United States Patent [191
`Asayama
`
`lllllllllllllllllllllllllllIlllllllllIlllllllllllllllllllllllllllllllllllll
`5,214,408
`May 25, 1993
`
`US005214408A
`[11] Patent Number:
`[45] Date of Patent:
`
`[54] DISTANCE DETECTING APPARATUS FOR A
`VEHICLE
`Yoshiaki Asayama, Himeji, Japan
`[75] Inventor:
`[73] Assignee:
`Mitsubishi Denki Kabushiki Kaisha,
`Tokyo, Japan
`[21] Appl. N0.: 782,110
`[22] Filed:
`Oct. 24, 1991
`[30]
`Foreign Application Priority Data
`Oct. 25, 1990 [JP]
`Japan ................................ .. 2~290469
`Nov. 28, 1990 [JP]
`Japan ................................ .. 2435430
`
`[51] Int. Cl.5 ........................ .. B60Q 1/00; G086 1/16
`[52] US. Cl. .................................. .. 340/435; 340/436;
`340/901; 340/903; 340/939; 340/555; 340/942;
`358/105; 358/125; 180/169; 180/167; 342/55;
`342/66; 342/69
`[58] Field of Search ............. .. 340/435, 903, 937, 901,
`340/436, 555, 556, 937, 961; 358/107-113, 125;
`180/167-169, 271; 342/47, 55, 66, 126, 118, 69,
`450, 451
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`4,539,590 9/1985 Gage ................................. .. 358/107
`4,709,264 11/1987 Tamura et a1v
`.... .. 358/93
`4,779,095 l0/l988 Guerreri ........ ..
`340/904
`4,908,704 3/1990 Fujioka et a1. ................ .. 358/108
`‘ 5,026,153 6/1991 Suzuki et al. ..................... .. 340/903
`
`FOREIGN PATENT DOCUMENTS
`
`55-15337 4/1980 Japan .
`
`57-49841 10/1982 Japan.
`63-18122 4/1988 Japan .
`63-38085 7/1988 Japan.
`63-64363 12/1988 Japan .
`l-l222l 4/1989 Japan.
`
`Primary Examiner-Donnie L. Crosland
`Attorney, Agent, or Firm-Sughrue, Mion, Zinn,
`Macpeak and Seas
`ABSTRACT
`[57]
`A distance detecting apparatus enables the driver of a
`vehicle to readily and concurrently recognize the loca
`tion and direction of each of a plurality of objects pres
`ent in the driver’s ?eld of view, in daylight or darkness,
`and at the same time determine whether each of the
`objects is an obstacle to the vehicle travel. The objects
`sensed by a pair of ?rst and second image sensors 3, 4
`are displayed on a screen 11 in a plurality of windows
`15—l9. Deviations between the images of the objects
`within the respective windows are electrically detected
`so that the distance to an object within each window is
`individually calculated based on the deviations. Obsta
`cles to the travel of the vehicle can be discriminated on
`the basis of the positions of the windows on the screen
`and the distances to the objects in the respective win
`dows as detected. Infrared light can be projected onto
`objects present within the ?elds of view of the image
`sensors when natural visible light is insufficient for the
`image sensors which, in this case, are sensitive to infra
`red light.
`
`8 Claims, 6 Drawing Sheets
`
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`Mercedes-Benz USA, LLC, Petitioner - Ex. 1006
`
`

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`US. Patent
`US. Patent
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`May 25, 1993
`May 25,1993
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`Sheet 1 of 6
`Sheet 1 of 6
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`5,214,408 _
`5,214,408 _
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`WINDOWDEFININGMEANS
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`MEMORY
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` A/DONVERTER
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`FIG.
