Patent Application
20080082000
The invention will now be described in more details refering to the drawings wherein:
The dental camera shown in the drawings has a housing 10 formed as a injection molded plastics part. The housing 10 is shown as being a one piece housing. It is to be understood that the specialist in the art can also use a multi-part housing as may be required by the respective production requirements. In such case the different parts of the housing can be connected in fluid-tight manner using seals or can be connected using an adhesive or can be welded.
The housing 10 has a grip portion 12 having essentially the form of a cylindrical sleeve being closed at one end thereof. At its free end the grip portion 12 carries a tapered and angled housing portion 14, the downward facing end of which is closed by an entrance window 16 and a light emission window 17 arranged in side-by-side relationship.
The entrance window 16 is simultaneously formed as an edge filter. It may be a coloured glass filter having an edge situated at about 550 nm, e.g. filter commercialized by ITOS Gesellschaft fur Technische Optik mbH as filter type OG 550. A coloured glass filter having an edge being closer to the wavelength of the UV light is for example the filter GG 495 of the firm Schott.
In the housing 10 there is arranged an optical system generally designated by 4. This optical system will form an image of a schematically shown object 6 (tooth or jaw) on an image converter 8. The image converter 8 can be provided in the form of a colour-CCD.
In the angled portion of the housing portion 14 there is arranged a deflection mirror 18 which is arranged under 45° with respect to the axis of the grip portion 12 and to the axis of the window 16. The deflection mirror can be also formed as a deflection prism, e. g. a right angle prism or a pentaprism.
Behind the deflection mirror 18 as seen in the direction of ray propagation, there is a lens 22 having a concave forward end face 24 and a convex rear end face 26.
Under a larger distance from the lens 22 there is arranged an intermediate lens 28, having a convex end face 30 facing the object and a convex end face 32 facing the image sensor.
A further lens 34 being adjacent to the image sensor is arranged under a major distance behind the intermediate lens. It has a convex end face 36 facing the object and a convex end face facing the image converter.
The image converter 8 is arranged on a carriage 40 running on guiding ribs 42, 44 formed on the interior surface of the housing 10 so as to be movable along the axis of the optical system 4. A tooth rack 46 is formed on one of the longitudinal surfaces of the carriage 40. It co-operates with a pinion 48 rotatably journalled in the housing 10 and having a pinion portion projecting through the housing 10 in outward direction. By rotating the pinion 48 the image converter 8 can thus be positioned along the axis of the optical system 4.
An essentially axially extending passage 50 is formed in the housing 10 to receive a light guide 52.
Behind the end of the light guide 52 being remote from the window 17 there is arranged a UW LED 55 emitting ultraviolet light having a wavelength between 390 and 410 nm. Such UV LEDs can be obtained e. g. by the firm ETG as type ETG-3UV400-30. The semi-conductor material used is InGaN which emits in the blue UW. A lens is integrated into the LED and as a result a very narrow light beam is obtained.
An end portion of the passage 50 and the light guide 52 are angled so that light applied to the light guide 52 will exit the light guide 52 in a direction being slightly inclined with respect to the axis of window 17, as shown at 54.
The image converter 8 and the light guide 52 are connected Os to image evaluating electronics by way of a connector arrangement not shown in the drawings (to be thought in the right portion of the figure).
The path of rays of the optical system 4 is shown in more detail in
In addition various rays have been shown which extend from different points from the object 6 to associated points on the surface of the image converter 8.
One sees that with the optical system shown in
Due to the shown arrangement of the three lenses wherein the intermediate lens 28 is spaced as well from the object facing lens 22 as from the lens 34 being adjacent to the image converter by a larger distance, the intermediate lens 28 need not have surfaces of strong curvature. Thus optical aberration is reduced. The fact that in the intermediate lens 28 marginal regions are used, too, will thus not result in a distortion of the image which is not acceptable.
The below table gives a concrete embodiment for putting into practice the optical system 4. The situation corresponds to the representation of
In the table there are given, respectively, the number of the end face (reference numeral of
Where in the column glass an “A” is given, the respective distances are distances, where the optical medium is air. The glass types correspond to the catalogue of optical glasses of the firm Schott.
The embodiment of
In the embodiment of
Thus the image converter 8 can be adjusted along the axis of the optical system 4 without the need of a mechanical acuating means extending through the wall of the housing 10.
In a modification of the embodiment described above the entrance window 16 can be formed as a fully transparent window and an additional colour filter 59 can be arranged on the deflecting mirror 18. This has the advantage, that the filter will be passed twice by the image light. As a still further modification the colour filter 59 can be arranged in front of the carriage 50 as shown in dashed lines or directly in front of the image converter 8.
In the embodiment of
Arranged around the circular entrance window 18 there are four white light LEDs 64. Situated between the latter there are four UV LEDs 66 also equally distributed in circumferential direction.
The white light generating LEDs 64 are connected to an output of an operating circuit 68 which will energize the white light generating LEDs selectively for continuous operation or for periods of operation.
