TWI765675B - Ranging system - Google Patents

Abstract

A ranging system includes: a source generating a wideband incident wave that is transmitted toward a target and that is reflected by the target to form a reflected wave; a feedback detector to detect the reflected wave to generate a detected signal; an operator configured to perform low-pass filtering on the detected signal at an adjustable filtering bandwidth to generate a filtered signal, and calculate cross-correlation of a feedback signal that originates from the filtered signal and a reference signal that corresponds to the incident wave to generate a cross-correlation result; and a controller calculating a distance to the target based on an operation output that originates from the cross-correlation result.

Description

ranging system

The present invention relates to a ranging technology, in particular to a ranging system.

A lidar system is a system that measures a distance from the lidar system to the target by illuminating a target with laser light and measuring the time of flight required for the laser light to return to the lidar system. The lidar system can detect the target when the target is within a ranging dynamic range of the lidar system.

In a lidar system, a higher sampling frequency results in a better ranging resolution; and a total number of samples is limited by a given power budget, so a higher sampling frequency results in a narrower ranging dynamic range . Therefore, given a power budget, the sampling frequency can be reduced to achieve a wider ranging dynamic range for which the ranging resolution is traded off, but this may result in a loss of target (ie, the target is not detected). Furthermore, fine ranging resolution and wide ranging dynamic range cannot be achieved simultaneously without excessive power consumption.

Accordingly, it is an object of the present invention to provide a ranging system which, when the adjustable parameters in the ranging system are properly set, ameliorates at least one of the disadvantages of the prior art.

Therefore, the ranging system of the present invention is suitable for measuring a distance from the ranging system to a target, and includes a source end, a feedback detector, an arithmetic unit and a controller. The source end generates a broadband incident wave. The incident wave is transmitted towards the target and is reflected by the target to form a reflected wave. The feedback detector is used for detecting the reflected wave to generate a detection signal. The arithmetic unit is electrically connected to the feedback detector to receive the detection signal therefrom, and is set to perform low-pass filtering on the detection signal under an adjustable preset filter bandwidth, so as to generate a filtered signal, and calculate the source Cross-correlation between a feedback signal from the filtered signal and a reference signal corresponding to the incident wave to generate a cross-correlation result. The controller is electrically connected to the operator to receive an operation output from the cross-correlation result therefrom, and calculates the distance from the ranging system to the target according to the operation output.

1: Ranging system

11: Source

12: Feedback detector

13: Reference detector

14: Operator

141: Low pass filter

142: Sampler

143: Cross-correlator

144: Analog to Digital Converter

145: low pass filter

146: Decimator

15: Controller

2: target

Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, wherein: FIG. 1 is a block diagram illustrating a first embodiment of a ranging system of the present invention; FIG. 2 is an example Explain that under different conditions of different preset filter bandwidths, the Figure 3 is a diagram illustrating the cross-correlation results of the first embodiment under different conditions with different preset sampling frequencies; Figure 4 is an example illustrating a Figure 5 is a block diagram illustrating a second embodiment of the ranging system according to the present invention; Figure 6 is a block diagram illustrating the A third embodiment of the ranging system of the present invention; FIG. 7 is a block diagram illustrating a fourth embodiment of the ranging system according to the present invention; FIG. 8 is a block diagram illustrating the ranging system according to the present invention and FIG. 9 is a block diagram illustrating a sixth embodiment of the ranging system according to the present invention.

Before the present invention is described in detail, it should be noted that in the following description, similar elements are designated by the same reference numerals.

Referring to FIG. 1, a first embodiment of a ranging system 1 of the present invention is suitable for measuring a distance from the ranging system to a target 2, and includes a source end 11, a feedback detector 12, and a reference detector 13, an arithmetic unit 14 and a controller 15.

The source end 11 generates a broadband incident wave (eg, light, electromagnetic wave or sound), and can be modulated or not modulated according to application requirements. the incident The wave is transmitted to the target 2 and is reflected by the target 2 to form a reflected wave.

The feedback detector 12 is used for detecting the reflected wave to generate a first detection signal.

The reference detector 13 is used to detect the incident wave to generate a second detection signal.

In this embodiment, the source end 11 is a light source end (eg, a laser) that generates light as the incident wave, and each of the feedback detector 12 and the reference detector 13 is a photoelectric converter A device (eg, a photodiode), which converts the corresponding one of the reflected wave and the incident wave into an electrical signal as the corresponding one of the first detection signal and the second detection signal. However, the present invention is not limited to the above embodiments.

