Abstract:
Optical sensor methods and systems for detecting the edge of an object are disclosed. An optical sensor having dual equal area active regions can be provided, and a uniform light source located opposite the optical sensor, such that an occlusion of light from the uniform light source provides location determination data of an object via the optical sensor regardless of the direction of motion of the occlusion relative to the dual equal area active regions thereof.

Description:
TECHNICAL FIELD 
   The present invention generally relates to semiconductor sensors, including optical sensors. The present invention also relates to sensors for detecting the edge of an object for position location thereof. The present invention is also related to silicon photo detector devices and manufacturing technologies thereof. 
   BACKGROUND OF THE INVENTION 
   Optical sensors are well known in the electronic sensing arts. Optical sensors are commonly used in the field of printers and hand-held and desktop computers. Functions of sensors within this field usually include label detection, gap detection, skew, label length or width determination, etc. Advantages of these devices include their small size and durability. As with any device, however, there are also disadvantages, including the fact that a certain level of sensitivity, precision or tolerance associated with each sensor, can vary greatly. Additionally, ambient lighting can greatly confuse the interpretation of the light received by the sensor, and the characteristics of the print media or other sensing media or sensing target can vary greatly. A higher sensitivity or tighter tolerance can result in a higher sensor cost, which presents another disadvantage. 
   In order to maintain reasonable costs associated with devices, such as, for example, printers, while attaining considerable accuracy, conventional sensing devices have employed a variety of sensing methods, which utilize lower-cost sensors to achieve acceptable results. Such sensors, however, generally become dirty, decay over time, rely upon inconsistent and varying manufacturing techniques, and in many other manners the characteristics of each sensor are different or can change over time. Thus, conventional sensor designs, which did not precisely account for these variations or changing ambient conditions, could not provide consistently reliable results. Other prior art designs offer manual adjustability or self-calibration but with heightened design and manufacturing complexity and greatly increased costs. 
   Optical sensors are ideally suited for edge detection. As explained, above, however, conventional optical sensors have a number of limitations, including the inability to provide highly accurate and repeatable sensing data regardless of the direction of motion of a sensor or optical light occlusion thereof. 
   The present inventors have thus concluded, based on the foregoing, that a need exists for an improved optical sensor, including methods and systems thereof, for use in detecting the edge of target objects. The present inventors believed that the improved optical sensing methods and systems disclosed herein can provide an accurate and repeatable edge detection of an object without suffering from the inconsistencies and inefficiencies that currently plague conventional optical sensing devices. 
   BRIEF SUMMARY OF THE INVENTION 
   The following summary of the invention is provided to facilitate an understanding of some of the innovative features unique to the present invention and is not intended to be a full description. A full appreciation of the various aspects of the invention can be gained by taking the entire specification, claims, drawings, and abstract as a whole. 
   It is, therefore, one aspect of the present invention to provide for improved optical sensor methods and systems. 
   It is also an aspect of the present invention to provide a semiconductor optical sensor having dual area active regions thereof. 
   It is another aspect of the present invention to provide an improved optical sensor for the detection of an edge of an object to determine its precise position and to allow servoing to a pre-determined location. 
   The above and other aspects can be achieved as is now described. Optical sensor methods and systems for detecting an edge of an object are disclosed herein. An optical sensor having dual equal area active regions is provided. A uniform light source is located opposite the optical sensor, wherein an occlusion of light from the uniform light source provides location determination data of an object via the optical sensor regardless of a direction of motion of the occlusion relative to the dual equal area active regions thereof. 
   The optical sensor can be configured in the shape of a rectangle and the dual equal area active regions thereof can be configured to include at least one upper region configured in a shape of an inverted triangle, and at least one lower region formed from a remainder of the rectangle, thereby resembling a shape of mirrored triangles having a common vertex and at least one hypotenuse thereof separated from the upper region by a thin inactive region. 
   The present invention can provide accurate and repeatable detection of the edge of an object to determine its precise position, and also allows servoing to a pre-determined location. The optical sensor described herein can be implemented as a silicon, or other semiconductor, optical sensor composed of dual equal area active regions whose geometry is configured, such that the occlusion of light from a light source, normal to the plane of the optical sensor, produces a differential output whose characteristics provide highly accurate and repeatable means of location determination regardless of the direction of motion of the occlusion. 
   Due to the unique geometric layouts of the active areas, as the occlusion moves across the sensor an unbalanced output is created that only becomes balanced at the exact center of the optical sensor. The direction and magnitude of displacement can also be resolved from the sensor outputs. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying figures, in which like reference numerals refer to identical or functionally-similar elements throughout the separate views and which are incorporated in and form part of the specification, further illustrate the present invention and, together with the detailed description of the invention, serve to explain the principles of the present invention. 
