Note: Descriptions are shown in the official language in which they were submitted.
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COLOR ANALYZING APPARATUS
WITH POLARIZED LIGHT SOURCE
FIELD OF THE INVENTION
The present invention relates to a color analyzing and setting apparatus and,
in particular, a color analyzing apparatus for analyzing the color of a tooth
surface while
eliminating the effects of glare and reflection and for analyzing the
structure of the tooth.
BACKGROUND OF THE PRESENT INVENTION
Color setting apparatuses for sensing the color of a tooth surface are known,
and an example of is described in DE-OS 195 34 517. This publication discloses
a light
source for emitting light along three paths to irradiate a tooth surface, and
three
corresponding sensors each for sensing the respective brightness of one of
three base colors.
It is taught that evaluation or analysis of the sensed results should lead to
the least possible
color deviation from the available tooth colors.
It is further conventionally known that reflected light or reflections distort
or
falsely influence the evaluation or analysis results. The arrangement of the
light sources at
various angles and emission of light therefrom at various spectra permits some
compensation of the tendency toward reflection.
It has long been known that, due to the reduced or modest peak-to-valley
thickness of the tooth surfaces, reflections distort the color analysis. In
order to maintain
the least possible degree of reflection, it is known to apply titanium oxide
powder on the
tooth surface as a contrast powder. However, depending upon the strength or
thiclmess of
the applied layer, a distortion of the color analysis is possible.
In order to avoid the disadvantages of contrast powder, the use of a
fluorescing color has been suggested (compare DE-OS 40 37 007) whereby the
fluorescing
color absorbs the green color and emits gold or red. However, a decided
disadvantage of
such a fluorescing color lies in the fact that the color is distorted so that
a compensation
therefor must be undertaken in the event that the light shift is to be
captured or sensed.
Also, it is difficult to apply the fluorescing color exactly in a uniform
strength or thickness,
as a result of which this approach has not heretofore found widespread
acceptance.
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In connection with the evaluation of the tooth surface structure, it is
desirable; in contrast to the evaluation of the tooth surface color, to
capture or sense
shadows which reveal or indicate the structure. In this context, as well, the
application of a
contrast powder or fluorescing color leads to distortion as the shadowing or
the like is
thereby reduced or eliminated.
It has further already been suggested to use a rotatable polarization filter
which, in accordance with the wishes of the user, can be configured to permit
the polarized
light reflectance to be passed therethrough or to be reduced in an infinitely
variable manner.
This approach, indeed, permits the comparison of a tooth surface with and
without
reflection. However, the analysis of the sensed result is strongly dependent
upon the angle
at which the light source irradiates the tooth surface. Those areas of the
tooth surface
remote from the light source are frequently darkened or cast in shadow in an
arrangement in
which the light source is disposed to the side of the tooth surface and,
consequently, such
areas of the tooth surface cannot readily be recognized or sensed.
SUMMARY OF THE PRESENT INVENTION
The present invention offers a solution to the challenge of providing a color
sensing apparatus for sensing the color of a tooth surface, providing
improvements in color
analysis as well as in analysis of the structure of a tooth surface.
A preferred embodiment of the invention is a light analyzer camera with a
housing that is configured for handheld use with a single hand. The camera has
first and
second light sources configured and disposed for irradiating light on an
object disposed at
an object location. The first light source preferably produces a substantially
unpolarized
light. The second light source produces a second light that is polarized along
a first axis,
preferably by employing a polarization filter. A light receiving element is
configured and
disposed for receiving the first and second light reflected from the object
and comprises a
sensing device that is configured for sensing and producing an image
corresponding to the
reflected light. The light receiving element has a polarizing filter
configured for polarizing
the reflected second light along a second axis at an angle to the first axis
for reducing glare
and reflection. Preferably an image is produced from the light from each of
the light
sources, and a timer associated with the light sources and receiving element
activates the
first and second light source sequentially for producing one of the first and
second images
before the other.
