Abstract:
The invention relates to an optoelectronic detection device, in particular a laser scanner, comprising at least one transmitter unit for the transmission of electromagnetic radiation, preferably pulsed electromagnetic radiation, at least one receiver unit associated with the transmitter unit and at least one radiation deflection device with which radiation transmitted by the transmitter unit can be guided into a monitored zone and radiation reflected from the monitored zone can be guided onto the receiver unit, with the front of the radiation propagating in the direction of the deflection device being of elongated shape and the deflection device being formed and being movable relative to the elongated radiation front such that the radiation front reflected into the monitored zone adopts different orientations in space in dependence on the position of the moved deflection device.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to an optoelectronic detection device comprising at least one transmitter unit for the transmission of electromagnetic radiation, preferably pulsed electromagnetic radiation, at least one receiver unit associated with the transmitter unit and at least one radiation deflection device with which radiation transmitted by the transmitter unit can be guided into a monitored zone and radiation reflected from the monitored zone can be guided onto the receiver unit. 
     Such detection devices are generally known and are attached to vehicles, for example, to detect the environment of the vehicle during the journey. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide an optoelectronic detection device of the kind first named which allows a reliable detection of the monitored zone and is designed as simply as possible and which, in particular, has as few moving components as possible. 
     This object is satisfied in that the front of the radiation propagating in the direction of the deflection device is of elongated shape and the deflection device is made and is movable relative to the elongated radiation front such that the radiation front reflected into the monitored zone adopts different orientations in space in dependence on the position of the moved deflection device. 
     In accordance with the invention, the scanning of the monitored zone not only takes place with the aid of punctiform radiation transmitted into the monitored zone, but the detection device is able to transmit an elongated radiation front into the monitored zone. The radiation deflection device serves this purpose and deflects the elongated radiation front subsequent to its generation such that the radiation front is transmitted into the monitored zone in an orientation dependent on the position of the deflection device. The scanning of the monitored zone therefore takes place by means of a two-dimensional radiation front which—together with the movement of the deflection device—results in a three-dimensional or quasi three-dimensional scanning of the monitored zone. When a correspondingly designed receiver unit is used, individual sections of the reflected elongated radiation front can be evaluated separately; i.e. a section of the respectively scanned object can be recorded for every direction in which the light line or streak is transmitted. Furthermore, different orientations of the radiation front transmitted into the monitored zone can be realized by means of the movable deflection device, whereby the optoelectronic detection device in accordance with the invention can be directly adapted to the respective application. 
     It is of special advantage for the invention that the deflection device is the only component which has to be moved in order to scan the monitored zone by means of the radiation front. The transmitter unit and the receiver unit, as well as the supply and connection devices associated therewith, do not have to be moved. The design of the detection device in accordance with the invention is hereby substantially simplified. Since the deflection device is moved relative to the propagating radiation front, the orientation of the radiation front does not change with respect to the alignment of the receiver unit; i.e. the orientation of the radiation front is the same before its deflection into the monitored zone, on the one hand, and after reflection in the monitored zone and a repeated deflection back in the direction of the receiver unit, on the other hand. For this reason, it is not necessary to take the different orientations of the radiation front in the monitored zone into account in the design of the receiver unit, which keeps the design of the receiver unit simple. 
     It is furthermore of advantage in accordance with the invention that no optical components are required for the production of the elongated radiation front which have to move together with the deflection device. The design of the detection device in accordance with the invention is hereby further simplified. In accordance with the invention, an especially low construction height, and thus an advantageous compact design overall, can be realized in particular, since no components which have to be moved together with the deflection device are required between the transmitter unit and/or the receiver unit, on the one hand, and the deflection device, on the other hand, to generate the radiation front. 
     The transmitter unit is preferably formed to transmit the elongated radiation front. Here, it is the transmitter unit itself which generates the elongated radiation front so that no optical components are needed between the transmitter unit and the radiation deflection device. 
     In a particularly preferred embodiment of the invention, the radiation front is a continuous radiation line. Consequently, a light line or streak is transmitted into the monitored zone with which objects located in the monitored zone are scanned not line by line, but areally so that a three-dimensional scanning takes place overall. 