In similar manner the UV generating LEDs 55 are connected with an operating circuit 70 energizing the UV LEDs for short spans of time, respectively.
Control of the operating circuit 70 is by means of a timer 72, which in addition to first and second activating pulses supplied to the operating circuit 70 and eventually 68 (if operated in intermittent mode as assumed here) will provide further control pulses being displaced in phase. These will thus be provided at times, wherein the UV LEDs (and eventually the white light generating LEDs if intermittently energized) will not be working.
The timing pulses and the control pulses of the timer 72 are supplied to a computing circuit 74. The latter has an input being connected to the output of the image converter 8. Each time that the timer 72 will receive a first activating pulse it will load from an image memory 76 co-operating therewith the fluorescence image integrated up to the respective moment and will add the image just received from the image converter 8 amplitudewise. Thereafter the thus obtained total image will be again stored in the image memory 76.
Each time when the timer 72 receives a second activating pulse it will load from the image memory 76 connected thereto a white light image integrated up to the respective moment and will add to this image amplitudewise the image just received from the image converter. Thereafter the total image thus obtained will be again stored in the image memory 76.
If the computing circuit 74 receives a control pulse it also loads the contents of the image memory 76 (fluorescence image and white light image) and will subtract therefrom the amplitudes of the image received from the image converter 8 and will store back the thus obtained new total image into the image memory 76.
One recognizes that thus the image memory 76 will contain a fluorescence image only showing the fluorescence due to the bacteria, the underground being formed by environmental light having been subtracted.
The same holds for the white light image.
The contents of the image memory 76 can be represented on a monitor 78.
In a variant of the embodiment of
Subtraction of the underground image is achieved for the further sets of UV LEDs as has been described above.
In addition one can additively or subtractively combine the images obtained with the different sets of the UV LEDs in view of making visible structures in the thick tissues.
In the embodiment of
Only the most important components of the camera are shown. For diagnosing regions, where the optical access is very difficult, like a deep crevice, the paranasal sinus, the ear or the fissure of the tooth root a fibre optic system will be used instead of a lens optic system. Such is schematically shown at 80.
The UV LED 55 illuminates the rear end of the fibre optics 80 via a dichroitic beam divider 82 and a wavelength dispersive layer 84. The image light returning via the fibre optics 80 is supplied to the image converter 8 via the beam divider 82. The image converter 8 is only required to have one pixel for detecting the light and can be formed e. g. by a light sensitive diode or a photo transistor.
In the camera shown in
The returning image forming light will run back through the fibre optics 80 and will reach the image converter 8 via the dichroitic layer 84.
If desired, the fibre optics 80 may comprise two separate fibre bundles one of which guides the UV light propagating towards the region to be diagnosed and the other of which guides the image forming light returning from the region to be diagnosed.
In the case of contaminations of the region to be diagnosed, e. g. contaminations in a fissure of the toothroot, it can be advantageous to keep contaminants like blood away from the region to be diagnosed. In such case a hollow fibre 86 can be provided extending parallel to the fibre optics 80 to pump a rinsing liquid to the region to be diagnosed.
In a further variant the fibre optics 80 can be designed such that it will simultaneously form a fluid passageway through which a rinsing liquid can be directed to the region to be diagnosed.
In such case the liquid is supplied to a transverse bore provided at a connecting end of the fibre optices.
Due to its high sensitivity the camera described above is well suited to make use of the autofluorescence of bacteria for discerning healthy and sick portions of tissue. It should be noted that this camera can also be used, when the bacteria have been marked by a fluorescence marker that has been additionally administered. Such markers are preferably supplied to the region to be diagnosed before the diagnosis is made, the marker being contained in a liquid solution. These markers will specifically accumulate at the bacteria to be diagnosed. If a fibre sensor camera is used, the fluorescence marker can be supplied before the diagnosis is made by a fluid passage way of this camera (cavities of these fibre optics or an additional hollow fibre).
The following further variants of the invention are feasable:
Since the intensity of the fluorescence may be very weak and since broad band interfering light may be present, e. g. due to other fluorescent cells or in the form of environmental light, it can be advantageous to use a plurality of photo detectors being sensitive at different wavelengths and to measure the intensity of the interfering signals as well as the intensity of the fluorescence signals to which the interfering signal is also super-positioned and to obtain the fluorescence signal in a subtracting step.
A further possibility to suppress an interfering signal due to environmental light can reside in providing the exciting light in the form of pulses and to integrate the returned intensity during this time and the decay time of the fluorescence signal. During a later interval preferably having the same length the intensity of the interfering light is integrated so that the fluorescence signal can be formed by combining the two precited signals in a subtractive way.
For example a region to be diagnosed is illuminated with an ultraviolett to blue semiconductor diode or semiconductor laser diode and the fluorescence is detected using a CCD-camera. To this end the illumination system of the camera described above will be provided with corresponding UV LEDs or laser diodes. A colour glass filter of the edge type (e. g. GG 495 Schott) is arranged in the optical path, which completely absorbs the exciting light and transmits the fluorescence light to the CCD-image converter. Environmental light or other interfering light can be eliminated in a way analogous to the method described above by intermittent provision of the exciting light and simultaneous and non-simultaneous detection of the fluorescence image and the image generated by the interfering light. Another possibility is to periodically switch to optical filters for detecting the intensity of the interfering light and the emission light, respectively.
