Abstract:
A distance measuring device is provided. The distance measuring device includes: a distance sensing unit, for sensing a distance value of a target object; a drive unit, for driving the distance sensing unit to rotate according to a rotation angle; and a compensation unit, for providing a compensation value according to the rotation angle and obtaining an actual distance according to the compensation value and the distance value.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This non-provisional application claims priority under 35 U.S.C.§119(a) on Patent Application No. 98134280 filed in Taiwan, R.O.C. on 2009/10/9, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a measuring device, and more particularly to a distance measuring device. 
     2. Related Art 
     With the development of electronic technology, the laser ranging method has been widely applied in distance measurement. For example, a laser rangefinder is applied in construction, traffic management, topographical reconnaissance, indoor decoration, and other areas. The laser rangefinder is equipped with a laser beam emitter for emitting a laser beam to a target object, and a laser light receiver for receiving a signal reflected from the target object, such that the distance is measured according to the time taken for the light wave to be emitted from the laser beam emitter and received by the laser light receiver. 
       FIG. 1  shows a conventional two-dimensional laser rangefinder A 1 , which is mainly formed by a laser beam emitter A 11  and a revolving mechanism A 12 . The laser rangefinder A 1  adds a back and forth scanning angle in a horizontal direction to a laser beam emitted by the laser beam emitter A 11  through the revolving mechanism A 12 , such that the laser rangefinder A 1  can be used in a robot to achieve functions such as obstacle sensing and environment recognition. Furthermore, if a back and forth scanning angle in a vertical direction in addition to that in the horizontal direction is added, the laser rangefinder becomes a three-dimensional laser rangefinder, and the sensing range thereof becomes three-dimensional, too. As compared with the two-dimensional laser which only scans a planar range, the three-dimensional laser can scan a three-dimensional space. For example, objects such as chairs and tables having different heights and depths can be detected. 
     The price of three-dimensional rangefinders available in the market is very high, typically ten times higher than that of two-dimensional laser rangefinders for scanning a plane, such that three-dimensional rangefinders cannot be applied widely to various fields. Therefore, simplifying the structure of the three-dimensional rangefinder so as to overcome the problem of the excessively high cost of the conventional three-dimensional laser rangefinder such that it can be widely applied in fields such as environment recognition, environment construction, obstacle detection, and positioning of a robot, is a problem urgently requiring a solution. 
     SUMMARY 
     Accordingly, the present invention is directed to a distance measuring device, which includes: a distance sensing unit, for sensing a distance value of a target object; a drive unit, for driving the distance sensing unit to rotate according to a rotation angle; and a compensation unit, for providing a compensation value according to the rotation angle and obtaining an actual distance according to the compensation value and the distance value. 
     Based on the above, the present invention further includes a revolving unit for driving the distance sensing unit to revolve. A rotation direction of the drive unit may be substantially perpendicular to a revolving direction of the revolving unit. 
     In addition, the drive unit of the present invention may preferably include: a seat, for disposing the distance sensing unit; a gear, located on a side edge of the seat; a rack, engaged with the gear; and a cam, revolving to drive the rack to displace reciprocally and driving the gear to rotate by the rack, so as to drive the seat to rotate. 
     The present invention has the effect of using a reciprocating mechanism having a low cost to drive a distance sensing unit to move, so as to add another dimension thereto. For example, an original one-dimensional distance sensing unit achieves the measuring effect of a two-dimensional distance sensing unit by means of the reciprocating mechanism, or an original two-dimensional distance sensing unit achieves the measuring effect of a three-dimensional distance sensing unit by means of the reciprocating mechanism. Since the present invention can solve the problem of an excessively high cost of a conventional three-dimensional laser rangefinder, it can be widely applied in fields such as environment recognition, environment construction, obstacle detection, and the positioning of a robot. 
     The detailed features and advantages of the present invention are described in detail through the embodiments below, and the content of the detailed description is sufficient for those skilled in the art to understand the technical content of the present invention and to implement the present invention there accordingly. Based upon the content of the specification, the claims, and the drawings, those skilled in the art can easily understand the relevant objectives and advantages of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description, which is provided below only for the purpose of illustration, and thus not limitative of the present invention, wherein: 
         FIG. 1  is a schematic outside view of a conventional two-dimensional laser rangefinder; 
         FIG. 2  is a schematic outside view of the present invention; 
         FIG. 3  is a first schematic operation view of the present invention; 
         FIG. 4  is a second schematic operation view of the present invention; and 
         FIG. 5  is a third schematic operation view of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 2  shows a distance measuring device in the present invention. 
     The distance measuring device  1  in the present invention includes a distance sensing unit  10 , a drive unit  20 , and a compensation unit  40 . 
     The distance sensing unit  10  is used for sensing a distance value of a target object (not shown). The distance sensing unit  10  mainly includes an emitter  11  and a receiver  12 . The emitter  11  is used for emitting a distance measuring signal, and the receiver  12  is used for receiving the distance measuring signal reflected by the target object. A distance value between the distance sensing unit  10  and the target object is obtained by the time taken for the distance measuring signal emitted from the emitter  11  and received by the receiver  12 . In this embodiment the emitter  11  may preferably be a laser emitter having a laser diode for emitting laser light as the distance measuring signal, but the present invention is not limited thereto. The emitter  11  may also be an infrared emitter for emitting infrared rays as the distance measuring signal or an ultrasonic emitter for emitting an ultrasonic wave as the distance measuring signal. Alternatively, the distance measurement is performed using other light waves or sound waves. 
