Excitation wavelength reflective shield for enhanced fluorescence

Abstract

The present invention relates to a fluorescence detection device for detecting light-induced fluorescence. The fluorescence detection device comprises a light source configured for emitting excitation light towards a target to be illuminated, the excitation light having a first wavelength range, a light sensor configured for detecting fluorescence emission light emitted by the target in response to the excitation light, the fluorescence emission light having at least one second wavelength range, the at least one second wavelength range being different from the first wavelength range, and a reflective shield configured for maximally reflecting the excitation light having the first wavelength range while minimally reflecting the fluorescence emission light having the at least one second wavelength range.

Description

[0001] 2025PF00036

[0002] 1

[0003] EXCITATION WAVELENGTH REFLECTIVE SHIELD FOR ENHANCED FLUORESCENCE DETECTION

[0004] FIELD OF THE INVENTION

[0005] The present invention relates to a fluorescence detection device for detecting light-induced fluorescence, a quantitative light-induced fluorescence system for detecting plaque on a tooth, and a method for detecting plaque on a tooth.

[0006] BACKGROUND OF THE INVENTION

[0007] Quantitative light-induced fluorescence (QLF) is used, for example, in research or dental professional tools to quantify caries in teeth, but it is also suitable to detect red fluorescent (RF) plaque on teeth. In order to identify and quantify the red fluorescent plaque, the contrast between the red fluorescence of the plaque and the green fluorescence of the teeth is the most important parameter. With an RGB camera having red, green, and blue channels, respectively, typically the red over green (R / G) signal is used to discriminate pixels of the camera image with RF plaque from pixels with no RF plaque.

[0008] A system for measuring or imaging the light-induced fluorescence always comprises the following components: A source of excitation light, a sensor like a camera to capture the fluorescence emission light, and a means to block the excitation light from getting to the sensor, which can be a filter, for example. The latter is required as the fluorescence emission intensity is in general much weaker than the excitation light. If the excitation light were to reach the sensor, the sensor would clip from the high intensity, as the sensor needs to be sensitive to capture the low intensity fluorescence emission. A typical QLF system is provided with light-emitting diode (LED) excitation sources in the wavelength range of from 390 to 420 nm, as in that wavelength range the red fluorescence intensity of RF plaque is maximal. The sensor can be an RGB camera, as it can be useful to get location information of the plaque, e.g., the plaque can be located at the gumline or further towards the middle of the tooth. To block the excitation light, a high-pass filter may be placed in front of the camera, for example blocking wavelengths below 460 nm.

[0009] Typically, QLF system may also have a spacer to keep the distance to the teeth at an optimal distance for field of view and excitation-emission intensities. The spacer can be closed fully around the camera, forming a shield against environmental light which could interfere with the fluorescence light.

[0010] However, fluorescence imaging always suffers from low fluorescence intensities, limiting the sensitivity of the system for red fluorescent plaque. In addition, in intraoral QLF imaging, the integration time cannot be long, as users are typically scanning the teeth with a moving sensor. A video2025PF00036

[0011] 2

[0012] rate of 30 frames per second would be advisable, but to minimize motion blurring from fast movements even shorter camera exposure times would be desired. This limits the fluorescence emission integration time. Alternatively, using intense excitation light could help to maximize the fluorescence intensity, but this also has disadvantages. Next to draining power from the system, high intensities have a risk to overheat the imaging head, which can cause both system failure and user safety issues intra-orally.

[0013] Further, it is desired to stay below a certain maximum of excitation light for photobiological safety.

[0014] Another problem observed with QLF camera systems is that the excitation light may illuminate the target area not fully homogeneously, creating potentially over- and under-exposed areas in the same image.

[0015] SUMMARY OF THE INVENTION

[0016] It is an object of the present invention to provide an improved system that solves at least part of the problems of the state of the art of low fluorescence intensities and inhomogeneous illumination.

[0017] The inventors of the present invention have developed a fluorescence detection device for detecting light-induced fluorescence that provides an increased intensity of detected fluorescence light and an improved illumination intensity, thereby significantly improving the signal-to-noise ratio and the reliability and accuracy of medical diagnoses.

