US009316495B2
`
`US 9,316,495 B2
`(10) Patent No.:
`az) United States Patent
`Suzuki etal.
`(45) Date of Patent:
`Apr. 19, 2016
`
`
`(54) DISTANCE MEASUREMENTAPPARATUS
`
`(56)
`
`References Cited
`
`(71) Applicants:Shuichi Suzuki, Kanagawa (JP);
`Kenichi Yoshimura, Kanagawa (JP):
`Mitsuru Nakajima, Kanagawa (JP);
`Yusuke Hayashi, Kanagawa (JP)
`
`(72)
`
`Inventors: Shuichi Suzuki, Kanagawa(JP);
`Kenichi Yoshimura, Kanagawa(JP);
`Mitsuru Nakajima, Kanagawa (JP);
`Yusuke Hayashi, Kanagawa (JP)
`(73) Assignee: Ricoh Company, Ltd., Tokyo (JP)
`
`(*) Notice:
`
`Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`US.C. 154(b) by 308 days.
`
`(21) Appl. No.: 13/962,196
`
`(22)
`
`(65)
`
`(30)
`
`.
`Filed:
`
`Aug. 8, 2013
`
`‘
`+
`att
`Prior Publication Data
`US 2014/0071428 Al
`Mar. 13, 2014
`
`Foreign Application Priority Data
`
`Sep. 13,2012
`
`IP) wee escteeeeeeeeees 2012-201054
`
`U.S. PATENT DOCUMENTS
`5,314,037 A
`5/1994. Shaw et al.
`6,163,371 A * 12/2000 Kato etal. oo. 356/4.03
`
` 356/3.1
`6,587,183 BL *
`7/2003 Uomuriet al.
`9/2003 Benzetal. oo. 356/5.1
`2003/0169414 Al*
`2009/0048727 Al
`2/2009 Hongetal.
`2013/0077083 Al
`3/2013 Suzuki et al.
`2013/0120734 Al
`5/2013. Ogataetal.
`
`oN
`CN
`a
`1p
`
`FOREIGN PATENT DOCUMENTS
`loLtixelo ‘
`coo
`101813778 A
`8/2010
`6soos,,
`IHitoso
`7.146353
`6/1995
`
`(Continued)
`OTHER PUBLICATIONS
`
`Extended European Search Report issued Oct. 2, 2014 in Patent
`Application No. 13181194.
`USS. Appl. No. 13/771,465, filed Feb. 20, 2013.
`US'S. Appl. No. 13/930,030, filed Jun. 28, 2013.
`USS. Appl. No. 13/909,340,filed Jun. 4, 2013.
`(Continued)
`
`Primary Examiner — Luke Ratcliffe
`(74) Attorney, Agent, or Firm —Oblon, McClelland,
`Maier & Neustadt, L.LP.
`
`(51)
`
`ABSTRACT
`(57)
`Int. Cl.
`A distance measurement apparatus that measures distance to
`GOIC 3/08
`(2006.01)
`a target byirradiating the target with laser beamsand detect-
`GO1S 17/00
`(2006.01)
`ing light reflected by the target includesa light projection unit.
`GOIS 7/484
`(2006.01)
`The distance measurement apparatus also includes a plurality
`GOIS 7/486
`(2006.01)
`of light emission units to emit a plurality of laser beams onto
`2
`the target while setting optical
`pathsofthe plurality
`of laser
`($2) US. Cl.
`CPC . GOIC 3/08(2013.01); GOIS 7/484 (2013.01);
`tS dally
`al
`& OP
`aa I olane yi
`i ca
`GO1S 7/4863 (2013.01); GOLS 17/00 (2013.01)
`amsTialllyalong @ given vitna Plane, anda aga
`receny
`.
`:
`:
`ing unit including a plurality oflight receivers to receive the
`(58) Field of Classification Search
`plurality of laser beams projected from the light projection
`CPC ........ GO01S 17/02; GO1S 17/10; GOIS 7/4811
`unit and reflectedbythetarget.
`USPC iceccsesecsesseseeceeesersensseneneeeees 356/3.01-5.15
`See application file for complete search history.
`
`16 Claims, 16 Drawing Sheets
`
`OPTIGAL PATH OF
`OPTICAL PATH OF
`TOTAL PROJECTION
`PROJECTION LIGHT
`PROJECTION LIGHT
`ANGLE RANGE
`80 DEGREES
`
`
`f
`?
`
`PROJECTION
`PROJECTION
`40 DEGREES
`ANGLE RANI
`
`ANGLE RANGE
`
`
`40 DEGREES
`20 DEGREES
`
`
`
`1
`
`APPLE 1072
`Apple v. Masimo
`IPR2022-01291
`
`1
`
`APPLE 1072
`Apple v. Masimo
`IPR2022-01291
`
`

