CUOAOA
`
`United States Patent
`Kobayashiet al.
`
`15)
`
`[11]
`
`[45]
`
`US005426294A
`Patent Number:
`Date of Patent:
`
`5,426,294
`Jun. 20, 1995
`
`[54] GLARE SENSOR FOR A VEHICLE
`
`[75]
`
`Inventors: Shoji Kobayashi; Toshihisa Hayami;
`Masaaki Ishikawa, all of Shizuoka,
`Japan
`
`[73] Assignee: Koito Manufacturing Co., Ltd.,
`Tokyo, Japan
`
`[21] Appl. No.: 67,097
`
`[22] Filed:
`
`May26, 1993
`
`Foreign Application Priority Data
`[30]
`May 27, 1992 [JP]
`Japan vecsscssscsssscssssesseen 4.041905 U
`
`ewes 4146027
`Jun. 5, 1992 [JP]
`Japan...
`May 14, 1993 [JP]
`Japan oes eeesecsecessseneneee 5-136920
`
`P51]
`Tint. C16 oeeee ecesseseessectsseceseseeeneens B60Q 1/14
`
`[52] US. Ch. oiecccseesesccsccssssseeseeenneseen 250/226; 250/205
`[58] Field of Search .................. 250/226, 205, 208.1,
`250/208.2, 214 D, 214 AL, 216; 356/218, 221,
`222, 225
`
`[56}
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`1/1989 Gahan .
`4,799,768
`1/1990 Matsumotoetal. .
`4,891,559
`5,235,178 8/1993 Hegyi csvseeceessssssecssseereereen 250/226
`
`FOREIGN PATENT DOCUMENTS
`
`0230620 12/1986 European Pat. Off.
`3217227 11/1982 Germany .
`3428364 2/1986 Germany .
`3936120
`5/1991 Germany .
`
`.
`
`Primary Examiner—David C. Nelms
`Assistant Examiner—John R. Lee
`Attorney, Agent, or Firm—Sughrue, Mion, Zinn,
`Macpeak & Seas
`
`ABSTRACT
`(57)
`A glare sensor includes a light condensing means for
`condensing light beams from the fore scene and photo
`sensing element for sensing the light beams from the
`light condensing means. The photo sensing elementis
`constructed with photodiodes. Blue filters are selec-
`tively coupled with the photodiodes. With provision of
`the blue filters, the glare sensor is able to discriminate
`red light from white light or yellow light. The output
`signals of the photodiodes with the blue filters and the
`photodiodes with no filters are used for detecting the
`direction and color of the light coming from the fore
`scene. Withthis, the glare sensoris capable ofdetecting
`forerunning cars, oppositely running cars and traffic
`lights.
`
`35 Claims, 10 Drawing Sheets
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`
`

`

`U.S. Patent
`
`June 20, 1995
`
`Sheet 1 of 10
`
`5,426,294
`
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`

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`U.S. Patent
`
`June 20, 1995
`
`Sheet 2 of 10
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`5,426,294
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`Sheet 3 of 10
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`June 20, 1995
`
`5,426,294
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`U.S. Patent
`
`June 20, 1995
`
`Sheet 4 of 10
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`5,426,294
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`

`U.S. Patent
`
`June 20,1995
`
`Sheet 5 of 10
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`5,426,294
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`U.S. Patent
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`June 20, 1995
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`Sheet6 of 10
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`5,426,294
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`U.S. Patent
`
`June 20, 1995
`
`Sheet 7 of 10
`
`5,426,294
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`FIG.
