Abstract:
An optical sensor includes a transmitter that emits light rays. Transmitting optics are installed downstream of the transmitter. An adjustment device is operatively arranged for reversibly adjusting, in three spatial directions, the relative position of the transmitter and the transmitting optics. A receiver receives light rays. An evaluation unit evaluates the received signals that are present at the receiver output.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   The present application is a continuation of U.S. patent application Ser. No. 10/427,995 filed May 2, 2003 entitled “Optical Sensor,” to Armin Claus et al, and claiming priority to German Patent Application No. 102 19 529.3 filed May 2, 2002, the priority of which is also claimed herein. The contents of both of foregoing applications are incorporated herein by reference in their entirety. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to an optical sensor, and more particularly to an adjustable optical sensor. 
   2. Related Art 
   In general, optical sensors can be embodied as light barriers, light scanners and distance sensors. In particular, the optical sensors can be barcode readers for detecting barcodes or, in general, for detecting markings with contrasting patterns. 
   Optical sensors of this type generally use transmitting optics or a standard optical system for generating a beam with the transmitting light rays emitted by the transmitter. To generate the desired beam with the transmitting light rays, in particular for focusing the beam and guiding the rays along a specific beam axis, the transmitting optics must be aligned relatively precisely and reproducibly. 
   During the process of manufacturing the optical sensor, the transmitter and the transmitting optics are installed inside a housing with an integrated optical sensor by using production steps that are typically carried out manually. 
   An optical sensor of this type is described in German patent document 198 44 238 A1. The optical sensor embodied as barcode reader is integrated into a housing, and an insert can be inserted into the housing for accommodating the optical components. 
   The housing insert is provided with a hollow-cylindrical receptacle in which the transmitter and the transmitting optics are positioned, one behind the other and spaced apart. 
   The disadvantage of this arrangement is that the installation locations for the transmitter and the transmitting optics are preset, thus making it impossible to adjust the beam course for the transmitting light rays. In particular, no subsequent corrections are possible in case of a faulty installation position of the components, because the transmitter and transmitting optics normally must be glued on for securing them inside the receptacle. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to provide an optical sensor of the aforementioned type, which provides a reliable adjustment option with high flexibility for adjusting the beam guidance of the emitted light rays. 
   The above and other objects are accomplished according to the invention by the provision of an optical sensor comprising a transmitter that emits light rays, a receiver that receives light rays and an evaluation unit for evaluating the receiving signals present at the receiver output. An adjustment device is assigned to the transmitter, which permits a reversible adjustment in three spatial directions of the relative position of the transmitter and a transmitting optic installed downstream of the transmitter. 
   The device according to the invention makes it possible to preset the beam guidance of the transmitting light rays in a flexible manner. For this, the reversible adjustment is particularly advantageous because the beam guidance can be changed if necessary. 
   The beam profile for the transmitting light rays as well as their focussing position can be changed through adjusting the distance between transmitter and transmitting optics. A precise adjustment of the beam direction for the transmitting light rays is possible through positioning the transmitter or transmitting optics transversely to the transmitter axis. 
   The adjustment device of one advantageous embodiment comprises an optics holder in which the transmitting optics are positioned so as to be displaceable. In a first embodiment of the invention, the transmitting optics in the holder are positioned such that they can pivot in a plane that is oriented perpendicularly to the axis of the transmitting light beam, thus making it possible to adjust the beam direction of the transmitting light rays. The transmitter is positioned such that it can be displaced relative to the transmitting optics in order to preset the beam profile and focussing position of the transmitting light rays. 
   According to a particularly advantageous second embodiment of the invention, the transmitting optics inside the holder can be adjusted in all three spatial directions. As a result, the transmitter can be arranged locally secured inside the optical sensor. The beam direction in that case is preset through a pivoting movement of the optics holder transverse to the optical axis of the transmitter. Adjusting the beam profile and the focussing position is usefully achieved by deflection of the optics holder with respect to a predetermined reference point. 
   In each case, the optics holder is secured in a specified adjustment position with the aid of mechanical fixing and fastening systems, wherein the adjusted position can be released again at any time by activating the fixing and fastening systems. 