     Alternatively, the elongated radiation front can also be formed by discrete radiation spots or beads arranged along a line in that, for example, a plurality of “light fingers” or individual rays are simultaneously directed onto the deflection device, for example by a correspondingly designed transmitter unit. A three-dimensional detection of the monitored zone is also possible in this way. 
     It is further preferred for the radiation to propagate in an expanding manner in the direction of the deflection device. The origin of the expansion is preferably not moved relative to the transmitter unit and the receiver unit during operation. The origin of the expansion is in particular formed by the transmitter unit. 
     The radiation propagating from the transmitter unit to the deflection device is preferably uninfluenced by optical components serving for the radiation refraction or diffraction of the radiation. A particularly advantageous compact design of the detection device can hereby be realized. 
     This compact design, resulting in particular through reduction of the construction height, is a substantial step in the direction of a miniaturization of optoelectronic detection devices, which is in particular of importance for the use on or in vehicles, where there is as a rule little room available for such detection devices. The wind resistance is moreover hereby minimized. 
     In a particularly preferred practical embodiment of the invention, the deflection device is rotatable and in particular adapted to carry out a continuous rotational movement at a constant speed. A scanning or scanner function is hereby realized with which it is possible to realize scanning over an angular range of up to 360° and thus a monitoring of the total environment of the detection device. 
     The radiation deflection device preferably has at least one planar reflection surface for radiation transmitted by the transmitter unit and reflected from the monitored zone. This reflection surface is preferably a planar mirror. The deflection device is in particular made as a mirror device and/or as a prism device. 
     It is further proposed that a reflection surface of the deflection device extends in an inclined manner with respect to a transmission plane and/or a reception plane and the deflection device is rotatable about an axis extending approximately perpendicular to the transmission plane and/or the reception plane. 
     In this way a situation is achieved in which, in a rotated position of the deflection device, the radiation front reflected by the reflection surface into the monitored zone is perpendicular with respect to the transmission plane and/or the reception plane; i.e. a light line is transmitted more or less upright. By further rotation of the deflection device by 90°, the radiation front transmitted into the monitored zone lies in a plane extending parallel to the transmission plane and/or the reception plane; i.e. the operation is carried out with a more or less horizontally lying light line. In intermediate rotational positions of the deflection device, the radiation front then extends in a more or less inclined manner to the transmission plane and/or the reception plane. With a rotating deflection device, work is consequently carried out with a rotating image or with a rotating light line or streak. 
     In accordance with a further preferred embodiment of the invention, provision is made for the transmitter unit to include at least one laser diode as a radiation source which is made for the transmission of a linear or streak-shaped radiation front. 
     Provision is furthermore preferably made for an optical transmission system to be installed in front of a radiation source of the transmitter unit. The radiation source, in particular a laser diode, and the optical transmission system can be combined to form a compact unit. In this way, additional optical components are not required between the transmitter unit and the deflection device for the generation of the elongated radiation front, whereby an advantageous compact construction of the detection device in accordance with the invention is achieved overall. 
     It is furthermore proposed in accordance with the invention for the receiver unit to have at least one areal radiation receiver. The radiation receiver is preferably matched to the elongated shape of the radiation front and in particular has an approximately strip-like basic shape. 
     The receiver unit, in particular an areal radiation receiver of the receiver unit, preferably includes a plurality of photodiodes which are in particular arranged in a single-line or multi-line manner. 
     Provision is preferably further made for the transmitter unit and the receiver unit to form an at least approximately common transmission/reception plane. This transmission/reception plane is in particular formed by an optical transmission system disposed in front of the radiation source as well as by an optical reception system of the receiver unit disposed in front of an areal radiation receiver. 
     The invention moreover relates to the use of at least one optoelectronic detection device such as was described above in connection with a vehicle. In this connection, the optoelectronic device is in particular used for object recognition and tracking. 
     In this connection, an optoelectronic detection device is preferably used which is made and is attached to or in the vehicle such that, in normal driving operation, the radiation front comprising an elongated shape extends at least substantially in the vertical direction on propagation toward the front in the direction of travel. 
     This use has the advantage that height information, for example on vehicles traveling in front of the vehicle equipped with the detection device, can be obtained from the region disposed in front of the vehicle in the direction of travel. 