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`

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`US. Patent
`US. Patent
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`May 25, 1993
`May 25, 1993
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`Sheet 2 of 6
`Sheet 2 of 6
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`5,214,408
`5,214,408
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`FIG.2
`FIG.2
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`US. Patent
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`May 25, 1993
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`Sheet 3 of 6
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`5,214,408
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`F l G . 4 (o)
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`US. Patent
`US. Patent
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`May 25, 1993
`May 25, 1993
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`Sheet 4 of 6
`Sheet 4 of 6
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`5,214,408
`5,214,408
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`US. Patent
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`May 25, 1993
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`Sheet 5 of 6
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`5,214,408
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`US. Patent
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`May 25, 1993
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`Sheet 6 of 6
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`5,214,408
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`F IG . 8
`PRIOR ART
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`

`1
`
`DISTANCE DETECTING APPARATUS FOR A
`VEHICLE
`
`5,214,408
`2
`Moreover, if there are many objects within the ?eld
`of view of the image sensors, it is unclear to which
`object the distance from the subject vehicle is being'
`detected. In particular, let us assume that the distance to
`an object in the form of a preceding vehicle is detected
`by the above-described distance detecting apparatus
`mounted on the subject vehicle during the travel
`thereof. In this case, if another vehicle travelling on one
`of plural lanes of a road adjacent the one on which the
`subject vehicle is travelling comes into the ?eld of view
`of the image sensors, it is not clear at all or the driver
`cannot tell to which vehicle (i.e., travelling on the same
`lane or on an adjacent lane) the distance is detected.
`Furthermore, in cases where the brightness or magni
`tude of external light is insuf?cient for proper distance
`detection by image sensors such as when the vehicle
`travels in a tunnel or in dark weather such as in the
`evening, twilight, etc., it is necessary to use a light emit
`ting element which projects a beam of visible light
`toward a preceding vehicle. In this case, however, there
`is a fear that the passengers including the driver in the
`preceding vehicle are dazzled by the light from the light
`emitting element, making it dif?cult for the driver to
`properly maneuver his or her vehicle in a safe manner.
`
`20
`
`BACKGROUND OF THE INVENTION
`The present invention relates to an apparatus for
`optically measuring the distance from a vehicle to ob
`jects such as obstacles lying ahead thereof as well as
`other vehicles which are travelling ahead of the vehicle
`or approaching it from behind.
`Some examples of an obstacle detecting apparatus are
`disclosed in Japanese Patent Laid-Open 55-15337 and
`Japanese Utility Model Laid-Open l-l222l. These ap
`paratuses project ultrasonic waves or electromagnetic
`waves in a speci?ed forward or backward direction to
`be detected and receive re?ected waves from an object
`or obstacle for the purpose of determining the presence
`or absence of an obstacle as well as measuring the dis
`tance thereto.
`Examples of an optical distance detecting apparatus
`utilizing image sensors are known from Japanese Patent
`Publication Nos. 63-38085 and 63-46363. As illustrated
`in FIG. 8, the apparatuses disclosed therein commonly
`have a pair of ?rst and second parallel optical systems
`having two convex lenses 101, 102 disposed in a hori
`zontally aligned relation at a prescribed distance L
`away from each other. A pair of separate image sensors
`103, 104 are horizontally disposed at focal points of the
`lenses 101, 102 at a distance f from the locations of
`corresponding lenses 101, 102, respectively, for generat
`ing respective image signals to a common signal proces
`sor 120. The signal processor 120 successively shifts the
`image signals from the image sensors 103, 104 and elec
`trically superposes them one over the other, so that the
`distance R from the lenses 101, 102 to an object 121 is
`calculated based on the principle of triangulation using
`the following formula:
`
`25
`
`SUMMARY OF THE INVENTION
`Accordingly, the present invention is intended to
`overcome the above-mentioned problems encountered
`with the conventional apparatuses.
`An object of the invention is to provide a novel and
`improved distance detecting apparatus for a vehicle in
`which the driver is able to readily and exactly recognize
`the location and direction of each object present within
`the wide ?eld of view of the driver, and at the same time
`determine whether each of the objects is an obstacle to
`the travel of his or her vehicle as well.
`Another object of the invention is provide a novel
`and improved distance detecting apparatus for a vehicle
`which is able to concurrently detect the distances to a
`plurality of objects which exist within the ?eld of view
`of the driver, and in which the driver is able to readily
`and accurately recognize to which objects the distances
`are detected.
`A further object of the invention is to provide a novel
`and improved distance detecting apparatus for a vehicle
`which is able to sense a preceding vehicle running
`ahead of a subject vehicle on which the apparatus is
`mounted without dazzling the passengers in the preced
`ing vehicle even when travelling in a tunnel or in dark
`weather such as in the evening, twilight and the like.