`

`US 9,316,495 B2
`Page 2
`
`(56)
`
`References Cited
`
`FOREIGN PATENT DOCUMENTS
`
`OTHER PUBLICATIONS
`U.S. Appl. No. 13/920,401, filed Jun. 18, 2013.
`Combined Chinese Office Action and Search Report issued Jul. 10,
`2015 in Patent Application No. 201310309562.X (with English
`translation of categories of cited documents).
`
`JP
`12/1995
`7-324911
`JP
`7/2009
`2009-145107
`WO
`WO 02/082016 Al—10/2002
`* cited by examiner
`
`2
`
`

`

`U.S. Patent
`
`Apr. 19, 2016
`
`Sheet 1 of 16
`
`US 9,316,495 B2
`
`OPTICAL PATH OF
`OPTICAL PATH OF
`TOTAL PROJECTION
`PROJECTION LIGHT
`ANGLE RANGE
`PROJECTION LIGHT
`
`
`
`
`80 DEGREES
`
`
`\
`
`
`
`
`
`PROJECTION
`ANGLE RANGE
`
`
`
`
`PROJECTION
`ANGLE RANGE
`40 DEGREES
`
`40 DEGREES 20 DEGREES
`
`3
`
`

`

`U.S. Patent
`
`Apr. 19, 2016
`
`Sheet 2 of 16
`
`US 9,316,495 B2
`
`NOLLVYSNSD|2—_sgNeFaee
`
`L02HOnGOTWNOIS
`TIndUloLHSHO
`WNOIS YOLVuVd
`
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`
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`
`DNILNdWOO
`
`LINDYID
`
`LHON
`
`NOISSIWA
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`JOYULNOO
`
`LINOUYIO
`
`LHOM
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`LINN
`
`JONVILSIO
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`ONILNdWOOD
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`LINOUYIO
`
`TOYULNOOD
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`-WO9
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`4
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`

`

`U.S. Patent
`
`Apr. 19, 2016
`
`Sheet 3 of 16
`
`US 9,316,495 B2
`
`100
`
`30
`
`af
`12
`13
`
`wD)L-
`
`Vy,
`
`Cl
` REFLECTION
`
`LIGHT
`
`LIGHT
`
`5
`
`

`

`U.S. Patent
`
`Apr. 19, 2016
`
`Sheet 4 of 16
`
`US 9,316,495 B2
`
`FIG. 4
`
`100
`
`
`
`30
`
`12
`
`13
`
`PROJECTION
`LIGHT
`—>
`
`
`
`FIG. 9
`
`100
`vane
`REFLECTION LIGHT _
`REFLECTION
`(OBLIQUE ENTERING)»,
`LIGHT
`I
`(INCIDENT
`
`
`
`LIGHT RECEIVING=39 Letom
` ANGLE: 0 DEGREE)
`AREA
`
`
`
`RECEIVING
`ANGLE
`RANGE
`40 DEGREE
`
` LIGHT
`
`y¥
`
`[
`
`REFLECTION LIGHT
`(OBLIQUE ENTERING)
`
`!
`
`6
`
`

`

`U.S. Patent
`
`Apr. 19, 2016
`
`Sheet 5 of 16
`
`US 9,316,495 B2
`
`OPTICAL PATH OF
`PROJECTION LIGHT
`
`BROJECTION
`ANGLE RANGE
`
`OPTICAL PATH OF
`PROJECTION LIGHT
`
`80 DEGREES
`
`
`
`PROJECTION
`PROJECTION
`ANGLE RANGE
`ANGLE RANGE
`
`
`40 DEGREES
`40 DEGREES
`
`
`
`
`
`7
`
`

`

`U.S. Patent
`
`Apr. 19, 2016
`
`Sheet 6 of 16
`
`US 9,316,495 B2
`
`TOTAL PROJECTION
`ANGLE RANGE
`80 DEGREES
`
`OPTICAL
`PATH OF
`
`LIGHT
`
`OPTICAL PATH OF
`PROJECTION LIGHT
`
`OPTICAL PATH OF
`PROJECTION LIGHT
`
`OPTICAL
`PATH OF
`
`LIGHT
`
`PROJECTION PROJECTION
`
`PROJECTION
`PROJECTION
`
`PROJECTION ANGLE RANGE/PROJECTIONANGLE RANGE
`
`
`ANGLE RANGE\90 DEGREES 9°90 DEGREES ANGLE RANGE
`
`20 DEGREES
`20 DEGREES
`
`100
`
`100
`
`8
`
`

