Abstract:
A scanner system and method are described, wherein two lenses are mounted on a slider positioned in the optical light path between two moving mirrors and the optical sensor. Each mirror is mounted on a moving carriage. The slider is bistable in two alignment positions, one for each lens. The slider is moved by the motion of one of the carriages. As the carriage moves toward the lens slider, a linkage causes the slider to move from the position it is currently in to the other position. This system allows the slider to be shuttled from one position to the other, thereby changing resolutions, using energy provided by the same motor that moves the mirrors.

Description:
TECHNICAL FIELD OF THE INVENTION 
     This invention relates to optical scanning systems, and more particularly to techniques for providing multiple resolutions. 
     BACKGROUND OF THE INVENTION 
     Moving mirror scanning systems are known, wherein two mirrors are moved relative to a target to be scanned to direct a reflected beam to a sensor. It would be advantageous to provide a technique for changing the resolution of the system without requiring a separate motor for changing lenses. 
     SUMMARY OF THE INVENTION 
     In accordance with an aspect of the invention, a scanner system is described, wherein two lenses are mounted on a slider positioned in the optical light path between two moving mirrors and the optical sensor. Each mirror is mounted on a moving carriage. The slider is bistable in two alignment positions, one for each lens. The slider is moved by the motion of one of the carriages. As the carriage moves toward the lens slider, a linkage causes the slider to move from the position it is currently in to the other position. This system allows the slider to be shuttled from one position to the other, thereby changing resolutions, using energy provided by the same motor that moves the mirrors. 
     In accordance with another aspect, methods are described for changing imaging resolution in an optical scanning system having a fixed optical sensor, and a moving carriage. An exemplary method includes: 
     moving the carriage to a position outside a normal scanning area; 
     engaging a slider linkage coupled to a slider structure which is movable between a plurality of home positions, the slider structure having mounted thereon a plurality of lenses of different optical power, wherein each said home position positions a corresponding one of said lenses in an optical scanning path for the system; 
     moving the slider structure to a home position by a driving force provided by motion of the carriage and the slider linkage; and 
     disengaging the carriage from the slider linkage. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     These and other features and advantages of the present invention will become more apparent from the following detailed description of an exemplary embodiment thereof, as illustrated in the accompanying drawings, in which: 
     FIG. 1 is a diagrammatic top view of an exemplary embodiment of a scanner system in accordance with the invention. 
     FIG. 2 is a cross-sectional view taken along line  2 — 2  of FIG.  1 . 
     FIG. 3 is a broken-away view illustrating the spring-detent feature of the lens slider. 
     FIG. 4 is a partial view of the slider linkage taken in the direction of line  4 — 4  of FIG.  1 . 
     FIG. 5 is a cross-sectional view taken along line  5 — 5  of FIG.  4 . 
     FIG. 6 is a cross-sectional view taken along line  6 — 6  of FIG.  4 . 
     FIG. 7 is a view similar to FIG. 4, but showing the rod at the opposite end of its range of motion. 
     FIG. 8 is a cross-sectional view taken along line  8 — 8  of FIG.  7 . 
     FIG. 9 is a partial top view of the scanning system of FIG. 1, showing the reflector carriage at the commencement of an actuating cycle. 
     FIG. 10 is a cross-sectional view taken along line  10 — 10  of FIG.  9 . 
     FIG. 11 is a top view similar to FIG. 9, showing the reflector carriage near the end of an actuating cycle. 
     FIG. 12 is a cross-sectional view similar to FIG. 10, but showing the pushrod in the lower position, out of engagement with the carriage hook. 
     FIG. 13 is a top view of the scanning system of FIG. 1 showing a high resolution lens field of view. 
     FIG. 14 is a cross-sectional view illustrating the slider structure mounted on the bracket structure of the scanning system of FIG.  1 . 
     FIG. 15 is a diagrammatic view illustrating an exemplary cabling drive arrangement for the scanning system of FIG.  1 . 
