Abstract:
An object detecting apparatus comprises a light radiation unit and a light receiver unit disposed in an outer case. The light receiver unit includes a light collecting lens and a light receiving element. The light collecting lens is integrated with an inner case that is disposed in the outer case. The inner case is resin-molded with the light collecting lens by placing the light collecting lens in a pair of dies and injecting resin into the dies. Thus, the optical axis of the light collecting lens is fixed relative to the inner case, and hence it becomes in alignment with the optical axis of the light radiated by the radiation unit when the radiation unit is attached to the inner case.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application is based on and incorporates herein by reference Japanese Patent Application No. 2004-43182 filed on Feb. 19, 2004.  
       FIELD OF THE INVENTION  
       [0002]     The present invention relates to an object detecting apparatus mounted on a vehicle, for instance, for detecting an object such as a preceding vehicle or a distance to such an object by using a light wave and to a manufacturing method for the same.  
       BACKGROUND OF THE INVENTION  
       [0003]     A conventional object detecting apparatus mounted on a vehicle uses a laser light, for instance, to detect an object such as a preceding vehicle or a distance to such an object. This detecting apparatus intermittently drives a laser diode to radiate the laser light towards the forward side of the vehicle, and detects the light reflected from the forward obstacle by a photo sensor. The detecting apparatus measures the distance to the forward obstacle based on a time difference between a light radiation time and a light receiving time.  
         [0004]     Specifically, as disclosed in JP 2002-031685A, the detecting apparatus comprises a light radiation unit for radiating a laser light, a polygon mirror and a light receiver unit for receiving a reflected light. The polygon mirror is shaped in a frustum of a hexagonal pyramid and rotatable as a scanning mirror. According to this construction, the polygon mirror reflects the laser light radiated from the light radiation unit and directs it to the forward side of the vehicle. As the polygon mirror is rotated and the laser light from the light radiation unit is directed to each side surface of the polygon mirror, so that the angle of reflection of the laser light at the polygon mirror is adjusted to scan a predetermined range of the forward side of the vehicle by the laser light. The receiver unit includes a Fresnel lens and a light receiving element to receive the laser light reflected from the forward object and measure the distance to the object.  
         [0005]     Component parts of the object detecting apparatus are fixed to an inner case made of resin, which is accommodated in an outer case. In fixing the Fresnel lens to the inner case, optical axes of the Fresnel lens and the laser light must be adjusted so that the optical axis of the Fresnel lens coincides with the axis of radiation of the laser light in the radiation unit.  
         [0006]     As shown in  FIG. 7 , in the distance detection circuit, the Fresnel lens J 1  has four elongated holes J 3  at four corners. Each hole J 3  is elongated in the up and down directions. The inner case J 2  has two screw holes J 4  at two locations opposing diagonally and two positioning projections J 5  at two locations diagonally. The screw holes J 4  and the projections J 5  are provided in facing correspondence with the elongated holes J 3 .  
         [0007]     In the assembling process, two screws J 6  are first screwed into the screw holes J 4  through the holes J 3  while receiving the projections J 5  in the holes J 3 . Thus, the Fresnel lens J 1  is tentatively and loosely fit to the inner case J 2 . The Fresnel lens J 1  is then slid in the up and down directions so that the optical axes of the radiated light and the Fresnel lens J 1  are adjusted to each other not to deviate from other. The screws J 6  are further tightened to finally fix the Fresnel lens J 1  to the inner case J 2 .  
         [0008]     The conventional apparatus thus requires the optical axis adjustment of the Fresnel lens J 1 , resulting in an increased and complication of the assembling process.  
       SUMMARY OF THE INVENTION  
       [0009]     It is therefore an object of the present invention to provide an object detecting apparatus and a manufacturing method therefor, which simplifies the apparatus and the method.  
