Fmcw lidar and fmcw lidar wavelength control method using the same

Abstract

The present invention relates to an FMCW lidar and a method for controlling the wavelength width of an FMCW lidar using the same. According to one embodiment of the present invention, an FMCW lidar may be provided, comprising: a resonator configured to output a target light having a single target wavelength; and a polarization controller for removing optical noise present in the target light output from the resonator, wherein the resonator comprises: a light source unit that outputs light having a predetermined wavelength; and two or more grating units that provide a fine grating formed so that the target light selectively passes through by the light output from the light source unit being transmitted back and forth, and wherein the light source unit comprises a first light source that outputs a first light having a spectrum including the target wavelength and transmits it to the grating unit.

Description

Technology Field

[0001] The present invention relates to an FMCW lidar and a method for controlling the wavelength width of an FMCW lidar using the same. Background Technology

[0002] Lidar is a technology that irradiates a target with a laser, measures the time it takes for the laser to be reflected from the target and enter a detector to determine the distance to the target, and based on this, acquires a three-dimensional image of the target. In Lidar technology, laser transmission and reception methods include pulse, FMCW, and FSK (frequency shift keying), and the method of extracting the speed and distance of the target varies depending on each method.

[0003] Pulsed LiDAR technology requires high-power lasers or high-sensitivity detectors for long-distance measurements, resulting in high costs, potential impact on eye safety, and the risk of mutual interference between multiple LiDAR signals.

[0004] In contrast, FMCW (frequency modulated continuous wave) lidar is a lidar that simultaneously transmits a continuous wave signal and receives a reflected wave signal from a target. In this case, FMCW lidar extracts relative distance and relative velocity information of the target using the beat frequency, which is the difference frequency component between the transmitted and received signals. Since it uses a laser interferometer for target signal detection, it is not affected by the external environment and can be implemented relatively simply, leading to extensive research in various fields.

[0005] These FMCW lidars are used for long-distance measurements in many industrial settings. When using such FMCW lidars for long-distance measurements, the accuracy and measurability of the measurement are determined by the laser output (power) and laser linewidth emitted by the FMCW lidar.

[0006] However, if the laser output is increased infinitely to emit lasers in order to improve the accuracy and measurability of long-distance measurements, there is a risk of safety accidents if the laser enters a person's eyes; therefore, there are limits to increasing the laser output to improve the accuracy and measurability of long-distance measurements.

[0007] Therefore, by adjusting the single linewidth of the laser emitted from the FMCW lidar, the accuracy and measurability of long-distance measurements can be improved. In other words, the closer the wavelength of the laser emitted from the FMCW lidar is to a perfect single wavelength, the more the performance of the FMCW lidar can be improved for long-distance measurements.

[0008] Therefore, there is a growing need for FMCW lidars capable of emitting lasers close to a perfect single wavelength without increasing the laser output infinitely. The problem to be solved

[0009] Embodiments of the present invention were invented against the background described above, and aim to provide an FMCW lidar capable of emitting a laser close to a perfect single wavelength without increasing the laser output of the FMCW lidar infinitely. means of solving the problem

[0010] According to embodiments of the present invention, an FMCW lidar may be provided, comprising: a resonator configured to output a target light having a single target wavelength; and a polarization controller for removing optical noise present in the target light output from the resonator, wherein the resonator comprises: a light source unit that outputs light having a predetermined wavelength; and two or more grating units that provide a fine grating formed such that the target light selectively passes through by the light output from the light source unit being transmitted back and forth, and wherein the light source unit comprises a first light source that outputs a first light having a spectrum including the target wavelength and transmits it to the grating unit.

[0011] Additionally, an FMCW lidar may be provided, wherein the light source unit further includes a second light source that outputs a second light having a smaller wavelength than the first light, and the resonator further includes a pump that pumps the second light to be delivered to the first light.

