Patent Publication Number: US-2023139573-A1

Title: Non-contact probe and profile measurement apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to Japanese Patent Applications number 2021-176229, filed on Oct. 28, 2021 contents of which are incorporated herein by reference in their entirety. 
     BACKGROUND OF THE INVENTION 
     The present disclosure relates to a non-contact probe and a profile measurement apparatus. A profile measurement apparatus is provided with a non-contact probe that radiates a laser beam onto a workpiece to detect a profile of the workpiece in a non-contact manner. The non-contact probe is provided with a mirror that reflects the laser beam from an irradiating part toward the workpiece and reflects a reflected light from the workpiece toward the light receiving part. The mirror is disposed in a manner to be swingable by a galvano motor. 
     Since the above-mentioned mirror has a function of reflecting the laser beam from the irradiating part and a function of reflecting the reflected light from the workpiece, the mirror surface becomes large and the galvano motor that drives the mirror also becomes large. Further, since the galvano motor supports the mirror in a cantilever manner, the posture of the mirror may become unstable. 
     BRIEF SUMMARY OF THE INVENTION 
     The present disclosure focuses on these points, and its object is to provide a non-contact probe capable of driving a mirror in a stable posture with a small-sized galvano motor. 
     A first aspect of the present disclosure provides a non-contact probe including: an irradiating part that radiates a laser beam; a first mirror that reflects the laser beam from the irradiating part toward a workpiece; a second mirror that reflects a reflected light from the workpiece; and a galvano motor capable of swinging both the first mirror and the second mirror, wherein the first mirror is provided at a first axial end of a motor shaft that extends on both ends of the galvano motor, and the second mirror is provided at a second axial end of the motor shaft. 
     A second aspect of the present disclosure provides a profile measurement apparatus including: an irradiating part that radiates a laser beam; a first mirror that reflects the laser beam from the irradiating part toward a workpiece; a second mirror that reflects a reflected light from the workpiece toward a light receiving part; and a galvano motor capable of swinging both the first mirror and the second mirror; a calculation part that calculates a profile of the workpiece on the basis of an output of the light receiving part, wherein the first mirror is provided at a first axial end of a motor shaft that extends on both ends of the galvano motor, and the second mirror is provided at a second axial end of the motor shaft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram illustrating an outline of a profile measurement apparatus  1 . 
         FIG.  2    is a schematic perspective view illustrating an internal configuration of a non-contact probe  10 . 
         FIG.  3    is a front view of  FIG.  2   . 
         FIG.  4    is a planar view of  FIG.  2   . 
         FIG.  5    is a schematic diagram illustrating configurations of an irradiating mirror  40 , a light-receiving mirror  42 , and a galvano motor  44 . 
         FIG.  6    is a schematic diagram illustrating a variation example. 
         FIG.  7    is a schematic diagram illustrating a detailed configuration of a fixing plate member  60 . 
         FIG.  8    is a schematic diagram illustrating a state of a deformation part  65  when a frame part  15  has thermally expanded. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, the present disclosure will be described through exemplary embodiments, but the following exemplary embodiments do not limit the invention according to the claims, and not all of the combinations of features described in the exemplary embodiments are necessarily essential to the solution means of the invention. 
     &lt;Outline of a Profile Measurement Apparatus&gt; 
     An outline of a profile measurement apparatus including a non-contact probe according to an embodiment will be described with reference to  FIG.  1   . 
       FIG.  1    is a schematic diagram illustrating an outline of a profile measurement apparatus  1 . The profile measurement apparatus  1  is a three-dimensional profile measurement apparatus that measures a three-dimensional profile of a workpiece which is an object to be measured, for example. As shown in  FIG.  1   , the profile measurement apparatus  1  includes a non-contact probe  10 , a moving mechanism  80 , and a control apparatus  90 . 
     The non-contact probe  10  radiates a laser beam onto the workpiece placed on a surface plate, and captures an image of the workpiece on the basis of light reflected from a surface of the workpiece. The non-contact probe  10  includes an irradiating part  20 , a light receiving part  30 , and a probe controller  70 . The detailed configuration of the non-contact probe  10  will be described later. 
