SCANNER SYSTEM WITH INPUT CAPABILITY

Abstract: A scanner system (10) includes a light source (11) for producing a light beam (12), scanning components (13) for directing the light beam to a spot (14) at a predetermined location relative to the scanning components (13) and for moving the spot (14) along a scan line (15) of specified length at the predetermined location, and a detector arrangement (30) responsive to light reflected from a surface (21) placed at the predetermined location for producing a signal related to a visually discernible pattern on the surface (21). The detector arrangement (30) is exposed to the full length of the scan line (15), preferably being configured to be responsive to light reflected toward it from substantially any point on the surface (21) along the full length of the scan line (15). One embodiment includes an optical element (140) disposed along the scan line (115) intermediate the scan line (115) and the detector arrangement (130).

Description: Scanner system With Input Capability Background of the Invention Technical Field This invention relates generally to laser scanners, and more particularly to a iaser scanner having input capability. Background Information A scanner having input capability is sometimes called a raster input scanner or RIS. It produces a signal related to a visually discernible pattern on a scanned surface and that enables various input functions such as reading a printed document. Some scanners do so by flooding the surface with light and reading reflected energy at each of many closely spaced positions along a scan line in order to produce the desired signal. Since surface reflectivity varies according to the visually discernible pattern, information about the pattern becomes encoded on the signal. Another type of scanner has output capability. Sometimes called a raster output scanner or ROS, such a scanner does the opposite of an RIS, producing a visually discernible pattern on a photoreceptor to enable various output functions such as printing a page. To do so, the scanner directs a light beam to a spot on the photoreceptor, moving the spot along a scan line by such means as a multifaceted rotating polygon while controlling the exposure at each of many closely spaced spot positions along the scan line according to encoded pattern information. Although existing RIS and ROS units operate quite effectively in many respects, certain problems arise in attempting to combine their input and output capabilities in a single multimode unit. In other words, the addition of existing RIS technology to an ROS design involves certain inefficiencies. Two light sources may be required, for example, one to illuminate the scanned surface for input purposes and one to scan the photoreceptor very precisely for output purposes. But that means extra cost, volume, and complexity, and so it is desirable to have some better way to make use of existing ROS components for RIS purposes. Summary of the Invention This invention solves the problem outlined above by providing a scanner that illuminates the surface to be scanned with ROS-type scanning componentry and reads surface reflectivity with a photodetector arrangement exposed to the whole scan line at once. The photodetector arrangement can be small and low cost, and it enables use of existing ROS-type scanning componentry. It eliminates the need for a second light source. It combines RIS and RIS technologies more efficiently. It reduces the size of the multimode unit, and it reduces cost. To better visualize the advantages, recall that existing RIS technology floods the surface with light. So existing RIS detectors must not only read surface reflectivity. They must provide information about spot position as well. But the present invention illuminates just a spot at a time in a precisely controlled manner. Thus, in enabling use of ROS-type scanning componentry the invention also eliminates the need for a detector that provides information about spot position because that information is available from the precise manner in which the ROS-scanning componentry operates. Generally, a scanner constructed according to the invention includes a light source for producing a light beam. That may be an ROS-type component. It also includes scanning components for directing the light beam to a spot at a predetermined location relative to the scanning components and for moving the spot along a scan line of specified length at the predetermined location. That may be an ROS-type component too. In addition, the system includes a detector arrangement responsive to light reflected from a surface placed at the predetermined location for producing a signal related to a visually discernible pattern on the surface. The detector arrangement is exposed to the full length of the scan line and so it enables use of ROS-type light and scanning components instead of having to flood the surface with light from a separate source. Preferably, all those components are contained in a light-tight enclosure. Then only light from the light beam that is reflected from the surface being scanned affects the detector arrangement. In addition, the detector arrangement may include at least one photodetector device that is configured to be simultaneously exposed to light reflected toward it from substantially any point on the surface along the full length of the scan line. Furthermore, the detector arrangement may include at least one detector array having a plurality of detector devices disposed along the scan line. They may be spaced apart a predetermined distance that is proportional to a distance by which the detector devices are spaced apart from the scan line. Preferably, the detector arrangement includes two such arrays