / or H2 and / or H3 irradiates the (receiving) photodiode D by way of the transmission path to be measured. In the case of several transmitting diodes, these are driven sequentially (for example cyclically).

The compensation transmitting diode K and the typically at least one measuring transmitter diode Hl or H2 or H3 are alternately attenuated or caused to increased radiation. First, this will result in a residual modulation of the output of the input stage. After amplification by an amplifier 36, the thus-received modulated signal can be converted into a DC signal by a demodulator. This can be used to control the amplitude of the modulation of the one Meßsendediode or each one of the transmitting diode Hl, 1-12,1-13 and / or the amplitude of the modulation of the compensation diode K.

In FIG. 2, a control of the compensation diode K is shown by way of example as the case F1 and, as the case F2, a regulation of the measuring transmitter diode or diodes H1, 1-12, 1-13 is shown. The control can be different for the measuring transmitter diodes H1, H2 and H3. Typically, moreover, the measuring transmitter diodes H1, H2 and H3 are not operated simultaneously but with a time delay. In this case, more than one receiving diode can be used. The time offset is typically chosen such that only one receiving diode D and one transmitting diode H1, H2, H3 are active at a time.

In the following, the regulation on the change of the modulation amplitude of the transmitting diode H1, H2, H3 will be explained.

In this case, the measured value obtained in this way regulates the amplitude of the respective measuring transmitter diode H1, H2, H3. It has been shown that it makes sense to increase this value before the negative feedback. This principle is also known from operational amplifier circuits and serves to suppress parasitic factors and influences. For a better understanding, reference is hereby made to the following documents and patent applications, the contents of which, in combination with the technical teaching disclosed here, are part of this application: DE-B-103 46 741, EP-A-2 546 620, EP-A-2 356 000, EP-B-1 410 507, EP-B-1 435 509, EP-A-2 418 512, EP-B-1 269 629, DE-A-103 22 552, DE-B-10 2004 025 345, EP-A-2 405 283, DE-C-44 11 773, WO-A-2012/163725, DE-A-2006 020 579, DE-B-10 2005 045 993, EP-B-1 979 764 DE-A-10 2012 024 778, DE-A-10 2013 000 376, DE10 2013 003 791.3, DEA-10 2013 000 380, WO-A-2014/096385, WO-A-2013/124018, DE-B -10 2013 002 304, EP-A-2 624 019, DE-A-10 2012 025 564, DE 10 2013 002 674.1, DE-A-10 2013 222 936, DE-A-10 2012 015 442, DE-A-10 2012 015 423, DE-B-10 2012 024 597, EP-A-2 679 982, EP-A-2 597 482, DE-A-10 2013 002 676, EP-A-2 653 885.

The regulation ideally sets up an equilibrium and the output signal 50 of the demodulator 37 constitutes, after said amplification, a measure for the attenuation of the transmission signal in the transmission channel. The control according to the invention of the current sources 27, 28 starts at the input lines 30, 31 in FIG an input resistance to the effect that the current sources vary in response to typically at least two phases of a measurement cycle (reference numerals A and C, B and C or A and B and C of Fig. 2).

Of course, the effectiveness of the voltage controlled current sources 27,28 is limited by the real conditions. The current sources 27, 28 can only try to keep the given voltage level up to a maximum current.

The measurement interval (from reference numeral 67, Fig. 2, to reference numeral 71, Fig. 2) is terminated by the fact that the "Measure" signal (66) becomes inactive again at the end of the measuring cycle (see reference numeral 71, Fig. 2). All transmit signals are turned off and the measurement result is typically frozen, for example, in a sample-and-hold circuit (not shown).

Depending on the application, it makes sense to repeat such a measuring interval (from reference numeral 67, FIG. 2, to reference numeral 71, FIG. 2) at regular time intervals in shorter or longer time intervals. However, higher repetition frequencies for the measurement sequences result in a higher current consumption. As a further measure for improving the optical distance measurement, the system may be able to provide at least some and typically each measured value with a quality value of the measurement, that is to perform a measurement signal quality determination. This measure forms part of this application an independent subject of the invention.

