Patent Publication Number: US-9886610-B2

Title: Monolithic integrated focal array plane and apparatus employing the array

Description:
DOMESTIC PRIORITY 
     This application is a Continuation of Non-Provisional application Ser. No. 14/975,719, entitled “MONOLITHIC INTEGRATED FOCAL ARRAY PLANE AND APPARATUS EMPLOYING THE ARRAY”, filed Dec. 19, 2015 which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     The present invention relates to an optical information detecting device having a matrix array of integrated semiconductor elements that are operable in either a photoresponsive or photoemissive mode. The present invention is particularly adapted to improving the performance of optical interfaces, optical transmitters, and image detecting apparatus such as bar code scanners or readers, optical heads, and other optical scanners. 
     Information of various types may be encoded in graphical form as one or more barcodes, including linear barcodes, in which parallel bars of various widths and spacing may represent encoded information, and matrix (or “two-dimensional”) barcodes, in which encoded information may be represented by a two-dimensional pattern of shading (e.g., Quick Response (“QR”) codes). Barcodes may typically be configured to be machine-readable, in order to facilitate retrieval and decoding of the information they represent for various purposes. Mobile computing devices and related applications may sometimes provide the capability to capture and/or decode barcodes of various types. For example, a camera-equipped cellular phone may be utilized to capture an image of a barcode (e.g., a QR code) and an internal (and/or remote) application may be utilized to decode the information encoded therein. 
     Laser barcode scanners were invented several decades ago. The principle of these scanners is to use a laser beam to scan a barcode and then the laser barcode image will be reflected from the barcode to a point-type sensor (such as a photodiode or phototransistor). Then, the reflected laser barcode image is converted into electronic signals which will be decoded by a decoder into numbers and/or characters represented by the barcode. 
     The original laser light comes from a point-shape laser beam, and so in order to perform the scanning of a barcode, there are two ways: one is moving the laser light by a hand in a scanning light line as shown in  FIG. 1 ; the other is moving the laser light by a mirror as shown in  FIG. 2 . 
     Heretofore, it is known that the light source of the barcode scanner is laser diode, the point type expanding light beam passes through a collimating lens and is transferred into a point type parallel light beam and then reaches a target barcode by reflecting the light beam using a mirror. The mirror rotates with a definite angle or vibrates to have the light “point” move from left to right (or from right to left) on the target barcode to scan the barcode, the scanned image is reflected back to a “point type” receiver (photodiode sensor, for example) to detect and decoded by the following electric components. The disadvantage of this design: i.e., to vibrate or rotate a mirror to send out the point type light source; the mirror might not be easy to be adjusted during manufacturing process, the mirror can be tilted or even disordered by collision. 
     As shown in  FIG. 2 , the light source structure includes a polygonal mirror  11  having a number of sides, each side of which is an independent mirror, so that the light emitted by laser diode  13  passes through a collimator  14  to be converted into parallel point-shape laser beam to one side of the polygonal mirror  11 . Then, the parallel point-shape laser beam will be reflected to the barcode  2  and generate one laser point on barcode, and then the laser point image will be reflected back to the polygonal mirror  11 . Thereafter, the reflected laser point image will be reflected again by polygonal mirror  11  and focused to a point-type sensor  15  by a light condensing lens. When the polygonal mirror  11  rotates, all sides of the polygonal mirror  11  will move and change the position and then the parallel point-shape laser beam will be reflected by the mirror at different angles, thereby enabling the parallel point-shape light beam to project on different positions of the barcode, and therefore causing the movement of the laser point. Due to the rapid rotation of the polygonal mirror  11 , the reflected laser point will be moved rapidly, thereby producing the scanning effect. 
     Because of the rapid movement of the polygonal mirror  11  or moving the laser light by hand in a scanning light line as shown in  FIG. 1 , a linear scanning light will be formed to cover the whole barcode  2 , so as to achieve the scanning operation. 
     The scanners requiring manual movement (See  FIG. 1 ) occupy no more than one percent of the market. The scanners with the rotating mirror or the vibrating mirror (see  FIG. 2 ) occupy the remainder of the laser barcode scanner market. However, the manufacturing cost for the rotating polygonal mirror or the vibrating mirror is expensive, the mirrors can be easily broken and are difficult to manufacture. Furthermore, the light source ( 13  in  FIG. 2 ) and the sensor array ( 15  in  FIG. 2 ) are typically disposed on separate circuit boards. That is, current optoelectronic devices used to sense motion or bar codes, for example, but not limited thereto, have separate chips for the light source, detector and processing electronics. 
