Multispectral active remote sensor
Disclosed is a radiation arrangement for a multispectral active remote sensing device. The arrangement includes a transceiver, a detector, and a wavelength-adjustable narrow band stopper.
1 . Method for operating a radiation arrangement for a multispectral active remote sensing device controlled by an electronic control system, and comprising:
a transceiver configured for receiving a radiation beam from the radiation source; the transceiver being further configured for outputting a transmitted peart of the radiation beam on a target, and further configured to receive a reflected part of the radiation beam from the target; wherein the radiation beam has a broadband spectral range,
a detector configured to detect a time-of-flight and a radiation power of the reflected part of the radiation beam; and
a wavelength-adjustable narrow band stopper arranged on a radiation path from the radiation source to the detector, wherein
the wavelength-adjustable narrow band stopper is configured to transmit the radiation beam in all the spectral range but a narrow band centered on a selected wavelength (λ_k), wherein the wavelength-adjustable narrow band stopper is further configured to sequentially set the selected wavelength (λ_k) to another wavelength (λ_k+1), of the spectral range, such that the detector receives a partial radiation power, which is the radiation power of the received reflection of the radiation beam in all the spectral range but the narrow band centered on the selected wavelength,
the method comprising:
sensing, by the detector, a total radiation power, which is the optical power of the reflected part of the radiation beam on the whole spectral range, and
sensing, by the detector, the partial radiation power associated to the selected wavelength (λ_k), then
calculate a band radiation power associated to the selected wavelength (λ_k), by comparison of the total radiation power and the partial radiation power.
2 . A radiation arrangement for a multispectral active remote sensing device controlled by an electronic control system, comprising:
a transceiver configured for receiving a radiation beam from a radiation source; the transceiver being further configured for outputting a transmitted part of the radiation beam on a target, and further configured to receive a reflected part of the radiation beam from the target; wherein the radiation beam has a broadband spectral range,
a detector configured to detect a time-of-flight and a radiation power of the reflected part of the radiation beam; and
a wavelength-adjustable narrow band stopper arranged on a radiation path from the radiation source to the detector, wherein
the wavelength-adjustable narrow band stopper is configured to transmit the radiation beam in all the spectral range but a narrow band centered on a selected wavelength (λ_k), wherein the wavelength-adjustable narrow band stopper is further configured to sequentially set the selected wavelength (λ_k) to another wavelength (λ_k+1), of the spectral range, such that the detector receives a partial radiation power, which is the radiation power of the received reflection of the radiation beam in all the spectral range but the narrow band centered on said selected wavelength,
wherein the optical detector is further configured to sequentially detect the partial radiation power in association with the selected wavelength, and
wherein the electronic control system is further configured to calculate a band radiation power associated to the selected wavelength (λ_k), by comparing the partial radiation power in association with the selected wavelength to a total radiation power, which is the optical power of the reflected part of the radiation beam on the whole spectral range.
3 . The radiation arrangement according to claim 2 , wherein the wavelength-adjustable narrow band stopper is arranged on a radiation path of the radiation beam from the radiation source to the transceiver, or the wavelength-adjustable narrow band stopper is arranged on a radiation path of the radiation beam from transceiver to the detector, or the wavelength-adjustable narrow band stopper is arranged on a radiation path of the radiation beam between the transceiver and the target.
4 . The radiation arrangement according to claim 2 , wherein the wavelength-adjustable narrow band stopper is further configured to sequentially select a number N of selected wavelength, wherein N is comprised between 4 and 6, wherein the spectral range of the laser beam is about 300 nm, between 1400 nm and 1700 nm.
5 . The radiation arrangement according to claim 2 , wherein the multispectral active remote sensing device is a multispectral LiDAR, wherein:
the radiation arrangement is an optical arrangement, and the radiation source is a laser source, the radiation beam being a laser beam,
the transceiver is an optical transceiver, the detector being an optical detector, the radiation power being an optical power, and the partial radiation power being a partial optical power.
6 . The radiation arrangement according to claim 5 , wherein the wavelength-adjustable narrow band stopper comprises a filter per selected wavelength, wherein the filter is a notch filter having a narrow band value comprised between 9 nm and 20 nm, centered on said selected wavelength.
