DISTANCE DETECTION SENSOR AND METHOD FOR OPERATING SUCH A SENSOR

Abstract

Distance detection sensor comprising: a current-to-voltage converter configured to convert a current corresponding to a detection signal reflected from a target into a voltage; an amplifier configured to amplify the converted voltage; a comparator configured to compare an output value of the amplifier with a reference value to generate a receive pulse; a reference value selecting means configured to select one of a plurality of reference values as a reference value; a time-to-digital converter configured to calculate a time-of-flight (TOF) duration in response to the receive pulse output by the comparator, and a digital signal processor configured to calculate and store propagation times corresponding to the continuous transmission pulses, wherein the reference value selecting means continuously changes different reference values for each of the continuous reception pulses at a fall time of a previous reception pulse, wherein the digital signal processor calculates a peak time from the runtimes and calculates a distance to the target using the peak time, wherein the digital signal processor calculates the peak point for an input signal using a quadratic function.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to distance sensing sensors and methods of operating such sensors. BACKGROUND

[0002] A distance sensor is a sensor designed to measure a distance to an object. A radiation pulse is radiated onto a target. The distance to the target is calculated based on the time difference between the emission of a radiation pulse and the reception of light reflected from the target (light reception pulse) based on the radiation pulse. This is referred to as a time-of-flight (TOF) scheme. A distance sensor employing a time-of-flight (TOF) scheme is widely used in practice.

[0003] Examples of distance detection sensors are known from US 2018 / 0 259 625 A1, US 2018 / 0 284 286 A1, US 2018 / 0 348 345 A1 and US 5 696 657 A. SUMMARY

[0004] The present disclosure provides a distance detection sensor that minimizes time distortion during distance measurement and a method of operating the distance detection sensor.

[0005] Embodiments of the present disclosure provide a distance detection sensor.The distance detection sensor according to the invention comprises a current-to-voltage converter configured to convert a current corresponding to a detection signal reflected from a target into a voltage, an amplifier configured to amplify the converted voltage, a comparator configured to compare an output value of the amplifier with a reference value to generate a reception pulse, a reference value selector configured to select one of a plurality of reference values as the reference value, a time-to-digital converter configured to calculate a time-of-flight (TOF) duration in response to the reception pulse output by the comparator, and a digital signal processor configured to calculate and store time-of-flight durations corresponding to the continuous transmission pulses, respectively.The reference value selection device continuously changes various reference values for each of the continuous received pulses at the fall time of a previous received pulse. The digital signal processor calculates a peak time from the propagation times and calculates a distance to the target using the peak time. The digital signal processor calculates the peak point for an input signal using a quadratic function.

[0006] In embodiments, the distance detection sensor may further comprise a photosensitive element configured to generate the detection signal.

[0007] In embodiments, the current-voltage converter may comprise a transimpedance amplifier.

[0008] In embodiments, the distance detection sensor may further comprise a capacitor and a resistor connected in parallel between an input terminal and an output terminal of the current-to-voltage converter.

[0009] In embodiments, the time-to-digital converter may comprise a counter configured to count an interval between a transmit pulse and a receive pulse.

[0010] In embodiments, the counter may count an interval from a rise time of the transmit pulse to a rise time of the receive pulse.

[0011] In embodiments, the reference value selecting means may change a reference value at a fall time of a preceding received pulse.

[0012] In embodiments, continuous transmit pulses corresponding to the continuous receive pulses may be transmitted to the target. The number of continuous transmit pulses may be three or more.

[0013] In embodiments, the distance detection sensor may further include a temperature sensor configured to measure a temperature. The digital signal processor may compensate for the distance using the temperature.

