Abstract:
A measurement system including a stage having a first piece and a second piece that are movable with respect to one another. A digital scale is integrated in the first piece and a detector is integrated in the second piece at a position suitable to detect movement with respect to the digital scale. The detector creates a signal based upon relative movement between the digital scale and the detector. A display integrated in the second piece receives the signal from the detector and displays a reading of the relative movement thus measured.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/434,759, filed Dec. 17, 2002. 
     
    
     
       BACKGROUND OF INVENTION  
         [0002]    1. Technical Field  
           [0003]    The present invention relates generally to means for measuring between at least two relatively movable contact members, and more particularly to an indicating means including a transducer which is responsive to the contact member movement for producing in an electrical circuit an indication of the distance between the contact members.  
           [0004]    2. Background Art  
           [0005]    In many manufacturing and laboratory processes a very high number of stages are still measured by mechanical micrometer. Unfortunately, this poses a number of disadvantages. For example, micrometer reading requires interpretation with the human eye. The mechanically engraved scale is not only crude in displaying the measurement, but also quite difficult to read. The same displacement can produce different readings when the angle of observation changes. A more serious problem is that the mechanical micrometer has backlash and the clockwise and counterclockwise turning of the micrometer can therefore produce different readings even though the amount of actual displacement is the same. It is also very difficult to get micrometer readings when stages have to be operated in low light or dark conditions, as is necessary or highly desirable in some applications. FIG. 1 (prior art) provides examples of various linear stages with micrometers attached, and FIG. 2 (prior art) provides an example of a linear slide with multiple moving stages.  
           [0006]    The shortcomings of the mechanically engraved scale are even more serious for a rotary stage, tilt stage, gimbal mount, or goniometer. Some rotary stages today are equipped with a mechanical micrometer on the side. The amount of the rotation is then measured by reading the scale on the micrometer, which is in a linear dimension, and this is then converted to an angular measurement. However, this is not only time consuming but often also highly inaccurate. For instance, when the rotation angle is large the cosine error becomes significant. FIG. 3 (prior art) provides examples of various rotary stages with engraved scales, and FIG. 4 (background art) depicts such a rotary stage with a mechanically engraved scale.  
           [0007]    Digital scales have been used in mechanical stages and slides for some time. However, up to now, almost all of these require a separate signal detection unit, interface cable, and personal computer (PC) board. The displacement of the stage is then displayed on a computer screen. The cost of these stages is high, typically in the range of several thousand dollars to over ten thousand dollars for a single axis displacement stage. Integrated signal-and-display stages are not offered and it is especially notable that we know of no rotary stages equipped with a digital scale readout that are presently available.  
         SUMMARY OF INVENTION  
         [0008]    Briefly, one preferred embodiment of the present invention is a measurement system. A stage having a first piece and a second piece is provided, wherein at least one of these pieces is are movable with respect to the other. A digital scale in integrated in the first piece and a detector is integrated in the second piece at a position suitable to detect movement with respect to the digital scale and create a signal based upon this relative movement. A display integrated in the second piece then receives the signal from the detector and displays a reading of the relative movement.  
           [0009]    An advantage of the present invention is that it provides an integrated signal-and-display stage.  
           [0010]    Another advantage of the invention is that it employs electronic detection and display, thereby minimizing the human interpretation errors and mechanical errors that mechanical stages suffer from.  
           [0011]    Another advantage of the invention is that it encompasses linear stages and slides as well as rotary stages, tilt stages, gimbal mounts, and goniometers.  
           [0012]    Another advantage of the invention is that it may include functions such as position reset, position preset, position difference between a reference position and a measured position, and conversion between units of measurement.  
           [0013]    And another advantage of the invention is that it is economical to construct and use.  
           [0014]    These and other objects and advantages of the present invention will become clear to those skilled in the art in view of the description of the best presently known mode of carrying out the invention and the industrial applicability of the preferred embodiment as described herein and as illustrated in the several figures of the drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0015]    The purposes and advantages of the present invention will be apparent from the following detailed description in conjunction with the appended figures of drawings in which:  
         [0016]    [0016]FIG. 1 (prior art) shows linear stage examples with mechanical micrometers attached;  
         [0017]    [0017]FIG. 2 (prior art) shows a linear slide example with multiple stages;  
         [0018]    [0018]FIG. 3 (prior art) shows rotary stage examples with engraved scales on the side and mechanical micrometers;  
         [0019]    [0019]FIG. 4 (background art) shows a rotary stage example with a mechanically engraved scale on the sides;  
         [0020]    [0020]FIGS. 5 a - b  shows an embodiment of a linear stage according to the present invention that is equipped with a digital scale, wherein FIG. 5 a  shows a top piece in left side and plan bottom views and FIG. 5 b  shows a bottom piece in left side, plan, and right side top views as well as in a front plan view;  
         [0021]    [0021]FIG. 6 shows an embodiment of a rotary stage according to the present invention that is equipped with a linear digital scale attached at the edge of the stage; and  
         [0022]    [0022]FIG. 7 shows an embodiment of a rotary stage according to the present invention that employs a digital disk mounted at the inner surfaces. 
