Abstract:
A portable construction layout tool generates laser beams in two or more directions related by a specific angle, such as 90°. The instrument emits two fans of light in such a way as to project a pair of lines on the floor, wall or other surface on which the instrument is mounted or placed, with the intersection of the two being visible rather than being a virtual intersection hidden beneath the instrument itself, enabling easier setup. Compared to rotating-beam instruments, the disclosed device is simpler by avoiding moving parts and provides for better visibility. In a preferred embodiment the non-collimated beam from a laser diode is used, and is passed through a cylinder lens to converge the beam on the narrower axis to generate the desired fan of light to be projected as a line.

Description:
BACKGROUND OF THE INVENTION 
     The invention concerns optical layout or measuring equipment, and in particular encompasses a laser projector tool mounted on or placed against a surface, that produces intersecting lines on that surface without moving parts to project the lines, and with a visible line intersection displaced from the instrument housing, for more convenient use. 
     Laser-projecting instruments are well known in the field of surveying and construction layout and as measuring devices. Prior patents show several examples of such tools that project lines, primarily by rotating a beam to make an apparently solid line on a surface. Some such instruments have included two rotating projected beams to produce intersecting lines at right angles to each other. See, for example, U.S. Pat. Nos. 5,218,770 and 6,202,312 in which such devices are shown as prior art. See also U.S. Pat. No. 6,065,217. 
     It has also been known to form lines on a surface by placing a cylindrical lens in the path of a collimated laser beam, thus spreading a narrow beam of light into a planar fan of light that forms a line on a surface. Again, see U.S. Pat. No. 6,202,312 showing such instruments, and the disclosure of that patent is incorporated herein by reference, particularly as to discussion of prior art. 
     There have been laser tools that produce two lines with a visible intersection, such as described in U.S. Pat. No. 5,539,990, but with an important difference from the device of this invention. The prior tools produced the intersecting lines on a surface that is generally perpendicular to the surface on which the instrument rests. 
     Other laser reference tools have produced spots of light on a surface, rather than solid lines of light. For example, see U.S. Pat. No. 6,005,719. 
     See also copending application Ser. No. 09/684,696, now U.S. Pat. No. 6,502,319, owned by the assignee of this invention, showing generation of lines on a surface on which the instrument is placed. 
     It is among the objects of this invention to produce an efficient portable laser reference tool that generates at least two intersecting lines of laser light on a floor or other surface against which the tool is placed, with the intersection being displaced from the instrument and visible. An accompanying object is to generate such light beams and lines without the use of moving parts, such as spinning lasers or mirrors. 
     SUMMARY OF THE INVENTION 
     A portable construction layout tool generates laser beams in two directions related by a specific angle, such as 90°. The instrument emits two fans of light in such a way as to project a pair of lines on a floor, wall or other surface on which the tool is mounted, with the intersection of the two fans being visible rather than being a “virtual” intersection inside or below the instrument, thus enabling easier setup. Compared to rotating-beam instruments, the disclosed device is simpler by avoiding moving parts, and provides for better visibility. In a preferred embodiment the non-collimated beam from a laser diode is used, and is passed through a cylinder lens to converge the beam on the narrower axis to generate the desired fan of light to be projected as a line. 
     In one embodiment two different laser diodes and lenses are used to generate the two fans of light, and in another embodiment a single laser diode is employed, with optics to produce the two fans of light. 
     It is thus a primary object of the invention to provide a rugged and reliable laser instrument, without moving parts, to produce at least two lines of light on the floor or other surface on which the instrument is mounted or placed, with the intersection of the two lines visible to the user. These and other objects, advantages and features of the invention will be apparent from the following description of a preferred embodiment, considered along with the accompanying drawings. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic perspective view showing an implementation according to one embodiment of the invention. 
     FIG. 1A is a view similar to FIG. 1 but with different optics. 
     FIG. 2 is a similar schematic perspective view showing an implementation according to another embodiment of the invention. 
     FIG. 3 is another schematic perspective view showing a further implementation of the invention involving a single laser diode. 
     FIG. 3A is a schematic side elevation view showing another embodiment, wherein the lines at 180° are produced. 
     FIG. 4 is a perspective view showing the exterior of an instrument according to one preferred embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention involves the use of two light beams combined to draw intersecting lines on the surface which the instrument is mounted or placed. The visible lines can be at a 90° angle or any other desired angle. 
