Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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LIGHT CURING DEVICE
Background of the Invention
' The present invention relates to a light curing device,
especially for irradiating curable dental compositions, with a light
source and a light guiding device, such as a light guide, having a
light receiving opening, whereby in the path of the light beam
between light source and light receiving opening a focusing lens
is arranged. The device is especially used for curing dental plastic
materials that are polymerizable under the effect of light.
Such a light curing device is known from German
Offenlegungsschrift 32 37 510. In such a light curing device the
light source is surrounded by a reflector which focuses the emitted
light radiation onto a focusing lens. The piano-convex focusing
lens the planar surface of which is facing the light source, is
designed to focus the light beam onto the light receiving opening
of the light guide. In the known light curing device spectral lamps
are used as light sources, which are relatively large and heavy in
order to be able to introduce monochromatic light radiation into the
light guide.
In order to facilitate handling of the device, the known light
curing device has a flexible light guide of a length of 2 meters.
With this construction, the operator is thus limited in his
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moveability by the connection via the light guide. Furthermore,
with a comparatively long and flexible light guide there is always
present the danger of kinking. Even though possible external
- damages cannot be seen, the resulting light efficiency of the light
guide is considerably reduced without being apparent to the
operator.
However, this carries the considerable risk that a light
curing step is not completed so that the used dental material is not
cured according to specification.
Furthermore, hand-held devices are known, for example,
from German Offenlegungsschrift 42 11 230. With such hand-
held devices it is conventional to use for the comparatively
compact arrangement light sources of high energy density which
results often in thermal problems. Despite the comparatively high
energy expenditure, the light efficiency for these hand-held
devices is still improvable.
It is therefore an object of the present invention to provide
a light curing device of the aforementioned kind that is improved
with respect to light efficiency, is easier to manipulate, and
provides a light efficiency that ensures complete polymerization
over an extended service life.
Summary of the Invention
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The present invention provides a hand-held light
curing device comprising: a light source; a light guiding
device having a light receiving opening; a lens arrangement
comprising a focusing lens positioned between said light source
and said light guiding device; said focusing lens comprising a
first cut-off filter vapor-deposited on the surface of the lens
proximal the light source and a second cut-off filter vapor-
deposited on the distal surface of the lens, the first cut-off
filter cutting off light at wavelengths higher than a
predetermined wavelength and the second filter cutting off
light at wavelengths lower than a predetermined wavelength.
Advantageously, the focusing lens is a plano-convex
lens having convex surface, wherein the convex surface faces
the light source.
Advantageously, the hand-held curing device further
comprises a reflector comprising an inner surface with
reflective coating. The reflector is positioned adjacent to
the focusing filter and widens conically in a direction toward
the light source.
The focusing lens preferably consist of heat
absorbing glass.
The focusing lens is preferably spaced from the light
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guiding device, and the focus of the focusing lens coincides with
the light receiving opening or is positioned within the light guiding
device behind the light receiving opening.
Advantageously, the light source is a compact lamp having
a high light efficiency relative to the size of the lamp and relative
to the amount. of electric energy supplied to the lamp.
Expediently, the lamp is a halogen lamp.
The lens arrangement may further comprise a concave-
convex lens or a biconvex lens.
The cut-off filter allows light below a selected wavelength
threshold to pass.
The cut-off filter is opaque to infrared radiation.
The cut-off filter preferably has reflective properties with
respect to the blocked radiation.
Surprisingly, with the inventive measures a favorable light
efficiency with respect to light curing can be achieved despite the
embodiment as a compact, hand-held device. Even though the
compact halogen universal lamps are used, which are
considerably less expensive than spectral lamps, the light
efficiency is surprisingly good and does not result in an
undesirable heating within the mouth of the patient or with respect
to the dental material to be cured. Apparently, the cut-off filter
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vapor-deposited onto the focusing lens has an especially good
reflective effect for undesirable radiation without impairing the light
radiation emitted by the halogen lamp. The cut-off filter has an
especially good transmissivity for the frequency ranges required
for polymerization. Advantageously, a light guide of a
comparatively large diameter can be used whereby weight and
handling problems of light guides of greater diameters are
substantially reduced with respect to known light curing devices
since the inventively used light guide extends only over a length
of a few centimeters instead of being 1 to 2 meters long.
The inventive light curing device is especially
advantageously realized as a hand-held device. Individual
advantages result, however, also in an embodiment as a
stationary device with flexible light guide.
The risk of unnoticed reduction of the light efficiency due to
breakage of the light guide is practically prevented since the light
guide can optionally be surrounded by a metal tube so as to be
especially well protected since it must not be flexible.
According to a preferred embodiment, it is suggested to
apply the cut-off filter onto the convex surface of the focusing lens.
Inasmuch as heat radiation is reflected by the cut-off filter, the
heat radiation is diverted which is especially favorable with respect
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to heat dissipation.
In an especially advantageous embodiment, the inventive
light curing device comprises a reflector which is positioned
adjacent to the focusing lens and/or cut-off filter whereby the
reflector cone extends between the light source and a cut-off filter
and/or the focusing lens and whereby the cone angle opens
toward the light source. This reflector increases the light
efficiency in that the radiation emitted by the light is reflected and
guided toward the focusing lens and improves in a double function
at the same time the heat dissipation of the cut-off filter, especially
when the conical reflector sleeve comprises a metallic reflective
layer.