disposed along the scan line, each of which is configured as an elongated element with a plurality of photodetector devices, each device being responsive to light reflected from the surface along a portion of the scan line. The outputs of the individual photodetector devices are summed by suitable circuitry while a timing circuit relates the generated signal to the position of the spot along the scan line. Brief Description of the Drawings FIGURE 1 of the drawings is a diagrammatic representation of a scanner system constructed according to the invention; FIGURE 2 is an enlarged diagrammatic representation of the detector element and scanned surface in cross section; FIGURE 3 is a block diagram of the detector element circuitry showing the detector elements, individual amplifiers, and a summing circuit; FIGURE 4 is a representation of a plot showing detector output as a function of spot position; FIGURE 5 is a diagrammatic representation of a second embodiment of a scanner system constructed according to the invention that includes a cylindrically shaped optical element intermediate the scan line and the detector array; FIGURE 6 is an enlarged cross sectional view of the second embodiment taken in the cross-scan plane; FIGURE 7 is a further enlarged cross sectional view taken in the cross-scan plane of a third embodiment having a non-cylindrically shaped optical element; and FIGURE 8 is a diagrammatic representation of a fourth embodiment having a Fresnel lens array between the scan line and the detector array. Description of the Preferred Embodiments Fig. 1 illustrates a scanner system 10 constructed according to the invention. Generally, the scanner system 10 includes a light source 11 for generating a light beam 12 and scanning means 13 for directing the light beam 12 to a spot 14 at a predetermined location relative to the scanning means 13. The scanning means 13 also serves to move the spot 14 along a scan line 15 of specified length at the predetermined location. For that purpose, the scanning means 13 includes a rotatable element or polygon 17 with a plurality of light reflecting facets 18 (eight facets being illustrated) and other known mechanical components that are depicted in Fig. 1 by the polygon 17 rotating about a rotational axis 19 in the direction of an arrow 20. As the polygon 17 rotates, the light beam 12 is directed by the facets 18 toward an image plane at a surface 21 to be scanned, such as the surface of a document 22, scanning across the surface 21 in a known manner along the scan line 15 from a first end 23 of the scan line 15 past a center (the illustrated position of the spot 14) and on to a second end 24 of the scan line 15. Thus, the light beam 12 scans in a scan plane defined as a plane containing both the scan line 15 and a central light beam position that is the position occupied by the light beam 12 when it is directed toward the center of the scan line 15 (i.e., the position of the light beam 12 that is illustrated in Fig. 1) . Those components may be similar in many respects to corresponding components of existing scanner systems and the scanner system 10 may include a post-facet lens system 25 having first and second elements 26 and 27 that compensate for field curvature and wobble. Wobble results in the light beam 12 being directed above or below the scan line 15 in a direction perpendicular to the scan plane as described in U.S. Patent Application Serial No. 496,459 filed March 20, 1990, and that application is incorporated by reference for the details provided. Of course, the post-facet lens system 25 may be omitted without departing from the inventive concepts disclosed. The light source 11 may include a known type of infrared laser diode, and known conditioning optics, for example. It forms a light beam 12 directed at the facets 18 such that the light beam 12 is colli ated in the scan plane and focused in the cross-scan plane. That is done so that the light beam 12 has a proper diameter in the scan plane and a proper Numeric Aperture (NA) in the cross-scan plane. In the scan plane, the conditioning optic can be a single aspheric lens of short focal length, for example, or a laser diode collector which is similar to a microscope objective but designed for infrared light and for infinite conjugates. In the cross-scan plane (i.e., the plane containing both the central light beam position and a line perpendicular to the scan plane) , the optic has the same diode collector, with the addition of a cylinder lens to focus the collimated beam at the facets 18. Suitable light source circuitry turns the light source 11 on and off in order to write on the document 22. Many of those things are well known in the art and reference is made to Brueggemann U.S. Patent NOS. 4,512,625, 4,247,160, 4,230,394, 4,662,709, 4,805,974, 4,682,842, 4,624,528, and 4,595,947 for the various details of scanner system construction provided. For that purpose, reference is also made to Starkweather U.S. Patent Nos. 4,475,787, 3,995,110, 3,867,571, 4,040,096, and 4,034,408. Any of various light sources may be employed without departing from the broader inventive concepts disclosed, however. A major way the scanner system 10 differs from existing designs is in having a detector arrangement 30 as subsequently described with reference to Figs. 1-4. It serves as detector means responsive to light reflected from a surface placed at the predetermined location (e.g., the surface 21) for producing a signal related to a visually discernible pattern on the surface (such as text or graphics) , and it is exposed to the full length of the scan line 15. That enables use of ROS-type scanning components without the need for a separate light source to illuminate the surface 21. The