     Therefore, it is desired to provide a light source without moving parts and reduce the number of circuit boards for an optical transceiver/optical information detecting apparatus, including a laser barcode scanner, which can obviate and mitigate the above-mentioned drawbacks. 
     BRIEF SUMMARY 
     According to one embodiment of the present invention, an optical information detecting apparatus is formed as an integrated, solid state monolithic structure. The monolithic structure includes a plurality of light sensors disposed on a substrate and electrically isolated from one another, a plurality of light emitting elements disposed on the substrate and electrically isolated from one another, the light sensors being optically isolated from the light emitting elements, and a circuit connected to the light emitting elements to generate light towards a target and connected to the light sensors to detect reflected light from the target, wherein a signal is generated in response to the detected light. The signal is indicative of an optical characteristic of the target. 
     According to an alternate embodiment of the present invention an optical information detecting apparatus comprising an integrated, solid state monolithic structure further comprising a first plurality of substantially coplanar photonic diodes disposed in a matrix array on a substrate and are optically and electrically isolated from one another, a second plurality of light emitting elements that are substantially coplanar and disposed in a matrix array with the first plurality of photonic diodes, a circuit for enabling the diodes to detect light, whereby a signal is generated in response to the detected light, the circuit switchably operates at least one of the photonic diodes to detect light and switchably operates at least one of the light emitting elements to generate light, and a light directing member that directs light that emanates from the light emitting elements to a target and for returning light that contains optical information to the diodes, the light directing member for directing light being external to the solid state monolithic structure. The signal is indicative of an optical characteristic of the target. 
     According to yet another alternate embodiment of the present invention, a bar code reading apparatus having an integrated, solid state monolithic structure that comprises a plurality of light sensors disposed on a substrate and electrically isolated from one another, a plurality of light emitting elements disposed on the substrate and electrically isolated from one another, the light sensors being optically isolated from the light emitting elements, a circuit connected to the light emitting elements to generate light towards a target and connected to the light sensors to detect reflected light from the target, wherein a signal is generated in response to the detected light, and a light directing member which directs light that emanates from the light emitting elements to the target and returns the light that contains optical information to the light sensors, the light directing member directs light being external to monolithic structure. The signal is indicative of an optical characteristic of the target. 
     Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention. For a better understanding of the invention with the advantages and the features, refer to the description and to the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The forgoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  illustrates a conventional light source structure of a laser barcode scanner. 
         FIG. 2  illustrates another conventional light source structure of a laser barcode scanner. 
         FIG. 3  illustrates a perspective view of an LED and photodetector focal plane array on a single substrate emitting light to scan a barcode through a lens disposed therebetween in an exemplary embodiment. 
         FIG. 4  illustrates a perspective view of the LED and photodetector focal plane array on a single substrate of  FIG. 3  receiving reflected light from the barcode through the lens disposed therebetween in an exemplary embodiment. 
         FIG. 5  is a pictorial representation (through a cross sectional view) illustrating a single pixel of a plurality of pixels on the LED and photodetector focal plane array of  FIG. 3  illustrating a Ge-on-insulator (GOI) photodetector, monolithically integrated with a Si-containing circuit and light source. 
     
    
    
     DETAILED DESCRIPTION 
     Turning now to the drawings, and in particular to  FIGS. 3-5 , there is shown a monolithically integrated chip  10  that includes a GOI substrate material ( 12 ) of the present invention. The chip  10  comprises a Si-containing, e.g., Si or SiGe, circuits  30  (only one shown in  FIG. 3  so as not to obscure the other elements), light sources  32 , and GOI photodetectors  34 . By monolithically integrating the light sources  32  and photodetectors  34  with the Si-containing circuits  30 , the parasitic inductance and capacitance can be reduced as compared with hybrid integration. Additionally, the fabrication of a dense array of detectors and light sources along with corresponding circuits  30  is easy to implement by conventional Si/Ge processing. 
     In exemplary embodiments, the substrate  12  is an Application Specific Integrated Circuit (ASIC) that is fabricated from the group consisting of: Silicon (Si), Germanium (Ge), Germanium-on-Insulator (GOI), and Gallium Arsenide (GaAs). 
     In exemplary embodiments, chip  10  is merely exemplary of a large area matrix, having an array of dimensions m×n, where m and n are positive integers, may be used without departing from the spirit of the invention. Neither the array nor the elements thereof are necessarily constrained to a rectilinear configuration. 