`In order to achieve the above objects, according to
`the present invention, there is provided a distance de
`tecting apparatus for a vehicle comprising: a pair of ?rst
`and second image sensors including a pair of optical
`systems for optically sensing a plurality of objects; a
`?rst memory for storing the images of the objects
`sensed by the ?rst image sensor as ?rst image signals; a
`second memory for storing the images of the objects
`sensed by the second image sensor as second image
`signals; a display with a screen for displaying the images
`of the objects as sensed by the image sensors on the
`screen; window de?ning means for de?ning a plurality
`of windows at speci?c locations on the screen of the
`display; distance calculating means for electrically de
`tecting deviations between the images of the objects
`within the respective windows as sensed by the image
`sensors and individually calculating the distance to each
`object in each window based on the calculated devia
`
`where d is a shift distance by which the image signals
`are moved to obtain the best match.
`In addition, Japanese Patent Publication No.
`63-l8l22 discloses an obstacle detecting apparatus for a
`vehicle which is provided with a plurality of light emit
`ting elements or light transmitters each projecting a
`beam of light toward objects to be detected for the
`purpose of improving the contrast of the image of an
`object sensed by the image sensors in the event that no
`good image contrast is obtained.
`With the distance and/or obstacle detecting appara
`tuses as described above, it is possible to detect the
`presence or absence of an object lying in the direction in
`which ultrasonic or electromagnetic waves or light are
`projected, but it is difficult to precisely determine
`whether the object thus detected is an obstacle to the
`travel of the vehicle. For example, when a vehicle is
`travelling on a curved road, the obstacle detecting ap
`paratus mounted thereon can misidentify a guide rail,
`which is set up along one side or shoulder of the curved
`road and lies ahead of the cornering vehicle, as an obsta
`cle. In addition, in order to exactly determine the loca
`tion and direction of the object detected with respect to
`the moving vehicle, many ultrasonic or electromagnetic
`wave transmitters and receivers are required, thus re
`sulting in a great increase in size and costs of manufac
`ture of the overall apparatus.
`
`50
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`tions; and obstacle discriminating means for discriminat
`In the ?gures, the same or corresponding parts are
`identi?ed by the same symbols.
`ing, among the objects around the vehicle as sensed by
`the image sensors, obstacles to the travel of the vehicle
`on the basis of the positions of the windows on the
`screen and the distances to the objects in the respective
`windows as detected.
`The window de?ning means de?nes the plurality of
`windows in such a manner that the windows are dis
`posed on the screen of the display in a horizontally
`separate relation with respect of each other, the win
`dows including a central window located at the center
`of the screen, and a plurality of side windows located on
`the opposite sides of the central window. The obstacle
`discriminating means determines that the image in the
`central window is the image of a preceding vehicle
`which a vehicle having the apparatus installed thereon
`follows.
`Preferably, the apparatus further comprises means for
`determining, based on the rate of change of the dis
`tances as measured by the distance calculating means,
`whether an object displayed in each window is coming
`near or going away from a vehicle on which the appara
`tus is installed.
`Preferably, a vehicle condition sensing means is pro
`vided for determining whether a subject vehicle having
`the apparatus installed thereon is travelling on a curved
`road. The obstacle discriminating means operates to
`determine that the objects displayed in the windows are
`not obstacles impeding the travel of the subject vehicle,
`if it is determined that the subject vehicle is travelling
`on a curved road and if the distances to the objects
`displayed in the windows vary in a gradually decreasing
`or increasing manner in a horizontal direction from one
`side to the other side of the windows.
`An infrared light generating means can be provided
`for projecting a beam of infrared light toward objects
`present within the ?elds of view of the image sensors
`when natural visible light is insufficient for the image
`sensors. In this case, the image sensors are sensitive to
`infrared light as well.
`The above and other objects, features and advantages
`of the invention will become more readily apparent
`from the detailed description of a few preferred embodi
`ments of the invention taken in conjunction with the
`accompanying drawings.
