Note: Descriptions are shown in the official language in which they were submitted.
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FIELD OF INVENTION
The invention relates to a laser arrangement for a multi-beam
laser sighting mechanism, which comprises a light source for producing at
least one primary laser beam bundle and an optical beam divider with
reflecting surfaces for splitting at least one primary laser beam bundle into
at
least two partial beam bundles.
BACKGROUND OF THE INVENTION
In the building industry, the long-known mechanical devices,
which make alignment and measurement of the positional accuracy of
building components, assemblies, installations and the like possible, are
increasingly being replaced by optical devices, which are based on a high
intensity collimated bundle of light rays. Since the semiconductor makes
large numbers of laser diodes available with radiation in the visible
spectrum,
usually in the red region of the spectrum, a series of measuring devices has
become known in the building industry, which replace the previously
dominating mechanical, visual devices and methods and, moreover, also
additionally offer new measurement possibilities. For example, sighting
mechanisms, which send out at least one collimated laser beam bundle,
which has a diameter of not more than 10 mm at a distance of 20 m and a
deviation of about 1 mm/10m in the horizontal direction have gained much
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acceptance. The laser beam bundle is usually aligned automatically in the
horizontal direction by gravity-affected constructions or control circuits.
Aside from the horizontal alignment and leveling, there is
frequently also the need to provide a plumb bob or to mark off a precise right
angle. For this purpose, for example, US patent no. 5,144,482 discloses a
laser device, which emits three laser beam bundles, which lie in a horizontal
plane and extend at right angles to one another. Additionally, the device
emits two plumb bob beams. An arrangement of mirrors is provided within the
io device to produce the horizontal and perpendicular laser beam bundles. This
arrangement of mirrors deflects the primary laser beam bundle, originating
from a laser diode, in the desired directions. The deflecting mirrors, for
producing the total of five horizontal and vertical beam bundles, are disposed
at a spatial distance from one another in the beam path of the primary laser
beam bundle.
Consequently, a zero offset results for the three-dimensional
coordinate system, put up by the emitting laser beam bundles, because the
perpendicular beam bundles and the horizontal beam bundles have different
20 virtual origins. Until now, the manufacturers of such laser beam devices ,
made do by providing a round gauge of, for example, 20 mm for this zero
offset. For measurements with such laser devices, the zero offset must
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always be taken into consideration. In use, this represents a considerable
source of errors. Due to the splitting of the primary laser beam bundle,
coming from the light source, the intensity, remaining for the individual
partial
beam bundles, is greatly reduced. Admittedly, an attempt is made to provide
a remedy for this disadvantage by using a laser light source of appropriately
high output. This solution is hardly economically feasible, since the costs of
laser diodes increase disproportionately to the power emitted. It is sometimes
also desirable to produce partial beams in different colors. This, however, is
not possible with conventional commercial equipment.
BRIEF SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide
economically feasible and practical solutions to these disadvantages of laser
sighting mechanisms of prior art. The laser arrangement for a multi-beam
laser sighting mechanism in accordance with the present invention indicates
an optical system of coordinates, for which a zero offset is avoided. At the
same time, this arrangement produces partial beam bundles having a
sufficient intensity, so that even readings over larger distances are
possible.
This arrangement also produces partial beam bundles with different colors,
without having to put up with losses in light intensity.
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These objectives are accomplished by a laser arrangement for a multi-
beam laser sighting mechanism, in accordance with the present invention.
The inventive laser arrangement is constructed for use in a multi-beam laser
sighting mechanism, which comprises a light source for producing at least
one primary laser beam bundle and an optical beam divider with reflecting
surfaces, by means of which the at least one primary laser beam bundle can
be split into at least two partial beam bundles extending at right angles to
one
another. Pursuant to the invention, the light source comprises two
semiconductor lasers, the light-emitting surfaces of which have a length
extent and a transverse extent in a ratio of about 2.5 : 1 to about 4: 1. The
semiconductor lasers are disposed with their light-emitting surfaces such that
the longitudinal dimensions of the light-emitting surfaces are rotated at an
angle of 900 to one another and the primary beam bundles, produced by the
two semiconductor lasers, can be superimposed at a position before or at the
beam divider.
