Three-dimensional model generating device

An example three-dimensional model generating device includes an emitting unit that emits a laser light and a first deflector that deflects laser light, whose emission direction rotates in a first rotation range, within a first scan plane. A second deflector deflects laser light, whose emission direction rotates in a second rotation range, within a second scan plane intersecting with the first scan plane. The detector detects a reflected light when laser light deflected from the first deflector is reflected from the target object or detects a reflected light when laser light deflected from the second deflector is reflected from the target object. The measuring unit measures a distance to the target object on the basis of the time taken since emission of the laser light to detection of the reflected light. The generating unit generates a three-dimensional model of the target object by using the measurement result.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2012-249859, filed on Nov. 14, 2012; the entire contents of which are incorporated herein by reference.

FIELD

An embodiment described herein relates generally to a three-dimensional model generating device.

BACKGROUND

Conventionally, a technology is known for generating a three-dimensional model by measuring the three-dimensional shape of a target object. For example, it is possible to think of a method in which a target object is placed in the center of the measurement direction (the observation direction) of a laser radar device that is capable of measuring the distance to the target object; measurement is performed by moving the laser radar device along the outer circumferential direction of the target object; and the three-dimensional shape of the target object is generated on the basis of the measurement result.

In order to obtain an accurate three-dimensional model, it is particularly important to eliminate omissions in the measurement. However, in a typical laser radar device, the laser light is deflected in a plurality of scan planes having different heights. Hence, if a target object is so thin that it is able to fit within the clearance gaps between adjacent scan planes, then that target object is not detectable by a typical laser radar device. Moreover, since the clearance gaps widen along with an increase in the distance to the target object, the number of undetectable objects also goes on increasing. Thus, in the conventional technology, that leads to omissions in the measurement of the target object for which a three-dimensional model is to be generated. For that reason, it is not possible to obtain an accurate three-dimensional  model.

DETAILED DESCRIPTION

According to an embodiment, a three-dimensional model generating device includes an emitting unit, a first deflector, a second deflector, a detector, a measuring unit, and a generating unit. The emitting unit emits a laser light in such a way that an emission direction of the laser light rotates around a predetermined axis. The first deflector deflects at least a part of the laser light, whose emission direction rotates in a first rotation range, within a first scan plane. The second deflector deflects at least a part of the laser light, whose emission direction rotates in a second rotation range, within a second scan plane that intersects with the first scan plane. The detector detects a reflected light when the laser light that has deflected from the first deflector is reflected from a target object or detect a reflected light when the laser light that has deflected from the second deflector is reflected from the target object. The measuring unit measures a distance to the target object on the basis of the amount of time taken since emission of the laser light up to detection of the reflected light. The generating unit generates a three-dimensional model of the target object by using a measurement result obtained by the measuring unit.

An exemplary embodiment of a three-dimensional model generating device will be described below with reference to the accompanying drawings. Herein, a three-dimensional model points to the data that enables expressing the shape of a three-dimensional object.FIG. 1is a diagram illustrating an overall configuration example of a three-dimensional model generating device1according to the embodiment. As illustrated inFIG. 1, the three-dimensional model generating device1includes a laser radar unit10, a first deflecting unit20, a second deflecting unit30, and a generating unit40.

The laser radar unit10emits a laser light such that the emission direction of the laser light rotates around a predetermined axis (in the example illustrated inFIG. 1, rotates around a light axis ax).FIG. 2is a diagram illustrating a specific configuration example of the laser radar unit10. As illustrated inFIG. 2, the laser radar unit10includes a laser light generating unit11, a lens12, a mirror13, a deflection plate14, a collecting lens15, a detecting unit16, and a control unit17. Herein, the laser radar unit10has the function of detecting the distance to or the direction toward a target object for which a three-dimensional model is to be generated.

The laser light generating unit11is configured with, for example, laser diodes. Under the control of the control unit17, the laser light generating unit11receives the supply of a pulse current from a driver circuit (not illustrated) and projects a pulsed laser light.

The lens12is disposed on the light path of the laser light that is projected by the laser light generating unit11. The lens12is configured as a collimated lens; and has the function of converting the laser light, which is projected by the laser light generating unit11, into a parallel light.

The mirror13is disposed on the light path of the laser light that has passed through the lens12. Herein, the mirror13is positioned in such a way that the laser light that has passed through the lens12is reflected toward the deflection plate14.

