United States Patent [19J
`Asayama
`
`[54] DISTANCE DETECTING APPARATUS FOR A
`VEHICLE
`
`Inventor: Yoshiaki Asayama, Himeji, Japan
`[75]
`(73] Assignee: Mitsubishi Denki Kabushiki Kaisha,
`Tokyo, Japan
`
`[21] Appl. No.: 782,110
`[22] Filed:
`Oct. 24, 1991
`[30]
`Foreign Application Priority Data
`Oct. 25, 1990 [JP]
`Japan .................................. 2-290469
`Nov. 28, 1990 [JP]
`Japan .................................. 2-335430
`[51]
`Int. Cl.s .......................... B60Q 1/00; GOSG 1/16
`(52] u.s. 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 eta!. ....................... 358/93
`4,779,095 10/1988 Guerreri .............................. 340/904
`4,908,704 3/1990 Fujioka eta!. ...................... 358/108
`· 5,026,153 6/1991 Suzuki eta!. ....................... 340/903
`
`FOREIGN PATENT DOCUMENTS
`55-15337 4/1980 Japan .
`
`lllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll
`5,214,408
`May 25, 1993
`
`US005214408A
`[11] Patent Number:
`[45] Date of Patent:
`
`57-49841 10/1982 Japan .
`63-18122 4/1988 Japan .
`63-38085 7/1988 Japan .
`63-64363 12/1988 Japan .
`1-12221 4/1989 Japan .
`
`Primary Examiner-Donnie L. Crosland
`Attorney, Agent, or Firm-Sughrue, Mion, Zinn,
`Macpeak and Seas
`
`ABSTRACf
`[57]
`A distance detecting apparatus enables the driver of a
`vehicle to readily and concurrently recognize the loca(cid:173)
`tion and direction of each of a plurality of objects pres(cid:173)
`ent in the driver's field 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 first and second image sensors 3, 4
`are displayed on a screen 11 in a plurality of windows
`15-19. 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(cid:173)
`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(cid:173)
`dows as detected. Infrared light can be projected onto
`objects present within the fields of view of the image
`sensors when natural visible light is insufficient for the
`image sensors which, in this case, are sensitive to infra(cid:173)
`red light.
`
`8 Claims, 6 Drawing Sheets
`
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`U.S. Patent
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`May 25, 1993
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`U.S. Patent
`
`May 25, 1993
`
`Sheet 3 of 6
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`5,214,408
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`U.S. Patent
`
`May 25, 1993
`
`Sheet 4 of 6
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`5,214,408
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`FIG.5
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`U.S. Patent
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`May 25, 1993
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`U.S. Patent
`
`May 25, 1993
`
`Sheet 6 of 6
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`5,214,408
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`FIG.8
`PRIOR ART
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`1
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`5,214,408
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`DISTANCE DETECTING APPARATUS FOR A
`VEHICLE
`
`2
`Moreover, if there are many objects within the field
`of view of the image sensors, it is unclear to which
`object the distance from the subject vehicle is being
`detected. In particular, Jet us assume that the distance to
`5 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 field 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 insufficient 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(cid:173)
`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 difficult for the driver to
`properly maneuver his or her vehicle in a safe manner.