       FIG. 1  depicts a block diagram of a sensor system at Time  1 , in accordance with a preferred embodiment of the present invention; 
       FIG. 2  illustrates a block diagram of a sensor system at Time  2 , in accordance with a preferred embodiment of the present invention; 
       FIG. 3  depicts a block diagram of a sensor system at Time  3 , in accordance with a preferred embodiment of the present invention; 
       FIG. 4  illustrates a block diagram of a sensor system at Time  4 , in accordance with a preferred embodiment of the present invention; 
       FIG. 5  depicts a graph depicting solar cell sensor tape edge characterization coarse data, which can be generated in accordance with a preferred embodiment of the present invention; 
       FIG. 6  illustrates a graph depicting sensor area output data versus tape edge displacement data, which can be generated in accordance with a preferred embodiment of the present invention; 
       FIG. 7  depicts a graph illustrating sensor output data generated with respect to a sensor implemented in accordance with a preferred embodiment of the present invention; and 
       FIG. 8  illustrates a high-level flow chart depicting logical operational steps that can be followed to implement an optical sensor in accordance with a preferred embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The particular values and configurations discussed in these non-limiting examples can be varied and are cited merely to illustrate embodiments of the present invention and are not intended to limit the scope of the invention. 
     FIG. 1  depicts a block diagram of a sensor system  100  at Time  1 , in accordance with a preferred embodiment of the present invention. Sensor system  100  includes an optical sensor  104  that can be fabricated utilizing conventional silicon photo-detector manufacturing processes and methodologies to produce a unique geometric layout of active regions. When nested, the two active regions can form a rectangle. 
   In accordance with a preferred embodiment of the present invention, an upper region  110  can be shaped as an inverted equilateral triangle and lower regions  106  and  108  can be formed by the remainder of the rectangle, thereby resembling mirrored right triangles with a common vertex and hypotenuses thereof, which can be separated from the upper region  110  by a very thin inactive region. This thin inactive region, although existing physically, can possess a negligible width thereof that is effectively zero when sensor diodes associated with sensor  104  are reverse biased. Note that the term “opto-electronic sensor” and “optical sensor” can be utilized interchangeably herein to describe the same general device. 
   In practical usage, sensor  104  can be mounted opposite a uniform light source  120 , and thereafter powered up so that the outputs of sensor  104  are monitored for change in current. Thus, as indicated in the example of  FIG. 1 , sensor  104  can be located proximate to an opaque object  102 . At Time  1 , as shown in  FIG. 1 , sensor  104  is generally unobscured, such that the output of both channels are virtually equivalent to one another and dependent upon the intensity of the light source. 
     FIG. 2  illustrates a block diagram of the sensor system  100  at Time  2 , in accordance with a preferred embodiment of the present invention. Similarly,  FIG. 3  depicts a block diagram of the sensor system  100  at Time  3 , in accordance with a preferred embodiment of the present invention. Likewise,  FIG. 4  illustrates a block diagram of the sensor system  100  at Time  4 , in accordance with a preferred embodiment of the present invention. Thus, in  FIGS. 1  to  4 , like or analogous parts are indicated by identical reference numerals. 
   As depicted in  FIG. 2 , as the opaque object  102  begins to occlude sensor  104 , the current in the upper region  110  will always be higher than the current in lower regions  106  and  108  until the opaque object  102  is directly centered over the sensor  104 , as indicated in  FIG. 3 , at which time the currents will be exactly the same. As the opaque object  102  continues across the sensor  104 , the current in the lower regions  106  and  108  will always be higher than the current in the upper region  110  until the sensor  104  eventually becomes entirely occluded at which time both outputs are approximately zero. 
   Note that in  FIG. 4 , the sensor  104  is depicted as approaching complete occlusion. It can be appreciated by those skilled in the art, based on  FIGS. 1  to  4 , that a complete occlusion is eventually achieved. Depending on the current differential between the two outputs, the distance from the center of the sensor  104  can be calculated and the direction can be determined by comparing the previous outputs to the latest outputs. 
   Sensor  104  can therefore be implemented as a semiconductor optical sensor that includes dual equal area active regions whose geometry is configured, such that occlusion of light from a light source, normal to the plane of the sensor  104 , produces a differential output whose characteristics provide highly accurate and repeatable means of location determination regardless of the direction of motion of the occlusion. Due to the unique geometric layouts of the active areas, as the occlusion moves across the sensor  104 , an unbalanced output can be created that only becomes balanced at the exact center of the sensor  104 . The direction and magnitude of displacement can also be resolved from the sensor outputs. 
   It can be appreciated by those skilled in the art that the configuration depicted in  FIGS. 1  to  4  herein represents one possible embodiment of the present invention and that other variations may be implemented, such as a different geometric layout of the active areas. At can also be appreciated by those skilled in the art that the output whose characteristics are utilized for location determination is not limited to current data, but can also be voltage and/or resistance or a combination thereof. 
