Patent Publication Number: US-2012037703-A1

Title: Optical device, optical information reading device and light source unit mounting method

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an optical device equipped with an illuminator or irradiator for illuminating an object with light, an optical information reading device for reading information represented by in a sequence of code symbols in a module whose optical reflectivity differs from its surroundings, and a light source unit mounting method for mounting the light source unit in the optical device. 
     Code symbols such as barcodes and two-dimensional codes are images constituted of modules of black bars (or simply bars) and white bars (or spaces). As is well known, product information is expressed in these code symbols. These code symbols are printed on or affixed to products, and the code symbols are read by an optical information reading device. Use of these code symbols is typified by point-of-sale (POS) systems used in supermarkets and retail outlets. However, they are also used in distribution, postage, event management, medicine and chemical analysis. 
     Optical information reading devices can be divided, broadly speaking, into laser code scanners using lasers and area sensor scanners using a camera with a charge-coupled device (CCD) or complementary metal oxide semiconductor (CMOS). Compared to area sensor scanners, laser code scanners have a longer history, greater accumulation of technologies and better reliability. 
     Laser code scanners include compact optical scanning modules in which the object to be read is scanned with a light beam (laser beam) using a semiconductor laser element as the light source, and information is decoded from the reflected light. As is well known, these optical scanning modules can use the laser beam deflecting method, the multiple-surface mirror (polygon mirror) rotating method or the vibrating mirror method in the scanning process. 
     For example, Publication of Unexamined Japanese Patent Application No. 2009-259058 (JP 2009-259058 A) describes a barcode reading device in which light is emitted from a light-emitting element such as a semiconductor laser, and reflected towards the object to be read using a surface of a polygon mirror. Japanese Patent Gazette No. 4,331,597 (JP 4,331,597 B2) describes an optical information reading device in which a laser beam emitted from a light-emitting unit is reflected towards the object to be read by a vibrating mirror which is vibrated using the seesaw method. In order to direct multiple light beams at the object to be read, the former device uses a polygon mirror with multiple reflective surfaces and the latter device uses a single-surface mirror that is vibrated. 
     Multiple light beams reaching the object to be read have an effect on precision when the code symbols are decoded, so multiple beams reaching the object to be read enable better decoding. 
     While this leads to better decoding precision, it is difficult to make smaller and thinner optical scanning modules for optical information reading devices that scan with a laser beam and detect reflected light. In recent years, optical scanning modules have been built into information reading devices such as handheld scanners. Optical scanning modules are also being built into multi-function electronic devices such as handheld information terminals and smart phones. 
     An optical scanning module using the technology disclosed in JP 4,331,597 B2 was the world&#39;s smallest known optical scanning module at the time of the disclosure. However, an even more compact module is desired. The problem with making a more compact module resides in the optical performance of the module. In other words, unless a compact module is devised with a configuration that has sufficient light beam intensity, the intensity of the light beam scanning the object to be read will be weak and the decoding precision will be poor. 
     In light of this situation, the purpose of the present invention is to downsize an optical device for scanning an object to be read with a light beam and detecting the reflected light, and a compact optical information reading device using a module with these functions. 
     In order to achieve this purpose, one embodiment in accordance with the present invention is an optical device equipped with an irradiator for irradiating an object with light, wherein the irradiator is equipped with a light source unit with a laser light source unit for outputting a laser beam and a collimating lens allowing the laser beam from the laser light source unit to pass through. The light source unit is equipped with a pedestal for arranging the laser light source unit so that the laser beam is outputted in the direction along the optical path passing through the optical axis of the collimating lens, and wherein the light source unit is secured by a first securing means to the pedestal so as to move only in the direction along the optical axis. A second securing means different from the first securing means secures the light source unit to the pedestal so as not to move in the direction along the optical axis. In this optical device, the pedestal can have a groove in the direction along the optical path, at least a portion of the optical unit can be inserted into the groove in the pedestal, and movement in directions other than the direction of the groove can be restricted. 
     In this optical device, a pair of protrusions can be formed on the light source unit and the pedestal, the protrusions can have a substantially constant width in the direction along the optical axis in the positions where the protrusions on the light source unit side and the protrusions on the pedestal side come into planar contact with each other when the light source unit is arranged on the pedestal. The first securing means can be elastic clips securing the protrusions on the light source unit side and the protrusions on the pedestal side while in contact with each other. Also, an exterior of the optical device can be equipped with a gap for inserting in the direction perpendicular to the optical path the clips securing the protrusions on the light source unit side and the protrusions on the pedestal side. 
     In this optical device, the irradiator can be a means for irradiating an object with a laser beam outputted from a laser light source unit via a collimating lens and an aperture with a slit-shaped opening. The collimating lens can be arranged in front of the aperture along the optical axis of the laser beam and have the same shape as the opening in the aperture, and the laser beam passing through the collimating lens can have a size greater than the opening so as to reach the aperture. Also, the collimating lens arranged in front of the aperture can have the power of a cylindrical lens on one side and the power of a collimating lens on the other side, and the lens can form an oval-shaped beam spot with the laser beam outputted from the laser light source unit. 
     In this optical device, the irradiator and a vibrating mirror for deflecting the laser beam outputted from the laser light source unit in the irradiator and scanning an object can be installed exteriorly, an opening can be formed in one side of the exterior, and the rotational axis of the vibrating mirror and the bearing for securing the vibrating mirror rotatably to the rotational axis can be arranged so as to pass through the opening. Also, a cover can be installed on one surface of the exterior to cover the rotational axis and bearing passing through the opening. In addition, the one side of the exterior can be a circuit board, and the circuit board can be secured by a securing tool to a case constituting the other side of the exterior. Another embodiment of the present invention is an optical information reading device equipped with any one of the optical devices described above for reading information represented by in a sequence of code symbols in a module whose optical reflectivity differs from its surroundings. 
