Abstract:
An optical device for establishing a spatial orientation for a drill bit includes at least three light sources and two cameras. The first light source is used to silhouette the drill bit; a second light source is used to generate a reflection from a primary facet of the drill bit; and a third light source is used to generate a reflection from the margin of the drill bit. In sequence, the first camera responds to the first light source to establish an axial position for the drill bit on the axis. The second camera then responds to the second light source to establish a gross rotational position for the drill bit on its axis. Finally, the first camera is again used. This time it establishes a precise rotational position for the drill bit on its axis to establish the spatial orientation for the drill bit.

Description:
This application is a continuation-part of application U.S. Ser. No. 09/305,608, filed May 5, 1999, which is currently pending. The contents of application U.S. Ser. No. 09/305,608 are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention pertains generally to inspection systems and methods. More particularly, the present invention pertains to systems and methods for inspecting and evaluating machine tools. The present invention is particularly, but not exclusively, useful as a device and a method for using same which employs optical techniques for selectively inspecting and evaluating the operational serviceability of drill bits. 
     BACKGROUND OF THE INVENTION 
     A “drill bit” is defined as a removable drilling or boring tool for use in a brace, drill press, or the like, and will generally be of a type that is classified either as an auger or as a straight shank drill bit. Of particular interest for the present invention is the so-called straight shank drill bit. 
     In order to drill or bore a hole into a surface with a straight shank drill bit, the drill bit is rotated relative to the surface by a brace or drill press. Sharp edges on the front or tip of the drill bit then cut into the surface. Due to the drill bit&#39;s configuration, the material that is cut as the drill bit is rotated is removed so that the result is a clean hole in the surface. Not surprisingly, with extended use, a drill bit can become worn. Thus, periodic screening may be necessary to determine whether the drill bit can be reshaped and reused, or must be discarded. Whenever a large number of particularly small drill bits are involved, the inspection and selection process for screening the drill bits can become quite labor intensive and very time consuming. 
     It happens that there is a standard configuration for straight shank drill bits. Importantly, although the particular dimensions of drill bits and the exact angles between respective component parts of different drill bits will vary, all straight shank drill bits generally have the same general configuration. Consequently, the component parts of the drill bit always have the same relationship relative to each, and they always have the same relationship relative to the longitudinal axis of the drill bit. Specifically, at the front end, or tip, of the drill bit are a pair of component parts more commonly referred to as primary facets. These primary facets are generally flat surfaces, and they each have a side which is aligned along a common diameter (extension line). Further, the primary facets are on opposite sides of the drill bit&#39;s longitudinal axis, and they are on opposite sides of their common diameter (extension line). Depending on the model of the drill bit, a normal to the primary facets will be inclined to the longitudinal axis of the drill bit by an angle α. 
     In addition to the primary facets mentioned above, the tip of the drill bit is also formed with a pair of diametrically opposed secondary facets that are each juxtaposed with a respective primary facet. Additionally, the drill bit has a pair of helical shaped flutes that continue from a respective secondary facet and extend generally along the length of the drill bit shank parallel to the axis. Each of these flutes is characterized by a margin that borders the flute along the length of the drill bit. For operational purposes, however, of all the component parts of the drill bit, it is the primary facets that face the most wear and are, therefore, of most concern. As indicated above, however, the primary facets are positioned in a rather complex geometrical orientation on the drill bit. Accordingly, any regrinding of the primary facets that may be necessary in order to maintain the serviceability of the drill bit must be done with a great deal of precision and care. 
     There are many optical techniques which have been used for purposes of inspecting and evaluating various items. While some of these techniques merely require adequate illumination of the item, others can involve highly sophisticated interference, absorption or specular analysis. In each case, some aspect or characteristic of light plays an important role. For the present invention, the characteristic of light that is of most importance is reflection. 
     In general, the reflection of light from an object can be classed as being either specular reflection or non-specular, diffuse reflection. In the case of non-specular or diffuse reflection, the reflection of light from a rough surface results in a scattering of the light wave components. On the other hand, the specular reflection of light occurs when a wavefront of light is diverted from a polished surface, so that the angle of the incident wave to the normal at the point of reflection is the same as that of the reflected wave. For irregular shaped objects, such as a drill bit, the specular reflection of light can be observed from predetermined surfaces. Specifically, depending on the known location of a light source, and the expected location of a particular surface, a detector (such as a camera) can be appropriately positioned to receive a specular reflection from the surface. The presence or absence of the specular reflection can then be used as intelligence for purposes of orienting or inspecting the item on which the surface is located. 