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a schematic block diagram showing the
`general arrangement of a distance detecting apparatus
`for a vehicle in accordance with the present invention;
`50
`FIG. 2 is an explanatory view showing a plurality of
`windows de?ned on the screen of a display;
`FIG. 3 is an explanatory view showing that a plural~
`ity of preceding vehicles running ahead of a vehicle
`come into some of the windows;
`FIGS. 4(a) and 4(b) are explanatory views showing
`image areas to be compared with reference images each
`within a corresponding window;
`FIG. 5 is an explanatory view showing images dis
`played on the screen when the vehicle is travelling on a
`curved road;
`FIG. 6 is a view showing that the positions of win
`dows on the screen are altered;
`FIG. 7 is a view similar to FIG. 1, but showing an
`other embodiment of the invention; and
`FIG. 8 is a block diagram showing the general ar
`rangement of a conventional distance detecting appara
`tus for a vehicle.
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`A few preferred embodiments of the present inven
`tion will now be described in detail with reference to
`the accompanying drawings.
`FIG. 1 illustrates, in a block diagram, the schematic
`arrangement of a distance detecting apparatus which is
`constructed in accordance with the principles of the
`invention and which is mounted on a vehicle for detect
`ing the distances to objects such as preceding vehicles,
`obstacles and the like lying ahead of the subject vehicle.
`The apparatus illustrated includes a pair of ?rst and
`second parallel optical systems having two convex
`lenses 1, 2 disposed in a vertically aligned relation at a
`prescribed distance L away from each other, and a pair
`of separate ?rst and second (e.g., upper and lower)
`image sensors 3, 4 which are vertically or otherwise
`disposed at focal points of the lenses 1, 2, respectively,
`at a distance f from the locations of the corresponding
`lenses 1, 2 for generating ?rst and second image signals
`in the form of analog signals representative of a two-di
`mensional image, which are input to a pair of corre
`sponding ?rst and second analog-to-digital (A/D) con~
`verters 6, 7. The outputs of the A/D converters 6, 7 are
`input to a pair of corresponding ?rst and second memo
`ries 8, 9 and stored therein. A microcomputer 10, which
`acts as a distance calculating means and an obstacle
`discriminating means of the invention, performs data
`transfer with the memories 8, 9 so that it makes various
`calculations and determinations based on the data
`stored in the memories 8, 9. A display 11 having a
`screen is connected to the ?rst and second memories 8, .
`9 and the microcomputer 10 for displaying the images
`of objects sensed by the ?rst or second image sensor 3,
`4 on the screen. The operation of the display 11 is con
`trolled by the microcomputer 10. A window de?ning
`means 12 is connected to the microcomputer 10 for
`de?ning on the screen of the display 11 a plurality of
`windows which can be utilized for designating a plural
`ity of objects for distance measurements. More speci?
`cally, as shown in FIG. 2, the driver of a vehicle can
`manipulate the window de?ning means 12 to de?ne a
`plurality (e.g., ?ve in the illustrated embodiment) of
`windows 15 through 19 on the screen of the display 11
`at horizontally spaced or separate predetermined loca
`tions thereof while looking at the screen. A vehicle
`condition sensing means 13 in the form of a steering
`angle sensor senses the amount or angle of steering
`representative of the rotational angle of a steering
`wheel of the vehicle and generates a corresponding
`steering angle signal to the microcomputer 10. An alarm
`14 in the form of a buzzer is actuated by the microcom
`puter 10 to generate a warning when the distance to an
`object 5 such as a preceding vehicle decreases to a
`predetermined level.
`The operation of the above embodiment will be de
`scribed below while referring to FIGS. 2, 3 and 4(0) and
`4(b). First, assume that an object in the form of a pre~
`ceding vehicle 5 lying ahead of the subject vehicle is
`sensed by the second or upper image sensor 4, digitized
`by the second A/D converter 7, stored in the second
`memory 9, and then displayed on the screen of the
`display 11, as shown in FIG. 3. In this case, the mi
`crocomputer 10 reads out from the second memory 9
`picture element signals within the central window 17
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`whereby the distances to the respective objects can
`that catches the preceding vehicle 5, and takes them as
`substantially concurrently be measured using the indi
`reference image signals, which are used as a basis for
`calculating the distance to the preceding vehicle 5.
`vidual windows 15 through 19.
