Apparatus and method for providing multiple reference laser beams

Apparatus for projecting a laser beam to provide multiple reference beams includes a beam diverting assembly rotatably mounted at an end of a housing from which emerges a laser beam generated within the housing, and a pentaprism assembly disposed stationarily at the housing end outwardly of the beam diverting assembly. The beam diverting assembly receives the laser beam and splits it into orthogonally-disposed transmitted and reflected beam components. Rotation of the beam diverting assembly about the axis of the transmitted beam component causes rotation of the reflected beam component to define a reference plane. The pentaprism assembly receives the transmitted beam component from the diverting assembly and deflects it to define a stationary reference line disposed in a generally parallel spaced relationship to the reference plane defined by the rotating reflected beam component. Also, an end cap mounts the pentaprism assembly at the housing end and a sighting telescope outwardly of and adjacent to the pentaprism assembly for facilitating alignment of the reference line.

CROSS REFERENCE TO RELATED APPLICATION 
Reference is hereby made to the following copending U.S. patent application 
dealing with related subject matter and assigned to the assignee of the 
present invention: "Multiple Reference Laser Beam Apparatus" by Theodore 
J. Markley, Richard J. Olmor, William K. Vatter and Mark D. Sobottke, 
assigned U.S. Ser. No. 734,325 and filed May 15, 1985, now U.S. Pat. No. 
4,676,598. 
BACKGROUND OF THE INVENTION 
The present invention generally relates to a method and apparatus for 
providing reference laser beams and, more particularly, to such a method 
and apparatus in which two such beams simultaneously define a reference 
plane and a reference line spaced above and extending generally parallel 
to the plane. 
Laser beam systems have been employed in numerous surveying and 
construction applications. In one such system disclosed in U.S. Pat. No. 
4,062,634, issued Dec. 12, 1977 to Rando et al, and assigned to the 
assignee of the present invention, a laser beam projecting apparatus 
provides a rotating laser beam which establishes a reference plane. The 
rotating laser beam is used to provide a continuous, visible plane of 
light that creates a constant horizontal benchmark of elevation over an 
entire work area. Also, one or more laser beam detectors are placed at 
considerable distances from the projecting apparatus for intercepting the 
rotating laser beam and determining elevations of selected points 
throughout the work area. 
In the laser beam projecting apparatus of the cited patent, the generally 
horizontal rotating reference laser beam is produced by projecting the 
beam generally upward and then deflecting it ninety degrees within a 
pentaprism or penta-mirror assembly. The pentaprism assembly is rotated 
about a vertical axis within the projecting apparatus to cause the 
horizontal beam to rotate and define the reference plane. 
It is often desired to align the plane defined by a rotating reference beam 
in a generally perpendicular relationship with another building structure, 
for example such as a wall. The multiple reference beam apparatus of the 
above cross-referenced application has met this need, left unfulfilled by 
the Rando et al apparatus, by providing both a stationary reference beam 
and a rotating reference beam defining a plane which is normal to the 
stationary beam. The apparatus of the cited application employs a beam 
diverting assembly of optical elements which intercept and split a primary 
beam into partially transmitted and partially reflected portions. The 
reflected portion of the beam is diverted to a path which extends 
generally perpendicular to the path of the transmitted beam portion. By 
rotating the beam diverting assembly, the reflected and diverted beam 
portion is rotated about an axis defined by the transmitted beam portion, 
whereby both a stationary reference beam, and a rotating reference beam, 
defining a plane normal to the stationary beam, are produced. 
For the most part, the overall performance and versatility of the 
above-described reference beam projecting apparatuses have met and even 
surpassed expectations. However, from time to time gaps in their 
capabilities are revealed when such apparatuses are tried in new 
applications not originally contemplated for them. It is, therefore, seen 
that a need exists for expansion of the capabilities of the beam 
projecting apparatus of the cross-referenced application to accommodate 
numerous other applications, such as are typically encountered in the 
surveying and construction fields. 
SUMMARY OF THE INVENTION 
The present invention provides and apparatus and method for projecting 
multiple reference beams designed to satisfy the aforementioned needs. The 
projecting apparatus comprises: means for providing a primary light beam, 
first means for receiving the primary beam and outputting first and second 
beam components thereof disposed in a generally orthogonal relationship 
with respect to one another, second means for receiving and deflecting one 
of the beam components into a generally parallel relationship with respect 
to the other beam component, and drive means for rotating one of the first 
and second means so as to rotate one of the beam components and define a 
reference plane which extends generally parallel to a reference line 
defined by the other beam component. 
