JP6250197B1 - Laser radar equipment - Google Patents

Abstract

A reference light source (113) that oscillates reference light having a wavelength different from that of the transmission light, an optical multiplexing coupler (114) that couples the oscillated reference light to one end of the optical fiber (206), and the transmission light and the reference light in the same direction A transmission / reception separating unit (106) emitted from the optical fiber (206) and the transmission / reception separating unit (106), an optical axis adjusting mechanism (109) for adjusting the optical axis of light passing therethrough, and transmission light And a partial reflection mirror (108) that transmits at least a part of the reference light, and an optical axis angle deviation detection that detects an optical axis angle deviation amount between the transmission light and the reference light that has passed through the partial reflection mirror (108). Unit (115) and a control unit (116) for controlling the optical axis adjustment mechanism (109) based on the optical axis angular deviation amount detected by the optical axis angular deviation detection unit (115).

Description

  The present invention relates to a laser radar device that radiates transmission light and receives reception light scattered by a target.

  In a conventional coherent laser radar apparatus, transmission light is pulsed by an acousto-optic (AO) element, amplified by an EDFA (Erbium Doped Fiber Amplifier), and then emitted from a fiber collimator (see, for example, Non-Patent Document 1).

`` Proceedings of 11th Coherent Laser Radar Conference '' by G. N. Pearson and J. Eacock (Malvern, Worcestershire, UK, July 2001), pp. 144-146

  On the other hand, in a coherent laser radar device as disclosed in Non-Patent Document 1, it is necessary to couple received light to an optical fiber in order to perform heterodyne detection. At this time, in order to perform a highly sensitive measurement while suppressing the loss of the received light, it is necessary to efficiently couple the received light to the optical fiber, and the optical axis of the receiving optical system with respect to the outgoing optical axis of the transmitted light. Need to match. When there is an optical axis angle shift, the coupling efficiency of received light to the optical fiber is greatly reduced, and therefore it is necessary to match the optical axes with an accuracy of μrad order. Therefore, it takes time to adjust the optical axis when assembling the apparatus. In addition, the optical axis is likely to be misaligned due to disturbance such as vibration, impact or temperature change, and it is difficult to improve the reliability of the apparatus.

  The present invention has been made to solve the above-described problems, and provides a laser radar device capable of easily adjusting the optical axes of transmission light and reception optical system with respect to a conventional configuration. It is an object.

  A laser radar device according to the present invention includes a transmission light emitting unit that emits transmission light, a reference light source that oscillates reference light having a wavelength different from that of the transmission light, and reference light oscillated by the reference light source at one end of the optical fiber. The first optical multiplexing unit to be coupled, the transmission light incident on the incident end opposed to the output end of the transmission light emitting unit, and the reference incident on the first incident / exit end opposed to the other end of the optical fiber A transmission / reception separating unit that emits light from the second incident / exit end, and a received light incident on the second incident / exit end, and the other end of the optical fiber and a transmission / reception separating unit. An optical axis adjustment unit that adjusts an optical axis of light passing therethrough, and a transmission / reception separation between the first incident emission end of the transmission light or between the emission end of the transmission light emission unit and the incidence end of the transmission / reception separation unit Placed on the optical axis of the second input / output end A partial reflection mirror that transmits a part of the transmission light and at least a part of the reference light, and an optical axis angle deviation detection unit that detects an optical axis angle deviation amount between the transmission light and the reference light transmitted through the partial reflection mirror; And a control unit that controls an adjustment amount in the optical axis adjustment unit based on the optical axis angle deviation amount detected by the optical axis angle deviation detection unit.

  According to this invention, since it comprised as mentioned above, the optical axis adjustment of transmission light and a reception optical system can be performed simply with respect to a conventional structure.

It is a figure which shows the structural example of the laser radar apparatus by Embodiment 1 of this invention. It is a figure which shows the structural example of the optical axis angle deviation detection part in Embodiment 1 of this invention. It is a figure which shows the structural example of the photon detection element in Embodiment 1 of this invention. It is a figure which shows the hardware structural example of the signal processing part and control part in Embodiment 1 of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration example of a laser radar apparatus according to Embodiment 1 of the present invention.
The laser radar device is a device that receives received light scattered by a target (for example, the atmosphere, fine particles or aerosol in the atmosphere, a flying object, a building, etc.) by radiating transmission light. In the following description, a coherent Doppler lidar device that measures wind speed by detecting Doppler shift using received light is used as the laser radar device. As shown in FIG. 1, the laser radar device includes a reference laser light source 101, an optical branching coupler (optical branching unit) 102, an optical modulator 103, an optical fiber amplifier 104, a laser amplifier 105, a transmission / reception separating unit 106, and a partial reflection mirror. 107, telescope (transmission / reception optical system) 108, optical axis adjustment mechanism (optical axis adjustment unit) 109, optical multiplexing coupler (second optical multiplexing unit) 110, photodetector 111, signal processing unit 112, reference light source 113, optical coupling A wave coupler (first optical multiplexing unit) 114, an optical axis angle deviation detection unit 115, and a control unit 116 are provided.