The arithmetic unit 14 is electrically connected to the feedback detector 12 and the reference detector 13 to receive the first detection signal and the second detection signal from the feedback detector 12 and the reference detector 13 respectively, and is used for executing The following actions: perform low-pass filtering on the first detection signal and the second detection signal at an adjustable preset filter bandwidth, so as to generate a first filter signal and a second filter signal respectively; A preset sampling frequency is used to sample the first filtered signal and the second filtered signal, so as to generate an echo derived from the first filtered signal and the second filtered signal and corresponding to the reflected wave and the incident wave, respectively the feedback signal and a reference signal; and calculating the cross-correlation of the feedback signal and the reference signal corresponding to a plurality of delay times distributed in a predetermined time zone to generate a cross-correlation result, wherein the predetermined time zone is possible optionally adjusted.

The controller 15 is electrically connected to the arithmetic unit 14 to control the adjustable parameters in the arithmetic unit 14 (including the preset filter bandwidth, the preset sampling frequency and the preset time zone), and is used to obtain data from the arithmetic unit 14 receives an operation output derived from the cross-correlation result, and calculates the distance from the ranging system 1 to the target 2 according to the operation output.

In this embodiment, both the first detection signal and the second detection signal are analog signals; and the arithmetic unit 14 includes a low-pass filter 141 , a sampler 142 and a cross-correlator operating in the analog domain 143, and also includes an analog digitizer 144.

The low-pass filter 141 has an adjustable filter bandwidth, is electrically connected to the controller 15, and is controlled by the controller 15 in a manner that the adjustable filter bandwidth is set to the preset filter bandwidth. The low-pass filter 141 is also electrically connected to the feedback detector 12 and the reference detector 13 to receive the first detection signal and the second detection signal from the feedback detector 12 and the reference detector 13, respectively, and Perform low-pass filtering on the first detection signal and the second detection signal at the preset filter bandwidth to generate the first filtered signal and the second filtered signal, respectively.

The sampler 142 has an adjustable sampling frequency, is electrically connected to the controller 15, and is controlled by the controller 15 in a manner that the adjustable sampling frequency is set to the preset sampling frequency. The sampler 142 is also electrically connected to the low-pass filter 141 to receive the first filtered signal and the second filtered signal from the low-pass filter 141, and the first filtered signal and the second filtered signal at the preset sampling frequency The two filtered signals are sampled to generate the feedback signal and the reference signal, respectively.

The cross-correlator 143 has an adjustable time zone, is electrically connected to the controller 15, and is controlled by the controller 15 in a manner that the adjustable time zone is set as the preset time zone. The cross-correlator 143 is also electrically connected to the sampler 142 to receive the feedback signal and the reference signal from the sampler 142, and calculate the feedback signal and the reference signal corresponding to the distribution in the predetermined time zone The cross-correlation of equal delay time is generated to generate the cross-correlation result as the output of the operation. Specifically, for each delay time, the cross-correlator 143 delays the reference signal by the delay time to generate a delay signal, and calculates the dot product of the feedback signal and the delay signal. The equal dot products respectively corresponding to the delay times together constitute the cross-correlation result.

The analog-to-digital converter 144 is electrically connected to the cross-correlator 143 to receive the operational output from the cross-correlator 143, and is also electrically connected to the controller 15, and performs analog-to-digital conversion of the operational output to generate a digital representation of the Compute the output to provide the controller to receive. The controller 15 calculates the distance from the ranging system 1 to the target 2 according to the operation output represented by the digital number.

In a first implementation of this embodiment, the controller 15 controls the low-pass filter 141 and the sampler 142 so that the predetermined filtering bandwidth is narrower than a signal bandwidth of the incident wave, and the predetermined filtering bandwidth is narrower than a signal bandwidth of the incident wave. The sampling frequency is higher than the preset filter bandwidth.

