Device for projecting a flat beam of diverging laser rays

A device for projecting a flat beam of diverging laser rays comprises a base supporting a movable gravity self-leveling equipment and at least a laser beam or ray projector mounted thereon and provided with an optical lens assembly for transforming the laser beam emitted by the projector into a flat beam of diverging laser rays and laying in a horizontal or vertical plane for projecting at least a straight line laying on a perfectly horizontal or vertical plane.

BACKGROUND OF THE INVENTION 
The present invention relates to a projector device for projecting one or 
more diverging laser ray flat beams of a gravity self-leveling type for 
forming one or more horizontal and/or vertical lines on bodies such as 
walls or the like. 
Devices for projecting laser rays or beams on bodies, such as walls, in 
which the laser beam projector is mounted on a gravity self-leveling 
movable equipment, so that the emitted laser beam, under an equilibrium 
condition of the movable equipment or assembly, is arranged in a perfectly 
horizontal plane, or along a vertical straight line are already known. 
These prior art devices are conventionally designed for projecting, on a 
wall, a single light point, obtained by the interference of the emitted 
laser beam, against said wall. 
A further class of devices of the above mentioned type, which are at 
present commercially available, provides for rotating a horizontal ray or 
beam about a vertical axis, by means of a rotor applied to a prism or 
penta-prism, which offsets through 90.degree. the vertical laser beam 
emitted by a laser diode. 
However, the latter devices are not of a self-leveling type, since the 
vertical arrangement of the main beam emitted by the beam generator is 
obtained by adjusting screws provided for locating the instrument with 
reference to suitable precision horizontal or vertical vials included 
therein, or they are self-leveling only within a small fraction of degrees 
(for example .+-.5.degree.), and, in the latter devices is always 
necessary to perform a rather accurate manual pre-leveling operation in 
order to bring the instrument within the self-leveling action field. 
A high speed rotation of the laser beam will involve a generation of a 
plane through 360.degree. and, accordingly, of a horizontal or vertical 
straight line by an interference of the mentioned plane with a body such 
as a wall. 
The wavelength of the rotary laser beam can be included either in the 
visible or in the not visible field: in the latter case, the straight line 
is defined by a receptor which is sensitive to a variation of the light 
power impacting thereon, and which is designed so as to signal either in a 
luminous manner or in an acoustic manner, as the plane generated by the 
rotary beam is parallel to or coincides with a fixed segment marked on the 
receptor. 
A third class of devices, which are also at present commercially available, 
provides for projecting a pulsating and not visible vertical laser ray or 
beam, emitted by a vertically arranged laser diode which, by impinging on 
a mirror like surface cone suspended under the gravity effect, will 
diffuse through 360.degree. a plane of not visible laser beams or rays, 
pulsating and horizontally arranged, which are picked-up by a sensitive 
receptor of the above mentioned type. 
Even in this case, the self-leveling property is limited to a small degree 
fraction; moreover, the laser beam is not visible and, accordingly, it is 
always necessary to provide a detecting receptor. 
On the other hand, the use of a visible beam, in addition to being of a 
less immediate exploitation, is frequently less practical, since it, for 
example, does not allow to perform instantaneous verifications of the 
leveling arrangement of points not accessible from the operator (this, for 
example, is the case of a leveling of several points, some of which are 
arranged beyond a not accessible gate), what, on the contrary, is always 
possible by using visible beams or rays. 
A drawback of this type of devices is the requirement of performing a 
pre-leveling operation, and the impossibility of simultaneously projecting 
several laser light planes, so as to provide on the impacted wall one or 
more perfectly horizontal straight lines, and/or straight lines suitable 
to be oriented depending on requirements. 
At the state of the art, it is not already available an optimum apparatus, 
i.e. a truly self-leveling device, which does not require any preliminary 
calibration, and which is suitable to simultaneously project, through the 
overall 360.degree. range, full planes of visible continuous and 
nonmovable horizontal and vertical laser beams so as to provide a 
plurality of optical tracing and/or squaring straight lines, in order to 
obviate the need of tracing conventional lines by pens or chalks. 
The above mentioned prior solutions, of only partially self-leveling 
devices with horizontal rotary laser beams which, tilted through 
90.degree., provide vertical planes, or of devices, them too partially 
self-leveling, using not visible laser beams horizontally diffused through 
360.degree. by a cone, constitute valid but partial answers to the above 
mentioned problem. 