         [0010]     According to the present invention, an object detecting apparatus comprises a light radiation unit and a light receiver unit disposed in an outer case. The light receiver unit includes a light collecting lens and a light receiving element. The light collecting lens is integrated with an inner case that is disposed in the outer case. The inner case is resin-molded with the light collecting lens by placing the light collecting lens in a pair of dies and injecting resin into the dies. Thus, the optical axis of the light collecting lens is fixed relative to the inner case, and hence it becomes in alignment with the optical axis of the light radiated by the radiation unit when the radiation unit is attached to the inner case.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings:  
         [0012]      FIG. 1  is a perspective view of an object detecting apparatus according to an embodiment of the present invention;  
         [0013]      FIG. 2  is a sectional view of the apparatus shown in  FIG. 1 ;  
         [0014]      FIG. 3  is a top plan view of the apparatus shown in  FIG. 1 ;  
         [0015]      FIG. 4  is a perspective view of an assembly of a Fresnel lens and an inner case of the apparatus shown in  FIG. 1 ;  
         [0016]      FIG. 5  is a sectional view of the assembly along a line V-V in  FIG. 4 ;  
         [0017]      FIG. 6  is a sectional view of a manufacturing device used for assembling the Fresnel lens; and  
         [0018]      FIG. 7  is a perspective view of an assembly of a Fresnel lens and an inner case of a conventional apparatus. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0019]     Referring first to FIGS.  1  to  3 , an object detecting apparatus includes a case  1  shaped in a cuboid and various component parts accommodated in the case  1 . The apparatus is mounted on a vehicle to be used as a laser radar. The apparatus is positioned to radiate a laser light in the forward direction of the vehicle (rightward direction in  FIG. 2 ) to detect a distance to a forward object such as a preceding vehicle during an auto-cruise control condition.  
         [0020]     The apparatus includes a first outer case  1   a , a second outer case  1   b  and an inner case  1   c . The first case  1   a  is box-shaped and open at its one side (bottom side in  FIG. 2 ). The first case  1   a  accommodates therein various component parts. The first case  1   a  has a resin part  1   d  made of black PPS resin and form a housing. The first case  1   a  has a light radiating window  1   e  and a light receiving window  1   f  arranged at the left and the right sections on the front-side resin part  1   d . The windows  1   e  and  1   f  may be made of light transmitting resin such as glass and acrylic resin.  
         [0021]     The second case  1   b  is made of aluminum die-cast and threaded to the first case  1   a  through a seal member  1   g . The second case  1   b  has an electrical connector  1   h  made of resin. The connector  1   h  partly projects from the second case  1   b  to connect the electrical parts (not shown) provided inside and outside the case  1 .  
         [0022]     In the case  1 , the inner case  1   c  accommodates a light radiation unit  2 , a reflection mirror  3 , a polygon mirror  4  and an electric circuit board  5 . The circuit board  5  includes an electronic control circuit, which are connected to the light radiation unit  2 , a light receiving unit  6  and the like to measure the distance to the forward object. The light receiving unit  6  is positioned inside the case  1  to face the light receiving window  1   f  and includes a Fresnel lens and a light receiving element.  
         [0023]     The light radiation unit  2  is first connected to the inner case  1   c  and then connected to the second case  1   b . The light radiation unit  2  is driven by the control circuit provided on the circuit board  5  and radiates the laser light towards the reflection mirror  3 . The light radiation unit  2  may include a laser diode to radiate the laser light in the pulse form.  
         [0024]     The reflection mirror  3  reflects the laser light radiated from the radiation unit  3  and directs it to the polygon mirror  4 . The reflection mirror  3  is supported swingably to the inner case  1   c  by a support part  7  fixed to the inside wall of the inner case  1   c . For instance, the reflection mirror  3  may be driven by a motor (not shown) and controlled by the electric circuit of the circuit board  5  to adjust the direction of reflection.  
         [0025]     The polygon mirror  4  is shaped in a frustum hexagonal prism and supported by the inner case  1   c . The mirror  4  is rotatable about an axis of the hexagonal prism. This mirror  4  is also driven by a motor (not shown) controlled by the control circuit of the circuit board  5 . The polygon mirror  4  has around its periphery mirror faces, each of which operates as a scanning reflection mirror.  
         [0026]     Specifically, the polygon mirror  4  reflects the laser light radiated from the radiation unit  2  and reflected by the reflection mirror  3 , and directs the laser light toward the vehicle forward area through the radiating window  1   e . As the polygon mirror  4  is rotated, the angle of the side face of the polygon mirror  4  changes. As a result, the angle of projection of the laser light is changed to scan a predetermined forward area of the vehicle.  
         [0027]     The light receiver unit  6  includes, as shown in  FIG. 3 , a Fresnel lens  6   a  and a light receiving element  6   b  such as a photo diode. The Fresnel lens  6   a  collects the laser light. The Fresnel lens may be replaced with other lenses that collect reflected laser light. The light receiving element  6   b  receives the collected light and produces an output voltage or output current varying with the intensity of the received light. The output voltage or current is applied to the control circuit of the circuit board  5 .  