     Chip  10  comprises an array of a plurality light sources  32  and an array of a plurality of detectors  34 , each operatively disposed in a two-dimensional, m×n matrix form. Each light source  32  and detector  34  defines a pixel and is interconnected with an associated circuit  30 , interconnects those elements to a bus of address lines  18  connecting each element to a processing circuit  36  (see  FIG. 3 ). These buses or lines  18  are formed of an electrically conductive material such as a metal or a thin film conductive oxide. The interconnection functions can be implemented in various forms depending upon the specific system functions desired. 
     In an exemplary embodiment, each of the detectors  34  is preferably an LED. LED  34  has a well known multilayered structure, and rests on substrate  12 . Such an LED can be driven to emit light in response to an electrical signal, and can also produce a detectable electrical signal in response to the absorption of illumination, thus functioning as a photodetector. In the preferred embodiments the detectors  34  are disposed on the same side of substrate  12  so that they are substantially coplanar. Thus the detectors are collocated in a small region, as can be further appreciated with reference to  FIG. 3 , wherein two neighboring diodes  36  are disposed close together on substrate  12 . This arrangement is advantageous in that with appropriate optics (light directing member  40 ), as might be achieved when the image is out of focus, the field of view of a light source  32  can readily be caused to be substantially coextensive with the field of illumination of a neighboring detector  34 . Also if the dimensions of the individual elements as imaged on the indicia substrate  12  are smaller than the substrate diffusion length, then the system will respond as if the two fields of view are substantially coextensive. It will be evident that flood illumination and the detrimental optical effects resulting therefrom can be avoided by disposing the light source  32  with a corresponding detector  34  proximate to each other in view of placement of a light directing member  40  being appropriately placed therefrom for the intended purpose of emitting light  42  from the light source  32  to indicia  50  on a target  52  ( FIG. 3 ). Furthermore, the reflected light  44  from the target  52  is then transmitted through the light directing member  40  and directed to the proper detector  34  neighboring the light source  32  that emitted the initial light  42  toward the target  52  (see  FIG. 4 ). 
     One problem with optical emitters is that the light produced is uncollimated, that is, it will disperse over some angle. As shown in  FIGS. 3 and 4 , light directing member  40  is a lens  40  that can be used to produce collimated light  42 . 
     In a preferred embodiment, lens is attached to an epoxy standoff (not shown), for example, but not limited thereto, surrounding the periphery of the array of devices (not shown) on substrate  12 . Preferably, the standoff (not shown) maintains lens  40  at a suitable height and may surround and protect the array, preventing the flow of glue or other contaminants onto the array. In practice the smallest distance that would still protect the arrays is the most desirable. 
       FIG. 5  illustrates a cross section view of one pixel of the matrix array of a plurality of pixels shown in  FIGS. 3 and 4 . The one pixel of  FIG. 5  includes one light source  32  and a neighboring detector  34  on an insulator film  38  between the substrate  12  and the elements  32 ,  34 . The insulator film  38 , e.g., buried insulator, may be a mirror stack in other embodiments, depending on the intended purpose of the chip  10 . Circuit  30  associated with the elements  32 ,  34  is shown disposed on the substrate  12  and interposed between the elements  32 ,  34 , but is not limited thereto. 
     The processing and/or control circuit  36  associated with each of the elements  32 ,  34 , respectively, is utilized to control electrical current through the light and detector array  10  to only predetermined paths using lines  18  so as to facilitate the discrete addressing of each particular optoelectric element  32 ,  34 . The processing and/or control circuit  36  may comprise a current control device, such as a transistor, a threshold switch, an FET, relay, or the like. 
     In certain applications it may be desired to integrate ancillary electronic circuitry (not shown), such as switches, amplifiers, and the like onto substrate  12 . Such circuits may be coupled to the address lines  18  in accordance with the requirements of the application. The details of fabrication of integrated solid state circuits and m×n arrays of both one and two dimensions are well known and need not be further described herein. 
     It will also be appreciated by those skilled in the art that an optical isolating opaque material may be operatively disposed between the elements  32 .  34  to optically isolate the light sources and detectors from one another and substantially reduce optical crosstalk. For example, the insulator  38  in  FIG. 5  separates two elements  32 ,  34 . 
     As previously mentioned, the invention is preferably practiced with a plurality of identically fabricated LEDs that can be tailored to generate charge when absorbing light radiation, and to emit light when an electrical potential is placed across the layers of semiconductor alloy material so as to forward bias the diode. 