SUMMARY OF THE INVENTION 
The aim of the present invention is to fully solve the above mentioned 
problem, so as to provide the possibility of projecting, in a very 
accurate and simple manner, flat beams of visible and continuous 
sufficiently diverging laser rays (in the range, for example, of 
90.degree.-100.degree.), either horizontal or vertical or, simultaneously 
both, in order to cover a broad sector of the 360.degree. angle, emitted 
by a truly self-leveling device provided for operating by gravity and not 
requiring any pre-calibration even on a slanted plane, and which, 
moreover, is turnable, either manually or automatically, about a vertical 
axis so as to orient the projected flat beam sector according to any 
directions. 
Such a solution will allow to instantaneously and simultaneously project 
horizontal and vertical luminous straight lines, having a length which 
varies according to the distance of the device from the targeted wall. 
The laser sources are small power laser diodes, so as to fit the vision 
safety rules or requirements (class 2 of the European Norm EN 60825, that 
is: wavelength range 400-700 nm and output power up to 1 mW for CW 
lasers), in a small size and weight portable instrument. 
The device, only for particular applications (for example outdoor and with 
bright light, or along great distances, where the visible beam tends to 
become invisible to a human eye even if aided by suitable eye glasses) is 
provided to use visible pulsating beams or rays (or even not visible 
beams) which emitted by the laser diode will generate, in an equilibrium 
condition, flat and pulsating beams of horizontal and/or vertical 
diverging rays for being intercepted by a receptor apt for detecting the 
above mentioned type of beams. 
Within the scope of the above mentioned aim, a main object of the present 
invention is to provide such a device which allows to orient through the 
space, depending on requirements, one or more suitably diverging flat ray 
beams, in a vertical and/or horizontal plane. 
Another object of the present invention is to provide a truly self-leveling 
device, i.e. a device able of operating without any pre-calibration 
operation, by simply arranging it on an approximately horizontal surface 
(for example .+-.10.degree.) and which can be operated by a single 
operator, even unskilled, to project perfect horizontal and/or vertical 
straight lines, independently from the arrangement of the device bearing 
surface. 
The above mentioned aim and objects and further objects, which will become 
more apparent hereinafter, are achieved by a projector device for 
projecting one or more diverging laser ray flat beams of a gravity 
self-leveling type for forming one or more horizontal and/or vertical 
lines on bodies such as walls or the like, characterized in that said 
device comprises a construction including a base supporting a movable 
gravity self-leveling equipment, and at least a laser beam projector 
mounted on said movable equipment and provided with an optical lens or 
assembly for transforming the laser beam emitted by said projector into a 
flat beam of diverging laser rays and laying in a horizontal or vertical 
plane for projecting at least a straight line laying on a perfectly 
horizontal or vertical plane.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
With reference to the reference numbers of the above mentioned figures, the 
device according to the present invention comprises a supporting 
construction, including a supporting base, constituted by a base 1 
provided with bearing feet 2, which can be constituted by screws engaging 
with threaded recesses defined in said base 1 and which can be 
advantageously registered or adjusted in height, so as to allow the device 
to be suitably arranged on a bearing surface, to project the ray beam at a 
desired level. 
From the base 1 extends a top portion 3 having a substantially tubular 
construction, and supported by the mentioned base 1, through the 
interposition of a bearing 4, so as to rotatably turn about a vertical 
axis 5. 
Thus, the top portion 3 can be turned, with respect to said base 1, about 
the mentioned vertical axis 5, said top portion 3 being moreover provided, 
near the bottom portion thereof, with a plurality of notches 6 which can 
be marked by an index 7, or mark, defined on the top face of the base 1, 
so that the rotation of the top portion 3, about the axis 5, can be 
carried out in a very accurate and controlled manner. 
Inside the top portion 3 it is supported a self-leveling movable equipment 
8, which can swing, with respect to said top portion 3, about two 
horizontal axes 9 and 10, substantially mutually coplanar and 
perpendicular, and preferably crossing at the axis 5. 
More specifically, the movable equipment 8 is mounted on a pin 11, whose 
axis coincides with the axis 10 which is ratably supported about the 
mentioned axis, through the interposition of bearings 12, by a small block 
13 which, in turn, is supported, through the interposition of bearings 14 
and 15, by a pair of pins 16a and 16b affixed to the top portion 3 and 
having axes which coincide with the axis 9. 