illustrated detector arrangement 30 serves as detector means responsive to light reflected from a surface placed at the predetermined location (i.e., the surface 21 of the document 22) for producing a signal related to a visually discernible pattern on the surface 21. It is exposed to the full length of the scan line 15 in the sense that it is responsive to light reflected from substantially all points on the surface 21 along the scan line 15. Thus, it provides information about surface reflectivity at each spot position or pixel position along the scan line 15. As the light beam 12 scans the spot 14 along the scan line 15, light reflected from the surface 21 impinges upon the detector arrangement 30. That causes the detector arrangement 30 to produce the desired signal, encoded with information about surface reflectivity along the scan line 15. That, in turn, provides information about the visually discernible pattern on the surface 21. Fig. 1 does not include a pattern on the surface 21, but it may typically be text or graphics to be read. From the foregoing and subsequent descriptions, it is apparent that any of various different types of detector arrangements can be used. The illustrated detector arrangement 30, however, includes first and second detector arrays 31 and 32 (Fig. 1) . Each of the detector arrays 31 and 32 includes a plurality of detector devices 33 (three being designated in Fig. 1 for the detector array 31) . They are mounted according to known techniques on some known type of support structure, such as a somewhat resilient strip 34 designated in Fig. 1 for the detector array 31. Each of the detector arrays 31 and 32 includes at least one detector device, preferably a known type of photodetector device. It could conceivably be elongated and disposed along the scan line 15. But as illustrated in Fig. 1, each of the detector arrays 31 and 32 includes nineteen detector devices 33 (preferably photodetector devices) spaced apart one-half inch from center to center (dimension "S" in Fig. 2) . Thus, they extend nine inches along the nine inch scan line 15. They are parallel connected as subsequently described in the sense that they can each contribute to a single output signal from detector circuitry 35 (designated OUTPUT in Figs. 1 and 3) . Preferably, the detector arrays 31 and 32 are located a distance from the scan line 15 that is proportional to that one-half inch spacing. The detector arrays 31 and 32, for example, are located one-half inch from the scan line 15 (dimension "d" in Fig. 2) . Those dimensions are chosen according to known design techniques in view of the characteristics of the detector devices 33, the light beam 12, the reflectivity of the surface 21, and the signal desired. So the dimensions may vary significantly depending on the particulars of a given application. The instantaneous distance of the spot 14 along the scan line from the first end 23 is designated "x" in Fig. 2. As the spot 14 moves away from the first end 23, a lesser proportion of total reflected light impinges upon the detector D.^ while a greater proportion impinges upon the detector D-. The proportion upon D, varies as the cosine to the fourth power of the angle A in Fig. 2 while the proportion upon D, varies as the cosine to the fourth power of the angle B. The output of the detectors D, and D, vary accordingly, as do the outputs of D 3 and the other detectors 33. The output of the detectors D,, D,, and D 3 are represented by the dashed lines at 36, 37, and 38 in Fig. 4, while the solid line at 39 represents the combination of detector outputs. In that regard, the detectors 33 are properly spaced and the detector arrays 31 and 32 are otherwise suitably configured so that the ripple of the OUTPUT does not impair performance. The combination of detector signals leaves a residual ripple as the spot 14 moves along the scan line 15. The ripple is reduced, and the output signal is increased, when the spacing between the detectors 33 is reduced. In using two detector arrays as illustrated in Fig. 1, the detectors are positioned so that the positions of opposing detectors are staggered. That helps minimize ripple. The combination of the outputs of D^, D 2 , and D 3 (i.e., the outputs of the amplifiers) is produced by the detector circuitry 35. In that regard, the detector circuitry 35 may be fabricated according to known techniques as an integral part of the detector arrays 31 and 32 on the strips 34, although it is shown in Fig. 1 as a separate component, and it may include a summing circuit 35a as shown in Fig. 3. The signals from the plurality of detectors D- , D 2 , D 3 ...D n are preferably first amplified by amplifiers A,, A~, 3 ...A^ and the outputs of those amplifiers are coupled to the summing circuitry 35a. The signals from the detectors (i.e., the amplifier outputs) may be combined by simple addition of the signals in a resistor network. Alternatively, they may be combined by using diodes providing an "OR" selection of one of the amplifier outputs. In other words, the OUTPUT is equal to the signal from the amplifier having the greatest amplitude. Consideration of signal to noise ratio involves the source of noise commonly known as "speckle." It results from coherent interference and it can be described as a very irregular pattern of the reflected energy, having many narrow lobes. For the small detectors 33, the lobe pattern may or may not illuminate a given detector. As the spot 14 moves along the scan line 15, those lobes will fluctuate wildly and "dance," causing the energy on nearby detectors 33 to fluctuate, and produce a noise signal. That noise can be reduced by increasing the angle of collection of the reflected energy such that the energy in many lobes is detected. One