Abstract:
A position determining system is disclosed, which has a simplified configuration capable of producing a plurality of phantom planes simultaneously. The improved system according to the present invention consists of a light receiving and sensing device that includes a body having means for sending data on elevation- and depression-angles and horizontal angles, and a phantom plane determining function for determining phantom planes, so as to display or output differential angles of elevations and depressions in relation with the phantom surfaces produced from the data received from the body.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to a position determination and adjustment system in which a laser source is rotated while emitting laser beam, so as to produce an inclined plane making a certain inclination angle from a horizontal reference plane, and it also relates to a light sensing device used for the system. The position determination and adjustment system according to the present invention allows for creating a reference point, a reference line, and a reference plane for measurements.  
         PRIOR ARTS  
         [0002]    Prior art optical leveling apparatuses have been replaced with rotary laser devices used to produce a horizontal reference level covering a relatively large range.  
           [0003]    For recent years, rotary laser devices have become popular in use for determining vertical orientations, especially, for creating lines and planes based upon reference elevations. Such rotary laser devices, while emitting laser beam in horizontal directions, rotates, reciprocally sweeps, and halts to produce reference planes of rotations, partial reference lines, reference planes, reference segments, reference points, and the like.  
           [0004]    The rotary laser devices have been used to produce reference horizontal lines for the purpose of localization of window frames in interior constructions for buildings, and to produce reference horizontal planes for making mounts in construction sites and simulating sectional surfaces after cutting the grounds off. The rotary laser devices have also been used to set up reference points in determining inclinations for stairs, and some of those devices can produce reference planes inclined in one way or in two ways.  
           [0005]    One of such prior art rotary laser devices capable of producing inclined reference surfaces is disclosed in Japanese Patent Laid-Open No. H6-26861, and the configuration and operation of the disclosed rotary laser device will now be summed up.  
           [0006]    Referring to FIG. 24, a rotary laser device  951  has a casing  901  and a laser projector  903 . The casing  901  has its upper center portion recessed in a shape of a frustum of a cone to define a concave portion  902 . The laser projector  903  vertically extends through the center of the concave portion  902 . The laser projector  903  supported by the recessed portion  902  can be tilted on and around a spherical mount  904  formed in the middle thereof. A rotary unit  905  provided with a pentaprism  909  is mounted in an upper portion of the laser projector  903 . The rotary unit  905  is rotated through a drive gear  907  and sweep gear  908  powered by a sweep motor  906 .  
           [0007]    Two pairs of units of inclination mechanism (only one of the pairs is illustrated) are attached around the laser projector  903 . Either of the units  910  of the inclination mechanism includes a motor  911 , a screw  912 , and a nut  913  that are all cooperative to make inclination. The screw  912  is rotated through a driving gear  914  and a tilting gear  915  both powered by the motor  911 . The laser projector  903  is coupled to the nut  913  by a tilting arm  916  intervening therebetween. Rotations of the screw cause the nut  913  to vertically move, which, in turn, causes the laser projector  903  to tilt.  
           [0008]    Two sensors  918  and  919  are located and separately fixed to the laser projector  903  in the middle thereof in a plane orthogonal to a rotation axis of the rotary unit  905 . One of the fixed sensors, the sensor  918 , is positioned in parallel with the tilting arm  916  while the other, the sensor  919 , is oriented orthogonal to the tilting arm  916 . A flange  920  having a pivot pin  921  is fixed to a lower end of the laser projector  903 . An upper end of the pivot pin  921  pivotally supports an L-shaped tilting plate  922  at one point thereon, and an angle-determining sensor  929  and an angle-determining sensor  930  are incorporated in the L-shaped tilting plate  922 . The angle-determining sensor  929  is positioned in the same direction as the fixed sensor  918  while the angle-determining sensor  930  is positioned in the same direction as the fixed sensor  919 . The tilting plate  922  is connected to both the pairs of the units of inclining mechanism (only one unit is shown).  
           [0009]    Each of the units  925  of inclining mechanism includes a motor  926 , a screw  927  rotated by the motor  926 , and a nut block  928  through which the tilting screw  927  is screwed down, all of these components being cooperative to make a reference to inclination angle. One end of the tilting plate  922  is fitted on the nut block  928 . The motor  926  is actuated to rotate the screw  927  and vertically move the nut block  928 , and thus, the tilting plate  922  can be inclined.  
           [0010]    A laser beam projector (not shown) and a projector optical system (not shown) including optics such as a collimator lens that refracts incident rays from the laser beam projector into parallel rays are built in the laser projector  903 . Laser beam emitted from the projector optical system is deflected in horizontal direction by the pentaprism and radiated out of a projector window  931 .  
           [0011]    Functional features of the rotary laser device will now be described. Determination of an inclination angle is carried out by the inclining mechanism  925 . First, the inclination mechanism  910  is actuated to regulate postures of the fixed sensors  918  and  919  so that both of the sensors are horizontal. The motor  926  is then actuated to rotate the screw  927  and lift the nut block  928 , and consequently, the tilting plate  922  is inclined at an angle η relative to the flange  920  in a reverse angular direction to the desired predetermined angle η. The inclination angle η is detected by a component such as an encoder (not shown) linked to the motor  926 .  
           [0012]    Then, the inclination mechanism  910  is actuated to tilt the laser projector  903  so that the tilting plate  922  is detected as being horizontal. At this posture, an emission direction of light from the laser projector  903  inclines at the predetermined angle η relative to the horizontal plane. After the inclination angle in the emission direction of the laser light is determined, the laser beam deflected at the pentaprism  909  in a direction orthogonal to the rotation axis is radiated through the laser projector  903  while the rotary unit  905  is being rotated or the rotary unit  905  is reciprocally sweeping within a range equivalent to the predetermined angle, so as to produce an inclined reference plane.  
           [0013]    Japanese Patent Laid-Open No. H11-94544 discloses a post-construction elevation display apparatus and a post-construction elevation determining apparatus both of which are comprised of a laser device rotating simultaneous with irradiating laser beam and a finished elevation display. The post-construction elevation determining apparatus can determine a desired post-construction elevation by using the post-construction elevation display to receive laser beam irradiated by the laser device so as to detect a distance from the laser device to the display device and a deviation between the display device and a reference horizontal plane against which the laser beam is directed.  
           [0014]    Furthermore, Japanese Patent Laid-Open No. H11-118487 discloses a reference irradiated beam detecting apparatus incorporated with an inclination angle sensor, which is used in combination with a laser device.  
           [0015]    Additionally, Japanese Patent Laid-Open No. H7-208990 discloses a 3-dimensional coordinate determining apparatus including an irradiating means rotating and irradiating a plurality of plane beams and more than one reflecting means. The 3D coordinate determining means uses the plurality of reflecting means to reflect light emitted from the irradiating means and uses the irradiated means to receive the reflected beams to determine 3-dimensional coordinates in relation with the reflecting means.  