[0012] Additionally, an FMCW lidar may be provided, further comprising an optical coupling unit that combines the first light and the second light, wherein the optical coupling unit transforms the second light into a second modified light having the same wavelength as the first light by coupling the second light to the first light.

[0013] Additionally, an FMCW lidar may be provided, wherein the resonator further comprises an optical amplification and transmission unit that optically amplifies and transmits the first light and the second modified light received from the optical coupling unit.

[0014] Additionally, an FMCW lidar may be provided in which light having a wavelength different from the target wavelength among the first light and the second modified light is extinguished by repeatedly proceeding between one of the two or more grating sections and the other of the two or more grating sections.

[0015] Additionally, an FMCW lidar may be provided, wherein the polarization controller comprises: a control unit that controls the polarization state of the target light by changing the refractive index of the target light output from the resonator; and a polarization filter that removes optical noise from the target light output from the control unit.

[0016] Additionally, an FMCW lidar may be provided, wherein the polarization controller further comprises a polarization-maintaining fiber connected to the polarization filter to maintain the polarization state of the target light transmitted from the polarization filter.

[0017] Additionally, an FMCW lidar may be provided, comprising: a first control unit that receives the target light having linear polarization output from the resonator and outputs a first control light having elliptical polarization; and a second control unit connected to the first control unit that receives the first control light and outputs a second control light having linear polarization that intersects perpendicularly.

[0018] Additionally, an FMCW lidar may be provided, wherein one side of the polarizing filter is connected to the control unit, and the other side opposite to the one side is connected to the polarization maintaining fiber, and when the phase in which the one side is positioned is set as the reference phase, the other side is positioned tilted to a rotational phase rotated at a predetermined angle with respect to the center from the reference phase.

[0019] In addition, an FMCW lidar may be provided, wherein the above-mentioned predetermined angle is 40 degrees or more and 50 degrees or less.

[0020] In addition, a method for controlling the wavelength width of an FMCW lidar performed in an FMCW lidar may be provided, comprising: an FMCW laser transmission step of outputting a first light having a predetermined wavelength from a light source; a grating passage step of passing through a grating formed to selectively pass only a target light having a single target wavelength; a target wavelength laser output step of outputting the target light having the target wavelength that has passed through the grating; and a noise removal step of removing noise contained in the target light by changing the different refractive indices of the target light in a polarization controller that receives the target light.

[0021] Additionally, an FMCW lidar wavelength width control method may be provided, which further includes a pumping laser transmission step for outputting a second light having a smaller wavelength than the first light and changing the wavelength of the second light to the same wavelength as the first light, wherein the pumping laser transmission step is performed prior to the grating section passing step. Effects of the invention

[0022] According to embodiments of the present invention, there is an effect of being able to emit a laser close to a perfect single wavelength without increasing the output of the laser of the FMCW lidar infinitely. Brief explanation of the drawing

[0023] FIG. 1 is a drawing showing an FMCW lidar according to embodiments of the present invention. FIG. 2 is a conceptual diagram showing a resonator of an FMCW lidar according to a first embodiment of the present invention. FIG. 3 is a conceptual diagram showing the case where the optical amplification and transmission unit of the FMCW lidar according to the first embodiment of the present invention is changed to an optical waveguide. Figure 4 is a diagram showing the case where a second light is pumped into and combined with a first light. FIG. 5 is a conceptual diagram showing a polarization controller of an FMCW lidar according to embodiments of the present invention. FIG. 6 is a conceptual diagram showing how polarization is changed in a polarization controller of an FMCW lidar according to embodiments of the present invention. FIG. 7 is a conceptual diagram showing a resonator of an FMCW lidar according to a second embodiment of the present invention. Figure 8 is a flowchart illustrating the FMCW lidar wavelength control method. Figure 9 is a diagram showing the difference in wavelengths contained in the light output from the light source. Specific details for implementing the invention

[0024] Hereinafter, specific embodiments for implementing the technical concept of the present invention will be described in detail with reference to the drawings.