`_
`Then, the microcomputer 10 selects a speci?c area cor
`Further, if it is detected from the output signal of the
`responding to the window 17 from the ?rst memory 8,
`steering angle sensor 13 that the subject vehicle is run
`which stores image signals of objects sensed by the ?rst
`ning straight, it is determined that the vehicle displayed
`or lower image sensor 3. Then, the microcomputer 10
`on the screen 11 in the center thereof is a preceding
`calculates a total sum of the absolute values of the dif
`vehicle travelling on the same lane of a road as that on
`ferences or deviations between the corresponding
`which the subject vehicle is travelling. Accordingly, if
`image signals for the ?rst and second picture elements
`the distance from the subject vehicle to the preceding
`stored in the ?rst and second memories 8, 9 while verti
`vehicle becomes short or decreases to a predetermined
`cally shifting the image signals from the ?rst memory 8
`level, the microcomputer 10 actuates the alarm 14,
`relative to the above de?ned reference image signals in
`warning the driver of the presence of an obstacle in the
`a stepwise manner one picture element by one picture
`form of the preceding vehicle lying ahead of the subject
`element. In other words, by sequentially shifting the
`second memory image signals one picture element by
`one picture element, the best position of the image of
`the object in the ?rst memory 8 is determined in which
`the image in the ?rst memory 8 best matches the refer
`ence image. Thus, the amount of shift or shift distance
`of the second memory image 5a relative to the reference
`image is calculated which minimizes the total sum of the
`absolute values of the deviations.
`In this connection, it is to be noted that the area in the
`?rst memory 8 relating to the above calculation is a
`vertically extending band area 22, as shown in FIG.
`4(b), which corresponds to the position of the window
`17 in which the reference image exists, as shown in FIG.
`4(a).
`Using the amount of shift it in terms of the number of
`picture elements as calculated above, the distance R to
`the preceding vehicle 5 is calculated as follows:
`
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`vehicle.
`-
`On the other hand, when the subject vehicle is travel
`ling on a curved road 26, e.g., a left-hand curve, the
`image of a guide rail 27, which lies ahead of the vehicle
`and is set up on one side or shoulder of the road 26, is
`displayed on the screen 11. In this case, too, the dis
`tances to the respective portions of the guide rail 27
`caught in the respective windows 15 through 19 are
`detected or measured in the same manner as in the case
`of the preceding vehicle. On this occasion, the distances
`as detected by the right-side windows 18, 19 lying to the
`right of the central window 17 in the center of the
`screen 11 are shorter than that detected by the central
`window 17, whereas the distances as detected by the
`left-side windows 15, 16 are longer than that detected
`by the central window 17. Accordingly, if such infor
`mation is obtained during the time when the steering
`angle sensor 13 senses a left-hand steering operation of
`the driver, the microcomputer 10 determines that an
`object caught in the central window 17 on the screen 11
`is not an obstacle impeding the travel of the vehicle. As
`a result, even if the distance detected by the central
`window 17 is short, it is determined that there is no
`problem, and hence the alarm 14 is not actuated. In this
`manner, on the basis of the information on the distances
`to objects ahead of the subject vehicle as detected by
`the respective windows 15 through 19, it can be pre
`cisely determined whether the objects as detected and
`displayed by the respective windows 15 through 19 are
`true obstacles to the travel of the subject vehicle.
`Although in the above embodiment, ?ve windows 15
`through 19 are set on the screen, the number of such
`windows can be arbitrarily selected depending on the
`dimensions of objects within the ?elds of view of the
`image sensors 3, 4, the number of objects to which
`distance measurements are required, etc. Also, the size
`and con?guration of each window can be arbitrarily
`changed according to an object to be detected. In addi
`tion, the positions of windows as set on the screen 11
`can be varied according to ranges or ?elds to be de
`tected, as shown in FIG. 6. Moreover, the present in
`vention can be applied for detecting or supervising
`objects present in the rear vision of a vehicle. Further,
`according to the invention, it is possible to calculate the
`rate of change of the distance to an object caught by
`each of the windows 15 through 19 so as to determine
`whether or not the object is coming near or going away
`from the subject vehicle.
