DE102009028350A1 - Method for producing coherent electric or electromagnetic modulation signals with definite, relative phase shifts, involves connecting signal outputs with common circuit output in component provided outside integrated circuit - Google Patents

Abstract

The method involves producing a reference signal (A) and input signals (B0-B3) by a same clock signal. Phase shifts are produced by a same phase generator in an integrated circuit (IC2). The input signals are temporally successively provided on a common circuit output (B). The integrated circuit includes a number of signal outputs corresponding to the number of the signals. The signals to be temporally successively switched are temporally distributed. The signal outputs are connected with the circuit output in a component that is provided outside the integrated circuit. An independent claim is also included for a circuit for producing coherent electromagnetic modulation signals with definite, relative phase shifts.

Description

The The present invention relates to a method for generating a plurality coherent electrical or electromagnetic modulation signals with defined, relative phase shifts, with a first Signal has a reference phase position and at least two more Signals are generated which have a different phase position relative to the reference phase, with all signals passing through it Clock signal can be generated and the phase shifts by the same Phase generator can be generated on an integrated circuit wherein the at least two further signals in temporal succession be routed to the same circuit output.

As well The present invention also relates to a circuit for generating a plurality of coherent electromagnetic modulation signals with defined, relative phase shifts, with a clock signal generator and a phase generator operating on an integrated circuit is arranged and several outputs for several Having signals of different relative phase bearings, wherein a first signal at a first output of the phase generator a Has phase position, which serves as a reference phase, and wherein at least two further outputs of the phase generator signals provided which are different from each other relative to the reference phase Have phase position, and with a multiplex circuit, the signals to the at least two further outputs of the phase generator optionally and in succession with a circuit output combines.

Appropriate Methods and devices are needed for modulation of signals or components that - in abstract terms - are direct or after passing through different paths or processes or generation secondary signals again for superimposition or Be brought mixture, wherein the mixed signal is evaluated, in this way conclusions about the different paths or to allow processes or the mixed signal as a useful signal to use and targeted by the different paths or To influence processes.

An example of this is the so-called PMD technology (PMD for photo-mixed detector), which enables an optical 3D measurement and acquisition of objects on the transit time principle. A PMD pixel, like conventional photo- or radiation-sensitive detectors, is formed on a semiconductor, however, unlike conventional pixels known from the semiconductor chips of digital photo or film cameras, each has two read-out memory areas (due to the nature of their manufacture) referred to as "read diffusions"). These readout memory areas are applied, preferably in push-pull, with a first modulation signal. This means that the two gates assume different potentials over time and tend to pick up or repel the charge carriers generated in the surrounding semiconductor material, depending on the instantaneous potential. Such a method is described, for example, in US Pat German Patent Application No. 197 04 496 A1 ,

at constant illumination of a corresponding pixel or a corresponding one Pixel arrays and a temporal integration of the readout memory areas derived currents or charges over a measuring time, which is significantly larger than the period of the modulation signals is, results between the read memory areas of a pixel a difference of 0 in the number of times recorded by the two gates Charges.

If However, the lighting is modulated with a frequency that too is coherent with the modulation signal (where the term "coherence" is here is used in the sense of a phase-locked coupling), results however, at the readout memory areas of a pixel, a difference in the number of charge carriers generated by the radiation, after integration into a non-zero difference signal leads. The difference signal is a measure of the relative phase angle between the modulation signal at the gates and the intensity modulated incident on the pixel radiation

at Accordingly, the PMD method becomes a 3D scene by an intensity-modulated light source illuminated (more generally by an intensity modulated subjected to electromagnetic radiation). For a complete 3D image is reflected (modulated) by the 3D scene Light on an imaging optics on an array of so-called Led PMD pixels that are similar to other optical Sensors made of a light- or radiation-sensitive semiconductor material are formed. The peculiarity of PMD pixels is, as already illustrates that each pixel has two readout memory areas has and that these two readout memory areas in push-pull with a modulation signal to be applied.

