Active solid-state devices (e.g. – transistors – solid-state diode – Responsive to non-electrical signal – Electromagnetic or particle radiation
Reexamination Certificate
1998-07-21
2001-03-27
Jackson, Jr., Jerome (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Responsive to non-electrical signal
Electromagnetic or particle radiation
C257S040000, C257S432000, C257S294000, C250S208100, C250S221000, C250S550000
Reexamination Certificate
active
06208006
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to solid state electronic devices. More particularly, it concerns thin film spatial filters made from organic or inorganic semiconductors or conductors which function as an active resistive network and find utility as spatial frequency filters to provide background suppression and local contrast gain control.
BACKGROUND OF THE INVENTION
Spatial frequency filtering is essential to a variety of image processing applications. Spatial frequency filtering is currently being used for image enhancement in medical imagery, such as in Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI), as an aid to detection of cancerous regions. In military applications, spatial frequency filtering is useful in the arena of target detection. In this case, bandpass filtering can be used to isolate features of a given dimension from an image, thus facilitating greatly the target detection algorithms.
Two of the existing methods for achieving spatial frequency filtering of images are computer software and analog discrete circuit implementations; both have significant drawbacks.
For the digital software approach, even a simple algorithm which produces “blurring” (low pass spatial frequency filtering) of an image can take up to several minutes to calculate, and is strongly dependent on the resolution of the image. For example, for a standard 1024×1024 grayscale image, a Gaussian blur of 20 pixels would take approximately 30 seconds using a standard Pentium computer; for higher resolution images with full color capability, this operation would take much longer. The power consumption for these systems is relatively high, with a standard desktop computer consuming in excess of 75 Watts.
Spatial frequency filtering has also been implemented [C. M. Mead,
Analog VLSI and Neural Systems,
1989] in the analog domain using digital circuits comprising discrete circuits comprising field effect transistors (FETs). This method was shown to be effective for achieving local contrast control (high pass spatial frequency filtering). However, the discrete circuit approach has two fundamental drawbacks.
First, the lateral conductance between pixels is emulated by a complicated multiple FET circuit, which requires a large unit cell area (“real estate”) for each pixel; typically dimensions of nearly 100 &mgr;m×100 &mgr;m are required. Because there is such a large real estate demand for this implementation, large format arrays (e.g. 1024×1024) cannot be fabricated, since the resultant array would have dimensions of 10 cm×10 cm. Current semiconductor processing techniques are not compatible with devices larger than 2 cm.
Second, like the computational algorithmic approaches to spatial frequency filtering, the discrete FET implementation also has a slow time response (
~
100 msec), in addition to large power requirements (>20W for a 1024×1024), both of which are incompatible with real time remote sensing applications which require sub-millisecond response with sub-Watt power consumption.
STATEMENT OF THE INVENTION
The present invention provides thin film spatial filters (TF Spatial Filters). This type of device, made from layers of thin film conductors (either conducting polymers, organic conductors, or inorganic conductors or semiconductors), functions as an active resistive network. The nondelineated conducting layer(s) provide spatial frequency filtering including background suppression and local contrast gain control. A single device with simple user adjustment can function as either a high pass or low pass spatial frequency filter with frame to frame agility. Any admixture of the filtering action by a linear combination with the original image is likewise easily controlled and implemented. The simplifications in the device architecture enable a super-architecture of image processors that can perform a variety of complex functions. By combining several devices operated individually as high and low pass spatial filters with different blurring lengths (spatial frequency roll-off), an agile band pass spatial filter of any selected width can be constructed.
A non-delineated array constructed from either conducting polymers or inorganic semiconductors offers both fabrication advantages and a significant saving of “real estate” within the unit cell of each pixel compared to the discrete approach implemented in conventional VLSI silicon technology [as described, for example, by C. M. Mead,
Analog VLSI and Neural Systems,
1989]. This is especially true in situations where temporal signatures are to be analyzed over the entire focal plane, thereby eliminating a digital approach to lateral interaction.
It is accordingly an object of the present invention to provide Thin Film Spatial Filters which are useful as spatial frequency filters.
It is additionally an object of the present invention to provide Thin Film Spatial Filters which are useful as low pass spatial frequency filters.
It is additionally an object of the present invention to provide Thin Film Spatial Filters which are useful as high pass spatial frequency filters. It is additionally an object of the present invention to provide Thin Film Spatial Filters which are useful as band pass spatial frequency filters.
It is additionally an object of the present invention to provide a means by which the spatial decay length (or blurring length) can be controlled.
It is additionally an object of the present invention to utilize the processing advantages associated with the fabrication of the conducting layer(s) of the TF Spatial Filter from soluble organic materials such as, for example, conducting conjugated polymers (and/or their precursor polymers), cast from solution to enable the fabrication of large active areas. Examples of conducting polymers that are processable from solution include, but are not limited to polyaniline (emeraldine salt form) and doped poly(ethylenedioxythiophene).
It is additionally an object of the present invention to utilize inorganic materials for the conducting layer(s) of the TF Spatial Filter. Examples include, but are not limited to indium/tin-oxide, amorphous silicon and amorphous carbon.
DETAILED DESCRIPTION OF THE INVENTION
The detailed description includes the following sections:
Brief description of the Drawings
Description of the Preferred Embodiments
Examples
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Heeger Alan J.
Langan John L.
McElvain Jon S.
Jackson, Jr. Jerome
Uniax Corporation
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