     Each of the elements  32 ,  34  is coupled to conventional electronic circuitry whereby it can be driven as a light source or can be incorporated in a photodetection circuit whereby an electrical signal is generated in response to light that is detected by the diode  34 . Referring now again to  FIGS. 3 and 4 , there is shown a two-dimensional array of photonic elements  32 ,  34  that are switchable by the action of a corresponding switch of a corresponding light source circuit  30  and a light sensor circuit  30 . When a switch of a corresponding light source/light sensor circuit  30  is not engaged, then the corresponding element  32 ,  34  is disabled entirely. The corresponding switch  34  of the corresponding circuit  30  can be a mechanical or electronic switch, operable at a required speed, such as a transistor, relay, diode, and the like. Also in some applications the switch may not be required at all, as the photonic elements  32 ,  34  are connected as sources or detectors to the processing/control circuit  36  via lines  18 . 
     Still referring to  FIGS. 3 and 4 , there is illustrated an exemplary embodiment of the invention, wherein an exemplary 3×4 integrated array comprises photodiodes  34  that are configured as light sensors, and the light emitting elements are microlasers  32 . The photodiodes  34  and lasers  32  are deposited on substrate  12  by methods known to the art, and are electrically isolated from one another by insulator  38  ( FIG. 5 ). Opaque insulating material  38  may be disposed between the photonic elements  32 ,  34  to prevent optical cross-communication therebetween. The lasers  32  and photodiodes  34  are selectively addressed by address bus  18 . The signals are conveyed to processing circuit  36  by signal lines  18 . If desired, greater versatility can be achieved by providing each photonic element  32 ,  34  with a dedicated address line, at a cost in density of component distribution on the substrate or chip  10 . Ancillary electronics (not shown) may optionally be provided as discussed above with reference to  FIG. 3 . The proportion and distribution of the diodes and lasers may be varied in accordance with the needs of the application, the intensity of light emitted by the lasers  32 , and the detection capabilities of the light diodes  34 . This exemplary embodiment can be advantageously employed where intense, coherent light is required, as in optical interfaces and communicators. It will be appreciated that particular lasers  32  may emit light of differing wavelengths, and that the response of light sensors  34  may be individually matched to lasers  32  within array  10 . In this way a plurality of functional subunits (i.e., “pixels”) within the matrix can be established, each producing a signal in response to a different optical characteristic or maintaining an individual optical communication channel. Practical uses for such a matrix will be discussed below. 
     In an exemplary embodiment of the invention depicted in  FIGS. 3 and 4 , there is illustrated an integrated source-detector array, shown as part of chip  10 . Photonic elements comprising light detectors  34  and light sources  32  are shown in an exemplary 3×4 matrix. Light detectors  34  can be p-n diodes, p-i-n diodes, or phototransistors or the like. Light sources  32  are LEDs or lasers. The photonic elements  32 ,  34  are fabricated on a substrate  10  as explained above with reference to  FIGS. 3-5 , and can be provided in desired combinations. Each photonic element has its own data line  18  to external circuitry (not shown). As discussed above with reference to  FIGS. 3-5 , opaque material may be disposed between the photonic elements to prevent optical cross-communication. A proximal end face of a light directing member  40  (e.g., lens  40 ) is disposed in face-to-face proximity with each of the photonic elements  32 ,  34 . The light directing member  40  may be affixes to the chip  10 . In alternate embodiments, the light directing member may include a waveguide, which may be fiberoptic lines, to efficiently transmit light that is emitted from light emitting elements  32  to remote locations and return light from remote locations (e.g., target  532 ) to light sensor elements  34 . Ancillary electronics (not shown) in addition to circuits  30  and  36  may optionally be provided as discussed above. 
     In  FIGS. 3 and 4 , an exemplary matrix of light source elements  32  and light detecting elements  34  are disposed on substrate  12  in pairs, ear pair defining a pixel. The proximal plane of a lens  40  is disposed in face-to-face proximity with each pair of photonic elements  3 ,  34 , while the distal plane of the lens  40  faces a remote location or target  52  with indicia.  50 . Indicia  50  is a barcode as shown in  FIGS. 3 and 4 , but is not limited thereto. Light is thereby intercommunicated between the pair of photonic elements  32 ,  34  and the remote location or target  52 . It will also be appreciated that such systems may be further optimized by the use of other optical elements such as lenses and apertures appropriately designed. 