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`16A
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`

`

`U.S. Patent
`
`June 20, 1995
`
`Sheet 8 of 10
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`5,426,294
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`U.S. Patent
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`June 20, 1995
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`Sheet 9 of 10
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`U.S. Patent
`
`June 20, 1995
`
`Sheet 10 of 10
`
`5,426,294
`
`FIG. 22
`
`DETECTOR
`
`TURN -ANGLE
`
`

`

`1
`
`GLARE SENSOR FOR A VEHICLE
`
`5,426,294
`
`BACKGROUND OF.THE INVENTION
`The present invention relates to a glare sensor for
`detecting forerunning vehicles, oppositely running ve-
`hicles and traffic lights and, more particularly, the in-
`vention relates to a glare sensor for detecting colors of
`light beam emitted from front side of vehicles, traffic
`lights or the like.
`Many proposals have been made ofthe car-carried
`devices, which automatically changes the intensity and-
`/or direction of light beamsso as to give no glare to the
`drivers of forerunning cars and cars running in the op-
`posite direction. When the oppositely running car is
`present, the devicetilts the light beamsof the head lamp
`to the left. When the forerunningcaris present, the light
`beamsare furthertilted downward.
`To switch thelight distribution pattern, the forerun-
`ning cars and the oppositely running cars must be dis-
`criminatively recognized accurately. In the prior tech-
`nique, the discriminative recognition of those objects
`depends on the brightness of incoming light from the
`objects. However, the technique fails to discriminate
`light from the car from light of others. Further, it is
`almost impossible to discriminate the forerunning car
`from the oppositely running car. Therefore, the light
`distribution characteristic of the head lamp cannot be
`properly adjusted. This makes it difficult to put the
`devices into practice.
`
`SUMMARYOF THE INVENTION
`
`For the above background reasons, the present inven-
`tion has an object to provide a glare sensor which is
`capable of discriminatively detecting forerunning cars,
`oppositely running cars and otherlight emitting objects
`than cars, such as street lamps, lamps or private houses,
`andtraffic lights (referred to traffic lights and the like).
`The glare sensor comprises a light condensing means
`for condensing light beams from the fore scene and
`photo sensing elements for sensing the light beams from
`the light condensing means. The photo sensing element
`is able to discriminate red light from at least white light
`or yellow light.
`The photo sensing elements are arrayed in a matrix
`fashion. The output signals of the photodiodes are used
`for detecting the direction and colorofthe light coming
`from the fore scene. Therefore, the glare sensoris capa-
`ble of detecting forerunning cars, oppositely running
`cars andtraffic lights.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG.1Ais a cross sectional view showing an optical
`system of a glare sensor according to an embodiment of
`the present invention;
`FIG.1B is an enlarged, cross sectional view showing
`a photosensorarray ofthe glare sensor;
`FIG. 2 is a view schematically showing a car carry-
`ing a glare sensorof the invention mountedat a specific
`location;
`FIG.3 is a view showing a modelof the scene present
`ahead ofa car;
`FIG.4 is a cross sectional view showing a modifica-
`tion of the photosensor array used in the first embodi-
`mentof the invention;
`
`30
`
`35
`
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`FIG. 5 is a cross sectional view showing an optical
`system of a glare sensor according to another embodi-
`ment of the present invention;
`FIG. 6Ais a plan view showing an optical system of
`a glare sensor according to yet another embodiment of
`the present invention;
`FIG.6B is a side view showingthe optical system of
`the glare sensor of FIG. 6A;
`FIG.7 is a cross sectional view showing a modifica-
`tion of the optical system of the flare sensor of FIG.6;
`FIG.8A is a front view showing an optical system of
`a glare sensor according to still another embodiment of
`the present invention;
`FIG.8Bis a plan view showing the optical system of
`the glare sensor of FIG. 8A;
`FIG.8C is a cross sectional view showingthe optical
`system of the glare sensor of FIG. 8A when viewed
`from theside;
`FIG.9Ais a plan view showing a light guide lensis