[0025] In addition, in describing the present invention, if it is determined that a detailed description of related known components or functions may obscure the essence of the invention, such detailed description is omitted.

[0026] Furthermore, when it is mentioned that one component is 'output,' 'transferred,' or 'connected' to another component, it should be understood that while the output, transfer, or connection may be direct to that other component, there may also be other components present in between.

[0027] The terms used in this specification are used merely to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0028] Furthermore, it should be noted in advance that the representations of parts, etc. in this specification are described based on the drawings, and may be depicted differently if the orientation of the object changes. For the same reason, some components in the attached drawings are exaggerated, omitted, or schematically depicted, and the size of each component does not entirely reflect its actual size.

[0029] Additionally, terms including ordinal numbers, such as first, second, etc., may be used to describe various components, but such components are not limited by such terms. These terms are used solely for the purpose of distinguishing one component from another.

[0030] The meaning of "comprising" as used in the specification is to specify certain characteristics, regions, integers, steps, actions, elements, and / or components, and does not exclude the existence or addition of other specific characteristics, regions, integers, steps, actions, elements, components, and / or groups.

[0031] Hereinafter, the specific configuration of the FMCW lidar (1) according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 4.

[0032] Referring to FIG. 1, the FMCW lidar (1) has a single linewidth target wavelength (λ tIt can output target light (T) that has a polarization state and maintains a polarization state. In other words, the FMCW lidar (1) can output a target wavelength (λ) of a single linewidth without increasing the intensity of the output light infinitely. t It can output a target light (T) that has a polarization state and maintains the polarization state. Such an FMCW lidar (1) may include a resonator (10), a polarization controller (20), and a controller (30).

[0033] Referring to FIG. 2, the resonator (10) has a single linewidth target wavelength (λ t It can output target light (T) having ). In other words, the resonator (10) can output a target wavelength (λ t The target light (T) can be output by canceling out light that is outside the range of destructive interference. This resonator (10) can be connected to a polarization controller (20). Additionally, the resonator (10) may include a light source section (100), a grating section (200), a transmission section (300), a pump (400), an optical coupling section (500), and an optical distribution section (600).

[0034] The light source unit (100) can output light having a predetermined wavelength. The light source unit (100) can emit light having a variety of wavelength spectra. Additionally, the light source unit (100) may be a laser diode (LD). The light source unit (100) may include a first light source (110) and a second light source (120).

[0035] The first light source (110) has a target wavelength (λ t A first light having a spectrum with a center wavelength of ) can be output. The first light output from such a first light source (110) can be transmitted to an optical coupling unit (500). For example, the first light output from the first light source (110) may have a wavelength spectrum such as 1549.9 nm, 1550 nm, 1550.1 nm, etc.

[0036] The second light source (120) can output a second light having a smaller wavelength than the first light. This second light source (120) can be connected to a pump (400). Additionally, the second light output from the second light source (120) can be pumped by the pump (400). In other words, the second light output from the second light source (120) can be pumped by the pump (400) and delivered to the optical coupling unit (500), and the second light can be transformed into a second modified light having the same wavelength as the first light. The second modified light can have the same wavelength as the first light at the optical coupling unit (500).

[0037] The grating section (200) has a single target wavelength (λ t A fine grating may be provided, formed to selectively allow only the target light (T) having ) to pass through. Such a grating portion (200) may be connected to an optical coupling portion (500). Additionally, the grating portion (200) may receive the first light and the second modified light transmitted from the optical coupling portion (500). Two or more grating portions (200) may be provided. Among the first light and the second modified light introduced into such a grating portion (200), the target wavelength (λ t Light having a wavelength different from that of the grid can be gradually extinguished by moving back and forth between one of the two or more grid sections (200) and the other of the two or more grid sections. The grid section (200) may include a first grid section (210) and a second grid section (220).

