Abstract:
An optical reader is provided for reading an image provided on a surface. The optical reader has at least one light source and a first lens configured to focus and diffuse light from the at least one light source onto an image. The optical reader also has at least one sensor, and a second lens configured to receive a reflection of the focused and diffused light from the image and direct it to the at least one sensor.

Description:
TECHNICAL FIELD  
       [0001]    The present disclosure is directed generally to an optical reader, and more particularly, to an optical reader having an integral lens and diffuser. 
       BACKGROUND  
       [0002]    Many construction and earthmoving machines use a hydraulic or pneumatic cylinder for moving a work tool such as a bucket, blade, or ripper. The cylinder typically includes a tube and a piston assembly arranged within the tube to form two separate pressure chambers. The chambers are selectively supplied with pressurized fluid and drained of the pressurized fluid to cause the piston assembly to displace within the tube and assist the movement of the work tool. During operation of a machine, it can be important to know the position of the piston relative to the tube so that movement of the work tool can be precisely controlled. 
         [0003]    Historically, barcodes have been marked on cylinder pistons to locate the position of the piston relative to the tube. In particular, the piston is etched with non-repeating segments of code, each of which correspond to a different location of the piston relative to the tube. In operation, a sensor is provided within the tube adjacent the barcode to identify a particular segment of the code. One such example is described in pending US Patent Publication No. US2006/0022047 (the publication) by Sewell et al., published Feb. 2, 2006. The publication describes an optical reader which comprises two light emitting diodes (LEDs), two lenses, a diffuser, and an array of photosensors. The LEDs provide light that is received and focused by a lens onto the diffuser. The diffuser spreads and transforms the light into a form that adequately illuminates the bar code. The second lens receives light reflected off of the bar code and focuses it onto the array of photosensors. The photosensors then generate a signal indicative of a position of a piston. 
         [0004]    Although this configuration is quite effective for reading the barcode etched on the piston to determine the position of the piston, the utilization of a separate diffuser may be inefficient and burdensome. In particular, a separate diffuser can increase assembly complexity and cost of the reader. 
         [0005]    The disclosed optical reader is directed to overcoming one or more of the problems set forth above. 
       SUMMARY OF THE INVENTION  
       [0006]    In one aspect, the present disclosure is directed toward an optical reader. The optical reader includes at least one light source and a first lens configured to focus and diffuse light from the at least one light source onto an image. The optical reader also includes at least one sensor, and a second lens configured to receive a reflection of the focused and diffused light from the image and direct it to the at least one sensor. 
         [0007]    Consistent with a further aspect of the disclosure, a method is also provided for reading an image provided on a surface. The method includes producing light, and simultaneously focusing and diffusing the produced light onto the image. The method also includes focusing a reflection of the diffused light from the image, receiving the focused reflection, and determining a position of the surface based on the received focused reflection. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0008]      FIG. 1  is a block diagram illustration of an exemplary disclosed positioning system; and 
           [0009]      FIG. 2  is a perspective view cross-sectional illustration of an exemplary disclosed reader for use with the positioning system of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION  
       [0010]      FIG. 1  illustrates a cylinder  10  and a system  12  for monitoring and controlling the expansion and retraction of cylinder  10 . The expansion and retraction of cylinder  10  may function to assist the movement of a work tool such as a bucket, blade, or ripper (not shown). For example, cylinder  10  may include a tube  14  operatively connected to the work tool and a piston  16  operatively connected to an associated machine. Piston  16  may be arranged within tube  14  to form two separated pressure chambers (not shown). The pressure chambers may be selectively supplied with pressurized fluid and drained of the pressurized fluid to cause piston  16  to displace within tube  14 , thereby changing the effective length of cylinder  10 . The expansion and retraction of cylinder  10  may assist in moving the work tool relative to the machine. 
         [0011]    Piston  16  may include a conventional thermally sprayed outer surface with a plurality of markings  18  that indicate the position of piston  16  in relation to tube  14 . Markings  18  may include, for example, a barcode. It should be understood that markings  18  may be formed by a high intensity laser that selectively exposes portions of the surface to radiation and may represent binary coded information in the sense that the marks, by being dark or light, represent 0s or 1s. In addition, markings  18  may represent encoded information based on numbers calculated with a random number generator, and may be grouped into subsets, each of which may correspond to a particular piston position. It is contemplated that markings  18  may be applied to piston  16  in a manner other than etching, if desired. 
         [0012]    System  12  may be used for monitoring and/or controlling the linear movement of piston  16  in relation to tube  14 . It should be understood that system  12  may include a reader  20 , which may be configured to read markings  18  on the surface of piston  16 . Additionally, system  12  may include a user interface  22  configured to transmit data to and receive inputs from a user. Furthermore, system  12  may include a mechanical control  24  for physically controlling the expansion and retraction of cylinder  10 . Yet another element that may be included in system  12  is a processor  28  configured to process data received from reader  20  and the user and send commands to mechanical control  24 . 
