JP2015210098A - Laser radar device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coaxial novel laser radar device.SOLUTION: The laser radar device two-dimensionally deflects laser light from a laser light source 10 by deflecting means 18 and emits the light as irradiation laser light SRL in a parallel flux state through an objective lens 20. Backward laser light BKL diverted by the objective lens 20 and deflected by the deflecting means 18 is condensed by a condensing lens system 32, 34 toward a range-finding light-receiving element 30. The deflecting means 18 is constituted as a MEMS, which includes a mirror 181 that two-dimensionally swings and a mask MQ that has a low reflectance and shields a region including an edge of the mirror 181 and outside an effective reflection region of the mirror against the backward laser light BKL.

Description

  The present invention relates to a laser radar device.

  Various types of laser radar devices (hereinafter also referred to as laser ranging devices) have been proposed and are known (Patent Document 1, etc.).

  The laser distance measuring device scans the laser light beam two-dimensionally and irradiates the object to be measured, and receives and detects the laser beam reflected by the distance measuring object by the light receiving element for distance measurement.

Then, the distance to the distance measuring object is measured based on “the time required for the laser light to travel back and forth the distance to the distance measuring object”.
Since the object to be measured is scanned two-dimensionally by the laser beam, the shape of the object to be measured can also be known by measuring the distance.

  The laser beam irradiated to the distance measurement object is referred to as “irradiation laser light”, and the laser light reflected and received by the distance measurement object is referred to as “return laser beam”.

  In addition, the portion of the laser beam emitted from the laser light source that is two-dimensionally deflected to be “irradiation laser beam that scans the object to be measured” is called the “irradiation optical system”, and the return laser beam is distance-measured. A portion that guides light to the light receiving element is referred to as a “light receiving optical system”.

  As described above, the “ranging light receiving element” is a light receiving element that receives the return laser beam.

  Laser ranging devices are roughly classified into two types, “different axis system” and “coaxial system”.

  In the “different axis system”, the laser light source and the irradiation optical system are configured separately from the light receiving optical system and the distance measuring light receiving element.

  The “coaxial system” is a part of the optical system composing the irradiation optical system and part of the optical system composing the light receiving optical system. Is feasible.

  That is, in the coaxial system, both the “laser light source and irradiation optical system” and the “ranging light receiving element and light receiving optical system” are provided in the laser distance measuring apparatus.

  This invention makes it a subject to implement | achieve the novel laser radar apparatus of a coaxial system.

  The laser radar device according to the present invention includes a laser light source, an irradiation optical system for irradiating laser light for scanning a distance measuring object by two-dimensionally deflecting laser light from the laser light source, and the distance measurement A ranging light-receiving element that receives the return laser beam reflected by the object, a light-receiving optical system that guides the return laser beam to the ranging light-receiving element, and the measurement after the laser light is emitted. And a control calculation means for obtaining a distance to the distance measuring object according to a time until the distance light receiving element receives the return laser beam, and the irradiation optical system includes a laser beam from the laser light source. Is deflected two-dimensionally by a deflecting means, and the two-dimensionally deflected laser beam is emitted as a parallel beam-shaped irradiation laser beam through the objective lens, and the light receiving optical system includes at least The objective lens and The deflecting unit is used in common with the irradiation optical system, and becomes a divergent light beam by the objective lens, and collects the return laser beam deflected by the deflecting unit toward the light receiving element for distance measurement. An optical lens system, and the deflecting unit is configured as a MEMS, and has a mirror part that swings two-dimensionally, and a part of the mirror part including an edge part and outside the effective reflection region is disposed on the return laser. A low-reflectance mask that shields light from light is included.

  As described above, in the laser radar device of the present invention, the return laser beam becomes a divergent beam when passing through the objective lens, and enters the mirror portion of the deflecting means.

  The deflecting unit is configured as a MEMS, and deflects the laser light from the laser light source two-dimensionally by reflection by two-dimensional swinging of the mirror unit.

  The size of the mirror part for deflecting the laser beam is such that the deflected laser beam can be reflected, but the “effective reflection region” has a small area because the beam diameter of the deflected laser beam is small.