The movable equipment 8 is moreover provided, near the bottom end portion 
thereof, with a threaded recess 17, the axis of which is substantially 
horizontal, and in which is engaged a dowel which can be displaced by 
screwing it on or off inside said threaded recess 17. The dowel 18 
constitutes a mass whose position, inside the threaded recess 17, allows 
to change the position of the center of mass of the movable equipment 8. 
The device according to the present invention is moreover provided with a 
damping device for damping the self-leveling swinging movement of the 
movable equipment 8. 
This damping device comprises a lever 19 which is articulated on the top 
portion 3 about an axis 19a preferably crossing the vertical axis 5. 
The lever 19, about said axis 19a, is provided with an eccentric portion 20 
suitable to operate, through a smaller lever 21, against the bottom end 
portion of the movable equipment 8 for cushioning or damping the swinging 
movement thereof. 
As shown, the lever 19 projects from an opening 22 defined through the side 
surface of the top portion 3, and being held in a rest condition by a 
small spring 24. 
As it is specifically shown in FIG. 1, at least a projector 25 is arranged 
on the movable equipment 8, said projector 25 is suitable to emit a laser 
beam or ray and is provided with an optical assembly or lens 26 for 
transforming the emitted laser beam or ray into a flat beam 30 of 
diverging laser rays laying on a same horizontal plane. 
At present, the emission or projection of a flat beam of diverging laser 
rays laying in a single plane, for example of the visible type, is 
obtained by specifically designed optical assemblies which, however, do 
not provide for a projected perfectly rectilinear line, for example on a 
wall. Moreover said line does not have an even thickness (of amplitude in 
the cross direction) for the overall length thereof. 
The present invention, owing to specifically designed constructional 
features, provides on the contrary for a visible laser line devoid of the 
above mentioned defects, so that the obtained line is laying fully and 
effectively on a single plane and is having, moreover, an even thickness 
through the overall length thereof. 
With reference, for simplicity, to visible rays, without excluding not 
visible laser rays, and with reference to FIGS. 20,21 and 22 the device 
according to the present invention comprises, a laser bearing bushing 206 
on which is mounted a cylindrical lens bearing bushing 204 provided with 
position affixing dowels 205 which supports a half-cylindrical lens 207 
set at a proper position by setting dowels 209 and fixed by dowels 208. 
The bushing 206 contains the body 203, therein half-spherical lens 202 
rigidly held in its position by the ring nut 210 is housed, whereas the 
laser diode assembly 201, locked by the threaded ring nut 215, is aligned 
with said body 203. 
The laser diode 201 will emit, as it is known, a laser beam having an 
elliptical cross-section whose rays are not collimated, that is they are 
not parallel but greatly and progressively diverging as the distance from 
the source thereof is increased. As these rays must be collimated, they 
are caused to pass through a suitable half spherical lens whose property 
is to collect them and making them parallel. In the case in consideration, 
the laser beam 216 will impact on the hemispherical lens 202 which is 
arranged at a properly set distance from the laser source, so that said 
lens collects all the emitted light, whereby the output collimated rays 
beam fully preserves the elliptical cross section of the laser source. 
The collimated beam 211 will successively impact against the 
half-cylindrical lens 207 which will transform the collimated laser beam 
211 into a flat beam. 
In order to give the collimated beam an even thickness, the plane of the 
elliptical cross section collimated laser beam 211, on which lays the 
minor axis 212 must contain the geometrical axis 213 of the 
half-cylindrical lens 207. In order to obtain this, the laser bearing 
bushing 206 is turned in the lens bearing bushing 204 so as to provide the 
desired alignment, thereupon the assembly is locked in its desired 
position by means of the screws 205. 
The so obtained flat beam will be perfectly rectilinear, i.e. it will lay 
on a single plane only if the geometrical axis 213 of the half-cylindrical 
lens 207 is effectively perfectly perpendicular to the central axis 217 of 
the elliptical cross section of the collimated laser beam 211. This 
condition is obtained by adjusting the half-cylindrical lens 207 by the 
screws 209 whereas the screws 208 hold said lens. 
The above disclosed adjustment operations will be performed at the factory 
by means of a suitable equipment and, when properly performed, a visible 
laser line of even thickness and laying on a same plane can be obtained by 
projection, for example on a front wall. 
The above disclosed device is substantially a novel independent optical 
assembly which further comprises a control panel 214 for the laser diode 
201, supplied by batteries or any other suitable power supply source. 