[0018] The object of the present invention is solved by the subject matter of the independent claims, wherein further embodiments are incorporated in the dependent claims.

[0019] The described embodiments pertain to a fluorescence detection device for detecting light-induced fluorescence, a quantitative light-induced fluorescence system for detecting plaque on a tooth, and a method for detecting plaque on a tooth. The embodiments described further may be combined in any possible way. Synergistic effects may arise from different combinations in various ways of the embodiments described further although these combinations might not be described explicitly in detail.

[0020] Further on, it shall be noted that all embodiments of the present invention concerning a method might be carried out with the order of the steps as described, nevertheless this has not to be the only and essential order of the steps of the method. The herein presented methods can be carried out with another order of the disclosed steps without departing from the respective method, unless explicitly mentioned to the contrary hereinafter.

[0021] According to a first aspect of the invention, there is provided a fluorescence detection device for detecting light-induced fluorescence. The fluorescence detection device comprises a light source configured for emitting excitation light towards a target to be illuminated, the excitation light having a first wavelength range, a light sensor configured for detecting fluorescence emission light emitted by the target in response to the excitation light, the fluorescence emission light having at least one second wavelength range, the at least one second wavelength range being different from the first wavelength range, and a reflective shield configured for maximally reflecting the excitation light having2025PF00036

[0022] 3

[0023] the first wavelength range while minimally reflecting the fluorescence emission light having the at least one second wavelength range.

[0024] Thus, in this invention fluorescence sensing is enhanced by adding a selective reflective system, selectively reflecting the wavelengths of the excitation light back that is reflected from the illuminated target. This can be applied to any fluorescence sensing system, but the exemplary application of an intraoral QLF camera is especially advantageous. In detail, the teeth are illuminated by a light source emitting excitation light having a wavelength that is optimized to induce the emission of red fluorescence emission light from plaque layers on the teeth. However, in addition to the red fluorescence emission light from the plaque, also green fluorescence emission light from the teeth is produced, and a significant amount of the excitation light is simply reflected from the teeth. In order to increase the intensity of fluorescence emission light detected by the light sensor, it is preferred to increase the illumination intensity of the teeth with excitation light. This can advantageously be achieved by providing a reflecting shield that selectively reflects only the excitation light while not reflecting the fluorescence emission light. In particular, it is preferred that the reflective shield does not reflect the green fluorescence emission light emitted from the teeth, as this would increase the overall amount of detected green fluorescence emission light, which would deteriorate the ration of red to green fluorescence emission light, which is usually employed for determining whether there is plaque present on the teeth. In addition, for determining the location of plaque on the teeth, it is preferred to only detect fluorescence emission light directly after its emission, without having a plurality of indirect reflections in-between. Therefore, according to the invention, only light having the excitation wavelength is reflected from the reflective shield, but light having the wavelengths of the red fluorescence emission light and the green fluorescence emission light is not reflected by the reflective shield according to the invention.

[0025] In the context of the present invention, the term “maximally reflecting” is to be interpreted broad such that the reflective shield is optimized for reflection in the wavelength range of the excitation light. It is of course not necessary that an ideal reflectivity of 100% is reached, which is only theoretically possible. Reflectivity in the first wavelength range of more than 60%, preferably more than 80%, is sufficient for the advantageous effect of the present invention. Accordingly, the terms “minimally reflecting” or “not reflecting” are to be interpreted broad such that the reflective shield is configured for low reflectivity in the wavelength range of the fluorescence emission light. Low reflectivity can be understood as a reflectivity lower than 40%, preferably lower than 20%. In particular, it is necessary that the reflectivity in the first wavelength range is sufficiently higher than the reflectivity in the second wavelength range. Reflection of the reflective shield in a broad range of wavelengths including the excitation light wavelength may be sufficient, as long as the reflective shield does not effectively reflect the fluorescence emission wavelength range.

