Method for laser radar and imaging spectrometer optical center coincidence

Abstract

The present application relates to a kind of laser radar and imaging spectrometer optical center coincides with method, signal light beam is divided into different wavelength range reflected light beam and transmission light beam after reaching filter;The wavelength range of the working of imaging spectrometer and laser radar is different, in corresponding wavelength range light path, respectively set up in line with reflected light beam wavelength range and transmission light beam wavelength range imaging spectrometer and laser radar;Wherein, signal light beam has a certain angle when incident filter;The filter has position coincident reflection point and transmission point at the place where signal light beam reaches.The distance of the imaging center of the imaging spectrometer to reflection point is equal to the distance of the imaging center of the laser radar to transmission point.The optical center coincides with method provided by the present application can make the imaging center of two devices completely coincide, so as to ensure that the data measured by imaging spectrometer and the data measured by radar come from exactly the same spatial position.To achieve the purpose of accurate fusion of two kinds of data.

Description

Technical Field

[0001] This invention belongs to the field of airborne hyperspectral and airborne lidar measurement technology, and particularly relates to a method for aligning the optical centers of lidar and imaging spectrometer. Background Technology

[0002] A lidar can be understood as a laser rangefinder that can quickly switch measurement angles. It can provide the distance and angle relationship between each measured point and a specific point, which we call the lidar's imaging center. An imaging spectrometer, on the other hand, captures data along only one line at a time. Each point on this line is equivalent to being observed from a specific point, which we call the imaging center of the imaging spectrometer.

[0003] LiDAR and imaging spectrometers are both commonly used airborne equipment in the surveying and remote sensing industry, and their data have strong potential for combined use. However, due to the characteristics of airborne surveying, particularly the tendency for changes in measurement angles during the measurement process, accurately unifying the data from both into the same coordinate system is very difficult. The primary method relies on ground control points. This involves placing several clearly visible markers on the ground, finding the same control points in both sets of data, matching these coordinates one-to-one, and then interpolating the other coordinate data to achieve a one-to-one correspondence between the two sets of data and their coordinates. The drawbacks of this method are: 1. Setting up control points generates a significant workload, which is impractical in many terrain conditions, such as jungles. 2. The number of control points is limited; the absence of control points introduces errors. 3. Due to the randomness of measurement angles during airborne surveying and factors such as the ground not being perfectly level, the data is not always a one-to-one match. That is, sometimes the same coordinates may represent different objects measured by LiDAR and imaging spectrometers. 4. The control point method also requires considerable manual processing in post-processing, resulting in low efficiency.

[0004] The current method involves installing two devices into a single system, with the imaging centers as close as possible, such as 10cm apart. The line connecting the centers is parallel to the aircraft's heading. Assuming the aircraft is in relatively stable flight with an initial speed of 2m / s, the two centers will pass the same measurement point within an extremely short timeframe of 0.05s. By matching time series data, such as the latest radar data with hyperspectral data from 0.05s prior, we assume that both sets of data were measured simultaneously from the same imaging center. The data are then matched according to their angles.

[0005] However, the drawback of this method is that it cannot guarantee that the imaging center will pass through the same point in space and that the observation angle will be consistent. Therefore, it can only be considered a very good approximation method.

[0006] In summary, the current method involves a large amount of work and has a large error rate. Summary of the Invention

[0007] (a) Technical problems to be solved

[0008] To address the existing technical problems, this invention provides a method for aligning the optical centers of a lidar and an imaging spectrometer, which enables the imaging centers of the two devices to completely overlap, thereby ensuring that the measurement positions and angles are the same, and achieving the purpose of accurate fusion of the two types of data.

[0009] (II) Technical Solution

[0010] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0011] A method for aligning the optical centers of a lidar and an imaging spectrometer, wherein the signal beam is split into reflected beams and transmitted beams of different wavelength ranges after reaching the filter;

[0012] Imaging spectrometers and lidars operate in different wavelength ranges. Imaging spectrometers and lidars that conform to the wavelength range of reflected beams and transmitted beams are respectively set up in the optical paths of the corresponding wavelength ranges.

[0013] The signal beam enters the filter at a certain angle;

[0014] The filter has a reflection point and a transmission point that coincide in position at the point where the signal beam arrives.

[0015] Preferably, the distance from the imaging center of the imaging spectrometer to the reflection point is equal to the distance from the imaging center of the lidar to the transmission point.

[0016] Preferably, the method further includes: selecting an imaging spectrometer and a lidar with different operating wavelength ranges;

[0017] Select filters that meet the wavelength range requirements of imaging spectrometers and lidar;

[0018] The filter is capable of transmitting light in a first wavelength range and reflecting light in a second wavelength range.

[0019] Preferably, the filter is a dichroic filter;

[0020] The filter is placed on the path of the signal beam and arranged at a 45° angle to the signal beam.

[0021] Preferably, the filter is capable of reflecting light with wavelengths below 1000nm;

[0022] The filter can transmit light with wavelengths above 1000nm.

[0023] Preferably, the operating wavelength of the lidar is greater than 1000nm;

[0024] The imaging spectrometer operates at wavelengths of 400-1000 nm.

[0025] Preferably, the first wavelength band is different from the second wavelength band.

[0026] Preferably, when the first wavelength range meets the requirements of the imaging spectrometer, the light energy in the second wavelength range meets the requirements of the lidar;

[0027] When the second wavelength range meets the requirements of the imaging spectrometer, the first wavelength range meets the requirements of the lidar.

