Patent Publication Number: US-6334573-B1

Title: Integrated scanner on a common substrate having an omnidirectional mirror

Description:
RELATIONSHIP TO OTHER APPLICATIONS 
     This application is a continuation-in-part of Ser. No. 08/506,574, filed Jul. 25, 1995, now U.S. Patent No. 6,102,294 which is a continuation of Ser. No. 08/141,342, filed Oct. 25, 1993, now abandoned, which is a continuation-in-part of Ser. No. 08/111,532, filed Aug. 25, 1993, now U.S. Pat. No. 5,623,483 which is a continuation-in-part of Ser. No. 07/745,776, filed Aug. 16, 1991, now abandoned, which is a continuation of Ser. No. 07/530,879, filed May 29, 1990, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to scanners, and specifically, to integrated barcode scanners. 
     Barcodes store information about an associated object and can be read by scanners. As barcode scanners have become smaller, the number of uses have increased. Today, barcode scanners are used to price store items, control warehouse inventory, and even route overnight packages. 
     In reading a barcode, a barcode scanner scans a laser beam across the barcode and detects the reflected light from the barcode. Typically, barcode scanners, including handheld scanners, have been constructed using discrete components. These discrete components, such as laser diodes and rotatable scanning mirrors, are separately manufactured and carefully aligned in the scanner to obtain the proper scanning function. 
     However, the use of discrete components limits further miniaturization of the barcode scanner, thus restricting additional uses for the barcode scanner. Further, improper alignment of the discrete components can render the scanner inoperative. Thus, the discrete components must be carefully aligned during assembly, making the scanner complex and costly to construct. 
     Accordingly, it is desirable to provide an improved barcode scanner with increased flexibility. 
     It is also desirable to provide a miniaturized barcode scanner. 
     It is also desirable to provide a barcode scanner that is simpler to construct. 
     It is also desirable to decrease the cost of constructing a barcode scanner. 
     Additional desires fulfilled by the invention will be set forth in the description which follow, and in part will be apparent from the description, or may be learned by practice of the invention. The advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the amended claims. 
     SUMMARY OF THE INVENTION 
     To achieve the foregoing desires, a scan module on a common substrate provides an omnidirectional scan pattern. More particularly, a scan module formed on a common substrate consistent with the present invention comprises a mirror for scanning light across a target, a support for coupling the mirror to the substrate, and a means for moving the mirror to provide an omnidirectional scan pattern across the target. The moving means may include a combination of a magnet and a coil or a mirror electrode and a substrate electrode. Alternatively, the moving means may include orthogonal hinges, coupled between the mirror and the substrate, made of shape memory alloys. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the objects, advantages, and principles of the invention. 
     In the drawings, 
     FIG. 1 is a side view of a scanner consistent with the present invention; 
     FIG. 2 is a plan view of the scanner in FIG. 1; 
     FIG. 3 is a side view of a scan module used in the scanner shown in FIG. 1; 
     FIG. 4 is a side view of another scanner consistent with the present invention; 
     FIG. 5 is a side view of yet another scanner consistent with the present invention; 
     FIG. 6 is a plan view of the scanner in FIG. 5; 
     FIGS. 7A and 7B show a side view of still other scanners consistent with the present invention; 
     FIG. 8 is a perspective view of another scan module consistent with the present invention; 
     FIG. 9 is a side view of yet another scan module consistent with the present invention; 
     FIG. 10 is a top view of still another scan module consistent with the present invention; 
     FIG. 11 is a top view of another scan module consistent with the present invention; and 
     FIG. 12 is a top view of a scanner incorporating a scan module consistent with the present invention. 
    
    
     DETAILED DESCRIPTION 
     Reference will now be made to methods and apparatus -*consistent with this invention, examples of which are shown in the accompanying drawings. In the drawings, the same reference numbers represent the same or similar elements in the different drawings whenever possible. 
     Light scanning systems consistent with the present invention are formed on a common substrate to provide omnidirectional scan patterns. The light scanning system may include a light source for producing a light beam, a deflector for deflecting the focused light beam in a desired pattern, a lens, a detector for monitoring the light beam from the light source, a sensor for detecting a reflection of the deflected light beam, and electronic circuits. 
