METHOD FOR ANALYZING BACKSCATTER HISTOGRAM DATA IN AN OPTICAL PULSE RUNTIME METHOD AND DEVICE FOR DATA PROCESSING

Abstract

A method for analyzing backscatter histogram data in an optical pulse runtime method, including the steps of receiving backscatter histogram data; and analyzing the received backscatter histogram data.

Claims

1. A method for analyzing backscatter histogram data in an optical pulse runtime method, comprising: Receiving backscatter histogram data; and Analyzing the received backscatter histogram data.

2. The method according to claim 1, wherein analyzing the received backscatter histogram data comprises: Calculating a similarity measure between the received backscatter histogram data and a predefined reference backscatter signal, so as to determine a backscatter signal.

3. The method according to claim 1, wherein analyzing the received backscatter histogram data comprises: Determining an ambient light quantity from the received backscatter histogram data.

4. The method according to claim 3, to the extent the latter depends on claim 2, wherein analyzing the received backscatter histogram data comprises: Determining an effective detection range for the optical runtime measurement based upon the backscatter signal and the ambient light quantity.

5. The method according to claim 2, wherein a transformation function is applied to the backscatter signal, so as to determine a signal damping factor.

6. The method according to claim 5, wherein the transformation function was determined experimentally.

7. The method according to claim 3, wherein an arithmetic mean is calculated from the received backscatter histogram data of several time intervals that lie before a starting time, so as to determine the ambient light quantity.

8. The method according to claim 3, wherein an arithmetic mean is calculated from the received backscatter histogram data of several time intervals that exceed a specific time threshold, so as to determine the ambient light quantity.

9. The method according to claim 3, wherein an arithmetic mean is calculated from the received backscatter histogram data of several time intervals that lie before a starting time, and from the received backscatter histogram data of several time intervals that exceed a specific time threshold, so as to determine the ambient light quantity.

10. The method according to claim 3, wherein a local minimum which satisfies a specific criterion is determined from the received backscatter histogram data that exceeds a specific time threshold, so as to determine the ambient light quantity.

11. The method according to claim 3, wherein determining the ambient light quantity comprises: Calculating an arithmetic mean from the received backscatter histogram data of several time intervals that lie before a starting time, so as to obtain a first ambient light quantity; Determining a local minimum that satisfies a specific criterion from the received backscatter histogram data that exceed a specific time threshold, so as to obtain a second ambient light quantity; and Determining the ambient light quantity from a comparison between the first ambient light quantity and the second ambient light quantity, wherein the ambient light quantity is determined as the smaller of the two ambient light quantities.

12. The method according to claim 4, wherein the effective detection range of the optical runtime measurement is determined with the help of a predefined function.

13. The method according to claim 4, wherein the effective detection range of the optical runtime measurement is determined from a characteristic diagram.

14. The method according to claim 4, wherein the effective detection range of the optical runtime measurement is determined from a comparison with predefined reference values.

15. A device for data processing, comprising means for implementing a method for analyzing backscatter histogram data in an optical pulse runtime method, comprising: Receiving backscatter histogram data; and Analyzing the received backscatter histogram data .

Description

[0081] Exemplary embodiments of the invention will now be described exemplarily and with reference to the attached drawing, in which:

[0082] FIG. 1 illustrates a first exemplary embodiment of a reference backscatter signal;

[0083] FIG. 2 illustrates a second exemplary embodiment of a reference backscatter signal;

[0084] FIG. 3 illustrates a third exemplary embodiment of a reference backscatter signal;

[0085] FIG. 4 illustrates a scheme of an embodiment for a receiving system for an optical distance measurement;

[0086] FIG. 5 illustrates a flowchart of a first exemplary embodiment of a method for analyzing backscatter histogram data during an optical runtime measurement;

[0087] FIG. 6 illustrates a flowchart of a second exemplary embodiment of a method for analyzing backscatter histogram data during an optical runtime measurement;

[0088] FIG. 7 illustrates a flowchart of a third exemplary embodiment of a method for analyzing backscatter histogram data during an optical runtime measurement; and

[0089] FIG. 8 illustrates a flowchart of a fourth exemplary embodiment of a method for analyzing backscatter histogram data during an optical runtime measurement.