[0038] The first grating section (210) is positioned adjacent to the optical coupling section (500) and, among the first light and second modified light received from the optical coupling section (500), the target wavelength (λ t It can filter light excluding ). In other words, the first grating part (210) can filter the target wavelength (λ) among the first light and second modified light received from the optical coupling part (500). tIt can pass light having ). This first grating section (210) may include a plurality of fine gratings. In addition, the grating period, which is the distance between the plurality of fine gratings of the first grating section (210), is the target wavelength (λ t It can be formed to be identical to ). The first grid section (210) can be connected to the transmission section (300).

[0039] The second grating section (220) is a target wavelength (λ) of light transmitted from the first grating section (210). t It can filter light having a ) such that the second grating section (220) is positioned adjacent to the light distribution section (600) and among the light transmitted from the first grating section (210), the target wavelength (λ t Light having ) can be transmitted to the light distribution unit (600). In addition, the second grating unit (220) can transmit the target wavelength (λ) that is not completely filtered by the first grating unit (210). t Light having a predetermined wavelength difference from ) can be transmitted to the first grating section (210). This second grating section (220) may include a plurality of fine gratings. In addition, the grating period, which is the distance between the plurality of fine gratings of the second grating section (220), is the target wavelength (λ t It can be formed to be identical to ). The second grid section (220) can be connected to the transmission section (300).

[0040] Referring further to FIG. 3, the transmission unit (300) can connect between the optical coupling unit (500) and the optical distribution unit (600). This transmission unit (300) can transmit the first light and the second modified light transmitted from the optical coupling unit (500) to the grating unit (200). Additionally, the transmission unit (300) may include an optical amplification fiber (310) and an optical waveguide (320).

[0041] The optical amplification and transmission unit (310) can amplify the first light and the second modified light received from the optical coupling unit (500). This optical amplification and transmission unit (310) can transmit the target light (T) to the light distribution unit (600). Additionally, the optical amplification and transmission unit (310) can provide a path through which light is transmitted. The optical amplification and transmission unit (310) can be extended in one direction. This optical amplification and transmission unit (310) may be, for example, an EDF (erbium-doped fiber), an EDWA (erbium-doped waveguide amplifier), or a SOA (semiconductor optical amplifier). Additionally, one side of the optical amplification and transmission unit (310) may be connected to the first grating unit (210), and the other side opposite to the one side of the optical amplification and transmission unit (310) may be connected to the second grating unit (220).

[0042] The optical waveguide (320) can provide a path for transmitting the first light and the second modified light received from the optical coupling unit (500) in a certain area. This optical waveguide (320) can transmit the target light (T) to the optical distribution unit (600). Additionally, the optical waveguide (320) can be extended in one direction. This optical waveguide (320) can be placed in place of the optical amplification transmission unit (310). Additionally, one side of the optical waveguide (320) can be connected to the first grating unit (210), and the other side opposite to the one side of the optical waveguide (320) can be connected to the second grating unit (220).

[0043] Referring to FIG. 4, the pump (400) can transmit the second light (λp) output from the second light source (120) to the optical coupling part (500). In other words, the pump (400) can transmit the wavelength of the second light (λp) to the first light (λ t Energy can be transferred to the light amplification stage to be transformed into the same wavelength as ). The second light may be a pump light, and the pump may further include a configuration such as an isolator. One side of the pump (400) may be connected to the second light source (120), and the other side opposite to the one side may be connected to the optical coupling part (500).

[0044] The optical coupling unit (500) can combine the first light and the second light. In other words, the optical coupling unit (500) can couple the first light and the second light. The light combined in the optical coupling unit (500) is transmitted to the first transmission unit (310) and the second transmission unit (320), which are optical amplification units, so that the second light can be transformed into the second modified light. Here, the first light acts as a seed laser, and the second light (pump laser) acts as the absorbed light. In other words, the energy of the second light absorbed by the optical coupling unit (500) can be emitted by vibrating at a wavelength equal to the wavelength of the first light, which is the wavelength of the light passing through the optical coupling unit (500). In this way, the second light can be stimulated to emit (light is radiated) as the light of the first light and emitted as light of the same wavelength as the first light (emitted as the second modified light). This optical coupling part (500) can be connected to the first light source (110) and the second light source (120). Additionally, the optical coupling part (500) can be positioned so that light travels to the optical coupling part (500) ahead of the transmission part (300).