`used instead of the optical fiber pairs, which forms a
`modification of the embodiment of FIG. 8;
`FIG.9Bis a front view showing the light guide lens
`of FIG. 9A;
`FIG. 10A is a cross sectional view showing a glare
`sensor incorporating the present invention;
`FIG. 10B is a cross sectional view showing another
`glare sensor incorporating the present invention;
`FIG.11 is a view schematically showing a car carry-
`ing the glare sensors shown in FIG. 10 mounted at two
`specific locations;
`FIG.12 is a longitudinal sectional view showing an
`optical system of a glare sensor in use with a car accord-
`ing to an additional embodiment of the present inven-
`tion;
`FIG.13 is an enlarged cross sectional view showing
`a lens drive section of the glare sensor of FIG. 12;
`FIG. 14 is a front view showing the CCD image
`pickup element used in the glare sensor;
`FIG.15 is a diagram showing an image formed on the
`surface of the CCD imagepickup element;
`FIGS. 16A and 16B cooperate to show how to mea-
`sure a car-to-car distance;
`FIG. 17 is a longitudinal sectional view showing a
`glare sensor according to a further embodimentof the
`present invention;
`FIG. 18 is a cross sectional view showing the glare
`sensor of FIG. 17;
`FIG. 19 is a longitudinal sectional view showing a
`glare sensor according to another embodiment of the
`present invention;
`FIG.20 is a cross sectional view showing the glare
`sensor of FIG. 19;
`FIG. 21 is a perspective view showing the internal
`structure of a head lamp accordingto still another em-
`bodimentof the present invention;
`FIG.22 is a view showing the shape of a shade;
`FIG.23 is a view showinga light distribution pattern
`of the head lamp of FIG.21; and
`FIG.24 is a block diagram showing a motordriver.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`65
`
`The preferred embodiments of the present invention
`will be described with reference to the accompanying
`drawings. As shown in FIG. 1A showing in cross sec-
`tion the structure of a glare sensor according to an
`embodiment of the present invention, a glare sensor 1,
`contained in a tubular casing 5, is comprised of an image
`
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`forming lens 2 for condensing light received from the
`scene. Theelectrical signals produced by the photodi-
`odes 7, which receive the light coming from another
`scene seen ahead of a car and focussing the received
`light on an imageplane,a flare stop 3, and a photosensor
`region in the fore scene located below the horizon H
`and ontheleft side of the vertical center line V, contain
`array 4 disposed on the image plane of the image form-
`information of colorlight emitted from private housings
`ing lens 2. The photosensor array 4, as shown in FIG.
`located on the left side of the road. When the ampli-
`1B, consists of a number of minute photodiodes 7 ma-
`tudes of the electrical signals output from the photodi-
`trix-arrayed at a high density on a planar substrate 6.
`The photodiodes 7, of which the spectral sensitivities
`odes 76 with nofilters, which receive the light coming
`for white light are substantially uniform, produceelec-
`from this scenic region, are larger than those of the
`trical signals according to the brightness of imagelight
`electrical signals from the specific photodiodes 7@ with
`formed by the image forming lens 2. Filters 8 of blue
`the bluefilters 8, it is understood that the tail lamps of
`color, for example, cyan, are layered on the front faces
`the forerunning cars are present.
`The cars running this side and the forerunning car
`ofthe selected photodiodes 7a alternately arrayed. The
`filters 8 shut off red light, which is the complementary
`can be known bydetecting the light coming from the
`colorof the blue color. Therefore, the selected photodi-
`fore scene of a car in this way. Accordingly, if the head
`lamp is switched from the high beam to the low beam
`odes 7a are insensitive to red light or produceslittle
`electrical signals when receiving red light.
`according to the light detection results, it is possible to
`The glare sensor 1 thus constructed is mounted at or
`eliminate the dazzling problem ofthe driver of the op-
`near to a location of the front bumper of a car C as
`positely running car. Further, if the light beam of the
`shownin FIG.2. Light coming from the scenein front
`head lampis tilted to the left and downward, the nui-
`of the caris limited in its passing area by the flare stop,
`sance to the driver of the forerunning car can be mini-
`mized.