More particularly, the projecting apparatus comprises: means for providing 
a primary light beam, first means for intercepting, splitting and 
deflecting the primary beam into a first transmitted beam component and a 
second relfected beam component, extending in a generally orthogonal 
relationship with respect to the first beam component, second means 
stationarily disposed in a position spaced from the first means for 
intercepting and deflecting the first beam component into a generally 
parallel relationship with respect to the second beam component, and drive 
means for rotating the first means to rotate the second beam component so 
as to define a reference plane which extends generally parallel to a 
reference line defined by the first beam component. 
Still further, the projecting apparatus comprises: a housing from which a 
laser beam projects, a beam diverting assembly disposed at the end of the 
housing for receiving the laser beam and splitting it into 
orthogonally-disposed transmitted and reflected beam components with the 
diverting assembly being mounted to the housing end for rotational 
movement with respect thereto for causing rotation of the reflected beam 
component so as to thereby define a reference plane, a pentaprism assembly 
disposed stationarily at the end of the housing outwardly of the beam 
diverting assembly for receiving the transmitted beam component therefrom 
and deflecting it to define a reference line disposed stationarily in a 
generally parallel spaced relationship to the reference plane defined by 
the rotating reflected beam component. Also, the apparatus includes a 
sighting telescope for facilitating alignment of the reference line 
defined by the transmitted beam component. 
The projecting method of the present invention comprises the steps of: 
providing a primary light beam, receiving the primary beam and outputting 
first and second beam components thereof disposed in a generally 
orthogonal relationship with respect to one another, receiving and 
deflecting one of the beam components into a generally parallel 
relationship with respect to the other beam component, and rotating one of 
the first and second beam components so as to define a reference plane 
which extends generally parallel to a reference line defined by the other 
beam component. 
More particularly, the projecting method comprises the steps of: providing 
a primary laser beam, then intercepting, splitting and deflecting the 
primary beam into transmitted and reflected beam components disposed in a 
generally orthogonal relationship with respect to one another, 
intercepting and deflecting the transmitted beam component into a 
generally parallel relationship with respect to the reflected beam 
component, and rotating the reflected beam component to thereby define a 
reference plane which extends generally parallel to a reference line 
defined by the transmitted beam component. 
Accordingly, it is an object of the present invention to provide a method 
and apparatus for projecting a stationary beam and, simultaneously, 
projecting a rotating beam such that the stationary beam defines a 
reference line and the rotating beam defines a reference plane; to provide 
the reference line and plane in spaced, parallel relationship to one 
another; to provide such parallel stationary and rotating beams from a 
common laser beam; and to provide means for facilitating aligning of the 
reference line with a desired object.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Reference is made to FIGS. 1-3 of the drawings which illustrate an 
apparatus according to the present invention, generally designated 10, for 
projecting simultaneously two reference laser beams. The projecting 
apparatus 10, except for the improvements to be described later, is 
generally similar to that disclosed in the above cross-referenced 
application, which is incorporated by reference herein. The basic 
components and arrangement of the apparatus 10 will be described to the 
extent necessary to obtain a general understanding of the apparatus so as 
to facilitate an appreciation of the improvements thereto provided by the 
present invention. A more detailed understanding of the apparatus can be 
gained by reference to the above-cited U.S. application, however. 
The laser beam projecting apparatus 10 includes a cylindrical housing 12 
which provides an enclosure for the internal components of the apparatus. 
A laser beam tube source and an arrangement of lenses and mirrors are 
mounted in a chassis (not shown) within the housing. When the housing 12 
is placed in the position shown in FIG. 1, the arrangement of lenses and 
mirrors route the reference laser beam B, generated by the laser beam 
source, along a vertical axis into a beam diverting assembly, generally 
indicated at 14. 
The laser beam diverting assembly 14 is disposed at the upper end of the 
housing toward which the laser beam is projected and includes an 
arrangement of optical elements, as shown in FIG. 2, which receive the 
laser beam B and ultimately split and deflect it into transmitted and 
reflected beam components T and R. 
More specifically, the optical elements of the assembly 14 take the form of 
a beam splitting element 16, a lower beam deflecting element 18 and an 
upper beam deflecting element 20. The elements 16-20 extend between and 
are mounted by a pair of side plates 22, being depicted in phantom outline 
in FIG. 2. The beam splitting element 16 receives the laser beam B and 
splits it into the orthogonally-disposed transmitted and reflected beam 
components T and R. The reflective properties of element 16 are such that 
the strength of component T is approximately 60% of that of primary beam 
B. 