     FIG. 1 shows a scanner  100  including a laser diode  112 , spherical lens  114 , scan module  118 , and detectors  120  and  128 . Laser diode  112  and detector  128  are mounted on a laser submount  126 , which serves as a supporting stand. Spherical microlens  114  is supported by lens holder  116 . Laser submount  126 , lens holder  116 , scan module  118 , and detector  120  are mounted on a substrate  122 . 
     The surface of substrate  122 , which is preferably made of a semiconductor material such as silicon, includes a flat portion  121  adjacent to a sloped portion  123 . 
     Preferably, the sloped portion  123  is inclined at about a 45° angle. Laser submount  126  and lens holder  116  are mounted on flat portion  121 , and scan module  118  is mounted on sloped portion  123 . 
     Laser diode  112  is aligned with an optical axis of lens  114  and emits a visible laser beam according to a laser diode driver, not shown in the drawings. In a preferred embodiment, laser diode  112  can be any commercially available laser diode capable of producing a laser beam suitable for bar code scanning, such as the laser diode chip from a Sony SLD  1101  VS. 
     Detector  128  is mounted on laser submount  126  behind laser diode  112  for monitoring the output of laser diode  112 . Detector  128  creates a signal representing the amount of light from the back of laser diode  112 , which is proportional to the intensity of the laser beam from the front of laser diode  112 . That signal can be transmitted to a laser diode driver to control the output of laser diode  112 . 
     FIG. 1 shows lens  114  secured in an upright position by a separate lens holder  116 . Lens  114  and lens holder  116  could also be a single integrated device. Although FIG. 1 shows lens holder  116  mounted on the flat portion of substrate  122 , it could also be attached to laser submount  126 . Also, although lens  114  is shown as a spherical microlens in the preferred embodiment, lens  114  could also be any other lens for focusing a laser beam, such as a ball microlens, a grated rod index lens (GRIN), a micro-FRESNEL lens, or a cylindrical microlens. 
     The desired focus of the laser beam can be achieved by adjusting the distance between lens  114  and laser diode  112 . Lens holder  116  may be adjustable to move lens  114  with respect to laser diode  112 , but lens  114  is preferably fixed in a prealigned position. 
     Scan module  118  intercepts and deflects a laser beam from laser diode  112 . During operation of scanner  100 , scan module  118  scans the laser beam in one dimension across a target. Scan module  118  preferably comprises a micro-machined mirror, which is fabricated using existing VLSI technology. K. E. Peterson, “Silicon as a Mechanical Material,” Proc. of IEEE, Vol. 70, No. 5, 420-457 (May 1982), U. Breng et al., “Electrostatic Micromechanic Actuators,” 2 J. Micromech. Microeng. 256-261 (1992), and Larry J. Hornbeck, “Deformable-Mirror Spatial Light Modulators,” 1150 Proceedings of SPIE (1989) describe acceptable techniques for fabricating micro-machined mirrors. 
     Detector  120 , which is preferably mounted on the flat portion  121  of substrate  122 , detects a reflection of a laser beam as the beam is scanned across a target. The laser beam scatters as it is scanned across the target, thus allowing detector  120  to receive and detect light reflected from the target. Detector  120  then creates a signal representing the detected reflection. For example, where a laser beam has been scanned across a barcode having light and dark regions, the light regions of a barcode will reflect light, but the dark regions will not. As the laser beam is scanned across the barcode, detector  120  detects the dispersed light, which represents the light regions of the barcode, and creates a corresponding signal, thus permitting the barcode to be “read.” In a preferred embodiment, detector  120  is a monolithically integrated photodetector. 
     FIG. 2 shows a top view of scanner  100 . Laser diode  112 , lens  114 , and scan module  118  are arranged in alignment with each other to permit scan module  118  to deflect a focused laser beam. Detector  120  can be located on either side of lens holder  116 . 
     Wire bond pads  130  permit detector  120  to interface with an external device, for example, a signal processor. Wire bond pads  132  and  134  permit laser diode  112  and detector  128 , respectively, to interface with an external device, such as a laser diode driver, for controlling the output of laser diode  112 . Wire bond pads  142  allow micro-machined mirror to be actuated by an external device such as a feedback circuit (not shown). 
