DE102017202957A1 - Receiver arrangement, semiconductor device and method for receiving light pulses and for outputting a received signal - Google Patents

Abstract

A receiver arrangement having at least one photosensitive element (LE) for receiving light pulses (LI) and outputting a reception signal (E) used for object detection is proposed. The receiver arrangement has a drive (A) which activates the at least one light-sensitive element (LE) in such a way that the photosensitivity of the at least one photosensitive element (LE) is increased within a predetermined measuring cycle, wherein the light sensitivity of the at least one photosensitive element (LE) is increased in dependence on a derived output signal of the at least one light-sensitive element (LE), the received signal (E) is generated. Furthermore, a semiconductor device is proposed with a substrate on which the receiver arrangement is arranged. A corresponding method for receiving light pulses and outputting a received signal (E) used for object detection is also proposed.

Description

The invention relates to a receiver arrangement, a semiconductor module or a method for receiving light pulses and for outputting a received signal according to the preamble of the independent claims.

Out US 9,285,464 B2 It is known that a so-called LiDAR device can be used for vehicle environment monitoring.

In contrast, the inventive receiver arrangement or the semiconductor device according to the invention or the inventive method for receiving light pulses and for outputting a received signal with the features of the independent claims has the advantage that, according to the invention, an electronic dynamic extension for the receiver arrangement is achieved. This is achieved in particular by the fact that the at least one photosensitive element is driven by a control such that in a given measuring cycle, the photosensitivity of the at least one photosensitive element is increased, wherein in response to a derived output of the at least one photosensitive element, the received signal is generated , The invention takes into account that at the beginning of a measuring cycle the expected received light energy is greater than at the end of the measuring cycle. This energy will decrease in particular in the ratio 1: r ² with the assumption that a so-called Lambert reflector is present as an object. The measure according to the invention of increasing the sensitivity in one measuring cycle has the effect that the number of photosensitive elements can be reduced in comparison with the state in which the invention is not used. Less photosensitive elements also means that the receiver arrangement is cheaper and in particular smaller.

Another advantage is that a better detection of objects is possible, because not so many photosensitive elements are necessary, which may possibly cause saturation of the amplitude signal. In the amplitude information of the received signal, however, there is information about the object itself. Thus, this information is retained.

It is furthermore advantageous that a semiconductor component is present which has the receiver arrangement according to the invention on a substrate. For a compact and cost-effective production in particular in the so-called CMOS technology is possible. In a development it can be provided that, in addition, the transmitting device, i. the semiconductor laser and its control and further processing steps of the received signal can be arranged on this semiconductor device.

The inventive method for receiving light pulses and for outputting a received signal can lead to the same advantages, regardless of the configuration of the receiver arrangement. In particular, if parts of the receiver arrangement are implemented by software.

In the present case, a receiver arrangement means a hardware and / or software embodiment of a receiver arrangement which is capable of receiving light pulses with a photosensitive element and outputting a corresponding received signal used for object detection. Such a receiver arrangement can be produced, for example, as a semiconductor chip, preferably made of silicon and / or other semiconductors. All possible combinations of semiconductor components on different substrates or other electronic components are also possible.

A photosensitive element is, for example and also preferably, a so-called photosensitive avalanche diode (APD), which in a further embodiment can be designed as a so-called single photon avalanche photodiode (SPAD), that is, can be designed for a sensitivity of a single photon. Usually, however, the threshold is set higher for the detection of a light pulse, since background noise can be used to receive individual photons which are not correlated with the emitted light pulses. Several such APDs or SPADs can be combined to form a so-called silicon photomultiplier, in which the SPADs are interconnected in one field. Depending on the application, individual photosensitive elements, ie individual SPADs, can be driven in appropriate expectation, but all SPADs of a silicon photomultiplier (SIPM) can also be controlled. These SPADs are connected in parallel, so that a summation signal of the individual SPADs is used as the output signal of the silicon photomultiplier.

In the present case, light pulses which are emitted by a laser arrangement and reflected by a possible object are received in the present case. These light pulses are emitted, for example, with a transit time of 1.33 μs, since this corresponds to a distance of 200 m. This would be the usual time for a measurement cycle to be assumed.