           [0016]    The prior art rotary laser device as in the above statement must have two pairs of units of inclining mechanism which support the laser projector  903  in a manner where the laser projector can have a full freedom of tilting in two ways, in order to produce inclined planes. Such prior art embodiment is disadvantageous in that it needs two of the fixed sensors  918  and  919  and two of the tilting sensors  929  and  930  and in that it requires a complicated configuration, i.e., it needs a control circuit to control an actuation of two of the pairs of the units of inclining mechanism, which results in an increased manufacturing cost. Moreover, the prior art rotary laser device disadvantageously produces only one reference plane but can never produce horizontal and inclined reference planes simultaneously, which disturbs determining a relative relation between the horizontal and inclined reference planes, or which disturbs determining a relative relation between two inclined reference planes different in inclination angle from each other.  
           [0017]    The prior art embodiment of the 3-dimensional coordinate determining device as disclosed in Japanese Patent Laid-Open No. H7-208990 should be further improved by accurately regulating an angular position of the reflecting means so as to return beams reflected from the reflecting means to the irradiating means. Additionally, the reflecting means must be moved in producing the predetermined reference plane, and a determination value also must be monitored at the irradiation means, which disadvantageously results in requesting more than one operators to dedicate themselves in handling the device.  
           [0018]    In order to overcome the aforementioned disadvantage, the present invention provides an improvement of a position determining system by which both a plane of arbitrary inclination and a horizontal reference plane of arbitrary elevation can be simultaneously determined without tilting a laser projector and without precisely locating a light receiving element.  
           [0019]    Accordingly, it is an object of the present invention to provide a position determining system of a simplified mechanism that is capable of producing a horizontal reference plane and a plurality of inclined planes simultaneously.  
           [0020]    It is another object of the present invention to provide a position determining system of simplified operation which permits a single operator to work sufficiently.  
           [0021]    It is still another object of the present invention to provide a light receiving and sensing device of a simplified mechanism that is capable producing a horizontal reference plane and an inclined reference plane simultaneously.  
         SUMMARY OF THE INVENTION  
         [0022]    The present invention is an improved system consisting of a light receiving and sensing device that includes a body having means for sending data on vertical angles and horizontal angles, and a phantom plane determining function for determining phantom planes, so as to display or output differential vertical angles in relation with the phantom surfaces produced from the data received from the body.  
           [0023]    The means for sending data on vertical angles is preferably laser light pivotal and diverging in a shape of a fan, and the means for sending data on horizontal angles is preferably configured with an encoder provided in a rotary element and a data transfer route aided by a communication means that relays the data detected by the encoder to the light receiving and sensing device.  
           [0024]    The communication means is preferably an optical communication or a wave communication.  
           [0025]    A light receiving section in the light receiving and sensing device may have a versatility of serving as either a vertical detecting element or a light receiving element for optical communication, and the light receiving section may have a condensing means.  
           [0026]    Also preferably, the diverging laser light is substantially of 3 or more diverging rays, and the pivotal diverging laser light of the means for sending data on vertical angles is correlated with the data transmitted from the encoder to the light receiving and sensing device for subsequent data transfer.  
           [0027]    With the system thus configured, the diverging beams emitted from a rotary laser device is received by the light receiving section in the light receiving and sensing device, and vertical angles of a location where the light receiving and sensing device is placed is computed from delays between points of time when the diverging beams are detected. Moreover, a rotational angular position transfer means provided in the rotary laser device transfers data on rotational angular positions to a receiving element of the light receiving and sensing device, and then, the light receiving and sensing device computes the location of the light receiving and sensing device from the rotational angular positions. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]    The best mode of the present invention will be explained in detail in conjunction with the accompanying drawings in which like alphanumeric symbols denote the corresponding elements and parts throughout the drawings:  
         [0029]    [0029]FIG. 1 is a schematic perspective view showing an embodiment of a position determining system according to the present invention;  
         [0030]    [0030]FIG. 2 is a view illustrating beams diverging in three-dimensional space after being emitted from a rotary laser device in the exemplary position determining system according to the present invention;  
         [0031]    [0031]FIG. 3 is a sectional view showing the exemplary position determining system according to the present invention;  
         [0032]    [0032]FIG. 4 is a diagram showing another embodiment of the rotary laser device in the position determining system according to the present invention;  
         [0033]    [0033]FIG. 5 is a diagram showing still another embodiment of the rotary laser device of the position determining system according to the present invention;  
         [0034]    [0034]FIG. 6 is a diagram showing a manner in which laser beam transmitted by diffraction grating is converted into diverging beams;  
         [0035]    [0035]FIG. 7 is a perspective view showing an embodiment of the rotary laser device that irradiates diverging beams varied in polarization;  
         [0036]    [0036]FIG. 8 is a sectional view showing the rotary laser device which emits diverging beams varied in polarization;  
         [0037]    [0037]FIG. 9 is an exploded view illustrating a laser projector and rotary section of the rotary laser device which emits diverging beams varied in polarization;  
         [0038]    [0038]FIG. 10 is a sectional view showing an embodiment of a rotary laser device that utilizes laser beam to transmit data on rotational angular positions;  
         [0039]    [0039]FIG. 11 is a view illustrating a light receiving and sensing device in an embodiment of the position determining system according to the present invention;  
         [0040]    [0040]FIG. 12 is a diagram showing the inside of the light receiving and sensing device;  
         [0041]    [0041]FIG. 13 is a graph showing signals detected by the light receiving and sensing device;  
         [0042]    [0042]FIG. 14 is a graph showing signals detected by the light receiving and sensing device at short signal detection intervals;  
         [0043]    [0043]FIG. 15 is a diagram showing a light receiving and sensing device for receiving diverging beams different in polarization from one another;  
         [0044]    [0044]FIG. 16 is a graph showing examples of laser light that carry rotational angular position signals;  
         [0045]    [0045]FIG. 17 is a diagram showing a light receiving and sensing device having a light receiving section at which a rotational angular signal are received;  
         [0046]    [0046]FIG. 18 is a perspective view showing directions of emitted laser diverging beams and laser light that carries the rotational angular signal;  
         [0047]    [0047]FIG. 19 is a diagram showing an embodiment of the light receiving and sensing device that has an omni-directional light receiving feature;  
         [0048]    [0048]FIG. 20 is a diagram showing a light receiving and sensing controller incorporated in the light receiving and sensing device in FIG. 19;  
         [0049]    [0049]FIG. 21 is a flow chart illustrating procedural steps of an embodiment of the position determining system according to the present invention;  
         [0050]    [0050]FIG. 22 is a diagram showing a relation of simulated inclined planes with coordinate axes;  
         [0051]    [0051]FIG. 23 is a diagram showing various exemplary pattern of emitted diverging beams; and  
         [0052]    [0052]FIG. 24 is a sectional view showing the prior art example of the rotary laser device. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0053]    A position determining system according to the present invention will now be described in more detail with reference to the drawings.  