     In light of the above, it is an object of the present invention to provide an optical device and a method which uses specular reflections from a drill bit to establish a spatial orientation for the drill bit. Another object of the present invention is to provide an optical device and a method which uses specular reflections from a drill bit, in concert with other illumination techniques, to measure dimensions of the drill bit. Still another object of the present invention is to provide an optical device and a method which uses specular reflections to inspect for irregularities in selected surfaces and boundaries of these surfaces. Yet another object of the present invention is to provide an optical device and a method which is easy to use, relatively simple to manufacture, and comparatively cost effective. 
     SUMMARY OF THE PREFERRED EMBODIMENTS 
     In accordance with the present invention, an optical device for establishing a predetermined spatial orientation for a drill bit includes three separate light sources which are used for selectively illuminating the drill bit in at least three different illumination schemes. The device also includes two camera systems that are used for creating images of the drill bit under the different illumination schemes. Specifically, the images of the drill bit are used to establish a spatial orientation for the drill bit in which subsequent grinding or inspection of the drill bit can be accomplished. As contemplated by the present invention, the drill bit will define a longitudinal axis and it will have a pair of diametrically opposed primary facets. Normals (i.e. perpendicular lines) to these primary facets will be inclined at a known angle α to the axis. Specifically, as determined for the present invention, α=cos −1  (1/(1+tan 2 (φ)+tan 2 (ψ))) where, in a Cartesian coordinate system, α is an angle with the z axis (the longitudinal axis), φ is an angle of rotation about the x axis, and ψ is an angle of rotation about the y axis. Additionally, the drill bit will have margins which border helical flutes that extend generally along the length of the drill bit parallel to the axis. 
     Insofar as the light sources are concerned, it is to be appreciated that the present invention does not use diffuse light sources. Instead, semicollimated light sources are used. One light source (the first light source) generates a light beam that is directed perpendicular to the drill bit for the purpose of silhouetting the drill bit. Another light source (the second light source) is used to generate reflections from the primary facets of the drill bit. Still, another light source (the third light source) is used to generate reflections from the margin of the drill bit. Using these various illumination schemes, the device of the present invention creates camera images that indicate how the drill bit needs to be moved in order to acquire the desired spatial orientation. 
     One camera in the optical device of the present invention (the first camera) views the drill bit from a position that is directly opposite the drill bit from the silhouetting light source. In this position, this camera creates a shadow silhouette image of the drill bit that can be used to establish the axial position of the drill bit. Also, the position of this camera allows it to create images of a margin on the drill bit by using light that has been reflected from the drill bit margin. Another camera (the second camera) is positioned on an extension of the drill bit axis, and is used to create images of the drill bit facets that are formed by light that has been reflected along the axis. 
     While the silhouetting light source (first light source) and the light source that is used to illuminate the drill bit margins (third light source) can each be a single LED, the light source that is used to illuminate the primary facets of the drill bit (second light source) is more complex. Specifically, this light source (second light source) includes many individual light sources (LEDs) which are positioned and operated, relative to each other, in a specific manner. 
     In detail, the light source that is used to illuminate the primary facets of the drill bit (second light source) includes a plurality of arrays (e.g. sixteen arrays) that are formed as a ring. Further, each array in the ring is slightly tilted relative to a central axis and includes a plurality of individual light sources (LEDs) that are arranged in a plurality of rows (e.g. seven rows). Geometrically, the arrays are positioned around the ring in diametrically opposed pairs (i.e. sixteen arrays provide eight pairs), and the ring is oriented in a plane with each row of light sources (LEDs), in all of the arrays, oriented substantially perpendicular to the central axis. Further, each LED in each row directs a respective light beam toward the central axis at an angle,  2 α. Recall, the primary facets have normals that are inclined to the axis at an angle, α. Thus, light from the LEDs that is reflected by the primary facets will travel substantially along the axis of the drill bit. 