SPAD cells as the photosensitive elements are arranged in a matrix for a SIPM as stated above. Each SPAD has Cell four possible states: Loaded, this is the state in which the diode waits for a photon or a so-called dark count event. This time is much greater than the time to be recharged. The second state is the so-called firing. Due to the received photons an avalanche effect is triggered and the current increases abruptly. This condition is much smaller than 1 ns. The next state is the so-called quenching. The avalanche effect is throttled and ultimately stopped, for example by a resistance. Again, this happens in a time that is much less than 1 ns. This quenching is necessary to prevent self-destruction of the photodiode. Quenching with a resistor, which is most commonly used, is called passive quenching. There are even more complicated embodiments, which are then called accordingly. The last and fourth state is the so-called recharge. This will prepare the SPAD cell for the next firing. This takes about 10 to 50 ns with today's technology. The SPAD cells ultimately fired a binary output signal or did not fire. The dynamics are determined by the frequency of the firing, and in these re-applications the effective dynamic bandwidth is 1 bit.

The SPAD cells are biased by a so-called bias voltage V_Bias. This voltage is greater than the breakdown voltage. The minimum voltage is approximately 1V above the breakdown voltage, and on the basis of this bias has a linear influence on the sensitivity. Currently, the bias upwards is usually limited to 5V, since a further increase would lead to diode destruction.

The received signal is the output signal of the receiver arrangement which is used by further signal processing to detect and also characterize the objects in the environment.

The drive is an electrical configuration, which is realized for example on a semiconductor substrate and increases the photosensitivity of the at least one photosensitive element. This can be achieved, for example, by a corresponding sawtooth circuit, since the same starting value is started in each measuring cycle. Alternatively or embodying this, an integrator circuit can be used. It may also be that it does not always start with the same starting value, for example, to investigate certain distance ranges.

The photosensitivity is defined such that for a given light output, a corresponding output signal of the photodiode is achieved as an example.

The derived output signal of the at least one photosensitive element can be directly a voltage which is tapped via a resistor at the output, for example by SPAD. However, it may also be a filtered signal, a converted signal from a raw signal from the photodiode.

In the present case, the object detection can be carried out, for example, using the measuring principle TCSPC (time-correlated single phonon counting). This measuring method, known in German as time-correlated photon counting, is a technique for measuring temporally rapidly changing light intensities. In this case, a measurement is repeated many times and the individual temporally correlated photons in relation to the excitation pulse are sorted according to their measured time in a so-called TCSPC histogram. This typically has a temporal channel resolution or class width of 0.1 to 1 ns and represents the time course of the backscattered by a laser pulse light. In time-correlated photon counting, individual photons of the light pulses are detected and counted and entered into a histogram at which point, seen in terms of time, the photon or photons occur. The emission of the light pulse and the count are repeated many times. This achieves a very accurate time measurement of the laser pulse. For example. An object is hit by a transmitter with many photons, which are then received by the receiver array. Due to the frequent repetition of this photon determination, it is possible to precisely determine the light pulse with respect to its time of flight. For example, an analog-to-digital conversion can be used and in particular the measured photon times are entered into a histogram in a memory and then at the end by a logic the maximum is determined.

Another measurement method for object detection is the so-called TDC (time-to-digital converter, time-to-digital conversion). This is a device for detecting states and providing a digital representation of the time that has occurred. For example, a TDC may output the arrival time for each incoming pulse. In particular, the time interval between two pulses is determined with a TDC. In this case, the measurement can be started and stopped when a rising or falling edge of a signal pulse exceeds a corresponding threshold. A time-to-digital conversion is a method for determining a time between, for example, two pulses and converting them into a digital word. This can, for example, a counter are used, which is activated by a start and a stop signal, for example, the received light pulse or the emitted light pulse. In order to determine the error at the beginning and at the end of the count determined by the counter, a so-called interpolation is used. For this purpose, a delay circuit can be used. However, it is also possible to use two mutually detuned oscillators or to use a so-called oversampling, for example, a quadruple oversampling and thus to sample the signal. By the count and the values obtained from the interpolation at the beginning of the count and at the end of the count, then the time and thus the flight time can be measured accurately.