7 . The radiation arrangement according to claim 5 , wherein the wavelength-adjustable narrow band stopper comprises a filter per selected wavelength, wherein the filter is selected from the list consisting of:
a Hard Coated Bandpass Filter having an Optical Density value of 4.0, and a narrow band value of 45 or 50 nm centered on said selected wavelength, or
dichroic filters.
8 . The radiation arrangement according to claim 5 , wherein the wavelength-adjustable narrow band stopper comprises a wavelength-tunable notch filter configured to block the narrow band centered on a notch wavelength, wherein the notch filter is controlled such as to tune the notch wavelength on the selected wavelength value.
9 . The radiation arrangement according to claim 8 , wherein the wavelength-tunable notch filter is based on liquid crystal modulators, or the wavelength-adjustable narrow band stopper comprises volume holographic notch filters.
10 . The radiation arrangement according to claim 2 , wherein the transceiver has a spatial scanning function, and the detector comprises a single radiation power sensor.
11 . A multispectral active remote sensing device comprising an arrangement according to claim 1 , further comprising the radiation source.
12 . A multispectral LIDAR device comprising a laser radiation source and an optical radiation arrangement, the optical radiation arrangement comprising:
an optical transceiver configured for receiving a laser radiation beam from a laser radiation source; the transceiver being further configured for outputting a transmitted part of the laser radiation beam on a target, and further configured to receive a reflected part of the laser radiation beam from the target; wherein the laser radiation beam has a broadband spectral range,
an optical detector configured to detect a time-of-flight and an optical radiation power of the reflected part of the laser radiation beam; and
a wavelength-adjustable narrow band stopper arranged on an radiation path from the radiation source to the detector, wherein
the wavelength-adjustable narrow band stopper is configured to transmit the laser radiation beam in all the spectral range but a narrow band centered on a selected wavelength (λ_k), wherein the wavelength-adjustable narrow band stopper is further configured to sequentially set the selected wavelength (λ_k) to another wavelength (λ_k+1), of the spectral range, such that the optical detector receives a partial optical radiation power, which is the optical radiation power of the received reflection of the laser radiation beam in all the spectral range but the narrow band centered on said selected wavelength,
wherein the optical detector is further configured to sequentially detect the partial optical radiation power in association with the selected wavelength.
13 . The multispectral LIDAR device according to claim 12 , wherein the wavelength-adjustable narrow band stopper is arranged on a radiation path of the laser radiation beam from the laser radiation source to the optical transceiver, or the wavelength-adjustable narrow band stopper is arranged on a radiation path of the laser radiation beam from the optical transceiver to the optical detector, or the wavelength-adjustable narrow band stopper is arranged on a radiation path of the laser radiation beam between the optical transceiver and the target.
14 . The multispectral LIDAR device according to claim 12 , wherein the wavelength-adjustable narrow band stopper is further configured to sequentially select a number N of selected wavelength, wherein N is comprised between 4 and 6, and wherein the spectral range of the laser beam is about 300 nm, between 1400 nm and 1700 nm.
15 . The multispectral LIDAR device according to claim 12 , wherein the wavelength-adjustable narrow band stopper comprises a filter per selected wavelength, wherein the filter is a notch filter having a narrow band value comprised between 9 nm and 20 nm, centered on said selected wavelength.
16 . The multispectral LIDAR device according to claim 12 , wherein the wavelength-adjustable narrow band stopper comprises a filter per selected wavelength, wherein the filter is selected from the list consisting of:
a Hard Coated Bandpass Filter having an Optical Density value of 4.0, and a narrow band value of 45 or 50 nm centered on said selected wavelength, or
dichroic filters.
17 . The multispectral LIDAR device according to claim 12 , wherein the wavelength-adjustable narrow band stopper comprises a wavelength-tunable notch filter configured to block the narrow band centered on a notch wavelength, wherein the notch filter is controlled such as to tune the notch wavelength on the selected wavelength value.
18 . The multispectral LIDAR device according to claim 12 , wherein the wavelength-tunable notch filter is based on liquid crystal modulators or the wavelength-adjustable narrow band stopper comprises volume holographic notch filters.
19 . The multispectral LIDAR device according to claim 12 , wherein the transceiver has a spatial scanning function and the detector comprises a single radiation power optical sensor.
20 . The multispectral LIDAR device according to claim 12 , wherein a path of the laser radiation beam from the optical transceiver to the target coincides with a return path from the target to the optical transceiver.