     FIG. 16 is a schematic block diagram of an exemplary control system for the scanning system of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An exemplary embodiment of a dual resolution scanning system  50  in accordance with the invention is illustrated in FIG.  1 . This diagrammatic top view does not show the glass platen situated above the scanner elements shown to support the target to be scanned. The system includes a pair of spaced carriage slider rods  52 ,  54  which are mounted to a frame structure (not shown). These rods support a scan carriage  60  and a mirror carriage  70  for sliding movement along the rods, to traverse the scan image area  56 . The scan carriage  60  carries an elongated light source  62 , such as an array of LEDs, cold cathode fluorescent (CCFL) tube or a Xenon tube. In an exemplary embodiment, the light source is a CCFL tube 9 inches long and 3 mm in diameter. The light source is energized during scanning operations to illuminate the target with light, and illumination light reflected from the target is reflected onto mirror  64  also carried by the carriage  60  toward a mirror system  72  carried by the reflector carriage  70 . The reflected light is in turn redirected by the mirror system  72  toward an optical sensor  80  mounted on a stationary housing  82 , through a lens. In an exemplary embodiment, the sensor is a linear CCD array of light sensitive elements or pixels. The lens focusses the light on the sensor elements. 
     The two carriages  60  and  70  are moved by a cable/pulley/motor drive system  210  (FIG. 16) which is known in the art. The drive system typically moves the scan carriage at twice the rate of the reflector carriage. An exemplary cabling arrangement is shown in FIG. 15, wherein cable  216  has its ends  216 A,  216 B fixed as generally illustrated. The cable is reeved about pulleys  214 ,  218 ,  220 , and fixed to the scan carriage  60 . Pulleys  214  and  218  are mounted at fixed locations relative to the scanner frame. Pulley  220  is a double pulley mounted on the reflector carriage  70  for rotation. This type of cabling system results in the scan carriage being driven at twice the rate of the reflector carriage. 
     To the extent just described, the scanner system  50  is conventional. In accordance with an aspect of the invention, the system is provided with a multiple lens system to provide multiple scan resolution. The lens system is actuated by the motion of a carriage. As a result, a separate lens drive system with its own motor is not needed. 
     The sensor housing  82  is mounted on a bracket structure  88 . The structure  88  has formed therein slots  90  and  92  positioned at respective acute angles with respect to the carriage rods  52 ,  54 . Also mounted on the bracket  88  is a slider structure  90 . The slider structure has mounted thereon the two lenses  84 ,  86  and is slidable along axis  92  in a direction transverse to the orientation of the rods between two home positions. One home position is shown in FIG. 1, and is the position orienting lens  84  in the optical path between the target and the sensor  80 . This lens  84  is the low resolution lens, and will scan the full width of the target page and image it onto the full width of the sensor array. The second home position is shown in FIG. 13, and is the position orienting lens  86  in the optical path between the target and the sensor. The lens  86  is the high resolution lens and will scan a portion of the width of the target page and image it onto the full width of the sensor  80 . The smaller the portion of the target width scanned, the higher the resolution. If half the target width is scanned, the resolution will be double the normal resolution. 
     An exemplary embodiment of the sensor  80  is a 5300 pixel CCD array, which can provide 600 pixel per inch (PPI) scan resolution when used with a lens  84  having an optical power for providing a full target (page) width image onto the sensor. The lens  86  images less than the full page width onto the CCD array, and this provides a higher resolution scan over an area the full length of the target page but only partial width. For example, if one quarter of the width of the page is imaged by the lens  86 , the resolution for a 5300 pixel CCD sensor would be 2400 PPI. 
     To change the resolution, a pushrod linkage coupled to the slider structure  90  is actuated by the reflector carriage. The linkage includes two pushrods  100 ,  102 , respectively pivotally connected to opposite lateral edges of the slider structure  90 . A pin  100 A is passed through an opening in the slider end  100 B of the pushrod  100  to pivotally mount the slider end of the pushrod  100  to the slider structure. A pin  102 A is passed through an opening in the slider end  102 B of the pushrod  102  to pivotally mount the slider end of the pushrod  102  to the slider structure. The distal ends  100 C,  102 C of the pushrods have hooks  100 D,  102 D extending upwardly for engagement with corresponding hooks carried by the reflector carriage. Only one of the pushrods will be positioned with its hook in position for engagement by the scanning carriage hook. 