`
`BACKGROUND OF THE INVENTION
`The present invention relates to an apparatus for
`optically measuring the distance from a vehicle to ob(cid:173)
`jects such as obstacles lying ahead thereof as well as
`other vehicles which are travelling ahead of the vehicle 10
`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 1-12221. These ap(cid:173)
`paratuses project ultrasonic waves or electromagnetic 15
`waves in a specified forward or backward direction to
`be detected and receive reflected 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 first and second parallel optical systems 25
`having two convex lenses 101, 102 disposed in a hori(cid:173)
`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 30
`corresponding lenses 101, 102, respectively, for generat(cid:173)
`ing respective image signals to a common signal proces(cid:173)
`sor 120. The signal processor 120 successively shifts the
`image signals from the image sensors 103, 104 and elec(cid:173)
`trically superposes them one over the other, so that the 35
`distance R from the lenses 101, 102 to an object 121 is
`calculated based on the principle of triangulation using
`the following formula:
`
`20
`
`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 field 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
`40 plurality of objects which exist within the field 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 ofthe 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(cid:173)
`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(cid:173)
`tecting apparatus for a vehicle comprising: a pair offrrst
`and second image sensors including a pair of optical
`systems for optically sensing a plurality of objects; a
`first memory for storing the images of the objects
`sensed by the frrst image sensor as first 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 defining means for defining a plurality
`of windows at specific locations on the screen of the
`display; distance calculating means for electrically de(cid:173)
`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-
`
`R=(fxL)!d
`
`where d is a shift distance by which the image signals
`are moved to obtain the best match.
`In addition,
`Japanese Patent Publication No.
`63-18122 discloses an obstacle detecting apparatus for a 45
`vehicle which is provided with a plurality of light emit(cid:173)
`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 so
`good image contrast is obtained.
`With the distance and/or obstacle detecting appara(cid:173)
`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 55
`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(cid:173)
`paratus mounted thereon can misidentify a guide rail, 60
`which is set up along one side or shoulder of the curved
`road and lies ahead of the cornering vehicle, as an obsta(cid:173)
`cle. In addition, in order to exactly determine the loca(cid:173)
`tion and direction of the object detected with respect to
`the moving vehicle, many ultrasonic or electromagnetic 65
`wave transmitters and receivers are required, thus re(cid:173)
`sulting in a great increase in size and costs of manufac(cid:173)
`ture of the overall apparatus.
`
`8
`
`

`

`5,214,408
`
`4
`In the figures, the same or corresponding parts are
`identified by the same symbols.
`
`3
`tions; and obstacle discriminating means for discriminat(cid:173)
`ing, among the objects around the vehicle as sensed by
`the image sensors, obstacles to the travel of the vehicle
`DESCRIPTION OF THE PREFERRED
`on the basis of the positions of the windows on the
`EMBODIMENTS
`screen and the distances to the objects in the respective 5
`A few preferred embodiments of the present inven-
`windows as detected.
`tion will now be described in detail with reference to
`The window defining means defines the plurality of
`windows in such a manner that the windows are dis-
`the accompanying drawings.
`posed on the screen of the display in a horizontally
`FIG. 1 illustrates, in a block diagram, the schematic
`separate relation with respect of each other, the win- 10 arrangement of a distance detecting apparatus which is
`dows including a central window located at the center
`constructed in accordance with the principles of the
`of the screen, and a plurality of side windows located on
`invention and which is mounted on a vehicle for detect-
`the opposite sides of the central window. The obstacle
`ing the distances to objects such as preceding vehicles,
`obstacles and the like lying ahead of the subject vehicle.
`discriminating means determines that the image in the
`central window is the image of a preceding vehicle 15
`The apparatus illustrated includes a pair of first and
`which a vehicle having the apparatus installed thereon
`second parallel optical systems having two convex
`follows.
`lenses 1, 2 disposed in a vertically aligned relation at a
`Preferably, the apparatus further comprises means for
`prescribed distance L away from each other, and a pair
`determining, based on the rate of change of the dis-
`of separate first and second (e.g., upper and lower)
`tances as measured by the distance calculating means, 20 image sensors 3, 4 which are vertically or otherwise
`disposed at focal points of the lenses 1, 2, respectively,
`whether an object displayed in each window is coming
`near or going away from a vehicle on which the appara-
`at a distance f from the locations of the corresponding
`tus is installed.