`

`U.S. Patent
`
`Apr. 19, 2016
`
`Sheet 7 of 16
`
`US 9,316,495 B2
`
`= 2_©u
`
`u
`i)
`oO
`u
`
`oo
`
`FIG.8
`
`LIGHT
`
`REFLECTION
`
`LIGHT
`
`9
`
`

`

`U.S. Patent
`
`Apr. 19, 2016
`
`Sheet 8 of 16
`
`US 9,316,495 B2
`
` REFLECTION
`
`10
`
`10
`
`

`

`U.S. Patent
`
`Apr. 19, 2016
`
`Sheet 9 of 16
`
`US 9,316,495 B2
`
`REFLECTION
`
`
` CYLINDRICALFACE
`
`
`FIRST
`
` PROJECTIONLIGHT
`
`FIG.10
`
`11
`
`11
`
`

`

`U.S. Patent
`
`Apr.19, 2016
`
`Sheet 10 of 16
`
`US 9,316,495 B2
`
`
` REFLECTION
`
`
`
`LIGHT
`<q
`
`12
`
`

`

`U.S. Patent
`
`Apr.19, 2016
`
`Sheet 11 of 16
`
`US 9,316,495 B2
`
`LIGHT
`
`REFLECTION
`
`Zz
`oOkK
`OLu
`~~
`Oo
`
`&a
`
`LIGHT
`
`FIG.12
`
`13
`
`13
`
`

`

`U.S. Patent
`
`Apr.19, 2016
`
`Sheet 12 of 16
`
`US 9,316,495 B2
`
`
`
`14
`
`

`

`U.S. Patent
`
`Apr.19, 2016
`
`Sheet 13 of 16
`
`US 9,316,495 B2
`
`FIG. 14
`
`BLAZED
`
`
`GRATING
`
`RhoOwaNoiasdCcwo
`
`10
`
`
`
`GRATINGPITCHd[um]
`
`0
`
`9
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`DIFFRACTION ANGLE £ [°
`
`]
`
`15
`
`15
`
`

`

`U.S. Patent
`
`Apr. 19, 2016
`
`Sheet 14 of 16
`
`US 9,316,495 B2
`
`FIG. 16
`
`18
`
`1.7
`
`1.6
`
`1.95
`
`1.4
`
`1.3
`
`1.2
`
`1.0
`
`0.9
`
`
`
`GRATINGHEIGHTh[um]
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`30
`
`55
`
`60
`
`DIFFRACTION ANGLE B[° ]
`
`16
`
`16
`
`

`

`U.S. Patent
`
`Apr. 19, 2016
`
`Sheet 15 of 16
`
`US 9,316,495 B2
`
`NOISSIWS AWIL
`
`
`
`|?————————uc—“—“——_AWAUSLND
`
`--4-----------I-gVadNOISSINS
`
`17
`
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`
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`AWIL
`
`
`
`-¥-—~-----------VWVddNOISSINS
`
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`
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`
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`
`NOISSIW3
`
`ALISNSLNI
`
`NOISSIWA
`
`17
`
`
`
`

`

`U.S. Patent
`
`Apr.19, 2016
`
`Sheet 16 of 16
`
`US 9,316,495 B2
`
`30
`
`a
`12
`
`13
`
`
`PROJECTION
`LIGHT
`
`REFLECTION
`
`18
`
`