     Scan module  118  may be implemented using various structures, such as the torsional or cantilever structures described in more detail below. Further, scan module  118  can be actuated by various techniques also described in detail below such as electrostatic actuation and heat actuation. For heat actuation, hinges would be made of shape memory alloy or be bimetallic. 
     If it has a torsional structure, scan module  118  includes scanning mirror  136 , torsional hinges  138 , and frame  140 . Hinges  138  are supported by frame  140 , which is mounted on the sloped portion  123  of substrate  122 . Scanning mirror  136  is suspended by hinges  138  and rotates about an axis formed by hinges  138  along the surface of the sloped portion of substrate  122 . Scanning mirror  136  can be rotated up to 90°. As described above, wire bond pads  142  permit scan module  118  to interface with an external device, such as a scan module driver for controlling scan module  118 . 
     FIG. 3 shows various elements for controlling scan module  118 . Electrostatic actuation is one way that scan module  118  can rotate mirror  136  to scan an incident laser beam. Preferably, scan module  118  includes upper electrodes  144  mounted on a glass cover  148  on either side of the rotation axis above mirror  136 , and substrate electrodes  146  mounted on substrate  122  on either side of the rotation axis below mirror  136 . Upper electrodes  144  should be transparent to allow light to enter and exit scan module  118 . For example, upper electrodes  144  can be formed by depositing on glass cover  148  a semi-transparent metallic coating having a low reflectivity. 
     During operation of scan module  118 , upper electrodes  144  and substrate electrodes  146  are energized to create an electrostatic force to rotate mirror  136 . The electrostatic force creates a voltage between one of the substrate electrodes  146  arid mirror  136 , which in turn creates charges of opposite polarity between substrate electrode  146  and mirror  136 . The resulting attractive force pulls the closer side of mirror  136  downward, thus rotating mirror  136  along the rotation axis. 
     At the same time, a voltage is applied between mirror  136  and a corresponding upper electrode  144  to aid the substrate electrode  146  in rotating mirror  136 . The resulting attractive force pulls the other side of mirror  136  upward, continuing to rotate mirror  136  in coordination with the substrate electrode  146 . 
     Mirror  136  can be rotated in the opposite direction by applying voltages to the other substrate electrode  146  and upper electrode  144 . An incident light beam can be scanned by scan module  118  by alternately applying voltages to the appropriate substrate electrodes  146  and upper electrodes  144 . This approach provides a simple method of actuating scan module  118  using very low power consumption. 
     Although FIG. 3 shows both upper electrodes  144  and substrate electrodes  146 , mirror  136  could also be rotated using only one set of electrodes, i.e. either upper electrodes  144  or substrate electrodes  146 . In such a configuration, substrate electrodes  146  could rotate mirror  136  without using upper electrodes  144  by alternately applying voltages between the substrate electrodes  146  and mirror  136 . Upper electrodes  144  could work alone in the same manner. Either situation would require a greater attractive force to rotate mirror  136 . 
     Hinges  138  can be made of any suitable material, but are preferably made of a shape memory alloy, such as titanium nickel, because of the unique shape-restoring features of such alloys. Shape memory alloys return to their original shape when heated above a transition temperature. After hinges  138  are twisted by the rotation of mirror  136 , they can be subjected to a short electric pulse prior to each scan to heat them and return mirror  136  to its original position. A 10-20 mW pulse can be applied for 10 milliseconds or less to restore mirror  136  to its original position. 
     FIG. 4 shows a different embodiment of a scanning system. Scanner  102  includes laser diode  112  mounted on laser submount  126  in alignment with an optical axis of lens  144  for emitting a laser beam, and detector  128  mounted on laser submount  126  for monitoring the output of laser diode  112 . Lens  144 , supported by lens holder  116 , focuses the laser beam emitted from laser diode  112 . Laser submount  126  and lens holder  116  are mounted on a flat portion  121  of substrate  122 . Scan module  118 , mounted on a sloped portion  123  of substrate  122 , deflects the focused light beam across a target, and detector  120  detects a reflection of the scanned laser beam. 