`lenses 1, 2 for generating first and second image signals
`Preferably, a vehicle condition sensing means is pro-
`in the form of analog signals representative of a two-di-
`vided for determining whether a subject vehicle having 25 mensional image, which are input to a pair of corre-
`the apparatus installed thereon is travelling on a curved
`sponding first and second analog-to-digital (A/D) con-
`verters 6, 7. The outputs of the AID converters 6, 7 are
`road. The obstacle discriminating means operates to
`determine that the objects displayed in the windows are
`input to a pair of corresponding first and second memo-
`not obstacles impeding the travel of the subject vehicle,
`ries 8, 9 and stored therein. A microcomputer 10, which
`if it is determined that the subject vehicle is travelling 30 acts as a distance calculating means and an obstacle
`discriminating means of the invention, performs data
`on a curved road and if the distances to the objects
`displayed in the windows vary in a gradually decreasing
`transfer with the memories 8, 9 so that it makes various
`or increasing manner in a horizontal direction from one
`calculations and determinations based on the data
`side to the other side of the windows.
`stored in the memories 8, 9. A display 11 having a
`An infrared light generating means can be provided 35 screen is connected to the first and second memories 8, .
`9 and the microcomputer 10 for displaying the images
`for projecting a beam of infrared light toward objects
`present within the fields of view of the image sensors
`of objects sensed by the first or second image sensor 3,
`when natural visible light is insufficient for the image
`4 on the screen. The operation of the display 11 is con-
`sensors. In this case, the image sensors are sensitive to
`trolled by the microcomputer 10. A window defining
`infrared light as well.
`40 means 12 is connected to the microcomputer 10 for
`defining on the screen of the display 11 a plurality of
`The above and other objects, features and advantages
`of the invention will become more readily apparent
`windows which can be utilized for designating a plural-
`from the detailed description of a few preferred embodi-
`ity of objects for distance measurements. More specifi-
`ments of the invention taken in conjunction with the
`cally, as shown in FIG. 2, the driver of a vehicle can
`accompanying drawings.
`45 manipulate the window defining means 12 to define a
`plurality (e.g., five 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
`55 14 in the form of a buzzer is actuated by the microcom(cid:173)
`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(cid:173)
`scribed below while referring to FIGS. 2, 3 and 4(a) and
`4(b). First, assume that an object in the form of a pre(cid:173)
`ceding vehicle 5 lying ahead of the subject vehicle is
`sensed by the second or upper image sensor 4, digitized
`by the second AID 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
`
`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 defined 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(cid:173)
`played on the screen when the vehicle is travelling on a 60
`curved road;
`FIG. 6 is a view showing that the positions of win(cid:173)
`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(cid:173)
`rangement of a conventional distance detecting appara(cid:173)
`tus for a vehicle.
`
`65
`
`9
`
`

`

`5
`that catches the preceding vehicle S, and takes them as
`reference image signals, which are used as a basis for
`calculating the distance to the preceding vehicle S.
`Then, the microcomputer 10 selects a specific area cor(cid:173)
`responding to the window 17 from the first memory 8, 5
`which stores image signals of objects sensed by the first
`or lower image sensor 3. Then, the microcomputer 10
`calculates a total sum of the absolute values of the dif(cid:173)
`ferences or deviations between the corresponding
`image signals for the first and second picture elements
`stored in the first and second memories 8, 9 while verti(cid:173)
`cally shifting the image signals from the first memory 8
`relative to the above defined reference image signals in
`a stepwise manner one picture element by one picture
`element. In other words, by sequentially shifting the 15
`second memory image signals one picture element by
`one picture element, the best position of the image of
`the object in the first memory 8 is determined in which
`the image in the first memory 8 best matches the refer(cid:173)
`ence image. Thus, the amount of shift or shift distance 20
`of the second memory image Sa 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
`first memory 8 relating to the above calculation is a 25
`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 n in terms of the number of 30
`picture elements as calculated above, the distance R to
`the preceding vehicle 5 is calculated as follows:
`
`R=(fxL)!nP
`(I)
`where f is the focal distance of the first and second
`lenses 1, 2; L is the distance between the centers of the
`first and second lenses 1, 2; n is the amount of shift
`represented by the number of picture elements for mini(cid:173)
`mizing the total sum of the absolute values of the devia(cid:173)
`tions between the first and second picture elements in
`the first and second memories 8, 9; and P is the vertical 40
`pitch between adjacent picture elements in a vertical
`array.