  An output end of the reference laser light source 101 and an input end of the optical branching coupler 102 are connected by an optical fiber 201. The first output end of the optical branching coupler 102 and the input end of the optical modulator 103 are connected by an optical fiber 202. The second output terminal of the optical branching coupler 102 and the first input terminal of the optical multiplexing coupler 110 are connected by an optical fiber 203. An output end of the optical modulator 103 and an input end of the optical fiber amplifier 104 are connected by an optical fiber 204. One end of the optical fiber 205 is connected to the output end of the optical fiber amplifier 104. One end of the optical fiber 206 is connected to the input / output end of the optical multiplexing coupler 114. In addition, an output end of the optical multiplexing coupler 114 and a second input end of the optical multiplexing coupler 110 are connected by an optical fiber 207. Further, an output end of the optical multiplexing coupler 110 and an input end of the photodetector 111 are connected by an optical fiber 208. The output end of the reference light source 113 and the input end of the optical multiplexing coupler 114 are connected by an optical fiber 209.

  The reference laser light source 101 oscillates with a CW (Continuous Wave) laser beam having a constant frequency as a reference laser beam. As the reference laser light source 101, for example, a DFB (Distributed Feed-Back) fiber laser or a DFB-LD (Laser Diode) can be used. The reference laser light oscillated by the reference laser light source 101 is coupled to the optical fiber 201 and propagates to the optical branching coupler 102.

  The optical branching coupler 102 splits the reference laser light oscillated by the reference laser light source 101 into two branches. One reference laser beam branched by the optical branching coupler 102 is coupled to the optical fiber 202 and propagates to the optical modulator 103. The other reference laser beam branched by the optical branching coupler 102 is coupled to the optical fiber 203 and propagates to the optical multiplexing coupler 110.

  The optical modulator 103 modulates one reference laser beam (transmission seed beam) branched by the optical branching coupler 102. At this time, the optical modulator 103 performs pulsing and frequency shifting on the transmission seed light. As the optical modulator 103, for example, an acousto-optic modulator (AOM) can be used. By using the AOM, pulse generation by cutting out the transmission seed light with a time gate, frequency shift, and the like. Can be performed simultaneously. The transmission seed light modulated by the optical modulator 103 is coupled to the optical fiber 204 and propagates to the optical fiber amplifier 104.

  The optical fiber amplifier 104 amplifies the transmission seed light modulated by the optical modulator 103. As the optical fiber amplifier 104, an amplifier suitable for the wavelength band of the transmission seed light is used. For example, when the wavelength of the transmission seed light is in the 1.06 μm band, the optical fiber amplifier 104 may be an amplifier using an Nd (Neodymium) -doped fiber or a Yb (Yterbium) -doped fiber. For example, when the wavelength of the transmission seed light is in the 1.55 μm band, an amplifier using an Er (Erbium) doped fiber can be used as the optical fiber amplifier 104. The transmission seed light amplified by the optical fiber amplifier 104 is coupled to the optical fiber 205 and emitted to the laser amplifier 105 side.

  The laser amplifier 105 is a spatial amplifier that amplifies the transmission seed light amplified by the optical fiber amplifier 104 with the incident end facing the other end (outgoing end) of the optical fiber 205. As the laser amplifier 105, a laser medium suitable for the wavelength band of the transmission seed light is used. For example, when the wavelength of the transmission seed light is in the 1.06 μm band, a crystal, glass, ceramic, or the like to which Nd or Yb is added can be used. Further, when the wavelength of the transmitted seed light is in the 1.55 μm band, a crystal, glass, ceramic or the like to which Er is added can be used. As the shape of the laser medium, a rod-type, disk-type or planar waveguide-type element can be used. When these elements are used, the laser amplifier 105 collimates the transmission seed light emitted from the optical fiber 205 with a collimator lens or the like, then condenses it with an optical system such as a lens and enters the element. The laser amplifier 105 collimates the transmission seed light that has passed through the element with a collimator lens or the like, and then emits the transmitted light to the transmission / reception separating unit 106 side as transmission light.

The optical fiber amplifier 104 and the laser amplifier 105 constitute an amplifier 117 that amplifies the reference laser light modulated by the optical modulator 103 and uses it as transmission light.
The reference laser light source 101, the optical branching coupler 102, the optical modulator 103, the optical fiber amplifier 104, and the laser amplifier 105 constitute a transmission light emitting unit 118 that emits transmission light.