     A further embodiment of the present invention is a light source unit mounting method for mounting a light source unit equipped with a laser light source for outputting a laser beam as the light source in an irradiator to the case of an optical device when an optical device equipped with an irradiator for irradiating an object with light is manufactured. The light source unit mounting method comprises in successive order a first step for preparing the case of the optical device equipped with a collimating lens and a pedestal for arranging the laser light source in the light source unit so that the laser beam is outputted substantially parallel to the optical path passing through the optical axis of the collimating lens, a second step for securing the light source unit to the pedestal using a first securing means so as to move only in the direction along the optical path, a third step for moving the light source unit in the direction along the optical axis and adjusting the position so that the laser beam outputted from the laser light source is converted to parallel light by the collimating lens, and a fourth step for securing the light source unit to the pedestal using a second securing means different from the first securing means so as not to move in the direction along the optical axis. In this light source unit mounting method, the pedestal can have a groove in the direction along the optical path, and the second step can include a step in which at least a portion of the light source unit is inserted into the groove in the pedestal. Also, a pair of protrusions can be formed on the light source unit and the pedestal, the protrusions can have a substantially constant width in the direction along the optical axis in the positions where the protrusions on the light source unit side and the protrusions on the pedestal side come into planar contact with each other when the light source unit is arranged on the pedestal, and elastic clips can secure the protrusions on the light source unit side and the protrusions on the pedestal side while in contact with each other in the second step. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing brief description and further objects, features and advantages of the present invention will be understood more completely from the following detailed description of presently preferred, but nonetheless illustrative, embodiments in accordance with the present invention, with reference being had to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of the optical scanning module in an embodiment of the optical device of the present invention; 
         FIG. 2  is a front view looking in the direction of arrow A in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view along line  3 - 3  in  FIG. 2  and looking in the direction of the arrows; 
         FIG. 4  is a perspective view of the light detector in the optical scanning module shown in  FIG. 1 ; 
         FIG. 5  is a schematic diagram showing the arrangement of the light detector in the optical scanning module; 
         FIG. 6  is a diagram showing the arrangement of a known surface-mounted light detector; 
         FIG. 7  is a perspective view of the laser light source unit in the optical scanning module shown in  FIG. 1 ; 
         FIGS. 8A-8D  are a sequence of diagrams used to explain the process for mounting the laser light source unit in the module package using clips; 
         FIG. 9  is a top view of the laser light source unit mounted on the pedestal; 
         FIGS. 10A and 10B  are a sequence of diagrams used to explain the process for mounting the circuit board to the module package with the laser light source unit; 
         FIG. 11  is a schematic diagram showing the cross-section of the portion of the optical scanning module in  FIG. 1  extending from the coil to the support shaft and vibrating mirror holder; 
         FIG. 12  is a cross-section of the comparative example corresponding to  FIG. 11 ; 
         FIG. 13A and 13B  are diagrams used to explain the power of the lens in the optical scanning module shown in  FIG. 1 ; 
         FIG. 14  is a diagram showing the shape of the spot formed by a laser beam passing through this lens; 
         FIG. 15  is a diagram showing the shape of this lens; 
         FIGS. 16A and 16B  are diagrams used to explain the power of the lens in the comparative example corresponding to  FIG. 13A and 13B , respectively; 
         FIG. 17  is a diagram used to explain the manufacturing method for a lens with the shape shown in  FIG. 15 ; and 
         FIG. 18  is a block diagram showing the configuration of the code scanner in an embodiment of the optical information reading device of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Embodiment of the Optical Device: FIG.  1  Through FIG.  16 B. 
     First, the optical scanning module in an embodiment of an optical device equipped with a light detector of the present invention will be explained.  FIG. 1  is a perspective view of the optical scanning module,  FIG. 2  is a front view looking in the direction of arrow A in  FIG. 1 , and  FIG. 3  is a cross-sectional view along line  3 - 3  and looking in the direction of arrows in  FIG. 2 , in which the cross-hatching for portions other than the module case  2  is omitted. 
     In this optical scanning module  1 , the exterior, as shown in  FIG. 1  and  FIG. 2 , is constituted of a module case  2  and a circuit board  3  secured to each other by two screws  4 ,  4 . The module case  2  is molded from a zinc alloy such as ZDC2 using the die-casting method, and the overall external dimensions are 14 mm×20.4 mm×3.4mm (D×W×H). In place of the zinc alloy, aluminum, an aluminum alloy or a magnesium alloy can be used. This component is molded from metal in order to obtain sufficient precision and strength and in order to obtain the shielding effect for the LSI described below. The component can also be molded with a resin such as a reinforcing plastic when separately considering the shielding effect. 
     In the module case  2  are installed slits  5  for inserting the clips  15  used to secure the laser light source unit  10  to the module case  2  as described below, and an opening  6  for the scanning laser beam to exit and for the reflected light to be detected to enter. In  FIG. 3 , the portion of the module case  2  denoted by  2   a  appears as a separate component. This component is connected to the other component by the portion above line  3 - 3  in  FIG. 2 . 
     In the circuit board  3  are formed through-holes  7  for insertion of the terminals  13  on the laser light source unit  10 , and a through-hole for insertion of the support shaft  34  and bearing  33  for the vibrating mirror  31  described below. The latter through-hole is covered by the cover  38  in  FIG. 1  and so is not shown in the figure. Various components are installed on the insides of the module case  2  and the circuit board  3  as shown in  FIG. 3 . The following is an explanation with reference to  FIG. 3 . The major components shown in  FIG. 3  will be explained below in greater detail. Accordingly, these components will not be explained with reference to  FIG. 3 . 