[0026] Thus, fluorescence detection, e.g. of red fluorescent dental plaque, is enhanced using a reflective shield which preferably only reflects the wavelength range of the excitation light, which would be in the range of 410 + / - 20 nm for red fluorescence plaque, for example. Reflecting the excitation light2025PF00036

[0027] 4

[0028] can increase the resulting fluorescence intensity as it recycles the light reflected by the teeth. Moreover, it may result in a better distribution of the illumination of the teeth with the excitation light. For comparison, simply using a white shield that reflects all the light has however the disadvantage that also the green fluorescence light of the teeth gets reflected back, which reduces the contrast and therefore the signal -to-noise ratio of the red plaque fluorescence. The specific reflective shield in this invention advantageously solves this problem.

[0029] Therefore, the advantages of a fluorescence detection device for detecting light-induced fluorescence according to the invention are the increase of fluorescence intensity and thus the sensitivity of the system, and the homogenization of the excitation light over the target area. In addition, the fluorescence color contrast is not reduced as a non-selective reflective system like a white reflector would do.

[0030] In an embodiment of the invention, the reflective shield is arranged to at least partially surround the light sensor, and configured for reflecting excitation light, that is reflected from the target, back to the target, thereby increasing an illumination intensity of the target with excitation light. With this arrangement, the excitation light can be most efficiently reflected, and a homogenous illumination of the target can be achieved.

[0031] In an embodiment of the invention, the reflective shield is configured for absorbing fluorescence emission light having the at least one second wavelength range. This may advantageously help to prevent fluorescence emission light that does not directly travel from the target to the light sensor from reaching the light sensor.

[0032] In an embodiment of the invention, the device further comprises an optical filter configured for transmitting the fluorescence emission light having the at least one second wavelength range and for blocking the excitation light having the first wavelength range, the optical filter being arranged to cover the light sensor. This optical filter covering the light sensor therefore prevents the light sensor from being irradiated with excitation light, which might lead to clipping of the sensor due to the high intensity of the excitation light. However, the fluorescence emission light from both the red fluorescence of the plaque and the green fluorescence of the teeth is transmitted through the optical filter to the light sensor to be detected.

[0033] In an embodiment of the invention, the reflective shield comprises a first region and a second region, wherein the first region is covering the light sensor, and the second region is at least partially surrounding the first region. Thus, the first region and the second region can have different absorption, transmission, and reflection properties.

[0034] In an embodiment of the invention, the first region is configured for transmitting the fluorescence emission light having the at least one second wavelength range and for blocking the excitation light having the first wavelength range, and the second region is configured for reflecting excitation light, that is reflected from the target, back to the target. Thus, the first region of the reflective shield can act as an optical filter preventing the light sensor from being irradiated with excitation light,2025PF00036

[0035] 5

[0036] but lets the fluorescence emission light pass to be detected by the light sensor. The second region of the reflective shield that is not covering the light sensor reflects the excitation light back to the target for increasing the illumination of the target with excitation light and therefore increases the fluorescence intensity. As explained before, the terms “transmitting the fluorescence emission light” and “blocking the excitation light” have to be interpreted broad such that no perfect transmission or perfect blocking is required. It may be sufficient if transmission of the fluorescence emission light is significantly higher than transmission of the excitation light.

[0037] In an embodiment of the invention, the reflective shield is configured to reflect the excitation light having the first wavelength range and to transmit the fluorescence emission light having the at least one second wavelength range in both the first region and the second region, and the fluorescence detection device comprises an absorption layer configured to absorb the fluorescence emission light that is transmitted through the reflective shield in the second region. Thus, a simplified reflective shield can be used extending over the whole area of the light sensor and the surrounding regions, which acts as reflector for the excitation light to increase the illumination of the target, and simultaneously prevents the light sensor from excitation light reaching the target. Preferably, fluorescence emission light that does not travel towards the light sensor is absorbed by an absorption layer in regions surrounding the light sensor.

[0038] In an embodiment of the invention, the reflective shield comprises an opening configured for receiving the light source and / or the light sensor. Thus, the light source can be integrated in the reflective shield.

[0039] In an embodiment of the invention, the light source is a light emitting diode having an emission wavelength in the range of from 380 nm to 440 nm. This wavelength corresponds to the excitation wavelength of the light induced fluorescence of the plaque.