     FIG. 5  depicts a graph  500  depicting solar cell sensor tape edge characterization coarse data, which can be generated in accordance with a preferred embodiment of the present invention. Graph  500  includes a legend box  502  referencing channel  1  and channel  2  photocurrent plot lines, which are respectively shown in graph  500  as plot lines  504  and  506 . Plot lines  506 , with respect to a channel  2  photocurrent extends from an interrupter edge position of −0.284 inches to 0.316 inches. Plot line  504 , on the other hand extends from an interrupter edge position located approximately between −0.284 inches and −0.225 inches to 0.316 inches, as shown in graph  500  of FIG.  5 . 
   Plot line  504  flattens out at a photocurrent of approximately 10 mA, while plot line  506  flattens out between a photocurrent of 8 mA and 10 mA at approximately 9 mA. It can be appreciated by those skilled in the art that the data depicted in  FIG. 5  is not considered a limiting feature of the present invention, but is presented for generally illustrative and edification purposes only. 
     FIG. 6  illustrates a graph  600  depicting sensor area output data versus tape edge displacement data, which can be generated in accordance with a preferred embodiment of the present invention. Graph  600  includes a legend box  602  referencing detector “A” active area and “B” active area output data. Line  604  is thus associated with output from the A active area, while line  606  is associated with the output from the B active area. The B active area is analogous to the upper region  110  of sensor  104 , while the A active area is analogous to the lower regions  106  and  108  of sensor  104 . 
     FIG. 7  depicts a graph  700  illustrating sensor output data generated with respect to a sensor implemented in accordance with a preferred embodiment of the present invention. Graph  700  generally depicts sample calculated output data obtained from a sensor  704  whose area is arbitrarily set at 800 units. Sensor  704  of  FIG. 7  is generally analogous to the sensor  104  depicted in  FIGS. 1  to  4  herein. Sensor  704  thus includes lower region(s) A and upper region B. 
   A legend box  702  indicates respective output values associated with sensor  704 , including lower region A and upper region B. Delta (i.e., differential) values, along with the ratios of A to B and B to A are also shown in legend box  702  and referenced by plot lines of graph  700 . Thus, line  706  is associated with output data from lower region A, while line  708  is associated with output data from upper region B. Line  710  references delta values, while line  712  is associated with a ratio A to B data and line  714  with a ratio of B to A data. It can be appreciated by those skilled in the art that the data depicted in  FIG. 7  is not considered a limiting feature of the present invention, but is presented generally for illustrative and edification purposes only. 
   The optical sensor described herein can be adapted, for example, for use to servo-control the tape edge in a tape storage application. Essentially, a “zero” position of the tape would occur when a first channel and two outputs thereof are equal. If the tape moves and unbalances the sensor output, then the direction of movement can be determined by the relative magnitudes of the first and second channels. For example, if the tape moved from a zero position to a left position, then a channel two-output signal would be lower in magnitude than a channel one output signal. Thus, the tape could then be adjusted to the right. 
     FIG. 8  illustrates a high-level flow chart  800  depicting logical operational steps that can be followed to implement an optical sensor in accordance with a preferred embodiment of the present invention. As indicated at block  802 , the optical sensor described herein can be formed upon, but not limited to, a silicon substrate, thereby providing a silicon-based optical sensor device. As indicated next at block  804 , the optical sensor can be configured to include dual equal area active regions, which include, as depicted at block  806 , one or more upper regions and one or more lower regions. An example of an upper region includes upper region  110  and lower regions  106  and  108  of sensor  104  of  FIGS. 1  to  4 . Once the optical sensor is formed, it can be located opposite a light source, as indicated at block  808 . 
   Thereafter, as illustrated at block  810 , occlusion of light from the light source moves across the optical sensor, and next, as indicated at block  812 , an unbalanced output can be created. This unbalanced output generated from the optical sensor becomes balanced at the exact center of the optical center, as illustrated at block  814 . The geometry of the optical sensor, including the dual equal area active regions is such that occlusion of light from a light source, normal to the plane of the sensor, produces a differential output whose characteristics provide highly accurate and repeatable means of location determination regardless of the direction of motion of the occlusion, as indicated at block  816 . The direction and magnitude of the displacement can then be resolved from the sensor outputs, as illustrated at block  818 . 
   The embodiments and examples set forth herein are presented to best explain the present invention and its practical application and to thereby enable those skilled in the art to make and utilize the invention. Those skilled in the art, however, will recognize that the foregoing description and examples have been presented for the purpose of illustration and example only. Other variations and modifications of the present invention will be apparent to those of skill in the art, and it is the intent of the appended claims that such variations and modifications be covered. The description as set forth is not intended to be exhaustive or to limit the scope of the invention. Many modifications and variations are possible in light of the above teaching without departing from the scope of the following claims. It is contemplated that the use of the present invention can involve components having different characteristics. It is intended that the scope of the present invention be defined by the claims appended hereto, giving full cognizance to equivalents in all respects.