     First, the module case  2  is equipped with the laser light source unit  10  serving as the light source in the irradiator for irradiating the object with a laser beam. The laser light source unit  10  is a thin package laser in which the semiconductor laser  11  serving as the laser light source for outputting the laser beam is installed near one end. A pair of flange-shaped protrusions  12 ,  12  is provided on the side to be pressed against the corresponding protrusions on the pedestal formed on the module case  2  by the clips  15 ,  15 . The protrusions on the end of the pedestal are not shown in  FIG. 3 . In the laser light source unit  10 , four terminals  13  are installed on the end opposite the semiconductor laser  11 . This is exposed to the outside of the optical scanning module  1  via a through-hole  7  installed in the circuit board  3 . Drive signals for driving the laser light source unit  10  can be inputted from the outside via terminals  13 . 
     In the module case  2  are also installed a mirror  21 , lens  22  and an aperture  23  serving as the optical elements constituting the light projecting optics for projecting the laser emitted from the semiconductor laser  11  installed in the laser light source unit  10  as a beam forming an oval-shaped beam spot. 
     The mirror  21  is a fixed mirror used to change the direction of the optical path of the laser beam. The lens  22  is a lens with the power of a collimating lens and the power of a cylindrical lens only in one of the X direction and Y direction perpendicular to each other. The radial laser beam outputted from the semiconductor laser  11  passes through this lens  22  and is converted into parallel light with a round spot by the power of the collimating lens and into a beam with an oval-shaped spot by the power of the cylindrical lens. The aperture  23  cuts off the ends of the beam passing through the lens  22  in order to narrow the beam to the desired diameter. 
     The laser beam passed through the aperture  23  is reflected by a vibrating mirror  31  swinging like a seesaw as indicated by arrow C, and directed out from the opening  6  along the optical path indicated by S. In this way, the object scanned by the laser beam can be scanned reciprocatingly. 
     The components in the module case  2  used to vibrate the metal, resin or glass vibrating mirror  31  include a vibrating mirror holder  32  made of resin with the vibrating mirror  31  attached to the front face, a support shaft  34 , and a coil  36 . The vibrating mirror holder  32  is supported rotatably on the support shaft  34  serving as the rotational axis by a resin bearing  33 , and a moving magnet (permanent magnet)  35  is secured to the end opposite the end to which the vibrating mirror  31  has been attached. A yoke  37  is passed through the coil  36  in the direction perpendicular to the winding direction. In the cross-section of  FIG. 3 , the coil  36  and the yoke  37  have been cut away near the center of the yoke  37 . 
     When the moving magnet  35  and the yoke  37  are in an inactive state (the coil  36  is not being electrified), they are generally parallel. In this state, the cross-sectional area of the yoke  37  in the direction perpendicular to the parallel direction is smaller than the cross-sectional area in the parallel direction. The terminals (not shown) of the coil  36  are connected to the circuit board  3 , and control signals are supplied from the circuit board  3 . 
     The yoke  37  is secured by pushing it into a pair of slits  8 ,  8  formed in the side wall and inner wall of the module case  2  via the insulating material doubling as the bobbin for the coil  36 . The arrangement of the yoke  37  and the arrangement of the coil  36  are adjusted with respect to the magnetic force and then secured in that position. 
     The moving magnet  35  in the vibrating mirror holder  32  is arranged so as to be separated slightly from the coil  36 . The support shaft  34  is covered by a bearing  33  serving as a sliding bearing, and is held loosely by a slider (not shown) whose upper and lower surfaces in the axial direction are fitted to the support shaft  34 . In this way, the vibrating mirror holder  32  is movingly supported in the axial direction and within a predetermined range by the support shaft  34 . 
     The slider is a resin washer that allows for non-contact and prevents interference so that the vibrating mirror holder  32  remains in a floating state. When different polarity voltage is applied alternatingly to the coil  36  in this state, the action of the electromagnetic induction between the coil  36  and the moving magnet  35  causes the vibrating mirror  31  to seesaw centered on the support shaft  34 . 
     In the module case  2 , reflected light from the scanned object enters via the opening  6 . The incoming light is reflected by the vibrating mirror  31  and directed towards the light-receiving lens  41  with condensing power. Because the light returns at the same angle with respect to the light-receiving lens  41  irrespective of the vibration phase of the vibrating mirror  31  (scanning at whatever angle), the vibration of the vibrating mirror  31  causes no problems. 
     A filter  42  selectively permeable to light with the wavelength of the laser beam outputted from the laser light source unit  10  is installed where the reflected light has passed through the light-receiving lens  41 , and the incident light is cut off in the range outside of the reflected light of the scanning beam. For example, if the wavelength of the laser beam is 650 nm (nanometers), the filter  42  is selectively permeable to a beam with a wavelength of 650 nm. If an infrared laser is used, an infrared (IR) filter is used that is selectively permeable to infrared light with this wavelength. 
     A light detector  43  equipped with a photodiode is mounted on the circuit board  3  near the focal point of the light-receiving lens  41  after the reflected light has passed through the filter  42 . The light-receiving lens  41  and the filter  42  are fixed to the module case  2 , but the light detector  43  is mounted on the circuit board  3  in  FIG. 1  and  FIG. 2 . 