         [0054]    (1) Preferred Embodiment 1  
         [0055]    (1.1) General Configuration of the Position Determining System  
         [0056]    First, a configuration of the position determining system according to the present invention will be outlined. As shown in FIG. 1, a position determining system  100  of the present invention includes a rotary laser device  151  and a light receiving and sensing device  154 . The rotary laser device  151  emits three diverging laser beams,  152   a ,  152   b , and  153 , while rotating the diverging beams about a point C. As can be seen in FIG. 2, the diverging beams  152   a  and  152   b  are emitted in an orthogonal direction to the horizontal plane while the diverging beam  153  is emitted at an angle θ with the horizontal surface. A cross line of the diverging beam  153  with the horizontal plane bisects an angle at which the diverging beams  152   a  and  152   b  meet. In other words, an angle made between the cross line and the diverging beam  152   a  is equivalent to an angle made between the cross line and the diverging beam  152   b , being expressed as d by way of reference. The three beams  152   a ,  152   b , and  153  rotate, keeping such relations with one another, and therefore, the diverging beams  152   a ,  152   b , and  153  cross a light receiving and sensing device one after another with time delay. The embodiment of the invention utilizes the time delay to determine a straight line on both the light receiving and sensing device and the point C, and an angle γ made between the straight line and the horizontal plane. The angle γ herein is referred to as “vertical angle”.  
         [0057]    (1.2) Rotary Laser Device  
         [0058]    (1.2.1) Rotary Laser Device Emitting Three Diverging Beams of Laser Light  
         [0059]    A rotary laser device will now be described, which rotates about a vertical axis while emitting three diverging beams of laser light.  
         [0060]    Referring to FIG. 3, a rotary laser device  151  according to the present invention has a casing  101  and a laser projector  103 . The casing  101  is recessed in a shape of a frustum of a cone at the center of its upper surface to define a concave portion  102 . The laser projector  103  vertically extends through the center of the concave portion  102 . The laser projector  103  supported by the recessed portion  102  can be tilted on and around a spherical mount  104 . A rotary unit  105  provided with a pentaprism  109  is mounted in an upper portion of the laser projector  103 . The rotary unit  105  is rotated through a drive gear  107  and sweep gear  108  powered by a sweep motor  106 .  
         [0061]    The rotary laser device  151  has two pairs of units of inclination mechanism (only one of the pairs is illustrated) that are attached around the laser projector  103 . Either of the units  110  of the inclination mechanism includes a motor  111 , a screw  112 , and a nut  113  that are all cooperative to make inclination. The screw  112  is rotated through a driving gear  114  and a tilting gear  115  both powered by the motor  111 . The nut  113  is coupled to the laser projector  103  by a tilting arm  116  intervening therebetween. Rotations of the screw cause the nut  113  to vertically move, which, in turn, causes the laser projector  103  to tilt. The other of the pairs not shown in the drawing uses a similar manner to the above-mentioned one of the units  110  and tilts the projector  103  in a direction perpendicular to the inclination direction of the above-mentioned unit.  
         [0062]    A fixed sensor  118  in parallel with the tilting arm  116  and a fixed sensor  119  orthogonal to the tilting arm  116  are located in the middle of the laser projector  103 . One of the units  110  of the inclination mechanism controls a tilt of the tilting arm  116  to always keep the fixed sensor  118  in horizontal orientation. Similarly, at the same time, the other of the units  110  can control the fixed sensor  119  to permanently keep its horizontal orientation.  
         [0063]    The laser projector  103  and the rotary unit  105  will now be described. As will be recognized in FIG. 4, a laser beam projector  132  and a projector optical system including optics such as a collimator lens  133  that refracts incident rays from the laser beam projector  132  into parallel rays are built in the laser projector  103 . Laser beam emitted from the projector optical system is split into three diverging beams,  152   a ,  152   b , and  153 , by a diffraction grating (BOE)  134  in the rotary unit  105 . The diverging beams  152   a ,  152   b , and  153  are respectively deflected in horizontal direction by pentaprism and radiated out of a projector window  131 .  
         [0064]    As shown in FIG. 5, a diffraction grating (BOE)  134   a  may be placed in a position at which laser beam is transmitted after being deflected by the pentaprism  109 . Such a configuration as depicted in FIG. 5 is identical that depicted in FIG. 4 except for a location of the diffraction grating  134   a.    
         [0065]    As can be seen in FIG. 6, the laser beam, after transmitted by the diffraction grating (BOE)  134 , is split into the three diverging beams  152   a ,  152   b , and  153 .  
         [0066]    As has been stated, the laser projector  103  irradiates laser beams that are originally emitted from the laser light projector  132  and then split into the three diverging beams  152   a ,  152   b , and  153  by the diffraction grating (BOE)  134 . The laser beams are respectively deflected in a horizontal direction by the pentaprism  109  while the rotary unit  105  is being rotated, so as to produce a reference plane.  
         [0067]    (1.2.2) Rotary Laser Device Emitting Three Diverging Laser Beams Different in Polarization  
         [0068]    An alternative rotary laser device will now be described, which emits three diverging laser beams different in polarization from one another.  
         [0069]    As will be detailed hereinafter, in order to attain a position determination with high accuracy, it is advantageous to use a rotary laser device that emits three diverging laser beams having their respective polarization patterns different from one another. As shown in FIG. 7, a rotary laser device  151   a  emits three diverging beams  152   c ,  152   d , and  153   a . Three of the diverging beams  152   c ,  152   d , and  153   a  are polarized in manners varied from one another, and thus, the light receiving section of the light receiving and sensing device  154   a  can distinguish those three diverging beams  152   c ,  152   d , and  153   a  one from the other.  
         [0070]    As shown in FIG. 8, a mechanism used to tilt the laser projector components are all identical with those depicted in FIG. 3 except for a laser projector  103   a  and a rotary unit  105   a  attached thereto both of which are built in the rotary laser device  151   a . For convenience of description, the laser projector  103   a  and the rotary unit  105   a  alone will be explained below.  
         [0071]    With reference to FIG. 9, the rotary laser device  151   a  emitting the diverging beams  152   c ,  152   d , and  153   a  of different polarizations includes the laser projector  103   a  and the rotary unit  105   a . Directions of the laser beams passing through each optical element in the drawing are shown by arrows of solid lines while polarization directions of the laser beams are shown by arrows of broken lines.  