[0028] (III) Beneficial Effects

[0029] The beneficial effects of this invention are as follows: The method for aligning the optical centers of a lidar and an imaging spectrometer provided by this invention has the following beneficial effects:

[0030] This method allows the imaging centers of the two devices to completely overlap, thus ensuring that the measurement positions and angles are the same, and providing a more accurate way to fuse the two data.

[0031] This method also provides an excellent solution for combining lidar and imaging spectrometer data, as well as for cross-verification of data.

[0032] This method achieves the overlap of the two imaging centers, greatly improving the accuracy of data fusion. Attached Figure Description

[0033] Figure 1 This is a schematic diagram illustrating the method for aligning the optical centers of a lidar and an imaging spectrometer, as provided by the present invention.

[0034] Figure label:

[0035] 1: Signal beam; 2: Reflected beam; 3: Transmitted beam; 4: Filter; 5: Imaging spectrometer; 6: LiDAR. Detailed Implementation

[0036] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] like Figure 1As shown: This embodiment discloses a method for aligning the optical centers of a lidar and an imaging spectrometer. After the signal beam 1 reaches the filter 4, it splits into a reflected beam 2 and a transmitted beam 3 with different wavelength ranges. The imaging spectrometer 5 and the lidar 6 operate within different wavelength ranges. Imaging spectrometer 5 and lidar 6 are respectively positioned along their corresponding wavelength paths, conforming to the wavelength ranges of the reflected beam 2 and the transmitted beam 3. The signal beam enters the filter 4 at a certain angle. The filter 4 has a reflection point and a transmission point that coincide at the point where the signal beam 1 arrives. It should be noted that the signal beam in this embodiment carries the reflection spectral intensity information of the surface material and the pulse information of the lidar.

[0038] The wavelengths of the reflected light and transmitted light from filter 4 are determined based on actual needs, and filters with appropriate physical properties are selected for use. No specific wavelength is limited here, as long as it meets the different operating wavelength requirements of the lidar 6 and the imaging spectrometer 5.

[0039] Specifically, the distance between the imaging spectrometer 5 and the reflection point is equal to the distance between the lidar 6 and the transmission point.

[0040] The method described in this embodiment further includes: selecting an imaging spectrometer 5 and a lidar 6 with different operating wavelength ranges; selecting a filter 4 that can meet the operating wavelength range requirements of the imaging spectrometer 5 and the lidar 6; the filter 4 can transmit light in the first wavelength range and reflect light in the second wavelength range.

[0041] In this embodiment, the filter 4 is a fluorescent dichroic filter. The filter 4 is disposed on the optical path of the signal beam carrying data information, and is arranged at a 45° angle to the signal beam carrying data information. The filter 4 can reflect light with wavelengths below 1100nm and can transmit light with wavelengths above 1100nm. The operating wavelength of the lidar 6 is greater than 1550nm; the operating wavelength of the imaging spectrometer 5 is 400-1000nm.

[0042] In this embodiment, the first wavelength range is different from the second wavelength range. When the first wavelength range meets the requirements of the imaging spectrometer 5, the light energy in the second wavelength range meets the requirements of the lidar 6; when the second wavelength range meets the requirements of the imaging spectrometer 5, the first wavelength range meets the requirements of the lidar 6.

[0043] In this embodiment, we selected a lidar 6 with a working wavelength of 1550nm and an imaging spectrometer 5 with a wavelength of 400-1000nm.

[0044] Set A and B to be equidistant from the reflection and transmission points, respectively. Simultaneously, set up an imaging spectrometer 5 and a lidar 6 at positions A and B, respectively, so that their imaging centers are optically perfectly aligned.

[0045] This achieves the overlap of imaging centers, minimizing inconsistencies and errors caused by spatial position and measurement angle, and also achieving complete synchronization of measurement time.

[0046] We chose these operating wavelength sensors merely to illustrate that such a device can be constructed as long as the two sensors operate in different wavelength bands.

[0047] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can conceive of other specific embodiments of the invention without creative effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A method for aligning the optical centers of a lidar and an imaging spectrometer, characterized in that, After the signal beam reaches the filter, it is split into reflected beams and transmitted beams of different wavelength ranges; Imaging spectrometers and lidars operate in different wavelength ranges. Imaging spectrometers and lidars that conform to the wavelength range of reflected beams and transmitted beams are respectively set up in the optical paths of the corresponding wavelength ranges. The signal beam enters the filter at a certain angle; The filter has a reflection point and a transmission point that coincide at the location where the signal beam arrives; The distance from the imaging center of the imaging spectrometer to the reflection point is equal to the distance from the imaging center of the lidar to the transmission point.

2. The method according to claim 1, characterized in that, The method further includes: selecting imaging spectrometers and lidars with different operating wavelength ranges; Select filters that meet the wavelength range requirements of imaging spectrometers and lidar; The filter is capable of transmitting light in a first wavelength range and reflecting light in a second wavelength range.

3. The method according to claim 1, characterized in that, The filter is a dichroic filter; The filter is placed on the path of the signal beam and arranged at a 45° angle to the signal beam.

4. The method according to claim 1, characterized in that, The filter is capable of reflecting light with wavelengths below 1100nm; The filter can transmit light with wavelengths above 1100nm.

5. The method according to claim 4, characterized in that, The operating wavelength of the lidar is greater than 1550nm; The imaging spectrometer operates at wavelengths of 400-1000 nm.

6. The method according to claim 2, characterized in that, The first wavelength band is different from the second wavelength band.

7. The method according to claim 6, characterized in that, When the first wavelength range can meet the requirements of the imaging spectrometer, the second wavelength range of light can meet the requirements of the lidar. When the second wavelength range meets the requirements of the imaging spectrometer, the first wavelength range meets the requirements of the lidar.

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