     Preferably, as indicated above, there will be around seven rows of LEDs in each array. All of the LEDs in a same row can then be collectively directed to accommodate a specific angle, 2α. Specifically, it is important that this angle, 2α correspond to the particular primary facet configuration that is being imaged. Stated differently, because the primary facets of different drill bits can have different angle configurations (e.g. α 1 , α 2 , α 3 . . . α 7 ) the LEDs in the various rows of the array will direct light onto the primary facet at respectively different angles (e.g. 2α 2 , 2α 2 , 2α 3 . . . 2α 7 ). For discussion purposes, only three such rows and three correspondingly different primary facet configurations will be described. Accordingly, a first row of LEDs will direct light toward the drill bit at an angle 2α 1  for reflection from primary facets that have a normal inclined at an angle α 1  from the axis. Similarly, a second row will direct light toward the drill bit at an angle α 2 , for reflection from primary facets that have a normal inclined at an angle α 2  from the axis, and a third row will direct light toward the drill bit at an angle 2α 3  for reflection from primary facets having a normal inclined at an angle α 3  from the axis. 
     In the operation of the present invention, a drill bit is advanced to an axial position in front of the silhouetting light source. The resultant shadow of the drill bit is then used to create a camera image which identifies the length of the drill bit and indicates the axial movement necessary to bring the drill bit into focus. Next, a row of LEDs is selected which corresponds to the angle α n  (n=1, 2, 3 . . . 7) configuration of the drill bit&#39;s primary facets. Specifically, the LEDs in this row will direct light toward the primary facets at an angle 2α n . The same rows, in each of the different pairs of arrays in the ring, are then selectively illuminated until the pair giving the clearest image of the primary facets is identified. Using this image, the drill bit is rotated to establish a gross rotational position for the drill bit on the axis that will be accurate to within approximately eight degrees (i.e. ±40°). The light source for illuminating the margin is then activated to fine tune the rotation of the drill bit. Specifically, by using reflections from the margin of the drill bit, the drill bit can be rotated into a precise rotational position which is accurate to within approximately one half of a degree (i.e. ±0.250°). The spatial orientation of the drill bit is thus established. 
     Once the spatial orientation of the drill bit is established, the drill bit can be moved to a dimensionally calibrated grinding wheel where the primary facets can be ground to sharpen the drill bit. After grinding, the drill bit can be returned to a predetermined spatial orientation in the optical device of the present invention where both the primary and secondary facets of the drill bit can be inspected. The drill bit can then be returned to service. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which: 
     FIG. 1 is a perspective schematic view of the optical system of the present invention; 
     FIG. 2 is a side view of a drill bit; 
     FIG. 3 is a front view of the drill bit shown in FIG. 2; 
     FIG. 4 is a cartesian coordinate system describing the angel α as used for the present invention; 
     FIG. 5 is a perspective schematic view showing the relationship between an array of light sources, as used for the present invention, and the respective angle α n  between selected rows of light sources in the array and the drill bit; 
     FIG. 6 is a silhouette of the drill bit; 
     FIG. 7 shows an illumination of the primary facets of the drill bit; 
     FIG. 8 shows an illumination of a margin of the drill bit; and 
     FIG. 9 how illumination of the secondary facets of the drill bit. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring initially to FIG. 1 a device in accordance with the present invention is shown and is generally designated  10 . As shown, the device  10  is used to sequentially illuminate a drill bit  12  from different predetermined locations. The device  10  then receives the resultant reflections from the drill bit  12  to accurately and precisely position the drill bit  12 . For reference purposes, the drill bit  12  is shown to have a longitudinal axis  14  which extends along the length of the drill bit  12 . 
     In FIG. 1 the device  10  is shown to include a light source  16  that directs a beam of light along the beam path  18 . As intended for the device  10 , the beam path  18  will be substantially perpendicular to the axis  14  and will be located opposite the drill bit  12  from a camera  20 . Consequently, upon activation of the light source  16 , the camera  20  will receive a silhouette image of the drill bit  12 . Preferably, the light source  16  is an LED of a type well known in the pertinent art. 
     As also seen in FIG. 1, the device  10  includes a light source  22  that is positioned to surround the axis  14 . For the present invention, the light source  22  selectively directs light along beam paths  24  that are azimuthally oriented around the axis  14  (the beam path  24  in FIG. 1 is only exemplary). Depending on the configuration of the drill bit  12 , and the particular orientation of the beam path  24 , the light from light source  22  will be reflected from the drill bit  12  in a direction along the axis  14  toward a camera  26 . Thus, the camera  26  will receive a specular reflection from the drill bit  12 . 