[0014] Embodiments of the present disclosure provide a method of operating a distance detection sensor. The operating method includes transmitting continuous transmit pulses to a target, changing a reference value corresponding to each of the transmit pulses, continuously receiving a signal corresponding to each transmit pulse according to the changed reference value, calculating a time-of-flight (TOF) peak time from the received continuous receive pulses, each corresponding to the continuous transmit pulses, using a quadratic function corresponding to the receive signals, and calculating a distance to the target from the time-of-flight peak time. Changing the reference value includes continuously changing the reference value for each of the corresponding continuous receive pulses at a fall time of a previous receive pulse.

[0015] In embodiments, the operating method may further comprise receiving detection signals, each corresponding to the transmission pulses, from a photosensitive element; converting a current corresponding to each of the received detection signals into a voltage; and amplifying the converted voltages.

[0016] In embodiments, the operating method may further comprise measuring a temperature; and compensating the distance according to the measured temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present disclosure will become more apparent from the attached drawings and the accompanying detailed description. The embodiments shown herein are given by way of example only and not by way of limitation, with identical reference numerals referring to identical or similar elements. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating aspects of the present disclosure. Fig. 1 is a block diagram of a distance detection sensor according to embodiments of the present disclosure. Fig. 2 is a timing diagram illustrating a method for detecting a propagation time in a time-to-digital converter according to embodiments of the present disclosure. Fig. 3 illustrates time sequences before and after passing through a comparator according to embodiments of the present disclosure. Fig. 4 illustrates a procedure for calculating a peak time of a detection signal in a digital signal processor according to embodiments of the present disclosure. Fig. 5 illustrates a method of operating a distance sensing sensor according to embodiments of the present disclosure. DETAILED DESCRIPTION

[0018] The advantages and features of the present disclosure, and the methods by which they are achieved, will become apparent from the following exemplary embodiments, which are described in more detail with reference to the accompanying drawings. However, it should be noted that the present disclosure is not limited to the following exemplary embodiments and may be implemented in various forms. Accordingly, the exemplary embodiments are provided merely to disclose the present disclosure and to indicate the category of the present disclosure to those skilled in the art.

[0019] Throughout the description, it should be understood that when an element is referred to as being "on" another layer or substrate, it may be directly on top of the other element, or intervening elements may be present. In the drawings, the thickness of the elements may be exaggerated for clarity of illustration.

[0020] Example embodiments of the invention are described below with reference to cross-sectional views that are example drawings of the invention. The example drawings may be modified by manufacturing techniques and / or manufacturing tolerances. Accordingly, the example embodiments of the invention are not limited to the specific configurations shown in the drawings and include changes based on the method of manufacturing the semiconductor device. For example, an etched region shown at a right angle may be formed in a rounded shape or with a predetermined curvature. Regions shown in the drawings thus have schematic features. The shapes of the regions shown in the drawings illustrate specific shapes of regions in an element and do not limit the invention.Although terms such as a first, a first, a first, a second, a second, a second, and a third, a third, a third are used to describe various elements in various embodiments of the present disclosure, the elements are not limited to these terms. These terms are used merely to distinguish one element from another element. An embodiment described and illustrated herein includes a complementary embodiment thereto.

[0021] The terms used in the description are for the purpose of describing particular embodiments only and are not intended to be limiting of the invention. The singular forms "a", "an" and "the" as used in the description are intended to include the plural forms unless the context clearly indicates otherwise. It is further to be understood that the terms "comprising" and / or "comprising", when used in the description, indicate the presence of stated features, integers, steps, acts, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, acts, elements, components and / or groups thereof.

[0022] The present disclosure will now be described in more detail below with reference to the accompanying drawings in which embodiments of the present disclosure are shown.

[0023] Fig. 1 is a block diagram of a distance detection sensor 100 according to embodiments of the present disclosure. With reference to Fig. 1, the distance detection sensor 100 includes a current-to-voltage converter (TIA) 110, a power amplifier (PGA) 120, a comparator 130, a reference value selector 140, a time-to-digital converter (TDC) 150, a temperature sensor 160, and a digital signal processor (DSP) 170.