     
    
       [0023]    In the various figures of the drawings, like references are used to denote like or similar elements or steps.  
       DETAILED DESCRIPTION  
       [0024]    A preferred embodiment of the present invention is a digital scale for linear or rotary stages. As illustrated in the various drawings herein, and particularly in the views of FIGS. 5 a - b,    6  and  7 , preferred embodiments of the invention are depicted by the general reference character  10 .  
         [0025]    An objective way of getting the reading of a true position (or rotation) is to use a digitally reading scale with an integrated display. The principle of operation of such a scale can be either magnetic, holographic grating, inductive, or capacitive and, in general, can be embodied in a tape form factor. All of these examples of scales are accurate to within a few microns, and are presently available in the market. What is not available and for which there is a long standing and severely felt need, however, are stages with such scales and their displays integrated therein. Such can provide accurate measurement for the position of a linear stage or the rotation of a rotary stage, and thus overcome the numerous disadvantages of the prior art stages discussed above.  
         [0026]    The digital scales used may be flexible and can be mounted very close to the axis of the motion, thus minimizing the Abbe offset error. These digital scales can also be mounted either at an outer or inner surface of the stage (either on a moving part or a stationary part), with the detector on the surface of a counterpart. Mounting on an inner surface has advantages from cosmetic and cleanliness points of view, and in some applications may provide a degree of protection against physical wear and damage. In addition, this reduces the chance for getting dust particles in between a scale and its detector.  
         [0027]    [0027]FIGS. 5 a - b  present various views of a stage  10  according to the present invention. The stage  10  here is a linear stage  12  that is equipped with a digital scale  14 , a detector  16 , and a display  18  which is connected with the detector  16  by a signal wire  20 . The linear stage  12  can be defined as having a top piece  22  and a bottom piece  24 . This definition is useful when considering the figures and the examples presented herein, but should not be taken to imply any form of limitation. Some purists hold that a “stage” is the portion of the mechanism that moves and that the stationary part of the mechanism is a base or basepiece. More generally, however, the total mechanism is spoken of as being a stage. This better encompasses the fact that both pieces, e.g., top and bottom, table and base, etc. may both move and that any measurement between them then is a relative measurement. This also helps avoid the incorrect implication that the a digital scale  14  is always placed in the moving “stage” and the detector  16  and display  18  are always placed in the “basepiece.” 
         [0028]    Continuing with FIGS. 5 a - b,  the top piece  22  in this embodiment includes the digital scale  14 , and the bottom piece  24  includes the detector  16  and the display  18 . An optional, conventional mechanical adjustable stop  26  is also shown here.  
         [0029]    In use, the top piece  22  of the linear stage  12  here can be moved left or right, thus moving the digital scale  14  relative to the detector  16 . The detector  36  then produces and sends a signal to the display  18  via the signal wire  20 . The adjustable stop  26  can be used to set a rightmost position  28  for travel of the top piece  22 . The display  18  can then be set to read zero when the top piece  22  is in the rightmost position  28 , and the display  18  will display a relative measurement or displacement when the top piece  22  is moved away from the rightmost position  28 .  
         [0030]    [0030]FIG. 6 presents another embodiment of a stage  10  according to the present invention. The stage  10  here is a rotary stage  32  that is equipped with a digital scale  34 , a detector  36 , and a display  38  which is connected with the detector  36  by a signal wire  40 . This rotary stage  32  can also be defined as having a top piece  42  and a bottom piece  44 , with the top piece  42  including the digital scale  34  and the bottom piece  44  including the detector  36  and the display  38 .  
         [0031]    In use, the top piece  42  of the rotary stage  32  here can be turned clockwise or counter clockwise, and in this embodiment the top piece  42  can even be revolved completely, many times, in either direction. This moves the digital scale  34  relative to the detector  36 , causing the detector  36  to send a signal to the display  38  via the signal wire  40 . Of course, the top piece  42  can also be held fixed and the bottom piece  44  be rotated, or both pieces  42 ,  44  can be rotated.  
         [0032]    The detector  36  and the display  38  here can be the same as the detector  16  and the display  18  of the linear stage  12  in FIGS. 5 a - b,  but this need not necessarily be the case. The detector  36  will, however, display measurements of angular position whereas the display  18  of the linear stage  12  will display measurements of linear position. The digital scale  34  here may even have close similarity to the digital scale  14  of the linear stage  12 . For instance, as noted above, digital scales can be embodied in a tape or other flexible form factor. The digital scale  34  here can therefore be simply an encircling application of the very same component used in the digital scale  14  in flat application.  