The reflected beam component R of the laser beam is then received by the 
lower beam deflecting element 18 and reflected by a mirror surface 24 
thereon in a direction which extends generally normal to the direction of 
the primary laser beam B. The transmitted beam component T of the laser 
beam is received by the upper beam deflecting element 20. The upper 
deflecting element 20 compensates for the slight lateral shift of the beam 
component T, which is produced due to refraction in the element 16, by 
introducing a reverse shift of the beam component as it passes through the 
element 20. The transmitted beam component T then passes in the same 
direction and along the same axis as the primary laser beam B and normal 
to the direction of the outputted reflected beam component R. 
The beam diverting assembly 14 is mounted on the housing 12 for rotational 
movement by an appropriate drive means M. This causes rotation of 
reflected beam component R and thereby defines a reference plane P. A 
cylindrical rotator or holder 26 is provided to support the assembly 14 
for rotation about the vertical axis of the primary laser beam B by means 
of a motor (not shown) mounted to the chassis. Although the reflected beam 
component is rotated in the illustrated embodiment, it should be 
understood that, optionally, the transmitted beam component T could be 
rotated instead. 
The improvements of the present invention generally relate to a means for 
receiving the transmitted beam component T of the laser beam B and 
deflecting it into a generally parallel relationship with respect to the 
reflected beam component R of the laser beam, while simultaneously 
rotating the reflected beam R to define the reference plane P. Such means 
include an end cap 28 mounted on the upper end of the housing 12 and a 
pentaprism assembly 30, supported by the end cap 28, above the beam 
diverting assembly 14. 
The pentaprism assembly 30 is disposed to receive the transmitted beam 
component T from the upper beam deflecting element 20 of the beam 
diverting assembly 14 and to deflect it by 90 degrees thereby defining a 
reference line L. Line L is disposed stationarily in a generally parallel 
and spaced relationship to the reference plane P defined by the rotating 
reflected beam component R. 
The end cap 28 includes a side window 32 with a glass roundel 33 fixed 
therein through which the transmitted beam component T passes after being 
deflected by the pentaprism assembly 30. The cap 28, preferably made of 
aluminum, is mounted to the upper end of the housing 12 by an annular ring 
34, which can also be constructed from aluminum. Ring 34 has a downwardly 
and inwardly tapering outer surface 36. The ring 34 is fixed to the 
housing by a plurality of screws 38, and the cap 28 is attached to the 
tapered surface 36 of the ring 34 by a plurality of screws 40, such as 
three nylon tip set screws disposed 120 degrees apart. Due to the tapered 
surface 36, cap 28 is firmly seated on phenolic washer 41. 
The pentaprism assembly 30 mounted to the end cap 28 includes a pair of 
reflecting surfaces which are accurately aligned for deflecting the 
transmitted beam component T into a direction generally parallel to the 
reference plane P. The assembly 30 includes a frame 42 formed by a pair of 
upstanding sidewalls 44 (only one shown) which mount an upper mirror 46 by 
a support bracket 48, and a lower mirror 50 by a support bracket 52. The 
mirrors 46 and 50 are precisely arranged to each reflect the transmitted 
beam T at a nominal forty-five degree included angle so that the beam 
ultimately emerges from the pentaprism assembly 30 at 90 degrees from the 
vertical axis of the beam component T as it enters the assembly. 
Finally, a sighting telescope 54 is attached by screw 56 and bracket 58 to 
the top 60 of the cap 28. The telescope 54 is set in alignment with the 
outputted transmitted beam component T which defines the reference line L, 
and thus can be used for aligning the beam component T. 
By the present invention, a primary laser beam B is split into two beams, a 
stationary beam component T which defines a reference line L and a moving 
or rotating beam component R which rotates about the axis of the laser 
beam B to define a reference plane P substantially normal thereto and 
substantially parallel to the reference line L. Further, the end cap 28, 
which mounts the pentaprism assembly 30 that produces the reference line 
L, can readily be removed from the upper end of the housing 12 by 
loosening the set screws 40. Thus, the apparatus 10 can be easily 
converted to the configuration disclosed in the cross-referenced 
application, wherein the transmitted beam component defines a reference 
line extending generally normal to the rotating reference plane. 
The apparatus of the present invention may be used in any of a number of 
construction applications. The dual beams produced may, for example, be 
used as references in conjunction with equipment which is performing a 
trenching operation. The stationary beam is used as a reference laterally, 
while the rotating beam is used as a reference to ensure that the trench 
has the desired depth. 
Having thus described the multiple reference laser beam apparatus of the 
present invention in detail and by reference to a preferred embodiment 
thereof, it will be apparent that modifications and variations are 
possible without departing from the scope of the invention defined in the 
appended claims.