FIG. 2 illustrates the simulation cross-correlation results of the present embodiment under various conditions. Under all conditions, the signal bandwidth of the incident wave is 500MHz and the preset sampling frequency is 5GHz, and the preset filter bandwidth is Under various conditions, respectively, no Infinity, 100MHz, 50MHz, 25MHz and 10MHz. Under each condition, the delay time corresponding to the maximum dot product is the actual delay time of the reflected wave of the ranging system 1 corresponding to the incident wave. It can be reasonably determined from FIG. 2 that the lower the preset filter bandwidth, the wider a pulse of the cross-correlation result including the maximum dot product. In addition, as shown in FIG. 3, when the preset sampling frequency is higher than the preset filter bandwidth, the cross-correlation result (ie, the combination of the solid dots and the hollow dots) does not lose the above-mentioned pulse, thus ensuring target detection ( That is, target 2 has been detected); and when the preset sampling frequency is lower than the preset filter bandwidth, the cross-correlation result (that is, the solid dots) may completely lose the above-mentioned pulses that should have appeared, Causes the target to be lost (ie, the target 2 is not detected). In a first implementation of this embodiment, by making the preset filtering bandwidth lower than the preset sampling frequency, even if the preset sampling frequency is reduced in order to widen a ranging dynamic range of the ranging system 1 , the target 2 will still be detected.

Referring to FIG. 1 and FIG. 4 , in a second implementation of this embodiment, the ranging system 1 operates in the coarse mode and the fine mode in sequence. In the coarse mode, the controller 15 controls the low-pass filter 141 , the sampler 142 and the cross-correlator 143 so that the preset filtering bandwidth, the preset sampling frequency and the preset time zone are respectively equal to one A first filtering bandwidth, a first sampling frequency and a first time zone, the first filtering bandwidth is narrower than the signal bandwidth of the incident electromagnetic signal, and the first sampling frequency is higher than the first filtering bandwidth. Furthermore, the controller 15 obtains a rough delay time of the reflected wave of the ranging system 1 corresponding to the incident wave according to the operation output. In fine mode, the The controller 15 controls the low-pass filter 141, the sampler 142 and the cross-correlator 143 so that the preset filter bandwidth, the preset sampling frequency and the preset time zone are respectively equal to a second filter bandwidth, a second sampling frequency and a second time zone. The second filter bandwidth is wider than the first filter bandwidth. The second sampling frequency is higher than the second filtering bandwidth and the first sampling frequency. As shown in FIG. 4, the second time zone is narrower than the first time zone and approximately equal to the rough delay time. Furthermore, the controller 15 obtains a fine delay time of the reflected wave of the ranging system 1 corresponding to the incident wave according to the operation output, and calculates the distance from the ranging system 1 to the target 2 according to the fine delay time. distance.

In the second implementation of this embodiment, because the preset sampling frequency in the fine mode is higher than the preset sampling frequency in the coarse mode, and the preset time range in the fine mode is narrower than the The preset time range in the coarse mode, so the ranging system 1 has a wider dynamic range in the coarse mode, and a better ranging resolution in the fine mode. In addition, the predetermined sampling frequency and the predetermined time zone in both coarse mode and fine mode can be such that a total number of samples (ie, the dot product) included in the cross-correlation result does not exceed a predetermined power budget Therefore, the ranging system 1 can have an overall fine ranging resolution in a wide ranging dynamic range without excessive power consumption.

Referring to FIG. 5, a second embodiment of the ranging system 1 of the present invention is similar to the first embodiment, but differs from the first embodiment in that the cross-correlator 143 operates in the digital domain .

In the second embodiment, the analog-to-digital converter 144 is electrically connected to the sampler 142 to receive the feedback signal and the reference signal from the sampler 142, and perform analog-to-digital conversion on the feedback signal and the reference signal , to generate a digital representation of the feedback signal and a digital representation of the reference signal. The cross-correlator 143 is electrically connected to the analog-to-digital converter 144 to receive the digital representation of the feedback signal and the digital representation of the reference signal from the analog-to-digital converter 144 , and is also electrically connected to the controller 15 . The cross-correlator 143 calculates the cross-correlation of the digital representation of the feedback signal and the digital representation of the reference signal corresponding to the delay times distributed in the predetermined time zone to generate the cross-correlation as the operation output The result is received by the controller 15 to provide. The controller 15 calculates the distance from the ranging system 1 to the target 2 according to the arithmetic output.

Referring to FIG. 6, a third embodiment of the ranging system 1 of the present invention is similar to the first embodiment, but differs from the first embodiment in that: (a) the reference detector is omitted 13 (see FIG. 1); (b) the controller 15 also generates a source signal of an analog signal; (c) the source terminal 11 is electrically connected to the controller 15 to receive the source signal from the controller 15, and according to the source signal generating the incident wave; and (d) the low-pass filter 141 for receiving the source signal from the controller 15 and performing low-pass filtering on the source signal at the preset filter bandwidth to generate the first Second filtered signal.