`In this manner, the distance R to the objectS imaged
`in the window 17 can be measured. Likewise, if another
`vehicle 25 running on an adjacent lane of the road ahead 45
`of the subject vehicle comes into the fields 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 first
`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 first
`memory 8 which provides the best match with the 55
`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 60
`vehicle, it is possible to concurrently detect the dis(cid:173)
`tances to the respective preceding vehicles.
`As can be seen from the foregoing, the objects caught
`in the plurality of windows 15 through 19 defined on
`the screen of the display 11, as shown in FIG. 4(a), are 65
`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),
`
`5,214,408
`
`6
`whereby the distances to the respective objects can
`substantially concurrently be measured using the indi(cid:173)
`vidual windows 15 through 19.
`Further, if it is detected from the output signal of the
`steering angle sensor 13 that the subject vehicle is run(cid:173)
`ning straight, it is determined that the vehicle displayed
`on the screen 11 in the center thereof is a preceding
`vehicle travelling on the same lane of a road as that on
`which the subject vehicle is travelling. Accordingly, if
`10 the distance from the subject vehicle to the preceding
`vehicle becomes short or decreases to a predetermined
`level, the microcomputer 10 actuates the alarm 14,
`warning the driver of the presence of an obstacle in the
`form of the preceding vehicle lying ahead of the subject
`vehicle.
`On the other hand, when the subject vehicle is travel(cid:173)
`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(cid:173)
`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, 19lying 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
`35 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(cid:173)
`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, five 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 fields of view of the
`50 image sensors 3, 4, the number of objects to which
`distance measurements are required, etc. Also, the size
`and configuration 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 fields to be de(cid:173)
`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 disiance 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 modified man(cid:173)
`ner, e.g., diagonally on a vertical plane, such that they
`
`10
`
`

`

`5,214,408
`
`8
`7
`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
`modified !lrrangement 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 5 nience.
`Although in the above description, the infrared light
`embodiment of FIG. 1 except for the following. An
`infrared light generating means is provided for project-
`generating means comprises a combination of the light
`ing a beam of infrared light to objects for detecting
`generator 30 and the infrared light filter 31, it is not
`them in dark weather in which there is insufficient natu-
`limited to such an arrangement but may take any other
`ral visible light. The infrared light generating means 10 appropriate form which can generate a beam of infrared
`comprises a light generator 30 in the form of a halogen
`light while excluding almost all of the visible light com-
`lamp for generating a beam of light including visible
`ponents.
