Abstract:
An optical character reader for conversion of information to a machine readable code from a strip of alpha-numeric characters on the face of a document. It includes an elongated document slot along which the document may be hand guided through a predetermined path. Optical viewing means is provided across a scan line intersecting the path of the alpha-numeric characters. A character scanning assembly electronically generates images of each character. Recognition processing means encodes these images into a machine readable code. All of the physical, optical and electronic components are contained within a compact single enclosure. Incandescent lamps are utilized to illuminate the document face across the scan line. The usable life of each lamp is extended by providing a constant current source in the operational lamp circuit. Incandescent lamps are utilized to illuminate the face of the document across the scan line. Lamp life is extended by dimming of the lamps when they are nonoperational, maintaining the lamps in a state of excitation beyond the crystalline state of the material comprising the lamp filaments. A second form of lamp life extension is provided by interposing a constant current source in the electrical power supply connected to the lamps in their operational state.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a document guide and recognition apparatus for machine reading of alpha-numeric characters that appear on the face of a document. It constitutes a manually fed slot reader, where the document is moved longitudinally by the user through a defined path on the equipment in order that its contents might be optically scanned and encoded into a machine readable code. The apparatus constitutes a self-contained remote peripheral which can be coupled to a host processor. 
     One problem encountered in the design of a compact self-enclosed scanner is the limitations of normal lamp life in the lamps used for illuminating the face of the document across a transverse scan line. Lamp life becomes critical to projected servicing of the equipment, particularly when access to the lamps is difficult or can be accomplished only under factory servicing conditions. 
     According to this disclosure lamp life is extended by dimming the lamps when they are not in use. Sensors are provided along the document path to sense the presence of incoming documents and automatically increase the brilliance of the lamp illumination for scanning purposes. When no document is present in the apparatus, the voltage drop across the lamps is reduced to a level at which the lamp excitation is slightly beyond the level at which the lamp filament material would return to a crystalline state. By eliminating the crystalline state of the filament, filament damage due to vibration and aging is substantially reduced. 
     In addition, lamp life is extended by utilizing a constant current source in the power supply for the lamps when they are operational. A constant current flow through the lamps counters the normal tendency of the lamps to be subjected to increased electrical current as they age, which is brought about by the progressive reduction in filament resistance. These electrical systems have substantially extended projected lamp life in the apparatus and have effected reductions in the frequency of service required to maintain proper lamp intensity for scanning purposes. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the apparatus, illustrating its use; 
     FIG. 2 is a fragmentary plan view of the apparatus; 
     FIG. 3 is a sectional view taken along line 3--3 in FIG. 2; 
     FIG. 4 is a sectional view taken along line 4--4 in FIG. 2; 
     FIG. 5 is an exploded view of the document slot and character scanning assembly; 
     FIG. 6 is an enlarged plan view of the character scanning assembly; 
     FIG. 7 is a corresponding elevation view; 
     FIG. 8 is an enlarged sectional view taken along line 8--8 in FIG. 7; 
     FIG. 9 is a sectional view taken along line 9--9 in FIG. 8; 
     FIG. 10 is a sectional view taken along line 10--10 in FIG. 8; 
     FIG. 11 is a schematic flow diagram of the electronic components; and 
     FIG. 12 is a schematic wiring diagram of the lamp circuits. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present disclosure relates to a compact, manually fed optical character recognition device in which documents are moved along a slot for reading purposes. It is designed for reading a longitudinal strip of visual indicia 11 containing discrete alpha-numeric characters located along the face 12 of a document 10. The document 10 illustrated in FIG. 1 is a conventional check blank used for commercial banking purposes and having a printed line of machine readable information that typically identifies the bank, the user&#39;s account, and the amount of the check. 
     The document 10 has a constant thickness and can be made from a sheet of paper, paperboard, plastic or other suitable sheet material. Its face 12 is bounded along one side by a planar longitudinal reference edge 13, which in this illustration constitutes the bottom edge of the rectangular check blank. Document 10 has a predetermined width dimension in a direction perpendicular to the reference edge 13. This width dimension would be measured across the end edges 14 which extend between the reference edge 13 and the remaining longitudinal edge 15 presented along the top of the check blank. 