     The light detector  43  outputs electric signals from electrodes installed on the surface opposite the light-receiving surface with the photodiode based on the light intensity registered by the photodiode. For example, when code symbols arranged in alternating black bars and white spaces are scanned by laser beam and the reflected light from the from the symbols is received by the light detector  43 , low-level electric signals are obtained as output from the light detector  43  on the timing of the reflected light received from the low-reflectivity black bars and high-level electric signals are obtained as output from the same detector on the timing of the reflected light received from the high-reflectivity white spaces. When the electric signals outputted from the light detector  43  are extracted and interpreted by the circuit board  3 , the bar arrangement can be estimated and the information signified by the code symbols can be read. 
     The following four sections of this document describe distinctive portions of the optical scanning module  1  explained above.
         (1) The Configuration of Light Detector  43  and the Mounting Configuration to Circuit Board  3 .   (2) The Process and Configuration for Mounting the Laser Light Source Unit  10  to the Module Package  2 .   (3) The Arrangement of the Bearing  33  and Support Shaft  34  for the Vibrating Mirror Holder  32 .   (4) The Performance and Configuration of the Lens  22 .       

     These sections will now be presented in successive order with reference to the figures. 
     (1) Configuration of Light Detector  43  and Mounting Configuration to Circuit Board  3 . ( FIG. 4  through  FIG. 6 ) 
     First, the configuration of the light detector  43  and the mounting configuration to the circuit board  3  will be explained.  FIG. 4  is a perspective view of the light detector  43 .  FIG. 5  is a schematic diagram showing the arrangement of the light detector  43  in the optical scanning module  1 . As shown in  FIG. 4 , the light detector  43  has a photodiode (PD)  55  shown in  FIG. 5  installed as the light-receiving element on the substrate  51 . This is covered by a transparent resin covering material  52  in order to protect the PD  55 . In other words, the PD  55  is installed on the surface of the substrate  51  covered with the coating material  52 . 
     A pair of flat, output electrodes  53 ,  53  are installed on the side of the substrate  51  opposite the side on which the PD  55  is installed in order to output electric signals corresponding to the intensity of the light received by the PD  55 . The PD  55  is connected to these output electrodes  53 ,  53  using a configuration common in the art, so depiction in the figures and further explanation have been omitted here. Notches  54  are formed in the surface of substrate  51  so as to be adjacent to but on a surface different from the surface on which the output electrodes  53  are formed. Notches  54  are also on a surface different from the surface on which PD  55  is installed, and they are positioned so as to come into contact with the output electrodes  53 . Electrodes connected to the output electrodes  53  are installed inside the notches  54 . 
     In  FIG. 4 , the electrodes installed inside the notches  54  are denoted with the same cross-hatching as the output electrodes  53 . However, it is not essential that the electrodes be installed inside the notches  54  in the same step as the output electrodes  53 , and it is not necessary to use the same material. Also, the electrodes do not have to be installed over the entire inside surface of the notches  54 . However, if there are multiple output electrodes  53 , the notches  54  and their internal electrodes are installed so that they connect to a corresponding one of the output electrodes  53  and so that different output electrodes  53  are not connected to each other. Preferably, the notches  54  are formed in the substrate  51  so that the surface with the PD  55  installed is not reached. This could have an adverse effect on covering the side with the covering material  52 . 
     When the light detector  43  is mounted on the circuit board  3 , the output electrodes  53  and the notches  54  are aligned with the pad electrodes  3   a  on the circuit board  3  serving as the connection electrodes to be connected to the output electrodes  53  as shown in  FIG. 4 . The output electrodes  53  are then connected to the pad electrodes  3   a  using solder  56 . By filling the notches  54  with solder  56  at this time, the output electrodes  53  and the pad electrodes  3   a  can be connected readily and reliably via the electrodes installed inside the notches  54 . 
     In the example shown in  FIG. 5 , the solder  56  covers not only the notches  54  but also the output electrodes  53 . This is intended to increase the connection area between the output electrodes  53  and the pad electrodes  3   a  and to increase the adhesive strength between the light detector  43  and the circuit board  3 . However, a connection can be established simply by filling the interior of the notches  54  with solder if there is a desire to reduce the amount of solder used. 
     The use of this light detector  43  and mounting configuration to the circuit board  3  allows a compact light detector to be readily mounted with the light- receiving surface perpendicular to the circuit board  3 . Thus, as shown in  FIG. 5 , incident light from the outside is reflected by the vibrating mirror  31  which is the first optical component for light directed towards the PD  55  in the light detector  43 . The reflected light can then be directed towards the light-receiving surface of the light detector  43  along an optical path parallel to the surface of the circuit board  3  with the pad electrodes  3   a  installed (via the light-receiving lens  41  and the filter  42  omitted from  FIG. 5 ). 
     A compact and inexpensive light detector  43  can be mass produced if the light detector has the output electrodes  53  on the back surface of the substrate  52 , multiple PDs  55  are installed on a substrate  51  and covered by a covering material  52 , and the individual light detectors  43  are cut away after the output electrodes  53  have been installed. The notches  54  can be created before the substrate is cut apart, and the inside can be plated with an electrode material. 
     A light detector with the output electrodes  53  installed on the back surface of the substrate  51  is well known in the art surface mounted device. However, this type of device presupposes the mounting of output electrodes on a circuit board opposite the connection electrodes on the circuit board.  FIG. 6  shows this arrangement in a surface mounted light detector  243  of the related art. In a light detector  243  of the related art, as shown in  FIG. 6 , the light-receiving portion has to be parallel to the surface of the circuit board  203  with the connection electrodes. When the optical path of the reflected light is parallel to this surface, a reflecting mirror  250  has to be installed to change the optical path so that the reflected light is directed towards the light-receiving portion. 