   In an exemplary embodiment, the present invention can be an optical sensor comprising: a transmitter that emits light rays; transmitting optics installed downstream of the transmitter; a receiver that receives light rays; an evaluation unit for evaluating the received signals that are present at the receiver output; and an adjustment device operatively arranged for reversibly adjusting, in three spatial directions, the relative position of the transmitter and the transmitting optics. 
   Further features and advantages of the invention, as well as the structure and operation of various embodiments of the invention, are described in detail below with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other features and advantages of the invention will be apparent from the following, more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings wherein like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. 
       FIG. 1  depicts a schematic representation of an exemplary embodiment of an optical sensor embodied as barcode reader according to the present invention; 
       FIG. 2  is a perspective representation of the adjustment device for the optical sensor according to  FIG. 1 ; 
       FIG. 3  depicts a cross section through the adjustment device according to  FIG. 2 ; 
       FIG. 4  is a perspective view of the optics holder for the adjustment device according to  FIGS. 2 and 3 ; 
       FIG. 5  illustrates a second exemplary embodiment of an adjustment device for an optical sensor; and 
       FIG. 6  is a longitudinal section through the adjustment device according to FIG.  5 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A preferred embodiment of the invention is discussed in detail below. While specific exemplary embodiments are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations can be used without parting from the spirit and scope of the invention. 
     FIG. 1  schematically shows the essential components of an optical sensor  1  according to the present invention, embodied as barcode reader. The optical sensor  1  is used for detecting barcodes  2  or, in general, for detecting markings with contrasting patterns. In principle, the optical sensor  1  can also be embodied as a light barrier, a light scanner, a distance sensor or the like. 
   The barcode reader according to  FIG. 1  comprises a transmitter  4  that emits light rays  3  and a receiver  6  that receives light rays  5 . The transmitter  4 , preferably a laser diode, is followed by transmitting optics  7  for generating a beam with the transmitting light rays  3  and focusing these rays. 
   The transmitting light rays  3  that are emitted by the transmitter  4  and the receiving light rays  5  that are reflected back by a barcode  2  are guided over a deflection unit. In an exemplary embodiment, the deflection unit is a motor-driven polygonal mirror wheel  8  with a predetermined number of facet-shaped mirror surfaces  9 . 
   As a result of the rotational movement of the polygonal mirror wheel  8 , the transmitting light rays  3  are periodically guided across a monitoring range  10 , which extends in a scanning plane. The monitoring range  10  extends across a specific angle region that is predetermined by the number of mirror surfaces  9  of the polygonal mirror wheel  8 . 
   The received signals present at the output of the receiver  6  are amplified in an amplifier that is not shown herein and evaluated in an evaluation unit  30 . 
   The received light rays  5 , which are reflected by the barcode  2 , are amplitude-modulated according to the sequence of black and white line elements in the barcode  2 . The received signals present at the output of the receiver  6  are correspondingly amplitude-modulated. The analog, amplitude-modulated receiving signals are evaluated in an evaluation unit  30  with a threshold value unit. Binary signal sequences are generated as a result, which are used to detect the barcode  2  through a comparison with stored contrast patterns for barcodss  2 . 
   A housing insert  11  is provided for accommodating the optical components of the optical sensor  1  according to the FIG.  1 . This insert is integrated into the optical sensor  1  housing, which is not shown herein.  FIGS. 2 and 3  show a detail of this housing insert  11  with an adjustment device for adjusting the relative position of the transmitter  4  and the transmitting optics  7 . 
   The adjustment device comprises an optics holder  12  for accommodating the transmitting optics  7 . The optics holder  12 , shown separately in  FIG. 4 , is positioned such that it can move on the housing insert  11 , whereas the transmitter  4  is locally secured to the housing insert  11 . 
   The detail of housing insert  11  that is shown in  FIGS. 2 and 3  shows another insert  13  with a bore  14 , in which the transmitter  4  is positioned. The housing insert  11  furthermore has a first and second holding part  15   a ,  15   b  for positioning the optics holder  12 . The holding parts  15   a ,  15   b  are essentially cube-shaped elements that project perpendicularly from the bottom of the housing insert  11 . 