         [0013]    In a disclosed exemplary embodiment, reader  20  may be attached to cylinder  10  through an opening  30  in tube  14 . Opening  30  may be sized and shaped in such a manner that when reader  20  is attached to tube  14 , the markings  18  that are directly adjacent to reader  20  may be exposed only to light emitted from reader  20 . As illustrated in  FIG. 2 , reader  20  may include a housing  32  enclosing a plurality of optical emitters  34  and  36 , a first lens  38 , a second lens  40 , a sensor  42 , a circuit  44 , and a support  46 . 
         [0014]    Optical emitters  34  and  36  maybe used to illuminate the subset of markings  18  by producing light  48 . It should be understood that optical emitters  34  and  36  may be any kind of radiation producing sources including, for example, light emitting diodes (LEDs). In addition, light  48  may be produced at any frequency including infrared frequencies. It is contemplated that reader  20  may alternatively include only one LED, if desired. 
         [0015]    Light  48  emitted from LEDs  34  and  36  may consist of divergent beams. In this state, the majority of light  48  may not reach markings  18 . Lens  38  may control and transform light  48  by bending and focusing the diverging beams in the direction of markings  18 . Focusing the beams in the direction of markings  18  may increase the percentage of light  48  that illuminates markings  18 . The greater percentage of light  48  reaching markings  18  may increase the radiance value of the light illuminating markings  18 , resulting in an increased signal to noise ratio and an increased measurement accuracy of reader  20 . 
         [0016]    Lens  38  may be manufactured from an acrylic material through, for example, an injection molding process and/or a milling process. In one example, lens  38  may be milled from rod shaped stock. The rod shaped stock may have a diameter of about 15 millimeters and may be milled to produce two opposing flat sides about 3 millimeters apart. The opposing flat sides may provide a means to mount the lens in reader  20  while light  48  may be passed through the cylindrical surfaces that remain unchanged. It should be understood that any number of transparent materials including glass may alternatively be used. 
         [0017]    Light  48  may need to be modified before it illuminates markings  18 . This is because the surface upon which markings  18  are engraved, may in general, consist of randomly oriented surface imperfections. When illuminated by a non-diffuse wavefront, only imperfections of a specific orientation may specularly reflect light through second lens  40 . The specularly reflected light may appear as glints in the image plane of sensor  42 . The position of the imperfections reflecting in this manner may vary randomly across the illuminated region and hence create spatially random image noise. The effect may degrade the image formed in the plane at sensor  42  and may reduce the accuracy of reader  20 . 
         [0018]    The above-mentioned image noise may be significantly suppressed by illuminating markings  18  with a diffuse beam of light. Under these conditions, imperfections on the surface of piston  16  may be illuminated over a range of angles of incidence thereby reducing the orientation specific image noise. This may be accomplished by diffusing focused light  48  as it passes through lens  38 . Light  48  may exit lens  38  through a surface  50 , which may be modified to create a predetermined angle of divergence, as well as a substantially equal intensity of light  48  over a range of incident angles throughout the entire subset of markings  18 . Surface  50  may include one of the unchanged cylindrical surfaces described above. In addition, it should be noted that the use of diffuse illumination may reduce the macroscopic variation in intensity resulting from the variation in the angle of incidence over the illuminated region due to the geometric form of the object. The latter may be a cylindrical surface for the application described. 
         [0019]    The angle of divergence is a measure of the spread of light caused by a diffusing surface and is correlated to the range of angles of incidence over which a given portion of the surface is illuminated. To a first order, the suppression of the surface spatial noise (described earlier) increases as this angular range increases. It may also be recognized that as the angle of divergence increases, the area of illumination also increases and the mean radiance of light  48  decreases. It may be important that the latter should not decrease below a level for which sensor  42  is able to effectively detect reflected light  52 . Therefore, there may be a tradeoff between the divergence (and hence suppression of surface induced noise) and the signal to noise ratio of the detected bar code signal. In one example, this maximum angle of divergence may be limited to about 30 degrees. 
         [0020]    One method used to modify surface  50  may include abrading surface  50 . Materials such as acid, sandpaper, or other known scouring tools may be used to abrade surface  50 . In order to achieve an accurate reading, the abrasion of surface  50  may need to be substantially consistent. This consistency may be accomplished by requiring that the angle, pattern, depth, and density of cuts resulting from the abrasion process be consistent over the entirety of surface  50 . In one example, these homogenous cuts may be made across surface  50  by applying sandpaper having a grit of about 150-600 in a uniform, single direction along the length of surface  50  at a substantially constant pressure for about 10 strokes. A small jig or other machine (not shown) may be used to generate the repetitive motion at the constant pressure. 