`

`US 9,316,495 B2
`
`1
`DISTANCE MEASUREMENT APPARATUS
`
`CROSS-REFERENCE TO RELATED
`APPLICATION
`
`This application claimspriority pursuant to 35 U.S.C. §119
`to Japanese Patent Application No. 2012-201054, filed on
`Sep. 13, 2012 in the Japan Patent Office, the disclosure of
`whichis incorporated by reference herein in its entirety.
`
`10
`
`BACKGROUND
`
`1. Technical Field
`
`The present invention generally relates to a distance mea-
`surement apparatus, and moreparticularly to a distance mea-
`surementapparatusthat irradiates a target with light, receives
`reflection light to measure a distanceto the target.
`2. Background Art
`In conventional laser radar apparatuses such as that dis-
`closed in JP-2009-145107-A,light emitted from a laser diode
`is radiated to a given area ofantarget via an oscillation mirror,
`which can oscillate about a first axis and a second axis per-
`pendicularto the first axis, and a mirror unit having a plurality
`of mirrors having different inclination angles with respect to
`a third axis perpendicularto thefirst axis. Light reflected from
`the given area is received by a photodiodevia the mirrorunit
`to measure distanceto a plurality ofportions in the given area
`within a short time period.
`However, the laser radar apparatus of JP-2009-145107-A
`has a complex configuration and control protocol, and is
`therefore costly.
`
`SUMMARY
`
`2
`FIG. 8 shows a schematic configuration of a light receiving
`unit of one type of a third variant example;
`FIG. 9 shows a schematic configuration of a light receiving
`unit of another type of a third variant example;
`FIG. 10 showsa schematic configuration of a light receiv-
`ing unit of one type of a fourth variant example;
`FIG. 11 showsa schematic configuration of a light receiv-
`ing unit of another type of a fourth variant example;
`FIG. 12 showsa schematic configuration of a light receiv-
`ing unit of one type of a fifth variant example;
`FIG. 13 shows a schematic configuration of a light receiv-
`ing unit of another type of a fifth variant example;
`FIG. 14 shows a schematic configuration of a blazed grat-
`ing;
`FIG. 15 shows an example profile indicating a relationship
`between diffraction angle of a blazed grating and grating
`pitch;
`FIG. 16 shows an example profile indicating a relationship
`between diffraction angle of a blazed grating and grating
`height;
`FIG. 17 shows an example of timing chart andlight inten-
`sity of LD of a sixth variant example; and
`FIG. 18 showsa schematic configuration of a laser system
`of a seventh variant example.
`The accompanying drawingsare intended to depict exem-
`plary embodimentsofthe present invention and should not be
`interpreted to limit the scope thereof. The accompanying
`drawings are not to be considered as drawn to scale unless
`explicitly noted, and identical or similar reference numerals
`designate identicalor similar components throughoutthe sev-
`eral views.
`
`DETAILED DESCRIPTION
`
`In one aspect of the present invention, a novel distance
`measurement apparatus to measure distance to a target by
`A description is now given of exemplary embodiments of
`irradiating the target with laser beams and detecting light
`the present invention. It should be noted that although such
`reflected by the target is devised. The distance measurement
`termsas first, second, etc. may be used herein to describe
`apparatus includesa light projection unit includingaplurality
`40
`various elements, components, regions, layers and/or sec-
`of light emission units to emit a plurality of laser beamsto the
`tions, it should be understood that such elements, compo-
`target while setting optical paths of the plurality of laser
`nents, regions, layers and/or sections are not limited thereby
`beamsradially along a given virtual plane; and a light receiv-
`because such termsare relative, that is, used only to distin-
`ing unit including a plurality oflight receivers to receive the
`guish one element, component, region, layer or section from
`plurality of laser beams projected from the light projection
`another region, layer or section. Thus, for example, a first
`unit and reflected by the target.
`element, component, region,layer or section discussed below
`could be termed a second element, component, region, layer
`or section without departing from the teachings of the present
`invention.
`
`In addition, it should be noted that the terminology used
`herein is for the purpose of describing particular embodi-
`ments only andis not intended to be limiting of the present
`invention. Thus, for example, as used herein, the singular
`forms “a’’, “an” and “the” are intended to includethe plural
`formsas well, unless the context clearly indicates otherwise.
`Moreover, the terms “includes” and/or “including”, when
`used in this specification, specify the presence of stated fea-
`tures, integers, steps, operations, elements, and/or compo-
`nents, but do not preclude the presence or addition of one or
`more other features, integers, steps, operations, elements,
`components, and/or groups thereof.
`Furthermore, although in describing views shown in the
`drawings, specific terminology is employed for the sake of
`clarity, the present disclosure is not limited to the specific
`terminology so selected andit is to be understood that each
`specific element includesall technical equivalents that, have
`a similar function, operate in a similar manner, and achieve a
`
`65
`
`19
`
`45
`
`50
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`A more complete appreciation of the disclosure and many
`of the attendant advantages and features thereof can be
`readily obtained and understood from the following detailed
`description with reference to the accompanying drawings,
`wherein:
`FIG. 1 showsa schematic configuration of a distance mea-
`surement apparatus according to an example embodiment;
`FIG. 2 is a block diagram of the distance measurement
`apparatus;
`FIG. 3 shows a schematic configuration ofa laser system of
`the distance measurement apparatus;
`FIG. 4 shows a schematic configuration ofthe light emis-
`sion unit of the laser system;
`FIG. 5 shows a schematic configuration ofthe light receiv-
`ing unit of the laser system;
`FIG. 6 showsa schematic configuration of a distance mea-
`surement apparatusof a first variant example;
`FIG. 7 showsa schematic configuration of a distance mea-
`surement apparatus of a second variant example;
`
`19
`
`