A laser beam, emitted from a semiconductor laser, has an
elliptical beam geometry, which is a consequence of the rectangular shape of
the light-emitting surface of the layer of the semiconductor laser, producing
the laser light. Due to the arrangement of the semiconductor laser that has
been selected, with light-emitting surfaces rotated at an angle of 90 to one
another, the total laser beam bundle of the two superimposed elliptical
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primary beam bundles has essentially a star-shape, which results from the
two ellipses rotated at an angle of 900 to one another. As a result, the total
beam bundle has an essentially symmetrical shape, which meets the
geometric requirements of the beam divider. By superimposing the primary
beam bundles of two semiconductor lasers, semiconductor lasers with low
powers can also be used as a light source to produce a sufficiently high light
intensity. Failure of one of the semiconductor lasers does not result in the
total failure of the laser sighting mechanism; instead, it can still be used
to a
limited extent. As a result, the economic efficiency and the availability of
the
laser sighting mechanism are further improved. Semiconductor lasers with
different outputs and different wavelengths can also be used as light sources.
As a result, interesting possibilities arise for varying the laser sighting
mechanism with respect to the laser beams emitted. In the case of a three-
dimensional laser sighting mechanism, for example, the at least three laser
beams, setting up the Cartesian coordinate system, can have different colors.
The user, therefore, can also get his bearings by relying on the color of the
projected marking.
To further improve the beam geometry and to improve the
adaptation to the requirements of the beam divider, one or more beam-
forming elements can be disposed at least between one of the semiconductor
lasers and the beam divider.
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In one embodiment of the laser arrangement, the light-emitting
surfaces of the semiconductor lasers are disposed perpendicularly to one
another. The two emitting primary beam bundles are directed onto a
semitransparent mirror, which is disposed between the semiconductor lasers
and the beam divider and inclined at an angle of 45 to the direction of
dispersion of the two primary beams and superimposed there into a total
primary beam bundle. The selected arrangement is easily implemented and,
aside from a semitransparent mirror, does not require any further optical
elements of special construction. For the arrangement of the two
semiconductor lasers selected, the beam divider has at least two and
preferably four reflecting surfaces. The reflecting surfaces are at right
angles
to one another and disposed at the same distance from the semitransparent
mirror. In each case, they are inclined at an angle of 45 to the incident
total
primary beam bundle and protrude into the total beam bundle, such that a
beam passage is formed for a portion of the total primary beam bundle. Due
to the arrangement of the reflecting surfaces in the beam path of the primary
light beam bundle, three partial beam bundles, extending perpendicularly to
one another, can be easily produced. For example, the partial beam bundles,
produced by the reflecting surfaces of the beam divider, form the orthogonal y
and z axes. The portion of the total primary beam bundle, which is
transmitted without hindrance, forms the x axis. For an arrangement of four
reflecting surfaces, the total primary beam bundle is divided into a total of
five
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partial beam bundles. In this way, "negative" sections of the y and z axes can
also be produced. The Cartesian coordinate system of partial beam bundles,
so produced, has a common virtual origin, which arises from the intersection
of the extension of the partial beam bundles through the "points of incidence"
of the total primary beam bundle on the reflecting surfaces. The portion of
the
total primary beam bundle, transmitted without hindrance, also strikes this
point of intersection. By these means, a zero offset is avoided. The
arrangement of the reflecting surfaces provides the prerequisite for a compact
and robust construction of the optical element. This facilitates the mounting
in
the laser device and reduces the susceptibility of the beam divider to
jarring.
In an alternative embodiment of the laser device for a laser
sighting mechanism, the light-emitting surfaces of the semiconductor laser are
disposed at an acute angle to one another. The beam divider has at least two
and preferably four reflecting surfaces, which are at the same distance from
the assigned semiconductor laser. Pairs of these surfaces, each enclose an
angle of 900 with one another. The reflecting pair of surfaces is disposed at
an angle of 45 to the incident primary beam bundle. In this embodiment, the
semitransparent mirror is omitted. The light-emitting surfaces of the two
semiconductor lasers are oriented towards the reflecting surfaces of the beam
divider and, only at the beam divider, are superimposed to form a total beam
bundle.
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In a further alternative embodiment of the inventive laser
arrangement, the light-emitting surfaces of the semiconductor lasers are
aligned parallel to one another. The beam divider is formed by two prisms,
which have longitudinal axes extending perpendicular to one another and are
disposed with their two prism surfaces at an angle of 45 to the respective,
assigned primary beam bundle. That prism, one of two plane parallel side
surfaces of which is disposed in the vicinity of one of the prism surfaces of
the
second prism, has optically polished side surfaces. In this embodiment, the
beam divider consists of two simple prisms, the reflecting prism surfaces of
which enclose an angle of 900 at the prism edge facing the semiconductor
laser. The prism, through which a deflected partial beam bundle must pass
without being refracted, has optically polished, parallel side surfaces and a
passage, extending from the edge of the prism to the base surface, for a
middle region of the incident primary beam bundle. The manufacture of the
prisms is simple and economically cost-effective. They are mounted and
aligned relatively easily in the laser equipment. The prisms are robust and
largely insensitive to shock.