Thus, at several successive measurement intervals, a sequence of measurement values with associated quality values results, which allow a measurement value estimator to estimate an optimized measurement value and to indicate a probability of the correctness of this measurement value. The resulting measured value vector can be used, for example, as the basis for the feature extraction of a gesture recognition.

This is particularly useful when a disturber is not relative, such as sunlight, relatively low frequency (for example, due to shading by eg trees), but as in fluorescent tubes or while driving in a convertible in the sunshine under trees relative is modulated quickly. Even if the disturbance frequency is close to the modulation frequency of the measuring transmitting diodes Hl, 1-12, 1-13 and the compensation transmitter K, this frequency is usually not hit correctly. It comes to a beat in the control signal, which can be recognized and used. The quality of the measurement will typically vary with the beat frequency over time. Since the system evaluates only those measured value sequences as a result of the evaluation of the measurement results, which are relatively undisturbed, there is thus de facto automatically to a sampling of the measurement signal only at relatively undisturbed times. In addition, it is conceivable that not only disturbed recognized measured values are discarded, but also those for which an estimator determines a high probability of interference. These can be, for example, directly preceding or directly following measured values. Also, such a measuring system should initiate countermeasures for detected disturbances. This includes, for example, a change in the measurement frequency. This can relate both to the repetition frequency of the measuring intervals and to the modulation frequency of the measuring transmitting diodes H1, 1-12, 1-13 and the compensating transmitting diode K. Also, the circuit can be parameterized differently. For example, the time constants of the measuring amplifiers 18, 19 acting as integrators can be changed by changing the capacitances 20, 21. In extreme cases, the integrators can be bridged by bridging their capacitances 20, 21 with the aid of the programmable switches 22, 23. As you can see from this example, a change in the system or circuit topology is also possible. The integrators then become pure impedance transformers.

A further improvement of the device can thus be achieved by an assessment of the quality of the measurement signal and / or by a control for optimizing the measurement results. In general, the feedback loop is closed by software because the control algorithms are very application dependent.

As an actuator for this measurement signal quality control typically serves a change in the system parameters and / or the system topology or structure.

Another possibility, which can be included in the quality evaluation of a measurement result, is the evaluation of the current source currents. For this purpose, in block 16 ("extrinsic light measurement" or "measurement of the external light"), the current measured by the current source or current sources 27, 28 is measured as a function of time. These measurement results can be made available to the software. This can determine, for example by a Fourier transformation, the interference frequencies that disturb the measurement signal. It is particularly advantageous to select the modulation frequency of the measuring transmitting diodes H1, H2, H3 and the compensation diode K and the repetition frequency of the measuring intervals (reference numeral 67, Fig. 2, to reference numeral 71, Fig. 2) in each case so that they possible with the interference frequencies do not interfere. Thus, for example wise by "frequency hopping" the noise robustness can be raised.

Furthermore, it is conceivable to use a band-limited signal instead of a monofrequency transmission signal and thus to reduce narrow-band interferers by means of a spread-spectra method in their influence on the measurement result. Such possible transmission signals are, for example, suitable pseudo-random sequences (see also EP-A-2 631 674, the content of which is hereby incorporated by reference in the present application)

Another measure representing an independent concept of the invention is the introduction and / or raising of a threshold for detecting the approach of an object to the measuring transmitter diodes Hl, H2, H3 / receiving diode D. This is a nonlinear filter function, which is typically used in the Block 37 of FIG. 1 is realized, but can also be implemented in a subsequent processing stage. All measured values below or above a threshold are fixed to a predefined value, for example. Finally, based on the measurements, a computational model of a jammer can be parameterized and times and setting parameters for the measuring system can be predicted, at which and with which the next measuring interval with a particularly good quality can be performed. Below is a further particularity of the circuit of FIG. 1 will be discussed, in which it is a further independent inventive idea.