     FIG. 1 also shows a light source  28  that is positioned to direct light toward the drill bit  12  along a beam path  30  that is substantially perpendicular to the axis  14 . As intended for the present invention, the light from light source  28  will be reflected toward the camera  20  along the beam path  18 ′. Note that the beam path  18 ′ is effectively an extension of the beam path  18 , and that the beam path  30  is coplanar with the beam path  18 ′ and forms an angle β therewith. Further, the device  10  includes a pair of light sources  32   a  and  32   b  that, respectively, direct light along colinear beam paths  34   a  and  34   b  for reflection from the drill bit  12 . The beam paths  34   a  and  34   b  are both substantially perpendicular to the axis  14  and the reflection of these beam paths  34   a  and  34   b  is directed from drill bit  12  along the axis  14  and toward camera  26 . As shown, the beam path  34   a  forms an angle θ a  with beam path  18  and the beam path  34   b  forms an angle θ b  with the beam path  18 ′. For purposes of the present invention, the light source  28  and the light sources  32   a  and  32   b  are preferably LEDs. 
     In FIG. 2, the component parts of a drill bit  12  are shown in more detail. Specifically, as shown, a typical drill bit  12  is formed with a tip  36  that has two primary facets  38   a  and  38   b , and two secondary facets  40   a  and  40   b . Additionally, there are helical shaped flutes  42  which extend generally along the shank of the drill bit  12  and are bordered by a margin  44 . As perhaps best seen in FIG. 3, both of the primary facets  38   a  and  38   b  are positioned astride a diametrical extension line  46  and are located opposite the tip  36  from each other. The secondary facets  40   a  and  40   b  are juxtaposed respectively with primary facets  38   a  and  38   b  and are also positioned astride the extension line  46 . Another diametrical extension line  48  also separates the facets such that primary facet  38   a  is opposite extension line  46  from the secondary facet  40   a  and is opposite extension line  48  from the secondary facet  40   b . Similarly, primary facet  38   b  is opposite extension line  46  from the secondary facet  40   b  and is opposite extension line  48  from the secondary facet  40   a.    
     It is an important aspect of the present invention that any normal  50  to a primary facet  38  will be inclined at an angle α to the axis  14 . Specifically, the angle α is inclined such that α=cos −1  (1/(1+tan 2 (φ)+tan 2 (ψ))) where, in a Cartesian coordinate system, α is an angle with the z axis, φ is an angle of rotation about the x axis, and ψ is an angle of rotation about the y axis. A geometrical representation of the relationship between the angles α, φ and ψ is shown in FIG.  4 . As appreciated by the present invention, the angle α can vary from one configuration for drill bit  12  to another. Importantly, however, each drill bit  12  will have an identifiable angle α. Consequently, in order for light to be specularly reflected from a primary facet  38 , along the axis  14  toward camera  26 , it is necessary that the light source  22  be able to direct the beam path  24  toward a primary facet  38  with an angle of incidence equal to α. Specifically, in accordance with the general laws of reflection which require that the angle of incidence (i.e. an angle α between beam path  24  and normal  50 ) be equal to the angle of reflection (i.e. an angle α between normal  50  and the axis  14 ), the beam path  24  needs to be inclined at an angle 2α relative to the axis  14  in order for there to be a specular reflection from primary facet  38  along the axis  14 . To accomplish this, the light source  22  of the device  10  is really a plurality of individual light sources. 
     Returning to FIG. 1, it is seen that the light source  22  is formed as a ring  52  which surrounds and is centered on the axis  14 . Further, the ring  52  generally defines a plane which is perpendicular to the axis  14 . As best seen in FIG. 1, the light source  22  includes a plurality of tilted arrays  54 . Preferably, there are sixteen separate arrays  54  in light source  22  (of which the arrays  54   a ,  54   b  and  54   c  are exemplary) that are arranged as diametrically opposed pairs. Accordingly, there are preferably eight such pairs of the arrays  54 . 