     The drive unit  30  is used for driving the distance sensing unit  10  to rotate according to a rotation angle. Herein, the drive unit  30  may be a reciprocating mechanism including a seat  31 , a gear  32 , a rack  33 , and a cam  34 . The seat  31  is used for disposing the distance sensing unit  10 . The gear  32  is disposed at the seat  31  so that the seat  31  can be rotated along with the gear  32 . The gear  32  is engaged with the rack  33 . One end of the rack  33  is connected to the cam  34 . In this way, the cam  34  may drive the rack  33  to displace reciprocally during rotation, and the rack  33  drives the gear  32  to rotate, so as to drive the seat  31  to rotate. However, the aforementioned structure regarding the drive unit  30  is merely an example, and the present invention is not limited thereto. The drive unit  30  may also be a motor, a multi-link reciprocating mechanism, or other reciprocating mechanisms for driving the distance sensing unit  10  to rotate repeatedly within the rotation angle. 
     The compensation unit  40  acquires a rotation angle at the time when the drive unit  30  drives the distance sensing unit  10  to rotate, so as to provide a compensation value according to the rotation angle, and obtains an actual distance according to the compensation value and the distance value sensed by the distance sensing unit  10 . Herein, the compensation unit  40  may preferably be an encoder, but the present invention is not limited thereto. 
     In this embodiment, the present invention takes a two-dimensional distance measuring device as an example. As a result, the present invention may further include a revolving unit  20  disposed on the seat  31  for driving the distance sensing unit  10  to revolve according to a revolving angle. Herein, a revolving direction of the revolving unit  20  is substantially perpendicular to a rotation direction of the drive unit  30 . For example, the drive unit  30  drives the distance sensing unit  10  to rotate in an X-Y plane, and the revolving unit  20  drives the distance sensing unit  10  to revolve in an X-Z plane (or a Y-Z plane), but the present invention is not limited thereto. Furthermore, the compensation unit  40  may acquire a revolving angle at the time when the revolving unit  20  drives the distance sensing unit  10  to revolve, so as to provide a compensation value according to the revolving angle. 
     Please refer to  FIGS. 3 ,  4 , and  5 , in which when the cam  34  of the drive unit  30  rotates it drives the rack  33  to displace reciprocally in advancing and retreating directions. When the rack  33  advances, the gear  32  rotates in a clockwise direction to drive the seat  31  to rotate upwards, such that the distance sensing unit  10  rotates upwards. When the rack  33  retreats, the gear  32  rotates in a counterclockwise direction to drive the seat  31  to rotate downwards, such that the distance sensing unit  10  rotates downwards. Moreover, the distance sensing unit  10  continuously emits distance measuring signals with the emitter  11  and receives the distance measuring signals reflected by the target object with the receiver  12  in the process of rotation. At the same time when the drive unit  30  drives the distance sensing unit  10  to rotate, the revolving unit  20  drives the distance sensing unit  10  to revolve repeatedly within a revolving angle. The compensation unit  40  may acquire a rotation angle at the time when the drive unit  30  drives the distance sensing unit  10  to rotate and meanwhile acquire a revolving angle at the time when the revolving unit  20  drives the distance sensing unit  10  to revolve, provide a compensation value according to the rotation angle and the revolving angle, and then obtain an actual distance according to the compensation value and the distance value sensed by the distance sensing unit  10 . Herein, after acquiring the rotation angle and the revolving angle, the compensation unit  40  may perform a space coordinate conversion to obtain the space coordinates of the target object, and connect the space coordinates of the target object to coordinates of the distance sensing unit  10 , so as to obtain a relative position of the target object to the distance sensing unit  10  to calculate the actual distance. Therefore, a variable velocity of rotation caused by a simple harmonic motion of the reciprocating mechanism and an error due to that the position of an axis of revolution is not in the center can be corrected, so as to achieve an effect similar to that of a three-dimensional laser rangefinder. 
     The present invention uses a reciprocating mechanism to drive a distance sensing unit to move, so as to add an additional dimension thereto. For example, an original one-dimensional distance sensing unit achieves the measuring effect of a two-dimensional distance sensing unit by means of the reciprocating mechanism, or an original two-dimensional distance sensing unit achieves the measuring effect of a three-dimensional distance sensing unit by means of the reciprocating mechanism. Furthermore, the present invention may also apply two reciprocating mechanisms to a one-dimensional distance sensing unit, so that two dimensions are added to the one-dimensional distance sensing unit and it achieves the measuring effect of a three-dimensional distance sensing unit. In the present invention, measuring dimensions of the distance sensing unit are increased by the reciprocating mechanism having a low cost, and the simple harmonic motion caused by the reciprocating mechanism is corrected through acquisition of a rotation/revolving angle by a back-end compensation unit, such that the present invention can solve the problem of an excessively high cost of a conventional three-dimensional laser rangefinder, and can thus be widely applied in fields such as environment recognition, environment construction, obstacle detection, and the positioning of a robot. 
     While the present invention has been described by the way example and in terms of the preferred embodiments, it is to be understood that the invention need not to be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structures.