     As a result, the number of components is increased and the optical path has to be arranged so that it has a certain path length directed perpendicular to the circuit board  203 . It also makes it difficult to reduce the thickness of an optical scanning module including a module case  202  (the size perpendicular to the circuit board). Some light detectors are known to have the light-receiving portion arranged perpendicular to the circuit board, but the electrodes are formed by lead wires. This causes problems with the number of components and manufacturing steps, and makes it difficult to obtain a compact light detector compared to light detector  243 . 
     The structure in  FIG. 4  and  FIG. 5  makes it easy to reduce the size of the light detector  43  itself. The incident light can be directed at the light-receiving surface of the light detector  43  via an optical path that is parallel to the surface of the circuit board  3  with the pad electrodes  3   a  installed. As a result, a thinner optical scanning module  1  can be obtained. Thus, this configuration can be said to be extremely useful in the miniaturization of the optical scan module  1 . 
     In the example shown in  FIG. 4 , the light detector  43  can be mounted on the circuit board  3  without any concern regarding top and bottom, because notches  54  are installed in the two surfaces making contact with the output electrode. However, the notches  54  only have to be installed in one of these surfaces. In the example shown in  FIG. 4 , the light detector  43  is rectangular. However, the present invention is not limited to this. If the surface in which the notches  54  are formed and the surface on which the PD  55  is installed (the light-receiving surface) are almost vertical, the light-receiving surface and the surface of the circuit board in which the connection electrodes are installed can be arranged almost vertically when the light detector  43  is mounted on the circuit board  3 , and the effect described above can be obtained. 
     (2) Mounting of Laser Light Source Unit  10  to Module Package  2  ( FIG. 7  through  FIG. 10B ) 
     First, the process and structure for attaching the laser light source unit  10  to the module case  2  will be explained.  FIG. 7  is a perspective view of the laser light source unit  10 .  FIG. 8A  through  FIG. 8D  are diagrams used to explain the process for securing the laser light source unit  10  to the module case  2  using clips  15 .  FIG. 9  is a top view showing the laser light source unit  10  mounted on the pedestal  60 .  FIG. 10A  and  FIG. 10B  are diagrams used to explain the process of mounting the circuit board  3  to a module case  2  to which the laser light source unit  10  has been attached. In  FIG. 8A  through  FIG. 8D , the hatching indicating the cross-sectional surface of the laser light source unit  10  has been omitted. 
     As described in the explanation of  FIG. 3  and shown in  FIG. 7 , the laser light source unit  10  is equipped with a semiconductor laser  11  near one end, a pair of flange-shaped protrusions  12 ,  12  on the side surfaces, and four terminals  13  at the end opposite the semiconductor laser  11 . The terminals  13  are bent in the optical scanning module  1  so as to penetrate the circuit board  3  and protrude upward. This saves the necessary space to the rear in which the laser light source unit  10  is mounted. 
     The section lines have been omitted from the figures, but  FIG. 8A  through  FIG. 8D  show the steps to secure the laser light source unit  10  to the module case  2  using clips  15 ,  15 . This is viewed in cross-section from the bottom of  FIG. 3  at the position of the connecting line near the center of the two clips  15 ,  15  in  FIG. 3 . Therefore, in  FIG. 8A  through  FIG. 8D , the laser beam is outputted towards the front of the figure from the back of the figure, and this direction is the direction of the optical path of the beam deflected by the mirror  21  and passing though the optical axis of the lens  22 . 
     As shown in  FIG. 8A , a pedestal  60  is formed in the module case  2 , and the laser light source unit  10  is arranged on top. A groove  61  is formed in the center of the pedestal  60  and a pair of protrusions  62 ,  62  is formed on both ends. When the laser light source unit  10  is arranged on the pedestal  60 , the laser light source unit  10  is inserted into the module case  2  from above. As shown in  FIG. 8B , the portion  14  (positioned opposite the circuit board  3 ) below the protrusion  12  on the laser light source unit  10  is fitted into the groove  61  in the pedestal  60 . When the width of the groove at the position denoted by the number  14  is the substantially same width as groove  61 , the laser light source unit  10  can be moved only in the direction parallel to the groove  61  in the pedestal  60 . In other words, it can only be moved in the direction of the optical path of a beam passing through the optical axis of the lens  22 . 
     When the laser light source unit  10  is arranged on top of the pedestal  60 , the protrusions  12 ,  12  on the laser light source unit  10  and the protrusions  62 ,  62  on the pedestal  60  make contact with each other on a plane. In this state, the elastic clips  15 ,  15  serving as the first securing means are inserted from the left and right in  FIG. 8B  or from the direction perpendicular to the optical axis of a beam passing through the optical axis of the lens  22 . Jigs  70 ,  70  are used to apply pressure from below and the side as shown in  FIG. 8B  and  FIG. 8C  so that, as shown in  FIG. 8D , the protrusions  12 ,  12  on the laser light source unit  10  and the protrusions  62 ,  62  on the pedestal  60  are secured so as not to separate. During the securing step, there is no need to be concerted with the position of the laser light source unit  10  with respect to the direction of the optical path of a beam passing through the optical axis of the lens  22 . 
       FIG. 9  is a top view showing the mounted position of the laser light source unit  10  in this state. The clip  15  on the left side in  FIG. 8A  through  FIG. 8D  can be inserted through the slit  5  installed in the side surface of the module case  2  and the clip  15  on the right side of the figures can be inserted from the gap  9  installed in the bottom surface of the module case  2  (see  FIG. 3 ). 