  Since one return laser beam is “divergent”, the size of the beam when entering the deflecting unit does not fit in the effective reflection region, and protrudes from the region.

  The “part protruding from the effective reflection region” of the return laser beam is incident on the portion surrounding the effective reflection region and is irregularly reflected.

  In particular, the reflected light irregularly reflected by the “edge part (outer shape part forming the mirror surface)” of the mirror part has an indefinite reflection direction and changes with the swing of the mirror part.

  When such irregularly reflected light is incident on the distance measuring light receiving element, it becomes a “noise component”, which causes a deterioration in distance measurement accuracy.

  Since the laser radar apparatus of the present invention has a low reflectance mask that shields the “part including the edge part and outside the effective reflection area” of the mirror part of the deflecting means against the return laser beam, the irregular reflection as described above. Can be effectively reduced or prevented, and distance measurement can be carried out in a stable system.

It is a figure for demonstrating one Embodiment of a laser radar apparatus.

Embodiments of the invention will be described below.
FIG. 1 is a diagram for explaining one embodiment of a laser radar device.

  In FIG. 1A, reference numeral 10 indicates a “laser light source”, reference numeral 12 indicates a “coupling lens”, reference numeral 14 indicates an “adjusting lens system”, and reference numeral 16 indicates an “irradiation optical path bending mirror”.

  Reference numeral 18 denotes a “deflecting means”, reference numeral 20 denotes an “objective lens”, reference numeral 30 denotes a “photodetecting element for distance measurement”, reference numeral 32 denotes a “condensing lens”, and reference numeral 34 denotes a “light receiving lens system”.

  Reference numeral 36 denotes a “light-receiving optical path bending mirror”, and reference numeral 40 denotes a “control calculation unit as a control calculation unit”.

  The laser light source 10 is a semiconductor laser (LD) and emits high-power laser light.

  The laser light emitted from the laser light source 10 passes through the coupling lens 12 and the adjustment lens system 14 and is converted into a “convergent laser beam” by receiving these optical actions.

  That is, the coupling lens 12 and the adjustment lens system 14 constitute a “coupling optical system that converts the laser light emitted from the laser light source 10 into a convergent laser beam”.

  The laser beam given a tendency to converge by the coupling optical system enters the irradiation optical path bending mirror 16 and is reflected toward the deflecting means 18.

  The deflecting means 18 is a deflector configured as MEMS (Micro Electro Mechanical Systems), and “mirrors the mirror part two-dimensionally” to deflect the direction of reflected light two-dimensionally.

  That is, the two-dimensional swing of the mirror part is a swing with the direction orthogonal to the drawing as the swing axis and a swing with the direction parallel to the drawing as the swing axis, and these swings are superimposed.

  The laser beam deflected two-dimensionally by the deflecting means 18 moves in “in a plane parallel to the drawing” in FIG. 1 and also in “a direction orthogonal to the drawing”.

  Thus, the laser light from the laser light source 10 enters the objective lens 20 while being deflected two-dimensionally by the deflecting means 18.

  That is, in FIG. 1, the coupling lens 12, the adjustment lens system 14, the deflecting unit 18, and the objective lens 20 constitute an “irradiation optical system”.

  The laser light beam deflected two-dimensionally by the deflecting means 18 is incident on the objective lens 20 and becomes “parallel light beam-shaped” irradiation laser light SRL by the objective lens 20.

  The parallel laser beam irradiation laser beam SRL is irradiated to a distance measuring object (not shown).

  With the operation of the deflecting means 18, the irradiation laser beam SRL is deflected two-dimensionally.

  The irradiation laser light SRL that irradiates the distance measurement object is reflected by the distance measurement object to become a “return laser beam BKL”.

  The laser radar device is used, for example, for “on-vehicle use or surveillance camera”, but the distance to the object to be measured is large in a general use situation.

  Therefore, the return laser beam BKL reflected by the object to be measured and incident on the objective lens 20 is substantially in a parallel beam state and is opposite in the same direction as the irradiation laser beam SRL.

  When the return laser beam BKL is incident on the objective lens 20, the return laser beam BKL is given a divergence tendency by the action of the objective lens 20 and is reflected by the deflecting means 18.