  The transmission / reception separating unit 106 transmits the transmission light incident on the incident end opposed to the emission end of the laser amplifier 105 and the reference light incident on the first incident / exit end opposed to the other end of the optical fiber 206. The light is emitted from the two incident / exit ends. Further, the transmission / reception separating unit 106 emits the received light incident on the second incident / exit end from the first incident / exit end. The transmission / reception separating unit 106 is constituted by a spatial optical element, and an optical circulator using a combination of a polarizer and a wave plate or a Faraday element can be used.

  The partial reflection mirror 107 is disposed on the optical axis of the second incident / exit end in the transmission / reception separating unit 106 and transmits a part of the transmission light and at least a part of the reference light. The partial reflection mirror 107 has a part (approximately several percent) transmittance with respect to the wavelength of the transmission light, and a part or all (several percent to 100%) of transmission with respect to the wavelength of the reference light. Have a rate. Note that the transmittance of the partial reflection mirror 107 with respect to the wavelength of the transmission light is desirably as small as possible in order to suppress loss of the transmission light and the reception light.

  The telescope 108 irradiates the transmission light reflected by the partial reflection mirror 107 toward the atmosphere, and receives the reception light scattered by the target (aerosol) existing in the atmosphere with respect to the transmission light. As the telescope 108, for example, a collimator capable of making the transmitted light to be irradiated substantially parallel and adjusting the focal length can be used. In addition, the telescope 108 preferably has a large aperture in order to reduce the divergence angle of the transmitted light to be irradiated and increase the reception efficiency. The telescope 108 converts the received light received into substantially parallel light, and then emits it to the partial reflection mirror 107 side.

  The optical axis adjustment mechanism 109 is disposed between the other end of the optical fiber 206 and the first incident / exit end of the transmission / reception separating unit 106, and adjusts the optical axis of the passing light (received light and reference light). As the optical axis adjustment mechanism 109, an optical element such as a wedge prism or a reflection mirror capable of changing the angle of the optical axis can be used. Here, when a wedge prism is used as the optical axis adjustment mechanism 109, two optical prisms are used and rotated in the circumferential direction, so that the optical axis can be set at an arbitrary angle within the emission angle range determined by the deflection angle of the wedge prism. Can be changed. Further, when a reflection mirror is used as the optical axis adjustment mechanism 109, one may be used to perform angle control in the biaxial direction, or two may be used to perform angle control in the uniaxial direction. Good. Note that an actuator using a motor, a piezoelectric element, or the like can be used as a driving mechanism for the optical element. Here, the configuration in which two wedge prisms are rotated by a motor makes it easy to perform minute angle control with a simple configuration. Further, the deflection angle of the wedge prism or the step angle of the motor is set to a suitable value so that the required angular accuracy can be obtained. The received light that has passed through the optical axis adjustment mechanism 109 is condensed by a condensing optical system (not shown) such as a fiber collimator, and then coupled to the optical fiber 206 via the optical multiplexing coupler 114 and the optical fiber 207. Propagated to the optical multiplexing coupler 110.

  The optical multiplexing coupler 110 combines the other reference laser light (local oscillation light) branched by the optical branching coupler 102 and the received light emitted from the transmission / reception separating unit 106 and passed through the optical axis adjusting mechanism 109 and the optical multiplexing coupler 114. Combine (mix). The light combined by the optical multiplexing coupler 110 is coupled to the optical fiber 208 and propagates to the photodetector 111.

  The photodetector 111 receives the light combined by the optical combining coupler 110 and detects a beat signal between the received light and the local oscillation light.

  The signal processing unit 112 extracts information about the target from the beat signal detected by the photodetector 111. Examples of the information on the target include information indicating received light intensity, round trip time, or Doppler frequency. In addition, the signal processing unit 112 calculates a motion specification of the target from the extracted information regarding the target. Examples of the target motion specifications include a distance to a target or a velocity distribution.

  The reference light source 113 oscillates with laser light having a wavelength different from that of the transmission light emitted from the transmission light emitting unit 118 as reference light. For example, a semiconductor laser (Laser Diode) or a DFB fiber laser can be used as the reference light source 113. Here, when a fiber output type laser is used as the reference light source 113, the connection with the optical multiplexing coupler 114 is facilitated by optical connector connection or fusion connection of optical fibers. The reference light oscillated by the reference light source 113 is coupled to the optical fiber 209 and propagates to the optical multiplexing coupler 114.

  The optical multiplexing coupler 114 couples the reference light oscillated by the reference light source 113 to one end of the optical fiber 206.

  The optical axis angle deviation detection unit 115 detects the amount of optical axis angle deviation between the transmission light transmitted through the partial reflection mirror 107 and the reference light. For example, as shown in FIG. 2, the optical axis angle deviation detection unit 115 includes a lens 1151, a light detection element 1152, and a calculation unit 1153.