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The preferred camera includes a light channel configured for allowing light
to pass therethrough and for blocking light from entering the channel radially
from other
sources. The first and second.light sources are disposed adjacent the light
receiving element
in this embodiment, along a direction angled towards the light channel, and
preferably
inclined forward towards the object location. Additionally, the first and
second paths are
preferably oriented at different angles with respect to the object position
In a preferred method of imaging an object according to the invention, the
object is irradiated with a first light from a source such as a camera. The
first light reflected
from the object is received in the source or camera, and a first image is
produced,
corresponding to the received first light. The object is irradiated with a
second light from
the source or camera, the second light being polarized along a first axis. The
second light
reflected from the object is passed through a polarization filter for
polarizing the second
light along a second axis and received to produce a second image corresponding
to the
received second light. Where the image from the first light can show the
structure of the
tooth in detail due to glare and reflections produced in the image, the image
formed with the
second light is free or more free from undesired reflections, allowing the
color to be
analyzed more accurately. Preferably, one of the lights is irradiated and
received before the
other, and the irradiation of each light is preferably conducted within about
two seconds
from each other. The preferred method also includes blocking light from being
received
from other than the source or camera. The preferred object comprises a tooth,
and the
images are generated electronically. When the source is a camera, the images
may be
viewed in the camera or can be electronically transferred to another location
for viewing.
By using two light sources, which irradiate the tooth surface at a different
time and from different angular orientations, shadows are compensated for
which would
arise during the production of pictures of the tooth surface upon illumination
thereof by a
traditional light source arrangement. Filtering of the light through a single
polarization
filter, as in the preferred embodiment, has been found not to disturb or
hinder the evaluation
of the shadowing on the tooth, which provides information on the tooth
structure, where the
light that irradiates the tooth surface does not pass through a polarization
filter. The
preferred embodiment is also advantageous in that the irradiation of the tooth
surface with a
light source having a polarization filter can produce a reflection-free
picture of the tooth
surface, while through the irradiation of the tooth surface with another light
source without
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polarization filter and which is oriented at a different
angle relative to the tooth from the other light source
provides a good sensing and capture of the tooth structure.
The light sources are preferably configured as
white light sources. In addition, preferably a reference
sample is irradiated with the same light sources to provide
reflections captured by the same capture or sensing device
of a light receiving element for electronic comparison to
the images of the teeth. The reference sample is preferably
disposed at a location close to and below or above the tooth
or teeth being irradiated.
The present invention also provides for
irradiating or illuminating the teeth from two different
sides thereof, improving the illumination thereof for color
and structure capturing. In this manner, in connection with
the sequential actuation of the light sources, the structure
of the tooth can be substantially clearly recognized or
sensed, such that the tooth model that is subsequently
produced based on the images gathered can be made including
the sensed tooth structure.
In accordance with the present invention, through
the common receipt or capture of pictures, which are
produced by the different light sources, an effective or
practical monitoring or quality control of the light sources
and their color spectrums can be undertaken. In this manner,
a white card can be inserted in substitution of the tooth
surface and the measured or sensed color value of each light
source can be used for the white color comparison. Moreover,
an optical lens is preferably disposed in the light path
between the tooth surface and the capture or sensing device
of the receiving element, and it is possible with this lens
to focus the picture of the tooth surface onto the capture
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or sensing device, in order to produce a precise image of
the tooth surface.
Light sources are preferably provided on opposite
sides of the tooth. It is possible to place a light source
with a polarization filter at an angle of approximately 45
relative to the tooth surface to irradiate the tooth surface
from this angle. A further light source without a
polarization filter can be disposed at an angle of about 70
relative to the tooth surface so that shadows are more
defined in the image produced by this light source.
In accordance with one aspect of this invention,
there is provided a light analyzer, comprising: a first
light source configured and disposed for irradiating with a
first light an object disposed at an object location, thus
generating first reflected light; a second light source
configured and disposed for irradiating the object with a
second light that is polarized along a first axis, thus
generating second reflected light; a light receiving element
configured and disposed for receiving both the first and
second reflected light from the object and comprising a
sensing device that is configured for sensing and producing
an image corresponding to the reflected light, wherein the
light receiving element comprises a polarizing filter
configured for polarizing the second reflected light along a
second axis at an angle to the first axis for reducing glare
and undesired reflection, and wherein said image comprises a
first image corresponding to the first reflected light, and
a second image corresponding to the second reflected light;
and a timer associated with the light sources and receiving
element for activating the first and second light sources
sequentially for producing one of the first and second
images before the other.
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In accordance with another aspect of this
invention, there is provided a light analyzer, comprising:
first and second light sources configured and disposed for
directing light along first and second light paths,
respectively, at different times towards an object disposed
at an object position; a first filter configured for
filtering light with predetermined qualities; and a light
receiving element disposed along the light paths for
receiving the light reflected from the object, the light
receiving element comprising a sensing device that is
configured for sensing characteristics of the light; wherein
the light analyzer is configured such that the first filter
is disposed along the first light path between the second
light source and the object position, and the second light
path does not pass through the first light filter.