     The irradiating part  20  radiates the laser beam onto the workpiece. The irradiating part  20  includes a light source  22 . The light source  22  is formed of a laser diode (LD) or the like, for example, and generates and emits a laser beam of a predetermined wavelength. 
     The light receiving part  30  functions as an imaging part that receives the laser beam reflected by the workpiece and captures an image of the workpiece. The light receiving part  30  includes an imaging sensor  32 . The imaging sensor  32  is an image sensor that captures the image of the workpiece. A CMOS image sensor is used as the image sensor, for example. 
     The probe controller  70  controls the operation of the non-contact probe  10 . The probe controller  70  controls radiation of the laser beam by the light source  22  of the irradiating part  20  and imaging of the image of the workpiece by the imaging sensor  32  of the light receiving part  30 . 
     The moving mechanism  80  moves the non-contact probe  10  relative to the workpiece. For example, the moving mechanism  80  moves the non-contact probe  10  in three axial directions orthogonal to each other. The non-contact probe  10  is detachably attached to the moving mechanism  80 . 
     The control apparatus  90  controls the operation of the non-contact probe  10  and the moving mechanism  80 . The control apparatus  90  performs the measurement using the non-contact probe  10  by moving the non-contact probe  10  with the moving mechanism  80 , for example. The control apparatus  90  includes a storage  92 , a control part  94 , and a calculation part  96 . 
     The storage  92  includes a read only memory (ROM) and a random access memory (RAM), for example. The storage  92  stores various types of data and a program executable by the control part  94 . For example, the storage  92  stores a result of the measurement by the non-contact probe  10 . 
     The control part  94  is a central processing unit (CPU), for example. The control part  94  controls the operation of the non-contact probe  10  via the probe controller  70  by executing the program stored in the storage  92 . Specifically, the control part  94  controls the radiation of the laser beam to the workpiece by the irradiating part  20 . 
     The calculation part  96  calculates the profile of the workpiece onto which the non-contact probe  10  radiates the laser beam. The calculation part  96  acquires an output of the light receiving part  30 , and calculates the profile of the workpiece. 
     &lt;Internal Configuration of the Non-Contact Probe&gt; 
     An internal configuration of the non-contact probe  10  will be described with reference to  FIGS.  2  to  8   . 
       FIG.  2    is a schematic perspective view illustrating the internal configuration of the non-contact probe  10 .  FIG.  3    is a front view of  FIG.  2   .  FIG.  4    is a planar view of  FIG.  2   .  FIG.  5    is a schematic diagram illustrating configurations of an irradiating mirror  40 , a light-receiving mirror  42 , and a galvano motor  44 . In  FIGS.  2  to  4   , for convenience of explanation, an outer cover of the non-contact probe  10  is omitted. In  FIG.  5   , the traveling direction of a laser beam is indicated by a broken arrow. 
     As shown in  FIG.  2   , the non-contact probe  10  includes a frame part  15 , a irradiating part  20 , a light receiving part  30 , the irradiating mirror  40 , the light-receiving mirror  42 , the galvano motor  44 , reflection mirrors  50  and  53 , a fixing plate member  60 , and a focusing lens  68 . In the present embodiment, the irradiating mirror  40  corresponds to a first mirror, and the light-receiving mirror  42  corresponds to a second mirror. 
     The frame part  15  forms a skeleton of the non-contact probe  10 , and is made of a metal material. An opening part is formed in the frame part  15  so that the laser beam radiated by the irradiating part  20  and the reflected light from the workpiece can pass through the opening part. The frame part  15  supports the irradiating part  20 , the light receiving part  30 , the galvano motor  44 , the focusing lens  68 , and the like. Specifically, the galvano motor  44  is supported inside the frame part  15 , and the irradiating part  20 , the light receiving part  30 , and the focusing lens  68  are supported on an upper portion of the frame part  15 . The frame part  15  may be made of engineering plastic such as aluminum, a magnesium alloy, polycarbonate, or carbon fiber reinforced plastic. This makes it possible to reduce the weight of the non-contact probe  10 . 
     As shown in  FIG.  3   , the irradiating part  20  is located at one end of the frame part  15  in the longitudinal direction. The light source  22  ( FIG.  1   ) and a lens such as a collimator lens are disposed inside the irradiating part  20 . 