Also, the image produced by the colour-CCD-image converter can be evaluated as to shifts in the colours.
In addition the fluorescence generated by the bacteria can be enhanced by certain substances, which are used to rinse the mouth before the diagnosis. So it is known for example from the photodynamic therapy of cancer that aminolevulinic acid and derivates of this acid are converted into porphyrins in cancer cells, which porphyrins are difficult to decompose in these cells. The same is true for many bacteria. Thus by rinsing the mouth with such a substance the fluorescence signal can be enhanced.
In the application described above using a camera the diagnosis of the complete space region can be made simultaneously. Thus incipient caries diseases at the surfaces of a tooth can be visualized.
However, it is also possible to visualize diseases of the skin like acne, which are caused by bacteria that can be activated optically, or melanoms of the skin, in which the concentration of porphyrin is clearly increased due to a higher rate of metabolism as compared to freckles.
In view of keeping interfering light away from the measuring region a cylindrical or conically formed cap may be arranged on the entrance window of the camera.
Since the currents of the CCD-image converter generated by the light intensities may be small as compared to the dark current of the image converter, a very sensitive detection by the CCD-image converter may require cooling thereof using e. g. a peltier element.
If a disease must be diagnosed in a crevice, where optical acces is a problem, e. g. the paranasal sinus, the ear, or a crevice of the tooth root, the region to be diagnosed is to be illuminated using an endoscope comprising a video camera as described above and an illuminating light source and the region to be diagnosed is filmed, or one limits the diagnose to a local study using a non-imaging system.
The latter may be conceived so as to direct the LED generated light or laser light to the region to be diagnosed using a light guide fibre. A second fibre may extend parallel to this fibre to receive the fluorescence emitted from the region to be diagnosed and transmitting the fluorescence light to a photodetector.
Also it can be advantageous in the case of measurements in a fissure in he a tooth root to keep the region to be studied free from contaminants like blood in view of having optical access to the region of diagnosis. In such case a further hollow fibre can be used to pump a rinsing liquid to the region to be diagnosed.
A further improvement of the invention results in using a single fibre for supplying the illuminating light and for receiving the fluorescence light. In such case a beam divider is provided at the coupling side of the laser light and the detecting side of the fluorescence light, respectively. The image divider may comprise a wavelength dispersive coating such that the blue laser light is transmitted, while the fluorescence light is reflected by 90°.
It is also possible to partly form the fibre as a hollow fibre such that the rinsing liquid is directed through this fibre to the surface to be studied. In such case the liquid must be supplied in the end portion of the fibre facing the laser by means of a lateral bore.
The diagnostic camera referred to above and constructed according to the teachings of the invention can also be used, if the bacteria are marked by an additionally applied fluorescence marker. Such markers are preferably supplied to the region to be studied as a liquid solution and will accumulate specifically at the bacteria to be studied. In the case of a fibre image converter being used the fluorescence marker can be supplied before the diagnosis via the rinsing fibre.
In the case of a high rate of accumulation of the fluorescence marker in the region of diagnosis it is also possible to detect not the fluorescence but the absorption of the fluorescence marker in the region of diagnosis.
Normally, this method of detection is less sensitive than the detection of the fluorescence. This alternative becomes possible by removing those optical components from the diagnostic apparatus which are responsible for colour separation of the emission signals.
Using this method it would be possible to also detect, e. g. discoloured dental tartar clinging to the root of a tooth in a tooth pocket. This method is appropriate e. g. for analyzing the tartar removal rate of a tooth. root in a vector treatment.
Since the absolute fluorescence signal depends amongst others from the coupling efficiency of the optical system, the distance, from which illumination is made, and the surface roughness as well as restoration materials in adjacent regions, the intensity of the disease cannot be easily determined from the absolute fluorescence intensity.
In such case a further improvement of the invention is appropriate. Therein the fact is used, that healthy tooth material also fluoresces under UV illumination. However, the emission spectrum is different. If a disease occurs, the emission spectrum is changed in that a part of the illumination light will be converted in the bacteria or the sick cells into the emission light of different wavelength. This change in the spectrum as compared to the healthy state can be detected using a colour sensitive image converter as a change in colour. This change in colour can be detected using a colour camera as a function of the spatial coordinates and can be represented on a monitor for showing the state of illness. Thus it is not the absolute intensity which is relevant for the diagnosis.
Accordingly, in accordance of the present invention the ratio between intensities of different spectral contributions can be generally used, to obtain a measure for the state of illness. Therein the one spectral contribution represents the reference signal that has not been modified by the disease and the other spectral contributions represents the signal in first line determined by the disease.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2004 024 494.4 | May 2004 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP05/05133 | 3/12/2005 | WO | 00 | 6/26/2007 |