     When the laser light source unit  10  has been secured to the pedestal  60  using the clips  15 , the laser light source unit  10  does not move either left and right or up and down in  FIG. 8D . However, there is no component to keep it from moving from the back of the figure towards the front or from the front of the figure towards the back. Therefore, by applying a force able to resist the frictional force of the clips  15 ,  15  on protrusions  12 ,  12  and  62 ,  62  the laser light source unit  10  can be moved on top of the pedestal  60  from the back of the figure towards the front or from the front of the figure towards the back. This allows the laser light source unit  10  to be moved in order to adjust the optical path from the semiconductor laser  11  to the lens  22 , arrange the semiconductor laser  11  near the focal point of the lens  22 , and obtain a beam spot from the lens  22  of the appropriate size. 
     If protrusions  12 ,  12  and protrusions  62 ,  62  have a constant width lengthwise in the direction of the optical path of a beam passing through the optical axis of the lens  22 , the protrusions do not push the clips  15 ,  15  outward and away even when the laser light source unit  10  is slid over the pedestal  60 , and the securing strength of the clips  15 ,  15  do not weakened due to width of the clipped protrusions becoming narrower. 
     If the laser light source unit  10  is mounted before the vibrating mirror  31  is installed in the module case  2 , a focus adjusting mirror (not shown) can be inserted in the position of the vibrating mirror  31  to reflect the laser beam emitted via the lens  22  and aperture  23  towards the outside. A laser beam measuring device (not shown) can then be used to precisely measure the diameter of the laser beam and to properly position the moving laser light source unit  10 . The laser adjusting mirror is removed once the adjustment has been made. 
     After making the adjustment, the clips  15 ,  15  are secured with the protrusions  12 ,  12  on the laser light source unit  10  and the protrusions  62 ,  62  on the pedestal  60  using an adhesive  16 ,  16 , which is the second securing means. The laser light source unit  10  then cannot move even in the direction of the optical path of a beam passing through the optical axis of the lens  22  (the adhesive  16 ,  16  is omitted from  FIG. 3 ). 
     After securing this with adhesive and attaching all of the necessary components including the vibrating mirror  31  to the module case  2 , as shown in  FIG. 10A  and  FIG. 10B , the circuit board  3  is attached to the module case  2  with the screws  4 ,  4  shown in  FIG. 1  ( FIG. 10A  and  FIG. 10B  are cross-sectional views of the components from the position of line  10 - 10  in  FIG. 9 ). At this time, the terminals  13  on the laser light source unit  10  are passed through the through-holes  7  in the circuit board  3 . The terminal  13  are connected to the electrodes on the circuit board  3  (not shown in the figure) and embedded in the through-holes  7  using solder  17 . 
     Due to manufacturing errors in the module case  2 , there is some individual variation in the position of the laser light source unit  10  after position adjustment. Therefore, the diameter of the through-holes  7  should be somewhat larger than the cross-section of the terminals  13  so that the through-holes  7  can be passed over the terminals  13  even when the position of the laser light source unit  10  is somewhat off. By installing the analog LSI  63  used to convert the analog electric signals outputted by the light detector  43  into digital data to the circuit board  3  in the position immediately above the laser light source unit  10  mounted on the module case  2 , space can be effectively utilized. 
     The configuration and method for attaching the laser light source unit  10  to the module case  2  explained above allows the laser light source unit  10 , while secured to the pedestal  60  by clips  15 ,  15 , to be moved toward a position near the lens  22  and also toward a position away from the lens  22 . Therefore, unlike inserting the light-emitting unit into a lens barrel hole under pressure and aligning the position of the light source, as described in JP 4,331,597 B2, the adjustment can be made easily and precisely. 
     In other words, the light source, once pushed in close to the collimating lens, cannot be adjusted in the direction away from the lens, in the case of insertion under pressure. Therefore, the push in operation has to be performed very carefully so as not to overshoot the target point. In order to be safe, it has to be adjusted slightly in front of the target point. However, the configuration and steps described with reference to  FIG. 7  through  FIG. 10  allow the laser light source unit  10  to be adjusted easily away from the lens  22  when after being moved too close. The laser light source unit  10  can be adjusted without fear, and the unit can be repeatedly readjusted until the error is sufficiently small with respect to the target point. 
     Also, the configuration is not complicated, the overall size is compact, the components are inexpensive, and the manufacturing can be performed with precision. By forming a groove  61  in the pedestal  60  for inserting the laser light source unit  10 , the laser light source unit  10  is easily kept from moving in directions other than the optical path passing through the optical axis of the lens  22 , which do not require adjustment. 
     By providing protrusions  12 ,  12  and protrusions  62 ,  62 , the clips  15 ,  15  can be installed easily using a tool as shown in  FIG. 8A  through  FIG. 8D . As a result, the mounting step can be simplified. If the pedestal  60  is at the end of the module case  2 , at least one gap is installed in the side surfaces of the module  2  for the clips  15  to be inserted. This causes fewer design limitations than having the gaps on the bottom surface. 
     (3) Arrangement of Bearing  33  and Support Shaft  34  for Vibrating Mirror Holder  32  ( FIG. 11  and  FIG. 12 ) 
     The following is an explanation of the arrangement of the bearing  33  and the support shaft  34  for the vibrating mirror holder  32 .  FIG. 11  is a schematic diagram showing the cross-section of the portion of the optical scanning module  1  extending from the coil  36  to the support shaft  34  and the vibrating mirror holder  32 .  FIG. 12  is a cross-section of the corresponding comparative example. However, in these figures, the cross-section of the module case is shown only near where the support shafts  34 ,  234  are mounted. 