     Further preferred embodiments of the invention relating both to the optoelectronic detection device itself and to the use in accordance with the invention are also set forth in the description and the drawing. 
     The invention will be described in the following by way of example with reference to the drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 a  shows an embodiment of an optoelectronic detection device in accordance with the invention in a side view with a deflection device disposed in a rotational position; 
     FIG. 1 b  shows the detection device of FIG. 1 a  in plan view; 
     FIG. 2 a  shows the detection device of FIG. 1 a  with a deflection device disposed in another rotational position; 
     FIG. 2 b  shows the detection device of FIG. 2 a  in a plan view; 
     FIG. 3 is a side view of an optoelectronic detection device in accordance with the invention comprising an optical system and a mirror sub-assembly; 
     FIG. 4 is a plan view of a receiver array of the detection device of FIG. 3; 
     FIG.5 illustrates the functional principle of the radiation source of the detection device of FIG. 3; and 
     FIG. 6 is a representation to explain the scanned image of a detection device in accordance with the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The detection device in accordance with the invention includes a transmitter unit  11  which has a laser diode  25  serving as a radiation source and an optical transmission system  27  in the form of a lens or a lens arrangement disposed in front of the laser diode  25 . Furthermore, a receiver unit  13  is provided which has an areal radiation receiver  29  which is formed, for example, by photodiodes arranged in a line and in front of which an optical reception device  31 , formed for example by a lens, is disposed. 
     A prism  15 , which serves as a radiation deflection device and has a planar reflection surface  19  facing the transmission/reception plane, is rotatable continuously at a constant speed about an axis  23  extending perpendicular to the transmission/reception plane. For this purpose, the prism  15  is connected to a drive unit  33 . 
     For certain vehicle applications, a scanning frequency of 10 Hz, i.e. of 10 scans per second covering 360° in each case, and an angular resolution of at least 1° are required. Here, the laser diode  25  must produce radiation pulses with a frequency of 3600 Hz for an angular resolution of 1°. The laser diode  25  of the scanner in accordance with the invention works with a pulse frequency of 14,400 Hz, whereby an angular resolution of 0.25° is achieved. 
     The optical transmission system  27  provides a fan-like widening or expansion of the radiation produced by the laser diode  25  such that the front  17  of the radiation propagating in the direction of the reflection surface  19  is of line shape and consequently, in the rotational position of the deflection device  15  in accordance with FIGS. 1 a  and  1   b , a radiation line  17 ′ is transmitted into the monitored zone which stands perpendicular to the transmission/radiation plane. 
     The orientation of the radiation front  17 ′ reflected into the monitored zone changes on rotation of the prism  15  relative to the transmitter unit  11  and to the receiver unit  13 , and thus relative to the elongated radiation front  17  propagating in the direction of the reflection surface  19 ; i.e. the light line  17 ′ rotates with the prism  15 . 
     FIGS. 2 a  and  2   b  show the other extreme case with the deflection device  15  rotated by 90° with respect to the position of FIGS. 1 a  and  1   b . The radiation front  17  still having the same orientation between the transmitter unit  11  and the reflection surface  19  is transmitted, as a result of the changed orientation of the reflection surface  19  extending in an inclined manner to the transmission/reception plane, as a radiation line  17 ′ into the monitored zone which lies in a plane extending parallel to the transmission/reception plane. 
     The light line  17 ′ transmitted into the monitored zone has a more or less strongly inclined position in the intermediate rotational positions (not shown) of the prism  15 . 
     The detection device in accordance with the invention is preferably used in connection with a vehicle for object recognition and object tracking. In this connection, the detection device is preferably attached in or on the vehicle such that the transmission/reception plane extends horizontally, i.e. perpendicular to the vertical axis of the vehicle, in normal driving operation, i.e. with a horizontally oriented vehicle, and the upright light line or streak  17 ′ in accordance with FIGS. 1 a  and  1   b  is transmitted to the front in the direction of travel of the vehicle. The division of the radiation receiver  29  of the receiver unit  13  into a plurality of individual receivers allows a separate evaluation of different regions of the light line or streak reflected onto the receiver  29  and thus the detection of contour profiles of the respectively scanned objects. 