     In FIG. 1, two lasers  10  and  12  produce collimated beams  14  and  16  which are passed through cylinder lenses  18  and  20  to generate fans of light  22  and  24  which produce lines of light  26  and  28  on a surface  30 , which is the surface against which the instrument&#39;s housing (not shown in FIG. 1) is placed. The lasers and optics are housed in or fixed to a single structure and are mechanically aligned to the desired angle between the fans  22 ,  24  and the intersecting lines  26 ,  28 . The lines  26 ,  28  intersect at a point  32  visible to the user, projected outside the instrument. Note that in the implementation of FIG. 1 the beams approaching the cylinder lenses are collimated. 
     FIG. 2 is an arrangement similar to FIG. 1, again utilizing two cylinder lenses  18 ,  20  to produce fans of light  22 ,  24  that project as intersecting lines  26 ,  28  on the surface  30 . However, in this embodiment the fans of light are produced by a single laser  35  producing a single collimated laser beam  36 . The beam  36  encounters a beam splitter  38  which partially reflects the beam at  40  and partially transmits the beam at  42 . The reflected beam  40  is twice more reflected off mirrors  44  and  46 , to pass through the cylinder lens  20  as shown (this could be done with only one reflection beyond the beam splitter by directing the beam  40  directly at the mirror  46 , properly directed). In this embodiment, as in FIG. 1, the positions and orientations of the cylinder lenses,  20 , can be manipulated relative to the axes of the approaching beams,  40  and  42 , so as to optimize the projected lines,  26  and  28 , for brightness and general quality on the projection surface,  30 , the same surface on which the instrument may rest. 
     In the embodiment shown in FIG. 1A, a laser projector  10   a  produces a beam which is not collimated and which projects a generally elliptical diverging beam of light  14   a , wider on a long axis which is arranged perpendicular to the work surface, i.e. in a plane perpendicular to the surface  30 . Similarly, a laser projector  12   a  produces a like beam  16   a . In this case, the laser diodes&#39; naturally widely diverging beams are employed to produce fans of light  22   a ,  24   a . A cylindrical lens  50  is used for the beam  14   a , arranged with its axis essentially at right angles to the position of the cylinder lens  18  of FIG. 1, and generally perpendicular to the work surface  30 . A cylinder lens  52  is used for the beam  16   a  in a similar arrangement. The purpose of the cylinder lenses  50 ,  52  is not to produce a fan of light as it was in FIG. 1, but to converge the beam in the smaller axis of divergence. Thus, if the raw beam is diverging at an angle of about 10° (at full width half maximum) on the minor axis, this diverging angle will be focused so that the beam after the lens  50  will be converging to form a substantially focused line  28   a  on the surface. The beam  22   a  exiting the cylinder lens  50  is converging as regards the narrow dimension of the approximately elliptical beam (the parallel direction in the far field of the diode beam), due to the positioning of the lens  50  in the path of the beam, toward the approximate focus at the line  28   a . The line  28   a  has a length along which the distance from the diode and the lens  50  varies, partially depending on the height of the diode from the projection surface. To achieve a high quality projected line the focus must be adjusted accordingly. This can be accomplished by appropriately tilting the cylinder lens  50 , which in essence creates a lens with variable focal length. The situation is the same at the other cylindrical lens  52 , receiving and focusing the light from the diode  12   a . Note that due to angular effects the cylinder lens creates a varying focal length effect in any event, even if not tilted. The tilt is set to produce the highest quality projected line possible. If desired a lens with built-in variation in focal length throughout the lens&#39; length could be used. 
     In all of FIGS. 1,  1 A, and  2 , the diodes and optical components are mounted in a housing or frame such that the intersection point  32  is projected on a surface  30  (such as a floor) outside the instrument (and preferably on which the instrument is placed), for clear visibility of the intersection point  22  by the user. It should be understood that the optical arrangements shown in FIGS. 1,  1 A and  2  can produce any angular relationship desired between the two lines on the surface, between 0° and 180°. Also, it should be understood that the configuration shown in FIG. 1A can also be employed in FIG. 2, provided the optical path of the reflected portion of the laser diode beam is sufficiently short so that the reflectors and the second cylindrical lens need not be inordinately large due to the diverging beam. 