`light components and infrared light components, and an
`What is claimed is:
`infrared light filter 31 for filtering or removing almost
`1. A vehicle mounted distance detecting apparatus,
`all of the visible light components from the light gener- 15 comprising:
`ated by the light generator while passing infrared light
`a) a pair of laterally spaced first and second image
`components alone. The infrared light beam projected
`sensors (3,4; 3'4') including a pair of optical systems
`from the light generator 30 through the filter 31 to an
`(1, 2) for optically sensing a plurality of objects;
`object 5 is reflected from a surface thereof and received
`b) a first memory for storing the images of said ob-
`by a pair of first and second image sensors 3', 4' through 20
`jects sensed by said first image sensor as first image
`respective lenses 1, 2. The image sensors 3', 4' are sensi-
`signals;
`tive to infrared light as well as visible light. Like the
`c) a second memory for storing the images of said
`previous embodiment, the images of the object 5 thus
`objects sensed by said second image sensor as sec-
`sensed by the image sensors 3', 4' are stored in corre-
`ond image signals;
`sponding memories 8, 9 and then processed by a mi- 25
`d) a display (11) with a screen for displaying the
`crocomputer 10 in the same manner as in the previous
`images of said objects as sensed by said image sen-
`embodiment. The image of the object 5 sensed by the
`sors on the screen;
`second image sensor 4' is displayed on the screen of a
`e) window defining means (12) for defining a plurality
`display 11 within a plurality of windows which are
`of windows (15-19) at specific locations on the
`appropriately set thereon in advance. In this connec- 30
`screen of said display;
`tion, the light generator 30 projects a light beam toward
`f) distance calculating means for electrically detect-
`the object 5 with an angle of projection B which is set
`ing deviations between the images of said objects
`to be less than the angle of field A of the image sensors
`within the respective windows as sensed by said
`3', 4' through the lenses 1, 2, as shown in FIG. 7, such
`image sensors and individually calculating the dis-
`tance to each object in each window based on the
`that the infrared light reflected from the object 5 can be 35
`received by the image sensors 3', 4'. More specifically,
`calculated deviations; and
`the light beam is projected to those areas of objects
`g) obstacle discriminating means for discriminating,
`which can be sensed by the image sensors 3', 4' and
`among the objects around the vehicle as sensed by
`displayed within the plurality of windows preset on the
`said image sensors, obstacles to the travel of the
`screen 11.
`vehicle on the basis of the positions of the windows
`In this embodiment, the steering angle sensor 13 and
`on the screen and the calculated distances to the
`the alarm 14 as employed with the previous embodi-
`objects in said respective windows.
`ment of FIG. 1 are omitted but may be provided as
`2. A distance detecting apparatus according to claim
`necessary.
`1, wherein said window defining means defines the
`The operation of the second embodiment is substan- 45 plurality of windows in such a manner that the windows
`tially similar to that of the first embodiment in cases
`are disposed on the screen of said display in a horizon-
`where sufficient natural light is available such as during
`tally separate relation with respect to each other, said
`day time. In dark weather such as in the evening, twi-
`windows including a central window (17) is located at
`light and the like in which natural light is limited and
`the center of the screen, and a plurality of side windows
`insufficient for the image sensors, however, the light 50 (15, 16, 18, 19) located on the opposite sides of said
`generator 31 is energized to generate a beam of light
`central window; and
`which is filtered by the infrared light filter 31 so that
`said obstacle discriminating means determines that
`infrared light components alone are passed onto an
`the image in the central window is the image of a
`object 5 such as a preceding vehicle. The infrared light
`preceding vehicle which a vehicle having the dis-
`reflected from a surface of the object S is sensed by the 55
`tance detecting apparatus installed thereon follows.
`first and second image sensors 3', 4'. The images of the
`3. A distance detecting apparatus according to claim
`· object S thus sensed are converted by the AID convert-
`1, further comprising means for determining, based on
`ers 6, 7 from analog into digital form and stored in the
`the rate of change of the distances as measured by said
`first and second memories 8, 9. The microcomputer 10
`distance calculating means, whether an object displayed
`fetches picture element signals from the memories 8, 9 60 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
`S as sensed by the second image sensor 4' on the screen
`installed.
`of the display 11 in the same manner as in the previous
`4. A distance detecting apparatus according to claim
`embodiment. Thus, according to this embodiment, the
`1, further comprising vehicle condition sensing means
`objects present in the dark can be detected and the 65 (13) for sensing whether a subject vehicle having the
`distances thereto can be precisely measured in the same
`distance detecting apparatus installed thereon is travel-
`manner as in bright weather. In this regard, the projec-
`ling on a curved road, and wherein said obstacle dis-
`tion of infrared light including little or no visible light
`criminating means is operable to determine that objects
`
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`11
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`9
`displayed in the windows are not obstacles impeding
`the travel of the subject vehicle, if it is determined that
`the subj