`

`3
`similar result. Referring now to the drawings, apparatuses or
`systems according to example embodiment are described
`hereinafter.
`
`US 9,316,495 B2
`
`4
`11 at +X side and the LD 11 at —X side are not considered as
`separate parts, the exit direction of LD 11 is referred to as the
`a-axis direction, and a direction perpendicular to the a-axis
`direction in the XY planeis referred to as the gamma(y)-axis
`direction.
`
`Adescription is now given to an example embodiment with
`reference to FIGS. 1 to 5. FIG. 1 shows a schematic configu-
`Further, for example, laser beam emitted from each LD 11
`ration of a distance measurement apparatus 1000 of accord-
`has a given divergence angle along the ay plane (XY plane) as
`ing to an example embodiment.
`shownin FIG.4, and a given divergence angle along the aZ
`The distance measurement apparatus 1000 is installed, for
`plane as shownin FIG.3. In FIGS. 3 to 5, yaZ three-dimen-
`example, in vehicles. The distance measurement apparatus
`sional orthogonal coordinate system is used.
`1000 irradiates targets such as other vehicles (hereinafter,
`The LD 11 is, for example, an edge emitting semiconductor
`other vehicle) with light and receives the reflection light
`laser having a base plate, and stacked-layers, wherein the
`reflected from the targets to measure a distanceto thetargets
`such as other vehicles.
`stacked-layers are composedof stacking a plurality of semi-
`conductor layers having an activation layer formed on the
`Further, the distance measurement apparatus can be dis-
`base plate. In the LD 11, the base plateis positioned in parallel
`posed forstill targets or moving targets other than vehicles,
`to the XY plane, and as for a light emission area of the
`and further, the distance measurementapparatus can be used
`activation layer, a long side direction of rectangular cross-
`alone. Further, the target includes, for example,still targets
`section is parallel to the XY plane, and a short side direction
`and movingtargets in addition to vehicles.
`ofrectangular cross-section is perpendicularto the XY plane.
`As shown in FIG.1, the distance measurement apparatus
`For example, a width of the long side direction of rectan-
`1000 includes, for example, two laser systems 100a/1008, a
`gular cross-section of the light emission area is set from 100
`control circuit 200, and a casing 300 that encase these units.
`um to 300 um, and a width of the short side direction of
`The casing 300 is, for example, a box member.
`In this example case, XYZ three dimensional orthogonal
`rectangular cross-section of the light emission area is set 10
`
`coordinate system is set, in whichadirection perpendicular to um orless.
`a moving direction of a vehicle equipped with the distance
`Asfor the edge emitting semiconductor laser (LD), in a
`measurement
`apparatus
`1000
`(hereinafter,
`apparatus-
`direction parallel to the base plate, the width of light emission
`equipped vehicle) is set as the Z-axis direction.
`area is broad, and can be operated with multi-mode,and light
`The two laser systems 100a@ and 1005 have the same con-
`intensity profile in the light emission area becomes uniform.
`figuration substantially, and are disposed symmetrically with
`To be described later, because a laser beam profile in a
`respect to the YZ plane. Hereinafter, the two laser systems
`direction parallel to the XY plane (hereinafter, horizontal
`100a and 1006 maybereferred to as the laser system 100.
`direction) of a laser beam irradiated to other vehicle is
`As shown in FIG. 3, the laser system 100 includes, for
`required to be uniform to enhance distance detection preci-
`example, a light emission unit 10, a light receiver 20, and a
`sion,the base plate ofthe LD 11 is positionedinparallelto the
`holder 30 to hold the light emission unit 10 and the light
`XYplane as described above.
`receiver 20 integrally. The light emission unit 10 and the light
`As shownin FIG.3, the LD drive circuit 9 is disposed on
`receiver 20 are disposed with a given distance apart, for
`the circuit board 14, and supplies modulation current to the
`example, several millimeters (mm) to several centimeters
`LD 11 to drive the LD 11 based on emission signal from a
`(cm) in the Z-axis direction, which means disposed sepa-
`light emission control circuit 201,
`to be described later.
`rately. For example, the light emission unit 10 is disposed at
`Therefore, the LD 11 emits modulated light beam having a
`+Z side and the light receiver 20 is disposed at -Z side, but the
`time-line waveform corresponding to current signals for a
`position ofthe light emission units 10 and 20 can be changed.
`waveform supplied from the LD drive circuit 9.
`The holder 30 is, for example, a box memberofrectangular
`The modulated light beam having waveform generated by
`parallelepiped shape, which may have a longer side in one
`the LD drive circuit 9 is, for example, a pulse wave used for
`direction such as Z-axis direction. The holder 30 retains the