     In addition, scanner  102  further includes lens  146 , supported by lens holder  142 , for magnifying the deflection of the beam from scan module  118  before the beam is scanned across a target. A wider deflection of the beam allows a smaller mechanical deflection angle of a micromirror in module  118  and increases the flexibility in focusing the beam. As shown in FIG. 4, lens  144  is a positive lens and lens  146  is a negative lens, although lenses  144  and  146  can be of any suitable type. 
     FIG. 5 shows another embodiment of the invention as scanner  104  comprising laser diode  112  mounted on laser submount  126 , which is in turn mounted on flat portion  121  of substrate  122 . Detector  128  is also mounted on laser submount  126  behind laser diode  112  for monitoring the output of laser diode  112 . Scan module  118 , mounted on the sloped portion  123  of substrate  122 , receives an unfocused laser beam from laser diode  112  and deflects that beam through lens  148 , which is supported by lens holder  150 . Lens  148  focuses the deflected beam before it reaches a target, such as a barcode. The configuration of scanner  104  provides a simple and compact structure due to the absence of a lens between laser diode  112  and scan module  118 . 
     FIG. 6 shows a top view of scanner  104  without lens  148 . Laser diode  112  is aligned with scan module  118 . Wire bond pads  132  and  134  allow external devices to interface with laser diode  112  and detector  128 , respectively. Wire bond pads  142  allow external devices to interface with the micro-machined mirror. Although FIG. 6 shows no detector for detecting the reflected light, such a detector may easily be mounted near scan module  118  or at some other desirable location. 
     Another scanning system, shown in FIGS. 7A and 7B, bends the light beam onto a scan module. Scanners  106  and  107  (FIGS. 7A and 7B, respectively) comprise laser diode  112 , lens  114 , scan module  118 . Lens  114  used in scanners  106  and  107  can be of any type and is mounted on substrate  222 , which is completely flat. Laser diode  112  is mounted on laser submount  126 . 
     As shown in FIG. 7A, laser diode  112  of scanner  106  is aligned above an optical axis of lens  114  by an amount ×. By aligning laser diode  112  in this way, the laser beam emitted from laser diode  112  is bent downward an angle θ. The bent laser beam strikes scan module  118 , which is mounted on flat substrate  222 . Scan module  118  scans the laser beam across a target in the manner described in the other embodiments. 
     As shown in FIG. 7B, scanner  107  also includes a prism  115  positioned adjacent to lens  114 . A laser beam emitted from laser diode  112  passes through lens  114  and is bent downward by prism  115  onto scan module  118 . Again, scan module  118  scans the laser beam across a target in the manner described in the other embodiments. 
     Bending the laser beam emitted from laser diode  112  eliminates the need for a sloped substrate. This provides a distinct advantage because a flat substrate is easier to manufacture than a sloped substrate. 
     Scan modules  118  and  119  can also include miniature scan elements capable of producing a number of omnidirectional scan patterns. These elements can be built using a combination of micromachining, die, and wire bonding techniques or other available methods. 
     FIG. 8 shows a scan module  250  for producing omnidirectional scan patterns consistent with the present invention. Scan module  250  includes a small mirror  136  connected to substrate  222  by an elastic support  252 , such as a polyimide. Four magnets  254  are placed on individual sides of the back of mirror  136  as shown in FIG.  8 . In addition, four coils  256  are incorporated into substrate  222 , for example by etching, directly under magnets  254 . 
     Applying current through coils  256  attracts and repels magnets  254  to substrate  222 . The combination of attraction or repulsion by magnets  254  provides mirror  136  with omnidirectional motion for generating omnidirectional scan patterns. For conventional, i.e., not micro-machining, technology, a ball-joint type of support can be used in place of elastic support  252 . 
     FIG. 9 shows another scan module  350  consistent with the present invention similar to the one described above in accordance with FIG.  8 . Scan module  350  in FIG. 9 uses one or more mirror electrodes  353  placed on the back of a mirror  136  instead of magnets. Scan module  350  of FIG. 14 further includes a support  352  for connecting mirror  136  to a substrate  322 , a wire  351  for applying an electric potential to mirror electrode  353 , and a set of four substrate electrodes  355  (only three shown) incorporated into substrate  322 . 