         [0072]    When laser diode is used for the laser beam projector  132   a  in the laser projector  103   a , the resultant laser beam polarizes linearly. Assume that the laser beam is polarized in X-direction and is emitted in Z-direction, and that a direction perpendicular to an X-Z plane is Y-direction. The laser beam emitted from the laser beam projector  132   a  is collimated by a collimator lens  133   a  to be directed at a quarter-wave plate  140 . The quarter-wave plate  140  is oriented so that the laser beam emitted from the laser beam projector  132   a  and linearly polarized in the X-direction is circularly polarized. After transmitted by the quarter-wave plate  140 , the laser beam is passed through another quarter-wave plate  139  and linearly deflected in a direction meeting at an angle of 45 degree with the X-direction, as illustrated in FIG. 9. Since the rotary unit  105   a  is rotatably supported, the quarter-wave plates  140  and  139  vary in their relative positions. However, as the laser light passing through the quarter-wave plate  140  is circularly deflected beam, such beam after passing through another quarter-wave plate  139  is not influenced by variations in the relative positions of the quarter-wave plates, but a direction of the linear deflection of the beam is determined merely by the quarter-wave plate  139 . Then, the laser beam is passed through a polarized-beam splitter  141 . The polarized-beam splitter  141  is configured so as to reflect components deflected in the Y-direction while transmitting components deflected in the X-direction. Thus, the laser beam linearly deflected by the quarter-wave plate  139  in the direction making the angle of 45 degree with the X-direction has its Y-directional components reflected by the polarized-beam splitter  141  and deflected by an angle of 90 degree and has its X-directional components transmitted by the polarized-beam splitter  141 .  
         [0073]    The laser beam reflected by the polarized-beam splitter  141  is incident upon still another quarter-wave plate  138  to be circularly deflected, and thereafter, it is reflected by a cylinder mirror  136 . The cylinder mirror  136  is oriented in such a manner that the laser beam is orthogonal to the horizontal plane when emitted from the rotary unit  105   a . Also, a declination prism  136   a  is placed between the quarter-wave plate  138  and the cylinder mirror  136 . The declination prism  136   a  is bisected at its center and has a transmission declination prism that develops an angle 2δ between diverging beams  152   c  and  152   d  emitted by the rotary unit  105   a . The laser beam reflected by the cylinder mirror  136  is transmitted again by the declination prism  136  and the quarter-wave plate  138  to be linearly polarized in the Z-direction, and hence, this time, the beam can be transmitted by the polarized-beam splitter  141  to be emitted out of the rotary unit  105   a.    
         [0074]    On the other hand, the laser beam transmitted thorough the polarized-beam splitter  141  is incident upon further another quarter-beam splitter  137  to be circularly polarized and then is reflected by a cylinder mirror  135 . The cylinder mirror  135  is oriented in such a manner that the laser beam meets the horizontal plane at an angle θ when emitted from the rotary unit  105   a . Since the laser beam reflected by the cylinder mirror  135  is transmitted again by the quarter-wave plate  137  to be linearly polarized in the Y-direction, the polarized beam is reflected by the polarized-beam splitter  141  that has transmitted it upon entrance to a path toward the rotary unit, and the reflected beam is emitted out of the rotary unit  105   a.    
         [0075]    (1.2.3) Unit for Determining a Rotational Angular Position of the Light Receiving and Sensing Device Relative to the Rotary Laser Device  
         [0076]    Now, described below will be a rotational angular position determining unit which is used to determine a rotational angular position of the light receiving and sensing device  154   a  relative to the rotary laser device  151   a , or to determine which rotational angular position the light receiving and sensing device  154   a  is positioned in circular tracks at which the rotational laser device  151   a  direct laser light. The rotational angular position determining unit described herein can also be combined with the aforementioned rotary laser device  151  in the similar manner.  
         [0077]    The rotary laser device  151   a  includes, as illustrated in FIG. 8, an emission direction detecting means such as an encoder  117  detecting an angle of emitted laser beam and an angle signal transmitter  123  transmitting the detected emission angle to the right receiving and sensing device  154   a . The encoder  117  detects an angle of beam emission from the rotary unit  105   a . Data on the detected emission angle is successively sent to the light receiving and sensing device  154   a  by the angle signal transmitter  123 .  
         [0078]    Combined with the rotary laser device  151  shown in FIG. 3 for the laser projector  103  (see FIG. 5), an embodiment shown in FIG. 10( a ) can determine a rotational angular position of the light receiving and sensing device  154 . In such an embodiment, an angle signal projector  172  is used, which modulates light emitting diode (LED) or laser diode varied in wavelength (color) from the diverging beams  152   a ,  152   b , and  153   a  to project light representing angular data onto the light receiving and sensing device  154 .  
         [0079]    Referring to FIG. 10( a ), the laser beam emitted from the angle signal projector  172  is reflected at a die clock prism  171  and then collimated by the collimator lens  133  to adjust beam angles so that the resultant beam covers the entire range of diversion made by the diverging beams  152   a ,  152   b , and  153 . The beam transmitted through the collimator lens  133  is transmitted by the pentaprism  109  and then reflected at a mirror  148  to be emitted out of the rotary unit  105  in a direction orthogonal to a rotation axis thereof. Laser beam  153   e  (see FIG. 10 a ( b )) has its rotational angular position determined by directing the beam at the light receiving and sensing device. A method of receiving the laser beam  153   e  to determine rotational angular positions will be explained later.  
         [0080]    Beam emitted from the laser beam projector  132  is transmitted through the die clock prism  171  and collimated by the collimator lens  133 . The collimated beam is reflected by a die clock mirror  149  and deflected by the pentaprism  109 . The deflected light is passed through the diffraction grating  134  and split into three diverging beams  152   a ,  152   b , and  153 .  
         [0081]    (1.3) Light Receiving and Sensing Device  
         [0082]    (1.3.1) Light Receiving and Sensing Device for the Rotary Laser Device That Emits Three Diverging Beam of Laser Light  
         [0083]    The light receiving and sensing device  154  will now be described which receives the diverging beams  152   a ,  152   b , and  153  emitted from the rotary laser device  151 . As shown in FIGS. 11 and 12, a box housing  164  of the light receiving and sensing device  154  is provided with a light receiving section  156  used to detect the diverging beams  152   a ,  152   b , and  153 . The box housing  164  includes a display  157 , a warning unit  161  such as a buzzer, input keys  162 , an index  163 , and a level rod  159 . The box housing  164  is incorporated with a memory  165 , a computation unit  166 , a scale reader  167  for the level rod, and an angle signal receiver  170 . The display  157  indicates information including an angle between a straight line joining a rotation center C of the laser beam and the light receiving section  156  and a rotational angular position of the light receiving and sensing device  154  relative to the rotary laser device  151 .  
         [0084]    (1.3.1.1) Principle of Angle Determination by the Light Receiving and Sensing Device  
         [0085]    As mentioned above, the rotary laser device  151  emits the diverging beams  152   a ,  152   b , and  153  in a pivotal manner. As illustrated in FIG. 2, the diverging beam  153  is emitted, meeting at an angle θ with the horizontal plane. A cross line of the diverging beam  152   a  with the horizontal plane and a cross line of the diverging beam  152   b  with the horizontal plane meet at an angle 2δ. Three of the diverging beams  152   a ,  152   b , and  153  rotate, keeping such relations with each other, and therefore, those beams cross the light receiving section  156  of the light receiving and sensing device  154  at a delay of time one after another in the order of the diverging beams  152   a ,  153 , and  152   b.    