The optical assembly, upon suitable calibration, is usable in any desired 
position for providing, for example, a visible vertical or horizontal 
straight line. 
The most useful and frequent use is, however, to apply the device to the 
self-leveling swinging element of a horizontal plane leveling apparatus, 
preferably of a rotary type. 
Such an apparatus is normally used for projecting a single self-leveled 
horizontal visible laser beam, for example on a wall, therefore it can be 
seen a bright point, displaceable in several directions by turning the 
apparatus, while preserving its position on the same horizontal plane. 
By using the device of the present invention, after being calibrated it is 
possible to project, for example on a vertical wall, a visible laser ray 
line of a comparatively great length and of even thickness entirely 
positioned on a single horizontal plane. 
Thus, the advantage of obtaining a line instead of a single point, which 
requires a lot of subsequent angular displacements of the point emitting 
apparatus for localizing several points laying all on the same plane is 
evident, whereas the line owing to its length will immediately localize a 
lot of points positioned on the same plane. 
Moreover, by turning the apparatus a self-leveled line is always obtained, 
independently from the projection direction thereof. 
An additional application of the device according to the present invention 
and related to the subject pivot laser, provides its mounting for the 
projection of the laser line in a perfect vertical orientation under any 
conditions: thus by turning the subject device it is possible to draw 
different vertical planes in different directions. 
Moreover, it is, also, possible to arrange on the swinging assembly two 
optical devices in the same apparatus, one over the other and parallel to 
one another but with axes turned through 90.degree., so as to provide two 
diverging ray flat beams perpendicularly crossing one another. 
The above disclosed solutions are related to either continuous or pulsating 
visible or not visible laser rays or beams. 
The projector 25 and optical assembly or lens 26 are mounted in a sleeve 29 
adjustably supported about the axis thereof which coincides with the 
emitted laser ray, inside a small block 27. 
The adjustment of the position of the projector 25 and related optical 
assembly or lens 26, is performed by a pair of screws 28a and 28b. 
The projector 25 can be constituted, for example, by a laser diode of a 
sufficient power having a collimated output beam, supplied by batteries 
arranged in the body 3 or by a rectifier connected to the mains voltage, 
whereas the beam can be emitted, according to the requirements, either in 
a continuous or a pulsating way or having a wavelength within the visible, 
or the not visible radiation range. 
Owing to the self-leveling effect of the movable equipment 8, it is not 
necessary in order to project a diverging ray beam on a perfectly 
horizontal plane, that the plane on which is arranged the device is a 
perfectly horizontal plane, but it can also be slanted with an inclination 
in the range of plus or minus 10.degree., or greater, the arrangement 
depending exclusively on the width or size of the inner diameter of the 
body 3, i.e. on the room available for the movable equipment in order to 
be set in the equilibrium positions, without touching the inner wall of 
the body 3. 
In order to allow the diverging laser ray flat beam to lay, in condition of 
equilibrium, on a perfectly horizontal plane, the two adjusting 
possibilities provided by the dowel 18 and the screws 28a and 28b are 
applied during the assembly operation. 
More specifically, the two screws 28a and 28b, cause the sleeve 29 to turn 
about its rotary axis so that the generated diverging laser ray flat beam 
30 does not cross the horizon or any horizontal reference lines. 
The horizontal arrangement of the diverging laser ray flat beam is obtained 
by sliding the dowel 18, which, by its mass, will cause the movable 
equipment 8 to obtain the desired position. 
As is clearly shown in FIG. 5, the projector 25 can be oriented inside the 
small block 27 so as to emit a diverging laser rays beam 31, the rays of 
which will lay in a vertical plane. 
In this case, in order to obtain a perfectly vertical ray beam 31, it is 
necessary only a single adjustment operation, during the assembling stage, 
which is performed by operating on the screws 28a and 28b, so as to cause 
the sleeve 29 to turn about the rotary axis thereof, so as to provide, 
under a rest condition of the movable equipment 8, a projection of a ray 
beam on a perfectly vertical plane, even when the top portion 3 is turned 
about the axis 5. 
According to the different embodiment shown in FIG. 7, the laser beam or 
ray projector 25, and its related optical assembly or lens 26, can also be 
arranged at the top end portion of the movable equipment 8, so as to 
provide a laser ray beam 32 laying on a vertical plane. 
This vertical plane can be anyhow suitably oriented, by turning the top 
portion 3 about the axis 5. 