`In addition, although in the above embodiment, the
`lenses 1, 2 and the image sensors 3, 4 are disposed in a
`vertically aligned and spaced relationship with respect
`to each other, they may be disposed in a modi?ed man
`ner, e.g., diagonally on a vertical plane, such that they
`
`(t)
`R=(/><L)/nP
`where f is the focal distance of the ?rst and second
`lenses 1, 2; L is the distance between the centers of the
`?rst and second lenses 1, 2; n is the amount of shift
`represented by the number of picture elements for mini
`mizing the total sum of the absolute values of the devia
`tions between the ?rst and second picture elements in
`the ?rst and second memories 8, 9; and P is the vertical
`pitch between adjacent picture elements in a vertical
`array.
`In this manner, the distance R to the object 5 imaged
`in the window 17 can be measured. Likewise, if another
`vehicle 25 running on an adjacent lane of the road ahead
`of the subject vehicle comes into the ?elds of view of
`the image sensors 3, 4 and is displayed on the screen of
`the display 11 inside the window 19, as illustrated in
`FIG. 3, the microcomputer 10 takes the image signals
`inside a window 19 as reference picture signals as
`shown in FIG. 4(a), selects an image area 24 in the ?rst
`memory 8 corresponding to the image signals of the
`second memory 9 inside the window 19, and determines
`the position of the image of the vehicle 25 in the ?rst
`memory 8 which provides the best match with the
`image inside the window 19. Then, using equation (1)
`above, the distance to the other vehicle 25 is calculated
`in the same manner.
`In this manner, even in cases where there are a plural
`ity of preceding vehicles running ahead of the subject
`vehicle, it is possible to concurrently detect the dis
`tances to the respective preceding vehicles.
`As can be seen from the foregoing, the objects caught
`in the plurality of windows 15 through 19 de?ned on
`the screen of the display 11, as shown in FIG. 4(a), are
`compared with the images thereof in the calculation
`areas of the memory 8 corresponding to the windows 20
`through 24, respectively, as shown in FIG. 4(b),
`
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`components does not cause any dazzling or blinding of
`are disposed substantially vertically. Obviously, such a
`the driver or passengers in the preceding vehicle 5, so
`modi?ed arrangement provides substantially the same
`the driver in the preceding vehicle can maneuver his or
`results.
`.her vehicle without any resultant trouble or inconve
`FIG. 7 shows another embodiment of the invention.
`This embodiment is substantially similar to the previous
`nience.
`Although in the above description, the infrared light
`embodiment of FIG. 1 except for the following. An
`generating means comprises a combination of the light
`infrared light generating means is provided for project
`generator 30 and the infrared light ?lter 31, it is not
`ing a beam of infrared light to objects for detecting
`limited to such an arrangement but may take any other
`them in dark weather in which there is insufficient natu
`appropriate form which can generate a beam of infrared
`ral visible light. The infrared light generating means
`light while excluding almost all of the visible light com
`comprises a light generator 30 in the form of a halogen
`ponents.
`lamp for generating a beam of light including visible
`What is claimed is:
`light components and infrared light components, and an
`1. A vehicle mounted distance detecting apparatus,
`infrared light ?lter 31 for ?ltering or removing almost
`comprising:
`all of the visible light components from the light gener
`a) a pair of laterally spaced ?rst and second image
`ated by the light generator while passing infrared light
`sensors (3,4; 3'4’) including a pair of optical systems
`components alone. The infrared light beam projected
`(1, 2) for optically sensing a plurality of objects;
`from the light generator 30 through the ?lter 31 to an
`b) a ?rst memory for storing the images of said ob
`object 5 is reflected from a surface thereof and received
`jects sensed by said ?rst image sensor as ?rst image
`by a pair of ?rst and second image sensors 3', 4' through
`signals;
`respective lenses 1, 2. The image sensors 3’, 4’ are sensi
`0) a second memory for storing the images of said
`tive to infrared light as well as visible light. Like the
`objects sensed by said second image sensor as sec
`previous embodiment, the images of the object 5 thus
`ond image signals;
`sensed by the image sensors 3’, 4’ are stored in corre
`(1) a display (11) with a screen for displaying the
`sponding memories 8, 9 and then processed by a mi
`images of said objects as sensed by said image sen
`crocomputer 10 in the same manner as in the previous
`embodiment. The image of the object 5 sensed by the
`sors on the screen;
`e) window de?ning means (12) for de?ning a plurality
`second image sensor 4' is displayed on the screen of a
`of windows (15-19) at speci?c locations on the
`display 11 within a plurality of windows which are
`screen of said display;
`appropriately set thereon in advance. In this connec
`f) distance calculating means for electrically detect
`tion, the light generator 30 projects a light beam toward
`ing deviations between the images of said objects
`the object 5 with an angle of projection B which is set
`within the respective windows as sensed by said
`to be less than the angle of ?eld A of the image sensors
`image sensors and individually calculating the dis
`3’, 4' through the lenses 1, 2, as shown in FIG. 7, such
`tance to each object in each window based on the
`that the infrared light re?ected from the object 5 can be
`received by the image sensors 3’, 4’. More speci?cally,
`calculated deviations; and
`g) obstacle discriminating means for discriminating,
`the light beam is projected to those areas of objects
`among the objects around the vehicle as sensed by
`which can be sensed by the image sensors 3’, 4’ and
`said image sensors, obstacles to the travel of the
`displayed within the plurality of windows preset on the
`vehicle on the basis of the positions of the windows
`screen 11.