way that is accomplished is by using many detectors spaced at close intervals, increasing the size of the detectors, or using one long narrow detector. But doing so is counter to the desire to minimize the area of the detector and thus minimize the capacity of the detector, as a fast response and wide bandwidth is required. The angle of collection of energy is increased without increasing the size of the detector by using a cylindrical lens as subsequently described with reference to Figs. 5 and 6. They show a second embodiment or sσanner system 100 constructed according to the invention. It is generally similar in many respects to the scanner system 10 and so only differences are described in further detail. For convenience, numerals designating parts of the scanner system 100 are increased by one hundred over those designating similar parts of the scanner system 10. Like the scanner system 10, the scanner system 100 includes a light beam 112 that is directed to a spot 114 on a surface 121 to be scanned (i.e., the surface of a document 122), and the spot 114 moves along a scan line 115 from a first end 123 of the scan line 115 to a second end 124. In addition, the scanner system 100 includes a detector arrangement 130 that includes a plurality of detector devices 133. But unlike the scanner system 10, the scanner system 100 includes an optical element 140 mounted by suitable known means in a position intermediate the detector device 133 and the scan line 114. It serves to converge reflected light toward the detector devices 133. Stated another way, it increases the angle of collection of energy without increasing the size of the detector. It is in the form of a cylindrical rod, the illustrated optical element 14 being fabricated of suitable known material, such as glass or plastic, in a cylindrical shape according to known optical design techniques. Fig. 7 illustrates a third embodiment or scanner system 200 constructed according to the invention. It is generally similar in many respects to the scanner system 100 and so only differences are described in further detail. For convenience, numerals designating parts of the scanner system 200 are increased by one hundred over those designating similar parts of the scanner system 100. Like the scanner system 100, the scanner system 200 includes an optical element 240 that serves to converge reflected light toward a detector device 233 mounted on a strip 234. Unlike the scanner system 100, however, the optical element 240 is not cylindrically shaped. Instead, it includes a convex surface 241 disposed toward the spot 214 and a flatter surface 242 disposed toward the detector device 233. That configuration facilitates mounting of the detector array and it can simplify fabrication of the optical element 240. To further collection efficiency, the shape and size is optimized for the spacing between the scan line and the detectors, the size of the detectors, and other such parameters. In addition, the detectors are placed into optical contact with the optical element 240 by fabricating the detector and optical element as a single assembly. Fig. 8 illustrates yet another embodiment constructed according to the invention, a third embodiment or scanner system 300. It is generally similar in many respects to the scanner system 100 and so only differences are described in further detail. For convenience, numerals designating parts of the scanner system 300 are increased by two hundred over those designating similar parts of the scanner system 100. Like the scanner system 100, the scanner system 300 includes an optical element 340 that serves to converge reflected light toward a detector array 331 having a plurality of detector devices 333 mounted on a strip 334. Unlike the scanner system 100, however, the optical element 340 includes a plurality of Fresnel lenses 343, one for each of the detector device 333. They serve to converge reflected light from a respective segment of the scan line 315 (a scan segment) to a respective one of the detector devices 333. Thus, reduced scan segments appear at the detector devices 333. In addition, the Fresnel lenses serve the usual function of reducing lens thickness and weight. Stated another way, the array of Fresnel lenses helps increase the collection angle and decrease the detector size. They do that while seemingly demagnifying or reducing the motion of the spot 14. That permits use of smaller detectors with little decrease in the energy that is collected at the detector. There is one Fresnel lens for each detector 333, much like the lens arrays that are used with small LED displays, and it provides imaging of the spot 314 on at least one detector 333 at all times, such that prior to the spot 314 moving out of the field of view of one Fresnel lens/detector element, it will have passed into the field of view of the next Fresnel lens/detector element. In other words, there is a region of overlap. Preferably, the detector signals are combined using the "OR" summing circuitry described previously. That avoids the spike which occurs in the overlap region if the signal is summed. Also, using the "OR" summing circuitry avoids the summation of noise from the detectors not contributing to the signal. Thus, the invention provides a scanner that illuminates the surface to be scanned with ROS-type scanning componentry and reads surface reflectivity with a photodetector arrangement exposed to the whole scan line at once. The photodetector arrangement can be small and low cost, and it enables use of existing ROS-type scanning componentry. It eliminates the need for a second light source. It combines RIS and RIS technologies more efficiently. It reduces the size of the multimode unit, and it reduces cost.