A substrate is understood to mean a semiconductor wafer on which the electronic components have been produced in one piece. This is a very cost effective method of manufacture which results in very small dimensions of the electronic components.

Advantageous embodiments of the receiver arrangement according to the invention or of the semiconductor module according to the invention or of the method according to the invention for receiving light pulses and for outputting a received signal are possible as a result of the developments and measures listed in the dependent claims.

It is particularly advantageous that the increase in sensitivity takes place step by step. This is very easy to control and also electronically easy to represent how the sensitivity is increased.

Furthermore, it is advantageous that the drive for increasing the photosensitivity increases an electrical bias for the at least one photosensitive element. This bias voltage, as denoted by V_Bias above, is a simple parameter which can be easily produced, for example, by a sawtooth circuit, but also by other circuits which can generate a time-varying signal.

Moreover, it is advantageous that the at least one photosensitive element is a photosensitive avalanche diode, wherein a plurality of photosensitive avalanche diodes form a silicon photomultiplier. These are the elements that have already been defined above for the photosensitive element, namely the SPADs and the matrix or just one row of SPADs that form a SIPM, ie the silicon photomultiplier.

In addition, it is advantageous for the derived output signal of the at least one photosensitive element to be compared with a threshold value of a threshold value transmitter and, depending on this comparison, for the received signal to be generated by at least one comparator, the threshold value being lowered by the threshold value during the measuring cycle. It should be noted here that this threshold is used to allow only those signals to pass through the comparator generated by a certain number of photons. However, since the power of the light decreases, it is expedient to further develop the invention in such a way that in addition to the sensitivity even lower this threshold. This can be achieved by a threshold generator, which also generates a time-dependent output signal. This can be achieved by software technology or hardware. The comparator or discriminator can also be discretely integrated or manufactured by software. As an example according to the invention, the threshold value can start, for example, at 25 photons and drop to 5 photons. This is represented by the output signals of the individual photodiodes. That it is known what number of photons lead to which output signal.

It is advantageous that the increase of the photosensitivity and the lowering of the threshold value occur at different time intervals during the measuring cycle. This means that, for example, the photosensitivity is increased in a first time segment and the threshold value is lowered in a subsequent second section and then the photosensitivity is increased again in a third section and then the threshold value is lowered again in a fourth subsection. For this purpose, any variations are possible, so that an overlap is possible or even a parallel increase in the photosensitivity or lowering of the threshold value.

Furthermore, it is very advantageous that the derived output signal of the at least one photosensitive element is fed directly to an analog-digital converter device, wherein the digital output signal of the analog-to-digital converter device is the received signal. In this solution, so you waived the aforementioned comparator and therefore here is also a lowering of a threshold not possible and necessary. Here only the photosensitivity is increased. The analog-digital converter device must be correspondingly fast in order to generate the received signal.

Furthermore, it is advantageous that the receiver arrangement has a delay device which delays the beginning of the measurement cycle. Usually, the measurement cycle is started by outputting the light pulse via, for example, a laser or a laser array. However, each measurement cycle can be delayed to evaluate only a certain distance relative to objects. For example, a delay of 0.66 μs can be provided to measure targeted in a distance range of 100 to 200 m distance to the receiver assembly.

In the following description and the drawings embodiments of the invention are shown and described.

• 1 ein erstes Blockschaltbild der Erfindung,
• 2 ein Flussdiagramm der Erfindung,
• 3 ein zweites Blockschaltbild der Erfindung,
• 4 ein drittes Blockschaltbild der Erfindung,
• 5 ein Ersatzschaltbild eines lichtempfindlichen Elements als SPAD,
• 6 ein erstes Spannungszeitdiagramm,
• 7 ein erstes Schwellwertzeitdiagramm,
• 8 ein erstes Zeitablaufdiagramm,
• 9 ein zweites Zeitablaufdiagramm,
• 10 ein zweites Spannungszeitdiagramm,
• 11 ein kombiniertes Spannungsschwellwertzeitdiagramm.