[0040] In an embodiment of the invention, the light sensor is an RGB camera configured for detecting red fluorescence emission light and green fluorescence emission light. With such an optical camera, an optical image of the target like a tooth can be provided that comprises an indication about the presence and location of plaque on the tooth.

[0041] In an embodiment of the invention, the reflective shield is a spacer shield configured for contacting the target to form a cavity comprising the light source, the light sensor, and a surface of the target. Thus, the reflective shield keeps the distance to the teeth at an optimal distance for field of view and excitation-emission intensities. The spacer shield can be closed fully around the light sensor and contact the target, forming a shield against environmental light which could interfere with the fluorescence detection device.

[0042] In an embodiment of the invention, the reflective shield has a shape of a truncated cone or pyramid. This provides an optimized shape having the light sensor at the small end of the shield and the target at the wider end of the shield, thereby providing improved reflection of the excitation light back to the target.2025PF00036

[0043] 6

[0044] In an embodiment of the invention, the reflective shield is configured for diffuse reflection of the excitation light. This can advantageously improve illumination homogeneity of the target.

[0045] According to another aspect of the invention, there is provided a quantitative light-induced fluorescence system for detecting plaque on a tooth. The system comprises the fluorescence detection device of any of the preceding embodiments, and a processor, wherein the processor is configured for: controlling the light source to emit excitation light towards a tooth of a user, receiving readout data from the light sensor, determining an amount of red fluorescence emission light and an amount of green fluorescence emission light in the readout data, calculating a ratio of the amount of red fluorescence emission light to the amount of green fluorescence emission light, and providing an indication about a presence of plaque on the tooth based on the calculated ratio.

[0046] This exemplary embodiment used is an intraoral fluorescence camera for detecting plaque on a tooth, but other embodiments are also possible that may comprise a simple fluorescence sensor or more complicated camera systems that employ also white light or other light source imaging systems. Such systems could be also embedded in other devices, such as dental appliances or other appliances.

[0047] According to another aspect of the invention, there is provided a method for detecting plaque on a tooth. The method comprises: providing a quantitative light-induced fluorescence system according to any of the preceding embodiments, controlling the light source to emit excitation light towards a tooth of a user, receiving readout data from the light sensor, determining and amount of red fluorescence emission light and an amount of green fluorescence emission light in the readout data, calculating a ratio of the amount of red fluorescence emission light to the amount of green fluorescence emission light, and providing an indication about a presence of plaque on the tooth based on the calculated ratio.

[0048] Thus, the benefits provided by any of the above aspects equally apply to all of the other aspects and vice versa.

[0049] In summary, the invention relates to a fluorescence detection device for detecting light-induced fluorescence. The fluorescence detection device comprises a light source configured for emitting excitation light towards a target to be illuminated, the excitation light having a first wavelength range, a light sensor configured for detecting fluorescence emission light emitted by the target in response to the excitation light, the fluorescence emission light having at least one second wavelength range, the at least one second wavelength range being different from the first wavelength range, and a reflective shield configured for maximally reflecting the excitation light having the first wavelength range while minimally reflecting the fluorescence emission light having the at least one second wavelength range.

[0050] One of the advantages of embodiments of the present invention is that fluorescence sensing is enhanced by adding a selective reflective system, selectively reflecting the wavelengths of the excitation light back that is reflected from the illuminated target. This has the advantage that fluorescence intensity and thus the sensitivity of the system is increased. Further, illumination with the excitation light2025PF00036

[0051] 7

[0052] over the target area is homogenized. In addition, the fluorescence color contrast is not reduced as a non-selective, e.g. white, reflective system would do.

[0053] These advantages are non-limiting and other advantages may be envisioned within the context of the present application.

[0054] The above aspects and embodiments will become apparent from and be elucidated with reference to the exemplary embodiments described hereinafter. Exemplary embodiments of the invention will be described in the following with reference to the following drawings:

[0055] BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Fig. 1 shows a schematic setup of a fluorescence detection device for detecting light-induced fluorescence according to an embodiment of the invention.

[0057] Figs. 2 to 4 show various configurations of a fluorescence detection device for detecting light-induced fluorescence according to embodiments of the invention.