According to another embodiment, the focusing lens is a
piano-convex lens the convex surface of which is especially facing
the light source. This embodiment is especially favorable with
respect to mounting and with respect to light introduction into the
light guide. Light beams reflected by the light receiving opening
are immediately reflected back at the planar surface of the
focusing lens so that they can reenter the light guide.
When the focusing lens is made of heat- absorbing glass,
the penetrating infrared radiation is mostly absorbed and the
temperature is increased. In this context it is especially favorably
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when the focusing lens is spaced from the light guide so that
there is no risk that the light guide could be heated to
unacceptable limits. The absorption properties furthermore act
to compensate residual heat whereby it is understood that in
this embodiment it may be advantageous to apply the cut-off
filter at the surface facing the light guide in order to
prevent the emission of heat radiation in the direction of the
light guide.
Even though, in general, other methods for
application of the cut-off filter are possible, it is preferred
to vapor-deposit the cut-off filter. This allows for uniform
and minimal layer thickness with optimal minimal transmission
damping in the transmissive range of the filter.
It is understood that, if needed, the focusing lens
can be used in combination with further lenses in order to
improve the optical properties.
BRIEF DESCRIPTION OF THE DRAWINGS
The object and advantages of the present invention
will appear more clearly from the following specification in
conjunction with the accompanying drawings, in which the only
Figure shows a portion of the inventive light curing device in
section, representing the light guide and the focusing lens.
DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention will now be described in detail
with the aid of several specific embodiments utilizing the only
Figure.
As apparent from the only Figure, the inventive light
curing device 10 comprises a light guide 12, a focusing lens
14, and a reflector 16 which are housed in a common housing 18.
The housing 18 furthermore supports a non-represented light
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source which can be optionally provided with a well known
reflector and which would be positioned to the left in the
drawing. The light guide 12 is only partly represented in the
drawing and extends over a length of a few centimeters,
optionally with a slightly bent tip, in order to allow easy
access to any area within the mouth of a patient.
The light curing device is a hand-held device and has
a construction as is, for example, known from German
Offenlegungsschrift 42 11 230. The housing 18 comprises a
plurality of vent openings 20, 22 which extend substantially
annularly coaxially to the optical axis 24 and which are
interrupted by ribs 26, 28 which are uniformly distributed over
the circumference.
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The housing is provided in a manner known per se with a
fan which is arranged behind the lamp and operated such that the
vent openings 20, 22 act as air inlet openings. Thus, relatively
cold air passes along the focussing lens 14 and the reflector 16
and provides a comparatively good cooling effect thereat. The
focusing lens. 14 is supported in the housing with a separate
securing sleeve 30 which also supports the light guide 12. The
light guide 12 is supported within the securing sleeve 30 by a
socket 32. The arrangement of focusing lens 14 and light guide
12 within the securing sleeve 30 is selected such that the light
receiving opening 34 of the light guide 12 is clearly spaced from
the focusing lens 14. In the represented embodiment the spacing
is greater than the maximal thickness of the focusing lens 14. The
focus of the focusing lens 14 is positioned somewhat behind the
light receiving opening 34 within the light guide 12.
The focusing lens 14 is a piano-convex lens whereby the
planar surface faces the light guide and the convex surface faces
the light source. On the side facing the light source a cut-off filter
is vapor-deposited onto the lens. fn addition, the lens is
comprised of heat-absorbing glass which absorbs to a large
extend infrared radiation. Due to this arrangement, it is achieved
that, despite the directly adjacent positioning to the light guide 12,
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practically only light with the desired wavelength range can enter
the light guide 12. For example, the cut-off filter can be embodied
such that undesirable UV radiation is filtered out. The rounded
. embodiment of the cut-off filter 36 also results in that the blocked
radiation is reflected over a large surface area and distributed.
The reflected. radiation impinges on the reflector 16 which is
positioned within the direct air flow at the flow channel 38 and
which is thus well cooled. Furthermore, the cut-off filter 36 and
thus the focusing lens 14 are positioned in thermal vicinity of the
reflector 16; via the vent openings 22 an additional flow channel
which is directly adjacent is opened which participates in the
cooling effect.
The support of the lens 14 is such that it is clamped with a
securing ring 40, that is optionally elastic, between the securing
sleeve 30 and the reflector 16. The reflector 16 is screwed from
the interior onto the housing 18 so that the screw connection
supports in sequence the securing sleeve 30, the focusing lens
14, the securing ring 40, and the reflector 16 at the corresponding
securing flange 42 of the housing.
As can be seen in the drawing, the light radiation emitted
by the light source is refracted partially directly, according to the
course of the light beam 44, and then enters, parallel to the optical
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axis 24, the light guide 12. Partly, the radiation is reflected at the
reflector 16, as indicated by the light beam 46, enters the lens
and, after corresponding refraction within the focusing lens 14,
exits parallel to the optical axis 24. This is of course only true for
light beams with wavelength which pass through the cut-off filter
36.
In the shown embodiment, the reflector 16 is a metal part
and has good heat conducting properties. However, it is
understood that instead a plastic part with inner reflective layer
can be used. It is advantageous to widen the reflector in the
direction toward to the light source.
Instead of the focusing lens 14 it is also possible to use
focusing lenses of a different design or to us a corresponding lens
arrangement. The focusing lens is provided in a suitable manner
with a cut-off filter which prevents that light or electromagnetic
radiation with an undesirable wavelength can enter the light guide
12.
The present invention is, of course, in no way restricted to
the specific disclosure of the specification and drawings, but also
encompasses any modifications within the scope of the appended
claims.
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