Abstract:
The invention relates to a measuring instrument, particularly a hand-held instrument ( 10 ) for measuring distances, comprising at least one transmission branch ( 28 ) for a test signal and adjustable switching means ( 36 ) for deflecting the test signal. The switching means ( 36 ) reflect at least a portion of the test signal in a first switched position ( 42 ) while unblocking the transmission branch ( 28 ) for the measuring radiation in a second switched position ( 42 ′). According to the invention, the switching means ( 36 ) reflect the measuring radiation in a diffuse manner in the first switched position ( 42 ). Also disclosed is a method for producing such a measuring instrument.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The invention described and claimed hereinbelow is also described in German Patent Application DE 10 2006 037 251.1 filed on Aug. 8, 2005. This German Patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119(a)-(d). 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a measuring device, in particular a hand-held device for measuring distances. 
     In order to attain the most accurate measurement result possible when performing a measurement, e.g., a distance measurement, it is advantageous when a known reference variable, e.g., a known reference distance in the case of a distance measurement, is available. With the aid of a reference variable of this type, the measurement device may be, e.g., calibrated occasionally, or transit times of the measurement signal inside the device may be determined so that they may be taken into account in a measurement. 
     Publication DE 198 040 50 A1 makes known a distance measurement with a laser diode and a photodiode for generating and/or receiving a send or receive signal. In order to calibrate this distance-measuring device, it is provided with an adjustable flap, which, when a reference measurement is carried out, is swiveled by a servo drive into an optical path of the transmitted measurement signal, thereby deflecting the transmitted measurement signal and directing it via a reference path directly to the photodiode. 
     Publication EP 1351070 A1 makes known an electro-optical, para-axial distance-measuring system, with which a rigid, stationary edge extends into the transmission path of the measuring device, in order to direct a portion of the measurement beam directly onto the receiving diode or an additional reference diode. 
     Publication DE 43 163 48 A1 makes known a device for measuring distance, which includes a switchable beam-deflection device, which may be swiveled about an axis using a motor. The surface of the beam-deflection device struck by the measurement beam reflects a directed, divergent light cone in the direction of an optical fiber, which is used as an optical waveguide. The opening of the light cone is so great that radiation may penetrate the incident face of the optical waveguide in all positions of the laterally displaceable optical waveguide. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a measuring device, in particular a hand-held measuring device for measuring distance, with at least one sending branch for a measurement signal, and with adjustable switching means for deflecting the measurement signal. In a first position, the switching means reflect at least a portion of the measurement signal and, in a second switching position, they release the sending branch for the measurement beam. 
     It is provided that, in the first position, the switching means reflect the measurement beam diffusely, i.e., in an undirected manner in particular. 
     Measuring devices, and rangefinders in particular, as they are designed today make it possible to measure distance across a large range. Rangefinders with a possible measurement width much greater than 100 m, with a resolution in the mm range, are now commercially available to anyone. In order to measure such a great distance while maintaining a high resolution of the distance measurement, a sensitive receiver and/or a measurement signal with a relatively high signal intensity are/is required. 
     When, as part of a reference measurement, the measurement signal is directed directly to a reference diode or the receiving diode, the high signal intensity may result in overdrive and, therefore, in a measuring error in the reference measurement. The purpose of a reference measurement—with which a reference path internal to the device is measured—is to increase the accuracy of the measuring device and, therefore, the reliability of the measurement, however. 
     With devices in the related art, the radiation intensity in a reference measurement is therefore reduced, e.g., via a large distance to the receiver or by using additional filter elements. 
     Given that rangefinders are becoming smaller and more compact, a direct path between the reference switchover element and the receiving or reference diode is desired, in particular. This direct path of the measurement signal to the reference diode results in a high measurement signal intensity on the receiving detector, however. 
     Advantageously, with the measuring device provided, the measurement beam in a reference measurement is not sent completely and in a targeted manner to the receiving diode used in the reference measurement. Instead, only a fraction of the measurement signal is used. Switching means are provided in the device for this purpose, which, in a first switch position, reflect and/or scatter the measurement signal diffusely, thereby allowing only a portion of the light intensity to strike a reference receiver. 
     Due to the diffuse reflection or scattering on the switching means, the measurement signal intensity used in the reference measurement is greatly reduced. The inventive embodiment of the switching means, which serve as the reference flap, may be manufactured using simple production means and in a cost-neutral manner. No additional components are required to reduce the signal. 