[0058] Fig. 5 shows a schematic setup of a quantitative light-induced fluorescence system for detecting plaque on a tooth according to an embodiment of the invention.

[0059] Fig. 6 shows an image of a surface of a tooth covered with red fluorescent plaque.

[0060] Fig. 7 shows a block diagram of a method for detecting plaque on a tooth according to an embodiment of the invention.

[0061] DETAILED DESCRIPTION OF EMBODIMENTS

[0062] Fig. 1 shows a schematic setup of a fluorescence detection device 100 for detecting light-induced fluorescence according to an embodiment of the invention. The fluorescence detection device 100 comprises in this embodiment a plurality of light sources 110 that emit excitation light 111 with a first wavelength range towards a target 140 to be illuminated. The fluorescence detection device 100 comprises further a light sensor 120 for detecting fluorescence emission light 141 that is emitted by the target 140 in response to the illumination with the excitation light 111. The fluorescence emission light 141 has at least one second wavelength range which is usually larger than the first wavelength range. Preferably, plurality of different wavelengths can be detected by the light sensor 120. The fluorescence detection device 100 further comprises a reflective shield 130 that is configured for maximally reflecting the excitation light 111, i.e., light having the first wavelength range, while minimally reflecting the fluorescence emission light, i.e., light having the at least one second wavelength range.

[0063] An exemplary embodiment shown in Fig. 1 can be a quantitative light-induced fluorescence camera with a reflective shield that absorbs all wavelengths except the excitation wavelengths, e.g. 380 to 440 nm for an wavelength of the excitation light source of 410 + / - 30 nm. The optical appearance of such a reflective shield would be violet-blue.

[0064] In an exemplary embodiment of violet excitation LEDs at 410 + / - 30 nm, the ideal reflective system reflects wavelengths of 380 to 440 nm. It may also reflect 300 to 440 nm without any2025PF00036

[0065] 8

[0066] issues. For fluorescence imaging of teeth most of the emission starts above 480 nm, so a reflective range of 300 to 480 nm might also work well enough. If wavelengths above the emission wavelengths (e.g. >730 nm) are reflected this is also no issue for the desired effect.

[0067] The wavelengths that should be reflected should be at least most wavelengths emitted by the excitation light 111 of the fluorescent system. Further wavelengths smaller than the excitation light wavelengths may be reflected, this would not harm the function. Reflection of wavelengths higher than the excitation light 111 wavelengths can for the wavelengths close to the excitation wavelengths also be acceptable, but the wavelengths where strong fluorescence emission is expected should be absorbed or transmitted by the reflective shield 130. In this way, the back reflection of fluorescence emission light can be prevented, which is the purpose of this invention.

[0068] In order to both improve the light intensity and the light homogeneity without changing the excitation sources it was tested to change from an original black spacer shield to a white spacer shield acting as reflective shield. The idea behind this was that the excitation light that is reflected from the teeth is recycled by the white shield, as it is reflected back to the teeth. As teeth are highly reflective, a strong gain in light intensity would be achieved, as the excitation light would be recycled multiple times.

[0069] Moreover, the reflection of the excitation light would help to spread and homogenize the light over the target area.

[0070] The use of a white spacer shield enhanced in tests the fluorescence intensity by approximately 50%, confirming the advantage of reflecting the light for enhanced sensitivity. However, these experiments revealed a new problem: the red over green ratio (R / G) also dropped significantly by about 25% when using the white spacer shield. This originates from the fact that there is a strong green fluorescence from the teeth, which is also reflected from the white shield back to the target teeth. This “artificial” green illumination of the teeth is not filtered away with the filter in front of the sensor, and so adds green reflection to red fluorescent plaque spots, reducing the contrast. Therefore, this invention aims to provide an excitation light reflective feature similar to the white shield, while maintaining the highest possible R / G contrast. The R / G contrast is used for determining the presence of plaque on teeth.

[0071] Experiments with a blue reflective shield 130 showed no significant effect on the R / G ratio compared to the black spacer, but showed a significant increase in the fluorescence intensity compared to the black spacer, and therefore showed the proof of principle that a reflective shield 130 according to the invention can lead to a better signal quality. A reflective shield with an reflection spectrum optimized according to the emission wavelength of the light source can therefore advantageously increase the fluorescence intensity and thus the sensitivity of the system.