     As shown in  FIG.  3   , the light receiving part  30  is located at one end of the frame part  15  in the longitudinal direction. The light receiving part  30  is provided with the imaging sensor  32  ( FIG.  1   ) that receives the reflected light from the workpiece (specifically, the reflected light that passed through the focusing lens  68 ). 
     The irradiating mirror  40  reflects the laser beam from the irradiating part  20  toward the workpiece. In the frame part  15 , the irradiating mirror  40  is located at one end in the longitudinal direction and immediately below the irradiating part  20 , as shown in  FIG.  3   . The irradiating mirror  40  is swingable so that an irradiation direction of the laser beam can be adjusted. The laser beam reflected by the irradiating mirror  40  passes through the opening part of the frame part  15  and reaches the workpiece. 
     The light-receiving mirror  42  is a mirror that reflects the reflected light from the workpiece. In the frame part  15 , the light-receiving mirror  42  is located at the other end in the longitudinal direction, as shown in  FIG.  3   . The light-receiving mirror  42  can swing in conjunction with the irradiating mirror  40 . The reflected light reflected by the light-receiving mirror  42  passes through the opening part of the frame part  15  and reaches the reflection mirror  50 . 
     The galvano motor  44  is a motor capable of swinging both the irradiating mirror  40  and the light-receiving mirror  42 . Specifically, the galvano motor  44  simultaneously swings the irradiating mirror  40  and the light-receiving mirror  42 . As shown in  FIG.  3   , the galvano motor  44  includes a motor shaft  45  extending from the ends of a motor body  44   a . The motor shaft  45  pierces through the motor body  44   a.    
     The irradiating mirror  40  is provided at one axial end of the motor shaft  45 , and the light-receiving mirror  42  is provided at the other axial end of the motor shaft  45 . Specifically, the irradiating mirror  40  is fixed to a D-cut portion at one axial end portion of the motor shaft  45 , and the light-receiving mirror  42  is fixed to a D-cut portion at the other axial end portion of the motor shaft  45 . That is, the motor shaft  45  supports the irradiating mirror  40  and the light-receiving mirror  42  at respective ends thereof. 
     When the irradiating mirror  40  and the light-receiving mirror  42  are disposed at the ends of the motor shaft  45  in this manner, the weight of each mirror can be reduced as compared with the case where the irradiating mirror  40  and the light-receiving mirror  42  are disposed integrally on one end of the motor shaft  45 , and the load torque of the galvano motor  44  can be reduced. Therefore, it becomes easy to downsize the galvano motor  44 . In addition, when the motor shaft  45  supports the irradiating mirror  40  and the light-receiving mirror  42  at respective ends, the postures of the irradiating mirror  40  and the light-receiving mirror  42  are more likely to be stabilized than when the motor shaft  45  supports the irradiating mirror  40  and the light-receiving mirror  42  in a cantilevered manner. As a result, the radiation of the laser beam and the reception of the reflected light can be performed with high accuracy (in other words, it is possible to prevent an occurrence of an error in a light receiving position of the reflected light in the light receiving part  30 ). 
     The weight of the irradiating mirror  40  is lighter than the weight of the light-receiving mirror  42 . Further, the size of the irradiating mirror  40  is smaller than the size of the light-receiving mirror  42 . Preferably, the size of the irradiating mirror  40  is equal to or smaller than half the size of the light-receiving mirror  42 . This is because the irradiating part  20  irradiates the irradiating mirror  40  with the laser beam at a spot, and a reflection position of the laser beam at the irradiating mirror  40  hardly varies even when the irradiating mirror  40  swings, so that the irradiating mirror  40  is made smaller. By reducing the size of the irradiating mirror  40 , the load torque of the galvano motor  44  can be further reduced. 
     A rotary encoder  48  is attached to the motor shaft  45 . The rotary encoder  48  detects a rotational position and a rotational speed of the galvano motor  44 . The rotary encoder  48  is provided between the motor body  44   a  and the irradiating mirror  40  in the motor shaft  45 . That is, the rotary encoder  48  is disposed nearer to the irradiating mirror  40 , which is small in size. As a result, a weight difference between one end side and the other end side when viewed from the motor body  44   a  can be reduced, so that the rotation of the galvano motor  44  can be stabilized. 
