Abstract:
An apparatus and method for efficiently generating a visible line of light on a surface such as a wall or a floor for the purpose of facilitating the layout process used in construction. The apparatus comprises a light beam generator projecting a beam of visible light on a surface. Reference marking elements on the instrument correspond to the light beam&#39;s position. One or more level vials may also be included for indicating vertical and horizontal, as well as a magnet for mounting and a reference bracket for a stud-finder instrument.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to hand tools, and in particular the invention is concerned with a hand tool for projecting a reference beam of visible light for precise alignment on floors and walls. 
     For some time laser beams have been used in construction for level references, vertical references and layout on floors and walls. Typically a construction worker marks the floor or walls indicating the location of walls, windows, or other building elements to be constructed. A chalk line is often used to permanently mark the walls or floors. This is a two man job with one man holding one end of the chalked string while the other snaps it, releasing chalk dust which makes the mark. 
     The most common prior laser device is a simple carpenter&#39;s level with level vials and with a laser beam projector attached. See FIG.  1 . Many thousands of these are in use today. U.S. patents in this area include Genho U.S. Pat. No. 4,221,483, Rando U.S. Pat. No. 6,009,630 and others. Although indicating level, these levels do a poor job of projecting a beam on a floor or wall. LeveLite Technology, Inc., the assignee of this invention, makes a product for producing two beams of visible light on the floor for the purpose of laying out a 90° corner. It is described in U.S. patent application No. Ser. No. 09/264,371, U.S. Pat. No. 6,202,312, incorporated herein by reference. This instrument uses a collimated beam of light and an adjustable cylinder lens to convert the round beam into a fan of light and thus project a line on the surface. This is not a very efficient use of the laser diode light because of the natural divergence of the diode and cropping of the beam in collimation. Typically the laser diode beam divergence is 30° in one axis and 8° on the transverse axis. About half the light is lost in the collimation process. In addition, the line can be focused for only one distance. Such an optical system is shown in plan view in FIG. 2 herein and in side view in FIG. 3 herein, and is the present state of the art. Both the problems of efficient use of the laser light and focusing continuously along a line are solved by the current invention. 
     SUMMARY OF THE INVENTION 
     This invention allows the user to project a highly visible line on a surface. In addition it allows the line to be adjusted to true vertical or horizontal with the aid of a level vial when used on a vertical surface, e.g. a wall. An attachment to a stud-finder instrument is further provided. In some cases a magnet facilitates holding the unit to metal studs. The instrument is partially described in Disclosure Document No. 476310. 
     The simple, efficient optical system is the important feature of this invention. The instrument provides a highly visible line which can temporarily act as a chalk line for the purpose of marking points along the line, when requiring a more permanent mark, or for operations along the line with the laser line in place. 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 perspective view showing a prior art carpenter&#39;s level with projected laser beam. 
     FIGS. 2 and 3 are elevation and plan views showing a prior art laser line projector schematically using a cylinder lens. 
     FIGS. 4 and 5 are elevation and plan views illustrating the principle of line-projection according to the invention. 
     FIGS. 6 and 7 are elevation and plan views similar to FIGS. 4 and 5 but showing a different embodiment. 
     FIG. 8 is a schematic perspective view showing a laser instrument projecting a line on a surface in accordance with the principles of the invention. 
     FIG. 9 is a sectional elevation view schematically showing the instrument of FIG. 8, with some elements omitted for clarity. 
     FIGS. 10 and 11 are perspective views illustrating use of the instrument on a wall, to project a line which may be horizontal or vertical on the wall surface. 
     FIG. 12 is a perspective view showing the instrument used along with a stud finder, to project a vertical line indicating location of an entire stud. 
     FIGS. 13,  14  and  15  are schematic side views showing the components of the invention projecting a line on a surface and showing three different methods for utilizing the entire wide angle of the diverging beam along the long axis. 
     FIGS. 16 and 17 are schematic side views showing another form of the invention using cylindrical concave mirrors for focus in the narrow angle of the beam. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     An optical system is shown in FIGS. 4 and 5. A laser diode  2  is positioned above a surface  4  to be marked, with the wide divergence angle of the laser, i.e. the major or long axis, perpendicular to the surface. In other words, a plane which is longitudinal relative to the laser diode and which includes the long axis of the beam is perpendicular to the surface. Cylinder lenses  6 ,  8 ,  10  project a beam  11  from the laser diode  2  onto a continuous line  14 . The widths of the lenses are chosen to collect all the light from the narrow divergence angle (short axis) of the diode, substantially without cropping. The use of a plurality of lenses in the direction of the wide divergence (long axis) allows most of the light to be collected making the system efficient. The ability of each lens to be adjusted for a particular distance to produce a fine line is superior to the prior art; focus adjustment for distance can be done either by use of different focal length lenses or by adjustment of distance from the diode to each lens. The figures show how substantially all of the laser power in the wide and narrow divergence angles of the diode is projected into a tapering fan and into a line on a surface. 