         [0086]    When the light receiving section  156  of the light receiving and sensing device  154  is in a position A within the horizontal plane, light detected by the light receiving and sensing device  154  is indicated as in FIG. 13( a ). When the light receiving section  156  is in a position B vertically right above the position A, the detected diverging beam is indicated as in FIG. 13( b ). As can be seen in FIG. 13( a ), two of the diverging beams  152   a  and  152   b  are detected at time interval t 0 . Assume now that a time delay between detections of the diverging beam  152   a  and the diverging beam  153  is t. When the light receiving section  156  is in the position A within the horizontal plane, the time interval t is a half of the time interval t 0 . Thus, such a relation is expressed as in an equation 1. A rotation cycle in which the rotary laser device  151  rotates the diverging beams is T. 
           t   0 =2 t   (1) 
         [0087]    When the light receiving section  156  is in the position B above the horizontal plane, the time delay between the two detections is shorter than a half of to as illustrated in FIG. 13( b ). The time interval t becomes shorter as the light receiving section  156  is raised higher from the horizontal plane, and it can be obtained from an angle ∠BCA=γ between the straight line joining the position B of the light receiving section  156  and a emission point C of the diverging beams and the horizontal plane, namely, a vertical elevation or depression angle can be obtained from the time interval between the detections by an equation 2 as follows.  
             γ   =       δ        (     1   -       2      t       t   0         )          tan                 θ             (   2   )                               
 
         [0088]    When the light receiving section  156  is below the horizontal plane, the time interval t is longer than a half of the time interval t 0 . In this way, it can be distinguished if the light receiving section  156  is above or below the horizontal plane. Additionally, the equation 2 can be applied to a case where the light receiving section  156  is below the horizontal plane.  
         [0089]    (1.3.1.4) Principle of Determination for a Short Time Interval between the Detections  
         [0090]    As has been described, the light receiving and sensing device  154  measures the delayed time t 0  and t according which three of the diverging beams cross the light receiving section  156  in the light receiving and sensing device  154 , respectively, and computes them to produce an angle at which the straight line joining the light receiving section  156  and the emission point C of the diverging laser beams meets with the horizontal plane. When the time interval between the detections where two of the diverging beams  152   a  and 152 b  are received at the light receiving section, the accurate time delay t can be determined. However, as shown in FIGS.  14 ( b ) and  14 ( c ), when the time interval between the detections of two of the diverging beams  152   a  and  153  is short and signals at light receptions interfere with each other, the time interval t cannot be accurately determined. If the signals developed by two of the diverging beams  152   a  and  153  can be distinguished from one another from polarization patterns, those signals can be detected distinguishably and separately, and hence, even when the time interval t between two light receptions is short, the time delay t can be determined accurately.  
         [0091]    (1.3.2) Light Receiving and Sensing Device for the Rotary Laser Device Emitting Diverging Beams of Laser Light of Different Polarizations  
         [0092]    The light receiving and sensing device  154   a  will now be described which receives diverging laser beams  152   c ,  152   d ,  153   a  emitted by the rotary laser device  151   a  and varied in polarization from one another. Specifically, a configuration of part provided to distinguish the laser beams of different polarizations will be explained herein. Configurations and determination principles of the remaining part are the same as those in the light receiving and sensing device  154 .  
         [0093]    As depicted in FIG. 15( a ) and FIG. 15( b ) containing a sectional view taken along the line A-A in FIG. 15( a ), the light receiving section  156   a  of the light receiving and sensing device  154   a  has light receiving elements  156   b  and  156   c  and a polarized-beam splitter  169  provided right in front of each of the light receiving elements. The polarized-beam splitter  169  transmits or reflects laser beam depending upon a polarization direction upon entrance of the laser beam. The light receiving element  156   b  is provided for reflected beams while the light receiving element  156   c  is provided for transmitted beams, and in this way, the direction of polarization of the incident laser beam can be distinguished. If two of the diverging beams  152   c  and  153   a  are incident upon the light receiving section  156   a  with a short dime delay, the light receiving element  156   b  detects the diverging beam  152   c  while the light receiving element  156   c  detects the diverging beam  153   a , respectively, and thus, the time delay or interval can be accurately detected. Similarly, the light receiving section  156   a  can distinguish the diverging beam  153   a  from the diverging beam  152   d.    
         [0094]    (1.3.3) Determination of Rotational Angular Position of the Light Receiving and Sensing Device Relative to the Rotary Laser Device  
         [0095]    The light receiving and sensing device  154  has an angular signal receiving unit  170  (see FIG. 12) that successively receives data on emission angles forwarded by the angle signal transmitter  123  (see FIG. 3) provided in the rotary laser device  151 . The emission angle data received at the very instance when the light receiving and sensing device  154  has received the diverging beam  153  is utilized to determine a rotational angular position of the light receiving and sensing device  154  relative to the rotary laser device  151 . Such a manner of determining the rotational angular position by the angle signal receiving unit  170  can totally similarly be applied to the light receiving and sensing device  154   a  (see FIG.  15 ) that receives two of the diverging beams varied in polarization from each other.  
         [0096]    An alternative embodiment shown in FIG. 10 will be described which transmits laser light representing a rotational angular signal. The angle signal projector  172  emits laser light different in color (wavelength) from the diverging beams  152   a ,  152   b , and  153 , and thereafter, the laser light is made come up and out in a pattern as illustrated in FIG. 16( a ), for example, to transmit the rotational angular position. A signal shown in FIG. 16( a ) is composed of a reference signal S 1  and a digitized signal S 2  that comes up and out in a digitally coded pattern for the rotational angular position. The reference signal S 1  is emitted with the same time of delay while the digitized signal S 2  comes up and out in the digitally coded pattern between two of the reference signals. Digitized codes of the pattern are digital codes of the rotational angular position determined by the encoder  117  (see FIG. 3).  
         [0097]    [0097]FIG. 17( a ) and FIG. 17( b ) sectioned along the line A-A in FIG. 17( a ) illustrate the light receiving and sensing device  154   b  used in combination with this embodiment of the rotary laser device. Hereinafter, determination of a rotational angular position by the light receiving and sensing device  154   b  will be explained. Configurations of the remaining part are the same as those in the light receiving and sensing device  154 .  
         [0098]    The light receiving and sensing device  154   b  has an angular data receiving unit  155  used to receive a signal representing the rotational angular position that is emitted from the rotary laser device. The angular data receiving unit  155  has a color filter  155   a  and a light receiving element  155   b . The color filter  155   a  is positioned right in front of the light receiving element  155   b , and the light receiving element  155   b  receives only laser light representing angular data so as not to be affected by the diverging beams  152   a ,  152   b , and  153 . The light receiving section  155   d  used to receive the diverging beams has a color filter  156   e  positioned right in front of a light receiving element  156   f  so as to receive only the diverging beams  152   a ,  152   b , and  153  without influence by the laser light representing the angular data.  