The deflection plate14is configured to be rotatable around the light axis ax, and is disposed on the light path of the laser light that has reflected from the mirror13. Moreover, the deflection plate14has the function of deflecting (reflecting) the laser light, which has reflected from the mirror13, toward the space in which a target object is present; as well as has the function of deflecting (reflecting) the reflected light from the target object toward the detecting unit16.

In the example illustrated inFIG. 2, the deflecting plate14is placed in such a way that the direction of the laser light that has reflected from the mirror13makes an angle of 45° with the normal of a reflecting surface14aof the deflection plate14. Moreover, the deflection plate14rotates around the light axis ax at which the laser light reflected from the mirror13is coincident in direction with the axis direction of the deflection plate14. Hence, irrespective of the rotational position of the deflection plate14, the laser light reflected from the mirror13is always maintained at an angle of incidence of 45°. As a result, the travelling direction of the laser light that has reflected from the deflection plate14is always orthogonal to the light axis ax.

By implementing the configuration described above, it becomes possible to enable emission of a laser light with the emission direction of the laser light rotating around the light axis ax. Meanwhile, under the control of the control unit17, the deflection plate14rotates when driven by a motor (not illustrated). Moreover, the reflecting surface14aof the deflection plate14is configured to be sufficiently larger in size than the size of the area on the mirror13from which the laser light is reflected. Meanwhile, in the example illustrated inFIG. 2, each of the laser light generating unit11, the lens12, the mirror13, the deflection plate14, and the control unit17can be regarded to correspond to an “emitting unit” mentioned in claims.

The collecting lens 15 is disposed on the light path of the reflected light between the deflection plate14to the detecting unit16. The collecting lens15collects the reflected light from the deflection plate14and guides the collected light to the detecting unit16.

The detecting unit16detects the laser light (the reflected light) that has reflected from the target object. The detecting unit16is configured with, for example, photodiodes that detect the reflected light from the target object and convert it into electric signals.

The control unit17has the function of measuring the distance to the target object by measuring the amount of time taken since the output of the laser light by the laser light generating unit11up to the detection of the reflected light by the detecting unit16. Meanwhile, in this example, the control unit17corresponds to a “measuring unit” mentioned in claims.

Returning to the explanation with reference toFIG. 1, the first deflecting unit20deflects at least a part of the laser light, which has been emitted by the laser radar unit10and whose emission direction rotates in a first rotation range, within a first scan plane P1. In the example illustrated inFIG. 1, the first deflecting unit20is configured with a flat reflecting material (such as a mirror or a prism). Herein, the explanation is given for an example in which the first deflecting unit20is configured with a mirror. In the embodiment, of the top surface (the reflecting surface) of the first deflecting unit20, such a position is set as the origin at which falls the laser light present at the center of the first rotation range; and a coordinate system is set in which the travelling direction of the laser light that has deflected from the first deflecting unit20serves as the Z-axis, the vertical upward direction serves as the Y-axis, and the horizontal direction orthogonal to the Z-axis serves as the X-axis. However, that is not the only possible case, and the coordinate system can be set by implementing an arbitrary method. Given below is the concrete explanation of the first deflecting unit20.

In the example illustrated inFIG. 1, the first deflecting unit20is disposed in such a way that the laser light in the first rotation range sequentially falls along a line that passes transversely across the top surface of the first deflecting unit20, and in such a way that the plane that includes a collection of laser light emitted with the emission direction thereof rotating around the light axis ax (i.e., a rotating plane of the laser light) makes an angle of 45° with the normal of the top surface of the first deflecting unit20.

FIG. 3is a schematic diagram (a schematic diagram in the YZ plane) illustrating a case when the laser radar unit10and the first deflecting unit20are viewed from the X-axis direction. As can be understood fromFIG. 3, the first deflecting unit20is disposed in such a way that the rotating plane of the laser light makes an angle (an angle of incidence) of 45° with the normal of the top surface of the first deflecting unit20. With that, the angle of reflection becomes equal to 45°, and the laser light reflected from the top surface of the first deflecting unit20travels in a direction perpendicular to the incident direction. That is, the first scan plane P1, which indicates the area in which the laser light travels after being deflected from the first deflecting unit20, becomes an orthogonal plane to the rotating plane. However, the first scan plane P1is not limited to this particular form.