`and imaged on the photosensor array 4 by the image
`forming lens 2. Upon receipt of the image light, the
`The photosensor array in the glare sensor may be
`modified into the construction as shown in FIG.4. As
`individual photodiodes 7 of the photosensor array 4
`produceelectrical signals. In this case, white light con-
`shown, in a photosensor array 104 of the modification,
`photodiodes 7a with blue filters 8 and photodiodes 7
`tained in the receivedlight directly hits the photodiodes
`7a and 7b to cause them to generate electrical signals,
`with red filters 9 are alternately arrayed. When the
`but the red light substantially fails to reach the photodi-
`photosensorarray 104 receives the light from tail lamp
`odes 7a to cause them to generate little electrical sig-
`of the forerunningcar, the ratio of the electrical signals
`nals.
`output from the photodiodes 7a with the blue filters 8 to
`Through measurementof distributions of amplitudes
`those from the photodiodes 74 with red filters 9 is great.
`of electrical signals from the specific photodiodes 7a
`Comparison of those outputsignals will ensure a further
`with the blue filters and those from the photodiodes 7
`reliable detection of the forerunning cars and the cars
`with no filters, it is possible to discriminately know the
`running this side.
`typesof the light coming from the fore scene,light from
`FIG.5 is a cross sectional view showing an optical
`the head lamp of the car running in the opposite direc-
`system of a glare sensor according to another embodi-
`tion, light from the tail lamp from the forerunning car,
`ment of the present invention. In the figure, reference
`or light from the traffic light.
`numeral 2 designates an image forming lens 3 represents
`a flare stop. A beam splitter 10 consisting of a half-mir-
`A scene present in front of a car is illustrated as a
`model in FIG. 3. As shown, oppositely running cars Cl
`ror, for example, is located in the poststage of the flare
`and forerunning cars C2 are present below the horizon
`stop 3. The incominglight beam is split into two beams,
`H,andtraffic lights L Gncluding street lamps) above the
`which travel in two directions to reach photosensor
`horizon H. Below the horizon H twoforerunning cars
`arrays 104A and 104B. The photosensor arrays 104A
`C2 are present at near the vertical center line V and on
`and 104B each consist of a number of minute photodi-
`odes arrayed at a high density in a matrix fashion. A
`the left side thereof, and two cars Ci run on the right
`side of the vertical center line V. Light coming from the
`filter 8 of blue color is located in the prestage of the
`fore scene containing the cars and traffic lights is re-
`photosensor array 204A. Nofilter is provided in the
`prestage of the photosensor array 204B. Reference nu-
`ceived by the photodiodes 7, which are set at the loca-
`tion corresponding to the horizon H—the vertical cen-
`meral 205 is representative of a casing.
`ter line V. Amplitudes of the electrical signals gener-
`The glare sensor thus constructed,like that of the first
`ated by the photodiodes 7 are measured. Accordingly,
`embodiment, is capable of detecting forerunning cars,
`the electrical signals generated by the photodiodes 7
`the oppositely running cars, traffic lights, and the like
`when receiving the light coming from the scene above
`by using the output signals of the photosensor array
`the horizon H contain those signals representative of
`204A associated with the blue filter 8 and the photosen-
`white light and yellow light. When the amplitudes of
`sor array 204B associated with nofilter.
`the electrical signals produced by the photodiodes 76
`It is noted that in the construction of the glare sensor,
`with no filters are larger than those of the electrical
`the signals output from all of the photodiodes of the
`signals by the specific photodiodes 7a with the blue
`photosensorarrays can be used. Accordingly, the signal
`filters 8, the signals representative of red light are pres-
`level of the outputsignals of those photosensorarraysis
`ent.
`high. The detection of thestate of the fore scene is more
`exact andreliable.
`Theelectrical signals produced by the photodiodes7,
`which receive the light coming from the region in the
`The beam splitter 10 may have a wavelength select
`fore scene located below the horizon H and ontheright
`function. For example, if the beam splitter 10 is de-
`side ofthe vertical center line V, contain color informa-
`signed so as to allow light of blue color to pass there-
`through, the blue filter 8 is omissible.