Show it:

• 1 a first block diagram of the invention,
• 2 a flowchart of the invention,
• 3 a second block diagram of the invention,
• 4 a third block diagram of the invention,
• 5 an equivalent circuit diagram of a photosensitive element as SPAD,
• 6 a first voltage time diagram,
• 7 a first threshold time diagram,
• 8th a first timing diagram,
• 9 a second timing diagram,
• 10 a second voltage time diagram,
• 11 a combined voltage threshold time diagram.

1 shows a first block diagram of the invention. This is controlled by a control A via a drive signal 10 a photosensitive element LE to increase its photosensitivity within a measurement cycle. The light pulses strike the photosensitive element LI , As an output signal of the photosensitive element LE becomes the received signal e output.

2 shows a flowchart of the method according to the invention. In the process step 200 be through the photosensitive element LE the light pulses LI receive. During the measuring cycle is in the process step 201 through the control A the photosensitivity of the photosensitive element LE by means of the signal 10 elevated. This increase can be gradual linear or nonlinear. It can remain constant for certain sections and then be increased again. In the process step 202 is from the photosensitive element LE the derived output signal is output. This signal can be filtered, amplified and converted to another size. From the derived output signal is in the process step 203 generates the received signal. The received signal can correspond directly to the derived output signal or it can be further processed.

3 shows a further block diagram of the receiver arrangement according to the invention. Here is also a transmission arrangement shown. By means of a pulse generator 300 becomes a laser 301 for the output of light pulses 302 on an exemplary object 303 causes. These light pulses are at least partially reflected 314 and strike the photosensitive element 304 , For example, a matrix of different SPADs, which together form a silicon photomultiplier. There is the photosensitive element 304 via the control 305 controlled by the bias voltage V_Bias. According to the invention, the bias voltage V_Bias is increased in one measurement cycle. This can be linear, stepwise or nonlinear. The derived output signal 309 the photosensitive element 304 or the silicon photomultiplier becomes an amplifier 308 fed. The output signal of the amplifier 308 goes to a comparator 311 , which is a threshold from a threshold 310 is compared. The threshold 310 is through a ramp generator 307 affected. The threshold 310 may be in particular a digital-to-analog converter. The ramp generator 307 continues to influence another digital-to-analog converter 306 that's the trigger 305 for the photosensitive element 304 controls. The ramp generator 307 is in turn with the pulse generator 300 connected to start with the emission of the laser pulse and the measurement cycle in the receiver assembly.

The output signal of the comparator 311 . 315 becomes an object detection 312 which operates, for example, using the TDC method. In doing so, the signal represents 315 the received signal. The signal 313 then represents the distance measurement.

4 shows a third block diagram of the invention. The pulse generator 400 triggers the laser 401 for the output of the laser pulses 402 that are on the object 403 to meet. The reflected laser pulses 404 hit the photosensitive element 405 that's about driving 406 with the bias voltage V_Bias is applied. The control 406 is via a digital-to-analog converter 408 that of a ramp generator 409 is acted upon. Again the ramp generator becomes 409 from the pulse generator 400 started. The derived output signal 407 becomes the amplifier 410 fed and the amplified output signal 410 the fast analog-to-digital converter 411 whose output signal 413 represents the received signal. This is then done by object detection 412 evaluated with another evaluation method, such as the method TCSPC, to perform the distance measurement.

5 shows in an equivalent circuit diagram a photosensitive element, which is designed as SPAD. The bias voltage V_Bias goes through a resistor R_Bias on a reverse-biased SPAD connected to ground via a load resistor R_Load. Between the SPAD and the load resistor R_Load the output signal 50 is tapped.

6 shows in a voltage time diagram possible changes in the bias voltage V_Bias during a measurement cycle. The measuring cycle lasts from t ₁ to t ₂ . The voltage is increased from 1V to 5V. This can be done, for example, linearly with the curve 60, or stepwise 61 or also in sections, as shown by 62.

7 shows the lowering of the threshold THR in a threshold time chart. The threshold value is lowered from the value max to the value min in the time interval between t ₁ and t ₂ . This can also be linear with the reference numeral 70 designates or stepwise designated by the reference numeral 71. Also, another non-linear lowering, which is not shown here, possible.