Especially for mobile applications, it is particularly important to use as little energy as possible. Therefore, it is particularly favorable, as described above, to modulate the measuring transmitting diodes or one of the measuring transmitting diodes H1, H2, H3 and not the compensation diode K and to operate the system only when required. To further reduce the required operating power, it is It makes sense not to operate the system if it is completely shaded, for example. This is the case when used in a mobile telephone, for example, when the user holds the telephone to his ear for telephoning. For the detection of such usage situations, it is therefore useful to provide another, typically passive sensor, which can pre-classify the usage situation, for example by measuring the ambient light. Again, if necessary, the use of an internal resistance-modulated interference radiation compensation circuit makes sense if modulated signals are to be detected. The circuit according to FIG. 1 has such an interface 53 (see top right in FIG. 1), which is provided with a corresponding input hardware 7.

In addition, it makes sense to put the whole system in a power-saving mode to further reduce energy consumption. It should be noted that modern integrated circuits typically operate internally at a lower voltage than their peripherals. In that regard, a voltage regulator 1 is advantageous, which provides the internal operating voltages. This voltage regulator 1 unnecessarily consumes energy in energy-saving mode. It therefore makes sense to realize the smallest possible part (see function block 14) of the circuit so that it can be operated directly with the operating voltage. This function block 14 has only the task, via an interface 54 to 57 to ensure the minimum communication to the main processor with which the measuring system communicates. The interface has, for example, a serial TX and RX two-wire line or an I ² C bus interface 54, an interrupt output 55 for the main processor, which must be at a defined potential, a non-maskable measuring system reset 56 and a reference voltage input 57. All other systems are switched off. If possible, the normal system oscillator 6 is also switched off and instead this function block 14 of the circuit is supplied with a low frequency from a minimum oscillator 5. This one is much smaller because it does not have to drive the entire IC. Thus, in the power save mode, only the standard blocks 14 and 6 are active. In particular, the band-gap reference 2, the block 4 (digital control), the voltage regulator 1 and all measuring amplifiers and receiving and transmitting devices are switched off.

If the interface 54 is, for example, an I ² C interface, then it makes sense to configure the function block 14 such that it can only recognize a specific command on the bus, which is sent to a precisely specified register address.

Such a protocol can, for example, be such that the function block 14 recognizes a sequence from a start bit and the slave address and from a bit for signaling a write access and then issues an acknowledge bit, whereupon the main processor sends the register address, the function block 14 sends an acknowledge bit and the main processor then sends a parity bit. If the function block 14 has recognized all these data as correct, the voltage regulator, the bandgap reference 2 and all other parts of the circuit are started up in a predefined sequence one after the other and / or in parallel, depending on the type and requirement. The normal I ² C bus communication is then taken over by the block 4 (Digital Control) again until a next sleep command. Upon receipt of such a sleep command, block 4 (Digital Control) causes the essential parts of the measurement system to enter the energy-saving mode. However, the last part of the shutdown sequence must be controlled by function block 14. This particularly relates to the shutdown of the power supply by switching off the voltage regulator 1, the oscillator 6 and the block 4 (Digital Control) itself.

It also makes sense if the function block 14 has an internal timer which can wake up the system at regular intervals, without requiring the reception of a command of the main processor via the interface 54. It may be useful if the system again switches to the energy-saving mode after carrying out measurement intervals predefined in terms of number and type, without requiring a separate command from the main processor via the interface 54 from the outside.

In this case, it makes sense if the measured values and preferably also the measured value qualities are stored in a memory (not shown). The measured values stored there can also include configuration data of the system (for example with which of the transmitting diodes H1, H2, H3, with which the compensating diode K and with which receiving diode D and with which quality measured values were recorded.) The measurement results of further measuring signal evaluation blocks such as For example, block 16 (Extrinsic Light Measurement) may be used, but energy may not be "wasted" in normal measurement mode, so bandgap reference 2, for example, provides only one reference voltage for use at different locations in the measurement system are temporarily turned off when their voltage is latched and buffered in, for example, a sample-and-hold circuit, and the bandgap circuit is then regenerated only for the inevitably slowly draining charges from the memory element of the sample-and-hold circuit (typically a capacitor) of Turned on time after time. Another feature of the invention, which is essential to the invention, results from the necessary calibration of the measuring system.