[0045] The light distribution unit (600) has a single target wavelength (λ) that has passed through the grating unit (200). t A target light (T) having ) can be transmitted in one direction. One side of this light distribution unit (600) may be connected to the grating unit (200), and the other side opposite to the one side may be connected to the polarization controller (20). Additionally, the light distribution unit (600) may be placed in the transmission unit (300). Since the target light (T) output from the light distribution unit (600) initially has a Gaussian energy distribution, it may exist in two parts: a central part with high energy intensity and a side part. These two lights may have linear polarization with directions horizontal to each other.

[0046] Referring to FIGS. 5 and 6, the polarization controller (20) can remove optical noise present in the target light (T) output from the resonator (10). This polarization controller (20) can be connected to the resonator (10). Additionally, the polarization controller (20) may include a control unit (700), a polarization filter (800), and a polarization maintaining fiber (900).

[0047] The control unit (700) can control the polarization of the target light (T) by changing the x-axis refractive index and the y-axis refractive index of the target light (T) output from the resonator (10) to be different from each other. This control unit (700) can change the polarization state of the target light (T) by compressing at least a portion of the optical fiber through which the target light (T) is transmitted. Additionally, the control unit (700) may include a first control unit (710), a second control unit (720), and a non-linear medium unit (730).

[0048] The first control unit (710) receives a target light (T) having linear polarization output from the resonator (10) and can output a first control light having elliptical polarization. In other words, the first control unit (710) can output a first control light having elliptical polarization by generating a difference in the speed of the electric and magnetic fields by adjusting the position inside the optical fiber through which the target light (T) is transmitted, as well as the x-axis refractive index and y-axis refractive index differently. The first control light output from the first control unit (710) passes through a non-linear medium unit (730) and then to the second control unit (720). Additionally, the first control unit (710) can be controlled by a controller (30).

[0049] The second control unit (720) receives two first control lights having different energies and can output a second control light having linear polarization that intersects perpendicularly. In other words, the second control unit (720) can generate a speed difference by adjusting the phase of the light transmitted by the first control light differently, and then output a second control light having linear polarization. The second control light output from this second control unit (720) can be transmitted to a polarization filter (800). Additionally, the second control unit (720) can be controlled by a controller (30).

[0050] The non-linear medium section (730) can rotate light of different light powers to different degrees. In other words, since the refractive index of the medium changes depending on the intensity of the light due to the Kerr effect, etc., even light that initially travels in parallel will be rotated into different phases if the intensities are different. This non-linear medium section (730) can be placed between the first control section (710) and the second control section (720).

[0051] The polarizing filter (800) can remove optical noise from the target light (T) output from the control unit (700). In other words, unwanted polarization can be blocked by the polarizing filter (800). One side of this polarizing filter (800) can be connected to the control unit (700), and the other side, which is opposite to the one side, can be connected to the polarization maintaining fiber (900). Additionally, when the phase in which one side of the polarizing filter (800) is positioned is set as the reference phase, the other side can be positioned to be tilted to a rotational phase rotated at a predetermined angle relative to the center from the reference phase. The predetermined angle at which the other side of the polarizing filter (800) is tilted can be 40 degrees or more and 50 degrees or less, for example, 45 degrees.

[0052] The polarization-maintaining fiber (900) can maintain the polarization state of the target light (T) transmitted from the polarization filter (800). This polarization-maintaining fiber (900) can be connected to the polarization filter (800). In other words, the polarization-maintaining fiber (900) can maintain the polarization state received from the polarization filter (800) by ensuring that no speed difference occurs when the light is transmitted. The polarization-maintaining fiber (900) can be extended in one direction.