`tion of white and yellow. The light of those colors is
`emitted by the head lamps of the oppositely running
`FIGS.6A and 6B are plan and side views showing an
`cars. Therefore, it is understood that the cars running
`' optical system of a glare sensor according to yet an-
`toward this side are present in that region of the fore
`other embodimentof the present invention. In this em-
`
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`bodiment, a Fresnel lens 2A is used as an image forming
`lens. The end faces of a numberofoptical fibers 11 are
`matrix arrayed on the image forming planeof the Fres-
`nel lens. The other endfaces of the optical fibers 11 are
`disposed facing a photosensor array 4B, viz., paired
`photodiodes 7a and 76. Each photodiode pair consists
`of a photodiode 7a with a bluefilter 8 provided on the
`front side, and another photodiode 7b with nofilter.
`In the glare sensor thus constructed, an image pattern
`formed by the Fresnel lens 2A is rearranged by the
`optical fiber 11, and the rearranged pattern is detected
`by the photosensorarray 4B. Accordingly, the first end
`faces of the optical fibers 11 are arrayed in a matrix
`fashion, but the second endfaces may be arranged prop-
`erly. Therefore, the photodiodes 7 may be properly
`arranged in the photosensor array 4B.
`Theglare sensor of this embodimentis likewise capa-
`ble of detecting the objects, such as forerunning cars,
`oppositely running cars, and traffic lights, in the fore
`scene ofa car.
`The glare.sensor of FIG. 6 may be modified to have
`the construction as shown in FIG. 7. As shown,in this
`flare sensor, a normal planoconvexlensis used for the
`image forming lens. A beam splitter 12 as a triangle
`prism is located facing the second endface ofan optical
`fiber 311. The light beams emanating from the beam
`splitter 12 are focused on photosensor arrays 304A and
`304B, respectively. In this case, a bluefilter 308 is pref-
`erably disposed on the fore side of the photosensor
`array 304B. In theillustration, no filter is disposed on
`the fore side of the photosensor array 304A.If required,
`a red filter may be located there.
`FIGS. 8A to 8C show front, plan and cross sectional
`views showing an optical system of a glare sensor ac-
`cording to still another embodiment of the present in-
`vention. In this embodiment, a plural number of image
`forming lenses 402 are arrayed side by side as shown.
`Optical fiber pairs 411 each consisting of optical fibers
`41la and 4110 are disposed in a state that the first end
`faces of each pair of optical fibers are opposed to the
`corresponding image forming lens 402, and the second
`end faces thereof are coupled with beam splitters 13,
`respectively. Photosensor arrays 404A and 404B, dis-
`posed at a right angle, face the different sides of the
`beam splitter 13, as shown. With the construction, light
`beams coming from the fore sceneofa car in the differ-
`ent directions are respectively guided through thedif-
`ferent optical fibers 411¢ and 4110 to the different pho-
`tosensor arrays 404A and 404B. The photodiodesof the
`photosensor arrays 404A and 404B areselectively cou-
`pled with blue filters and red filters (not shown). Refer-
`ence numeral 14 designates an optical fiber support.
`With the above-mentioned construction of the glare
`sensor, it is possible to discriminate the white or yellow
`light from the red light, to detect the direction of the
`incoming light, and the oppositely running cars, fore-
`running cars, andtraffic lights on the basis of the output
`signals of the photodiodes with the blue andredfilters.
`In the glare sensor of FIG. 8, the optical fiber pair
`may be substituted by a light guide lens 15 formed of 60
`transparent resin. Lens pieces constituting the light
`guide front side, as shown. The photodiodes, which are
`respectively disposed in opposition to the lens pieces,
`can receive light beams coming throughthe fore scene
`in different directions. Reference numeral 16 indicates a
`light-shield film.