In accordance with a further aspect of this
invention, there is provided a dental camera comprising: a
housing configured for handheld operation using a single
hand; first and second light sources mounted to the housing
and, the light sources being separately operable and
configured and disposed for directing light along first and
second light paths towards a tooth disposed at an object
position, wherein the first and second light paths are
oriented at different angles with respect to the object
position and wherein the first and second light sources
direct light towards the tooth at different times; a light
receiving element mounted to the housing and disposed along
the light paths for receiving the light reflected from the
tooth and configured for forming first and second images
corresponding to the received light from the first and
second paths, respectively.
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In accordance with yet another aspect of this
invention, there is provided a method of imaging an object,
comprising: irradiating the object with a first light from a
source; receiving the first light reflected from the object
in the source; producing first image corresponding to the
received first light; at a different time from irradiating
the object with the first light, irradiating the object with
a second light from the source, wherein the second light is
polarized along a first axis; passing the second light
reflected from the object through a polarization filter for
polarizing the second light along a second axis; receiving
the second light from the polarization filter in the source;
and producing a second image corresponding to the received
second light.
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 schematic drawings, in
which:
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Fig. 1 is a schematic view of an embodiment of the color setting apparatus of-
the present invention;
Fig. 2 is a schematic representation of the image generated by a capture or
sensing device of a tooth surface, whereby the left-hand view shows the
receipt of a tooth
surface image via a light source not having a polarization filter and the
right-hand view
shows the receipt of a tooth surface image via a light source having a
polarization filter;
Fig. 3 is a side cutaway view of an embodiment of a dental camera
constructed according to the invention;
Fig. 4 is a cutaway view of the optical assembly thereof;
Fig. 5 is a cutaway view of the optical'assembly of another embodiment with
a zoom feature; and
Figs. 6-8 are back views of a camera according to the invention showing
images produced by operating the zoom feature.
DETAILED DESCRIPTION OF TIBE PREFERRED EMBODIMENTS
The color setting apparatus 10, as shown in Fig. 1, includes a light source
12,
which is disposed fairly substantially to the side of a tooth surface 14 for
directing light
from that side. Additionally, a light source 16 is provided, which is disposed
toward the
same side of the tooth surface as the light source 12 and is arranged at an
angle relative to
the tooth surface 14.
A capture or sensing device 18 is preferably disposed centrally and along a
middle plane relative to the tooth surface 14, the sensing device 18 being
operable to
capture or sense the light reflected from the tooth surface 14.
A light source 20 is disposed symmetrically to the light source 16 and at an
angle relative to the tooth surface 14 but=is disposed on a different side of
the tooth surface.
In the embodiment of Fig. 1, the apparatus includes a fourth light source 22
disposed fairly
substantially to the side of the tooth surface 14. The light source 22 is
arranged to its
respective side in a symmetric manner with regard to the location of the light
source 12 on
its respective side of the tooth surface. Preferably, light sources 16,20 are
disposed at
substantially the same angle from the sensing device 18. Similarly, light
sources 12,22 are
disposed at substantially the same angle from the sensing device 18, greater
than the angle
at which light sources 16,22 are disposed.
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Each light source 12, 16, 20, and 22, preferably comprises a plurality of
LEDs or light emitting diodes, so that a correspondingly high light output is
available. All
of the light sources 12, 16, 20, and 22, are preferably configured as white
light emitting
diodes. The light sources emit light 24 as shown,. for example, schematically
with respect
to the light sources 12 and 16, and light 24 irradiates the tooth surface 14
and is reflected
thereby to be captured or sensed by the sensing device 18.
In accordance with the embodiment shown, the light source 12 and the light
source 22 are configured such that they directly irradiate the tooth surface
14 without a filter
disposed therebetween. In contrast thereto, polarization filters 26,28 are
disposed in front
of light sources 16,20, respectively, between these light sources 16,20 and
the tooth ;surface
14 along the path of light 24. Light 24 from these two light sources 16,20
passes through
the polarization filters 26,28 before hitting the tooth surface 14. The
polarization filters 26
and 28 are arranged, for example, to polarize the light in a vertical manner,
although other
directions of polarization are possible.
Moreover, in the light path between the tooth surface 14 and the sensing
device 18, a further polarization filter 30 is disposed. The polarization
orientation of the
polarization filter 30 is, in contrast or perpendicular to the aforementioned
polarization
filters 26,28 for the light sources 16,20, i.e. horizontal in the embodiment
shown. By this
arrangement, reflections from the tooth surface can be suppressed in a
conventional r:nanner,
if the light sources 16 and 20 are actuated.
