Lidar device with a laser retuned by a diffraction grating

Abstract

A LIDAR device with a laser retuned by a diffraction grating (1), which contains an auxiliary detector (5) for generating an electrical signal for synchronizing and measuring the energy of the departing laser beam, characterized in that the auxiliary detector (5) is arranged with respect to the diffraction grating (1) in an area where the energy of the laser radiation falls from the +1st diffraction maximum (8) of grating (1).

Description

[0001] LIDAR device with a laser retuned by a diffraction grating

[0002] Field of technology

[0003] The invention relates to LIDAR devices that use a laser or lasers retuned by a diffraction grating.

[0004] Prior art

[0005] The usual known arrangement of a LIDAR device with a retuned laser or lasers uses the so-called beam splitter placed in front of the laser, i.e. on the side where the laser beam departs to the target, and an auxiliary detector that generates an electrical signal on synchronizing and measurement of the departing energy from this laser beam. The mentioned arrangement is schematically shown in Fig. 1.

[0006] The beam splitter diverts a part of the energy to the auxiliary detector, which produces a synchronization signal and at the same time enables the measurement of the departing energy.

[0007] The disadvantages of the mentioned known arrangement are that a part of the energy of the laser pulse is lost, although this is used for synchronization and measurement of the departing energy and represents e.g. "only" 10%, which could, however, be used for the operation of the LIDAR device, for example for detection. The consequence of the mentioned fact is then a reduction in the reach and reliability of the measurement of the device. Furthermore, a relatively expensive beam splitter must be used, which complicates the construction of the device and increases its dimensions and weight. In addition, the beam splitter has spectrally dependent characteristics, which are slightly different for each piece, which means that during retuning, the dividing ratio of the beam splitter changes, which complicates the calibration of the device.

[0008] The aim of the mentioned invention is to substantially eliminate the disadvantages of the prior art. The essence of the invention

[0009] The mentioned aim achieved by a LIDAR device with a laser retuned by a diffraction grating according to the present invention, which contains an auxiliary detector for generating an electrical signal for synchronizing and measuring the energy of the departing laser beam. The essence of this invention lies in the fact that the auxiliary detector is arranged with respect to the diffraction grating in an area where the energy of the laser radiation falls from the +lst, plus the first, diffraction maximum of the diffraction grating.

[0010] Overview of figures on drawings

[0011] The invention is explained in more detail with the help of figures in the accompanying drawings, in which Fig. 1 schematically shows the arrangement of a LIDAR device according to the prior art and Fig. 2 schematically shows the arrangement of a LIDAR device according to the invention.

[0012] Examples of the embodiments

[0013] An example of the embodiment of the LIDAR device according to the invention mentioned below with reference to Fig. 2, describes the arrangement of the LIDAR device, which contains a laser retuned by a diffraction grating 1, and which contains an auxiliary detector 5 for generating an electrical signal for synchronizing and measuring the energy of the laser beam departing to the target, to the measurement destination, i.e. of the departing laser beam.

[0014] The laser retuned by a diffraction grating 1, shown in Fig. 1 and Fig. 2, has a resonator 10 in a so-called Litorow arrangement, i.e. at a location where there is usually an impermeable mirror in the resonator of the laser, there is a diffraction grating 1 in the described arrangement.

[0015] The diffraction grating 1 returns the energy that comes from the -1st(minus the first) diffraction maximum 2 of grating 1, to the resonator 10. The construction of grating 1 tends to be optimized so that the grating returns as much energy as possible to the - 1stdiffraction maximum 2, e.g. up to 95%. Most of the remaining energy, e.g. almost 5 %, is in the +lst(plus first) diffraction maximum 8, i.e. symmetrically around the normal line 3 to grating 1 with respect to the -1st(minus first) diffraction maximum 2, while (in the classic LIDAR arrangement) this energy is lost.

[0016] An auxiliary detector 5 in the LIDAR device according to the invention, according to Fig. 2, is arranged with respect to the diffraction grating 1 in the area where the laser radiation energy falls from the +lstdiffraction maximum 8 of grating 1.

[0017] In the arrangement of the LIDAR device according to the prior art, shown in Fig. 1, an electrical signal for synchronizing and measuring the energy of the laser beam departing to the target is generated by the auxiliary detector 5 from the reflected part 9 from the beam splitter 7. The beam splitter 7 is placed behind the resonator 10 in the direction of the axis 6 of the laser beam departing to the target.

[0018] In contrast to the arrangement described in the prior art, LIDAR device according to the invention does not require a beam splitter 7, which significantly simplifies the construction of the device, and at the same time it is not necessary to correct the device for errors introduced by the beam splitter 7 as such, and there is also an efficient use of the laser pulse energy for the operation of the device, as will be explained below.

[0019] As mentioned in the prior art, a part of the energy of the laser pulse, the laser beam departing from the resonator 10 to the destination, is practically lost by passing through the beam splitter 7. This loss is eliminated by the absence of the beam splitter 7 in the solution according to the invention, and at the same time the energy from the laser resonator 10 is used, which in the mentioned Litorow arrangement practically departs in two ways: firstly through semitransmissive mirror 4, while at 90% reflectivity of this mirror 4, the departing power is 10% of the internal resonator power of resonator 10, and on the other hand through the +lstdiffraction maximum 8 of grating 1, where 5% of the internal resonator power reaches. In other words, energy in the +lstdiffraction maximum 8 equals up to half of the energy used for the operation of the LIDAR device.

[0020] Analogically, the solution is also applied in the case where the LIDAR device contains several lasers or laser resonators 10.

Claims

CLAIMS1. A LIDAR device with a laser retuned by a diffraction grating (1), which contains an auxiliary detector (5) for generating an electrical signal for synchronizing and measuring the energy of the departing laser beam, characterized in that the auxiliary detector (5) is arranged with respect to the diffraction grating (1) in an area where the energy of the laser radiation falls from the +lstdiffraction maximum (8) of grating (1).

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