`FIG.11 is a view schematically showing a car carry-
`ing the glare sensors shown in FIG. 10 mounted at two
`
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`
`6
`specific locations; Two types of glare sensorsare illus-
`trated in FIG. 10. Thefirst glare sensor 1A shown in
`FIG. 10A is made up of an image forminglens2,a flare
`stop 3, and a photosensor array 4. The second glare
`sensor 1B shown in FIG. 10B is made up of an image
`forminglens2, a flare stop 3, a blue filter 8, and a photo-
`sensor array 4. The photosensor arrays of those glare
`sensors may be those shown in FIG. 1B or4. The glare
`sensor 1B havingthe blue filter and the glare sensor 1A
`having nofilter may be respectively mountedata loca-
`tion of the front bumperof a car C andat a location near
`the window shield, as shown in FIG.11.
`The image forming lenses 2 of the glare sensor 1A
`and 1B are directed in the running direction. The glare
`sensor 1B having the blue filter receives the upward
`light beam, while the glare sensor 1A having nofilter
`receives both the upward and downward light beams.
`Accordingly, the light beams coming from the fore
`scene of a car can be more properly detected.
`In FIGS. 12 through 14 showing a glare sensor ac-
`cording to an additional embodiment of the present
`invention, FIG. 12 is a longitudinal sectional view
`showing an optical system of a glare sensor in use with
`a car according to an additional embodiment of the
`present invention. FIG. 13 is an enlarged cross sectional
`view showinga lens drive section of the glare sensor of
`FIG.12.
`A zoom objective 501,fit into a tubular portion 503 of
`a casing 502,includesa first lens system fixed at the fore
`end of the tubular portion 503 and a second lens system,
`which is moved with respectto the first lens system by
`a lens driver 504. Thefirst lens system consists ofa fixed
`lens 505 as a planoconvex lens. The secondlens system
`includes a movable lens 507 as a planoconcave lens,
`whichis fastened to a slide tube 506. Theslide tube 506
`is slidable parallel to the optical axis L of the fixed lens
`505 with respect to the tubular portion 503.
`Theslide tube 506 is movable along the optical axis L
`by a lens driver 504 to be given later. It moves the
`movable lens 507 along the optical axis L with respect
`to the fixed lens 505, thereby changing the focal posi-
`tion of the zoom objective 501. Thefirst lens system and
`the second lens system of the zoom objective 501 may
`properly be combined. In this embodiment, the plano-
`convex lens is used for the fixed lens 505 of the first lens
`system and the planoconcavelens, for the movable lens
`507 in the second lens system, in order to remove the
`color aberration.
`A beamsplitter 508, constructed with a half-mirrorof.
`the multilayer film structure, is provided on the rear
`side of the fixed lens 505 and on the optical axis L. The
`beam splitter 508 is slanted at an angle of 45° to the
`optical axis L. A CCD image pickup element510 lies on
`the optical axis L1 on the rear side of the beam splitter
`508. A red filter 509 is located in front of the CCD
`image pickup element 510. Another CCD image pickup
`element 512 lies on another optical axis L2 on the rear
`side of the beam splitter 508. A bluefilter 511 is located
`in front of the CCD image pickup element 512. The
`image pickup surface of each of the CCD image pickup
`elements 510 and 512 has preferably such a rectangular
`shape that it is asymmetrical with respect to the hori-
`zontal axis H, viz., the upper part thereofis larger than
`the lower part, as shownin FIG. 14.
`Theinner surface of the fixed lens 505 is coated with
`an infrared-rays cut film 513 as a thin film of the type
`which allowslight to selectively transmit therethrough.
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`5,426,294
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`the CCD imagepickup element 510 lying on the trans-
`mission optical axis L1 (FIG. 16).