Light sources 12, 16, 20, and 22 are preferably surrounded by reflectors for
effecting an increase in the light output of the light sources, and light
emitted from the light
sources is collected by collecting lenses 38. Preferably, these collecting
lenses 38 are so
configured that they are color true and cause no distortion of the emitted
color spectrums.
In a corresponding manner, a collecting lens 40 is disposed between the
tooth surface 14 and the sensing device 18, which focuses the light for the
formation of a
picture of the tooth surface 14 onto the sensing device 18. T"ne sensing
device 18 comprises
a CCD-sensor or any other desired suitable sensor.
Fig. 2 shows the manner in which a picture or image of the tooth surface 14
is captured or sensed. At least the substantially the whole of one tooth is
preferably imaged,
although at least two teeth can be viewed in the preferred embodiment. In the
figure,4,
between three and four teeth are included in each image. The left-hand view
shown in Fig.
2 shows a picture 32, which is produced upon actuation of the light source 12.
The
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reflections effected by the irradiation of the tooth surface by the light
source 12 perrnit
capture or recognition of the structure of the tooth surface. In contrast, the
right-hand view
shown in Fig. 2 shows a picture 34, which is produced upon actuation of the
light source 16.
By polarization of the light falling on the tooth surface in an orientation
which is
perpendicular to the polarization orientation of the reflections, the
reflections are
substantially reduced and substantially canceled and eliminated, making the
determination
of the specific color easier.
The pictures 32 and 34 show, in addition to the tooth surface 14, respective
reference samples 36 which are inserted in immediate neighboring relation
underneath the
tooth surface. Preferably, the corresponding reference sample image results
are arranged
such that they are immediately adjacent those taken of the teeth.
Referring to Figs. 3 and 4, a preferred embodiment of a camera 50, including
the color setting apparatus includes a housing 52 and a mouthpiece 54, which
is fitted to a
coupling member 56 of the housing 52. A sensing device 58, which preferably
comprises a
light receiving element such as a CCD chip, is preferably disposed
substantially coaxially
with a receiving light channel 60, which preferably blocks light from entering
directly from
the light sources within the camera.
Within the receiving light channel 60 are preferably disposed an infrared
filter 62 and one or more camera lenses 64, which are mounted in a movably
focus
assembly 66. The focus assembly 64 is controlled preferably by electronics and
a motor
disposed within the camera 50 to move the focus assembly 64 in directions 65
to vary the
distance between the lens 64 and the sensing device 58 in order to focus the
received
reflected light appropriately on the CCD to obtain a clear image. A receiving
polarization-
filter 68 is positioned along the reflected light path 70 ahead of the sensing
device 58.
Light sources 72,74 are preferably disposed on each lateral side from the
receiving light channel 60. The preferred light sources 71,73 comprise rows of
LEDs
configured for producing a white light. In the embodiment shown, the LEDs
72,74 are
mounted on a supports 76 that extend along a direction angled towards the
light channel,
preferably in a forward direction towards an object position 79, at which the
object to be
pictured, such as teeth, is located for generating the images thereof. The
supports 76 are
preferably disposed at an angle 78 to the axis 80 of the light channel of
about between 10
and 80 , more preferably about between 30 and 60 , and most preferably about
between
40 and 50 . The preferred supports 76 are straight, although alternatives can
be curved to
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obtain optimum placement of the light sources. The present embodiment includes
a support
on two sides of the receiving light channel 60, but a different number of
supports and light
source locations can be employed. For instance, one embodiment has light
sources
supported substantially surrounding all sides of the receiving light channel
60, and the
supports can be connected as a single unit.
The location and configuration of the ligbt sources 72,74 is preferably
selected so that the light paths reach the object position 79 from different
angles. This
arrangement can provide to maximize the effectiveness of the light sources to
illuminate the
teeth for color analysis or for visualizing the tooth structure.
A source polarization-filter 82 is disposed along light paths 84 from LEDs
74. Source polarization filters 82 are preferably configured and oriented for
polarizing the
light from LEDs 74 along a first axis, whereas the receiving polarization-
filter 68 is
configured and oriented for polarizing the reflected light along a second axis
that is
different than the first axis. Preferably, these first and second axes of the
source and
receiving filters 82,68 are disposed at more than about 30 to each other,
more preferably at
more than about 45 to each other, more preferably at more than about 75 to
each other,
and most preferably at about a right angle to each other with respect to light
paths 84,70 for
best eliminating glare and disparate reflections from the image formed based
on the light
from sources 74. Lenses 86 are preferably cylindrical lenses an are disposed
along light
paths 84 for focusing and distributing the light from sources 74 to the teeth
to properly
illuminate the teeth.