The modulation of the illumination now takes place with the same modulation signal as the modulation of the two read-out memory areas (or with a coherent modulation signal). The relative phase position between the modulation signal and the reflected and received by a pixel array, intensity-modulated light signals is a measure of the transit time difference of the modulated light signal and directly the Auslesespeicherberei che the pixel acting first modulation signal. This phase difference, in turn, is due to the distance of the object from which the radiation was reflected from the pixel in question, it being understood without loss of generality that the modulated light source is located immediately adjacent to the pixel or pixel array.

This Phase difference is again detected by the different Charge amounts due to the simultaneous modulation of the readout memory areas and the received radiation at the two readout memory areas. Specifically, the charge differences at the readout memory areas or the currents or voltages derived therefrom, if the phase difference between the read-out memory areas acting modulation signal and the intensity modulation the incident radiation is 0 ° or 180 ° and minimum or equal to zero, if the phase difference of these signals 90 ° or 270 °. The difference the charges at the readout memory areas is thus a directly convertible Measure the relative phase angle between the received, modulated (and reflected) light signal and the modulation signal, with to which the readout memory areas of the pixel are applied

Around to clearly detect the relative phase, must be a measurement with at least two different relative phase angles. For example, a first modulation signal with which the light source output is modulated, relative to the modulation signal the readout memory areas have a phase angle of 0 °, while a second modulation signal for the Light source relative to a phase shift of 90 ° having the modulation signal of the readout memory areas. In the Practice often uses four different modulations Lighting with phase angles of 0 °, 90 °, 180 ° and 270 ° relative to the reference phase, due to the modulation signal the read-only memory is defined because you can do it that way also possible asymmetries between the two read memory areas better able to compensate, which in itself is proportionate to each other because of the push-pull modulation also a phase shift of 180 °.

To more accurate determination of the relative phase angle of the pixel received light signal can over the wavelength the intensity modulation this phase immediately the duration of the light signal and thus the distance of the modulated with the Light illuminated object or object point to the pixel determined become.

slight Deviations in the relative phases between the first modulation signal, which serves as a reference, and the signals modulating the illumination corresponding setpoints therefore have an immediate effect Error in the distance determination of the object and thus as Errors in the three-dimensional rendering of an object.

to Reduction of error sources and reduction of the control and control effort in practice become the various modulation signals from a single clock source and a single phase generator generated. The different phase-shifted modulation signals, which are necessary for the uniqueness of the phase determination must be used one after the other to evaluate the results of both Compare and evaluate measurements.

To The prior art is on the integrated circuit, the includes a phase generator for generating the phase-shifted signals, Also, a corresponding multiplexer arranged over a likewise integrated output driver each one of the different light modulation signals to a power output for controlling the to be modulated Light source gives.

In front all in view of the ongoing integration of electronic Components on integrated circuits, there is always the danger a crosstalk or some repercussions and interactions of different signals, especially when a device such as the output driver of the multiplexer integrated on the same Circuit (short: IC) is arranged, which is a sufficiently stable Provide signal for driving the light source to be modulated should. Basically, such interactions are as long as they can be accurately recorded or unchanged during operation not a significant problem, but they can lead to significant errors and thus become problematic if the repercussions on other signals of the integrated Circuit vary in time.

In the present example, the phase generator of the integrated circuit on the one hand provides a signal for modulation of the read-out memory area, which is referred to here for better distinction as a reference signal. On the other hand, such a phase generator has at least two further output signals which have a different phase position relative to the phase of the reference signal. A power component arranged on the integrated circuit, such as the output driver of a multiplexer, may in this case due to the interactions with the other components of the integrated circuit, in particular with The outputs of the phase generator, not only cause a slightly different from their nominal values phase shift, but it can also affect the reference signal in particular depending on which of the other two modulation signals is switched to the output of the multiplexer in different ways. This influence can in particular consist in the fact that the "duty cycle" or the duty cycle is influenced in different ways when the read-out memory areas are acted upon. That is, during one modulation cycle, one read-out memory area is held at a potential attractive to the charges for a longer time than the other, which conversely remains longer at a repulsive potential during each modulation cycle. Even if these differences in the duty cycle are relatively small, but results in the readout memory areas even at constant illumination or even at a relative phase shift of 90 ° between the reference signal and the incident, modulated light, a difference in the amounts of charge at the two read memory areas since due to the different duty cycle, more charges tend to be shifted to one read-out storage area than the other.

