Abstract:
An obstacle detecting system comprises an optical unit having a plurality of spaced laser diodes each of which emits a laser beam, a convex lens spaced from the optical unit in the frontward direction thereof and establishing a combined beam after each the laser beam passes through the convex lens, and a driving device for adjusting the relationship between each the laser beam and the convex lens. Such structure enabling the detection of the obstacle such as a vehicle in such manner that the obstacle is fallen within the width of the combined beam by adjusting the relationship between each the laser beam and the convex lens.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an obstacle detecting system, and in particular to an obstacle detecting system which is mounted on a vehicle for detecting an obstacle at a frontward direction thereof by using a radar principle. 
     Conventional obstacle detecting systems of the type are disclosed in Japanese Patent Laid-open Print No. Hei 1-114550 published in May 8, 1989, and Japanese Patent Laid-open Print No. Hei 2-216080 published in Aug. 28, 1990. In each of the conventional systems, a radio wave of an ultrahigh frequency is emitted from a following vehicle to a preceeding vehicle as an obstacle. If the wave is found to be the reflection from the preceeding vehicle, the resulting recognition is used for controlling the inter-vehicle distance. 
     However, in each of the conventional systems, since the beam of the radio wave is narrow in width or the lateral length direction of the vehicle, if the preceeding vehicle is moved in a direction which is substantially perpendicular to the cruising direction of the following vehicle, the chasing of the preceeding vehicle may be in malfunction. 
     SUMMARY OF THE INVENTION 
     It is, therefore, a primary object of the present invention to provide an obstacle detecting system which ensures the reliable chasing of an obstacle such as a preceeding vehicle. 
     In order to attain the foregoing object, an obstacle detecting system comprises an optical unit having a plurality of spaced laser diodes each of which emits a laser beam, a convex lens spaced from the optical unit in the frontward direction thereof and establishing a combined beam after each the laser beam passes through the convex lens, and driving means for adjusting the relationship between each of the laser beams and the convex lens. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will be more apparent and more readily appreciated from the following detailed description of preferred exemplarily embodiment of the present invention, taken in connection with the accompanying drawings, in which; 
     FIG. 1 is a block diagram showing an overall structure of an obstacle detecting system according to the present invention; 
     FIG. 2 is a plane view showing a scanning manner of laser beams; 
     FIG. 3 is a plane view showing three laser beams pass a common convex lens; 
     FIGS. 4 is a flowchart showing the control of the rotating direction of a prime axis of a laser beam; 
     FIG. 5 is a view showing the relationsihip between a prime axis of a laser beam emission direction and a rotational direction of a system driven by a motor; 
     FIG. 6 is an illustration showing a mechanism for rotating a system unit; 
     FIG. 7 is an illustration showing another mechanism for rotating a system unit; 
     FIG. 8 is an illustration showing a third type mechanism for rotating a system unit; 
     FIG. 9 is a plane view showing another mode of a scanning manner of laser beams; and 
     FIG. 10 is a plane view showing a third mode of a scanning manner of laser beams. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will be described hereinunder in detail with reference to the accompanying drawings. 
     Referring first to FIG. 1, a block diagram of an overall structure of an obstacle detecting system 10 is shown. This obstacle system 10 has a first laser diode LD1, a second laser diode LD2, and a third laser diode LD3 which are under the control of a driving circuit 16. The laser diodes LD1, LD2, and LD3 are set to emit laser beams in turn at intervals towards an obstacle 90. Emission timing circuit 14 controls driving circuit 16 upon receipt of a signal from clock generator 12. A part of each emitted laser beams is fed via a common optical fiber 89 to a photodiode 18B, is amplified at amplifier 20B, is wave-shaped at a wave-shaper 22B, and is fed as an emission timing signal to a counter 24. The counter 24 is set to start upon receipt of the emission timing signal. The counter 24 is also fed from a clock generator 12 with a clock signal for measuring a time necessary for the emitted laser beam to go and return back. 
     A reflected laser beam or the emitted laser beam after its reflection at the obstacle 90 is set to be received at another photodiode 18A. The resulting laser beam is amplified at an amplifier 20A, is wave-shaped at a wave-shaper 22A, and is fed to the counter 24 as a receipt time signal. The counter 24 is set to be terminated upon receipt of the receipt time signal. Due to the fact that the value in the counter 24 indicates the time required for the laser beam&#39;s reflection movement, the value is fed to a distance calculator 26 so as to be converted into the corresponding distance between the vehicle and the obstacle 90, and the resulting distance is displayed at an output circuit 28 including a CRT (not shown) or an instrument (not shown). 
     The interval Δt between two successive laser beam emissions is determined on the basis of the following principle. That is to say, if the maximum measuring distance is set to be 200 m, the time taken for each laser beam to establish its reflection movement can be obtained by the calculation of (200 m×2)÷(3×10 8  m/s)=1.3 μ sec. Thus, when the interval Δt is set to be above 1.3 μ sec, an identification of each laser beam can be established at the photodiode 18A. 
     A control circuit 30 controls a motor driving circuit 32 in order to adjust the rotation of a motor M on the basis of the distance corresponding to each laser beam. In this system 10, as shown in FIG. 2, the three laser beams which constitute a combined laser beam as a whole cover a total of 3.6 m wide emission range at a 100 m distance ahead, and if the vehicle is of 1.7 m width each beam can detects the obstacle 90. If the obstacle 90 in the form of the preceeding vehicle traverses the cruising direction of the following vehicle (hereinafter referred to this vehicle) on which this system is mounted, the detected conditions of the obstacle 90 by the system 10 are summarized in the following Table 1. 
     