     By cross referencing FIG. 5 with FIG. 1, it will be appreciated that each of the arrays  54  includes a plurality of individual light sources  58  that are respectively arranged in rows  56  (of which the rows  56   a ,  56   b  and  56   c  are only exemplary). Importantly, each row  56  is oriented to be substantially perpendicular to the axis  14 , and all of the individual light sources  58  in a single row  56  are positioned to direct light along beam paths  24  that are inclined at an angle 2α n  to the axis  14 . For example, all of the individual light sources  58  in row  56   a  of the array  54   a  will direct light generally along the beam path  24   a  which is inclined at an angle 2α 1  to the axis  14 . Similarly, all of the individual light sources  58  in row  56   b  of the array  54   a  will direct light generally along the beam path  24   b  which is inclined at an angle 2α 3  to the axis  14 . Likewise, all of the individual light sources  58  in row  56   c  of the array  54   a  will direct light generally along the beam path  24   c  which is inclined at an angle 2α 7  to the axis  14 . This same arrangement applies equally to all of the arrays  54 . Additionally, FIG. 5 indicates that each array  54  will be tilted at an angle β relative to the axis  14  and that each row  56  will include a diffuser  59 . Specifically, the diffuser  59  causes light from the individual light sources  58  in a row  56  to diffuse together so that light from a row  56  is incident on the drill bit  12  as a single beam. The diffuser  59  can be of any type well known in the art. Further, recall that each array  54  is paired with another array  54  that are positioned diametrically across the axis  14  from each other. Despite the differences in the angle α n , between different rows  56 , all of the individual light sources  58  in an array  54  are directed toward substantially the same point on the axis  14  (e.g. tip  36  of drill bit  12 ). As intended for the present invention, the individual light sources  58  in the arrays  54  are, preferably, LEDs of a type well known in the pertinent art. 
     OPERATION 
     In the operation of the device  10 , the drill bit  12  is mounted on a base (not shown) and is advanced in a direction along its longitudinal axis  14  and into an axial position  60  (see FIG.  1 ). The light source  16  is then activated and the camera  20  receives a silhouette image of the drill bit  12  (see FIG.  6 ). Based on the actual position of the drill bit  12  as detected by the camera  20 , in comparison with the desired position of the drill bit  12 , it can be determined how much of the drill bit  12  needs to be moved in order to sharpen the drill bit  12 . Further, it can be determined whether the drill bit  12  even has sufficient material remaining for a grinding operation and, if not, whether the drill bit  12  should be discarded. 
     If a grinding operation can be performed, the drill bit  12  is advanced from the axial position  60  into an axial position  62  which effectively corresponds to the coincident focal points of the individual light sources  58  in the light source  22 . While the drill bit  12  is in the position  62 , a specific row  56  of individual light sources  58  is to be activated. In particular, the row  56  that is activated will depend on the configuration of the drill bit  12 . Importantly, the activated row  56  needs to have beam paths  24  at the specific angle 2α n  that is required to achieve specular reflections from the primary facets  38   a  and  38   b  of the drill bit  12 . Using the proper row  56 , diametrically opposed pairs of arrays  54  are sequentially activated in order to identify the particular pair of arrays  54  that best illuminate the primary facets  38   a  and  38   b  (see FIG.  7 ). The drill bit  12  can then be rotated about its axis  14  to establish a gross rotational position for the drill bit  12  on the axis  14 . Specifically, the extension line  46  can be of considerable use in establishing the gross rotational position. 
     Once a gross rotational position has been established for the drill bit  12 , the drill bit  12  is located in the axial position  60  to achieve even greater precision in the positioning and orientation of the drill bit  12 . Specifically, while in the axial position  60 , the drill bit  12  is illuminated by the light source  28  to create an image of the margin  44  (see FIG.  8 ). The image of margin  44  that is created will be observed by the camera  20 . Based on the known geometry of the drill bit  12 , the image of margin  44  can be used to precisely rotate the drill bit  12 , as necessary, into a desired spatial orientation. In this spatial orientation, the drill bit  12  can be moved into a grinding tool (not shown) where the primary facets  38   a  and  38   b  are ground down to sharpen the drill bit  12 . 
     After the drill bit  12  has been sharpened, it can be returned to the positions  60  and  62  for inspection. To do this the light source  16  and camera  20  are used to check the profile and axial position of the drill bit  12  in axial position  60 . The light source  22  and camera  26  are then used to check the primary facets  38   a  and  38   b  with the drill bit  12  in axial position  62 . Additionally, the light sources  32   a  and  32   b  can be used with camera  26  to check and inspect the secondary facets  40   a  and  40   b  (see FIG.  9 ). 
     While the particular Optical Inspection Device as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.