     With this application, the regions disposed to the side of the vehicle are scanned with a horizontally extending radiation front, i.e. with a lying light line, such that—in contrast to the scanning to the front in the direction of travel—no height information is gained. However, since information from regions disposed in front of the vehicle in the direction of travel is of very high relevance in most vehicle applications, this circumstance can be accepted without problem in practice, especially since a light line which is lying and extends parallel to a plane extending perpendicular to the axis of rotation  23  of the deflection device  15  provides the advantage of a multiple scan at least for specific vehicle applications. The light line, which is lying or is disposed in the scanning plane, moreover advantageously allows a reduction in the scanning frequency, since a plurality of measuring points disposed next to one another are measured with it at the same time. The scanning frequency can thus be reduced by a factor corresponding to the number of measuring points. 
     The optoelectronic detection device shown in FIG. 3 is likewise a laser scanner. It comprises a laser module  147 , which includes a laser chip, and has a connection  149 , the laser module serving as a linear radiation source, a projection lens  143  serving as a transmitting lens, a mirror  133  rotatable about an axis  139  by means of a motor  131  and a receiver unit which includes a receiver lens  145  surrounding the projection lens  143  and a receiver member having an areal radiation receiver in the form of a diode array which has a one-row arrangement of a plurality of photodiodes. 
     The mirror sub-assembly is arranged in a glass tube  141 . The angular position of the mirror  133  is determined by means of an encoder disk  137  and an angular measuring device  135 . 
     The radiation  155  transmitted by the transmitter unit, exiting the glass tube  141  after reflection at the mirror  133  and entering into the monitored zone, is again guided—after reflection in the monitored zone as incident radiation  153 —via the mirror  133  onto the receiver lens  145  and from this onto the diode array of the receiver member  151 . 
     FIG. 4 shows the diode array  121  of the receiver member  151  which consists in this example of eight avalanche photodiodes  113  arranged in a row and serving as an areal radiation receiver. The individual diode elements  113  are separated from one another by webs  119  at which the receiver  121  is “blind”. 
     The diode array  121  protected by a glass window  111  is arranged in a housing  115  provided with connector pins  117 . A separate amplifier (not shown) is connected to each individual diode  113  so that a separate distance measurement can be carried out for each field of view corresponding to one of the individual diodes  113 . The amplifiers are connected to a common evaluation unit (not shown). 
     FIG. 5 schematically shows the laser chip  147  of the transmitter unit which has a p-n junction  123  serving as a linear radiation source. A projection lens  143  is disposed in front of the laser chip  147 . The transmitter unit of laser module  147  and transmitter lens  143  generates a radiation line or light streak  127  as a projected image of the linear radiation source  123 . 
     The expanded radiation propagating as a radiation line, i.e. the elongated radiation front transmitted by the transmission unit  143 ,  147 , strikes the inclined mirror  133 , which rotates with respect to the stationary transmitter/receiver unit, and is reflected out of the tube  141  into the monitored zone in an orientation dependent on the rotational position of the mirror  133 . 
     FIG. 6 shows the projected scanned image of the detection device in accordance with the invention for a complete revolution of the rotating mirror  133  including a horizontal angle of 360°. The image  165  of the line-like laser source  123  is rotated once about itself with respect to the horizon  161  in a mirror rotation due to the rotating mirror  133 , whereby a sinusoidal expansion with an envelope  169  is created, with the sinusoidal curve defining the effective height of the light line. 
     With a laser scanner installed on a vehicle, this is aligned such that the antinodes of the sinusoidal expansion are directed to the front in the direction of travel and in the backward direction such that, in these directions, an expansion of the radiation takes place in the vertical direction which is advantageous for at least most vehicle applications; i.e. the vehicle environment is scanned to the front and rear with a large vertical angle. 
     In FIG. 6, the position of a region  167  of the projected line image  165  corresponding to one of the eight diode elements  113  is shown for different orientations of the line image  165  to illustrate the movement of this part of the overall line-shaped visual field during the scanning operation. 
     The continuously changing orientation of the line-shaped image  165  of the linear radiation source  123  in the monitored zone is taken into account in the evaluation of the received radiation  153  by means of the evaluation unit connected to the receiver member  151 , with said image  165  always being imaged on the diode array  121  which is stationary and thus always having the same orientation in the scanner.