The lens 1151 condenses incident transmission light and reference light.
The light detection element 1152 is a two-dimensional light detection element that receives the transmission light and the reference light collected by the lens 1151. Note that the light detection element 1152 is arranged at a position away from the lens 1151 by the focal length f of the lens 1151. As the light detection element 1152, for example, a four-quadrant light detector or a camera-type element such as a CCD can be used. Here, when a four-quadrant light detector is used as the light detection element 1152, a small and simple configuration can be obtained.
The calculation unit 1153 calculates the optical axis angle deviation amount from the positions of the transmission light and the reference light received by the light detection element 1152.

  The control unit 116 controls the adjustment amount in the optical axis adjustment mechanism 109 based on the optical axis angle deviation amount detected by the optical axis angle deviation detection unit 115.

Next, an operation example of the laser radar device according to the first embodiment will be described.
In the operation example of the laser radar apparatus, first, the reference laser light source 101 oscillates with CW laser light having a constant frequency as reference laser light. In order to improve the accuracy of coherent detection, the spectral width of the reference laser beam is preferably as narrow as possible, and for example, a laser beam of 100 kHz or less is suitable as the reference laser beam. The reference laser light oscillated by the reference laser light source 101 is coupled to the optical fiber 201 and propagates to the optical branching coupler 102.

  Next, the optical branching coupler 102 splits the reference laser light oscillated by the reference laser light source 101 into two. One reference laser beam branched by the optical branching coupler 102 is coupled to the optical fiber 202 and propagates to the optical modulator 103. The other reference laser beam branched by the optical branching coupler 102 is coupled to the optical fiber 203 and propagates to the optical multiplexing coupler 110.

  Next, the optical modulator 103 modulates one reference laser beam (transmission seed beam) branched by the optical branching coupler 102. At this time, the optical modulator 103 performs pulsing and frequency shifting on the transmission seed light. The intermediate frequency added by the frequency shift is usually a frequency of about several tens to several hundreds of MHz, and a suitable value for the laser radar device is selected. The transmission seed light modulated by the optical modulator 103 is coupled to the optical fiber 204 and propagates to the optical fiber amplifier 104.

  Next, the optical fiber amplifier 104 amplifies the transmission seed light modulated by the optical modulator 103. The transmission seed light amplified by the optical fiber amplifier 104 is coupled to the optical fiber 205 and emitted to the laser amplifier 105 side. As described above, by using the optical fiber amplifier 104, the intensity of the transmitted light is increased and the intensity of the received light can be increased, so that the measurement accuracy and the measurable distance are improved.

  On the other hand, in the optical fiber, stimulated Brillouin scattering, which is a non-linear phenomenon, occurs when laser light having a certain intensity or more is incident. Therefore, the intensity of the laser beam that can enter the optical fiber is limited. A general optical fiber has a gain bandwidth of stimulated Brillouin scattering of about several tens to 100 MHz, and a coherent Doppler lidar apparatus using a narrow linewidth laser beam is likely to cause stimulated Brillouin scattering. Therefore, normally, the intensity of the laser beam to be output is adjusted by limiting the pumping power input to the optical fiber amplifier 104 so that stimulated Brillouin scattering does not occur. As described above, since the intensity of the transmission light is limited only by the optical fiber amplifier 104, the measurement accuracy and the measurable distance are not sufficiently improved by increasing the intensity of the transmission light. Therefore, in addition to the optical fiber amplifier 104, a laser amplifier 105 is used.

  The laser amplifier 105 further amplifies the transmission seed light amplified by the optical fiber amplifier 104. This laser amplifier 105 is a spatial amplifier, and by setting the power density appropriately, nonlinear phenomena can be suppressed and the intensity of transmitted light can be increased as compared with the optical fiber amplifier 104. Thus, by using the optical fiber amplifier 104 and the laser amplifier 105 in combination, the intensity of the transmitted light is increased and the intensity of the received light can be increased, so that the measurement accuracy and the measurable distance are improved. The transmission seed light amplified by the laser amplifier 105 is emitted to the transmission / reception separating unit 106 side.

  Next, the transmission / reception separating unit 106 emits the transmission seed light (transmission light) amplified by the laser amplifier 105 to the partial reflection mirror 107 side.

  Next, the partial reflection mirror 107 transmits a part of the transmission light emitted by the transmission / reception separating unit 106 and reflects the rest to the telescope 108 side. Here, since the partial reflection mirror 107 has a transmittance of about several percent with respect to the wavelength of the transmission light, most of the transmission light incident on the partial reflection mirror 107 is reflected to the telescope 108 side. .

  Next, the telescope 108 irradiates the transmission light reflected by the partial reflection mirror 107 toward the atmosphere, and receives the reception light scattered by the target (aerosol) existing in the atmosphere with respect to the transmission light. The received light received by the telescope 108 is converted into substantially parallel light and then emitted to the partial reflection mirror 107 side.