Returning to the explanation with reference toFIG. 1, the second deflecting unit30deflects at least a part of the laser light, which has been emitted by the laser radar unit10and whose emission direction rotates in a second rotation range, within a second scan plane P2that intersects with the first scan plane P1(in the example illustrated inFIG. 1, intersects at an angle Φ). The second deflecting unit30is configured with a reflecting material such as a mirror or a prism. Herein, the explanation is given for an example in which the second deflecting unit30is configured with a mirror. Given below is the concrete explanation of the second deflecting unit30.

In the embodiment, the second deflecting unit30has a twisted shape obtained by twisting a flat reflecting material. As illustrated inFIG. 4, the second deflecting unit30is formed by twisting a flat reflecting material.FIG. 5is a front view of the second deflecting unit30. In the example illustrated inFIG. 5, such a position on the top surface (the reflecting surface) of the second deflecting unit30at which the normal direction does not change upon being twisted is set as the reference position (the origin); while the torsion axis direction is set as the x-axis, the direction orthogonal to the torsion axis direction is set as the y-axis, and the depth direction of the top surface is set as the z-axis. InFIG. 5, “Q” represents an area along the torsion axis.FIG. 6is an xz planar view when the second deflecting unit30is viewed down from above.FIG. 7is a yz planar view when the second deflecting unit30is viewed from a side. The angle Φ illustrated inFIG. 7corresponds to the torsional angle of the second deflecting unit30.

In this example, it is assumed that the original flat reflecting material from which the second deflecting unit30is formed (i.e., a non-twisted flat reflecting material) is present on the xy plane, and that the horizontal width (i.e., the width in the x direction of the flat reflecting material) is 2W (x=[−W, W]) and the longitudinal width (the width in the y direction of the flat reflecting material) is 2H (y=[−H, H]). Moreover, when the original reflecting material is twisted, it is assumed that the ends of the mirror rotate by the angle Φ with respect to the y-axis (thus, the torsional angle=Φ). Then, the coordinates of the upper end and the coordinates of the lower end at a position x of the twisted mirror surface can be expressed using Expression (1) given below.

Consequently, the surface shape of the second deflecting unit30according to the embodiment can be expressed using Expression (2) given below.

In Expression (2), “t” represents a parameter equal to or greater than zero and equal to or smaller than one.

Herein, of the top surface of the reflecting material from which the second deflecting unit30is formed, all normal directions of the area along the x-axis (the torsion axis) are coincident with the z-axis direction. However, when the second deflecting unit30is formed by twisting the flat reflecting material in the abovementioned manner; then, of the top surface of the second deflecting unit30, the normal direction of the area Q along the torsion axis keeps changing in a continuous manner (the normal direction only at the reference position is coincident with the z-axis direction). Consequently, for example, of the top surface of the second deflecting unit30, if the laser light in the second rotation range sequentially falls on the area Q along the torsion axis; then, due to the fact that the normal direction of the area Q keeps changing in a continuous manner, the angle formed between the incident direction of the laser light and the normal direction of the area Q (i.e., the angle of incidence) also changes in a continuous manner (that is, the angle of reflection also changes in a continuous manner). As a result, the second scan plane P2, which indicates the area in which spreads the laser light that has deflected from the second deflecting unit30, has a gradient equal to the torsional angle Φ.

In the embodiment, as illustrated inFIG. 8, the second deflecting unit30is disposed in such a way that the first scan plane P1and the second scan plane P2intersect at the angle Φ (=the torsional angle Φ). As a result, it becomes possible to reliably prevent a situation in which the laser light does not fall on the target object present in the Z-axis direction thereby causing omissions in the measurement.FIG. 8is a diagram illustrating a scan area of the laser light in the XY plane at a distance Z=L. Herein, it is desirable that the position of intersection between the first scan plane P1and the second scan plane P2is in the vicinity of the center of the first scan plane P1. However, that is not the only possible case. Alternatively, the first scan plane P1and the second scan plane P2can intersect at a position other than the centers or can intersect at different positions. With reference to the example illustrated inFIG. 8, the first deflecting unit20and the second deflecting unit30are disposed in such a way that the area to which the laser light deflected from the reference position of the second deflecting unit30travels corresponds to the point of intersection between the first scan plane P1and the second scan plane P2.