     A strip of visual indicia 11 is located on the face 12 within transversely spaced boundaries that are parallel to one another and are also parallel to the lower reference edge 13 of document 10. In this illustration, these boundaries are coincident with the upper and lower edges of the alpha-numeric characters imprinted on the check blank. 
     As a general definition of the document geometry pertinent to this disclosure, the strip of visual indicia will have a transverse width perpendicular to the document reference edge and will be arranged parallel to said edge. 
     The present apparatus is provided within an enclosure generally designated at 16. The enclosure 16 has outer surfaces including an upper longitudinal wall surface 17, a front wall surface 18, a rear wall surface 20 and oppositely facing end wall surface 21. The enclosure 16 as illustrated is rectangular in shape, and contains all the interior components of the apparatus in the completed assembly (FIGS. 1 through 4). 
     The upper wall surface 17 and end wall surfaces 21 are interrupted by a longitudinal document slot 22. Slot 22 intersects the walls on which these surfaces are formed and which extends the full length of enclosure 16. Slot 22 is a document guiding apparatus by which individual documents 10 can be fed longitudinally the length of the enclosure 16 to permit machine reading of the strip of visual indicia 11. 
     Located within enclosure 16 is a rigid frame generally shown at 33. The frame 33 includes the stationary support elements for the various components of the apparatus. It includes upwardly protruding front and back longitudinal walls 23, 24 which are located in close opposed positions. The walls 23, 24 have respective opposed inner surfaces 25, 26 spaced apart transversely by a distance adequate to receive the thickness of a document 10 between them. They include coplanar longitudinal upper edges 28, 30 and coplanar outer ends 31, 32, respectively. A base 27 extending between the inner surfaces 25, 26 of the two walls 23, 24 completes the boundaries of document slot 22. Base 27 is positioned at a location spaced inwardly from the longitudinal upper edges 28, 30 of walls 23, 24 a distance less than the height across the document 10. The upper edges 28, 30 are located in close proximity to the upper longitudinal wall surface 17 of enclosure 16. The slot depth is such that a document 10 can be manually moved within it in a longitudinal direction with respect to the rigid frame 33 and enclosure 16. Document 10 is hand-held and guided along slot 22 by sliding engagement of base 27 by the document reference edge 13. This general operation is illustrated in the view shown in FIG. 1. 
     To facilitate entry of document 10 within document slot 22 from either end of enclosure 16, the outer ends of slot 22 are formed by inwardly converging surfaces 34, 35 formed at the respective longitudinal ends of the front and back walls 23, 24. The slot access openings presented by the exterior wall surfaces 17 and 21 of enclosure 16 are correspondingly tapered in shape (FIG. 1). However, the operational section of slot 22 intermediate its ends is formed with the inner surfaces 25, 26 of the front and back walls 23, 24 parallel to one another and spaced apart a distance slightly greater than the thickness of the document 10 designed to be fed between them. 
     The general assembly of the apparatus essentially comprises character scanning means 36 mounted to the frame 33 and located within enclosure 16 for electronically generating images of each alpha-numeric character. As will be described below, the character scanning means 36 is mounted on a separable support frame 37 that is detachably fixed to and forms part of rigid frame 33. The electronic components of the character scanning means 36 are located on a printed circuit board 58 fixed alongside front wall 23 (FIG. 3). 
     The apparatus is completed by electronic recognition processing means located on the rigid frame 33 and also positioned within an enclosure 16. The recognition processing means 38 is operatively connected to the character scanning means 36 for analyzing the electronic images generated thereby and for encoding the images into a machine readable code. It provides the final coded information at output terminals 40 adapted to be wired to the Host Processor (not shown). 
     The recognition processing means is located on a printed circuit board 41 rigidly secured to end support brackets 42, which in turn also mount the slot structure presented by walls 23, 24 and base 27. The electronic components of the character scanning means 36 on circuit board 58 are connected to components on the board 41 through ribbon conductors 60, 61 arranged between the two upright boards. While the precise arrangement of the electronic components is not critical to an understanding of this invention, it is to be noted that all electronic components of the reader assembly are fully contained within the compact enclosure 16. 
     As an example of the practical application of this equipment, the illustrated apparatus might read a printed strip of visual indicia 11 on the face 12 of a check blank and be utilized by bank tellers to verify the status of a customer&#39;s account by access to information stored in a central computer memory. It might be similarly used by personnel in sales establishments to verify the status of a checking account balance before accepting or cashing the check written on the face 12 of the document 10. 