[0072] The reflective shield 130 should capture as much as possible of the excitation light reflected from the target. This could for example be in the form of a cone-shaped shield, as shown in Fig.

[0073] 1. It could have a very different shape as well, for example rectangular. Preferably, the reflective shield 130 is arranged to at least partially surround the light sensor 120, and is configured for reflecting2025PF00036

[0074] 9

[0075] excitation light 111, that is reflected from the target 140, back to the target 140, thereby increasing an illumination intensity of the target 140 with excitation light 111.

[0076] Preferably, the reflective shield 130 is a spacer shield configured for contacting the target 140 to form a cavity comprising the light source 110, the light sensor 120, and a surface of the target 140. In this cavity, the excitation light 111 can be reflected multiple times between the reflective shield 130 and the target 140, before it causes fluorescence emission light 141 in a fluorescent layer on the target, and the fluorescence emission light 141 is detected by the light sensor 120.

[0077] The material of the reflective shield 130 could be plastic polymers or elastomers containing pigments that reflect the excitation light wavelength range but absorb the higher wavelengths of the fluorescence emission. For pure violet light reflection such a material would appear to have a violet color in white light.

[0078] Preferably, the reflective shield 130 comprises a diffuse reflective layer, which improves a homogenous illumination of the target 140 with the excitation light 111.

[0079] The example used in most embodiments is a fluorescence camera, but other embodiments can be thought off that are a simple fluorescence sensor or more complicated camera systems that employ also white light or other light source imaging. Such systems could be also embedded in other devices, such as dental appliances or other appliances.

[0080] Figs. 2 to 4 show various configurations of a fluorescence detection device 100 for detecting light-induced fluorescence according to embodiments of the invention. In Fig. 2, the reflective shield 130 comprises an opening 112, which receives the light sensor 120 and a plurality of light sources 110 surrounding the light sensor 120. An optical filter 150 is in this embodiment of the invention arranged to cover the light sensor 120 to filter the excitation wavelength and to only transmit the fluorescence emission light of red and green fluorescence. In Fig. 3, an embodiment is shown where the reflective shield 130 comprises a smaller opening 112, and only the light sensor 120 is arranged in this opening 112 of the reflective shield. The light sources may be arranged in separate dedicated openings in the reflective shield 130, or the excitation light 111 of the light sources may be transmitted through the reflective shield 130 from the backside. Also in this embodiment, the light sensor 120 is covered by an absorption filter 150.

[0081] Next to absorbing materials, other embodiments may use specific wavelength range reflecting mirrors or coatings. In fact, the absorption filter 150 used to block the excitation light 111 could be replaced with a reflecting mirror, specifically reflecting only the wavelengths below as certain wavelength, preferably 460nm. In a preferred embodiment, such a mirror may be extending over the full area of the reflective shield and also the light sensor 120 like a camera. The excitation light 111 emission would cross the selective reflective shield 130 from the backside, or maybe through dedicated openings, to illuminate the target. The excitation light 111 reflected from the target would be reflected back to the target by the selective reflective shield 130 so it could be recycled and also does not reach the light sensor2025PF00036

[0082] 10

[0083] 110 or camera. The fluorescence emission wavelengths 141 would nicely pass through the selective reflective shield 130 and get absorbed by an optional black backing or the camera or light sensor 110.

[0084] Such an embodiment is shown in Fig. 4, where the reflective shield 130 is divided into a first region 131 and a second region 132. The first region 131 is covering the light sensor 120, and the second region 132 is at least partially surrounding the first region 131. The first region 131 transmits the fluorescence emission light 141 with the at least one second wavelength, i.e., red fluorescent light and green fluorescent light, and blocks the excitation light 111 with the first wavelength, i.e., blue, violet or near ultra-violet light , and the second region 132 reflects excitation light 111, that is reflected from the target 140, back to the target 140.