[0090] FIG. 1 illustrates the first exemplary embodiment of a reference backscatter signal.

[0091] The reference backscatter signal illustrated on FIG. 1 corresponds to a typical signal form of the kind that arises in a coaxial LIDAR system, i.e., in a LIDAR system in which there is no parallax between the transmitter and receiver. The reference backscatter signal (in other words, the intensity of the backscattered light) drops off monotonously over time.

[0092] FIG. 2 illustrates the second exemplary embodiment of a reference backscatter signal.

[0093] The reference backscatter signal illustrated on FIG. 2 corresponds to a typical signal form of the kind that arises in a biaxial single-beam LIDAR system. In biaxial systems (i.e., the transmitting and receiving system are at a defined distance, e.g., 10 cm, and have defined beam divergence), an overlap only arises as of a minimal distance (beginning of the signal rise of the reference backscatter signal). The reference backscatter signal thereafter drops according to the progression on FIG. 1. The reference backscatter signal has a low intensity at very small distances, and rises to a maximum, which subsequently drops off monotonously over time.

[0094] FIG. 3 illustrates the third exemplary embodiment of a reference backscatter signal.

[0095] The reference backscatter signal illustrated on FIG. 3 corresponds to a typical signal form of the kind that typically arises in a biaxial multibeam LIDAR system (e.g., according to DE 10 2017 222 971 A1). The reference backscatter signal is similar to a biaxial single-beam LIDAR system, but has several maximums at distances where various beams cross the visual field of the light-detecting receiving elements. For larger distances, the intensity drops off monotonously over time.

[0096] FIG. 4 illustrates a scheme of an exemplary embodiment of a receiving system 1 for an optical distance measurement.

[0097] The receiving system 1 has a receiving matrix 2, on which several light-detecting receiving elements (ENxM, in this exemplary embodiment E0,0 to E127,255) are arranged in rows (Z0 to Z127) and columns (S0 to S255). M=256 light-detecting receiving elements (E0.0 to E127.255) are arranged in each of the N=128 rows (Z0 to Z127) (corresponding to the M=256 columns (S0 to S255)). The light-detecting receiving elements (E0.0 to E127,255) are SPAD’s in this exemplary embodiment.

[0098] The receiving system 1 further has several evaluation units (A0 to A127), wherein a respective evaluation unit (A0 to A127) is connected with the light-detecting receiving elements (E0.0 to E127.255) of a row (Z0 to Z127) via a multiplexer (not shown). In each row (Z0 to Z127), only the two light-detecting receiving elements (E0,0 and E0,1 to E127,0 and E127,1) are activated in the columns S0 and S1 at a given time (illustrated by the second circle within the light-detecting receiving elements (E0,0 and E0,1 to E127,0 and E127,1)). Upon the detection of light, the activated light-detecting receiving elements (E0,0 and E0,1 to E127,0 and E127,1) generate electrical signals, from which time-correlated histogram data are generated with the help of a time-to-digital converter (not shown) in each of the evaluation units (A0 to A127). In this exemplary embodiment, the time-correlated histogram data of the two activated light-detecting receiving elements (E0,0 and E0,1 to E127,0 and E127,1) are added together in the evaluation units (A0 to A127), so as to generate and output time-correlated histogram data. In other exemplary embodiments, any desired number of M=256 light-detecting receiving elements (E0,0 to E127,255) can be activated in each row, e.g., E0,0 to E0,10, E1,0 to E1,10, E2,0 to E2,10, ..., E127,0 to E127,10.