         [0099]    After receiving the signal representing the rotational angular position, the light receiving and sensing device  154   b  computes the rotational angular position based upon its digitized signal. The rotational angular position merely shows a rough value since the digitized signal S 2  is transmitted at certain intervals. Thus, as shown in FIG. 16( b ), a time difference between an instance of reception of the diverging beam  153  and an instance of reception of the reference signal S 1  is utilized to interpolate datum on rotational angular positions at intervals and determine a more accurate angle.  
         [0100]    Three of the diverging beams and the laser light emitted by the angle signal projector  172  do not always have to be received at the same time. Thus, as shown in FIG. 18, alternative configuration may be used to make the rotary laser device emit the diverging beams  152   a ,  152   b , and  153  and the laser light from the angle signal projector  172  in directions varied from one another. In such a case, a time difference between an instance of reception of the diverging beam  153  and an instance of reception of the angular data is utilized to compute an angle. With such a configuration, the diverging beams  152   a ,  152   b , and  153  and the laser light emitted from the angle signal projector  172  may be the same in color (wavelength), and thus, the light receiving section for the diverging beams may also be substituted for the light receiving element for the angular data, or vice versa.  
         [0101]    Moreover, the laser light carrying the angular data must be diverged or converged to cover the entire range at which positional determination can be permitted by using the diverging beams  152   a ,  152   b , and  153 .  
         [0102]    (1.3.4) Light Receiving and Sensing Device Having a Light Receiving Section Capable of Receiving Light in an Omni-directional Manner  
         [0103]    [0103]FIG. 19 shows an embodiment of the light receiving and sensing device  154   c  that is capable of receiving light in an omni-directional manner. As shown in FIG. 19, the omni-directional light receiving and sensing device  154   c  has a supporting rod  180 , a light receiving section  156   g , and a sensor controller  177 . The light receiving section  156   g  is mounted on top of the supporting rod  180  while the sensor controller  177  is attached to a lower portion of the supporting rod. The light receiving section  156   g  has an annular cylindrical Fresnel lens  176 , an annular fiber sheet  175 , and a plurality of light receiving elements  173  disposed in an annular form, and these components are deployed in a concentric form. In addition to that, a light receiving element controller  174  is surrounded by the light receiving elements  173  annularly disposed. As depicted in FIG. 20( a ) and FIG. 20( b ) which is a sectional view of FIG. 20( a ), the sensor controller  177  includes a display  157 , a warning element  161  such as a buzzer, input keys  162 , a memory  165 , a computation unit  166 , an angle signal receiver  179 , and an external communication unit  178 . Furthermore, the sensor controller  177  can be connected to an external computer  179  through the external communication unit  178 . The external computer  179  can be used to process data entry, display of the determination results, and subsequent treatment of the determination results.  
         [0104]    When the light receiving section  156   g  is irradiated with the diverging beams, the laser light is converged toward the light receiving elements  173  the cylindrical Fresnel lens  176  having a directivity toward elevating and depressing directions with the fiber sheet  175  intervening therebetween. The fiber sheet  175  diffuses in horizontal direction the diverging beams converged by the cylindrical Fresnel lens  176 , and hence, the received diverging beams are uniformly incident upon the light receiving elements  173 . With such a configuration, any rays scattered out beyond the directivity of the cylindrical Fresnel lens  176  are not incident upon the light receiving elements  173 , and therefore, an S/N ratio of a reception signal developed by the incident diverging beams. The light receiving elements  173  judges a state of receiving light and breaks a circuit of the light receiving element  173  at which the diverging beams are directed to further enhance the S/N ratio of the incident signal.  
         [0105]    When the light receiving element  173  receives laser light, the light reception signal is sent to the light receiving element controller  174 . The light receiving element controller  174  built in the light receiving section  156   g  sends the light reception signal to the light receiving and sensing controller  177 . Signal processing in the light receiving and sensing controller  177  is similar to that in the light receiving and sensing device  154 .  
         [0106]    (1.4) Operation of the Position Determining System  
         [0107]    (1.4.1) An exemplary operation of the position determining system in combination with the rotary laser device  151  and the light receiving and sensing device  154  will now be described. FIG. 21 is a flow chart of an operational procedure according to which the position determining system produces phantom planes or inclined planes. FIG. 22 is a diagram showing positional relations of the horizontal plane, the inclined planes to be produced, and the coordinate axes. A case is explained in which an inclined plane (2-axially beveled plane) is to be produced so as to cross a reference point C, tilting at angle α in an X-axis direction, and tilting at angle β in a Y-axis direction. The inclined plane has its inclination (bevel angle) maximized when measured in a direction of straight line CD, and the angle is denoted λ.  
         [0108]    At step F 1 , the rotary laser device  151  is placed so that the diverging beams  152   a ,  152   b , and  153  rotate about a vertical axis joining the point C. Then, at step F 2 , a reference direction of the rotary laser device  151  is set up to be identical with a reference direction (X-axis direction herein) of the inclined plane to be produced. The “reference direction” of the rotary laser device  151  is a direction in which the encoder incorporated in the rotary laser device  151  produces an angle of zero degree for a direction of emitted diverging beam. The reference direction of the inclined plane is optionally determined as desired by an operator.  
         [0109]    In an alternative manner of the step F 2 , the rotary laser device  151  is placed in an arbitrary direction while the light receiving and sensing device  154  is placed along an extension in the reference direction of the inclined plane (on the X-axis), so as to determine the rotational angular position of the light receiving and sensing device  154 . Then, the determined angle may be used as an offset angle to numerically subtract it from the angle of laser emission by the rotary laser device  151  to adjust the angle of the diverging beam when the diverging beam is emitted along the X-axis.  
         [0110]    At step F 3 , a desired inclination angle α of the inclined plane to be produced in the reference direction (X-axis direction) and a desired inclination angle β in a direction orthogonal to the reference direction (Y-axis direction) are entered on the input keys  162  in the light receiving and sensing device  154 . The reference point C and the inclination angles α and β thus entered allow the inclined plane to be completely defined. In general, the inclination angle of the inclined plane varies depending upon which direction the inclination angle is determined from the reference point C or an original point. Assuming the inclination angle of the inclined plane is determined in an arbitrary direction such as a direction with which the X-axis meets at an angle φ, the inclination angle γ 0  (elevating or depressing angle) can be computed based upon an equation 3 as follows. 