  The return laser beam BKL reflected by the deflecting means 18 is incident on and reflected by the light receiving optical path bending mirror 36, and enters the light receiving lens system 34 while maintaining the divergence.

  The return laser beam BKL transmitted through the light receiving lens system 34 enters the condenser lens 32, is condensed toward the distance measuring light receiving element 30, and is received by the distance measuring light receiving element 30.

  The light receiving lens system 34 and the condensing lens 32 constitute a “condensing lens system”.

When receiving the return laser beam BKL, the distance measuring optical element 30 sends a light reception signal (amplified at an appropriate amplification factor) to the control calculation unit 40.
The control calculation unit 40 is constituted by a CPU and a microcomputer.

  The control calculation unit 40 causes the laser light source 10 to emit pulses, determines a time: 2T from the moment of light emission to the moment of receiving the received light signal, and calculates a distance: CT using the speed of light: C.

  Along with the deflection of the irradiation laser beam SRL, the acquisition of the time: 2T and the calculation of CT are repeated.

  In this way, the distance to the distance measurement object and the three-dimensional shape of the distance measurement object are obtained.

  As described above, the irradiation laser light SRL for two-dimensionally scanning the object to be measured has a “parallel light beam shape”, so that the light beam diameter does not change on the way to the object to be measured, and the light intensity does not change. .

  Therefore, regardless of the distance to the distance measurement object, the distance measurement object can always be scanned with the “irradiation laser beam having the same intensity”, and stable distance measurement can be performed.

  That is, the laser radar apparatus shown in FIG. 1A uses a laser light source 10 and irradiation laser light SRL that scans a distance measuring object by two-dimensionally deflecting laser light from the laser light source. It has an “irradiation optical system”.

  Further, the light-receiving element 30 for distance measurement that receives the return laser beam BKL reflected by the object to be measured and the optical system for light reception that guides the return laser beam BKL to the light-receiving element 30 for distance measurement are provided.

  Then, it has a control calculation means 40 for obtaining the distance: CT to the distance measuring object by the time: 2T from when the laser light is emitted until the distance measuring light receiving element 30 returns and receives the laser beam BKL. .

  The “irradiation optical system” includes coupling optical systems 12 and 14 that convert laser light emitted from the laser light source 10 into a convergent laser beam, and deflecting means 18 that deflects the convergent laser beam two-dimensionally. And an objective lens 20 that converts the two-dimensionally deflected “convergent laser beam” into a parallel beam-shaped irradiation laser beam SRL.

  The “light receiving optical system” shares the objective lens 20 and the deflecting means 18 with the irradiation optical system.

  Then, there are condensing lens systems 34 and 32 for condensing the return laser beam BKL, which becomes a divergent light beam by the objective lens 20 and is deflected by the deflecting means 18, toward the light receiving element 30 for distance measurement.

  In the embodiment shown in FIG. 1A, the irradiation optical system is an irradiation optical path bending mirror that bends the optical path of the convergent laser beam by the coupling optical systems 12 and 14 toward the deflecting means 18. 16

  The light receiving optical system also includes a light receiving optical path bending mirror 36 that bends the optical path of the divergent return laser beam BKL via the deflecting means 18 toward the condenser lens systems 34 and 32.

  A few additional notes regarding the light receiving path bending mirror 36 will be given.

  As described above, the return laser beam BKL is incident on the objective lens 20 in a parallel beam state in the same direction as the irradiation laser beam SRL and in the opposite direction.

  Then, a divergent laser beam is produced by the action of the objective lens 20 and is reflected by the deflecting means 18.

  For this reason, the optical path of the return laser beam BKL reflected by the deflecting unit 18 is parallel to the optical path of the laser beam directed from the irradiation optical path bending mirror 16 to the deflecting unit 18.

  On the other hand, in the embodiment shown in FIG. 1A, the optical axis of the coupling optical system and the optical axis of the condenser lens system are laid out parallel to each other.

  Therefore, in this case, the mirror surface of the light receiving optical path bending mirror 36 is parallel to the mirror surface of the irradiation optical path bending mirror 16.

  In the embodiment shown in FIG. 1A, the “coupling optical system” is for adjusting the coupling lens 12 disposed on the laser light source 10 side, and for adjusting the laser light transmitted through the coupling lens 12 to converge. And a lens system 14.