`on the screen and the calculated distances to the
`In this embodiment, the steering angle sensor 13 and
`objects in said respective windows.
`the alarm 14 as employed with the previous embodi
`2. A distance detecting apparatus according to claim
`ment of FIG. 1 are omitted but may be provided as
`1, wherein said window de?ning means de?nes the
`necessary.
`plurality of windows in such a manner that the windows
`The operation of the second embodiment is substan
`are disposed on the screen of said display in a horizon
`tially similar to that of the ?rst embodiment in cases
`tally separate relation with respect to each other, said
`where suf?cient natural light is available such as during
`windows including a central window (17) is located at
`day time. In dark weather such as in the evening, twi
`light and the like in which natural light is limited and
`the center of the screen, and a plurality of side windows
`(15, 16, 18, 19) located on the opposite sides of said
`insufficient for the image sensors, however, the light
`central window; and
`generator 31 is energized to generate a beam of light
`said obstacle discriminating means determines that
`which is ?ltered by the infrared light ?lter 31 so that
`the image in the central window is the image of a
`infrared light components alone are passed onto an
`preceding vehicle which a vehicle having the dis
`object 5 such as a preceding vehicle. The infrared light
`tance detecting apparatus installed thereon follows.
`re?ected from a surface of the object 5 is sensed by the
`3. A distance detecting apparatus according to claim
`?rst and second image sensors 3', 4'. The images of the
`1, further comprising means for determining, based on
`‘ object 5 thus sensed are converted by the A/D convert
`the rate of change of the distances as measured by said
`ers 6, 7 from analog into digital form and stored in the
`distance calculating means, whether an object displayed
`?rst and second memories 8, 9. The microcomputer 10
`fetches picture element signals from the memories 8, 9
`in each window is coming nearer to or going away from
`and processes them and displays the image of the object
`a vehicle on which the distance detecting apparatus is
`installed.
`5 as sensed by the second image sensor 4’ on the screen
`4. A distance detecting apparatus according to claim
`of the display 11 in the same manner as in the previous
`1, further comprising vehicle condition sensing means
`embodiment. Thus, according to this embodiment, the
`(13) for sensing whether a subject vehicle having the
`objects present in the dark can be detected and the
`distance detecting apparatus installed thereon is travel
`distances thereto can be precisely measured in the same
`manner as in bright weather. In this regard, the projec
`ling on a curved road, and wherein said obstacle dis
`criminating means is operable to determine that objects
`tion of infrared light including little or no visible light
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`for projecting a beam of infrared light toward objects
`displayed in the windows are not obstacles impeding
`the travel of the subject vehicle, if it is determined that
`present within the ?elds of view of said image sensors
`when natural visible light is insufficient for said image
`the subject vehicle is travelling on a curved road and if
`the distances to the object displayed in the windows
`sensors, and wherein said image sensors are sensitive to
`infrared light.
`vary in a gradually decreasing or increasing manner in
`7. A distance detecting apparatus according to claim
`a horizontal direction from one side to the other side of
`the windows.
`6, wherein said infrared light generating means com
`prises:
`5. A distance detecting apparatus according to claim
`a lig