                       TABLE 1______________________________________Mode  LD3    LD2    LD1  Condition of the obstacle______________________________________1     X      X      X    No obstacle is detected.2     X      X      ◯                    At front-right side relative                    to this vehicle3     X      ◯               X    In alignment with this vehicle4     X      ◯               ◯                    Inclination toward front-right side5     ◯        X      X    At front-left side relative                    to this vehicle6     ◯        X      ◯                    In alignment with this vehichle7     ◯        ◯               X    Inclination toward front-left side8     ◯        ◯               ◯                    In alignment with this vehicle______________________________________ ◯ : The obstacle is detected. X : No obstacle is detected. 
    
     As shown in FIG. 6, the motor M is connected to a reducer 34A having a shaft on which a pinion 36A is fixed. The pinion 36A is in meshing engagement with an annular rack 36B which is secured to a bottom surface of a base plate 40. The base plate 40 is provided with a shaft 41 which is rotatably mounted on a portion 42 of the vehicle body. On the plate 40, there is mounted a system unit 38 which includes, as shown in FIG. 3, a plate 43 for retaining the laser diodes LD1, LD2, and LD3, and a convex lens 44 aiming at the obstacle 90. The plate 43, the laser diodes LD1-LD3 constitute an optical unit. In the system unit 38, other electric components are also accommodated. The relationship between the emission direction and the rotational direction of the system unit 38 in FIG. 5. Instead of the plate 40 and the annular rack 40, a worm wheel 45 is available as shown in FIG. 7. In addition, the system unit 38 shown in FIG. 6 can be divided into an optical division 46 and an electric division 47 as shown in FIG. 8. In the optical division 46, the laser diodes LD1, LD2, LD3, and the photodiode 18A are accommodated. In the electric division 47, other electric components are accommodated. Such structure will reduce the load of the motor M due to the fact that the mass of each member to be driven by the motor M is reduced. 
     The system 10 is set to be operated in order that the obstacle 90 is to be detected by the laser beam emitted from the second laser diode LD2 in accordance with a control based on a flowchart shown in FIG. 4. 
     First of all, at step S0, the motor M is ready for rotation. At step S1, laser beams are emitted from the laser diodes LD1, LD2, and LD3 in turn at an interval. At step S2, if the result of the operation at step S1 is deemed not to be any one of mode 3, mode 4, mode 7, and mode 8 (i.e. the laser beam emitted from the second laser diode LD2 is not received at the photodiode 18A as the reflected beam), the control is returned to step S1. If any one of mode 3, mode 4, mode 7, and mode 8 is recognized at step S2, it is checked at step S3 whether or not the locking indication signal is fed by which the motor M is remained unchanged. If positive answer is obtained at step S3, at steps S4 and S5, processings similar to those at steps S1 and S2 are performed. respectively. If negative answer is obtained at step S3, the control is returned to step S1. If the answer at step S5 is positive, the step S4 is set to be performed after execution of step S13 at which the locking signal is so generated as to show that the obstacle 90 is applied with the laser beam from the second laser diode LD2 or both of the laser beams from first and third laser diodes LD1 and LD3. When the answer at step S5 is negative, at step S6, it is checked whether the condition is mode 2 or not. If positive answer is obtained, the obstacle 90 is deemed to be at a front-right side relative to this vehicle, and at step S14 the plate 43 is rotated through an angle Δθ in one direction to chase the obstacle 90 by driving the motor M in normal direction. If negative answer is obtained at step S6, step S7 is performed whether mode 5 is detected or not. In case of positive answer, the obstacle 90 is deemed to be at a front-left side relative to this vehicle, and at step S15 the plate 43 is rotated through an angle Δθ in the other direction to chase the obstacle 90 by driving the motor M in reverse direction. In case of negative answer at step S7, the condition is found to be mode 1 wherein the obstacle 90 is deemed to be out of the beam range or not to be in existence. Thus, at step S9, the generation of the locking indication signal is terminated, and at step 8, the plate 43 is returned to its initial or original position by driving the motor M. 
     In summary, the rotation of the prime axis of the combined beam or the plate 43 in relation to each mode is shown in the following Table 2. 
     
                       TABLE 2______________________________________      Rotational direction of the primeMode       axis of the combined beam______________________________________1          Returning to its original or initial position2          Rightward direction3          Remained unchanged4          Remained unchanged5          Leftward direction6          Remained unchanged7          Remained unchanged8          Remained unchanged______________________________________ 
    
     It is to be noted that the maximum rotation angle of the prime axis of the combined beam or the plate 43 is ±θ ma4  as shown in FIG. 2. 
     As shown in FIG. 9, instead of the rotation of the plate 43, the plate 43 can be moved in the width direction of the vehicle body. Furthermore, as shown in FIG. 10, a structure is also available wherein a rotatable mirror 49 is positioned between the convex lens and the plate 43 to laser diodes LD1-LD3. 
     As mentioned above in detail, since the system 10 is provided with at least three laser diodes in the present invention, the system per se can detect the moving direction of the obstacle such as the preceeding vehicle. That is to say, at least one of the laser beams emitted from the laser diodes can be applied to the obstacle, which enables the successful or reliable chasing thereof. 
     It should be apparent to one skilled in the art that the above-described embodiments are merely illustrative of but a few of the many possible specific embodiments of the present invention. Numerous and various other arrangements can be readily devised by those skilled in the art without departing from the spirit and scope of the invention as defined in the following claims.