         [0033]    [0033]FIG. 7 presents yet another embodiment of a stage  10  according to the present invention. The stage  10  here is a rotary stage  52 , but one using a different form of digital scale  54  than the digital scale  34  of the rotary stage  32  in FIG. 6. A detector  56  and a display  58  connected by a signal wire  60  are also provided here. The detector  56  necessarily is one suitable for use with the particular digital scale  54  here, but the display  58  may potentially be the same as the displays  18  and  38 .  
         [0034]    The rotary stage  52  here can also be defined as having a top piece  62  and a bottom piece  64 . The top piece  62  here, show turned over to better depict its elements, includes the detector  56  and the display  58 . The bottom piece  64  has an outer housing  66  and an inner race  68 , and the inner race  68  includes the digital scale  54 .  
         [0035]    In use, either the top piece  62  or the inner race  68  (or both) can be turned clockwise or counter clockwise, possibly even revolved completely multiple times. This moves the digital scale  54  and the detector  56  relative to one another, causing the detector  56  to send a signal to the display  58  via the signal wire  60 . The outer housing  66  of the bottom piece  64  may or may not move, as desired, with any such movement having no effect on the measurement being made between the top piece  62  and the inner race  68 .  
         [0036]    Considering the displays  18 ,  38 ,  58  now, these can be illuminated, permitting use in low light so users do not have to turn on a light to take a reading. They can also, optionally, allow users to preset an initial position as a reference, and to then measure displacement from this reference position, to reset a reference position with a targeted value and to measure the difference position from there (“+” direction and “−” direction, etc.), and to change between different units, e.g., millimeters or inches for linear displacement and degrees or radians for rotation measurement. Similarly, the display can change scales, e.g., millimeters to centimeters, degrees to minutes or seconds, and radians to milli-radians, etc.. The displays  18 ,  38 ,  58  can even further provide an input/output connector for the user to output the measured result to a computer, to load presets, to set units, etc. For example, the RS232 or other protocols can be used.  
         [0037]    To achieve these, and potential other capabilities, the displays  18 ,  38 ,  58  use at least a limited microprocessor. The stage  10  also has access to a power source to power the detectors  16 ,  36 ,  56  and the displays  18 ,  38 ,  58 . In the figures herein the microprocessor and power source have been treated as being integrated into the displays  18 ,  38 ,  58 , as will typically be the case. This, however, need not necessarily be the case. The microprocessor can be located elsewhere in the stage  10 , and connected to the detectors  16 ,  36 ,  56  and displays  18 ,  38 ,  58  in straightforward manner, and the power source can be located elsewhere in the stage  10  or even outside of it.  
         [0038]    Without limitation, some suitable candidate types for the displays  18 ,  38 ,  58  are liquid crystal or light emitting diode (LED) based units. These typically have limited microprocessor capability already provided to handle their visual presentation role, and it is a simple matter to employ or to enhance this to also handle any other desired microprocessor roles as well.  
         [0039]    Various suitable candidate types for the power source also exist. For example, also without limitation, batteries, local generation, and external sources may be employed. The batteries used for this may be replaceable, rechargeable, or permanent. For instance, replaceable or permanent (e.g., lithium based, long-life type) batteries will typically be best suited when used with low-power type displays  18 ,  38 ,  58 , such as liquid crystal based units. Conversely, rechargeable batteries or other types of power sources will typically be best suited when used with higher-power type displays  18 ,  38 ,  58 , such as LED based units.  
         [0040]    Local generation of power is also suitable for use in some embodiments of the stage  10 . Some examples here include photo generation cells, often called solar cells, but also usable in many other ambient light conditions, and movement based generation. Since the stage  10  is by its vary nature subject to movement, this may be used to generate the small amounts of power it needs. For instance, a coil and magnetic field can be used to form a generator, or a piezoelectric device and a storage mechanism, such as a capacitor, can be used.  
         [0041]    External power sources may also be employed. One common example is conventional “plug into the wall” type sources. Another example is parasitic “leaching” of power from a system used in concert with the stage  10 . For instance, it was noted above that an interface (e.g., RS232, USB, etc.) can be present and used to permit communication with an external computer. Power for the relatively minor needs of the stage  10  can be obtained from such an interface.  
         [0042]    The particular design details of the microprocessors and the power sources are, of course, not critical to the underlying invention here, but we have gone into some detail on possible candidates for them to emphasize the invention&#39;s versatility and wide range of potential options.  
         [0043]    While various embodiments have been described above, it should be understood that they have been presented by way of example only, and that the breadth and scope of the invention should therefore not be limited by any of the above described exemplary embodiments, but instead defined only in accordance with the following claims and their equivalents.