Abstract:
The optical control having an optical source that uses a transmission medium to deliver energy to an optical detector. Upon physical contact with the transmission medium changes in the internal reflection of the transmission medium occur and reduce the amount of energy being delivered to the detector. The change in internal reflection causes a change in the state of the optical control.

Description:
BACKGROUND 
     1. Field of the Invention 
     The present invention generally relates to an optical control for a human machine interface. 
     2. Description of Related Art 
     For automotive applications, as well as other environments, mechanical controls are typically used to provide input to an electrical system. Over time, the mechanical controls may wear or collect debris impeding the performance of the controls. Typically, these controls are moved, for example rotated or displaced, to provide user input to the system. Common controls could include knobs, levers, and switches. Recently, other sensing technologies have been investigated to replace controls that require mechanical movement. Some of the technologies investigated include resistive, capacitive, direct optical, and infrared, as well as microwave and magnetic inductance. Each of these approaches reveal a variety of feasibility issues. Although some of these technologies are currently available, their cost and form factor complicates designing them into the automotive interior environment efficiently. In addition, vehicle occupants should be able to identify the control at night in the dark. Accordingly, the control should be lit to help identify its location. 
     Automotive interiors pose many constraints that limit the use of the above mentioned technologies. Aesthetics, space, and cost concerns usually filter out the above mentioned choices. For example, touch panels typically use resistive technology, however, these devices are typically too large for automotive consoles and not compatible with the aesthetics of the automotive environment. Capacitive technologies are not compatible with vehicle occupants wearing gloves. Direct optical technologies are generally sensitive to varying day and night driving conditions. Infrared controls may be sensitive to vehicle occupants wearing gloves and have unacceptable response times. Other inductive techniques may lead to difficult packaging feasibility, as well as, electromagnetic noise issues. 
     In view of the above, it is apparent that there exists a need for an improved optical control for a human machine interface. 
     SUMMARY 
     In satisfying the above need, as well as overcoming the enumerated drawbacks and other limitations of the related art, the present invention provides an improved optical control for a human machine interface. 
     The optical control includes an optical source that uses a transmission medium to deliver energy to an optical detector. Changes in the internal reflection of the transmission medium will reduce the amount of energy being delivered to the detector. This change in internal reflection thus causes a change in the state of the optical control. The internal reflection through the transmission medium may be changed in many ways. However, a balance of input and output energy must be maintained such that the transmission, plus the reflection, plus the absorption must equal one. Therefore, if an item is introduced into contact with the transmission medium, increased absorption and scattering reflection outside the medium occurs. Accordingly, the transmission rate within the medium is reduced. Alternatively, if the geometry of the transmission medium is changed, the optical properties would be affected to achieve a similar result. Prior optical techniques, typically, used a direct source and a detector without utilizing changes in the total internal reflection of a medium between these devices. In addition, monitoring the internal reflection is less sensitive to ambient light since the ambient light can be decoupled from the source inputs based on transmission medium geometry. 
     Further objects, features and advantages of this invention will become readily apparent to persons skilled in the art after a review of the following description, with reference to the drawings and claims that are appended to and form a part of this specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is schematic view of an optical control in accordance with the present invention; 
         FIG. 2  is a side view of an optical control illustrating a light path in an unactivated state in accordance with the present invention; 
         FIG. 3  is a side view of an optical control illustrating the light path when the control is activated in accordance with the present invention; 
         FIG. 4  is a front view of a optical control switch in accordance with the present invention; 
         FIG. 5  is a sectional view, generally taken along line  5 — 5  in  FIG. 4 , of an optical control switch in accordance with the present invention; 
         FIG. 6  is a slide-type control based on an optical control switch in accordance with the present invention; and 
         FIG. 7  is a dial-type control based on an optical control switch in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIG. 1 , an optical control embodying the principles of the present invention is illustrated therein and designated at  10 . As its primary components, the optical control  10  includes a light source  12 , a transmission medium  14 , and a detector  16 . A control circuit  18  is in electrical communication with the optical source  12  to generate a beam of light. The beam of light is transmitted from the optical source  12  into the transmission medium  14 , which is a medium such as a waveguide or translucent sheet allowing the beam of light to propagate therethrough. The beam of light enters at a first end  13  of the transmission medium  14  and exits at a second end  15 , where an optical detector  16  is aligned with the second end  15  to receive the beam of light. The optical detector  16  generates an electrical signal based on the beam of light and the internal reflection characteristics of the transmission medium  14 . This electrical signal is then provided to the control circuit  18 . Changes in the internal reflection of the transmission medium  14  cause changes the amount of light that propagates through the transmission medium  14  and reaches the optical detector  16 . Accordingly, the electrical signal generated based on the light beam received by the optical detector  16  may be analyzed to determine if the internal reflection has changed. 
     Now referring to  FIGS. 2 and 3 , an example is provided in more detail illustrating the changes in internal reflection when an object  22  comes in contact with the transmission medium  14 . The optical source  12  generates a beam of light, as previously described above. The beam of light is received by the first end  13  of the transmission medium  14 . With no object contacting the transmission medium  14 , the entire beam of light propagates through the transmission medium  14  with minimal losses. In  FIG. 2 , the path of the beam of light within the medium is illustrated by the ray traces  20 . As shown by the ray traces  20 , the beam of light reflects off the internal walls of the transmission medium  14  as it propagates between the first end  13  of the transmission medium  14  to the second end  15  of the transmission medium  14 , where it is received by the optical detector  16 . 