[0024] The current-to-voltage converter (TIA) 110 may be configured to convert a current output by a photosensitive element that receives a detection signal (reflected pulse) into a voltage. The photosensitive element may include a photodiode. In embodiments, the current-to-voltage converter 110 may include a transimpedance amplifier (TIA). As shown in Fig. 1, the current-to-voltage converter 110 may include a capacitor C and a resistor R connected in parallel between an input terminal and an output terminal.

[0025] The amplifier (PGA) 120 can be configured to amplify an output voltage of the current-to-voltage converter 110. In embodiments, the amplifier 120 can be a regulated amplifier. The regulated amplifier can be, for example, a programmable operational amplifier (PGA).

[0026] The comparator 130 may be configured to compare an output voltage of the amplifier 120 with a reference value to generate a receive pulse.

[0027] The reference value selector 140 may be configured to select one of a plurality of reference values TH1, TH2, and TH3. In exemplary embodiments, the reference value selector 140 may continuously (or sequentially) select and output the plurality of reference values TH1, TH2, and TH3 based on a predetermined algorithm.

[0028] In exemplary embodiments, the reference value selector 140 may change differential reference values that each correspond to continuous received pulses. The continuous received pulses may correspond to continuously transmitted pulses that are each reflected from a target.

[0029] In some embodiments, the reference value selector 140 may change a reference value in response to a reception pulse output by the comparator 130. In other embodiments, the reference value selector 140 may output the plurality of reference values TH1, TH2, and TH3 at regular time intervals. Even if in Fig. 1 the three reference values TH1, TH2 and TH3 are shown, it should be understood that the number of reference values of the present disclosure should not be interpreted as being limited by the illustrative embodiments.

[0030] The time-to-digital converter (TDC) 150 may be configured to count a time-of-flight (TOF) duration between a transmit pulse and a receive pulse and output a counted value. For example, the time-to-digital converter 150 may be configured to count the time-of-flight duration for a time period from the time a transmit pulse is transmitted by an object until the time an output value is received from the comparator 130. In embodiments, the time-to-digital converter 150 may include a high-speed counter.

[0031] The temperature sensor 160 may be configured to measure a temperature of the distance detection sensor 100.

[0032] The digital signal processor (DSP) 170 may be configured to calculate a distance to an object according to the counted value output by the time-to-digital converter 150. The digital signal processor 170 may also be configured to correct the calculated distance according to the measured temperature from the temperature sensor 160.

[0033] In the internal circuitry of the distance detection sensor 100, a distance detection circuit (TIA / comparator / TDC) can generally be used to measure the time of flight. These circuits encounter the problem of not being able to detect changes in the magnitude of a reflected signal, which is their limitation. Accordingly, when the reflected signal becomes small, timing distortion is caused by a predetermined threshold. This is called skew error, and distance distortion of this magnitude occurs.

[0034] In contrast, according to embodiments of the present disclosure, the distance detection sensor 100 may receive three or more reception pulses from a transmission terminal (not shown), receive reflection pulses corresponding to the transmission pulses, change the reference values TH1, TH2, and TH3 for the received three or more reception pulses for each of the reception pulses, and store a timestamp for each of the changed values TH1, TH2, and TH3. This allows the distance detection sensor 100 to calculate the maximum of a quadratic function and minimize the time offset error by a time value at a calculated pulse peak.

[0035] Fig. 2 is a timing diagram illustrating a method for detecting a propagation time in a time-to-digital converter 150 according to embodiments of the present disclosure.

[0036] The distance detection sensor 100 can convert a sensor signal input as a current signal through the TIA 110 into a voltage signal, amplify the voltage signal using the controlled amplifier 120 for fine signal amplification, compare the amplified signal with a reference value of the comparator 130 to be converted into a high / low signal, and send the converted signal as an input to the time-to-digital converter (TDC) 150. As shown in Fig. 2, a propagation time can be detected as an interval for the transmitted signal. In embodiments, the propagation time can be a value counted by a precise counter. Fig. The propagation time shown in Figure 2 can range from the rise time of an initial pulse to the rise time of an end pulse. The start pulse can be a transmit pulse and the end pulse a receive pulse.