  Hereinafter, the laser distance measuring device whose embodiment is shown in FIG.

  In the present invention, laser light emitted from the laser light source 10 is converted into a convergent laser beam by the coupling optical systems 12 and 14, and the convergent laser beam is deflected two-dimensionally by the deflecting means 18.

  Then, the convergent laser beam deflected two-dimensionally is converted into a parallel beam-shaped irradiation laser beam SRL by the objective lens 20.

  As described above, the combination of the action of “converting the laser light emitted from the laser light source 10 into a convergent laser light flux” of the coupling optical system and the action of the objective lens 20 makes the irradiation laser light SRL in the form of a parallel light flux. Is realized.

  Such a “combination of a coupling optical system and an objective lens” can be variously combined.

  In the embodiment shown in FIG. 1A, the coupling lens 12 has a collimating action, and makes the laser beam from the laser light source 10 a parallel beam.

  The adjustment lens system 14 is a “cylindrical lens”, has a positive refractive power in a plane parallel to the drawing, and emits a laser beam in a parallel luminous flux state incident from the coupling lens 12 side in a plane parallel to the drawing. Convert to a convergent laser beam.

  On the other hand, the objective lens 20 is a “concave cylindrical lens” having “negative refractive power” only in a plane parallel to the drawing and having no refractive power in a direction perpendicular to the drawing.

  The laser beam incident on the objective lens 20 is a parallel beam in a direction orthogonal to the drawing, and a convergent beam in a plane parallel to the drawing.

  Such an incident laser beam is converted into a parallel beam by correcting the convergence in a plane parallel to the drawing by the negative refractive power of the objective lens 20, and the refractive power of the objective lens in the direction orthogonal to the drawing. Does not work.

  Therefore, the irradiation laser beam SRL emitted from the objective lens 20 has a “parallel beam shape”.

  For this reason, the imaginary focal point due to the “negative refractive power” of the objective lens 20 is located on the “range object side” of the objective lens 20.

  The adjustment lens system 14 is displaced and adjusted in the optical axis direction so that the position of the imaginary focus is “substantially matched with the image-side focal position” of the adjustment lens 14.

  The combination of the coupling optical system and the objective lens is not limited to this.

  For example, the objective lens 20 is a “lens having a negative refractive power that is rotationally symmetric with respect to the optical axis”, and the adjustment lens system 14 is a “positive lens that is rotationally symmetric with respect to the optical axis”.

  Then, the mutual positional relationship is adjusted by “displacement of the positive lens in the optical axis direction” so that the focal position of the positive lens substantially matches the focal position of the objective lens 20.

  Even in this case, the irradiation laser beam SRL in the form of a parallel light beam can be obtained.

  In this case, the adjustment lens system 14 is omitted, and a converging laser beam is obtained by the coupling lens 12 alone, which is incident on the objective lens 20 and converted into a parallel beam by the negative refractive power of the objective lens 20. Laser light SRL can also be realized.

  That is, the coupling optical system and the objective lens can be designed in an appropriate combination so as to realize the parallel laser beam irradiation laser beam SFL.

  In the embodiment of FIG. 1A, among the condenser lens 32 and the light receiving lens system 34 constituting the condenser lens system, the light receiving lens system 34 has a function similar to that of the adjustment lens system 14. Convex cylindrical lens ".

  That is, the light receiving lens system 34 returns the return laser light beam BKL to a parallel light beam and makes it incident on the condenser lens 32.

  The distance measuring light receiving element 30 has its light receiving portion positioned at the focal position of the condensing lens 32, and receives the return laser beam BKL condensed by the condensing lens 32.

  Also in this case, the light receiving lens system 34 may be omitted, and the return light beam BKL may be directly condensed on the distance measuring light receiving element 30 by the condenser lens 32.

  As described above, when the adjustment lens system 14 is “a rotationally symmetric positive lens with respect to the optical axis”, the light receiving lens system 34 may be a positive lens having the same function as this positive lens.

  Note that the return laser beam BKL has a larger beam diameter than the laser beam passing through the adjustment lens system 14 at the stage of entering the condenser lens system, and accordingly, the lens diameter of the lens constituting the condenser lens system. Need to be larger.