     The switching means advantageously include a reflecting surface, on which the measurement signal is reflected when a reference measurement is performed. The reflecting surface has an uneven surface structure. The surface structure of this reflecting surface of the switching means may be formed directly in the process of manufacturing the switching means. It is possible, e.g., to provide a defined eroding structure in an injection-moulding tool used to form the switching means. The switching means and the reflection structure may be advantageously formed directly in plastic. 
     In an advantageous embodiment of the inventive measuring device, the reflecting surface of the switching means are provided with a prism structure in the region of impact of the measurement beam, which results in a diffuse reflection, and, in particular, to a directionally-dependent, diffuse reflection of the measurement signal. 
     In an alternative embodiment of an inventive measuring device, the reflecting surface of the switching means may have a plurality of curved sub-surfaces, which result in a diffuse reflection and/or scattering of the incident measurement signal. Circular, curved cylindrical surfaces, for example, similar to a Frenel lens may be installed on or formed in the reflecting surface of the switching means. It is also possible to provide a large number of spherically curved surfaces or a combination of several surface structures of different types. In a further embodiment of the switching means, a plurality of cylindrically curved surfaces for diffuse reflection is provided. 
     One thing that all of these embodiments of the reflecting surface of the switching means have in common is the fact that the diffuse reflection is retained despite the dependence on direction, so that, after the measurement signal is reflected on the actuator, only a fraction of it strikes a receiving detector, which serves to provide a reference measurement. 
     Advantageously, the reflecting and/or scattering structure is designed as a single piece with the reflecting surface of the switching means. In particular, the reflecting surface may be formed directly during the injection-moulding process for the switching means, thereby resulting in a simple manufacturing method for the advantageous switching means and, therefore, for the inventive measuring device. 
     Further advantages of the inventive measuring device are disclosed in the drawing below and in the related description. 
     An exemplary embodiment of an inventive measuring device and several exemplary embodiments of an inventive switching means are depicted in the drawing, and they are described in greater detail in the subsequent description. The figures in the drawing, their description, and the claims contain combinations of numerous features. One skilled in the art will also consider the features individually and combine them to form further reasonable combinations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a distance-measuring device with a transmitting unit, a receiver unit, and a deflecting unit, in a perspective overview depiction, 
         FIG. 2  shows a switching means of an inventive measuring device, in a sectional view, 
         FIG. 3  shows a detailed view of the reference path of an inventive measuring device, in a schematic top view, 
         FIG. 4  shows a perspective view of a first exemplary embodiment of an inventive switching means, 
         FIG. 5  shows an alternative exemplary embodiment of an inventive switching means, in a perspective view. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a measuring device designed as a distance-measuring device  10 . Distance-measuring device  10  includes a housing  12 , and actuating elements  14  for switching distance-measuring device  10  on and off, and for starting and configuring a measuring procedure. In addition to actuating elements  14 , the measuring device also includes a display  16  for depicting measurement results. The following are located on a carrier element  18  inside housing  12  of measuring device  10 : A transmitting unit  20  designed as a laser diode for generating an optical transmitted measurement signal, a light channel  22 , a deflecting unit  24  for deflecting the transmitted measurement signal, and a receiver unit  26  designed as a photodiode for receiving the received measurement signal.  FIG. 1  shows schematic depictions of transmitting unit  20 , light channel  22 , deflecting unit  24 , and a reference path  34  for receiver unit  26 . 
     To measure a distance of distance-measuring device  10  to a remote object, transmitting unit  20  sends out a transmitted measurement signal along a sending branch  28  during operation. The transmitted measurement wavelength leaves the measuring device via a window  30  in housing  12  of the device. The measurement signal, which is reflected by a surface of a remote object, is received as a received measurement signal via receiving optics  32  by receiver unit  26 , e.g., a photodiode. The transit time of the light may be deduced from this received measurement signal, e.g., using a phase comparison carried out between the transmitted measurement signal and the received measurement signal, thereby making it possible to determine the distance between the measuring device and the object to be measured based on the speed of light, which is a known quantity. 
     A reference measurement is carried out before a distance measurement is performed, in order to take transit times into account that are independent of the distance and that result, e.g., when the transmitted measurement signal is generated and/or when the received measurement signal is processed in the device. The transmitted measurement signal is deflected by deflection unit  24 , and it is directed via a known reference path along a path  34  directly to receiver unit  26 . In particular, no further optical components are located between deflecting unit  24  and reference diode  26 , which serves as a receiver unit, thereby ensuring that the measurement signal coming directly from the deflecting unit strikes the reference diode. 