     The rotary encoder  48  can be configured with a type of rotary encoder (an absolute encoder) that is capable of outputting an absolute signal. Since the absolute encoder is an encoder that outputs an absolute value of a rotation angle, the rotary encoder  48  can measure the absolute value of the rotation angle of the irradiating mirror  40  and the absolute value of the rotation angle of the light receiving mirror  42 . This eliminates the need for reference positioning of the rotary encoder  48  at the time of activation, thereby reducing the initial setting time taken for activation. The rotary encoder  48  is not limited to the above, and may be configured with a type of rotary encoder that is capable of outputting an incremental signal and a Z-phase signal (reference position signal). 
       FIG.  6    is a schematic diagram illustrating a variation example. As shown in  FIG.  6   , a regulation block  49   a  may be provided on a stator side of the galvano motor  44 , and a stopper part  49   b  may be provided on a rotor side. The regulation block  49   a  is formed by cutting out a part of a cylindrical block. The stopper part  49   b  is attached to the motor shaft  45  in a manner to be swingable together with the motor shaft  45 . When the galvano motor  44  swings the irradiating mirror  40  and the light-receiving mirror  42 , the stopper part  49   b  regulates the swing by abutting against the regulation block  49   a . In this case, the rotary encoder  48  may output a signal corresponding to a position where the stopper part  49   b  abutted against the regulation block  49   a  to perform reference positioning. This makes it possible to accurately perform reference positioning at the time of activation. Further, the size and weight of the rotary encoder according to the variation example can be made more compact than those of the absolute rotary encode inexpensively. 
     The reflection mirrors  50  and  53  are provided above the light-receiving mirror  42 , and reflect the reflected light reflected by the light-receiving mirror  42  toward the light receiving part  30 . Specifically, the reflection mirror  50  reflects the reflected light from the light-receiving mirror  42  to the reflection mirror  53 , and the reflection mirror  53  reflects said reflected light toward the focusing lens  68 . The reflection mirrors  50  and  53  are provided at positions apart from each other on the frame part  15 . 
     As shown in  FIG.  3   , the reflection mirrors  50  and  53  are located at the other end of the frame part  15  in the longitudinal direction. That is, the reflection mirrors  50  and  53  are located on the opposite side of the irradiating part  20 . Therefore, the reflection mirrors  50  and  53  are less likely to be affected by heat generated by the irradiating part  20 . Disposing the irradiating mirror  40  and the light-receiving mirror  42  apart from each other at the ends of the motor shaft  45  increases the degree of freedom in terms of the installation position of the reflection mirrors  50  and  53  and the irradiating part  20 . 
     The reflection mirror  50  is supported by a support member  51 , and the reflection mirror  53  is supported by a support member  54 . The support members  51  and  54  are made of ceramics, for example, and have heat insulating properties. Since the support members  51  and  54  have heat insulating properties, it is possible to prevent or reduce conduction of heat from the frame part  15  to the reflection mirrors  50  and  53 . 
     The reflection mirrors  50  and  53  are not directly supported by the frame part  15 , but are supported via the fixing plate member  60 . The fixing plate member  60  is provided on the frame part  15 . Specifically, the fixing plate member  60  is supported at two locations on the upper portion of the other end of the frame part  15  in the longitudinal direction. The reflection mirrors  50  and  53  are fixed to the fixing plate member  60 . Although two reflection mirrors  50  and  53  are provided in the above description, the present disclosure is not limited thereto. The number of reflection mirrors that reflect the reflected light reflected by the light-receiving mirror  42  toward the light receiving part  30  may be one. 
     In the present embodiment, a linear expansion coefficient of the fixing plate member  60  is smaller than a linear expansion coefficient of the frame part  15 . Specifically, the fixing plate member  60  is formed of a titanium plate, and a linear expansion coefficient of the titanium plate is smaller than a linear expansion coefficient of the material forming the frame part  15 . Therefore, since the degree of heat change of the fixing plate member  60  is small even when the heat rises, a change in the relative positions of the reflection mirrors  50  and  53  fixed to the fixing plate member  60  can be reduced. As a result, it is possible to prevent an occurrence of an error in the light receiving position of the reflected light in the light receiving part  30 . 