Referring to FIG. 7, a fourth embodiment of the ranging system 1 of the present invention is similar to the second embodiment, but differs from the second embodiment in that: (a) the reference detector is omitted 13 (see Figure 5); (b) the controller 15 also generates a digital source (c) the source terminal 11 is electrically connected to the controller 15 to receive the source signal from the controller 15 and generate the incident wave according to the source signal; and (d) the arithmetic unit 14 is further included in the digital domain Another low-pass filter 145 and a decimator 146 operate in .

In the fourth embodiment, the second filtered signal is generated by the low-pass filter 145 instead of the low-pass filter 141 , and the reference signal is generated by the decimator 146 Not produced by the sampler 142 . Specifically, the low-pass filter 145 has an adjustable filter bandwidth, is electrically connected to the controller 15, and is controlled by the controller 15, so that the adjustable filter bandwidth is set to the preset filter bandwidth. The low-pass filter 145 is used for receiving the source signal from the controller 15, and performing low-pass filtering on the source signal at the preset filter bandwidth to generate the second filtered signal. The decimator 146 has an adjustable sampling frequency, is electrically connected to the controller 15, and is controlled by the controller 15, so that the adjustable sampling frequency is set to the preset sampling frequency. The decimator 146 is also electrically connected to the low-pass filter 145 and the cross-correlator 143 for receiving the second filtered signal from the low-pass filter 145 and down-sampling the second filtered signal to generate a The reference signal with a sampling rate equal to the predetermined sampling frequency is provided for reception by the cross-correlator 143 . The cross-correlator 143 calculates the cross-correlation of the digital representation of the feedback signal and the reference signal corresponding to the delay times distributed in the predetermined time zone to generate the cross-correlation result.

Referring to FIG. 8 , a fifth embodiment of the ranging system 1 of the present invention is similar to the first embodiment, but differs from the first embodiment in that the arithmetic unit 14 for performing the following actions: performing low-pass filtering on the first detection signal and the second detection signal under the preset filter bandwidth, to respectively generate the first filtered signal as the feedback signal and the reference signal, respectively with the second filtered signal; calculating the cross-correlation of the feedback signal and the reference signal corresponding to the delay times distributed in the preset time range to generate the cross-correlation result; and at the preset sampling frequency The cross-correlation result is sampled below to produce the output of the operation.

In the fifth embodiment, the cross-correlator 143 is electrically connected to the low-pass filter 141 to receive the feedback signal and the reference signal from the low-pass filter 141, and calculates the feedback signal corresponding to the reference signal and the cross-correlation to the delay times distributed in the predetermined time zone to generate the cross-correlation result. The sampler 142 is electrically connected to the cross-correlator 143 to receive the cross-correlation result from the cross-correlator 143 and sample the cross-correlation result at the preset sampling frequency to generate the operation output. The analog-to-digital converter 144 is electrically connected to the sampler 142 to receive the operational output from the sampler 142 and performs an analog-to-digital conversion of the operational output to generate a digital representation of the operational output for the controller 15 to receive. The controller 15 calculates the distance from the ranging system 1 to the target 2 according to the digital representation of the operation output.

Referring to FIG. 9, a sixth embodiment of the ranging system 1 of the present invention is similar to the fifth embodiment, but differs from the fifth embodiment in that: (a) the reference detector is omitted 13 (see FIG. 8 ); (b) the controller 15 also generates a source signal of an analog signal; (c) the source terminal 11 is electrically connected to the controller 15 to receive from the controller 15 the source signal, and the incident wave is generated according to the source signal; and (d) the low-pass filter 141 is used for receiving the source signal from the controller 15, and performs low-pass filter on the source signal under the preset filter bandwidth pass filtering to generate the reference signal.

In the above description, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiments. It will be apparent, however, to one skilled in the art that one or more other embodiments may be practiced without these specific details. It should be understood that throughout the specification references to "one embodiment", "an embodiment", an embodiment ordinal, etc., mean that a particular feature, structure or characteristic may be included in the practice of the invention. It will also be appreciated that, in this specification, various features are sometimes grouped together in a single embodiment, drawing or description thereof to simplify the invention and to assist in understanding various aspects of the invention, and one or more features may be In the practice of the invention, specific details of one embodiment may be practiced together with one or more features or specific details of another embodiment.

However, the above are only examples of the present invention, and should not limit the scope of implementation of the present invention. Any simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the contents of the patent specification are still included in the scope of the present invention. within the scope of the invention patent.