     In  FIG. 3 , the optical source  12  provides the beam of light to the transmission medium  14  in the same manner as described above in reference to  FIG. 1 . However, only some of the traces  28  propagate the entire length of the transmission medium  14  and are provided to the optical detector  16 . Some of the traces  24  are directed at an area of the transmission medium  14  where an object  22  is in contact with the wall of the transmission medium  14 . When an object  22  is in contact with the transmission medium  14 , the light that is directed at the contacted area will be absorbed or diffusely reflected. Light that is absorbed by the object  22  is indicated by ray traces  26 . Light that is diffusely reflected into the transmission medium  14  is denoted by ray traces  24 . Accordingly, when the angle of incidence with the side of the transmission medium  14  of the traces  24  is greater than the reflection angle of the transmission medium  14 , the light will escape from the transmission medium  14  and be lost to the environment. With a smaller amount of light reaching the detector  16 , the optical detector  16  will create an electrical signal indicative of that overall lower light power. 
     Now referring to  FIGS. 4 and 5 , an optical switch  40  incorporating the above optical control  10  is provided. The optical switch  40  includes an optical source  48 , a transmission medium  42 , and an optical detector  50 . As previously described, the optical source  48  generates a light beam that propagates through the transmission medium  42  and is received by the optical detector  50 . To provide improved aesthetics, the optical switch  40  includes a housing  44  that may be made of a metal or plastic to match the environment, such as a vehicle interior, where the switch  40  is located. The housing  44  includes an opening  41  allowing a surface  46  of the transmission medium  42  to be exposed to the touch of the user through the opening  41 . Accordingly, the transmission medium  42 , is preferably provided with a geometry allowing the optical source and optical detector to be located out of plane with the touch surface  46  of the transmission medium  42 . The optical source  48  is aligned with a first surface  52  of the transmission medium  42  and may, preferably, be configured to generate a beam of light that is transmitted substantially perpendicular to the surface  52 . 
     The beam of light initially propagates along the transmission medium  42  to a curved portion  56  that changes the direction of light propagation. For the optical switch  40  the curved portion  56  provides approximately a 90° bend, although other geometries may be used. The curved portion  56  is in communication with a middle portion  58  that may be substantially straight or may include a slight curvature. The overall direction of propagation of the light beam through the middle portion  58  is generally in a direction that is parallel to an outside surface of the housing  44 . This middle portion  58  includes the previously mentioned touch surface  46  that is exposed through the opening  41  and the housing  44 . The light propagates along the middle portion  58  to a second curved portion  60 . The second curved portion  60  provides a curve of about 90°, away from the front surface of the housing  44 , allowing the light to propagate substantially perpendicular to the direction of propagation in the middle portion  58 . The light propagates from the second curved portion  60  through a second surface  54  that is aligned with the optical detector  50 , such that the beam of light may be received by the optical detector  50  which will generate an electrical signal. The electrical signal is indicative of the power of the optical beam and any change in the internal reflection characteristics of the transmission medium  42 . 
     As shown and described above, the transmission medium  42  generally has a “C” shape where the first surface  52  that receives the light beam is substantially parallel to the second surface  54  that is aligned with the optical detector  50  to provide the light beam to the optical detector  50 . The geometry of the transmission medium  42  allows improved packaging options including compact location of the optical source  48 , the optical detector  50 , and any processing electronics. In addition, the geometry of the transmission medium  42  may provide for the reduced effect of ambient light on the optical detector  50  resulting in improved sensing of changes in the internal reflection characteristics of the transmission medium  42 . Obviously, however, other configurations can be employed depending on design criteria and packaging. 
     When using the optical switch  40 , the user may direct an object, such as a finger, to contact the touch surface  46  of the transmission medium  42 , thereby changing the internal reflection characteristics of the transmission medium  42 . The optical detector  50  senses the lower power of the light beam (resulting from the change in internal reflection) and changes the state of the optical switch  40 . 
     Now referring to  FIG. 6 , various optical controls may be configured using multiple optical switches  40  of the type described above. In one embodiment, an optical slide-type control  70  is configured from a plurality of optical switches  78 . Provided in a linear arrangement, a series of touch surfaces  79 , one touch surface  79  for each optical switch  40 , is exposed through a corresponding opening in the a housing  72 . As described in reference to optical switch  40 , each optical switch  78  is configured to sense a change in internal reflection when the user contacts the touch surface  79  of one of the optical switches  78 . Accordingly, the user may touch one of the switches  78 , indicating a level or setting of the slide-type control  70  based on the location of the optical switch the order from the top control  74  to the bottom control  76 . Alternatively, the slide-type control  70  may be oriented in a horizontal direction where the order or level may be determined from left to right across the slide-control control  70 . 
     In another embodiment, a dial-type control  80  is constructed from a plurality of optical switches  86  configured in a circular arrangement. Each of the optical switches  86  has a touch surface exposed through a housing  82  and is configured to sense a change in internal reflection when the user contacts the surface of one of the optical switches  86 . Accordingly, the user may touch one of the switches indicating a level or setting of the dial control  80  based on the radial location of the optical switch. In addition, a controller can determine the transition between switches as the user moves from adjacent switch to adjacent switch around the dial control  80 . The transition between multiple switches may be interpreted by the controller as an adjustment to the level of a user setting. For example, a clockwise transition can be used to provide an increase in the user settings and a counterclockwise transition can be used to provide a decrease the level of the user setting. 
     As a person skilled in the art will readily appreciate, the above description is meant as an illustration of implementation of the principles this invention. This description is not intended to limit the scope or application of this invention in that the invention is susceptible to modification, variation and change, without departing from the spirit of this invention, as defined in the following claims.