  Next, the partial reflection mirror 107 reflects the reception light emitted from the telescope 108 toward the transmission / reception separating unit 106 side. That is, since the received light coming from the telescope 108 has almost the same wavelength as the transmitted light, most of the reflected light is reflected to the transmission / reception separating unit 106 side.

  Next, the transmission / reception separating unit 106 emits the reception light reflected by the partial reflection mirror 107 to the optical axis adjustment mechanism 109 side.

  Next, the optical axis adjusting mechanism 109 adjusts the optical axis of the received light emitted by the transmission / reception separating unit 106. The received light whose optical axis is adjusted by the optical axis adjusting mechanism 109 is condensed by a condensing optical system such as a fiber collimator and then coupled to the optical fiber 206 via the optical multiplexing coupler 114 and the optical fiber 207. Propagated to the optical multiplexing coupler 110.

  Next, the optical multiplexing coupler 110 receives the other reference laser beam (local oscillation light) branched by the optical branching coupler 102 and the received light that has been emitted by the transmission / reception separating unit 106 and passed through the optical axis adjusting mechanism 109 and the optical multiplexing coupler 114. Are combined (mixed). The light combined by the optical multiplexing coupler 110 is coupled to the optical fiber 208 and propagates to the photodetector 111.

  Next, the photodetector 111 receives the light combined by the optical combining coupler 110 and detects a beat signal between the received light and the local oscillation light. Here, the received light is subjected to a frequency shift by the optical modulator 103 and a Doppler shift accompanying the movement of the aerosol. Therefore, the Doppler shift can be obtained by analyzing the frequency of the beat signal detected by the photodetector 111.

  Next, the signal processing unit 112 extracts information on the target from the beat signal detected by the photodetector 111. In addition, the signal processing unit 112 calculates a motion specification of the target from the extracted information regarding the target. In addition, since the process which calculates the motion specification of a target from the information regarding a target is a well-known technique, detailed description is abbreviate | omitted.

Here, it is necessary to couple the received light that has passed through the optical axis adjusting mechanism 109 to the optical fiber 206. However, if there is a deviation between the outgoing optical axis of the transmitted light and the optical axis of the received optical system, the received optical system The collected received light is not incident on the core of the optical fiber 206, and the coupling efficiency to the optical fiber 206 is reduced. As a result, the intensity of the received light decreases and the detection sensitivity of the laser radar device decreases.
Since the received light is collected by the condensing optical system and is incident on the optical fiber 206, it is particularly necessary to accurately match the angles of the outgoing optical axis of the transmitted light and the optical axis of the receiving optical system. Although it depends on the beam diameter, it is usually necessary to match the optical axis angles with an accuracy of μrad order.

The outgoing optical axis of the transmitted light is the optical axis on the optical path from when the transmitted light emitted from the laser amplifier 105 is irradiated into the atmosphere via the transmission / reception separating unit 106, the partial reflection mirror 107, and the telescope 108. Point to. The optical axis of the reception optical system is an optical axis of reception light that can be ideally coupled to the optical fiber 206. In FIG. 1, the telescope 108, the partial reflection mirror 107, the transmission / reception separating unit 106, and the optical axis adjustment The optical axis on the optical path from the mechanism 109 to the optical fiber 206 is included.
Here, since the optical axis of the receiving optical system is an optical axis that can be ideally coupled to the optical fiber 206 as described above, it coincides with the optical axis when laser light is emitted from the optical fiber 206. Further, in order to make the outgoing optical axis of the transmission light coincide with the optical axis of the reception optical system, the optical axis of the transmission light and the optical fiber 206 on the path after the transmission / reception separating unit 106, the partial reflection mirror 107 and the telescope 108. What is necessary is just to make the optical axis of the laser beam radiate | emitted from the light source correspond.

Therefore, in the laser radar device according to the first embodiment, the outgoing light axis of the transmission light and the optical axis of the reception optical system are matched using the reference light.
That is, first, the reference light source 113 oscillates with laser light having a wavelength different from that of the transmission seed light (transmission light) emitted from the laser amplifier 105 as reference light. The reference light oscillated by the reference light source 113 is coupled to the optical fiber 209 and propagates to the optical multiplexing coupler 114.

  Next, the optical multiplexing coupler 114 couples the reference light oscillated by the reference light source 113 to one end of the optical fiber 206. Thereafter, since the reference light is emitted from the other end of the optical fiber 206, the optical axis of the reference light coincides with the optical axis of the reception optical system.

  Further, by setting the reference light to a wavelength different from that of the transmission light, it is possible to prevent the reference light from being mixed into the reception light caused by reflection by the optical system, and noise can be reduced. Therefore, the wavelength of the reference light may be a different wavelength band from the frequency band detected by the photodetector 111. When a visible laser light source is used as the reference light source 113, the reference light can be used as guide light for the optical axis of the receiving optical system when the apparatus is assembled.