`Assuming that the focal distance ofthe fixed lens 505
`is f1, the focal distance of the movable lens 507is f2, and
`the distance between both lensesis d, the focal distance
`f of the movable lens 507 when both the lenses are
`combined is
`
`7
`Thestructure of the lens driver 504 follows. A cou-
`pling pin 514 is protruded from a slide tube 506. An
`elongated hole 515 elongating in the optical axis L is
`formedin the tubular portion 503 of the casing. A heli-
`cal tube 516 with a helical groove 517 is rotatably cou-
`pled with the tubular portion 503. The coupling pin 514
`is upstanding passing through the elongated hole 515
`and slidably coupled with the helical groove 517. A
`gear 518 is provided on the outer surface of the end of
`the helical tube 516. A drive gear 520 is fastened to the
`drive shaft of a reversible motor 519, which is tightly
`mounted on the casing 502 by means of screws. The
`gear 518 is in mesh with the drive gear 520. When the
`control motor 519 turns, the coupling pin 514 coupled
`with the helical groove 517 is movedin thedirection of
`the tube axis, through the gear mechanism. As a conse-
`quence, the movable lens 507 is moved forward and
`backward along the optical axis L.
`In the operation of the glare sensor thus constructed,
`the lens driver 504 moves the movable lens 507 of the
`zoom objective 501 in accordance with a distance of a
`measuring car and a measured car. With the movement
`of the movablelens 507, the focal position of the lensis
`adjusted so as to form images on the CCD image pickup
`elements 510 and 512 (FIG.15). The car-to-car distance
`is measured by a infrared-rays distance measuring in-
`strument 521. A controller 522 controls the control
`motor 519 so as to turn by an angle, which depends on
`the measured value. As a result, the movable lens 507is
`movedto a preset position by the helical mechanism.
`The controller also carries out the following control
`process. When the CCD image pickup element 510,
`which lies on the transmission optical axis L1, picks up
`a lamp image TL,the light beam from the head lamp of
`the measuring car is tilted downward. When the CCD
`image pickup element 512, which lies on the reflection
`optical axis L2, picks up a lamp image HL,the control-
`ler recognizes it as “head lamp of the oppositely run-
`ning car”, andtilts the light beam form the head lamp of
`the measuring car to the left (under the keep-to-the-
`right rule).
`Theinfrared-rays distance measuring instrument 521
`operates as follows. A transmitter/receiver section of
`the instrument 521 emits forward a near-infrared, pulsa-
`tive laser beam, and receives laser beam reflected from
`the reflectorof the rear side of-a forerunning car or the
`front side of an oppositely running car. The distance
`measuring instrument 521 halves the time between the
`transmission and reception of the laser beam, and out-
`puts it as the distance of the measuring car and the
`measured car.
`When a car to be measuredis present at a great dis-
`tance, the movable lens 507 is controlled so as to ap-
`proachto the fixed lens 505 (as indicated by a solid line
`in FIG. 12), and forms the lamp imageof the forerun-
`ning car or the oppositely running car on the CCD
`image pickup elements 510 and 512. Such a control of
`the movable lens 507 makes the images on the CCD
`image pickup elements clear. Further, the image of the
`measured car, whenit is at a long distance, is enlarged.
`In this respect, the object discrimination performanceis
`improved.
`Theinfrared-rays distance measuring instrument 521
`is used for the car-to-car distance measurement. In this
`instance of the embodiment, the forerunning car and the
`oppositely running car are present as the measuredcars.
`The distance D can also be gained using the image on
`
`1/f=1/f1—a)+1/42/
`
`10
`
`The theoretical distancef is
`
`1/f=1/1+1/n—-d/Axp
`
`In a case where, as shownin FIG. 16A, a lamp image G
`is present at a location h higher than the horizon H
`passing through the optical axis O of the surface of the
`CCD image pickup element 510, the following equa-
`tions hold
`
`fXtan @=h
`
`tan =(HS—HL)/D
`
`where HS:height of the sensor mounted
`
`HL:height of the lamp mounted
`
`Rearranging the above equations for the distance D
`between the measuring and measured cars, we can gain
`the distance D. Undercontrol of the controller 522, the
`lens driver 504 is driven to set the movable lens 507 at
`a desired position.