Also this would be by appropriate evaluation without further notice subsequently correctable, if one uses the modulated light source as the only source of light. This is only below Laboratory conditions, but not in most practical applications realizable. Rather, in practice by far the largest Part of the charge carriers in the semiconductor material through incident radiation or light are generated by the environment or Generates background light that hits the pixels. there can be the part of the charge carriers, which by the background light be generated, without further 100 to 1000 times that by the intensity-modulated light generated charge carriers be. As a result, the actual measurand, namely the difference between the number of electrical charge carriers, due to the phase position of the intensity-modulated Light relative to the phase of the modulation of the readout memory areas is caused, another difference superimposed, alone by the background light due to the different Duty cycle and the modulation of the two read memory areas is caused.

If now this difference caused by the background light Charge quantities at the two read memory areas even of it depends on which of the phase-shifted light modulation signals is present at the power output of the respective multiplexer, so leaves The influence of the background light is not easy anymore Correct and leads directly to falsification the determination of the phase of the modulated light signal relative to Reference signal. This will also remove the respective object or object point incorrect and inaccurate.

Also in other applications, the interactions of on the circuit of the phase generator integrated components, especially if they are partly power components, to malfunctions and influences on the various Modulation signals or the reference signal lead, the to adversely affect the intended use of these signals. The example of the PMD technology was just an example here chosen because in this process the corresponding make negative influences particularly noticeable.

Across from The prior art explained above is the present invention Invention, the object of a method and a circuit to create with the above characteristics which ensure that the reference signal and the further modulation signals remain completely unaffected by which of the Modulation signals via a multiplexer to a circuit output is placed.

Regarding of the method, this object is achieved in that the the integrated circuit comprising the phase generator one of Number of signals has corresponding number of signal outputs, the temporal distribution of the temporally successive aufzuschaltenden Signals and the connection of the signal outputs with the common circuit output on a component that is outside of the phase generator having provided, integrated circuit is provided.

Regarding The above circuit is the basis of the invention Problem solved by that of the phase generator having integrated circuit corresponding to the number of signals Number of signal outputs, where the multiplexing circuit and their output driver for the common power output for the time-sequentially aufzuschaltenden, phase-shifted Signals are arranged on a component outside of the phase generator having integrated circuit is provided.

The fact that the multiplexer and its output driver are arranged on a different circuit than the phase generator, takes place virtually no feedback and no crosstalk from the multiplexer and its output driver to the phase generator and the different signals remain completely unaffected in their phase position, which of the concrete Signals over the Multiplexer is placed on the circuit output, which in turn modulates the transmitter or the light source.

Conveniently, has each of the outputs of the phase generator having integrated circuit has its own output driver, the each connected to an input of the multiplexer. Even though these output drivers do not need to be power devices, is an influence and an interaction of these output drivers with the other components and thus also an influence of this Output driver to the reference signal is not complete excluded. However, this influence remains temporal constant, regardless of which one of the integrated Circuit leaving signals outside this circuit switched by the following multiplexer and its signal output becomes. Such, temporally constant influence on the reference signal can be easily determined by appropriate calibration measurements correct.

In a variant of the method is provided that in operation all Signals at the same time at the outputs of the phase generator to be provided. This avoids any change in the Operating state of the IC concerned, if by an outside Each of the multiplexers located on the IC has a different one of the signals the common circuit output is switched.

In In one embodiment, each of the signal outputs of the phase generator with one on the same integrated circuit arranged and individually assigned output driver connected is. This ensures even better decoupling of the individual from the inputs of the multiplexer or its output driver.

Farther can output drivers with a corresponding number of inputs of the multiplex circuit (permanently) connected be. One thus avoids time varying conditions on or in the integrated circuit containing the phase generator.