Likewise, the orientation of the horizontal and vertical ray beam, as shown 
in FIGS. 1 and 5, can be changed by means of the rotation of the top 
portion 3 about the axis 5. 
According to the modified embodiment shown in FIG. 9, on the movable 
equipment 8 can also be mounted two projectors 41 and 42, provided with 
the related optical lenses or assemblies, so as to project two diverging 
ray beams, which respectively lay on a vertical plane and on a horizontal 
plane, thereby projecting, on a wall spaced apart from the device, a 
perfectly vertical straight line and a perfectly horizontal straight line 
which intersect mutually as a cross. 
The arrangement of the projectors 41 and 42 and related lens assemblies can 
be calibrated, during the assembling stage of the projectors on the 
movable equipment 8, so as to provide perfectly horizontal and vertical 
ray beams. 
More specifically, by operating the projector 42 adjusting screws 28a and 
28b, the beam 34 is so oriented as not to cross the horizontal line, or 
any reference horizontal lines. The horizontal arrangement of the beam 34 
is obtained by suitably arranging the adjustment dowel 19. 
In order to make the projector 41 to generate a beam 33 laying on a 
vertical plane, it is sufficient to adjust the pair of screws 28a and 28b 
of said projector 41 so as to cause the beam 33 to pass through a plumb 
line. 
The particular arrangement of the projectors 41 and 42 will allow to 
project on a wall, by using equal power laser emitters, a cross having 
substantially arms of the same length. 
The two diverging ray beams, respectively horizontal and vertical, can also 
be generated by two mutually independent emitters, or, as is clearly shown 
in FIG. 11, they can be generated by a single emitter 50 emitting a laser 
ray 41 which, by an optical assembly constituted for example by a 
semireflecting mirror or prism, or pentaprism 52, will be split into two 
rays 53 and 54. As shown, along the path of the ray 54 is provided a 
further prism or pentaprism, or reflecting mirror 55, for deflecting the 
ray 54 so as to make it preferably parallel to the ray 53. 
Along the path of the rays 53 and 54 are moreover provided optical 
assemblies or lenses 55 and 56 for transforming respectively the rays 53 
and 54 into a vertical beam 57 of diverging flat laser rays and into a 
horizontal beam 58 of diverging flat laser rays, corresponding to the 
beams 33 and 34. 
As clearly shown in FIG. 13, it is also possible to provide three 
projectors 61, 62, 63 with related optical assemblies or lenses, so as to 
respectively project a horizontal beam 64 of diverging laser rays, a beam 
65 of diverging laser rays laying on a vertical plane and perpendicularly 
crossing the beam 64 of laser rays emitted by the projector 61, as well as 
a third beam 66 of laser rays also laying on a vertical plane but emitted 
on the top of the device. 
Even in this case, the projectors and associated optical assemblies can be 
constituted by mutually independent emitters or, as shown in particular in 
FIG. 16, a single emitter 7G can be provided for emitting a laser ray 71, 
which, by means of an optical system constituted for example by a 
semi-reflecting mirror 72, or prism, or pentaprism, is split into three 
rays respectively indicated at 73, 74e and 75. 
On the path of the ray 74 is, moreover, provided a reflecting mirror 76 or 
prism, or pentaprism, which deflects the ray 74, so as to bring it to a 
position substantially parallel to the ray 73. 
Along the path of the so deflected ray 74, as well as along the path of the 
ray 73, there are arranged respective optical assemblies 77 and 78 which 
generate laser ray beams, respectively laying on a vertical and on a 
horizontal plane, and mutually cross-like intersecting. 
Along the p at h of the beam 75, is further provided an additional optical 
assembly 79, or lens, which generates a flat beam of diverging laser rays 
laying on a substantially vertical plane. 
Even in this case, the optical assemblies 77, 78, 79 can be calibrated, in 
a rotary manner and about their respective axes, by means of calibrating 
or adjustment screws, in an analogous manner to the above disclosure. 
As laser ray or beam emitters having a wave length within the not visible 
radiation range are used, there is provided on the wall or the surface, 
thereon the diverging laser rays or beams are impacted, a suitably 
receiver of the type shown in FIG. 19, sensitive to the variations of the 
light power impacting on it, and capable of signaling either in an 
acoustic or in a luminous manner when the intercepted diverging ray flat 
beam is parallel to or coincides with a fixed preset line on said 
receiver. 