           γ   0 =tan −1 (tan λ cos(φ−ε))  (3) 
         [0111]    where β≠0 and λ={square root}{square root over (α 2 +β 2 )} 
         [0112]    when α&gt;0 and β.0, ε=tan −1 (β/α),  
         [0113]    when α=0 and β.0, ε=π/2,  
         [0114]    when α&lt;0 and β.0, ε=tan −1 (β/α)+π 
         [0115]    when α&lt;0 and β.0, ε=−tan −1 (β/α)−π 
         [0116]    when α=0 and β.0, ε=−π/2  
         [0117]    when α&gt;0 and β.0, ε=tan 31 (β/α)  
         [0118]    At step F 4 , the angle signal receiver  170  in the light receiving and sensing device  154  receives a signal transmitted from the angle signal transmitter  123  in the rotary laser device  151  to determine which rotational and angular position relative to the reference point C the light receiving and sensing device  154  is positioned. Then, the computing unit  166  of the light receiving and sensing device  154  computes the inclination angle γ 0  of the inclined plane that is determined in a direction corresponding to the obtained rotational angular position. For example, when the light receiving and sensing device  154  is placed in a point A in a rotational angular position making an angle φ relative to the reference point C (the point A is in the horizontal plane), the inclination angle γ 0  of the inclined plane determined in a direction making an angle φ is an angle ∠BCA at which the horizontal plane meets with a straight line joining a point B vertically right above the point A in the inclined plane and the reference point C, and the inclination angle γ 0 , can be obtained based upon the equation 3. The angle φ is referred to as a rotational angular position in this specification.  
         [0119]    At step F 5 , the computation unit  166  of the light receiving and sensing device  154  uses the equation 2 together with the time delays t and t 0  between detections of the three diverging beams  152   a ,  152   b , and  153  emitted by the rotary laser device  151  to compute the elevating or depressing angle γ for the position where the light receiving and sensing device is currently located, and the resultant value is indicated on the display  157 . The rotational angular position φ of the light receiving and sensing device  154  also appears on the display  157 . After that, the elevating or depressing angle γ is compared with the inclination angle γ 0  to compute an angular difference Δγ between them. The light receiving and sensing device  154  may be configured so that the angles such as the elevating or depressing angle γ can be converted and displayed in desired units such as “rad (radian)”, “deg (angle)”, “% (bevel angle)”, and so forth.  
         [0120]    At step F 6 , the display  157  in the light receiving and sensing device  154  indicates, on the basis of the angle Δγ computed at the step F 5 , the simulation results on which way the light receiving and sensing device  154  must be moved upward or downward to be in a closer position to the desired inclined plane. An operator or user moves the light receiving and sensing device  154  upward or downward, referring to the indication on the display  157 . A displacement of the light receiving and sensing device  154  can be read with the index  163  and the level rod  159  attached in the light receiving and sensing device. Alternatively, the displacement may be read by a level rod scale reader  167  to send the reading results to the computing unit  166 .  
         [0121]    Procedures in the steps F 4  and F 6  are automatically repeated till the light receiving and sensing device  154  is placed on the inclined planes to be produced. Preferably, the light receiving and sensing device  154  has the buzzer  161  that rings when the light receiving and sensing device is located on the desired inclined plane to be produced.  
         [0122]    (1.4.2) Other functional features of the position determining system will be described. The above-mentioned operation is attained by the operator&#39;s setting the desired inclined plane and then by using the position determining system according to the present invention to produce the inclined plane. In contrast, one of functional feature described hereinafter uses the position determining system according to the present invention to determine an inclination angle an arbitrary position where the light receiving and sending device  154  is located. Specifically, the rotary laser device  151  is placed in the reference point C, and the light receiving and sensing device  154  is located in a position that is to be determined. Then, the rotary laser device  151  is actuated to emit the diverging beams  152   a ,  152   b , and  153  so that the light receiving and sensing device  154  receives the diverging beams, and thus, an elevating or depressing angle can be determined as to a position where the light receiving and sensing device  154  is located.  
         [0123]    As desired, an inclined plane can be automatically produced where a straight line joining the reference point C and the light receiving and sensing device  154  arbitrarily located makes a maximum inclination angle. Specifically, referring to FIG. 22, the rotary laser device  151  is placed so that the reference direction is superposed with the X-axis, and thereafter, the light receiving and sensing device  154  is placed at an arbitrary point D. The rotary laser device  151  is actuated to determine an elevating or depressing angle λ at the point D. The computation unit  166  of the light receiving and sensing device  154  computes inclination angles α and β in the X- and Y-axis directions of the inclined plane that has a maximum inclination angle identical with a straight line CD. The computation results of the inclined angles α and β are indicated on the display  157  in the light receiving and sensing device  154  to determine an inclined plane defined by the inclination angles α and β. Thus, the inclined plane determined in this way can be produced in an arbitrary position. The light receiving and sensing device  154  may have a buzzer that rings when the light receiving and sensing device is located on the inclined plane.  
         [0124]    In an alternative embodiment of the position determining system according to the present invention, a single unit of the rotary laser device  151  may be combined with a plurality of the light receiving and sensing devices  154  to independently use each light receiving and sensing device  154 . In the prior art inclined plane determining system, two of the rotary laser devices are necessary to produce two types of different inclined planes, and there arises a problem that laser beams emitted respectively by the rotary laser devices interfere with each other to cause malfunction. However, in the alternative embodiment of the position determining system according to the present invention, the plurality of the light receiving and sensing devices  154  can work on the single rotary laser device  151 , and the resultant inclined planes are different from one another and respectively unique to those light receiving and sensing devices  154 .  
         [0125]    With such an improvement, when the light receiving and sensing devices  154  are attached to construction machines to level the ground, a plurality of the construction machines can simultaneously work cooperative with only one rotary laser device  151 , and moreover, the construction machines can respectively dedicate themselves for inclined surfaces varied one from another. When the inclined plane determined according to the procedure as mentioned above is to be altered, such predetermined settings can be varied for each light receiving and sensing device. Therefore, there is no need of interrupting an operation of the rotary laser device for setting change, and also there is no need of interrupting an operation of any light receiving and sensing device that undergoes no setting change.  
         [0126]    (2) Other Preferred Embodiments  
         [0127]    (2.1) Other Embodiments of the Diverging Beams  
         [0128]    Although the embodiments as mentioned above is configured so that the rotary laser device  151  emits three of the diverging laser beams  152   a ,  152   b , and  153  together making a generally N-shaped irradiation pattern as shown in FIG. 2, the number of the emitted laser beams may be more or less than three, and the irradiation pattern of the laser beams may be varied as desired. Examples of the irradiation pattern of the diverging laser beams are shown in FIGS.  23 ( a ) to  23 ( r ). These patterns of the diverging laser beams can be easily implemented by appropriately changing the diffraction grating in FIG. 5.  
         [0129]    As with the irradiation patterns of the diverging laser beams as shown in FIGS.  23 ( g ) to  23 ( p ), the light receiving section  156  of the light receiving and sensing device  154  detects the diverging laser beams three times for a duration of one revolving movement of the rotary laser device  151 . Thus, the elevating or depressing angle γ can be computed in a similar manner as in the aforementioned embodiment 1.  
         [0130]    As to the irradiation patterns of the diverging laser beams as shown in FIGS.  23 ( q ) to  23 ( r ), the diverging laser beams are detected four times for a duration of one revolving movement of the rotary laser device  151 . Thus, arbitrarily selecting three out of the detected four diverging beams and computing to obtain the elevating or depressing angle γ permits 4 variations of γ to be produced. Averaging these results of the elevating or depressing angle permits the elevating or depressing angle γ to be determined with enhanced accuracy. The number of the diverging laser beams may be increased to increase the number of samples subjected to the averaging, in order to further enhance the determination accuracy.  