     In the optical scanning module  1 , as shown in  FIG. 11 , an opening  80  is formed in a position on the circuit board  3  corresponding to the support shaft  34 , and one end of the support shaft  34  and the bearing  33  are passed through the opening  80 . The other end of the support shaft  34  is attached to the module case  2 . By using this configuration the size of the bearing  33  is not restricted to the thickness of the optical scanning module  1  (the size lengthwise with respect to the support shaft  34 ). 
     When the support shaft  234  and the bearing  223  are accommodated inside the optical scanning module, as in the comparative example shown in  FIG. 12 , the length of the bearing is not sufficient if the optical scanning module is too thin. There is a danger of misalignment of the bearing  233  and the support shaft  234 , and the vibrating mirror holder  232  may rotate around the support shaft  234  with too much fluctuation (the rotational shaft of the vibrating mirror holder  232  will easily be misaligned with the support shaft  234 ). 
     However, there are no such problems with the configuration shown in  FIG. 11 . The vibrating mirror holder  32  can rotate stably around the support shaft  34  even when the optical scanning module  1  is thin. Thus, there are no restrictions on the size of the bearing and the optical scanning module  1  can be compact. 
     In the optical scanning module  1 , as shown in  FIG. 11 , a cover  38  is installed on the circuit board  3  surface opposite that of the module case  2  in order to cover the support shaft  34  and the bearing  33  protruding from the opening  80 . The cover  38  is secured on the circuit board  3  using solder  39 . By installing a cover  38 , the bearing portion of the vibrating mirror holder  32  can be protected from the infiltration of moisture and contaminants. If contaminants and moisture get into the bearing portion, the smooth rotation between the support shaft  34  and the bearing  33  is impeded. A cover  38  effectively prevents this. However, a cover  38  is not essential. This can be secured to the circuit board  3  using an adhesive or screws or it can be fitted into the circuit board  3  using some other appropriate securing means. 
     In the example shown in  FIG. 11 , an opening  80  is formed in the circuit board  3 . However, an opening can also be formed in the abutting surface when the support shaft  34  extends to the side opposite the securing position. In this configuration, the circuit board at that surface is not essential. The bearing  33  passing through the opening  80  can have the desired thickness. In other words, it does not have to have the minimum thickness able to realize the bearing function. If the diameter of the opening  80  is nearly the same or slightly larger than the diameter of the bearing  33  passing through, a vibrating mirror holder  32  including a bearing  33  can be supported and kept from becoming misaligned by the opening  80 , even if the rotational shaft of the vibrating mirror holder  32  is offset from the support shaft  34 . 
     (4) Performance and Configuration of Lens  22  ( FIG. 13  through  FIG. 17 ) 
     The following is an example of the performance and configuration of the lens  22 .  FIG. 13A  and  FIG. 13B  are diagrams used to explain the powers of the lens  22 .  FIG. 14  is a diagram showing the shape of the spot formed by the laser beam passing through the lens  22 .  FIG. 15  is a diagram showing the shape of the lens  22 .  FIG. 16A  and  FIG. 16B  are diagrams used to explain the powers of the lens in a comparative example.  FIG. 17  is a diagram used to explain the manufacturing method for the lens  22 . 
     If the optical scanning module  1  is used to read code symbols arranged in bar-type modules such as barcodes and two-dimensional barcodes, the spot of the laser beam used to scan the code symbols is preferably not round but oval-shaped with the long axis aligned lengthwise with respect to the code symbols. This can reduce the effects of bar contamination and friction. In the optical scanning module  1 , as described above, an oval-shaped spot can be obtained from a lens  22  with the powers of both a collimating lens and a cylindrical lens only in one of the X direction and Y direction perpendicular to each other (both the X axis and the Y axis are perpendicular to the optical axis). 
     More specifically,  FIG. 13A  and  FIG. 13B  show the shape of the lens  22  in a cross-section on the plane including the optical axis and the X axis and in a cross-section on the plane including the optical axis and the Y axis, respectively. It is clear from the figures that the lens  22  has the power of a cylindrical lens on plane  22   a  as the cross-section in the X-axis direction is planar and the cross-section in the Y-axis direction is concave, and has the power of a collimating lens on plane  22   b  as the cross-section in the X-axis direction and the cross-section in the Y-axis direction are both convex. 
     A laser beam emitted from the semiconductor lens  11  of the laser light source unit  10  arranged in the appropriate location and passed through the lens  22 , as shown in  FIG. 14 , forms a beam spot with an oval shape in which the Y-axis direction is the long axis. Afterwards, the unstable portions of the beam spot profile are cut off at the ends by the aperture  23 . The beam is then reflected by the vibrating mirror  31  and emitted to the outside. 
     Here, the lens  22 , as shown in  FIG. 15 , has a rectangular shape, which is the same shape as the opening  23   a  in the aperture  23 . The size, however, is slightly larger than the opening  23   a.  A size slightly larger than the opening  23   a  allows the laser beam passing through the lens  22  to reach the aperture  23  with a size larger than the opening  23   a.  The size of lens  22  can be slightly smaller than the opening  23   a  in the Y-axis direction with the beam widening. 
     The ends of the laser beam passing through the lens  22  do not pass through the opening  23   a  but are instead cut off by the aperture  23 . If the lens  22  is of a certain size, this does not adversely affect the quality of the scanning beam. During manufacture, the lens is first manufactured in a round shape. When a lens with a diameter conforming to the long sides of the aperture  23   a  is used, the width also has to be the same in the short-side direction in order to install the lens. However, this wastes space. Therefore, by using a lens  22  with the same shape as the opening  23   a , wasted space can be eliminated. This makes a positive contribution to downsizing of the optical scanning module  1 . 