     A detent mechanism is employed to force the slider structure to move to a home position as it is pushed by a pushrod to approach the home position. There are two home positions, one for the low resolution lens and the other for the high resolution lens. FIGS. 2,  3  and  14  illustrate the detent mechanism. The slider structure  90  is positioned for sliding movement on a planar surface of top structure  89  attached to the bracket  88 . The slider structure includes a protruding beveled surface with a first ramp  90 A, a second ramp  90 B and a flat surface  90 C between the ramps. Mounted to the structure  89  is a spring-loaded plunger  110 . The plunger and a spring  112  are captured in a cylindrical opening in boss  114  mounted to top structure  89 , so that the spring biases the plunger to an extended position, but allows the plunger to be retracted within the boss under force. The plunger tip rides along the surfaces of the slider structure, so that as the slider structure is moved by a pushrod, the plunger tip will ride up a ramp to the flat surface  90 C, storing energy in the spring. As the slider structure is pushed further by the pushrod to the opposite ramp, the energy stored in the spring will ensure that the slider will move all the way to the home position even if no more pushing force is applied by the pushrod. This spring energy will cause the active pushrod to move ahead of the reflector carriage and drop down into its guide, as will be described below. 
     The slider structure  90  is held against the top structure  89  by leaf springs  91 A,  91 B, which are captured between surfaces of the slider structure  88  and top lips  82 A,  114 A (FIG.  14 ). The leaf springs provide bias forces to insure that the slider  90  remains in aligned position relative to the slide axis. 
     Each pushrod hook member is formed on a rod which extends into the corresponding slot  90 ,  92  formed in the bracket structure. An exemplary hook member rod is shown in FIGS. 4-8. Here, the hook  100 D is formed on one end of rod  100 E which is fitted transversely into an eye opening formed at the end of the pushrod  100 . The hook has a ramp surface  100 D 1 . The opposite end  100 F of the rod travels in the slot  90 , constraining the movement of the distal end  100 C of the pushrod to follow the contour of the slot. 
     The distal end  100 C of the pushrod includes an end shoulder surface  100 C 1  which rides on a cam surface  120  defined in the wall  88 A of the bracket structure along the slot. The surface  120  has an elevated portion  120 A, a ramp portion  120 B and a lower portion  120 C. FIG. 4 illustrates the pushrod  100  in a back, elevated position, wherein the tip of the pushrod is in contact with the elevated portion  120 A of the cam surface, and the hook  100 A is positioned for engagement by the reflector carriage hook, if the carriage is moved to the engagement position. 
     FIG. 7 is a view similar to FIG. 4, but showing the pushrod in a forward position, wherein the pushrod tip is in contact with the lower cam surface  120 C. In this position, the pushrod tip is lowered such that the hook  100 D is beneath the level of the carriage hook, and so the carriage hook will not engage the pushrod hook. The two elevations of the pushrod hook are also shown in FIGS. 5 and 8. 
     FIGS. 9-12 show the operation to switch from the low resolution lens  84  to the high resolution lens  86 . With the slider structure  90  in its home position for low resolution scanning, the lens  84  is in the optical path of the reflected light energy. With the slider structure in this home position, the pushrod  100  is positioned in a rearward position, with its hook  100 C in the raised. position illustrated in FIG.  4 . To move the slider structure  90 , the reflector carriage  70  is moved in a rearward direction, in the direction of arrow  120 A (FIG.  9 ), to an area outside a reflector carriage scan mode range of travel. A boundary  56 A of this range of travel is indicated in FIG.  1 . The carriage  70  has mounted on each end a hook structure  70 A,  70 B. As the carriage is moved in the rearward direction to an actuating position, the hook  70 A 1  on the carriage contacts the ramp surface  100 D 1  on the hook  100 D of pushrod  100  and rides over the hook  100 D. 
     To permit the carriage-mounted hooks to ride over the rod-mounted hooks, the hook structures  70 A,  70 B can be made of a flexible material which has sufficient resilience to permit the upward movement needed, or can include a flexible link portion. Alternatively, the carriage  70  could be mounted to the slider rods on bushings which are open at the bottom side adjacent the pushrod hooks, and which allow the carriage to move upwardly so that the carriage hooks  70 A,  70 B ride over the tops of the pushrod hooks. 