     The details of the character scanning means 36 are best illustrated in FIGS. 5 through 10. The character scanning means 36 is mounted to the upright wall 43 and protruding shelf 44 of the separable support 37 as a subassembly which permits prealignment of the physical components of the scanning means prior to assembly on the remaining elements of the rigid frame 33. This also permits these components to be pre-aligned and readily replaced as a unit for servicing purposes. 
     The support frame 37 includes a stationary wall surface area 45 (FIG. 10) which is adapted to be slidably engaged by the document face 12. The section of upright wall 43 about area 45 serves as a document viewing assembly for reflecting light from the strip of visual indicia 11 on document 10. The details of this assembly are shown in FIGS. 8-10. 
     The front wall 23 along the open slot 22 has a complementary opening at 46 to receive the wall surface area 45 of the frame 37 in a position at which the surface area 45 is substantially coplanar to the inner surface 25. To assure sliding engagement of the document face 12, it is preferable that the area 45 be slightly radiused and protrude very slightly beyond surface 25 and extend within the confines of slot 22. 
     The opening 46 is located elevationally between the slot base 27 and the longitudinal edges 28, 30 of the walls 23, 24. The distance between base 27 and the mounted wall surface area 45 corresponds to the transverse separation between the lower reference edge 13 of document 10 and the strip of visual indicia 11. Thus, the moving strip of visual indicia 11 will overlap the stationary area 45 as the document 10 traverses the length of slot 22. 
     Light means is provided on the frame 37 for directing light onto the face 12 of a document 10 across the moving path of the strip of visual indicia 11. This light means is illustrated as four incandescent lamps 47 mounted to the back of printed circuit board 58 and recessed within the upright wall 43 immediately outward from the wall surface area 45 (FIG. 8). The light means also includes upright light guide slots 48 which converge toward one another from the lamps 47 and openly intersect the critical wall surface area 45. 
     Light sensing means 50 is mounted to shelf 44 of frame 37 for producing analog signals at individual terminals proportional to the level of light intensity directed to them. Means 50 in general comprises an array or matrix of light-responsive sensors for detecting the geometric relationship of light values directed upon it. The unit illustrated is a conventional self-scanning linear photodiode Array which consists of a single vertical row of silicon photodiodes. The individual output terminals are shown as a bundle of conductors 51 leading to a receptacle 52 at one end of wall 23 (FIG. 3), which in turn is wired to the proper components on the printed circuit board 41. 
     Optical viewing means is used between the light means and array 50 to direct reflected light from the face of document 10 to the array of photodiodes. The optical viewing means includes a narrow vertical viewing slot 53 that centrally intersects the two light guide slots 48 at a plane slightly recessed from the wall surface area 45 (FIG. 8). The width of the knife edge slot 53 is sufficiently narrow to have an aperture function in assuring viewing depth of field through it across the permissible planar locations in which the face 12 of a document 10 might be viewed within document slot 22. The narrow field viewable through the viewing slot 53 constitutes a scan line which is physically positioned with respect to document slot 22 so as to transverse the strip of visual indicia 11. The side edges of slot 53 formed through the upright wall 43 of subframe 37 converge outwardly to permit maximum reflectance of light through the thickness of the upright wall 43. The light path, which is initially perpendicular to the wall surface area 45, is turned 90° by the reflective surface of a mirror 54 mounted at an angle of 45° across shelf 44, and is beamed to focusing lenses 55, 56 arranged along shelf 44 to properly direct the reflected light patterns from slot 53 onto the photodiodes of the Array 50. The lenses 55, 56 and Array 50 are aligned parallel to the wall surface area 45. 
     Since the separable frame 37 contains the surface area 45 which the field viewable through slot 53 must engage, the entire optical path from document 10 to Array 50 can be prealigned on frame 37 independently of the remaining components of the reader. This is much less cumbersome than the alternative of aligning the components on the total assembly and eliminates alignment of individual elements when servicing the equipment. Frame 37 is fixed as part of rigid frame 33 by releasable screws 39 (FIG. 3). 