         [0131]    As for the irradiation patterns of the diverging laser beams as shown in FIGS.  23 ( a ) to  23 ( f ), the diverging laser beams are detected only twice for a duration of one revolving motion of the rotary laser device  151 , and therefore, the elevating or depressing angle γ cannot be computed in the above-mentioned way. For example, employing the irradiation pattern of the diverging laser beams in FIG. 23( b ), the elevating or depressing angle γ can be computed by using an equation 4 as follows.  
             γ   =         (     t   -     t   0       )                   π                 tan                   (   ξ   )       T             (   4   )                               
 
         [0132]    where T is a rotation cycle of the rotary laser device, ξ is an inclination angle of the diverging laser beams relative to the horizontal plane, t p  is a time delay between receptions of the diverging laser beams when the light receiving and sensing device  154  is placed on the horizontal plane, and t is a time delay between receptions of the diverging laser beams when the light receiving and sensing device  154  is located in a position of the determination.  
         [0133]    Since an equation 4 contains a term of the rotation cycle T of the rotary laser device, irregularity of the rotations by the diverging laser beams influence the accuracy at which the elevating or depressing angle γ is determined. In these embodiments, for the motor that causes the diverging laser beams to rotate, a motor of high revolution accuracy such as a spindle motor is preferably used. On the contrary, since the equation 2 has no term of the rotation cycle T, the determination accuracy is not varied unless irregularity of the rotations by the diverging laser beams exists during a short period of time from a reception of the diverging beam  152   a  to a reception of the diverging beam  152   b . Thus, it is recognized that there is a reduced influence of errors caused by such irregularity of the beam rotations in the embodiment where the diverging beams are detected three times during one revolution of the rotary laser device  151 , compared with the embodiment where the diverging beams are detected twice for the same duration.  
         [0134]    The diverging laser beams of the patterns in FIGS.  23 ( c ),  23 ( d ),  23 ( j ), and  23 ( k ) assume a moderate inclination in the vicinity of the horizontal plane while assuming a sharp inclination in a section apart from the horizontal plane, and hence, a rate of a variation in the elevating or depressing angle γ to a variation in the time delay between the light receptions varies from a section close to the horizontal plane to a section apart from the horizontal plane. In this way, a sensitivity in determining the elevating or depressing angle in the vicinity of the horizontal plane can be enhanced.  
         [0135]    (2.2) Other Uses of the Light Receiving and Sensing Device  
         [0136]    As has been described, the light receiving and sensing device used in the preferred embodiments of the position determining system according to the present invention may be combined with not only a rotary laser device but also any other laser beam emitting device.  
         [0137]    The present invention can be applied in various manners as mentioned below.  
         [0138]    [1] An alternative embodiment of the position determining system includes  
         [0139]    a first device having a means for transmitting data on vertical angles and a means for transmitting data on rotational angular positions, and  
         [0140]    a second device having a means for determining inclined planes, a means for determining the vertical angles from the data transmitted from the first device, and a means for displaying an angular difference between the vertical angles determined by the vertical angle determining means and the elevation- and depression-angles of the inclined planes determined by the inclined planes determining means.  
         [0141]    [2] In the position determining system as defined in [1], the first device is a rotary laser device that includes a means for determining rotational angular positions, and a means for transmitting the rotational angular positions determined by the determining means, where the rotary laser device emits at least two diverging beams of laser light having divergence within planes other than the horizontal plane while rotating the diverging laser beams about a predetermined axis,  
         [0142]    the second device has a means for receiving the rotational angular positions transmitted by the rotational angular position transmitting means, and a means for receiving the diverging laser beams, and  
         [0143]    at leas one of inclination angles of the diverging laser beams is different from the remaining inclination angles of the diverging laser beams, the light receiving and sensing device determines the vertical angles of the light receiving and sensing device relative to the rotary laser device based upon a state of light receptions in the light receiving section that has received the diverging laser beam, and the light receiving and sensing device determines the rotational angular positions of the light receiving and sensing device relative to the rotary laser device based upon the rotational angular positions received from the rotary laser device.  
         [0144]    [3] In the position determining system as defined in [2], the light receiving and sensing device further has a function to determine inclined planes to be produced,  
         [0145]    the light receiving and sensing device displays a deviation of its location from the inclined plane, and/or, the light receiving and sensing device gives a warning display to announce that the light receiving and sensing device is placed on the inclined plane.  
         [0146]    [4] In the position determining system as defined in [2] or [3], the means for determining the rotational angular position is an encoder.  
         [0147]    [5] In the position determining system as defined in any one of [2] to [4], the means for transmitting the rotational angular positions is light or laser light.  
         [0148]    [6] In the position determining system as defined in any one of [2] to [4], the means for transmitting the rotational angular positions is wave.  
         [0149]    [7] In the position determining system as defined in [5], both the diverging beams of laser light and the light or laser light carrying data on the rotational angular positions are received at the same light receiving section in the light receiving and sensing device.  
         [0150]    [8] In the position determining system as defined in any one of [2] to [7], the light receiving section in the light receiving and sensing device is provided with a compressing or converging means.  
         [0151]    [9] In the position determining system as defined in [8], the compressing or converging means is a lens.  
         [0152]    [10] In the position determining system as defined in any one of [2] to [9], the rotational laser device emits three diverging beams of laser light in an N-shaped irradiation pattern.  
         [0153]    [11] In the position determining system as defined in any one of [2] to [9], the light receiving section in the light receiving and sensing device detects the diverging laser beams three times or more for a duration of one revolving motion of the rotary laser device.  
         [0154]    [12] A light receiving and sensing device includes a means for receiving data on rotational angular positions transmitted from a rotary laser device, and a light receiving section receiving diverging beams of laser light emitted by the rotary laser device,  
         [0155]    the rotary laser device determines vertical angles relative to the rotary laser device based upon a sate of light receptions at the light receiving section that has received the diverging laser beams.  
         [0156]    [13] In the light receiving and sensing device as defined in [12] that further functions to determine inclined planes to be produced,  
         [0157]    the light receiving and sensing device displays a deviation of its location from the inclined plane, and/or, the light receiving and sensing device gives a warning display to announce that the light receiving and sensing device is placed on the inclined plane.  
         [0158]    [14] In the light receiving and sensing device as defined in [12] or [13], both the diverging beams of laser light and the light carrying data on the rotational angular positions are received at the same light receiving section.  
         [0159]    [15] In the light receiving and sensing device as defined in any one of [12] to [14], the light receiving section is provided with a condensing or converging means.  
         [0160]    [16] In the light receiving and sensing device as defined in [15], the condensing or converging means is a lens.  
         [0161]    Although the preferred embodiments of the present invention have been described, the disclosure can be modified in various manners without departing from the true range and spirit of the invention and without departing from equivalent technical forms as defined only in the appended claims.