         [0028]     As shown in  FIGS. 4 and 5 , the Fresnel lens  6   a  is integrally molded with the inner case  1   c . The peripheral part of the Fresnel lens  6   a , specifically the part which does not operate to collect the laser light, is covered with the inner case  1   c . Thus, the Fresnel lens  6   a  is fixed to the inner case  1   c . Thus, when the inner case  1   c  is fixed in position in the first and the second cases  1   a  and  1   b , the Fresnel lens  6   a  is not displaced. As a result, the optical axis of the Fresnel lens  6   a  is held in a predetermined positional relation with the optical axis of the laser light radiated through the radiating window  1   e.    
         [0029]     The Fresnel lens  6   a  and the inner case  1   c  is integrally molded as shown in  FIG. 6 . The Fresnel lens  6   a  is placed at a desired position in a fixed die  10  with its one surface, which is to be directed forward to face the window  1   f , directed downward. The fixed die  10  has positioning walls  101  or the like at the position of mounting the Fresnel lens  6   a , so that the Fresnel lens  6   a  is maintained immovably from the desired position in the process of molding.  
         [0030]     Next, a sliding die (movable die)  11  is placed above the Fresnel lens  6   a  in the fixed die  10  so that no resin is injected in the rear side of the Fresnel lens  6   a . Thus, a space is provided between the Fresnel lens  6   a  and the light receiving element  6   b . A movable die  12  is placed on the fixed die  10 . The fixed die  10 , sliding die  11 , the movable die  12  and the Fresnel lens  6   a  are shaped to provide an inner space that corresponds to the inner case  1   c  in shape.  
         [0031]     Resin is injected into the dies  10  and  12  through a resin injection hole  12   a . After the injected resin solidifies, the dies  11  and  12  are moved away from the fixed die  10  so that the inner case  1   c  to which the Fresnel lens  6   a  is integrally molded is produced.  
         [0032]     The injected resin may be in fluid state of about 300° C. If the Fresnel lens  6   a  is made of resin such as a polycarbonate, which is likely to melt at high temperatures, the Fresnel lens  6   a  may melt in the injection molding process. Therefore, it is preferred that the temperature of the resin fluid around the Fresnel lens  6   a  is lowered. For instance, a cooling device may be provided in the sliding die  11  or in a part of the fixed die  10  facing the Fresnel lens  6   a.    
         [0033]     After the injection molding of the inner case  1   c , other parts are assembled to the inner case  1   c . Then the inner case  1   c  is assembled to the second case  1   b  together with the circuit board  5 . The first case  1   a  is assembled to the second case  1   b  to cover various parts.  
         [0034]     The object detecting apparatus constructed and manufactured as above operates in the following manner, assuming that it is mounted in a vehicle and an auto-cruise control system switch is turned on. The following operation is mostly controlled by the control circuit of the circuit board  5 .  
         [0035]     The reflection mirror  3  is first driven to a predetermined angular position by the motor. The light radiation unit  2  radiates the laser light at predetermined intervals. The laser light is reflected by the reflection mirror  3  and the polygon mirror  4  to be directed toward the forward area of the vehicle through the radiating window  1   e  as shown with an arrow in  FIG. 2 . When the laser light is reflected by an object such as a preceding vehicle, the reflected light passes the light enters the light receiver unit  6  through the light receiving window  1   f.    
         [0036]     In the light receiver unit  6 , the reflected light is collected by the Fresnel lens  6   a  and received by the light receiving element  6   b . The light receiving element  6   b  generates an output signal in response to the reception of the collected light. Based on this output signal, the control circuit calculates a distance L to the forward object by using the laser light travel speed V and the time difference T between the laser light radiation by the radiation unit  2  and the reception of the laser light by the light receiver unit  6 : L=V×T/2.  
         [0037]     The calculated distance is output through the connector  1   h  to various devices such as an engine control ECU and a brake control ECU provided outside the case  1 . As a result, the ECUs may control an engine and/or brakes to maintain the distance to the object at a predetermined distance.  
         [0038]     According to the above embodiment, the Fresnel lens  6   a  is integrally molded with the inner case  1   c , and the Fresnel lens  6   a  is protected from displacing from the desired position during the molding process. Therefore, the Fresnel lens  6   a  is fixedly attached to the inner case  1   a  such that its optical axis is directed toward a predetermined position. When the light radiation unit  2  and other parts are fixed to the inner case  1   c  or the cases  1   a ,  1   b , the optical axis of the Fresnel lens  6   a  is put in a state of correspondence with the optical axis of the laser light radiated by the light radiation unit  2  in a self-aligned manner. As a result, the optical axis adjustment of the Fresnel lens  6   a  can be obviated and the manufacturing process of the apparatus is simplified.  
         [0039]     The present invention should not be limited to the above embodiment, but may be implemented in many other ways.