In In a preferred variant, the phase generator has at least in total four outputs for at least four output signals different phase up. One of the outputs can be simultaneously serve as an output for the reference signal. For However, the reference signal can also have its own additional Signal output be provided, even if the phase of one of the other Output signals coincides with the phase of the reference signal. The same applies to any other number of output signals.

It it is understood that the inventive method and the corresponding circuit not just on the case of PMD measurements are restricted, but rather everywhere are applicable where multiple coherent, d. H. phase-locked coupled signals are needed when applying any load experience any change at the signal output or other, affect simultaneously generated by the same phase generator signals could.

Further Advantages, features and applications of the present Invention will become apparent from the following description of a preferred embodiment and the associated Characters. Show it:

1 schematically five coherent signals, each with different phase shifts with respect to the reference phase of the first of these signals,

2 FIG. 2 schematically shows a signal course in a PMD system with four modulated exposures of different phase positions carried out immediately one after the other, wherein only the signal modulation is shown here. FIG.

3 a circuit for generating the signals after the 1 and 2 according to the prior art and

4 an inventively modified circuit for generating the signals of 1 and 2 ,

One recognizes in 1 a first square-wave signal A whose phase position is referred to as the reference phase. Furthermore, coherent signals B0 to B3 can be seen, all of which have exactly the same principal course in the form of a rectangular signal with the same frequency, but which have different phase shifts relative to the reference phase A. The signal B0 has the same phase as the signal A (phase shift 0), the signal B1 is 90 ° out of phase with the signal A, the signal B2 is 180 ° out of phase with the signal A and finally the signal B3 is offset by 270 ° shifted the signal A.

In the case of a PMD measurement, the readout memory areas of a PMD pixel are in push-pull applied to the signal A, for example, one can imagine the signal A as a modulation voltage between two terminals, one with the one readout memory area and the other with the other readout memory area connected is. The potential at both read memory areas then follows exactly the course of the signal A, but in one of the readout memory area shifted by 180 ° relative to the other read-out memory area. However, even a slight shift of the duty cycle between the two read memory areas can not be excluded.

Then For example, a scene with a laser, z. B. a laser diode, illuminated, and the reflected light is received by the PMD pixel. As long as the lighting is not modulated, the integration results The charges at both readout storage areas are generally accurate the same charge quantities, so that the difference in the two Readout memory areas generated charges is 0. in case of a different duty cycle is a constant Difference, which could be subtracted from later measurement results.

Becomes but then the illumination intensity modulates with a coherent to modulating the read-only memory areas Frequency, this results depending on the relative phase position of the modulated, At the PMD pixels incoming light different amounts of charge at the two read memory areas. This difference can be in be converted into a phase position and from the relative phase of Lighting to the reference phase can turn on the life of the modulated light from the light source to the object and back to be calculated to the PMD pixel.

For the uniqueness of the phase position are two different measurements required at different relative phase angles, so that the Measurement immediately after a modulation in the lighting with the signal B0, now under modulation with the signal B1 takes place. To further accuracy in determining the phase position In addition, even more measurements can be made be performed with the modulation signals B2 and B3. The detection of an object point or its removal from the PMD pixel thus takes place by four immediately consecutive Exposures with modulated light in each case different Phasing relative to the reference phase.

3 shows a corresponding circuit according to the prior art, with which the signals A to B3 are generated conventionally. A phase generator is arranged together with a multiplexer and two output amplifiers on a common, integrated circuit IC. The phase generator receives an external or internal clock, which serves as the basis for generating all the signals A to B3. Internally, the phase generator generates five different signals, namely the signal A, with which the PMD pixel or pixels are modulated, and the signals B0, B1, B2 and B3, which are applied to four inputs of a corresponding multiplexer. The multiplexer successively selects one of the signals B 0, B 1, B 2 and B 3, in turn, to apply to an output amplifier at the output of the multiplexer, this output amplifier in turn modulating the light source (eg an LED) by means of which a Scene is illuminated. The multiplexer operates in such a way that in total the waveform according to 2 results.