Light sources 71 preferably produce substantially unpolarized light, with no
polarization filter between the object position 79 and the LEDs 72 along light
path 88.
Alternatively, a polarization filter may be employed with light sources 71
with a relatively
small or no difference in polarization axis orientation from the polarization
axis of receiving
polarization-filter 68. Additionally, in the embodiment shown in Figs. 3 and
4, the second
light source 72 does not include a lens in front of LEDs 72, but alternative
embodiments
also include lenses in the light path coming from these LEDs.
As shown in Fig. 3, the axis of the optical assembly of the camera 50 is
oriented substantially coaxially with the mouthpiece 54 and coupling member
56, and main
light channel 90 extends through the coupling member 56 and the mouthpiece 54
to permit
the light from the light sources 72,74 to irradiate the teeth at the object
position 79 and the
light reflected by the teeth to return into the receiving light channel 60.
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The mouthpiece 54 of the embodiment shown is configured to set the
distance between the camera and the teeth and includes radially extending
wings 92
configured for placement between the patient's lips and teeth or gums to block
light from
other sources from entering the camera and affecting the images produced. Bite
protrusions
92 preferably extend forward from the wings for the patient to bite on, to
help position the
teeth with respect to the camera. The camera housing 52 preferably includes a
protective
transparent window, which is preferably disposed in the coupling portion 56 to
prevent
matter from the patient's mouth from entering the camera. A color reference
sample 93 is
disposed in the mouthpiece 54 to appear in the images generated of the teeth
for comparison
to the tooth color, as the sample 93 is of a known color, preferably white.
The preferred housing 52 also houses electronics 94 for controlling the
camera functions, producing images from the signals from the CCD, and for
storing and
transferring data, including image files, to another computer or electronic
device. The
electronics comprise storage medium, such as a digital storage medium for
storing the
images and other data. Also contained within the housing are a power source
96, such as a
battery or accumulator for powering the camera; a display 98, which is
preferably a color
LCD screen configured for displaying the image being presently generated and
stored
images; and a keypad 100 that provides an interface for a user to operate the
camera.
Preferably menu items related to camera control and information about the
images are
shown on the display 98. A protective transparent window is disposed outside
of the
display 98 for viewing the display preferably from a side of the camera 50
opposite from
the object location. Many of these components are disposed within an elongated
handle
portion 102 of the housing, which extends preferably at a downward angle from
the main
light channel 90. Preferably at the bottom ends of the handle 102 is an
interface 104, such
as a USB interface, for connecting and transferring data to a computer or
other electronic
device.
The camera 50 preferably has a timer in the electronic circuitry that is
configured for generating an image from the light from each of the first and
second sources,
preferably in response to a single push of a single key of the keypad 100 by
the user. These
images are preferably taken within about 2 seconds of each other, more
preferably within
about 1 second of each other, stiIl more preferably within about %2 second or
less.
As shown in Figs. 3 and 4, the light sources are disposed adjacent a forward
end of the receiving light assembly and receiving light channel 60, thus
delivering the light
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directly to the object position, obviating the need for light conduits, such
as fiber optics,
prisms or mirrors to deliver the light to the object position 92. In an
alternative
embodiment, however, the one or more of the light sources is disposed well
behind the front
end of the receiving light channel, and the light from each light source is
irradiated to the
object position by conducting the light through optical conduits and by
reflecting the light
by with prisms and mirrors.
Referring to Fig. 5, the embodiment shown includes a zoom optical
assembly 106 for varying the focal length of the camera. The zoom assembly 106
itself
comprises one or more lenses and is controller preferably by the electronics
94 and a motor
to vary the image from wide atigle, as shown in Fig. 6, where one, two, three,
or four teeth
are shown in the image for example, to an image and lens arrangement that
tends towards a
telephoto, narrower-angle arrangement and image, for viewing the entire mouth,
as shown
in Fig. 7, or face of a patient, as shown in Fig. 8.
While illustrative embodiments of the invention are disclosed herein, it will
be appreciated that numerous modifications and other embodiments may be
devised by
those skilled in the art. For example, whereas the preferred embodiment
employs a
polarization filter in one of the light sources, a light source of an
alternative embodiment is
configured or has a filter configured- to block out or reduce light with a
certain characteristic
that is present in the light from the other light source. Therefore, it will
be understood that
the appended claims are intended to cover all such modifications and
embodiments that
come within the spirit and scope of the present invention.
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