       FIG. 2  shows a deflecting unit  24  with switching means  36 , which are designed essentially as a swivelable reference flap. It may be located, e.g., in light channel  22  of measuring device  10 , and it may be supported such that it may swivel around a rotation axis  38 . Switching means  36 , which are designed as a flap-type element, are shown in  FIG. 2  in their second switching position  42 ′, so that sending branch  28  and/or channel  22  are/is released for the measurement wavelength. Flap-type element  36 , in its first position  42 , is also shown in  FIG. 2 , using dashed lines. In this first switched position  42  of switching element  36 , the measurement signal, which is sent out along sending branch  28 , is scattered on a reflecting surface  50  of switching means  36 . Direction  29  of reference path  34  is also indicated in  FIG. 2 ; it corresponds to the direction of a specular reflection of the measurement signal on reflecting surface  50 . In contrast to specular reflection, a diffuse reflection or scattering takes place in the inventive measuring device, so a direction is not indicated therefor. 
       FIG. 3  shows a detailed top view of reference path  34  of an inventive measuring device. A transmitting unit  20 , which is designed as a laser diode, sends out a measurement signal along measurement path  28 , which is then reflected on switching means  36  of a deflecting unit  24 . To this end, switching means  36  include a reflecting surface  50 , which has—at least partially—an uneven, i.e., raw, in particular, surface structure  52 . Due to uneven surface structure  52 , the measurement signal is diffusely reflected and/or scattered on the switching means, so that the measurement signal is reflected not only in specular direction  29 , but rather nearly in the entire half-space located opposite to reflecting surface  50 . The reflection and/or scattering on the inventive switching means therefore takes place in a non-directed manner. This is indicated symbolically in  FIG. 3  as a large number of measurement beam directions  31 . Since the measurement signal that strikes switching means  36  is reflected diffusely and/or scattered, only a fraction of the measurement signal intensity reaches active surface  52  of receiver unit  26 , as shown in  FIG. 3 . 
       FIG. 4  shows a first exemplary embodiment of switching means  36 , which are designed as a flap-type element. Switching means  36  include a shaft  54 , via which the switching means are supported in a manner that allows them to rotate around an axis  38 . A permanent magnet  56  is installed on shaft  54 . Permanent magnet  56  interacts with a controllable electromagnet, which is not shown in  FIG. 4 , thereby causing switching means  36  to rotate about central axis  38  of shaft  54  when the electromagnet is actuated accordingly. 
     A reflecting surface  50 , which has—at least partially—an uneven, i.e., raw, in particular, surface structure  52 —is formed as a single piece with shaft  54 . To this end, reference surface  50  may have a prism structure  58  in the region of impact of the measurement radiation, which results in a diffuse reflection of the measurement beam that strikes this structure  58 . Advantageously, shaft  54 , reflecting surface  50 , and prism structure  58  are designed as a single piece, e.g., made of plastic. In this manner, the uneven surface structure  52  of switching means  36  may be formed directly when the switching means are formed. The switching means may be manufactured, e.g., using an injection-moulding process in which uneven surface structure  52  is manufactured simultaneously with switching means  36  and, therefore, in a cost-neutral manner. For example, a defined eroding structure could be present at the corresponding point in the injection-moulding tool, which forms a corresponding structure—an uneven structure, in particular—on reflecting surface  50  of switching means  36 . 
     In addition to prism structure  58  shown in  FIG. 4 , any type of uneven or raw surface structure  52  is possible. For example, uneven surface structure could also be produced using a plurality of curved surfaces  60  or  62 , as depicted in a second exemplary embodiment of the inventive switching means shown in  FIG. 5 . Curves surfaces  60  and  62  could be designed as circular, curved cylindrical surfaces, similar to the structure of a Fresnel lens. A plurality of spherically curved surfaces or a plurality of cylindrically curved surfaces is also possible. Diffusely scattering surface structure  52  may also be produced using a combination of the structures shown here as examples or using a combination of further structures, of course. 
     Inventive switching element  36  and inventive measuring device  10  are not limited to the exemplary embodiments shown in the figures. 
     In particular, surface structure  52  of inventive switching element  36  is not limited to the embodiments shown in the figures. The type of diffusely scattering structure  52  and its boundary surface are not limited to the exemplary embodiments. Diffusely scattering structure  52  may also be formed with a round, rectangular, non-square, or oval boundary, for example.