[0053] The controller (30) can control the operation of the light source unit (100) so that light is output from the light source unit (100). By controlling the operation of the pump (400), the controller (30) can transmit the second light output from the second light source (120) to the optical coupling unit (500). Additionally, the controller (30) can control the operation of the adjustment unit (700) so that the polarization of the target light (T) output from the resonator (10) can be changed. In other words, the controller (30) can control the operation of the adjustment unit (700) so that the optical refractive index is changed by at least a part of the adjustment unit (700) pressurizing the optical fiber. Furthermore, the controller (30) can be implemented by a computing device including a microprocessor, and since the method of implementation is obvious to those skilled in the art, further detailed explanation is omitted.

[0054] Meanwhile, in addition to this configuration, an FMCW lidar (1) according to the second embodiment of the present invention may be provided. Hereinafter, the second embodiment of the present invention will be described with reference to FIG. 7. In describing the second embodiment, the differences when compared with the above-described embodiment will be described mainly, and the same descriptions and reference numerals will be taken from the above-described embodiment.

[0055] The resonator (10) of the FMCW lidar (1) according to the second embodiment of the present invention may not include a grating portion (200). In such a resonator (10), the first light and the second modified light received from the optical coupling portion (500) may continue to be transmitted along the transmission portion (300). Additionally, the resonator (10) may further include a coupler (801).

[0056] One side of the transmission unit (300) may be connected to the optical coupling unit (500) and the other side may be connected to the coupler (801) to form a ring. The first light and the second modified light transmitted from the optical coupling unit (500) may be rotated multiple times along this transmission unit (300). Additionally, the length of the ring formed by the transmission unit (300) is the target wavelength (λ t It can be provided with a length that is an integer multiple of ). While rotating multiple times along the transmission part (300), among the first light and the second modified light, the target wavelength (λ t Light other than ) can be canceled out through destructive interference.

[0057] The coupler (801) is a target wavelength (λ) of light transmitted from the transmission unit (300). t ) can separate light having ). For example, the coupler (801) can separate light having a target wavelength (λ) corresponding to 1% of the light transmitted from the transmission unit (300). t Light having ) can be separated. The light separated in this coupler (801) can be transmitted to a polarization controller (20).

[0058] Hereinafter, with reference to the drawings, an FMCW lidar wavelength control method (S10) according to a first embodiment of the present invention will be described. In describing the FMCW lidar wavelength control method (S10), the explanation will focus on the differences when compared with the above-described embodiment, and the same descriptions and reference numerals are adopted from the above-described embodiment.

[0059] Referring to FIG. 8, the FMCW lidar wavelength width control method (S10) can be performed by the FMCW lidar (1). This FMCW lidar wavelength width control method (S10) is a target wavelength (λ t It is possible to output a target light (T) having ). In other words, the FMCW lidar wavelength width control method (S10) can output a target wavelength (λ) without increasing the intensity of the output light infinitely. t A target light (T) having ) can be output. The FMCW lidar wavelength control method (S10) may include an FMCW laser transmission step (S100), a pumping laser transmission step (S200), a grating passing step (S300), a mirroring step (S400), a target wavelength laser output step (S500), and a noise removal step (S600).

[0060] In the FMCW laser transmission step (S100), a first light having a predetermined wavelength may be output from the light source unit (100). The first light output in this FMCW laser transmission step (S100) has a target wavelength (λ t It may have a spectrum with ) as the center wavelength. In addition, the FMCW laser transmission step (S100) may be performed before the pumping laser transmission step (S200). However, the present invention is not limited thereto and may be performed simultaneously with the pumping laser transmission step (S200).

[0061] In the pumping laser transmission step (S200), a second light having a smaller wavelength than the first light may be output. In this pumping laser transmission step (S200), the wavelength of the second light may be changed to the same wavelength as the first light. Additionally, the pumping laser transmission step (S200) may be performed before the grating section passing step (S300). In the pumping laser transmission step (S200), the second light output from the second light source (120) may be transmitted to the optical coupling section (500) by the pump (400). After the pumping laser transmission step (S200), the second light may be modified to the same wavelength as the first light.