[0037] Fig. 3 illustrates time sequences before and after passing through comparator 300 according to embodiments of the present disclosure. Fig. In particular, Figure 3(a) shows continuous transmit pulses before passing through comparator 130 and corresponding received reflection pulses. The received reflection pulses have a smaller amplitude than the transmit pulses.

[0038] Fig. 3(b) shows receive pulses through continuously selected reference values TH1, TH2, and TH3 after passing through comparator 130. In embodiments, a change time of a reference value may be a fall time of a previous reference value. However, it should be understood that the change time of the reference value should not be interpreted as limited by the illustrative embodiments. The reference values TH1, TH2, and TH3 may be changed, for example, taking into account the time at which transmit pulses are continuously generated.

[0039] Fig. 4 illustrates a procedure for calculating a peak time of a detection signal in a digital signal processor 170 according to embodiments of the present disclosure. With reference to Fig. 4, for a signal output by the comparator 130, ie a received pulse, a quadratic function (y = at 2 + bt + c). A peak point for an input signal can be calculated using the quadratic function, and a time value (t Spitze = -b / 2a) can be calculated using y' = 2at +b (a differential value of the quadratic function).

[0040] An equation of the quadratic function for the input signal is: [abc][t02t12t22t0t1t2111]=[V0 V1 V2]

[0041] In the above equation, V0, V1, and V2 are reference values (TH1, TH2, and TH3, which are Fig. 3). Accordingly, the peak time (tSpitze ) can be expressed by the following equation. tpeak=−b2a=V0(t12−t22)−V1(t02−t22)+V2(t02−t12)V0(t1−t2)−V1(t0−t2)+V2(t0−t1)

[0042] The distance detection sensor 100 according to embodiments of the present disclosure may reduce a distance error to the reduction of a signal amplitude and detect a rising edge during the implementation of the TDC for a reduction of a circuit size, change a reference value using three or more pulses, and store time information for each changed reference value, thereby creating a quadratic function.

[0043] Fig. 5 illustrates a method for operating a distance detection sensor according to embodiments of the present disclosure. With reference to Fig. 1 to 5, the distance detection sensor 100 can be operated as follows.

[0044] Continuous transmission pulses may be transmitted to a target (S110). The pulses reflected from the target, i.e., the detection signals, may be received by a photosensitive element in the distance detection sensor 100. A reference value corresponding to each of the received detection signals may be changed in the reference value selector 140 (S120). The comparator 130 may compare the detection signal received from the photosensitive element with the reference value changed by the reference value selector 140 to output a digital value corresponding to the propagation time (S130). The digital signal processor 170 may calculate the propagation time peak time for the detection signal from the digital propagation time values obtained using the changed reference values (S140). The digital signal processor 170 may calculate / correct a distance to the target using the propagation time peak time and the temperature (S150).

[0045] As one of ordinary skill in the art will appreciate, in other embodiments, steps and / or acts according to the present disclosure may occur for different periods of time or the like, in a different order, or in parallel or concurrently.

[0046] Depending on the embodiments of the present disclosure, some or all of the steps and / or acts may be implemented or otherwise performed, at least in part, using one or more processor flow instructions, one or more programs, one or more interactive data structures, one or more client and / or server components, wherein such instruction(s), program(s), interactive data structure(s), client and / or server components are stored in one or more non-transitory, computer-readable media. The non-transitory, computer-readable medium(s) may be instantiated in software, firmware, hardware, and / or a combination thereof.The functionality of all “modules” explained here can also be implemented in software, firmware, hardware and / or a combination thereof.

[0047] The non-transitory, computer-readable medium(s) and / or means for implementing / executing one or more acts / steps / modules of embodiments of the present disclosure may include, without limitation, application-specific integrated circuits (ASICs), standard integrated circuits, controllers executing corresponding instructions, including microcontrollers and / or embedded controllers, field-programmable gate arrays (FPGAs), complex programmable logic devices (CPLDs), and the like.