[0085] Preferably, the whole area of the reflective shield 130, i.e., the first region 131 and the second region 132, reflect the excitation light 111, and an absorption layer 160 that absorbs the fluorescence emission light 141 that is transmitted through the reflective shield 130 in the second region 132 is provided on a backside of the second region 132 of the reflective shield 130 that is opposite to the target 140. The light sources 110 are arranged in dedicated openings 112 in this embodiment of the invention.

[0086] Next to reflecting mirrors, there are also coatings These coatings may also be used on the reflective shield 130. In this class of embodiments the coating may additionally be placed in front of the light sensor 120 and serve as the reflective layer for the excitation light, as the emitted fluorescence wavelengths will pass through this reflection filter. At the back of such a reflective system, outside the camera opening, should then still be a material that absorbs all the fluorescence emission light coming through the coating, e.g., a black material. The reflection filter should not block the light sources of the fluorescent sensing system, or any other light sources.

[0087] Fig. 5 shows a schematic setup of a quantitative light-induced fluorescence system 200 for detecting plaque 146 on a tooth 145 according to an embodiment of the invention. The system 200 comprises the fluorescence detection device 100 of any of the preceding embodiments, and a processor 170. The processor 170 is configured for controlling the light source 110 of the fluorescence detection device 100 to emit excitation light (111) towards a tooth 145 of a user, receiving readout data from the light sensor 120 of the fluorescence detection device 100, determining and amount of red fluorescence emission light and an amount of green fluorescence emission light in the readout data, calculating a ratio of the amount of red fluorescence emission light to the amount of green fluorescence emission light, and providing an indication about a presence of plaque 146 on the tooth 145 based on the calculated ratio.

[0088] Fig. 6 shows an image of a surface of a tooth 145 covered with red fluorescent plaque 146. In this example, the plaque 146 is positioned close to the gums of a user, while the remaining part of the surface of the tooth is not covered with plaque. Thus, the part of the surface of the tooth 145 close to the gums will provide a red fluorescence if illuminated with excitation light 111, while the uncovered surface of the tooth 145 will provide green fluorescence. This ratio of red fluorescence to green2025PF00036

[0089] 11

[0090] fluorescence is utilized as indication for the presence of plaque 146 in the respective region of the tooth 145.

[0091] Fig. 7 shows a block diagram of a method for detecting plaque on a tooth according to an embodiment of the invention. The method comprises step S 110 of providing a quantitative light-induced fluorescence system 200, step S120 of controlling the light source 110 to emit excitation light 111 towards a tooth 145 of a user, and step S130 of receiving readout data from the light sensor 120. The method comprises further step S140 of determining an amount of red fluorescence emission light and an amount of green fluorescence emission light in the readout data, step S150 of calculating a ratio of the amount of red fluorescence emission light to the amount of green fluorescence emission light, and step S160 of providing an indication about a presence of plaque 146 on the tooth 145 based on the calculated ratio.

[0092] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing a claimed invention, from a study of the drawings, the disclosure, and the dependent claims.

[0093] In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are re-cited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.2025PF00036

[0094] 12

[0095] LIST OF REFERENCE SIGNS:

[0096] 100 fluorescence detection device

[0097] 110 light source

[0098] 111 excitation light

[0099] 112 opening

[0100] 120 light sensor

[0101] 130 reflective shield

[0102] 131 first region

[0103] 132 second region

[0104] 140 target

[0105] 145 tooth

[0106] 146 plaque

[0107] 141 fluorescence emission light

[0108] 150 optical filter

[0109] 160 absorption layer

[0110] 170 processor

[0111] 200 quantitative light-induced fluorescence system

Claims

2025PF0003613CLAIMS:

1. A fluorescence detection device (100) for detecting light-induced fluorescence, the fluorescence detection device (100) comprising:a light source (110) configured for emitting excitation light (111) towards atarget (140) to be illuminated, the excitation light (111) having a first wavelength range;a light sensor (120) configured for detecting fluorescence emission light (141) emitted by the target (140) in response to the excitation light (111), the fluorescence emission light (141) having at least one second wavelength range, the at least one second wavelength range being different from the first wavelength range; anda reflective shield (130) configured for maximally reflecting the excitation light (111) having the first wavelength range while minimally reflecting the fluorescence emission light (141) having the at least one second wavelength range.