However, it may happen that the outputs of the phase generator are connected directly to the inputs of the multiplexer, which in turn has an output driver, that the reference signal A as well as the relative phase position and the duty cycle of a signal with respect to the reference phase A also by the others, in the immediate Near adjacent other reference signals B0 to B3 or the associated output driver is affected. Thus, the signal A or B does not exactly the in 2 but with respect to one or more of the modulation signals B0, B1, B2 and B3 still has some not exactly determined and for the different signals unequal additional phase shift and / or an asymmetric duty cycle on. This distorts the results in determining the relative phase angle between modulated illumination and the reference signal A with which the PMD pixels are modulated.

In 4 the circuit according to the invention is shown. PMD pixels, lighting and clock generator can be identical to the corresponding components of the circuit 3 be. However, the multiplexer is now not shared with the phase generator on an integrated circuit but the phase generator having signal outputs has four output drivers V0 to V3 whose signal outputs correspond to the signals B0, B1, B2 and B3. The multiplexer is in turn arranged on a further integrated circuit IC2 and can now place the preamplified input signals B0, B1, B2 and B3 optionally on the common circuit output B, with the aid of which the illumination is modulated. Since the phase generator is separated from the input of the multiplexer by the output drivers and the signals applied to the output drivers remain unchanged over time, there is no effect on the phase position of the individual signals B0 to B3 and also not on the phase and the phase Duty cycle of the reference signal A, approximately in dependence on which the signals B0 to B3 are placed by the multiplexer on the common circuit output B. Even if some repercussions should not be avoidable, they would be constant at least over time and could therefore be easily corrected.

This can ideally just the exposure state according to 2 be realized with four different output phases, and the accuracy of the phase measurement and thus in the case of a PMD transit time measurement and the distance determination of an object is thus significantly improved.

For Purpose of the original disclosure is pointed out that all features, as they result from the present Description, the drawings and the dependent claims for a specialist, even if they specifically described only in connection with certain other features were, both individually and in any compilations can be combined with other features or feature groups disclosed herein unless expressly excluded or technical conditions such combinations impossible or make pointless. On the comprehensive, explicit representation of all conceivable feature combinations and the emphasis on independence the individual characteristics of each other will be here only for brevity and omitted for the sake of readability of the description.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 19704496 A1 [0004]

Claims (7)

A method for generating a plurality of coherent electromagnetic modulation signals having defined, relative phase shifts, wherein a first signal has a reference phase position and at least two further signals are generated which have a different relative phase to the reference phase, all signals are generated by the same clock signal and the phase shifts through the same phase generator are generated on an integrated circuit, wherein the at least two further signals are passed in succession to the same circuit output, characterized ; in that the integrated circuit having the phase generator has a number of signal outputs corresponding to the number of signals, the time distribution of the signals to be successively switched on and the connection of the signal outputs to the common circuit output being made on a component which is provided outside of the integrated circuit having the phase generator is. Method according to claim 1, characterized in that that during operation all signals are simultaneously at the outputs the phase generator are provided. Method according to claim 1 or 2, characterized that at least 4 output signals are different from each other Be provided phases. Circuit for generating a plurality of coherent electromagnetic Modulation signals with defined, relative phase shifts, with a clock generator and a phase generator operating on an integrated circuit is arranged and the several outputs for several signals of different relative phase position having a first signal at a first output of the phase generator has a phase position which serves as a reference phase, and at least two further outputs of the phase generator signals provided which are mutually different relative to this reference phase Have phase position, and with a multiplex circuit, which signals optionally at the other outputs of the phase generator and connecting in time to a circuit output, characterized in that having the phase generator integrated circuit at least one of the number of different Signals has corresponding number of signal outputs, where the multiplex circuit and the common circuit output for the phase-shifted signals which can be successively switched on one after the other are arranged on a component outside of the Provided phase generator having integrated circuit is. Circuit according to Claim 4, characterized that each of the signal outputs of the phase generator with each one arranged on the same integrated circuit and individually assigned output driver is connected. Circuit according to Claim 5, characterized that the output driver with a corresponding number of inputs the multiplex circuit are connected Circuit according to one of claims 4 to 6, characterized in that the phase generator in total at least four outputs for at least four output signals has different phase.

Images