Next, the optical axis adjustment mechanism 109 adjusts the optical axis of the reference light emitted from the optical fiber 206.
Next, the transmission / reception separating unit 106 emits the reference light whose optical axis is adjusted by the optical axis adjusting mechanism 109 to the partial reflection mirror 107 side. That is, the transmission / reception separating unit 106 emits the reference light in the same direction as the transmission light.
When a polarization separation type optical system is used as the transmission / reception separating unit 106, the polarization direction of the reference light is set so that the reference light is reflected toward the partial reflection mirror 107 by the transmission / reception separating unit 106. The loss of reference light can be reduced, and the output required for the reference light source 113 can be reduced. Further, when the wavelength bands of the transmission light and the reference light are greatly different, the optical element used in the transmission / reception separating unit 106 may have wavelength selectivity.

  Next, the partial reflection mirror 107 transmits at least a part of the reference light emitted by the transmission / reception separating unit 106.

  Next, the optical axis angle deviation detection unit 115 detects the amount of optical axis angle deviation between the transmission light transmitted through the partial reflection mirror 107 and the reference light. Here, since the optical axis of the reference light and the optical axis of the reception optical system match, the optical axis angle of the transmission light and the reception optical system is detected by detecting the amount of optical axis angle deviation between the transmission light and the reference light. The amount of deviation can be detected.

The detailed operation of the optical axis angle deviation detection unit 115 will be described below.
As shown in FIG. 2, first, the lens 1151 condenses incident transmission light and reference light. Next, the light detection element 1152 receives the transmission light and the reference light collected by the lens 1151. Next, the calculation unit 1153 calculates the optical axis angle deviation amount from the positions of the transmission light and the reference light received by the light detection element 1152.
Here, when the optical axes of the transmission light and the reference light match, the center positions of the focused spots on the light detection element 1152 match. On the other hand, when there is an angle shift between the optical axes of the transmission light and the reference light, a condensed spot appears at different positions. Therefore, by measuring the center position of the condensing spot of the transmission light and the reference light on the light detection element 1152, the optical axis angle deviation amount between the transmission light and the reference light can be measured. The center position of the focused spot can be obtained by calculating the center of gravity, and the angle deviation Δθ of the optical axis is expressed by the following equation (1). In Expression (1), Δd is the distance between the center positions of the condensing spots of the transmission light and the reference light on the light detection element 1152.
Δθ = arctan (Δd / f) (1)

Note that the condensing spot between the transmission light and the reference light can be distinguished by, for example, a spatial separation method using a wavelength difference between the transmission light and the reference light.
In the method using the wavelength difference between the transmission light and the reference light, a four-quadrant light detector is used as the light detection element 1152, and, for example, as shown in FIG. You may divide the light-receiving object inside and outside the four-quadrant light detector. In the configuration of FIG. 3, in the four-quadrant light detector, a reference light receiving region 301 is provided on the inner side to receive the reference light focusing spot 302, and a transmission light receiving region 303 is provided on the outer side to collect the transmitted light. The light spot 304 is received. This configuration is, for example, a method of providing a wavelength separation filter having a spatial distribution in the front stage of a four-quadrant photodetector, or forming a filter film having a wavelength characteristic on the surface of the four-quadrant photodetector. Can be realized. Further, by making the wavelength of the reference light shorter than the wavelength of the transmission light, the diameter of the condensing spot of the reference light can be made smaller than the diameter of the condensing spot of the transmission light. With this configuration, it is possible to detect the optical axis angle deviation between the transmission light and the reference light with a small and simple configuration. Further, when the wavelength range of the transmission light and the reference light is greatly different, a combination of light receiving elements having different sensitivity wavelength ranges in the light receiving region 301 of the reference light and the light receiving region 303 of the transmission light is used as the light detection element 1152. It is also possible to use one having a different configuration.
In addition, when it is difficult to spatially separate the condensing spot of the transmission light and the reference light, a method in which the reference light is temporally separated from the transmission light by performing a pulse operation can be used. By emitting the reference light between the pulses of the transmission light, the transmission light condensing spot 304 and the reference light condensing spot 302 appear alternately on the light detection element 1152. Therefore, by dividing the light reception signal at the light detection element 1152 at time intervals, the condensing spot 304 of the transmission light and the condensing spot 302 of the reference light can be distinguished and detected.

Further, a reduction optical system may be provided between the partial reflection mirror 107 and the optical axis angle deviation detector 115 or between the lens 1151 and the light detection element 1152 in the optical axis angle deviation detector 115. Here, when a reduction optical system having a magnification of M times is used, the optical axis angle deviation becomes M times, so that the detection accuracy of the optical axis angle deviation amount can be improved. In addition, since the focal length of the lens 1151 necessary for obtaining a constant detection accuracy of the optical axis angle deviation amount can be shortened, the optical axis angle deviation detection unit 115 can be configured in a small size.
The optical axis angle deviation detection unit 115 is adapted to meet the conditions of the reception optical system so as to obtain the accuracy necessary for detecting the amount of angle deviation necessary for preventing the reduction of the coupling efficiency of the received light to the optical fiber 206. Composed.