`normal distance measurement apparatus. For example, a
`light emission unit 10 and the light receiver 20 therein with
`drive signal is pulses having a pulse width of several nano
`the above described positional relationship.
`seconds to several tens nano seconds, a peak intensity of
`The light emission unit 10 includes, for example, a laser
`about several tens Watt, and frequencies of several kHz to
`diode (LD) 11 used as a light source, a LD drive circuit 9,
`several tens kHz in time line are supplied to the LD 11. The
`whichis a light source drive circuit, and a projection optical
`LD 11 emits laser beamson andoff based onthe drive signal.
`system 8 integrally.
`The LD drive circuit 9 is input with a light emissiontrigger
`A shownin FIG.1, for example, each LD 11 is disposed on
`signal and a given direct current voltage from the control
`circuit 200, to be described later, via a connector 250, and
`a circuit board 14 (see FIG. 3) while directing an light exit
`direction of each LD 11 to other vehicle positioned at +Y side
`generates modulation signals to be output to the LD 11.
`of the apparatus-equipped vehicle. Specifically, the LD 11 at
`The projection optical system 8 includes, for example, a
`-X side has, for example, an exit direction (a.1-axis direc-
`coupling lens 12 and a cylindrical lens 13 to shape laser
`beams emitted from the LD 11.
`tion), parallel to the XY plane, which is angled 20 degrees to
`-X side from +Y direction, and the LD 11 at +X side has, for
`example, an exit direction (@2-axis direction), parallel to the
`XY plane, which is angled 20 degrees to +X side from +Y
`direction,
`Therefore, the exit direction ofthe LD 11 at —X side and the
`exit direction of the LD 11 at +X side can define an angle of
`40 degrees in the XY plane. In this example, a direction
`perpendicular to the al-axis direction in the XY plane is
`referred to as a gamma 1(y1)-axis direction, and a direction
`perpendicular to the @2-axis direction in the XY plane is
`referred to as a gamma2 (y2)-axis direction. Further, ifthe LD
`
`The coupling lens 12 is disposed on optical paths of laser
`beams emitted from the LD 11 to set the laser beams as
`substantially parallel light.
`As shown in FIG.4,the cylindrical lens 13 is disposed on
`optical paths of laser beams after the coupling lens 12 to
`diffuse the laser beams in the y-axis direction (1.e., direction
`parallel to the XY plane). For example, the cylindrical lens 13
`has an incidenceface used asa refraction face having negative
`refractive powerin the y-axis direction. In this case, the cylin-
`drical lens 13 is, for example, curved so that the ay cross-
`section of the incidence face of the cylindrical
`lens 13
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`5
`becomes convex at +c side. Further, the optical axis of the
`cylindrical lens 13 is aligned to the optical axis of the cou-
`pling lens 12.
`In this case, the long side direction of rectangular cross-
`section light emission area ofthe LD 11 anda direction of the
`cylindrical lens 13 having the power are matched. With this
`configuration, a divergence angle oflaser beams emitted from
`the light emission unit 10 along the ay plane (XY plane) can
`be further enlarged, and the light intensity can be set uniform
`within the divergence angle range. Ifthe light intensity can be
`set uniform within the divergence angle range along the ay
`plane, distance measurementprecision for each divided area
`can be preferably set uniform when the distance detection
`angle range is divided in the horizontal direction.
`Laser beams emitted from the cylindrical lens 13, which
`meansthe laser beams emitted from the light emission unit 10
`can be projected outside the holder 30 through a window
`disposed on at a +a-side wall ofthe holder 30, and then can be
`projected outside the casing 300 via a light-permeable win-
`dow member 400, madeoftranslucent glass (or translucent
`plastic), attached on an opening formed on the +Y-side wall of
`the casing 300. Therefore, the laser beam projected from the
`light-permeable window member 400 is the laser beam pro-
`jected from the distance measurement apparatus 1000. Fur-
`ther, the light-permeable window member400 canbeset with
`a function of a band-passfilter to prevent entering of ambient
`light into the casing 300.
`The two light emission units 10 configures a light projec-
`tion unit that projects two laser beams having optical paths
`arranged radially along the XY plane.
`The two laser beams having optical paths along the XY
`plane meansthe optical paths ofthe two laser beamsalong the
`XYplaneare separated, close (including contacting), or over-
`lappedslightly.
`Further, for example, the exit direction of the two laser
`beamsare angled for 40 degrees in the XY plane each other,
`and each ofthe two laser beamshasthe divergence angle of40
`degrees along the XY plane. Further, for example, each of the
`twolaser beams has a divergence angle of 10 degrees along
`the aZ plane.
`With this configuration, the distance measurement appara-