         [0021]    Physical characteristics of the abrasive material used to modify surface  50  may affect the angle of divergence. For example, as the grit value of the sandpaper increases, the diffusing effect may weaken. This may lead to smaller angles of divergence. A measurement of the roughness of surface  50  may be pre-calibrated against known diffusing angles and may be used to monitor the diffuser manufacturing process. One possible way to measure the roughness of surface  50  might be to utilize a surface gauge (not shown). The surface gauge may measure the center line average (CLA) of depth of the cuts in surface  50 . 
         [0022]    Another method used to modify surface  50  may include covering surface  50  with a translucent material  150  which may be a layer of polyester film or paper. The diffusion ability of the different translucent materials may be determined by measuring the angle of divergence of light passing through the materials. This measurement may also be useful as an alternative to the CLA measurement described above for determining the preferred roughness of surface  50  when using abrading techniques. 
         [0023]    Yet another method alternatively used to modify surface  50  may include employing integral protrusions  250  on surface  50 . The protrusions may be created in the same injection molding process used to create lens  38  or through a separate additional process. Just as in the previously described diffuser creating methods, the diffusing ability of surface  50  may require consistency over surface  50 . This consistency may be accomplished by manufacturing protrusions having substantially identical shapes and sizes. In addition, the location and spacing between the protrusions may be consistent throughout surface  50 . 
         [0024]    First lens  38  may transmit light  48  to a subset of markings  18  through an opening  54 . It should be noted that opening  54  may be closed by a planar transparent optical window  56  to provide protection for the reader components. 
         [0025]    Second lens  40  may receive reflected light  52  from the subset of markings  18  and may focus it onto sensor  42 . Lens  40  may be a unitary object manufactured in a manner similar to lens  38 , or it may include a prefabricated array of graded index lenses, if desired. 
         [0026]    In response to receiving reflected light  52 , sensor  42  may generate and transmit a signal to processor  28  (referring to  FIG. 1 ) via circuit  44 . It should be understood that sensor  42  may include an array of photosensors, if desired. In one exemplary embodiment, the photosensors may be complementary metal oxide semiconductor (CMOS) photosensors. 
         [0027]    User interface  22  may include components that cooperate to display and transmit data. In particular, user interface  22  may include for example, a display or monitor and a keyboard or other data entry device. User interface  22  may display on the monitor, data generated by reader  20  and transmit user-inputted data to processor  28 . 
         [0028]    Processor  28  may embody a conventional microprocessor, computer, or digital signal processor and include associated circuitry. Processor  28  may be operationally connected to reader  20 , user interface  22 , and mechanical control  24  to receive and transmit data. 
         [0029]    Mechanical control  24  may physically control the extension and retraction of piston  16 . Specifically, mechanical control  24  may include an assembly of valves that regulate the flow of pressurized fluids to and from the chambers of cylinder  10 . In response to the pressurized fluids, piston  16  may be urged to extend or retract relative to tube  14 . 
       INDUSTRIAL APPLICABILITY  
       [0030]    The disclosed optical reader may provide a simple, inexpensive, and reliable way to determine the position of a moving element. In particular, the disclosed optical reader may utilize a single integral lens/diffuser component to determine the position of a piston relative to a tube housing the piston. The operation of system  12  will now be explained. 
         [0031]    Cylinder  10  may be activated to extend or retract a connected machine work tool (not shown) relative to the machine. During the extension or retraction of the connected machine work tool, LEDs  34  and  36  within reader  20  may emit light  48 . First lens  38  may bend and focus divergent beams of light  48  as it passes through first lens  38 . Substantially simultaneously, as light  48  exits first lens  38 , it may pass through modified surface  50  and be diffused. The diffused light  48  may pass through opening  54  of reader  20  and uniformly illuminate a subset of markings  18 . 
         [0032]    Light  52  reflected off of the subset of markings  18 , may pass through opening  54  of reader  20  and into lens  40 . Lens  40  may then focus light  52  onto sensor  42 . Once sensor  42  receives reflected light  52 , it may generate a signal indicative of the subset of markings  18  that were illuminated by light  48  and transmit the signal to processor  28  via circuit  44 . In response to the signal, processor  28  may determine a position of piston  16  and display the determined position on user interface  22 . In response to commands inputted to the processor  28  from user interface  22  and the identified position, processor  28  may supply control signals to mechanical control  24 , to thereby move piston  16 . 
         [0033]    Because the focusing and diffusing functions of optical reader  20  may be performed substantially simultaneously by a single modified lens, the number of components and the size of optical reader  20  may be reduced. In addition, the reduction of the number of components within optical reader  20  may decrease assembly complexity and associated cost and unreliability. 
         [0034]    It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed system without departing from the scope of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.