FIG. 9is a schematic diagram illustrating a case when the laser radar unit10and the second deflecting unit30are viewed from the X-axis direction. As can be understood fromFIG. 9, the second deflecting unit30is disposed in such a way that the laser light in the second rotation range sequentially falls on the area along the torsion axis on the top surface (the reflecting surface) of the second deflecting unit30.

FIG. 10is a schematic diagram illustrating a case when the laser radar unit10, the first deflecting unit20, and the second deflecting unit30are viewed from the Z-axis direction (i.e., a schematic diagram illustrating an anterior top view). In the example illustrated inFIG. 10, the laser light is emitted while being rotated in the clockwise direction starting from the position corresponding to 3 o'clock (in the example illustrated inFIG. 10, the position corresponding to the angle of rotation of 0°) toward the position corresponding to 9 o'clock (in the example illustrated inFIG. 10, the position corresponding to the angle of rotation of 180°). In the example illustrated inFIG. 10, the range between the position corresponding to 4:30 (the position corresponding to the angle of rotation of 45°) and the position corresponding to 7:30 (the position corresponding to the angle of rotation of 135°) is set as the first rotation range; while the range between the position corresponding to 3 o'clock and the position corresponding to 4:30 is set as the second rotation range. However, that is not the only possible case. As described above, the laser light in the first rotation range is deflected from the first deflecting unit20. Then, the laser light that has deflected from the first deflecting unit20spreads within the first scan plane P1. Similarly, the laser light in the second rotation range is deflected from the second deflecting unit30. Then, the laser light that has deflected from the second deflecting unit30spreads within the second scan plane P2that intersects with the first scan plane P1.

Returning to the explanation with reference toFIG. 1, the generating unit40refers to the measurement result obtained by the laser radar unit10(the control unit17) and generates a three-dimensional model of the target object. A more concrete explanation is given below. Herein, for the sake of simplicity in the explanation, the constituent elements other than the generating unit40(i.e., the laser radar unit10, the first deflecting unit20, and the second deflecting unit30) in the three-dimensional model generating device1are collectively referred to as a “distance measuring device”. In the embodiment, as illustrated inFIG. 11, the target object is placed in the center of the measurement direction in which the distance measuring device performs measurement (i.e., the target object is placed in the center of the travelling direction of the laser light used for scanning), and performs measurement while moving the distance measuring device along the outer circumferential direction of the target object. InFIG. 11, each black circle represents a position of the distance measuring device at a particular timing. Then, the generating unit40uses the measurement results to generate a three-dimensional model of the target object. In this example, every time the distance measuring device performs measurement at a particular timing, the generating unit40obtains a data group indicating the measurement result.

Herein, Dt0 represents a data group that is obtained at a timing t0 while the laser light rotates one revolution. Thus, Dt0 points to the positional coordinates of the target object in the coordinate system in which the position of the distance measuring device at the timing t0 serves as the origin. Herein, a change in the position and the angle of the distance measuring device leads to a change in the coordinate system of the distance measuring device. For that reason, a data group Dt1, which is obtained at a timing t1 at which the next measurement is performed, cannot be treated as the data of the same coordinate system as the coordinate system of the data group Dt0.

In that regard, if the variation in the positions of the distance measuring device or the rotations of the distance measuring device at the timings t0 and t1 is calculated and if the data group Dt1 is converted into the coordinate system of the data group Dt0, then the two data groups can be treated to be of the same coordinate system. The variation in the positions or the rotations of the distance measuring device can be calculated by attaching a gyroscopic instrument or a global positioning system (GPS) to the distance measuring device. Alternatively, a camera can be installed in the distance measuring device, and the variation in the positions or the rotations of the distance measuring device can be calculated by comparing the images captured by the camera at two different timings. Still alternatively, the variation of the distance measuring device can be observed from outside using a sensor such as a camera. Meanwhile, the coordinate system conversion can be achieved by performing a commonly-known correction of rotation or translation. The generating unit40converts the coordinate systems of all data groups, which are obtained at a plurality of timings, into the coordinate system of a reference timing, thereby generating a three-dimensional model of the target object.