For manufacturing reasons and to improve the robustness of the
construction, the reflecting surfaces of the beam divider are combined with
one another into a structural unit. For example, the two prisms can be
assembled into a matched unit. In a particularly advantageous variation, the
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reflecting surfaces of the beam divider are constructed at a monolithic
component. The component may, for example, have the configuration of a
truncated pyramid, the surfaces of the pyramid extending at an angle of 900
to one another and at an angle of, for example, 45 to the perpendicular.
IN THE DRAWINGS
For a more complete understanding of the present invention, and
the advantages thereof, reference is now made to the following descriptions
taken in conjunction with the accompanying drawings, in which:
FIG 1 illustrates a conventional semiconductor laser;
FIG 2 illustrates an embodiment of a laser arrangement of the
present invention;
FIG 3 illustrates a cross section of the course of the total primary
beam G at the site of the superimposition 6 of FIG 2, in
accordance with the present invention,
FIG 4 illustrates an alternative embodiment of a laser
arrangement of the present invention; and
FIG 5 illustrates a further alternative embodiment of a laser
arrangement of the present invention.
DESCRIPTION OF A SPECIFIC EMBODIMENT
Figure 1 shows a conventional commercial semiconductor
laser S, which has a layered construction. In particular, an active layer A is
disposed between two reflecting layers R, at which total reflection takes
place.
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The light-emitting surface of the semiconductor laser S is labeled E. The
light-emitting surface E has a rectangular shape with a longitudinal extent I
and a transverse extent w. The ratio of the longitudinal extent I to the
transverse extent w of the light-emitting surface E is about 2.5 : 1 to about
4:
1. As a result of the asymmetry of the light-emitting surface E, the laser
beam
emitted has an elliptical cross section.
In Figure 2, a first laser arrangement 1 is shown, which
may be disposed, for example, in a multi-beam laser sighting mechanism.
The laser arrangement 1 comprises two semiconductor lasers 2 and 3, which
are aligned perpendicularly to one another such that the longitudinal extents
of their light-emitting surfaces are perpendicular to one another. This is
indicated in Figure 2 by the arrows I, which are disposed perpendicularly to
one another. The primary beam bundles P, Q, which are emitted by the laser
light sources 2, 3, are passed through the collimator lenses 4, 5 and
superimposed at a semitransparent mirror 6 to form a total primary beam
bundle G.
The cross-sectional contour of the total primary beam
bundle G at the site of the superimposition is indicated in Figure 3. As
shown,
in Figure 3, the two elliptical primary beam bundles P, Q are rotated at 90
to
one another because of the arrangement, as shown in Figure 2, which has
been selected for the two semiconductor lasers 2, 3. The superimposing of
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the two elliptical primary beam bundles P, Q leads to a total beam bundle G,
which has an essentially star-shaped cross section. The semitransparent
mirror 6 is disposed at an angle of 45 to the two primary beam bundles P, Q.
The primary beam bundles P, Q, superimposed to form a
total primary beam bundle G, are passed on to a beam divider 7, which is
provided with reflecting surfaces 8 and a central passage borehole 9 for a
central section of the total primary beam bundle G. Instead of a passage
borehole 9, the beam divider can also be provided with plane parallel polished
surfaces, through which the vertically striking portion of the primary beam
bundle can pass without hindrance. The reflecting surfaces 8 are aligned at
an angle of 90 to one another and inclined at an angle of 45 to the incident
total primary beam bundle. For example, the beam divider 7 has the shape of
a truncated pyramid with a square base surface and mirrored side surfaces.
Because of the essentially star-shaped cross-sectional contour of the total
primary beam bundle G, a partial section of a semi-ellipse is assigned to each
reflecting side surface 8 of the truncated pyramid. The portion of the total
beam bundle G, striking the reflecting surface 8, is deflected by 90 with
respect to the direction of incidence. The central section of the superimposed
total beam bundle G passes through the beam divider 7 essentially
unhindered through the central passage opening 9. In the case of four
reflecting surfaces 7, four partial beam bundles T, pairs of which extend
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perpendicularly to one another, can be produced. The central portion of the
total primary beam bundle extends perpendicularly to the deflected partial
beam bundles T. In this manner, the Cartesian coordinate system, which has
a common origin, can be produced.