`tus 1000 can project laser beams toward other vehicle posi-
`tioned at +Y side of the apparatus-equipped vehicle in an
`angle range of 80 degrees along the XY planeentirely, and a
`maximum angle range of 10 degrees along a plane perpen-
`dicular to the XY plane (Z-axis direction).
`The laser beam projected. to other vehicle from the each
`light emission unit 10 in the light projection unit (hereinafter,
`projection light) is reflected at other vehicle, and a part of the
`reflection light returns along the sameoptical path of projec-
`tion light, and enters the light receiver 20. Further, the +a-side
`wall of the holder 30 has a window to pass through the
`reflection light to the light receiver 20.
`As shown in FIG. 5, the light receiver 20 includes, for
`example, a photodiode (PD) 21 used as a light receiving
`element, a condensing lens 22 used as a light condensing
`system, and a signal amplification circuit 23 (see FIG. 3) as
`one integrated unit.
`The PD 21 has, for example, a light receiving face includ-
`ing a plurality of light receiving areas arranged along the
`y-axis direction. The PD 21 is equippedto a circuit board 24
`while setting the light receiving face perpendicular to the exit
`direction (a-axis direction) of the exit direction of LD 11.
`The condensinglens 22 is disposed on optical paths of laser
`beams projected from the light emission unit 10 of the laser
`system 100 and reflected at other vehicle to focus the laser
`beams to any oneofthe light receiving areas of the PD 21.
`
`6
`For example, the condensing lens 22 has a shapethat a size
`in the Z-axis direction is long anda size in the y-axis direction
`is short, which meansa shape having a greater aspectratio is
`used.
`
`Eachofthe twolight receivers 20 is used as a light receiv-
`ing unit to receive the laser beam emitted from the light
`projection unit and reflected at other vehicle.
`Further, the light emission unit 10 andthelight receiver 20
`in each of the laser systems 100 are disposed close to each
`other in the Z-axis direction as described above. For example,
`the optical axis of the projection optical system 8 and the
`optical axis of the condensing lens 22 can be assumed on the
`same axis when viewed from a position distanced for several
`meters or more.
`
`The PD 21 converts light signals received at each of light
`receiving areasto electrical signals, and outputs the electrical
`signals to the signal amplification circuit 23.
`The signal amplification circuit 23 amplifies the electrical
`signals input from the PD 21, and outputs the amplified elec-
`trical signals to a comparator 203 to be described later.
`Asfor the above described laser system 100, the laser beam
`emitted from the LD 11 is projected outside the casing 300 via
`the projection optical system 8, and then irradiated to other
`vehicle.
`The laser beams emitted from the LD 11 radiate into the
`horizontal direction (y-axis direction) and the vertical direc-
`tion (Z-axis direction) with a given divergence angle and
`enters the coupling lens 12, and the coupling lens 12 sets the
`laser beams to substantially parallel light.
`In this case, the divergence angle of projection light along
`the aZ plane can be determined based on a width of rectan-
`gular cross-section of light emission area of the LD 11 in the
`Z-axis direction and a focal length ofthe coupling lens 12, and
`this divergence angle defines a projection angle range along
`the aZ plane.
`Further, the cylindrical lens 13 having negative refractive
`powerin the y-axis direction is disposed after the coupling
`lens 12 (+c side), with which only the divergence angle along
`the ya plane canbesetfurther greater, in which the projection
`light is broader in the direction parallel to the XY plane.
`Further, the long side direction (y-axis direction) of rect-
`angular cross-section of light emission area of the LD 11 and
`the direction (y-axis direction) that the cylindrical lens 13 has
`negative refractive power can be matched. In this case, the
`divergence angle ofprojection light in the y-axis direction can
`be easily set greater, and the light intensityof projection light
`within the projection angle range along the ay plane can beset
`uniform. If the light intensity of projection light can be set
`uniform within the projection angle range, distance measure-
`ment precision for each divided area can be preferably set
`uniform whenthe projection angle range is divided.
`The laser beam reflected at other vehicle scatters at the
`
`reflection position (incidence position) to random directions
`(i.e., reflect diffusely), and only the laser beam (reflection
`light) coming back the sameoptical path of projection light
`can be guided to the PD 21 via the condensing lens 22.
`The projection angle range of laser beams of the laser
`system in the horizontal direction (X-axis direction) and the
`vertical direction (Z-axis direction) is defined by the diver-
`genceangle of projection lightin the horizontal direction and