  For this reason, the lens diameters of the light receiving lens system 34 and the condenser lens 32 are increased.

  As described above, the adjustment lens system 14 and the light receiving lens system 34 can be omitted.

  However, the use of these “lenses having a collimating function” increases the degree of freedom of adjustment of the optical system, so the use of these lenses 14 and 34 is preferable.

  Here, a specific example of the deflecting means 18 will be described.

  As described above, the deflecting unit 18 deflects the direction of the reflected light two-dimensionally by “swinging the reflecting surface two-dimensionally” with a deflector configured as a MEMS.

  FIG. 1B illustrates the main part of the deflecting means 18 in an explanatory manner.

  The deflecting unit 18 includes a mirror portion 181, a first frame body 182, and a second frame body 184. These are formed as “single structures”.

  The mirror unit 181 is a plane mirror, and its mirror surface is the “reflection surface”.

  The mirror unit 181 that forms a reflection surface is configured to receive and reflect the entire laser beam LF incident from the irradiation optical path bending mirror 16 side.

  That is, as shown in FIG. 1B, the reflection surface of the mirror unit 181 is larger than the beam diameter of the laser beam LF incident from the irradiation optical path bending mirror 16 side.

  Both the first frame body 182 and the second frame body 184 are rectangular frames, and the mirror portion 181 is fixed to the first frame body 182 by axes j1 and j2 sharing a swing axis.

  The axes j1 and j2 have “torsional elasticity”, and the reflecting mirror 181 can be swung around a swinging axis shared by the axes j1 and j2 by a restoring force of torsional deformation.

The first frame 182 is fixed to the second frame 184 by axes j3 and j4.
The axes J3 and j4 also share the swing axis.

  The shafts j3 and j4 also have torsional elasticity, and the first frame 182 can be swung around the swinging shaft shared by the shafts j3 and j4 by the restoring force of torsional deformation.

  The axes j1, j2, j3, and j4 also form part of a single structure together with the first frame 182 and the second frame 184.

As shown in FIG. 1D, the second frame 184 is fixedly disposed in the casing MQS.
The driving means (not shown) is configured as an electronic circuit element by MEMS, and is manufactured together with the structure shown in FIG.
The swing axis shared by the axes j1 and j2 and the swing axis shared by the axes j3 and j4 are orthogonal to each other.
Therefore, the mirror unit 181 can be “oscillated independently in two vertical and horizontal directions orthogonal to each other”.

  The driving means fixed to the mirror unit 181 can be connected to the reflecting mirror 181 to drive the reflecting mirror 181 to swing.

  Similarly, driving means fixed to the second frame 184 can be connected to the first frame 182 to drive the first frame 182 having the mirror portion 181 to swing.

  Needless to say, the operation of the “driving means” is controlled by the control calculation unit 40.

  The mask MQ will be described with reference to FIG.

  The mask MQ shields the “part including the edge part and outside the effective reflection region” of the mirror part 181 from the return laser beam, and has “low reflectance”.

  As shown in FIG. 1C, when the mirror portion 181 is viewed through the mask MQ, the mirror portion 181 can be seen only at the opening portion opened in the mask MQ.

  The opening portion opened in the mask MQ is a size that shields the “return laser beam” from “the portion including the edge portion of the mirror portion 181 (shown by a broken line) and outside the effective reflection region”.

  As shown in FIG. 1D, the mask MQ is disposed so as to be sandwiched between a casing MQS that houses the mirror portion 181 and a mounting member DR that attaches the casing MSQ to the main body side of the laser radar device.

  In this way, by providing the low-reflectance mask MQ that shields the part of the mirror part 181 including the edge part and the outside of the effective reflection region from the return laser beam BKL, the above-described irregular reflection of the return beam is prevented. It can be effectively reduced or prevented.

  Instead of using a mask in this way, it is conceivable to apply an “antireflection treatment” to the portion “outside the effective reflection region” of the mirror section 18, but using a mask is less expensive.

  The mask MQ can be formed of any appropriate material as long as it has a “low refractive index”, but “raised paper” is suitable as a mask material.