For this purpose, the control characteristic of the system in regulating the transmitter diode amplitude Tj is shown in FIG. The amplitude of the component attributable to the respective measuring transmitter diode H1, H2, H3 (see 72,75,77 in FIG. 3) of the photocurrent I _PD in the receiving diode D depends on the transmitter diode amplitude T | from. The amplitude of the component attributable to the compensation diode K or the respective compensation diode K (see line 73 in FIG Fig. 3) of the photocurrent I _PD in the / a receiving diode D in contrast depends on the transmitter amplitude T, not from.

When the controller is settled, the difference signal 63 is a Gleichsig-. The proportion attributable to the transmission signal is then zero in the difference signal 63. The maximum distance from which an object approaching the receiving diode or up to which an object removing from the receiving diode can still be recognized is determined by the regulating characteristic and / or the fact that, with the maximum amplitude of the transmitting diode signal, the object still exists such a large proportion of the transmitting diode signal is reflected that at the receiving diode, a signal having at least the amplitude of the compensation diode signal is received. For a large photocurrent 72, which is synonymous with a near object (and thus for a steep control characteristic), this results in the intersection with 73, a first operating point 74. For a lower photocurrent 75 (and thus flatter control characteristics) another second operating point 76. For very distant objects, however, the reflected light can become so low that no working point can arise at all. The control characteristic in the case of the photocurrent 77 is then so flat that there is no intersection with the line 73, which represents the amplitude of the compensation diode K, so that no meaningful control is possible.

There are now two possibilities: Either the Kompensationsdiodensignal is controlled down with such weak receiver signals, which corresponds to a mixed control and has a higher circuit complexity, but can be quite successfully implemented, or to the receiver signal is added to the transmission signal synchronous offset signal, which shifts working points 74, 76 all around the point PO by rotational stretching (see 74 ', 76' in FIG. 4) and creates a new operating point 78 for the new photocurrent 77 '. The offset signal leads to an unreachable area 79 in the diagram of FIG. 4. The generation of this offset signal is shown in FIG. 1 indicated by a calibration block 81, for the respective transmitter / receiver combination of the transmitter signals. 9 12 generates the offset signal 82, from which the signal 82 is generated by addition.

For the calibration of a complete system, which is part of the system described here and forms another independent inventive idea, this entire system is now measured in a defined measurement setup. The overall system differs from the measuring system in that, in addition to the measuring system, it also includes optical elements such as mirrors, diaphragms etc. and, of course, the housing.

For calibration, the compensation diode K is switched to a static level. The coupling between the receiving diode D and the compensation diode K is very difficult to stabilize according to experience. Therefore, the coupling is always the same as an application type, but it is assumed to fluctuate from application to application within the same type.

The calibration is now carried out so that the switchable reference current sources 41,42,43 are provided, with which the reference current supply 38 is now set so that the measured photocurrent is always set to a same, application-specific predetermined value. As a result, the ordinate position of the line 73 in Figs. 3 and 4 are given. This ensures that an operating point is found. This operating point is typically set in such a way that the compensating transmitting diode current is increased until the compensation signal above the system noise becomes measurable. Subsequently, the offset signal is set to such a value that the lowest operating point is assumed.