[0062] In the grating section passing step (S300), a single target wavelength (λ t A target light (T) having ) can selectively pass through the grating section (200). In this grating section passing step (S300), light transmitted from the optical coupling section (500) can pass through the fine grating of the grating section (200).

[0063] In the mirroring step (S400), among the first light and the second modified light, the target wavelength (λ t Light excluding ) can be repeatedly transmitted between one of the two or more grating sections (200) and the other of the two or more grating sections (200). In this mirroring step (S400), among the first light and the second modified light that proceed repeatedly multiple times, the target wavelength (λ t Light excluding ) may be extinguished by destructive interference. Additionally, the mirroring step (S400) can be performed simultaneously with the grating part passing step (S300).

[0064] In the target wavelength laser output step (S500), the target wavelength (λ) that has passed through the grating part (200) t A target light (T) having ) can be output. The target light (T) output in the target wavelength laser output step (S500) can be transmitted to a polarization controller (20). In addition, the target light (T) output in the target wavelength laser output step (S500) may be in a linearly polarized state.

[0065] In the noise removal step (S600), the different refractive indices of the target light (T) are changed so that noise contained in the target light (T) can be removed. This noise removal step (S600) can be performed in a polarization controller (20) that receives the target light (T). Additionally, the noise removal step (S600) can be performed by sequentially passing the target light (T) through a control unit (700) that compresses at least a portion of the optical fiber and a polarization filter (800).

[0066] Below, the operation and effects of the FMCW lidar (1) having the configuration described above will be explained.

[0067] Referring to FIG. 9, the FMCW lidar (1) according to embodiments of the present invention has a target wavelength (λ) close to a complete single wavelength. t It can output a target light (T) having ). In other words, a target wavelength (λ1) desired by the user, which is included in the light output from the light source part (100) of the FMCW lidar (1). t By extinguishing light having a wavelength (λ2) that differs from ), the target wavelength (λ t Only target light (T) having ) can be output. By making the wavelength of the light output from this FMCW lidar (1) close to a perfect single wavelength, long-distance performance can be improved without increasing the intensity of the output light infinitely.

[0068] In addition, in the FMCW lidar (1), the target wavelength (λ) output from the first light source (110) t A first light having a spectrum with a center wavelength of ) and a second light having a shorter wavelength than the first light output from a second light source (120) can be coupled. The light coupled in the optical coupling unit is transmitted to the first transmission unit (310) and the second transmission unit (320), which are optical amplification units, so that the second light reaches the target wavelength (λ t It is transformed into a second modified light having the same wavelength as ) and the target wavelength (λ t Light having a ) can be induced to be emitted. For example, by coupling a first light having a spectrum with a center wavelength of 1550 nm output from a first light source (110) and a second light having a wavelength of 980 nm, the second light is transformed into light having a wavelength of 1550 nm at the optical coupling part (500), and the second transformed light with a wavelength of 1550 nm can be transmitted to the grating part (200) together with the first light.

[0069] Additionally, the target light (T) output from the resonator (10) can be polarized by changing the position inside the optical fiber and the x-axis refractive index and y-axis refractive index by the control unit (700). In other words, the controller (30) controls the operation of the control unit (700) so that at least a part of the control unit (700) compresses at least a part of the optical fiber through which the target light (T) is transmitted, thereby changing the polarization state of the target light (T) from linear polarization to elliptical polarization. This target light (T) can be transmitted to the polarization-maintaining fiber (900) with the changed polarization state maintained and optical noise removed.