   The optics holder  12  can be a molded plastic part, the center piece of which forms a support element  12   a  for accommodating the transmitting optics  7 . The transmitting optics  7  in this case are positioned on a bore  16  that extends through the support segment  12   a.    
   Holder segments  12   b ,  12   c  adjoin the longitudinal ends of the support segment  12   a  and also form components of the optics holder  12 . The first holder segment  12   b  has a plate-shaped design and is positioned so as to be displaceable on the level support surface for the first holding part  15   a , which extends in a vertical plane and is assigned to the insert  13 . The first holder segment  12   b  is connected via a flexible element  12   d  to the support segment  12   a . The flexible element  12   d  is formed by a structural weakness in the area where the wall thickness of the optics holder  12  is reduced considerably. The flexible element  12   d  forms a resilient spring that can serve to bend the support segment  12   a  relative to the first holder segment  12   b.    
   For a position change, the first holder segment  12   b  can be displaced on the support surface of the first holding part  15   a , wherein the displacement movement occurs in the vertical plane of the support surface and thus perpendicularly to the horizontally extending optical axis of the transmitter  4 . The second holder segment  12   c  is positioned such that it can turn on the second holding part  15   b . The second holder segment  12   c  is essentially a leg forming a right angle, wherein a rotary head  17  for the rotational positioning on the second holding part  15   b  is provided on the front end of the leg, at the free end of the second holder segment  12   c . The leg of the holder segment  12   c  forms a resilient element. 
   The optics holder  12  that is positioned on the holding parts  15   a ,  15   b  adjoins the front of the insert  13 , so that the transmitting optics  7  in the insert  13  are positioned at a predetermined distance to the transmitting optics  7  in the optics holder  12 . The first holder segment  12   b  is located inside a recess between the front portions of the insert  13  and the support surface of the holding part  15   a . A fixing screw  18  that extends through the side edge of insert  13  is used to secure the optics holder  12  in a certain adjustment position. The first holder segment  12   b  in this case is secured in the recess between insert  13  and the first holding part  15   a  by turning the fixing screw  18 . 
   The other side of the optics holder  12  is secured to the second holding part  15   b  through the rotational positioning of the second holder segment  12   c . For this, the rotary head  17  is positioned on the second holder segment  12   c , inside an indentation  19  on the support surface of the second holding part  15   b  that faces the insert  13  and extends in a vertical plane. This indentation  19  extends in horizontal direction across the complete width of the second holding part  15   b . The indentation  19  has a constant semi-circular cross section in the longitudinal direction. The radius of the indentation  19  is adapted to the radius of the rotary head  17 . 
   The longitudinal axis of the optics holder  12 , arranged on the holding parts  15   a ,  15   b , also extends in the horizontal direction, wherein the longitudinal axis of the optics holder  12  is positioned perpendicularly to the optical axis of the transmitter  4 . 
   The position of the optics holder  12  relative to the insert  13  can be changed as specified to adjust the relative position of the transmitter  4  and the transmitting optics  7 . 
   An operating element in the form of a rod-shaped lever  20  is provided to vary the position of the transmitting optics  7  in a vertical plane that extends perpendicularly to the optical axis of the transmitter  4 . The lever  20  is disposed in a bore  21  of a first holder segment  12   b  of the optics holder  12 , wherein the bore  21  extends in axial direction through the first holder segment  12   b . The cross section of bore  21  narrows down in the center of the first holder segment  12   b . Starting with this narrowed down cross-section, the diameter of the bore  21  continuously expands toward the locations where it exits on the front and back of the first holder segment  12   b . A recess  22  that exits at the support surface is furthermore provided in the first holding part  15   a  for accommodating the lever  20 . The recess  22  has an essentially hemispherical design, wherein its diameter at the support surface is somewhat larger than the diameter of the lever  20 . To adjust the position of the transmitting optics  7 , the lever  20  is inserted into the bore  21  of the first holder segment  12   b , so that the front end of lever  20  that projects over the first holder segment  12   b  engages in the recess  22  in the first holding part  15   a.    