     Rather than install a collimating lens  222  and a cylindrical lens  223 , as in the comparative example shown in  FIG. 16A  and  FIG. 16B , lens  22  combines the power of both in a single lens. This reduces the number of lenses required and saves space. In order to conform the shape of the lens  22  to the opening  23   a,  a rectangular lens can be manufactured. For example, as shown in  FIG. 17 , a lens plate molded into a shape combining multiple lenses can be cut to the size of an individual lens in order to manufacture a rectangular lens inexpensively. 
     Because the lens  22  has different powers in different directions, it has to be installed in the right direction inside the module case  2 . It would be difficult to readily grasp the right direction if the lens were round. However, in the case of a rectangular lens, the X axis and the Y axis are cut to conform to the short side and the long side. This makes it easy to align in the right direction during installation. It also helps to reduce the number of manufacturing steps. 
     (5) Embodiment of the Optical Information Reading Device ( FIG. 18 ) 
     The following is an explanation of an embodiment of an optical information reading device equipped with the optical scanning module  1  described above.  FIG. 18  is a block diagram showing the configuration of the code scanner  100  that is the embodiment of the optical information reading device. 
     The code scanner  100  is a device that reads a barcode, which is code symbols constituted of modules of black bars and white bars whose optical reflectivity differs from their surroundings. As shown in  FIG. 18 , the code scanner  100  includes an optical scanning module  1  and a decoder  120 . The optical scanning module  1  is the optical scanning module explained with reference to  FIG. 1  through  FIG. 17 . The optical scanning device  25  is the optical system outputting a scanning beam from the laser light source unit  10  to the vibrating mirror  31 . The light detector  43  is the light detector  43  shown in  FIG. 3 . 
     Electric signals corresponding to the strength of the reflected light obtained when the beam outputted from the optical scanning device  25  is reflected by the barcode B formed on the scanned object are outputted by the light detector  43  to the pad electrodes  3   a  on the circuit board  3  via the output electrodes  53 . The signals are then inputted to the analog LSI  63  on the circuit board  3 . 
     The analog LSI  63 , as shown in  FIG. 18 , has an IV converter  111 , a preamp  112 , a filter processor  113  and a binarization circuit  114 . This circuit processes the electric signals outputted by the light detector  43  and outputs a pulse sequence to the decoder for the barcode symbols. More specifically, the IV converter  111  converts the current signals outputted from the photodiode of the light detector  43  to voltage signals. Next, the preamp  112  amplifies the voltage signals converted by the IV converter  111 . The IV converter  111  and the preamp  112  form an amplifier which converts the current signals to voltage signals and amplifies them. 
     Afterwards, noise is removed from the signals outputted from the preamp  112  by the filter processor  113 , and the signals are inputted to the binarization circuit  114 . The binarization circuit  114  includes a low-pass filter and a logic circuit, and outputs a pulse sequence indicating the positions of the white bars and the black bars. These correspond to the rows of bars constituting the barcode symbols. By inputting the pulse sequence to the decoder  120 , information in the form of an arrangement of white bars and black bars is received and converted to information represented by the arrangement. The code scanner  100  can have a device for outputting the information obtained by the decoder  120  to an external information processing device such as a personal computer or a handheld terminal. The decoder  120  can also be located outside of the code scanner  100 . 
     This ends the explanation of the embodiment, but the configuration of the devices and the type of code symbols to be read are by no means limited to the explanation in this embodiment. The optical information reading device in the present invention can be configured as a stationary device or as a portable device. The optical devices of the present invention such as the optical scanning module  1  can be used in optical information reading devices. However, nothing prevents them from being used in other devices. The same is true of the light detector and the light source unit mounting method. 
     The structures and variations described above can be applied individually or in combination where appropriate consistent with the scope of the present invention. The characteristics listed in (1) through (4) can be applied individually to sufficient effect. When only some of the characteristics are applied, the spots where the characteristics listed in (1) through (4) are not applied have the configurations described in the comparative examples and related art examples. 
     Use of the optical device and light source unit mounting method of the present invention allows a module used to scan an object with a laser beam and detect the reflected light to be made more compact. The same light detector can also be used to make the optical information reading device of the present invention more compact. 
     Although a preferred embodiment of the invention has been disclosed for illustrative purposes, those skilled in the art will appreciate that many additions, modifications and substitutions are possible without departing from the scope and spirit of the invention as defined by the accompanying claims. 
     KEY TO THE FIGS. 
     
         
           1  . . . Optical Scanning Module 
           2  . . . Module Package 
           3  . . . Circuit Board 
           4  . . . Screw 
           5  . . . Slit 
           6  . . . Opening 
           7  . . . Through-Hole 
           8  . . . Slit 
           9  . . . Gap 
           10  . . . Laser Light source Unit 
           11  . . . Semiconductor Laser 
           12  . . . Protrusion 
           13  . . . Terminal 
           15  . . . Clip 
           21  . . . Mirror 
           22  . . . Lens 
           23  . . . Aperture 
           31  . . . Vibrating Mirror 
           32  . . . Vibrating Mirror Holder 
           33  . . . Bearing 
           34  . . . Support Shaft 
           35  . . . Moving Magnet 
           36  . . . Coil 
           37  . . . Yoke 
           38  . . . Cover 
           39  . . . Solder 
           41  . . . Light-Receiving Lens 
           42  . . . Filter 
           43  . . . Light Detector 
           51  . . . Substrate 
           52  . . . Coating Material 
           53  . . . Output Electrode 
           54  . . . Notch 
           55  . . . PD 
           60  . . . Pedestal 
           61  . . . Groove 
           62  . . . Protrusion 
           63  . . . Analog LSI 
           70  . . . Jig 
           80  . . . Opening 
           100  . . . Code Scanner