2. The fluorescence detection device (100) according to claim 1, wherein the reflective shield (130) is arranged to at least partially surround the light sensor (120), and configured for reflecting excitation light (111), that is reflected from the target (140), back to the target (140), thereby increasing an illumination intensity of the target (140) with excitation light (111).

3. The fluorescence detection device (100) according to any of claims 1 or 2, wherein the reflective shield (130) is configured for absorbing fluorescence emission light (141) having the at least one second wavelength range.

4. The fluorescence detection device (100) according to any of the preceding claims, further comprisingan optical filter (150) configured for transmitting the fluorescence emission light (141) having the at least one second wavelength range and for blocking the excitation light (111) having the first wavelength range, the optical filter (150) being arranged to cover the light sensor (120).

5. The fluorescence detection device (100) according to any of the preceding claims, wherein the reflective shield (130) comprises a first region (131) and a second region (132), wherein the first region (131) is covering the light sensor (120), and the second region (132) is at least partially surrounding the first region (131).2025PF00036146. The fluorescence detection device (100) according to claim 5, wherein the first region (131) is configured for transmitting the fluorescence emission light (141) having the at least one second wavelength range and for blocking the excitation light (111) having the first wavelength range, and the second region (132) is configured for reflecting excitation light (111), that is reflected from the target (140), back to the target (140).

7. The fluorescence detection device (100) according to any of claims 5 or 6, wherein the reflective shield (130) is configured to reflect the excitation light (111) having the first wavelength range and to transmit the fluorescence emission light (141) having the at least one second wavelength range in both the first region (131) and the second region (132), and wherein the fluorescence detection device (100) comprises an absorption layer (160) configured to absorb the fluorescence emission light (141) that is transmitted through the reflective shield (130) in the second region (132).

8. The fluorescence detection device (100) according to any of the preceding claims, wherein the reflective shield (130) comprises an opening (112) configured for receiving the light source (110) and / or the light sensor (120).

9. The fluorescence detection device (100) according to any of the preceding claims, wherein the light source (110) is a light emitting diode having an emission wavelength in the range of from 380 nm to 440 nm.

10. The fluorescence detection device (100) according to any of the preceding claims, wherein the light sensor (120) is an RGB camera configured for detecting red fluorescence emission light and green fluorescence emission light.

11. The fluorescence detection device (100) according to any of the preceding claims, wherein the reflective shield (130) is a spacer shield configured for contacting the target (140) to form a cavity comprising the light source (110), the light sensor (120), and a surface of the target (140).

12. The fluorescence detection device (100) according to any of the preceding claims, wherein the reflective shield (130) has a shape of a truncated cone or pyramid.

13. The fluorescence detection device (100) according to any of the preceding claims, wherein the reflective shield (130) is configured for diffuse reflection of the excitation light (111).

14. A quantitative light-induced fluorescence system (200) for detecting plaque (146) on a tooth (145), comprising:2025PF0003615the fluorescence detection device (100) of any of claims 1 to 13; anda processor (170);wherein the processor (170) is configured for:controlling the light source (110) to emit excitation light (111) towards a tooth (145) of a user,receiving readout data from the light sensor (120),determining and amount of red fluorescence emission light and an amount of green fluorescence emission light in the readout data,calculating a ratio of the amount of red fluorescence emission light to the amount of green fluorescence emission light, andproviding an indication about a presence of plaque (146) on the tooth (145) based on the calculated ratio.

15. A method for detecting plaque (146) on a tooth (145), the method comprising:providing (SI 10) a quantitative light-induced fluorescence system (200) according to claim 14;controlling (S120) the light source (110) to emit excitation light (111) towards a tooth (145) of a user;receiving (S130) readout data from the light sensor (120),determining (S140) an amount of red fluorescence emission light and an amount of green fluorescence emission light in the readout data,calculating (SI 50) a ratio of the amount of red fluorescence emission light to the amount of green fluorescence emission light, andproviding (S160) an indication about a presence of plaque (146) on the tooth (145) based on the calculated ratio.

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