   The position of the lever inside the receptacle is changed through moving the back end of the lever  20 . In the process, the first holder segment  12   b  is deflected in the plane for the support surface through the guidance of the lever  20  inside the bore  21 . As a result of the cone-shaped design of the bore  21 , the deflection movement of the lever  20  is continuously converted to a pivoting movement of the holder segment  12   b  and thus moves the complete optics holder  12 . With this pivoting movement, the optics holder  12  is pivoted relative to the pivoting axis predetermined by the rotary head  17 . In addition, the rotary head  17  is displaced in the second holding part  15   b , if necessary along the indentation  19 . As soon as the desired adjustment position of the optics holder  12  is reached, this holder is secured on the insert  13  with the fixing screw  18 . 
   An eccentric element  23  is provided for adjusting the position of the transmitting optics  7  in the direction of the optical axis for the transmitter  4 . The eccentric element  23  takes the form of an eccentric plate and is positioned on the side relative to the insert  13 , with the rotational axis extending in vertical direction. The outer surface of the eccentric plate rests against the back of the optics holder  12 , in the region of the support segment  12   a  end, which is facing the second holding element  12   c . A wrench or similar tool is attached to the surface and used to turn the eccentric plate around the plate&#39;s rotational axis, which changes the contact pressure exerted onto the optics holder  12  in accordance with the shape of the eccentric plate. 
   The optics holder  12  is bent in the region of flexible element  12   d  by changing the contact pressure. As a result, the support segment  12   a  is pivoted in horizontal direction and the transmitting optics  7  are either moved toward or away from the transmitter  4 . The respectively adjusted position of the optics holder  12  is secured by the eccentric plate  23  since the eccentric plate  23  presses the first holder segment  12   b  with the rotary head  17  into the indentation  19 . As a result of the springy effect of the leg of the holder segment  12   c , a contact spring is formed that pushes against the eccentric plate  23 . 
     FIGS. 5 and 6  show a different embodiment of an adjustment device for an optical sensor  1 . The transmitter  4  is again positioned inside an insert  13 , wherein the insert  13  has a bore  14  for accommodating the transmitter  4 . The optics holder  12  again holds the transmitting optics  7  and follows the insert  13  with the transmitter  4 . 
   The optics holder  12  is provided with a spherical head  24 , having a spherical outer surface. A bore  25  with the transmitting optics  7  disposed therein extends through the spherical head  24 . The optics holder  12  furthermore has a housing, consisting of two housing halves  26   a ,  26   b , which are secured to each other, fitted one on top of the other, with fixing screws  18 ′. Each housing half  26   a ,  26   b  has a spherical half shell  27   a ,  27   b . The spherical half shells  27   a ,  27   b  complement each other to form a spherical receptacle with the spherical head  24  disposed therein. The upper spherical half shell  27   a  contains a circular opening  28  on the top. A lever  20 ′ that is connected to a spherical head  24  and radially projects from the outer surface of the spherical head  24  extends through this opening  28 . Alternatively, the lever  20 ′ can also be inserted into a bore in the spherical head  24 . The opening  28  has a smaller diameter than the lever  20 ′, which functions as operating element. 
   To adjust the position of transmitting optics  7 , the fixing screws  18 ′ on the housing are loosened slightly. As a result, the spherical head  24  fits with only slight friction against the walls of the spherical half shells  27   a ,  27   b  and can be pivoted to the desired adjustment position by deflecting the lever  20 ′. Following this, the adjusted position of spherical head  24  is secured by tightening the fixing screws  18 ′. In principle, the holder inside the spherical half shells  27   a ,  27   b  can also be designed to be self-holding, so that the fixing screws  18 ′ can be omitted. For this, at least one spherical half shell  27   a ,  27   b  is made from a material having springy characteristics, so that the spherical head  24  can be locked in place as a result of the spring force exerted by the spherical half shell  27   a ,  27   b.    
   The transmitting optics  7  inside the spherical head  24  can be pivoted inside the housing in a vertical plane that extends perpendicularly to the optical axis for the transmitter  4 . The distance between the transmitter  4  and transmitting optics  7  is adjusted by displacing the transmitter  4  in its position along the optical transmitter axis. 
   While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should instead be defined only in accordance with the following claims and their equivalents.