`the vertical direction. Because the divergence angle depends
`on the long side direction width and the short side direction
`width of a rectangular cross-section of light emission area of
`LD,and a focal length of the projection optical system in the
`horizontal direction and the vertical direction, by adjusting
`each value, the laser beam having a desired divergence angle
`can be projected.
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`US 9,316,495 B2
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`7
`A part ofthe light reflected from other vehicle coming back
`along the sameoptical path that the projectionlight takes, and
`the reflection light condensedto the condensing lens 22 has a
`divergence angle whichis the samelevel of divergence angle
`of projection light in the horizontal direction andthe vertical
`direction. In this case, the reflection light passing through the
`condensinglens 22 enters the PD 21 while shifted to the y-axis
`direction and the Z-axis direction from the optical axis of the
`condensing lens 22 depending on the incidence angle to the
`condensing lens 22 (see FIG. 5).
`In view of such shifting, a plurality of light receiving areas
`is arrangedin the y-axis direction (horizontal direction) in the
`PD 21, which meansthat the light receiving faceis divided in
`the y-axis direction. With this configuration,
`information
`(hereinafter, distance computing information) for computing
`distance to a plurality of positions on a surface of other
`vehicle in the X-axis direction (horizontal direction) can be
`obtained one by one.
`Further, by adjusting a size ofthe entire light receiving face
`of the PD 21 in the y-axis direction and a focal length of the
`condensing lens 22, the light receiving angle range in the
`y-axis direction can be set. By setting the light receiving angle
`range sameas the above projection angle range in the y-axis
`direction, and dividing the light receiving face of the PD 21
`into a plurality of light receiving areas arranged in the y-axis
`direction and detecting light signal received by each area, the
`light receiving angle range can be divided.
`For example, in FIG.5,the light receiving face ofthe PD 21
`is divided into five areas in the horizontal direction. The
`
`The distance measurement map generation circuit 207 gen-
`erate map information by collecting distance information of
`each ofthe light receiving areas, and transmits map informa-
`tion to an electronic control unit (ECU) for vehicle control
`disposed at -Y side of the distance measurement apparatus
`1000.
`
`The light emission control circuit 201 outputs an emission
`signal to the LD drive circuit 9 at a given timing to control the
`emission timing of the LD 11.
`The comparator 203 compares the received light signal,
`output from eachofthe light receiving areas of the PD 21 via
`
`systems 100, the optical path of projection light and the
`optical path of reflection light can be assumed the sameopti-
`cal path in the laser system 100.
`The laser beam (reflection light) coming back to the laser
`system 100 can be condensed by the condensing lens 22 in the
`horizontal direction andthe vertical direction, and then enters
`the PD 21. The light receiving angle range in the horizontal
`reflection light entering parallel to the optical axis of the
`direction and the vertical direction can be set based onasize
`condensinglens 22 enters the center light receiving area in the
`of the light receiving face of the PD 21 and a focal length of
`y-axis direction via the condensing lens 22 (see a solid line in
`the condensing lens 22. By setting the light receiving angle
`FIG. 5). Further, the reflection light entering from a direction
`range substantially the same as the projection angle range of
`(oblique entering) crossing the optical axis of the condensing
`projection light, a noise signal occurrence causedby intrusion
`lens 22 (most+y side of light receiving angle range) enters the
`of ambientlight to the PD 21 can be suppressed, with which
`most —y side of the light receiving areas via the condensing
`distance measurementcan be conducted with high precision.
`lens 22 (see a broken line of FIG. 5). Further, the reflection
`Further, to secure thelight receiving angle range extending
`light entering from a direction (oblique entering) crossing the
`in the horizontal direction, the light receiving face shape of
`optical axis of the condensing lens 22 (most —y side of light
`the PD 21 has a long shapein the horizontal direction (y-axis
`receiving angle range) enters the most +y side of the light
`direction). The light receiving angle range in the y-axisdirec-
`receiving areas via the condensing lens 22 (see an alternate
`tion can be determined based on a total width of the light
`long and short dash line of FIG. 5).
`receiving face of the PD 21 in the y-axis direction and the
`Referring back to FIG.1, the control circuit 200 is disposed
`focal length of the condensing lens 22. The total width of the
`at -Y side of the two laser system