     Another preferred embodiment of the optical system is shown in two views in FIGS. 6 and 7. A laser diode  15  projects a line  16  on a surface  18  using a single cylinder lens  20 . The lens is tipped to provide the best focus for the entire surface by varying continuously the distance between the lens and the diode along the wide angle or long axis of the diode&#39;s beam. This provides variation for best focus on the line  16  on the surface. The diode is located preferably about 25 mm to 125 mm above (or away from) the surface to provide the angle needed to distribute the light along the floor (or other surface on which the device is used). 
     A preferred embodiment of an instrument is indicated generally by  22  in FIG. 8. A housing  24  contains the projection system described above. A fan-shaped beam  26  is projected onto a surface  28  to form a line  30 . The housing has a battery door  32  and marking notches  34  and  36  which are in the same plane as the projected beam  26  and are used for positioning the line  30  and the instrument on marks on the floor during layout. An on-off switch  38  and sights  40  and  42  are in the plane of the beam  26  and may be used for sighting the instrument for desired alignment. Details of the internal construction of the instrument  22  are shown in FIG. 9. A battery  39  and wires  37  are included. 
     A slightly modified instrument  44  shown in FIG. 10 is the same as  22  except for the addition of a horizontal indicating level vial  46 . A magnet  45  is provided to hold the instrument to a steel stud as may be necessary from time to time. The sights and switch of FIGS. 8 and 9 have been removed for clarity in FIG.  10 . The unit is positioned on a vertical wall  48 . A second level vial  50  for indicating vertical is also mounted to the line projector. In this figure a horizontal line  52  is projected on the wall. 
     FIG. 11 shows the instrument of FIG. 10 positioned on the vertical wall projecting a vertical line  54  on the wall  48 . 
     FIG. 12 shows the instrument  44  of FIGS. 10 and 11 on the vertical wall  48  with a bracket  56  attached to the instrument. The bracket holds a stud-finder  58  which indicates the location of a stud behind a wall with its indicator lights  60 . Using this combination instrument one location of the stud may be used to locate the entire length of a vertical stud. This eliminates the need to find the stud at several locations up and down the wall. 
     In another preferred embodiment the light in the wide angle divergence or long axis direction of the diode is used efficiently by employing one or more mirrors to reflect part of the light back onto the line as shown in FIG. 13. A laser diode  64  directs a beam of light  62  to a cylinder lens  66  to form a line  68 . A portion of the light  70  exiting the lens  66  strikes mirrors  72  and  73  and is directed onto the line  68  increasing its brightness, at the distant portion of the line where the line is weakest. A prism  74  can also be used to redirect the portion  70  back onto the line  68  as shown in FIG.  14 . FIG. 15 shows that a positive cylinder lens  76 , oriented transversely to the cylinder lens  66 , can be used to narrow the divergence of the diode laser beam as it reaches the cylinder lens  66  to efficiently use the power from the laser diode in this preferred embodiment. Instead of two separate cylinder lenses  66  and  76 , a hybrid lens could be fashioned to accomplish both functions. 
     In another preferred embodiment the light beam is focused in the narrow angle of divergence with a cylindrical mirror instead of a cylinder lens, achieving similar beam distribution and focus. FIG. 16 shows the projector  80  comprising a laser diode  82  and cylindrical reflecting surface  84  projecting the beam, diverging in its wide angle as shown, from the laser diode into a fan of line  88  on a surface. The back-reflection arrangement shown allows the beam conveying element  84  to be placed at a proper angle of tilt to achieve optimum focus along the length of the line  88 , as shown with the lens in FIGS.  6  and  13 - 15 . The beam divergence in the wide angle can be further controlled by a lens  90  shown in FIG. 17 which otherwise contains the same elements of FIG.  16 . It is also possible to include the optical power of the lens  90  in the mirror  84 , by providing a mirror which curves concavely in the transverse direction, i.e. appearing arcuate and concave in side view, rather than linear as in FIGS. 16 and 17. This becomes an expensive optical element but is theoretically possible. In addition, the focus correction for a range of distance, as achieved by the tilted conveying element, could be realized using a concave cylinder reflecting surface that varies in radius of concavity along its length, to provide varying focal length for this narrow angle of divergence. 
     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.