     Now the carriage  70  is driven in the forward direction  120 B, bringing the hook  70 A 1  into engagement with the hook  100 D on the pushrod. As the carriage  70  is driven forward, the pushrod  100  is pulled forward. Due to the angle of the channel  90  relative to the rod and the hinge action by which the pushrod is coupled to the slider structure, the pushrod exerts a force component transverse to the rod  52 , pulling the slider structure toward the rod  52  as the carriage  70  is moved forward. This causes the plunger  110  to engage the ramp surface  90 B on the slider structure, compressing the spring  112 . As the slider structure moves from one home position toward the other home position, the plunger rides on the flat surface  90 C. As the slider structure  90  reaches its detent position for the high resolution lens, the plunger travels down the ramp  90 A, releasing the stored energy. This release of energy causes the slider structure to move quickly to its home position, even if the carriage  70  stops moving. The pushrod  100  travels more quickly than the carriage  70 , and its distal end travels to the lower position shown in FIG. 12, out of engagement with the hook  70 A 1  on the carriage  70 . Now as the carriage  70  moves further in the direction  120 B, the hook  70 A 1  will pass over the hook  100 D without touching it. 
     To ensure disengagement of the carriage hook  70 A 1  from hook  100 D, the carriage movement can optionally be slowed as the distal end of the pushrod reaches its lower position, or the carriage can be stopped and moved in the reverse direction. Another alternative is to provide feedback on the motor drive and carriage movement to detect as an error condition any failure of a carriage hook to disengage from a pushrod hook. 
     As the pushrod  100  is being pulled by the carriage, moving the slider structure laterally, the pushrod  102  is being pulled by the slider structure. The distal end of the pushrod  102  travels along the lower channel portion of its guide slot, up the ramp portion to the elevated channel surface. Now the hook  102 D is in position to engage the hook structure  70 B the next time the carriage is moved backwards to actuate the slider structure. It can thus be seen that the slider structure will be toggled from one home position to the other by the linkage provided by the pushrods and the carriage hooks. Moreover, this toggling occurs without the need for a separate motor drive system to move the slider structure. 
     FIG. 16 is a simplified control block diagram for the scanning system  500 . Here the target page  40  to be scanned is positioned on the glass platen  204  at the scan region. The system includes an electronic controller  200  such as a microprocessor or ASIC, which controls the drive motor  212  and the illumination light source  62 , and receives the scanner optical sensor signals from optical sensor  80 . A host computer  202  is connected to the controller, and can optionally receive the representation of the scanned target for its use. The scanner system  50  may be part of a system such as a copy system. 
     This invention allows two different lenses to be used in a simple scanner system. Selection from one lens to the other is accomplished by the motion of the reflector carriage. This allows a multiple magnification system without having to add an additional motor to switch the lenses. 
     The described embodiment of the invention is implemented so that pulling the pushrod forward switches the lens slider. This implementation has the advantage of allowing much of the reflector carriage travel used for switching to also be used for normal scanning. The lenses do not move until the mirror carriage hooks the pushrod and starts forward. At the end of actuation the forward pushrod drops down in the guide track so that the scanner is now free to move back and forth over this pushrod without actuating the lens system. The only travel that can not be used for scanning is that required to hook over the pushrod. This would probably be about ¼ inch in an exemplary implementation. 
     The invention can be implemented in other ways. For example, an alternate embodiment of the system switches the lens by pushing with the carriage so that actuation occurs as the reflector carriage  70  moves towards the lens  84 ,  86 . To do this the guide tracks in which the distal ends of the pushrods run are rearranged so that the pushrod nearest the lens is up and the other down. The ramp profiles on the mirror and pushrods are reversed from that illustrated in FIG. 4 so that the hook on the reflector carriage engages the pushrod hook as it moves towards the lens. As the mirror carriage moves backwards, i.e. toward the lens slider structure (direction arrow  120 A) it pushes the pushrod backwards. The other pushrod passes under the reflector carriage and follows the channel upward at the end of its travel so that it is ready to engage the carriage hook on the next switch. The pushrod hook and carriage hook contact surfaces are ramped so that as the carriage moves away from the lenses the carriage hook will ride over the now elevated pushrod hook. The carriage rides on its slider rod in such a way that it is free to move up. Without these features the carriage would hit the forward pushrod on its return from actuation and stall. The distance that the reflector carriage would need to push the pushrod in order to achieve this actuation is about 1 inch in an exemplary implementation. It could be shorter if enough power from the motor that moves the carriage is available. This alternate implementation requires the travel of the carriage system to be lengthened by the actuation distance as the distance used for actuation can not also be used for scanning. 
     It is understood that the above-described embodiments are merely illustrative of the possible specific embodiments which may represent principles of the present invention. Other arrangements may readily be devised in accordance with these principles by those skilled in the art without departing from the scope and spirit of the invention.