The essential features of the aforementioned subject matter can be summarized in subgroups as follows:

1. Fremdlichtrobuste device for measuring at least one optical transmission path, characterized in that they has at least one receiver (D) and at least one transmitter (Hl, 1-12,1-13) has and

at least said receiver is connected to at least one gyrator or other interfering radiation compensation unit, and

at least said gyrator at different times has a different internal resistance. Device according to item 1, characterized in that the receiver is a photodiode or another optical receiver which supplies a photocurrent as a signal. Device according to one or more of the preceding figures, characterized in that the measurement is not continuous but in measuring cycles. Device according to item 3, characterized in that at the beginning of at least one measurement cycle, a first preparation phase or similar preparation phase for stabilizing the operating point of the receiver is run through. Device according to item 4, characterized in that during a first preparation phase (A) the at least one gyrator is lower impedance than at a time outside the preparation phase (A). Device according to item 4 or 5, characterized in that

it has at least one compensation transmitter (K) and transmits during a first preparation phase (A) the at least one compensation transmitter (K). Device according to one of the numbers 0 to 6, characterized in that during the at least one measuring cycle following the first Preparation phase (A) a second preparation phase (B) to stabilize a regulator will go through. Device according to item 7, characterized in that during the second preparation phase (B) the at least one gyrator is higher-impedance than at other times, in particular a time outside the second preparation phase (B). Device according to item 7 or 8, characterized in that

it has at least one compensation transmitter (K) and during the second preparation phase (B) the at least one compensation transmitter (K) is transmitted and modulated. Device according to one of the numbers 3 to 9, characterized in that during at least one measuring cycle after the second preparation phase (B) a measuring phase (C) is passed through. Device according to item 10, characterized in that during the measuring phase (C) the at least one gyrator is higher-impedance than at a time outside the measuring phase (C) and the second preparation phase (B) of the measuring interval. Device according to item 10 or 11, characterized in that

it has at least one compensation transmitter (K) and in at least one measurement phase (C) at least one compensation transmitter (K) is transmitted and modulated. Device according to one of the numbers 10 to 12, characterized in that in at least one measuring phase (C) at least one transmitter (Hl, H2, H3) is transmitted and modulated. Device according to one or more of the preceding figures, characterized in that it has at least one compensation transmitter (K) and at least temporarily at least one transmitter (Hl, 1-12, 1-13) and the said compensation transmitter (K) are transmitted and modulated.

Device according to item 14, characterized in that for modulation the at least one compensation transmitter (K) and the at least one transmitter (H) takes place in such a way that at least portions of the compensation transmission signal of said compensation transmitter (K) at least temporarily complementary to the transmission signal of said transmitter (Hl, 1-12,1-13) are. Device according to item 14 and / or l5, characterized in that the radiation of at least the said compensation transmitter (K) and at least of said transmitter (H1, H2, H3) are superposed in the receiver (D) in an additive or multiplying manner. Device according to item 0, characterized in that at least during a period in which at least one transmitter (H1, H2, H3) and said compensation transmitter (K) are transmitted and modulated, at least said compensation transmitter (K) and / or said Transmitter (H) are controlled in the amplitude and / or phase so that the receiver (D) receives no more shares at least a predetermined part of the transmission signal or substantially only during a predetermined measurement phase (C) to system noise and Einregelfehler a DC signal receives. Device according to one or more of the preceding figures, characterized in that an offset signal (82) can be added to the receiver signal which, at least in portions, is at times in phase synchronous with the at least one transmission signal (9, 10, 11) of at least one transmitter (H1, H2 , H3) and corresponds with this. B EZUGSZE IC HEN LIST

voltage regulators

Bandgap reference

function block

Digital Control Block

minimal oscillator

system oscillator

Input Hardware

signal line

function block

Drive / evaluation unit

measuring amplifiers

capacities

switch

coupling capacitors

amplifier

power source

amplifier

input line

output

differential stage amplifier

demodulator

Reference Power

Reference current source

modulation signal

output

interface

RX two-wire cable of the interface

Interrupt output of the interface

Measuring system reset of the interface

Reference voltage input of the interface

circuit node

difference signal

power source

time

photocurrent

Amplitude of the compensation diode representing line

working

photocurrent

working

photocurrent

working 79 area

81 Calibration block

82 offset signal

Hl measuring transmitter diode

H2 measuring transmitter diode

H3 transmitter diode

PO point

Refl reference potential

Ref2 reference potential

A first preparation phase of the measurement interval

B second preparation phase of the measurement interval

C Measurement phase of the measurement interval

D receiving diode

K compensation diode

Claims

claims

1. Störstrahlungskompensierte device for measuring an optical signal transmission path during a plurality of particular intermittently successive measurement intervals, in particular for the detection of an object and / or for the detection of a movement and / or movement device of an object, with