1: Ranging system

11: Source

12: Feedback detector

13: Reference detector

14: Operator

141: Low pass filter

142: Sampler

143: Cross-correlator

144: Analog to Digital Converter

15: Controller

2: target

Claims (12)

A ranging system suitable for measuring a distance from the ranging system to a target, and comprising: a source end for generating a broadband incident wave, the incident wave is transmitted to the target, and is reflected by the target to A reflected wave is formed; a feedback detector is used to detect the reflected wave to generate a first detection signal; an arithmetic unit is electrically connected to the feedback detector to receive the first detection signal therefrom and used for Low-pass filtering is performed on the first detection signal at an adjustable preset filter bandwidth to generate a first filtered signal, and a feedback signal derived from the first filtered signal and corresponding to the incident wave are calculated a cross-correlation between a reference signal of a The operational output calculates the distance from the ranging system to the target. The ranging system of claim 1, wherein the operator calculates the cross-correlation corresponding to a plurality of delay times distributed in an adjustable preset time zone. The ranging system as claimed in claim 1, wherein: the operator is further configured to pair with an adjustable preset sampling frequency The first filtered signal is sampled to generate the feedback signal; and the cross-correlation result is output as the operation. The ranging system according to claim 3, wherein the preset sampling frequency is higher than the preset filtering bandwidth. The ranging system as claimed in claim 3 can be operated in a coarse mode and a fine mode, wherein: in the coarse mode, the controller sets the preset filtering bandwidth and the preset sampling frequency respectively equal to a first The arithmetic unit is controlled by means of a filtering bandwidth and a first sampling frequency; and in the fine mode, the controller controls the arithmetic unit so that the predetermined filtering bandwidth and the predetermined sampling frequency are respectively equal to a first sampling frequency. The arithmetic unit is controlled by means of two filtering bandwidths and a second sampling frequency, wherein the second filtering bandwidth is wider than the first filtering bandwidth, and the second sampling frequency is higher than the first sampling frequency. The ranging system of claim 5, wherein: the operator calculates the cross-correlation corresponding to a plurality of delay times distributed in an adjustable preset time zone; in the coarse mode, the controller calculates the The operator is controlled in such a way that the preset time zone is equal to a first time zone, and according to the calculation output, a rough delay time of the reflected wave corresponding to the incident wave in the ranging system is obtained; and in the fine mode , the controller sets the preset time zone equal to a The arithmetic unit is controlled in the manner of the second time zone, and according to the arithmetic output, a fine delay time of the reflected wave corresponding to the incident wave in the ranging system is obtained, and according to the fine delay time, the distance from the ranging system is calculated. The distance of the system to the target, the second time zone is narrower than the first time zone and is approximately the rough delay time. The ranging system of claim 3, further comprising a reference detector for detecting the incident wave so as to generate a second detection signal, wherein: the operator is also electrically connected to the reference detector to receive detection from the reference The second detection signal of the filter is also used to perform low-pass filtering on the second detection signal at the preset filter bandwidth, so as to generate a second filter signal, and the second filter at the preset sampling frequency. The signal is sampled to generate the reference signal. The ranging system according to claim 3, wherein: the source end is used for receiving a source signal, and generating the incident wave according to the source signal; and the arithmetic unit is further used for receiving the source signal, and is also used for Low-pass filtering is performed on the source signal at the predetermined filtering bandwidth to generate a second filtered signal, and the second filtered signal is sampled at the predetermined sampling frequency to generate the reference signal. The ranging system of claim 3, wherein: The source end is used for receiving a source signal, and generating the incident wave according to the source signal; and the arithmetic unit is also used for receiving the source signal, and is also used for performing a low-frequency operation on the source signal under the preset filter bandwidth Pass filtering to generate a second filtered signal, and down-sampling the second filtered signal to generate the reference signal corresponding to a sampling frequency equal to the preset sampling frequency. The ranging system as claimed in claim 1, wherein: the first filtered signal is used as the feedback signal; and the operator is further set to sample the cross-correlation result at an adjustable preset sampling frequency, so as to generate a calculation output. The distance measuring system according to claim 10, further comprising: a reference detector for detecting the incident wave to generate a second detection signal; wherein the operator is further electrically connected to the reference detector to detect the incident wave from the reference detector The reference detector receives the second detection signal, and is further set to perform low-pass filtering on the second detection signal under the preset filter bandwidth, so as to generate the reference signal. The ranging system according to claim 10, wherein: the source end is used for receiving a source signal, and generates the incident wave according to the source signal; and the arithmetic unit is further used for receiving the source signal, and is also set in the pre Perform low-pass filtering on the source signal at a filter bandwidth to generate the reference signal.

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