       FIG.  7    is a schematic diagram illustrating a detailed configuration of the fixing plate member  60 . The fixing plate member  60  includes a flat plate part  61 , a plurality of holes  62   a ,  62   b , and  62   c , a plurality of narrow portions  63   a ,  63   b ,  63   c , and  63   d , and a connection portion  64 . 
     The flat plate part  61  is formed of sheet metal having a predetermined thickness. The holes  62   a ,  62   b , and  62   c  are formed in the flat plate part  61  at positions away from a portion where the reflection mirrors  50  and  53  are fixed. The holes  62   a  to  62   c  are formed adjacent to each other at one corner of the flat plate part  61 . 
     The narrow portions  63   a ,  63   b ,  63   c  and  63   d  are each a portion having a narrow width, and are adjacent to the holes  62   a  to  62   c . The widths of the narrow portions  63   a  to  63   d  are each equal to or less than the thickness of the flat plate part  61 , for example. Since the rigidity of the narrow portions  63   a  to  63   d  is lower than that of other portions, the narrow portions  63   a  to  63   d  are likely to deform when a force is applied. 
     The connection portion  64  is a portion connected to the four narrow portions  63   a  to  63   d . The holes  62   a  to  62   d  are located around the connection portion  64 . In the present embodiment, the four narrow portions  63   a  to  63   d  and the connection portion  64  function as a deformation part  65  which deforms when the frame part  15  thermally expands. 
       FIG.  8    is a schematic diagram illustrating a state of the deformation part  65  when the frame part  15  thermally expands. When the frame part  15  thermally expands, the deformation part  65  having low rigidity in the fixing plate member  60  in contact with the frame part  15  receives a force from the frame part  15  and deforms, as shown in  FIG.  8   . In  FIG.  8   , the narrow portions  63   a  to  63   d  deform so as to be bent, and the connection portion  64  is located so as to swell with respect to the flat plate part  61 . Since the deformation part  65  deforms in this manner, the fixing plate member  60  functions to absorb the thermal expansion of the frame part  15 . Therefore, even when the frame part  15  thermally expands, a change in the relative positions of the reflection mirrors  50  and  53  can be prevented. 
     The focusing lens  68  focuses light onto the light receiving part  30 . Specifically, the focusing lens  68  focuses light onto an imaging surface of the imaging sensor  32 . Although the non-contact probe  10  is provided in the profile measurement apparatus  1  in the above-mentioned embodiment, the present disclosure is not limited thereto. For example, the non-contact probe  10  may be applied to a coordinate measuring machine that measures three-dimensional coordinates of a workpiece. 
     Effect of the Present Embodiment 
     In the non-contact probe  10  of the present embodiment, the irradiating mirror  40  that reflects the laser beam from the irradiating part  20  toward the workpiece is provided at one axial end of the motor shaft  45  that extends on the ends of the galvano motor  44 , and the light-receiving mirror  42  that reflects the reflected light from the workpiece is provided at the other axial end of the motor shaft  45 . That is, the motor shaft  45  supports the irradiating mirror  40  and the light-receiving mirror  42  at respective ends thereof. When the irradiating mirror  40  and the light-receiving mirror  42  are disposed on the ends of the motor shaft  45 , the weight of each mirror can be reduced and the load torque of the galvano motor  44  can be reduced as compared with the case where the irradiating mirror  40  and the light-receiving mirror  42  are disposed integrally at one end of the motor shaft  45 . Therefore, it becomes easy to downsize the galvano motor  44 . In addition, when the motor shaft  45  supports the irradiating mirror  40  and the light-receiving mirror  42  at respective ends thereof, postures of the irradiating mirror  40  and the light-receiving mirror  42  are more likely to be stabilized than when the motor shaft  45  supports the irradiating mirror  40  and the light-receiving mirror  42  in a cantilevered manner. 
     The present disclosure is explained based on the exemplary embodiments. The technical scope of the present disclosure is not limited to the scope explained in the above embodiments and it is possible to make various changes and modifications within the scope of the disclosure. For example, all or part of the apparatus can be configured with any unit which is functionally or physically dispersed or integrated. Further, new exemplary embodiments generated by arbitrary combinations of them are included in the exemplary embodiments. Further, effects of the new exemplary embodiments brought by the combinations also have the effects of the original exemplary embodiments.