[0048] The distance detection sensor 100 according to embodiments of the present disclosure can compensate for the time shift by receiving multiple transmission pulses and establishing reference values that differ from each other when receiving pulses that each correspond to the multiple transmission pulses. The distance detection sensor 100 according to embodiments of the present disclosure can be applied to a light detection and ranging (LIDAR) system for vehicles.

[0049] As described above, a distance detection sensor according to embodiments of the present disclosure may transmit three or more continuous pulses, receive reflected pulses corresponding to the transmitted pulses, change reference values for the three or more received pulses for each received pulse, and store a timestamp for each of the changed values. This allows the distance detection sensor to calculate the maximum of a quadratic function and minimize the time offset error by a time value at a calculated pulse peak.

[0050] Although the present disclosure and its advantages have been described in detail, it is to be understood that numerous modifications, substitutions, and changes may be made without departing from the spirit and scope of the disclosure as defined by the following claims.

Claims

[1] Distance detection sensor comprising: a current-to-voltage converter configured to convert a current corresponding to a detection signal reflected from a target into a voltage; an amplifier configured to amplify the converted voltage; a comparator configured to compare an output value of the amplifier with a reference value to generate a receive pulse; a reference value selecting means configured to select one of a plurality of reference values as a reference value; a time-to-digital converter configured to calculate a time-of-flight (TOF) duration in response to the receive pulse output by the comparator, and a digital signal processor configured to calculate and store propagation times corresponding to the continuous transmission pulses, wherein the reference value selecting means continuously changes different reference values for each of the continuous reception pulses at a fall time of a previous reception pulse, wherein the digital signal processor calculates a peak time from the runtimes and calculates a distance to the target using the peak time, wherein the digital signal processor calculates the peak point for an input signal using a quadratic function. [2] The distance detection sensor according to claim 1, further comprising: a photosensitive element configured to generate the detection signal. [3] The distance detection sensor according to claim 1, wherein the current-voltage converter comprises a transimpedance amplifier. [4] The distance detection sensor according to claim 1, further comprising: a capacitor and a resistor connected in parallel between an input terminal and an output terminal of the current-to-voltage converter. [5] The distance detection sensor according to claim 1, wherein the time-to-digital converter comprises a counter configured to count an interval between a transmission pulse and a reception pulse. [6] The distance detecting sensor according to claim 5, wherein the counter counts an interval from a rise time of the transmission pulse to a rise time of the reception pulse. [7] A distance detecting sensor according to claim 1, wherein said reference value selecting means changes a reference value at a fall timing of a preceding reception pulse. [8] Distance detection sensor according to claim 1, wherein the continuous transmit pulses corresponding to the continuous receive pulses are sent to the target and the number of continuous transmission pulses is three or more. [9] The distance detection sensor according to claim 1, further comprising: a temperature sensor configured to measure a temperature, where the digital signal processor compensates for the distance using the temperature. [10] A method of operating a distance detection sensor, comprising: Sending continuous transmission pulses to a target; Changing a reference value corresponding to each of the transmitted pulses; continuously receiving a signal corresponding to each transmission pulse according to the changed reference value; Calculating a time-of-flight (TOF) peak time from the received continuous receive pulses, each corresponding to the continuous transmit pulses, using a quadratic function corresponding to the received signals; and Calculating a distance to the target from the runtime peak time, wherein changing the reference value includes continuously changing the reference value for each of the corresponding continuous receive pulses at a fall time of a previous receive pulse. [11] The operating method of claim 10, further comprising: Receiving detection signals, each corresponding to the transmission pulses, from a photosensitive element; Converting a current corresponding to each of the received detection signals into a voltage; and Amplifying the converted voltages. [12] The operating method of claim 10, further comprising: measuring a temperature; and Compensate the distance according to the measured temperature.

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