[0070] Although the embodiments of the present invention have been described above as specific embodiments, they are merely examples and the present invention is not limited thereto, but should be interpreted as having the broadest scope in accordance with the technical concept disclosed in this specification. Those skilled in the art may implement patterns of shapes not specified by combining or substituting the disclosed embodiments, and this also does not deviate from the scope of the present invention. Furthermore, those skilled in the art may easily modify or alter the disclosed embodiments based on this specification, and it is evident that such modifications or alterations also fall within the scope of the rights of the present invention. Explanation of the symbols

[0071] 1: FMCW LiDAR 10: Resonator 100: Light source 110: First light source 120: Second light source 200: Grid section 210: 1st grid section 220: Second grid section 300: Optical transmission unit 310: 1st Delivery Unit 320: 2nd Delivery Unit 400: Pump 500: Optical coupling part 600: Optical distribution unit 20: Polarization controller 700: 1st control unit 720: Second control unit 800: Polarizing filter 801: Coupler 900: Polarization-maintaining fiber

Claims

Claim 1 FMCW LiDAR comprising: a resonator configured to output a target light having a single target wavelength; and a polarization controller for removing optical noise present in the target light output from the resonator, wherein the resonator comprises: a light source unit that outputs light having a predetermined wavelength; and two or more grating units that provide a fine grating formed such that the target light selectively passes through by the light output from the light source unit being transmitted back and forth, wherein the light source unit comprises a first light source that outputs a first light having a spectrum including the target wavelength and transmits it to the grating unit. Claim 2 In claim 1, the light source unit further includes a second light source that outputs a second light having a smaller wavelength than the first light, and the resonator further includes a pump that pumps the second light to be delivered to the first light, FMCW LiDAR. Claim 3 In claim 2, the FMCW light further comprises an optical coupling unit that combines the first light and the second light, wherein the optical coupling unit transforms the second light into a second modified light having the same wavelength as the first light by combining the second light with the first light. Claim 4 In claim 1, the resonator further comprises an optical amplification and transmission unit that optically amplifies and transmits the first light and the second modified light received from the optical coupling unit, and is an FMCW lidar. Claim 5 In claim 4, the light having a wavelength different from the target wavelength among the first light and the second modified light is extinguished by repeatedly proceeding between one of the two or more grating parts and the other of the two or more grating parts, FMCW LiDAR. Claim 6 In claim 1, the polarization controller comprises: a control unit that controls the polarization state of the target light by changing the refractive index of the target light output from the resonator; and a polarization filter that removes optical noise from the target light output from the control unit, FMCW lidar. Claim 7 In claim 6, the polarization controller further comprises a polarization-maintaining fiber connected to the polarization filter to maintain the polarization state of the target light transmitted from the polarization filter, and is an FMCW lidar. Claim 8 In claim 6, the control unit comprises: a first control unit that receives the target light having linear polarization output from the resonator and outputs a first control light having elliptical polarization; and a second control unit connected to the first control unit that receives the first control light and outputs a second control light having linear polarization that intersects perpendicularly with each other. Claim 9 In claim 7, the polarizing filter is an FMCW lidar in which one side is connected to the control unit and the other side opposite to the one side is connected to the polarization maintaining fiber, and when the phase in which the one side is positioned is set as the reference phase, the other side is positioned tilted to a rotational phase rotated at a predetermined angle with respect to the center from the reference phase. Claim 10 In claim 9, the above-mentioned predetermined angle is an FMCW LiDAR of 40 degrees or more and 50 degrees or less. Claim 11 A method for controlling the wavelength width of an FMCW lidar performed in an FMCW lidar, comprising: an FMCW laser transmission step of outputting a first light having a predetermined wavelength from a light source; a grating section passing step of passing through a grating section formed to selectively pass only a target light having a single target wavelength; a target wavelength laser output step of outputting the target light having the target wavelength that has passed through the grating section; and a noise removal step of removing noise contained in the target light by changing the different refractive indices of the target light in a polarization controller that receives the target light. Claim 12 In claim 11, the FMCW lidar wavelength width control method further comprises a pumping laser transmission step for outputting a second light having a smaller wavelength than the first light and changing the wavelength of the second light to the same wavelength as the first light, wherein the pumping laser transmission step is performed prior to the grating section passing step.

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