Abstract:
A sensor includes an array of substantially parallel wires, radiant energy sensitive material formed adjacent the array of parallel wires, and output units connected to each of the wires and constructed to provide an analog correlation vector output responsive to radiant energy incident on the sensor. The sensor is constructed as an image sensing device suitable for applications such as pattern recognition and image tracking.

Description:
This application is a Continuation-In-Part of the U.S. patent application Ser. No. 11/446,223 entitled “Crosswire Sensor,” filed Jun. 5, 2006 now U.S. Pat. No. 7,488,950. 

   FIELD OF THE INVENTION 
   The present invention pertains to a sensing device which may be used for a variety of sensing functions including pattern recognition, pattern comparison and image tracking. 
   BACKGROUND OF THE INVENTION 
   Array sensor technologies such as CCD or CMOS sensors have typically included the use of semiconductor or capacitive junctions formed from silicon substrates. However, new materials based on nanoparticulate matter or photosensitive molecular and polymer films provide an avenue for new sensor technologies which may provide several advantages over the conventional sensor technologies. U.S. patent application Ser. No. 11/446,223, which is incorporated by reference in its entirety, provides teachings of using such materials to construct sensor arrays for applications such as imaging and pattern recognition. The present patent application provides further embodiments of such a sensor. 
   SUMMARY OF INVENTION 
   A sensor includes an array of substantially parallel wires, radiant energy sensitive material formed adjacent the array of parallel wires, and output units connected to each of the wires and constructed to provide an analog correlation vector output responsive to radiant energy incident on the sensor. The sensor is constructed as an image sensing device suitable for applications such as pattern recognition and image tracking. 
   In one particular embodiment the sensor includes a first array of substantially parallel wires formed on a first substrate, a second array of substantially parallel wires formed on the first substrate at an intersecting angle with the first array of parallel wires, an input electrode formed on a second substrate, radiant energy sensitive material formed between the first and second substrates, and output units connected to each of the wires in the first and second arrays and constructed to provide analog correlation vector outputs responsive to radiant energy incident on the sensor. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1   a - 1   d  illustrate fabrication steps for a first substrate used in forming one embodiment of the sensor. 
       FIGS. 2   a - 2   b  illustrate assembly of the first substrate with a second substrate to form the sensor. 
       FIG. 3  illustrates a top view cross-section of wiring of the sensor connected to output circuits. 
       FIG. 4  illustrates an embodiment of the output circuits employing an op-amp functioning as a summing amplifier. 
       FIG. 5   a - 5   d  illustrate uses of the sensor in image and pattern sensing. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1   a - 1   d  illustrate fabrication steps for a first substrate used in forming one embodiment of the sensor.  FIG. 1   a  illustrates a substrate  100  provided with a layer of metallic material patterned as a series of parallel wires  110 . Substrate  100  may be made from a variety of insulating materials such as glass or plastic with either rigid or flexible characteristics depending on the desired application and fabrication method. An insulating layer  120  is coated over the substrate  100  and metallic wiring array  110 .  FIG. 1   b  illustrates a second array of parallel metallic wires  130  formed at a perpendicular, or at least intersecting, angle with the first array of parallel wires  110 . The different layers  110 ,  120 ,  130  are preferably formed and patterned using a low cost process applicable at room temperature and pressure such as inkjet printing, silkscreen printing, roll to roll processing, imprinting or self-assembly. Alternatively, deposition, optical lithography, and other techniques more conventionally used by the semiconductor industry may be employed to form the layers  110 ,  120 ,  130 .  FIG. 1   c  illustrates post-etching of the insulating layer  120  using wiring  130  as a mask.  FIG. 1   d  illustrates deposition of radiation sensitive material  140  above wiring  110  and  130 . The radiation sensitive material may be material such as discussed in Sakuhara et al. U.S. Pat. No. 4,837,435 or Jang et al. U.S. Pat. No. 7,042,003 (both of which are incorporated by reference in their entirety) or take the form of any other known material sufficiently sensitive to photonic, electronic or ionic. radiation so as to be useful in sensor applications. 
     FIGS. 2   a - 2   b  illustrate assembly of the first substrate from  FIG. 1   d  with a second substrate to form the sensor. The second substrate  210  may be formed from a reflective or opaque material and is coated with a conductive film  220  to serve as an input electrode. In one embodiment, substrate  100  is formed of a material transparent to incident radiation such as visible light while the surface of substrate  210  in contact with material  140  is reflective to visible light. In another embodiment, substrate  100  may be formed to be translucent with filtering properties so as to be selective to a particular type of radiation or frequency of light. As shown in  FIG. 2   a  substrate  210  is molded or etched to be complementary to the surface geometry of the first substrate from  FIG. 1   d . so as to form a uniform gap thickness for the layer  140 . However, if layers  120  and  130  are formed sufficiently thin with respect to the thickness of the layer  140  substrate  210  may instead be formed of uniform thickness. 