  Various types of brushed paper are commercially available at low prices, and those having low reflectivity with respect to the laser beam can be appropriately selected according to the wavelength of the laser beam used for distance measurement.

  In addition, the mask can be easily replaced if necessary.

  As described above, according to the present invention, the following laser radar device can be realized.

[1]
Laser light source 10, irradiation optical system for irradiating laser light SRL for scanning a distance measurement object by two-dimensionally deflecting laser light from the laser light source, and return reflected by the distance measurement object A ranging light-receiving element 30 that receives the laser beam BKL, a light-receiving optical system that guides the return laser beam to the ranging light-receiving element, and the ranging light-receiving element that returns after the laser light is emitted. Control calculation means 40 for obtaining the distance to the object to be measured depending on the time until the light is received. The irradiation optical system deflects the laser light from the laser light source 10 two-dimensionally by the deflection means 18. The two-dimensionally deflected laser beam is emitted as a parallel beam-shaped irradiation laser beam SRL through the objective lens 20, and the light receiving optical system includes at least the objective lens 20, the deflecting unit 18, and the like. Irradiate Condensing lens systems 32 and 34 for converging the return laser beam BKL, which is shared by the optical system and becomes a divergent light beam by the objective lens, and deflected by the deflecting means toward the light receiving element 30 for distance measurement, The deflecting unit 18 is configured as a MEMS and includes a mirror unit 181 that swings two-dimensionally. The deflecting unit 18 is a low-light shielding unit that shields a portion of the mirror unit including the edge portion and outside the effective reflection region from the return laser beam. A laser radar device having a reflectance mask MQ.

[2]
Coupling optical systems 12 and 14 for converting the laser light emitted from the laser light source into a converging laser beam, and deflecting means 18 for deflecting the converging laser beam two-dimensionally. A laser radar device having an objective lens 20 that converts a two-dimensionally deflected convergent laser beam into a parallel beam-shaped irradiation laser beam SRL.

[3]
The laser radar device according to [1] or [2], wherein the mask MQ is formed of brushed paper.

The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments described above, and the invention described in the claims unless otherwise specified in the above description. Various modifications and changes are possible within the scope of the above.
The effects described in the embodiments of the present invention are merely a list of suitable effects resulting from the invention, and the effects of the present invention are not limited to those described in the embodiments.

10 Laser light source
12 Coupling lens
14 Lens system for adjustment
16 Optical path folding mirror for irradiation
18 Deflection means
20 Objective lens
Laser light for SRL irradiation
BKL return laser beam
30 Light receiving element for distance measurement
32 condenser lens
34 Cylindrical lens
MQ mask

JP2013-113684A

Claims (3)

A laser light source;
An irradiating optical system that irradiates laser light from the laser light source in a two-dimensional manner and scans the object to be measured;
A light-receiving element for distance measurement that receives the return laser beam reflected by the object to be measured;
A light receiving optical system for guiding the return laser beam to the distance measuring light receiving element;
Control calculation means for obtaining a distance to the distance measuring object according to a time from when the laser light is emitted until the distance measuring light receiving element receives the return laser beam,
The irradiation optical system deflects the laser light from the laser light source in a two-dimensional manner by a deflecting unit, and the two-dimensionally deflected laser light is emitted as an irradiation laser light in the form of a parallel beam through an objective lens. Configured to
The light receiving optical system shares at least the objective lens and the deflecting means with the irradiation optical system, becomes a divergent light beam by the objective lens, and converts the return laser light beam deflected by the deflecting means to the It has a condensing lens system that condenses toward the light receiving element for distance measurement,
The deflecting unit is configured as a MEMS, has a mirror part that swings two-dimensionally, and shields the part of the mirror part including the edge part and outside the effective reflection region from the return laser beam. A laser radar apparatus having a reflectance mask. A coupling optical system for converting the laser light emitted from the laser light source into a convergent laser beam; and a deflecting unit for deflecting the convergent laser beam in a two-dimensional manner.
A laser radar apparatus comprising: an objective lens that uses a two-dimensionally deflected convergent laser beam as a parallel beam-shaped irradiation laser beam.   3. The laser radar device according to claim 1, wherein the mask is made of brushed paper.

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