Herein, in the embodiment, as illustrated inFIG. 8, in the vicinity of the point of intersection between the first scan plane P1and the second scan plane P2, during a single measurement (during the measurement performed while the laser light rotates one revolution), the same place is measured for a plurality of times. At that time, if a plurality of pieces of data is used to limit the effect of a measuring error, then it becomes possible to enhance the measuring accuracy in the vicinity of the point of intersection.

In the embodiment, the control unit17of the laser radar unit10measures the distance to the target object, which is present at the point of intersection, on the basis of the following two pieces of data: a first piece of data that indicates the distance to the target object present at the point of intersection, which is obtained based on the amount of time taken since the emission of the laser light that, of the laser light in the first rotation range, is projected on the point of intersection between the first scan plane P1and the second scan plane P2up to the detection of the reflected light; and a second piece of data that indicates the distance to the target object present at the point of intersection, which is obtained based on the amount of time taken since the emission of the laser light that, of the laser light in the second rotation range, is projected on the point of intersection between the first scan plane P1and the second scan plane P2up to the detection of the reflected light.

Then, an arbitrary method can be implemented to obtain final data (i.e., data that indicates the distance to the target object which is present at the point of intersection) based on the first piece of data and the second piece of data. For example, the average value of the first piece of data and the second piece of data can be obtained as the final data. Alternatively, a weighted average value can be obtained as the final data. Still alternatively, for example, the first piece of data can be selected as the final data, or the second piece of data can be selected as the final data. Still alternatively, for example, from among the first piece of data and the second piece of data, the data obtained at the earlier timing (calculated at the earlier timing) can be selected as the final data. Alternatively, in contrast, from among the first piece of data and the second piece of data, the data obtained at the later timing can be selected as the final data. However, these are not the only possible methods of obtaining the final data based on the first piece of data and the second piece of data.

As described above, in the embodiment, the first deflecting unit20is disposed that deflects the laser light, whose emission direction rotates in the first rotation range, within the first scan plane P1, and the second deflecting unit30is disposed that deflects the laser light, whose emission direction rotates in the second rotation range, within the second scan plane P2which intersects with the first scan plane P1. As a result, whatever may be the thickness of the target object that is present in the vicinity of the point of intersection between the first scan plane P1and the second scan plane P2, that target object is reliably detected (measured) using the laser light spreading in either one of the two scan planes (seeFIG. 12). Hence, according to the embodiment, it becomes possible to reliably prevent omissions in the measurement of the target object. That enables obtaining an accurate three-dimensional model.

In the embodiment, the explanation is given for an example in which only a single second deflecting unit30is disposed. However, that is not the only possible case. Alternatively, for example, it is possible to dispose a plurality of second deflecting units30. For example, two second deflecting units30can be symmetrically positioned across the first deflecting unit20. With that, as illustrated inFIG. 13, each of the two second deflecting units30intersects with the first scan plane P1at the angle Φ. As a result, two different second scan planes P2are formed that have the same absolute value of the gradient but with opposite signs.

Alternatively, for example, as illustrated inFIG. 14, a plurality of second deflecting units30having different torsional angles can be disposed in such a way that each second deflecting unit30makes a different intersection angle with the first scan plane P1. Still alternatively, it is also possible to combine the configuration illustrated inFIG. 13and the configuration illustrated inFIG. 14. In this way, by increasing the number of second scan planes P2that intersect with the first scan plane P1, omissions in the measurement of the target object can be prevented in a more reliable manner.

Meanwhile, the invention can also be applied to a distance measuring device (i.e., in the example described above, the constituent elements other than the generating unit40in the three-dimensional model generating device1) that measures the distance to the target object. Such a distance measuring device can include an emitting unit, a first deflector, a second deflector, a detector, and a measuring unit. The emitting unit has the function of emitting a laser light in such a way that an emission direction of the laser light rotates around a predetermined axis. The first deflector has the function of deflecting the laser light, whose emission direction rotates in a first rotation range, within a first scan plane. The second deflector has the function of deflecting the laser light, whose emission direction rotates in a second rotation range, within a second scan plane that intersects with the first scan plane. The detector has the function of detecting the reflected light when the laser light that has deflected from the first deflector is reflected from the target object or detecting the reflected light when the laser light that has deflected from the second deflector is reflected from the target object. The measuring unit has the function of measuring the distance to the target object on the basis of the amount of time taken since the emission of the laser light up to the detection of the reflected light.