     FIG. 3  illustrates an exemplary cross-section top view of wiring of a sensor constructed in accordance with the above described method connected to output circuits A 1 -A 4  and B 1 -B 4 . Each output circuit is constructed to act as a summing amplifier for the corresponding row wiring  110  or column wiring  130  to produce an analog sum proportional to the electrical state of the corresponding row or column. 
     FIG. 4  illustrates an embodiment of the output circuits employing an op-amp functioning as a summing amplifier. Signal selouto) may be used to actuate the op-amp  450 , including feedback impedance Zout  430  and balancing impedance Zb  440 . The values of Zout and Zb for each output unit should be determined based on preliminary testing of the sensor to provide an identical low voltage output for each output unit under zero or minimal incident radiation conditions when voltage is applied input electrode  220 . Under incident radiation the summing amplifier would produce an output voltage corresponding to the incident radiation of the corresponding row or column. 
     FIGS. 5   a - 5   d  illustrate exemplary uses of the sensor in image and pattern sensing.  FIGS. 5   a  and  5   b  illustrate one example of the development of vertical and horizontal correlation vectors from a sensor array formed as an 8×8 matrix. In  FIG. 5   a , a voltage is applied to input electrode  220  and the output units associated with the rows are actuated. If the pattern of the incident radiation intensity affects only one column of the sensor as shown, a corresponding vertical correlation vector will be output consisting of a uniform intensity output. In  FIG. 5   b , a voltage is applied to input electrode  220  and the output units associated with the columns are actuated. If the pattern of the incident radiation intensity is the same as in  FIG. 5   a , an analog output will appear corresponding to the 3rd column. The array of column output units and array of row output units may be alternatively selected at sequential times to form an analog valued horizontal correlation vector (such as [00800000] in the example) and an analog valued vertical correlation vector (such as [11111111] in the example) associated with the image. The correlation vectors may be stored in a memory for later use or directly compared with a database of horizontal/vertical correlation vectors previously stored in memory corresponding to a database of correlation vectors associated with common shapes or figures. This allows for image identification to be performed more quickly then if individual digital pixels were to be compared. In the current example 16 analog values are formed (8 for the horizontal correlation vector and 8 for the vertical correlation vector) for comparison whereas 64 comparisons would be necessary if the results of each sensor element were analyzed independently. While comparison of analog values does not offer the precision of comparing binary or digital data, pattern recognition applications would typically require searches for the closest rather than an exact image match making comparisons of analog correlation vectors more reasonable. 
     FIGS. 5   c  and  5   d  illustrate another example of image recognition in which both the position and shape of a pattern are identified. For example, a black square pattern, with a white square pattern of half the size embedded therein, may be identified with stored horizontal and vertical correlation patterns such as [(2 1 1 2), (2 1 1 2)]. Though the particular magnitude and position of a detected pattern using horizontal and vertical correlation vectors may differ from the stored value, this difference may actually be useful to ascertain the coordinates of the image and the relative intensity of the image. For example, the average analog value R of a correlation vector may be found using the algorithm R=Σf(n)/N, the summation performed over 1≦n≦N wherein n represents an ordinal number of the analog values in the correlation vector, f(n) represents the analog values corresponding to the ordinal numbers n, and N represents the maximum ordinal number (i.e. size) of the correlation vector. The mean coordinate X of a correlation vector may be found using the algorithm X=Σ[nf(n)]/Σf(n), the summations performed over 1≦n≦N. For a correlation vector (0 4 2 2 4 0 0 0), N=8, Σf(n)=12, Σnf(n)=42, R=1.5, X=3.5. For a correlation vector (0 0 2 1 1 2 0 0), N=8, Σf(n)=6, Σnf(n)=27, R=0.75, X=4.5. It can readily be seen that the relative mean coordinates X and average values R of detected and stored correlation vectors may be used in feedback control for image tracking and magnification control (for the given example the difference in mean coordinates 4.5−3.5=1 is indicative of the necessary repositioning while the ratio of the average values 0.75/1.5=0.5 is indicative of the magnification adjustment). 
   It is important to note that a horizontal and vertical correlation vector does not uniquely describe a particular pattern and can not be used to reconstruct a pattern. However, the use of a turret on which the sensor of the present invention is mounted may be rotated to find the correlation vector at different angles and expand the characterization of the image. In addition, such a turret could allow for only one array of parallel wires to be used in the manufacture of the sensor making manufacture simpler. 
   The use of the sensor of the present invention in pattern recognition may be combined with various feedback control systems such as used in robotics, automated vehicular control, etc. Feedback may also be provided to control preliminary optics to determine magnification and directional orientation (translation/rotation) of the image exposed to the sensor. For example, in the case of  FIGS. 5   c  and  5   d , the detected correlation vectors may be used to adjust the optics to center and enlarge the image to provide for higher resolution image analysis or to provide for image tracking such as tracking the position of a celestial body, a missile or projectile or for characterization of image patterns such as human facial characteristics, etc. 
   MODIFICATIONS/ALTERNATIVES 
   As discussed in the parent U.S. patent application Ser. No. 11/446,223, which is incorporated by reference in its entirety and to which the teachings of the present application may be applied, many modifications and alternatives are possible. The present invention is only limited by the following claims.