at least one measuring transmitter (Hl, 1-12, 1-13) for transmitting an optical measuring signal,

at least one receiver (D) for receiving an optical signal, wherein the at least one receiver (D) of an interference radiation z. B. is exposed from the environment,

a control and evaluation unit (17) for controlling the at least one measuring transmitter (Hl, 1-12, 1-13) and the at least one receiver (D) for transmitting or receiving an optical signal during a measuring phase (C) of a measuring interval and for evaluating the received optical measurement signal by processing an electrical signal which is present at a first first circuit node (61, 62) electrically coupled to the at least one receiver (D), at least one first interference radiation device coupled to the first circuit node (61, 62) Compensation unit (26,27,28,29) for electrically biasing the at least one receiver (D) by providing a first compensation current having a magnitude substantially equal to the magnitude of a noise generated by the at least one receiver (D) as a result of the noise is

wherein the at least one first interference radiation compensation unit (26, 27, 28, 29) has a variable internal resistance, and

wherein the control and evaluation unit (17) determines the internal resistance of the at least one first interference radiation compensation tion unit (26,27,28,29) during a first preparation phase (A) before the measurement phase (C) of a measurement interval to a lower first resistance value and during the measurement phase (C) to a higher second resistance value.

2. An interference radiation compensated device according to claim 1, characterized in that the at least one receiver (D) between the first circuit node (61,62) and a second circuit node (61,62), with which it is electrically coupled, is connected the at least one first interference compensation unit (26, 27) is coupled to the first circuit node (61), that the electrical signals present at and / or between these circuit nodes (61, 62) can be fed to the control and evaluation unit (17) and that there is at least one second variable internal impedance compensation unit (28, 29) providing a second compensation current substantially equal to the first compensation current, and in that the drive and evaluation unit (17) determines the internal resistance of the second interference radiation Compensation unit (28,29) during a measurement interval in substantially the same manner as the Innenwid the first interference radiation compensation unit (27, 28).

3. Störstrahlungskompensierte device according to claim 1 or 2, characterized in that at least one compensation transmitter (K) for transmitting an optical compensation signal is present to which the at least one receiver (D) is exposed, that the control and evaluation unit (17) the at least a compensating transmitter (K) for sending the optical compensation signal during a subsequent to the first preparation phase (A) and the measuring phase (C) upstream second preparation phase (B) controls a measurement interval and that the control and evaluation unit (17) the internal resistance of the mindes - a first interference radiation compensation unit (26, 27) and, if present, the at least one second interference radiation compensation unit (28, 29) for the duration of the second preparation phase (B) of a measurement interval to a resistance value which is equal to the second resistance value or between the first and the second resistance value and which is greater than during the measurement interval and greater than outside the second preparation phase (B).

Störstrahlungskompensierte device according to one of claims 1 to 3, characterized in that the at least one measuring transmitter (Hl, 1-12,1-13) and / or the at least one compensation transmitter (K) at least during the measuring phase (C) emits modulated optical signals / emit.

An interference-radiation-compensated device according to claim 4, characterized in that at least portions of the compensation signal are complementary, i. E. out of phase or 180 ° out of phase with the measurement signal.

Störstrahlungskompensierte device according to one of claims 3 to 5, characterized in that at least portions of the measurement signal and the compensation signal are superimposed on each other, in particular adding or multiplying received by the at least one receiver (D).

An interference radiation compensated device according to any one of claims 1 to 6, characterized in that the at least one interference radiation compensation unit (26, 27, 28, 29) is a voltage controlled current source, a gyrator, a variable impedance, a variable resistance or is designed as a variable inductance.