     The integrated array according to the invention can improve the performance of optical imaging devices. Still referring to  FIGS. 3 and 4 , there is schematically shown an image detector  100  that incorporates an integrated source-detector array chip  10  including the lens  40  according to the present invention. The embodiments of the matrix discussed above are suitable. Areas on substrate  12  are populated by light emitting and light detecting photonic elements, and comprise functional subunits (e.g., pixels) within the matrix. Light beams, representatively denoted by reference numerals  42 ,  44 , are directed between array chip  10  and target indicia  50  by optics  40 . Optics  40  can be a mirror, a lens system, or could be omitted entirely in appropriate applications. While the target  52  is shown as a bar code, it is understood that the device could be designed to read other indicia such as OCR characters, ordinary text, and graphic images. Optics  40  can be designed so that particular regions in which the light emitting and light detecting photonic elements  32 ,  34  spatially correspond in their fields of view and illumination to limited regions on the target  52  with spatial dimensions less than the diffusion length of the indicia substrate. By choosing suitable optics, light emanating from a particular light emitting photonic element  32  will not flood illuminate the target  52 . Control circuit  36  is integrated with the monolithic array chip  10  and coupled to the array of light emitting and light detecting photonic elements  32 ,  34  and can individually address regions corresponding to specific photonic elements  32 ,  34  disposed therein. If desired, regions corresponding to individual “pixels” can be permanently connected or spatially or temporally enabled by control circuit  36  so that the instrument reads selective regions on target  52 , or sequentially reads a plurality of optical characteristics of the target. It will be recalled that the photonic elements  32 ,  34  can be tailored to differ from one another in spectral response. This facilitates the reading of more than one optical characteristic of target  52 . 
     Referring once again to  FIGS. 3 and 4 , when monolithic integrated array chip  10  is constructed in accordance with the embodiments described above, circuits  30  can be operable by a controller such as control circuit  36 . When required, control circuit  36  may cause a desired set of photonic elements  32 ,  34  that are included in each pixel to alternate between a photoemitting and a photodetecting mode so that the instrument can perform optimally under changing conditions. As required in a given application, control circuit  36  integrated with chip  10  may continually enable a set of photonic elements  32 ,  34  of a pixel in a desired mode. 
     The signal produced by each of the light sensors  32  can be coupled to signal processing circuitry of the processing/control circuit  36 . The signal processing circuitry could include a digitizer in the case of a bar code reader that would convert the signal to bit serial form. In the case of optical information having periodicity, the signal processing circuitry may include a processor adapted to signal processing algorithms as required for interpretation of the optical information that is detected by the matrix of photonic elements  32 ,  34 . The output of the signal processing circuitry may be submitted to any suitable display, storage medium, or to a computer or microprocessor. 
     As discussed above, the signal processing circuitry may be colocated on substrate  10  with the matrix of photonic elements  32 ,  34  on the Si or GOI substrate  12 . In applications where the signal processing is complex this may be impractical; nevertheless miniaturization may be achieved by placing the signal processing circuitry with the processing/control circuit  36 , array of photonic elements  32 ,  34  and light directing member  40  in a common housing to be implemented as a single monolithic integrated focal plane array module. 
     In exemplary embodiments as disclosed above, the light emitting elements  32  are selected from a group consisting of: light-emitting-diodes (LEDs), and vertical cavity surface emitting lasers (VCSELs). Likewise, the light sensors/detectors are selected from a group consisting of: photoconducting (PC), and photovoltaic (PV) such as p-i-n photodiodes and metal-semiconductor-metal (MSM) photodetectors. In exemplary embodiments, the detector can be made of Silicon and Germanium as well. However, as will be appreciated by those skilled in the art, other light emitting elements or light sources and light sensors/detectors may be utilized when suitable with the substrate being fabricated from the group consisting of: Silicon (Si), Germanium (Ge), Germanium-on-Insulator (GOI), and Gallium Arsenide (GaAs). In each case, exemplary embodiments include the optoelectronics (light source, detector) and Si circuits on the same chip monolithically (e.g., not packaged or bonded together). 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one ore more other features, integers, steps, operations, element components, and/or groups thereof. 
     The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated 
     The diagrams depicted herein are just one example. There may be many variations to this diagram or the steps (or operations) described therein without departing from the spirit of the invention. For instance, the steps may be performed in a differing order or steps may be added, deleted or modified. All of these variations are considered a part of the claimed invention. 
     While the preferred embodiment to the invention had been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the claims which follow. These claims should be construed to maintain the proper protection for the invention first described.