     Referring now to FIGS. 8, 9 and 10, the wall surface area 45 includes provision for dispersal of environmental dust and solid particles that might otherwise collect about the area of the viewing slot 53 as documents 10 are fed past it, particularly when the documents are made from paper or paperboard. To minimize the difficulties that are encountered due to dust, upright ventilation ducts 57 are formed within the upright wall 43 and surround the lamps 47. They openly intersect the light guide slots 48. As discussed previously, lamps 47 are preferably of the incandescent type, but might be any suitable heat emitting light source. 
     The ventilation ducts 57 provide convection cooling of the lamps 47 or other light means and dispersion of environmental dust in the vicinity of the viewing slot 53. Each duct 57 extends through the height of the upright wall 43 within the subframe 37 (FIG. 9) and has open communication in frame 33 beyond the boundaries of the upright wall 43 at positions above and below the width of slot 53. The lower end of each duct 57 is open and unobstructed in the completed assembly. Ventilation of the upper end is assured through open communication along mating duct extensions 59 in wall 23 (FIGS. 3, 5). 
     As can be seen in FIG. 9, ducts 57 are preferably cylindrical apertures formed parallel to one another and extending through the full height of wall 43. Ducts 57 are in open communication with the complete height of each light guide slot 48. Upright movement of air within ducts 57 will tend to also draw air (and small dust or solid particles) from the edges of the viewing slot 53. The moving currents of air will tend to disperse this dust outside the viewing slot area, where it can come to rest on horizontal surfaces within the enclosure 16 not critical to the optical path of the character scanning means. 
     FIG. 11 schematically illustrates the electronic components of the character scanning means 36 and the recognition processing means 38, which are generally outlined within dashed line boundaries. 
     The character scanning means 36 includes Array 50, which is illustrated by the RL 256G Array made by Reticon Corporation of Sunnyvale, California. This is a 256 element photodiode array of photodiodes as generally described above. It is connected to an Array Drive 60, which provides all the necessary signals to interface to and provide control of Array 50 as specified by its manufacturer. The Array Drive 60 also generates all the required signals to control the Quantizer 61 and the Transition Processor and Counter 62. 
     The Quantizer 61 basically functions as a comparator. The analog video signal directed to it from Array 50 is compared within its circuitry to a reference voltage source. This reference voltage value was derived as a preselected percentage of the output from a peak white sample and hold circuit within the Quantizer. A peak white follower circuit of the Quantizer tracks the maximum amplitude of the video signal coming from Array 50. The output of the Quantizer comprises digitized video information corresponding to the light values received on the individual photodiodes in Array 50. 
     The Transition Processor and Counter 62 is a digital video processor which takes the digitized video information from Quantizer 50 in the form of a serial bit stream and analyzes it, one bit at a time, looking for valid transitions. A valid white to black transition for this reader was defined as a sequence of at least two consecutive white bits of information followed by at least two consecutive black bits. Similarly, a valid black to white transition is the reverse of this sequence. The circuit also counts the number of white or black bits received between valid transitions. The white and balck count information is then passed on to the Direct Memory Access circuit 63. 
     The Direct Memory Access circuit receives count information from Transition Processor and Counter 62. This count information is then deposited into Picture Buffer 64. The Direct Memory Access scheme used in this reader is a pseudo cycle stealing type technique, where all accesses are done during Phase I. Therefore no central processor time is lost doing memory accesses. 
     The Picture Buffer 64 contains 16 bytes of Random Access Memory, which are organized into two columns, 8 bytes each. It also has separate Data-In and Data-Out ports. The picture buffer is therefore a Read Only port for the recognition processor 65 and a Write Only port for the Direct Memory Access circuit 63. The Picture Buffer 64 appears to be only one column long to both the recognition processor 65 and the Direct Memory Access circuit 63, because address bit 3 is not used by either circuit, thus utilizing a memory mapping technique. However, the logic state of address bit 3 is changed once every scan of the Array 50, which effectively causes the memory remapping function. 
     The recognition processor 65 is a Motorola MC6802 n-channel 40 pin Integrated Circuit. It is manufactured by Motorola Corporation of Phoenix, Arizona. It executes 72 variable length instructions and is also capable of directly addressing 65K bytes of memory. The 6802 Microprocessor contains 128 bytes of internal Random Access Memory starting at address 0000 and going to 007F (hexadecimal). It is properly programmed to carry out the logical functions necessary for operation of the reader as described above. 
     The memory address space of the microprocessor 65 has been allocated to Read Only Memory, Input/Output, Picture Buffer, and Debug equipment needs. 