  Next, the control unit 116 controls the adjustment amount in the optical axis adjustment mechanism 109 based on the optical axis angle deviation amount detected by the optical axis angle deviation detection unit 115. That is, the control unit 116 changes the optical axis of the reference light by the optical axis adjustment mechanism 109 so that the optical axis angle deviation amount between the transmission light and the reference light becomes small. In this way, by reducing the amount of optical axis angle deviation between the transmitted light and the reference light, it is possible to prevent a decrease in the coupling efficiency of the received light to the optical fiber 206 and to prevent a decrease in the intensity of the received light. A decrease in detection sensitivity of the laser radar device can be prevented. In addition, since the optical axes of the transmission light and the reception optical system can be adjusted according to the optical axis angle deviation detected by the optical axis angle deviation detector 115, the optical axis can be easily adjusted when the apparatus is assembled. Furthermore, by applying an automatic adjustment mechanism that uses feedback-type control, etc., even if an optical element is misaligned due to disturbances such as vibration, shock, or temperature change, the transmitted light and the received optical system light Since the axial angle deviation can be reduced, the reliability of the apparatus can be improved.

  As described above, according to the first embodiment, the transmission light emitting unit 118 that emits the transmission light, the reference light source 113 that oscillates the reference light having a wavelength different from that of the transmission light, and the reference light source 113 oscillates. An optical multiplexing coupler 114 that couples the reference light to one end of the optical fiber 206, a transmission light incident on an incident end opposite to the emission end of the transmission light emitting unit 118, and a first opposite to the other end of the optical fiber 206. A transmission / reception separating unit 106 that emits the reference light input to the input / output end of the first light from the second input / output end and outputs the received light incident on the second input / output end from the first input / output end; An optical axis adjustment mechanism 109 that adjusts the optical axis of the light passing therethrough and is arranged between the other end of the optical fiber 206 and the first incident / exit end of the transmission / reception separation unit 106; Input / output end A partial reflection mirror 107 that is disposed on the optical axis and transmits a part of the transmission light and at least a part of the reference light, and detects an optical axis angle shift amount between the transmission light and the reference light transmitted through the partial reflection mirror 107 Since the optical axis angle deviation detection unit 115 and the control unit 116 that controls the adjustment amount in the optical axis adjustment mechanism 109 based on the optical axis angle deviation amount detected by the optical axis angle deviation detection unit 115 are provided. On the other hand, the optical axis angle deviation amount between the transmission light and the reception optical system can be easily reduced. As a result, it is possible to prevent a decrease in the coupling efficiency of the received light to the optical fiber 206, and it is possible to prevent a decrease in the intensity of the received light, thereby preventing a decrease in detection sensitivity of the laser radar device. In addition, the adjustment for suppressing the optical axis angle shift amount between the transmission light and the reception optical system becomes easy, and the optical axis adjustment at the time of assembling the apparatus can be simplified. Furthermore, by using automatic control or the like, even when an optical element misalignment occurs due to disturbances such as vibration, shock, or temperature change, the optical axis angular misalignment between the transmitted light and the receiving optical system can be reduced. Can improve the reliability.

  In the above description, the optical axis adjustment mechanism 109 is disposed between the other end (input / output end) of the optical fiber 206 and the first input / output end of the transmission / reception separating unit 106, and the optical axis of the reception optical system is transmitted light. It is changed to match the optical axis. However, the present invention is not limited to this, and the optical axis adjustment mechanism 109 is disposed between the emission end of the laser amplifier 105 and the incident end of the transmission / reception separating unit 106 so that the optical axis of the transmission light coincides with the optical axis of the reception optical system. It may be changed as follows.

  In the above, a spatial type is used as the optical axis adjustment mechanism 109, but a mechanism for directly changing the position or angle of the optical fiber 206 may be used. Further, when a lens or the like is used, a mechanism for changing the position of the lens may be used.

  In the above description, a coherent Doppler lidar device is used as the laser radar device. However, the present invention is not limited to this, and the same applies to other laser radar devices that transmit laser light and receive scattered light from a target. Applicable.

Finally, with reference to FIG. 4, an example of the hardware configuration of the signal processing unit 112 and the control unit 116 in the first embodiment will be described. In addition, although the hardware structural example of the control part 116 is demonstrated below, it is the same also about the signal processing part 112. FIG.
The function in the control unit 116 is realized by the processing circuit 51. As shown in FIG. 4A, the processing circuit 51 is a CPU (Central Processing Unit, a central processing unit, a processing unit that executes a program stored in the memory 53, as shown in FIG. 4B, even if it is dedicated hardware. , An arithmetic device, a microprocessor, a microcomputer, a processor, or a DSP (Digital Signal Processor) 52.