[0099] The receiving system 1 further has several histogram accumulation units (HAO to HAX). Each histogram accumulation unit (HAO to HAX) has P=16 signal inputs (not explicitly shown), wherein each signal input is connected with a respective evaluation unit (A0 to A127). For this reason, X=N/P=8 histogram accumulation units are required in this exemplary embodiment at N=128 rows (Z0 to Z127), which correspondingly accumulate the time-correlated histogram data of P=16 evaluation units (A0 to A127). The time-correlated histogram data output by the evaluation units (A0 to A127) are transmitted to the histogram accumulation units (HAO to HAX), so that the latter are received at the signal inputs. Based upon the received time-correlated histogram data, the histogram accumulation units (HAO to HAX) generate backscatter histogram data. In this exemplary embodiment, the time-correlated histogram data received at each signal input are added together, so as to generate the backscatter histogram data.

[0100] The receiving system 1 further has a device 3 for data processing, which has a processor and storage elements (not shown). The histogram accumulation units (HAO to HAX) output the generated backscatter histogram data, which are received by the device 3 for data processing. The device 3 for data processing analyzes the received backscatter histogram data. In this exemplary embodiment, the device 3 for data processing calculates a correlation between the received backscatter histogram data and the reference backscatter signal from FIG. 3, so as to determine a backscatter signal, for example one ascertained as a backscatter indicator or backscatter signal strength.

[0101] FIG. 5 illustrates a flowchart of the first exemplary embodiment of a method 20 for analyzing backscatter histogram data during an optical runtime measurement.

[0102] Backscatter histogram data are received at 21, as explained herein.

[0103] The received backscatter histogram data are analyzed at 22, as explained herein.

[0104] A similarity measure between the received backscatter histogram data and a predefined reference backscatter signal is calculated at 23 so as to determine a backscatter signal, as explained herein.

[0105] A transformation function is applied to the backscatter signal at 24 so as to obtain a signal damping factor, as explained herein.

[0106] Wherein the transformation function from step 24 was experimentally determined (beforehand) at 25, as explained herein.

[0107] FIG. 6 illustrates a flowchart of the second exemplary embodiment of a method 30 for analyzing backscatter histogram data during an optical runtime measurement.

[0108] Backscatter histogram data are received at 31, as explained herein.

[0109] The received backscatter histogram data are analyzed at 32, as explained herein.

[0110] An ambient light quantity is determined from the received backscatter histogram data at 33, as explained herein.

[0111] Steps 34 to 36 are options that are each implemented separately.

[0112] An arithmetic mean is calculated at 34 from the received backscatter histogram data of several time intervals that lie before a starting time, so as to determine the ambient light quantity, as explained herein.

[0113] An arithmetic mean is calculated at 35 from the received backscatter histogram data of several time intervals that exceed a specific time threshold, so as to determine the ambient light quantity, as explained herein.

[0114] An arithmetic mean is calculated at 36 from the received backscatter histogram data of several time intervals that lie before a starting time so as to determine the ambient light quantity, and from the received backscatter histogram data of several time intervals that exceed a specific time threshold, so as to determine the ambient light quantity, as explained herein.

[0115] FIG. 7 illustrates a flowchart of the third exemplary embodiment of a method 40 for analyzing backscatter histogram data during an optical runtime measurement.

[0116] Backscatter histogram data are received at 41, as explained herein.

[0117] The received backscatter histogram data are analyzed at 42, as explained herein.

[0118] An ambient light quantity is determined from the received backscatter histogram data at 43, as explained herein. Steps 44 and 45 are options that are each implemented separately.

[0119] A local minimum which satisfies a specific criterion is determined at 44 from the received backscatter histogram data that exceed a specific time threshold, so as to determine the ambient light quantity, as explained herein.

[0120] At 45, an arithmetic mean is calculated from the received backscatter histogram data of several time intervals that lie before a starting time as to obtain a first ambient light quantity, and a local minimum that satisfies a specific criterion is determined from the received backscatter histogram data that exceeds a specific time threshold, so as to determine a second ambient light quantity, and an ambient light quantity is determined from a comparison between the first ambient light quantity and second ambient light quantity, wherein the ambient light quantity is determined as the smaller of the two ambient light quantities, as explained herein.