     There are no specific Input/Output instructions for the 6802 Microprocessor. Therefore, Input/Output is done by using the &#34;Memory Mapped&#34; technique. This means that outputs from this system are the same as a memory write, and inputs are the same as a memory read. 
     The recognition processor memory (ROM) 68 within is basically split into two halves. The top half is reserved for Debug equipment usage and the bottom half is allocated to the recognition part of this system. 
     Since address bits 13 and 15 are not used in this system, the memory space allocated for the Recognition Program in memory 68 is replicated many times. The preferred memory space that should be used for the Recognition program is 7800 (Hexadecimal) to 7FFF (Hexadecimal). 
     The Picture Buffer is first located in memory at 1000 (Hexadecimal) to 1007 (Hexadecimal). 
     The Asynchronous Communications Interface Adaptor (ACIA) 66, conforms to an Electronic Industries Association Standard RS232C having a port first located in memory at 1400 (Hexadecimal) to 17FF (Hexadecimal). 
     The output terminals at customer Input/Output port 40 provide a wired communication path which consists of Receive Data and Transmit Data. This path provides means for connection to the Host Processor (not shown). 
     The reader is also provided with two control sensors 70, 71 that are physically mounted on wall 23 at opposite sides of the viewing slot 53 (FIG. 5). They enable the recognition processor 65 to identify the direction of travel of each document 10 moved through the slot 22. They are operably connected to the sensor port shown at 72. 
     Because of the miniaturization of this apparatus and the relatively inaccessible positions of the lamps 47, it was found essential to provide circuitry to maximize the life of the lamps. This has been successfully accomplished through two different electronic systems in addition to the desirable cooling effect of the ventilation ducts 57 described above. 
     Sensor port 72 is also operably connected to two additional sensors 73, 74, whose circuitry is shown in FIG. 12. The sensors 73, 74 are physically located at positions longitudinally outward from the corresponding sensors 70, 71. They are utilized to vary the brightness of the lamps 47 from normal readiness state to a brighter operational state. The additional separation between sensors 73, 74 and the scan line provides sufficient time for the lamps to reach full brightness prior to reading of the strip of visual indicia 11 on the face 12 of a document 10 being fed through the reader. 
     As shown in FIG. 12, the four lamps 47 are preferably wired in series between a common terminal 75 at a first potential and alternate terminals 76 and 77 at two different voltage potentials. The voltage drop from terminal 75 to terminal 76 equals that required for normal full brightness of the operational lamps 47. The voltage drop between terminal 75 and 76 is substantially less, but is adequate for their readiness state, to maintain a visible incandescent glow in the lamps 47 and to assure that their state of excitation remains beyond the crystalline stage of the lamp filaments. By maintaining the lamps at a constant condition beyond the crystalline state of the filament the circuitry eliminates normal damage which would otherwise occur due to vibration of the cold lamp filaments. The circuit connecting the lamps 47 across the terminals 75 and 76 is normally open, but is completed by a transistorized switching circuit including transistors 78, 79. 
     When either sensor 73, 74 is turned off by passage of a document 10 between one sensor 73 or 74 and a corresponding Light Emitting Diode 80 or 81, the transistor 78 will become conductive and the voltage drop between terminals 75 and 76 will be applied to the lamp circuit. Conversely, when no document is within the slot 22, the transistor 78 will be inoperative and the lower voltage drop between terminals 75 and 77 will be applied across the lamp circuit. 
     To further extend lamp life, a constant current is supplied to the lamps 47 when they are in their operational or full brightness condition. This counteracts the normal tendency of an incandescent lamp to draw increased amounts of current with age, in response to decreasing lamp resistance. This normally causes the lamp to become increasingly brighter and progressively increases the rate of lamp aging until failure occurs. 
     Constant current through the lamps 47 is assured by interposing a Constant Current Regulator 81 between the terminal 75 and the first lamp 47. The Constant Current Regulator 81 is operational when the full operational voltage between terminals 75 and 76 is applied across the lamp circuit. It is not functional during application of the reduced voltage. A typical Constant Current Regulator is exemplified by Model LM317KC, manufactured by National Semiconductor Corporation of Santa Clara, California. 
     Various modifications might be made with respect to specific electronic components of this invention. The functional attributes of these components are therefore the only details believed to be essential to an understanding of the invention disclosure.