In 8th It is shown that the lowering of the thresholds THR and the increase of the bias voltage V_Bias can be sequential. Here, first the threshold value THR is lowered and then the bias voltage V_Bias is increased, then the threshold value THR is lowered again and then the bias voltage V_Bias is increased again.

9 shows, however, that this can also be done overlapping by first the bias voltage V_Bias is increased, then overlapping the threshold value THR is lowered and then again overlapping the bias voltage V_Bias is lowered.

10 shows another voltage timing diagram, after which the increase of the bias voltage V_Bias with a time delay .DELTA.t ₁ after the start t ₁ takes place. Thus, the increase takes place only in the section Δt ₂ , for example, to evaluate only a certain distance section.

11 shows a combined Spannungsschwellwertzeitdiagramm, in which first at the time t _1, the measuring cycle starts and the bias voltage of V_min is increased to 2V gradually. From the time t ₃ , the voltage 2V is initially maintained until the time t ₄ , to then increase again in other steps from the time t ₄ to t ₅ to the maximum value V_max. Accordingly, the maximum value of the threshold value THR_max is held at the time t ₁ and lowered stepwise until the time t ₃ until the time t ₄ . Then, this intermediate value is held from the time t ₄ to the time t ₅ , in order then to lower it again until the time t ₂ to the minimum value THR_min.

LIST OF REFERENCE NUMBERS

A

control

LE

photosensitive element

LI

light pulse

e

receive signal

10

control signal

200

reception

201

Increase in sensitivity

202

Derivative output signal

203

Generation of received signal

300

pulse generator

301

laser

302

light pulses

303

object

304

photosensitive element

305

control

306

Digital to analog converter

307

ramp generator

308

amplifier

309

derived output signal

310

threshold generator

311

comparator

312

object detection

313

signal

314

reflected light pulses

315

receive signal

400

pulse generator

401

laser

402

laser pulses

403

object

404

reflected laser pulses

405

photosensitive element

406

control

407

derived output signal

408

Digital to analog converter

409

ramp generator

410

amplifier

411

Analog to digital converter

412

object detection

413

output

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 9285464 B2 [0002]

Claims (10)

A receiver arrangement comprising at least one photosensitive element (LE) for receiving light pulses (LI) and outputting a reception signal (E) used for object detection, characterized in that the receiver arrangement comprises a drive (A) comprising the at least one photosensitive element (LE) controls such that in a given measurement cycle, the photosensitivity of the at least one photosensitive element (LE) is increased, wherein in response to a derived output signal of the at least one photosensitive element (LE), the received signal (E) is generated. Receiver arrangement according to Claim 1 , characterized in that the increase is gradual. Receiver arrangement according to Claim 1 or 2 characterized in that the photosensitivity enhancement increases an electrical bias (V_Bias) for the at least one photosensitive element (LE). Receiver arrangement according to Claim 3 characterized in that the at least one photosensitive element (LE) is a photosensitive avalanche diode (SPAD), wherein a plurality of avalanche photosensitive avalanche diodes (SPAD) form a silicon photomultiplier (SIPM). Receiver arrangement according to one of the preceding claims, characterized in that the derived output signal of the at least one photosensitive element (LE) is compared with a threshold value (THR) of a threshold value generator and, as a function of this comparison, the received signal (E) is generated by at least one comparator, wherein the threshold (THR) is lowered by the threshold during the measurement cycle. Receiver arrangement according to Claim 5 , characterized in that the increase of the photosensitivity and the lowering of the threshold value take place at different time intervals during the measuring cycle. Receiver arrangement according to one of Claims 1 to 4 , characterized in that the derived output signal of the at least one photosensitive element (LE) is supplied to an analogue-to-digital converter device, the digital output signal of the analogue-digital converter device being the received signal (E). Receiver arrangement according to one of the preceding claims, characterized in that the receiver arrangement comprises a delay device which delays the beginning of the measurement cycle. Semiconductor device with a substrate on which the receiver assembly according to claims 1 to 8 is arranged. Method for receiving light pulses for outputting a received signal (E) used for object detection, characterized in that a photosensitivity of at least one photosensitive element is increased in a given measuring cycle and in dependence on a derived output signal of the at least one photosensitive element (LE ) the received signal is generated.

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