The laser arrangement 11, in an alternative embodiment,
as shown in Figure 4, once again comprises two semiconductor lasers 12, 13,
which are disposed at an acute angle to one another. The light-emitting
surfaces of the semiconductor lasers 12, 13 are aligned so that their
io longitudinal extents are perpendicular to one another, as indicated by
arrows I
in the semiconductor lasers 12, 13. The two laser light sources 12, 13 are
directed directly onto a beam divider 17 where they are superimposed.
Collimator lenses 14, 15 may be disposed between the beam divider 17 and
the laser light sources 12, 13. The reflecting surfaces 18 of the beam divider
17 are disposed perpendicularly to one another and inclined to the incident
primary beam bundles P, Q so that the reflected partial beam bundles extend
perpendicularly to one another and intersect in their geometric elongation in
an origin. In the case of four reflecting surfaces 18, two pairs of partial
beam
bundles each extend perpendicularly to one another. To produce five partial
20 beam bundles, one of the incident primary beam bundles is aligned parallel
to
the axis of the beam divider. The key reflecting surfaces for these primary
beam bundles are then inclined at an angle of 450 to the direction of the
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primary beam. For the middle portion of the primary beam bundle, the beam
divider is provided with a passage borehole or with plane parallel, polished
surfaces.
For the further alternative embodiment of the laser
arrangement, which is shown in Figure 5 and labeled 21 as a whole, two
semiconductor lasers 22, 23 are disposed next to one another. Their light-
emitting surfaces are aligned perpendicularly to one another, as indicated by
the arrows I, which extend perpendicularly to one another. The primary
beams P, Q are directed onto a beam divider 24, which comprises two prisms
25, 26. Each prism 25 or 26 is in the beam path of a primary beam bundle P
or Q. The first prism 25 is in the beam path of the first primary beam bundle
P
and has two reflecting surfaces 28, which extend at an angle of 45 to the
first
primary beam bundle P. As a result, the primary beam bundle P is split into
two partial beam bundles Z, -Z, which are aligned with one another but spread
out in opposite directions. The second prism 26, which is in the beam path of
the second primary beam path Q, is disposed in the immediate vicinity of one
of the reflecting surfaces of the first prism 25. The second prism 26 is
rotated
through 90 with respect to the first prism. Correspondingly, its reflecting
surfaces 28 are also rotated by 90 with respect to those of the first prism
25.
The second prism 26 has plane parallel, polished surfaces 29 at the prism
edge and at the base surface. The side surfaces 30 of the second prism 26
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are plane parallel and extend perpendicularly to the partial beam bundles Z, -
Z, which are deflected by the first prism 25. The two side surfaces 30 form
transmission surfaces for the deflected partial beam bundle Z and are
polished optically. The incident second primary beam bundle Q is deflected
by 90 from the reflecting prism surfaces 28 of the second prism 26. This is
indicated by the partial beam bundles X, -X, which extend perpendicularly to
the partial beam bundles Z, -Z, deflected from the first prism 25. A portion
of
the second primary beam bundle Q passes through the prism 26 without
hindrance through the plane parallel, polished surfaces 29 and forms a partial
beam bundle Y, which extends perpendicularly to the remaining partial beam
bundles Z, -Z, Y. In this way, a Cartesian coordinate system with a common
origin is produced.
The two semiconductor lasers of the laser arrangement
offer the possibility of forming the axes of the Cartesian coordinate system
with different intensities or also in different colors, by using semiconductor
lasers with different outputs and/or wavelengths. Due to the inventive
arrangement of the two semiconductor lasers, the elliptical beam shape of the
primary beams is superimposed in an advantageous manner. By these
means, the losses can be reduced clearly in conjunction with a beam divider
of the type described, since the cross section of the incident laser beam
bundle is approximated to the arrangement of the reflecting surfaces. By
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superimposing the two primary beams to form a total beam bundle,
semiconductor lasers with low outputs can be used, as a result of which the
economic efficiency of laser devices, equipped with the laser arrangement, is
increased.
Although the present invention and its advantages have
been described in detail, it is understood that various changes, substitutions
and alterations can be made herein without departing from the spirit and
scope of the invention.
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