     FIG. 3 shows in schematic perspective a preferred arrangement in which one laser diode  60  is used to produce two intersecting lines of light  62 ,  64  on a surface  65 . In this implementation, like that of FIG. 1A, the laser diode beam  66  is not collimated. The diode is positioned such that the beam  66  straddles an angled mirror or pair of mirrors  68  in roof like configuration as shown, with the wider beam divergence angle, i.e. the perpendicular-to-junction beam intensity distribution indicated extending left to right in FIG.  3 . Thus, essentially one-half of the light is projected from the roof mirror  68  at each of two secondary mirrors  70  and  72 , beyond which the diverging fan of light, approximately half an ellipse in cross section at each side, is directed through a cylinder lens  74 ,  76  at each side. The cylinder lenses, as in FIG. 1A, do not affect divergence in the wide-divergence axis, or perpendicular axis, but only act to converge the light spreading along the smaller axis, or parallel axis. As noted above, the lenses  74 ,  76  can be tilted appropriately so as to adjust focus so that the entire lines  62 ,  64  within a useful range of length, are approximately in focus. 
     Other arrangements, with different numbers of mirrors, are possible to produce a result similar to that of FIG.  3 . Also, the cylinder lenses  74 ,  76  can be positioned between the folded mirror  68  and the second reflectors  70 ,  72  if desired, rather than the position shown in FIG.  3 . Further, by rotating the mirrors  70  and  72  and repositioning the cylinder lenses  74 ,  76 , any angle of intersection between the lines  62  and  64 , between 0° and 180° can be generated (at 180° the second mirrors  70 ,  72  are not needed—see FIG.  3 A). The beam path is simplest if the beam portions  66   a ,  66   b  are approximately coplanar, i.e. defining planes generally perpendicular to the surface  65 . 
     The conventional approach to generating two lines at 90°, projecting parallel to a surface, has been to pass a single collimated beam through a beam splitter. Beyond the beam splitter, the beams are then passed through cylinder lenses to generate lines. This generates the desired lines at 90°, at high accuracy, but has the drawback of hiding the point of intersection of the lines, which is in the beam splitter. In contrast, the approach of this invention uses two separately aimed lines to allow the drawing of the intersection on the desired surface. 
     FIG. 3A shows a variation in which two oppositely directed lines, i.e. lines at 180°, are produced on a surface  65 . Here, the diverging beam is again divided by a roof mirror or mirror pair  68  as in FIG. 3, but no further reflection is made on the two beam halves. Opposing fans of light  66   a ,  66   b  are focused in the lesser angle of divergence by cylinder lenses  76 ,  78 . Again, these are tilted appropriately to produce lines of light on the surface  65  that are essentially focused throughout their length. In this case, there is no visible intersection, but the purpose is to produce lines of light in opposite directions, with the position of the instrument as a reference. 
     FIG. 4 shows an example of the exterior of an instrument  80  of the invention. This is an instrument with optics such as shown in FIG. 1 or FIG. 1A, using two separate laser diodes. Separate housings  81  and  82  are mounted on a base  84 . As can be envisioned from FIG. 4, the two housings  81  and  82  could be repositioned at different angles relative to each other on the base  84 , thus enabling the integration of a protractor into the instrument. In FIG. 4, the two housings are arranged to produce two lines of light at 90° on a surface on which the base  84  rests. An appropriate mechanism can be employed as a base, providing for rotation of one housing relative to the other, preferably about the point of intersection. 
     The principles of the invention can also be applied to an instrument producing more than two beams of light, having one (or more) intersections. A typical embodiment would be an instrument producing lines on a surface at right angles to one another, with a visible intersection as described above, and with an additional line projected at 45°, intersecting the other two lines at the visible intersection point. This can be achieved with three separate laser diodes, e.g. with another housing such as shown at  81  and  82  positioned at the 45° position in FIG.  4 . It can also be done with a beam divider to produce three separate beam portions by spatial beam division, with further reflection of these beam segments to achieve the angularly related three fans of light. See, for example, U.S. Pat. No. 6,154,319 assigned to the assignee of the this invention, showing reflective elements for producing three, four or five beams. 
     The above described preferred embodiments are intended to illustrate the principles of the invention, but not to limit its scope. Other embodiments and variations to this preferred embodiment will be apparent to those skilled in the art and may be made without departing from the spirit and scope of the invention as defined in the following claims.