     To provide omnidirectional scan patterns, an electric potential is applied between substrate electrodes  355  and mirror electrode  353  to move mirror  136 . The electric potentials between each substrate electrode  355  and mirror electrode  353  generate electrostatic forces that cause mirror  136  to move in different directions, thereby providing an omnidirectional scan pattern. 
     FIG. 10 shows another scan module  450  consistent with the present invention. In scan module  450  of FIG. 10, a mirror  136  is suspended on four orthogonal hinges  462 . The hinges are made of, for example, shape memory alloys (SMA). Also shown are alternate hinges  464 , also made of SMA, which suspend mirror  136  from different points. In addition, a support  452  can be installed under mirror  136 . Support  452  provides a pivoting point for mirror  136  and can serve as a motion limiter if there is a sudden acceleration, such as being dropped. 
     Hinges  462  provide the omnidirectional scan capability to mirror  136 . When heated by applying current, hinges  462  change their dimension and move mirror  136  to create an omnidirectional scan pattern. 
     FIG. 11 shows a scan module  500  that includes a combination of elements used in scan modules  250 ,  350 , and  450  (FIGS. 8,  9 , and  10 , respectively). In contrast to those scan modules, however, scan module  500  only has two active elements. As shown in FIG. 11, scan module  500  includes a mirror  136  and a support  552  for supporting mirror  136  and connecting it to a substrate  522 . Scan module  500  further includes, two SMA hinges  502  and an optional pivot hinge  504 . Pivot hinge  504  connects to the corner of mirror  136  and can be used as a suspension or as a conductor to provide electric potential to one or more mirror electrodes (not shown). 
     Scan module  500  can provide omnidirectional scan patterns using the operation of any of the above scan modules  250 . For example, SMA hinges  502  could be replaced by a combination of coils and magnets as described in scan module  250  of FIG.  8 . By applying current through the coils, the magnets are either attracted to or repelled from the substrate. The combination of attraction or repulsion by the magnets with support from pivot hinge  504  provides mirror  136  with omnidirectional motion for generating omnidirectional scan patterns. 
     Alternatively, SMA hinges  502  could be replaced by two substrate electrodes. In this design, pivot hinge  504  is used as a conductor to provide electric potential to mirror electrodes (not shown). To provide omnidirectional scan patterns, mirror  136  is moved by applying electric potential between the substrate electrodes and mirror electrode. Electrostatic forces, based on the electric potentials between each substrate electode and the mirror electrodes, cause mirror  136  to move in different directions. 
     With SMA hinges  502  as shown in FIG. 11, pivot hinge  504  connects to mirror  136  to keep mirror  136  suspended. In operation, SMA hinges  502  are heated by applying current. Because hinges  502  are made of SMA, the heat causes hinges  502  to change their dimension, thereby providing motion to mirror  136  for creating the omnidirectional scan patterns. Each design of scan module  500  only requires two active elements, either two SMA hinges, two combinations of a coil and a magnet, or two substrate electrodes. 
     FIG. 12 shows a scanner  700  integrated on a substrate  702 . Scanner  700  includes a light source  704 , such as a laser diode, a detector  706  for detecting light reflected from a target, and a scan module  708  for scanning light from light source  704  across the target. Scan module  708  may be any of the scan modules discussed above including scan modules  118 ,  119 ,  250 ,  350 ,  450 , and  500 . Scanner system  700  may be, for example, a stationary barcode scanner or a handheld barcode scanner. 
     The scanners of the present invention can be manufactured using either monolithic integration or hybrid integration. Monolithic integration fabricates the opto-mechanical system entirely on a single semiconductor chip. On the other hand, a hybrid integrated circuit combines one or more individually fabricated subsystems on a common substrate. Hybrid integration generally involves less complicated processes than monolithic integration and permits the combination of more accurate devices. 
     Many of the components of the present invention including the laser diode, detectors, lenses, and scan module could be fabricated using VLSI technology. If monolithic integration is used, all of these components are fabricated onto a single chip in a single series of process steps. If hybrid integration is used, each component is individually fabricated and mounted onto a common substrate. 
     All of the components need not be VLSI, however. For example, the lens for focusing the light beam could be constructed using other known techniques and then appropriately mounted onto the scanner. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the scanner consistent with the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.