[0121] FIG. 8 illustrates a flowchart of the fourth exemplary embodiment of a method 50 for analyzing backscatter histogram data during an optical runtime measurement.

[0122] Backscatter histogram data are received at 51, as explained herein.

[0123] The received backscatter histogram data are analyzed at 52, as explained herein.

[0124] A similarity measure between the received backscatter histogram data and a predefined reference backscatter signal is calculated at 53 so as to determine a backscatter signal, as explained herein.

[0125] An ambient light quantity is determined from the received backscatter histogram data at 54, as explained herein.

[0126] An effective detection range of the optical runtime measurement is determined at 55 based upon the backscatter signal, for example which is determined as the backscatter indicator or backscatter signal strength, and the ambient light quantity, as explained herein.

[0127] Steps 56 to 58 are options that are each implemented separately.

[0128] The effective detection range of the optical runtime measurement is determined at 56 with the help of a predefined function, as explained herein.

[0129] The effective detection range of the optical runtime measurement is determined at 57 from a characteristic diagram, as explained herein.

[0130] The effective detection range of the optical runtime measurement is determined at 58 from a comparison with predefined reference values, as explained herein.

Reference List

[0131] 1 Receiving system

[0132] 2 Receiving matrix

[0133] 3 Device

[0134] 20, 30, 40, 50 Method

[0135] 21, 31, 41, 51 Receiving backscatter histogram data

[0136] 22, 32, 42, 52 Analyzing the received backscatter histogram data

[0137] 23, 53 Calculating a similarity measure between the received backscatter histogram data and a predefined reference backscatter signal, so as to determine a backscatter signal

[0138] 24 Applying a transformation function to the backscatter signal, so as to obtain a signal damping factor

[0139] 25 Experimentally determining the transformation function

[0140] 33, 43, 54 Determining an ambient light quantity from the received backscatter histogram data

[0141] 34 Calculating an arithmetic mean from the received backscatter histogram data of several time intervals that lie before a starting time, so as to determine the ambient light quantity

[0142] 35 Calculating an arithmetic mean from the received backscatter histogram data of several time intervals that exceed a specific time threshold, so as to determine the ambient light quantity

[0143] 36 Calculating an arithmetic mean from the received backscatter histogram data of several time intervals that lie before a starting time, and from the received backscatter histogram data of several time intervals that exceed a specific time threshold, so as to determine the ambient light quantity

[0144] 44 Determining a local minimum that satisfies a specific criterion from the received backscatter histogram data that exceeds a specific time threshold, so as to determine the ambient light quantity

[0145] 45 Calculating an arithmetic mean from the received backscatter histogram data of several time intervals that lie before a starting time, and from the received backscatter histogram data of several time intervals that exceed a specific time threshold, so as to determine a first ambient light quantity; determining a local minimum that satisfies a specific criterion from the received backscatter histogram data that exceeds a specific time threshold, so as to determine a second ambient light quantity; and determining the ambient light quantity from a comparison between the first ambient light quantity and the second ambient light quantity, wherein the ambient light quantity is determined as the smaller of the two ambient light quantities

[0146] 55 Determining an effective detection range of the optical runtime measurement based upon the backscatter signal and the ambient light quantity

[0147] 56 Determining an effective detection range of the optical runtime measurement with the help of a predefined function

[0148] 57 Determining an effective detection range of the optical runtime measurement from a characteristic diagram

[0149] 58 Determining an effective detection range of the optical runtime measurement from a comparison with predefined reference values

[0150] A0 to A127 Evaluation units

[0151] ENxM, E0,0 to E127,255 Light-detecting receiving elements

[0152] HA0 to HAX Histogram accumulation units

[0153] S0 to S255 Columns

[0154] Z0 to Z127 Rows