  When the processing circuit 51 is dedicated hardware, the processing circuit 51 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), or an FPGA (Field Programmable Gate). Array) or a combination thereof.

  When the processing circuit 51 is the CPU 52, the function of the control unit 116 is realized by software, firmware, or a combination of software and firmware. Software and firmware are described as programs and stored in the memory 53. The processing circuit 51 implements the function of the control unit 116 by reading and executing the program stored in the memory 53. That is, the control unit 116 performs an operation of controlling the adjustment amount in the optical axis adjustment mechanism 109 based on the optical axis angle deviation amount detected by the optical axis angle deviation detection unit 115 when executed by the processing circuit 51. A memory 53 is provided for storing a program to be executed as a result. These programs can also be said to cause a computer to execute the procedures and methods of the control unit 116. Here, the memory 53 is, for example, a nonvolatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable ROM), or an EEPROM (Electrically EPROM). And a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD (Digital Versatile Disc), and the like.

  In the present invention, any constituent element of the embodiment can be modified or any constituent element of the embodiment can be omitted within the scope of the invention.

  The laser radar device according to the present invention can easily adjust the optical axes of the transmission light and the reception optical system, and receives the reception light scattered by the target by irradiating the transmission light. Suitable for use in laser radar devices and the like.

  DESCRIPTION OF SYMBOLS 101 Reference laser light source, 102 Optical branch coupler (optical branch part), 103 Optical modulator, 104 Optical fiber amplifier, 105 Laser amplifier, 106 Transmission / reception separation part, 107 Partial reflection mirror, 108 Telescope (transmission / reception optical system), 109 Optical axis Adjustment mechanism (optical axis adjustment unit), 110 optical multiplexing coupler (second optical multiplexing unit), 111 photo detector, 112 signal processing unit, 113 reference light source, 114 optical multiplexing coupler (first optical multiplexing unit), 115 Optical axis angle deviation detection unit, 116 control unit, 117 amplifier, 118 transmission light emitting unit, 201-209 optical fiber, 1151 lens, 1152 photodetection element, 1153 calculation unit.

Claims (5)

A transmission light emitting section for emitting transmission light;
A reference light source that oscillates a reference light having a wavelength different from that of the transmission light;
A first optical multiplexing unit for coupling reference light oscillated by the reference light source to one end of an optical fiber;
The transmission light incident on the incident end opposed to the emission end in the transmission light emitting portion and the reference light incident on the first incident / exit end opposed to the other end of the optical fiber are second incident / exit ends. And a transmission / reception separating unit that emits the received light incident on the second incident / exit end from the first incident / exit end,
Between the other end of the optical fiber and the first entrance / exit end of the transmission / reception separating unit, or between the exit end of the transmission light emitting unit and the entrance end of the transmitting / receiving separation unit, An optical axis adjustment unit for adjusting the optical axis;
A partial reflection mirror that is disposed on the optical axis of the second incident / exit end in the transmission / reception separating unit, and transmits a part of the transmission light and at least a part of the reference light;
An optical axis angle deviation detector for detecting an optical axis angle deviation amount between the transmission light and the reference light transmitted through the partial reflection mirror;
A laser radar device comprising: a control unit that controls an adjustment amount in the optical axis adjustment unit based on an optical axis angle deviation amount detected by the optical axis angle deviation detection unit. The optical axis angle deviation detector is
A lens for condensing incident transmission light and reference light;
A light detecting element for receiving the transmission light and the reference light collected by the lens;
The laser radar device according to claim 1, further comprising: a calculation unit that calculates the optical axis angle deviation amount from the positions of the transmission light and the reference light received by the light detection element. The laser radar device according to claim 2, wherein the light detection element has a light receiving area for transmission light and a light receiving area for reference light. The laser radar device according to claim 1, wherein the reference light source is a visible laser light source. The transmission light emitting unit is
A reference laser light source for oscillating the reference laser light;
An optical branching unit that splits the reference laser light oscillated by the reference laser light source into two parts;
An optical modulator that modulates one reference laser beam branched by the optical branching unit;
An amplifier that amplifies the reference laser light modulated by the optical modulator and uses it as the transmission light;
A transmission / reception optical system that irradiates transmission light reflected by the partial reflection mirror and receives reception light scattered by a target with respect to the transmission light;
A second optical multiplexing unit that combines the other reference laser beam branched by the optical branching unit and the received light output from one end of the optical fiber;
A photodetector that receives the light combined by the second optical multiplexing unit and detects a beat signal;
The laser radar device according to claim 1, further comprising: a signal processing unit that extracts information on the target from a beat signal detected by the photodetector.

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