In this case, the not visible laser rays emitted must be of a pulsating 
nature. 
Such a pulsation can be generated, for example, by an electronic circuit 
connected between the laser diode LD and the power supply as it is shown 
in the diagram of FIG. 18. 
This diagram comprises: an electric power supply 100 (bias level) for the 
control and energizing system of the laser diode LD, a reference circuit 
101 (bias calibration) for controlling the power to be applied to the 
laser diode LD, a circuit 102 (oscillator) for generating a square wave 
carrier frequency, and a circuit 103 (modulator) for generating code 
pulses on the carrier frequency (square wave pulse bursts). 
The oscillator 102 and modulator 103 drive an electric switch 104 (writer) 
for power supplying the laser diode LD. The switch 104, in particular, is 
supplied by a control knot of the feedback type 105 for the current to be 
supplied to the laser diode LD through the writer 104, depending on the 
power supply voltage and on the reference electric parameters and the 
light power emitted by the laser diode LD. 
The feedback arrangement 105 is coupled at the input to the bias level 100, 
to the bias calibration 101 and to a feedback amplifier 106, constituted 
by a detection circuit for detecting the light power of the laser diode LD 
by a photodiode PD generating an electric signal depending on the light 
emitted by the laser diode LD, and at the output to the writer 104. 
The writer 104 supplies the laser diode LD through an LD output driver 107, 
which is a typical circuit for igniting the laser diode LD. 
The receiver shown in FIG. 19 comprises a supporting plate 108, provided 
laterally with reference notches 109 at a preset reference line 110 
arranged at the center of the two sensor assemblies 111 and 112. The 
receiver further comprises a sound emitting device 113 or a light emitting 
device 116 for emitting either an acoustic signal or a light signal 
actuated as the laser beam impacts simultaneously and with the same 
intensity the sensor 111 and 112, thereby providing a continuous sound 
and/or the energizing of sensor 116. 
If, on the contrary, the laser beam impacts with a greater intensity one of 
the two sensor assemblies 111 or 112, then the acoustic signal will be an 
intermittent signal and the light signal will be energized exclusively in 
the sensor 114 or 115, respectively. 
The possibility of interposing between the laser diode and the power supply 
source thereof an electronic circuit suitable to transform, if desired 
through a switch, flat beams of visible laser rays from continuous to 
pulsating, allows the device to meet all of the possible use requirements, 
since it can operate both in an inside environment as a self-leveling 
projector of continuous horizontal and vertical segments (i.e. visible for 
the human eye) and an outside environment where the sensitive receiver 
will allow to localize the pulsating planes of horizontal and vertical 
laser rays which are not visible for the human eye. 
In the embodiments using several laser ray emitters, such as, for example, 
the embodiment shown in FIGS. 9 and 13, it is possible to provide for 
several switches for switching off one or more of said emitters as their 
use is no longer required. 
For completeness of description it is underlined that the elements which 
are shared in the several above discussed embodiments have been 
referenced, in the drawing figures, by the same reference number. 
From the above disclosure and from observations of the figures of the 
accompanying drawings, it should be apparent that the invention fully 
achieves the intended aim and objects. 
Moreover, it should be pointed out that a fully range of 360.degree. of 
rotation self-leveling device has been provided, which allows to project 
one or more flat beams, of diverging laser rays, visible or not visible, 
either continuous or pulsating, laying on a horizontal plane and/or on a 
vertical plane, with the possibility of changing the orientation of said 
ray beams about a vertical axis, thereby allowing a single operator, even 
unskilled, to perform, in a simple and quick manner, a tracing of 
perfectly and even simultaneous horizontal and/or vertical reference 
segments, possibly crossing perpendicularly on a wall, or on a surface on 
which said beams are projected and without the need of providing a 
perfectly horizontal bearing surface and of the rotation of said laser 
beam about a vertical or horizontal axis, but simply providing a 
horizontal and/or vertical diverging flat laser beam which, depending on 
requirements, can be continuous and visible (particularly suitable in an 
indoor environment) or pulsating, either visible or not visible (suitable 
in an outdoor environment or for great distances) by using a sensitive 
suitable receiver. 
While the invention has been disclosed and illustrated with reference to 
preferred embodiments, it should be apparent that such disclosed 
embodiments are susceptible to several modifications and variations, all 
of which will come within the spirit and scope of the invention, as 
defined in the accompanying claims.