`In the measurement of the distance D by using the
`CCD image pickup element 510, a plural number of
`light emitting objects (amps) frequently appear on the
`surface of the CCD image pickup element 510. In this
`case, the image having the highest brightnessis selected
`and image processed, and then the distance calculating
`process is carried out.
`A glare sensor according to a further embodiment of
`the present invention will be described with reference
`to FIGS. 17 and 18.
`The glare sensor of this embodiment consists of three
`sensor sections, a long-distance sensor section, a medi-
`um-distance sensor section, and a short-distance sensor
`section. The long distance sensor section contains a
`fixed lens 501@ (planoconvexlens) for the long distance
`measurement, a beam splitter 508 and two CCD image
`pickup elements 510 and 512. The fixed lens 501a serves
`as an objective, which corresponds to the zoom objec-
`tive in the previous embodiment. The beam splitter 508
`and the CCD image pickup elements 510 and 512 are
`located on the rearside of the objective as in the previ-
`ous embodiment. The medium-distance sensor section
`and the short-distance sensor section contain fixed
`lenses 5014 and 501c (planoconvexlenses) as objectives,
`and are constructed as the long-distance sensor section.
`In the glare sensor using the fixed lenses 501a, 501b
`and 501c as objectives, image angles w1, w2, and w3 are
`different depending on the distance between the mea-
`suring car and the measuredcar (the image angle for the
`long distance is larger than those for the medium and
`short distance). The resultant images are substantially
`equal in size.
`The long-, medium- and short distance sensor sec-
`tions are selectively operated depending on the car-to-
`car distance, so that the images formed on the surface of
`the CCD image pickup elements 510 and 512 are always
`
`45
`
`60
`
`65
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`5,426,294
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`20
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`9
`clear. Further, the image of the measured car at a long
`distance is not reduced in size whenit is formed on the
`CCDelement surface. Accordingly, the object discrim-
`ination performanceis improved.
`A glare sensor according to another embodiment of 5
`the present invention will be described with reference
`to FIGS. 19 and 20.
`In this embodiment, a numberof optical fibers 523
`(may be substituted by the light guide lens) optically
`couple the focal planepositions (indicated by arrows A)
`of the fixed lenses 501a and 501with the beam splitter
`508. The glare sensor consists of a pair of long-distance
`sensor sections and a pair of short-distance sensor sec-
`tions.
`In this embodiment, the optical fibers 523 provide
`light paths between thefocal plane positions of the fixed
`lenses 501¢ and 501d and the beam splitter 508. Accord-
`ingly, if the focal plane position A of the long-distance
`sensorsection pairis different from that of the short-dis-
`tance sensor section pair, the quantity of light incident
`on the CCD image pickup elements 510 and 512
`through the beam splitter 508 can be kept substantially
`constant.
`
`w5
`
`FIG. 21 is a perspective view showing the internal
`structure of a head lamp according tostill another em-
`bodiment of the present invention. FIG. 22 is a view
`showing the shape of a shade. FIG. 23 is a view show-
`ing a light distribution pattern of the head lamp of FIG.
`21. FIG. 24 is a block diagram showing a motordriver. 30
`In those figures, a light projection unit 610, supported
`by an aiming mechanism (not shown), is contained in a
`capsule-like Jamp body (not shown). Althoughnotillus-
`trated, the light projection unit 610 is tiltable vertically
`and horizontally by the aiming mechanism. Accord-
`ingly, the direction of the light beam emitted from the
`light projection unit 610, viz., the light projection axis
`(optical axis) of the head lamp,can be tilted vertically
`and horizontally by operating the aiming mechanism.
`In the light projection unit 610, a reflector 614 and a
`projection lens 616 form a single unit. The reflector 614,
`which is substantially elliptical, receives a discharge
`bulb 612. The projection lens 616 is located in front of
`the reflector 614. The projection lens 616 is supported
`by a lens holder, not shown, fastened to the reflector
`614 by means of screws. Aluminum is vapor deposited
`on the inner side of the reflecto