Claims: CLAIMS : 1. A scanner system comprising a light source for producing a light beam; scanning means for directing the light beam to a spot at a predetermined location relative to the scanning means and for moving the spot along a scan line of specified length at the predetermined location; characterized by detector means responsive to light reflected from a surface placed at the predetermined location for producing a signal related to a visually discernible pattern on the surface, which detector means comprises at least one detector device that is exposed to at least a segment of the scan line. 2. A scanner system as recited in Claim 1, wherein the detector means is disposed alongside the scan line. 3. A scanner system as recited in Claim 1, wherein the detector means extends along substantially the full length of the scan line. 4. A scanner system as recited in any one of Claims 1, 2 or 3 wherein the detector device is elongated. 5. A scanner system as recited in claim 4 wherein the detector device includes at least one photodetector device that is configured to be responsive to light reflected towards it from substantially any point on the surface along the segment of the scan line. 6. A scanner system as recited in Claim 1, wherein the detector means includes at least one detector array having a plurality of detector devices. 7. A scanner system as recited in Claim 6, wherein the detector devices include at least one photodetector device. 8. A scanner system as in claim 6, wherein the detector devices are spaced apart along the scan line. 9. A scanner system as recited in Claim 6, wherein the detector devices are spaced apart along the scan line a predetermined distance that is proportional to a distance by which the detector are spaced apart from the scan line. 10. A scanner system as recited in Claim 6, wherein the detector means includes at least two detector arrays disposed along the scan line. 11. A scanner system as recited in Claim 6, wherein the detector array is configured as an elongated element disposed along the scan line. 12. A scanner system as recited in Claim 6, further characterized by means defining a summing circuit for summing the outputs of the detector devices. 13. A scanner system as recited in Claim 6, further characterized by directing means defining an optical element disposed intermediate the scan line and the detector means for directing light reflected from the surface toward the detector means. 14. A scanner system as in Claim 13, wherein the directing means includes a cylindrical lens. 15. A scanner system as in Claim 13, wherein the directing means includes a Fresnel lens. 16. A scanner system as recited in Claim 13, wherein the detector means is characterized by at least one detector array having a plurality of detector devices disposed along the scan line; and the directing means is characterized by a Fresnel lens array having a plurality of Fresnel lenses disposed along the scan line, each Fresnel lens being configured to direct light reflected from the surface along a respective segment of the scan line toward a respective one of the detector devices. 17. A scanner system as recited in Claim 6, wherein the detector device is configured to be responsive to light reflected toward it from substantially any point on the surface along the scan line. 18. A scanner system as recited in Claim 6, wherein the detector device includes at least one photodetector device that is configured to be exposed to light reflected toward it from substantially any point on the surface along the segment of the scan line. 19. A scanner system having input as well as output scanning modes, comprising means defining a light source for producing a light beam, said light beam encoded with information regarding a visually discernible pattern when in the output scanning mode; single scanning means, for both the input as well as output scanning mode, for directing the light beam to a spot and moving the spot along a scan line of specified length; characterized by: for the input scanning mode, detector means responsive to light reflected from a surface placed at a predetermined location for producing a signal related to a visually discernible pattern on the surface; and for the output scanning mode, means for outputting the visually discernible pattern as encoded in the light beam and represented by the scan line. 20. A scanner system as in claim 19 wherein the detector means comprises a detector array having a plurality of detector devices. 21. A scanner system as in claim 20 wherein the detector devices are disposed along the scan line. 22. A scanner system as in claim 20 further comprising directing means for directing light reflected from the scan line to the detector devices. 23. A scanner system as in claim 22 wherein the directing means comprises at least one lens for converging light reflected from the scan line to the detector devices. 24. A scanner system as in claim 19 wherein the detector means comprises at least one elongated detector device. 25. A scanner system as in claim 24 wherein the detector device is disposed alongside the scan line.

Inventors: BRUEGGEMANN HARRY PAUL, SWANBERG MELVIN E, BRUEGGEMANN, HARRY, PAUL, SWANBERG, MELVIN, E.
Applicants: S & R TECH DEV, S & R TECH DEVELOPMENT
Application year: 1991
Main classification: H04N1
IPC codes: H04N1