GB2581834A - Process and apparatus for intra-oral holography imaging - Google Patents

Abstract

A holography based method for generating a three-dimensional (3D) volumetric dental arch model, the method comprises: placing a holographic imaging device at least comprising an object and a reference laser beam source and a device capable of recording a holographic image in view to a subject's dental arch; recording at least one holographic image of at least a portion of the subject's dental arch; re-constructing the subject's dental arch holographic image from the recorded image data; and forming a 3D volumetric model of at least a part of the subject's dental arch by using the data of the reconstructed holographic image. In addition, a dental image device may include a light sensor, an ambient light shield. The device may have a mirror device positioned inside the oral cavity with the laser source and image recording means located outside the oral cavity.

Description

Process and Apparatus for Intra-Oral Holography Imaging

FIELD OF THE INVENTION

The present invention relates to a holography based method for generating a three-dimensional (3D) volumetric dental arch model, the method comprising: placing a holographic imaging device at least comprising an object and a reference laser beam source and a device capable of recording a holographic image in view to a subject's dental arch; recording at least one holographic image of at least a portion of the subject's dental arch; re-constructing the subject's dental arch holographic image from the recorded image data; and forming a 3D volumetric model of at least a part of the subject's dental arch by using the data of the reconstructed holographic image. In addition, the present invention relates to a dental image device and a holographic dental image scanning system adapted to perform the inventive process.

BACKGROUND OF THE INVENTION

A proper alignment of teeth in the dental arch of a patient isn't just a matter of aesthetics. The correct teeth position is a fundamental pre-requisite for an adequate health condition and, in addition, may also affect other dental illnesses like periodontal disease or dental caries. The latter may, at least in part, be caused or favored by teeth misalignment, resulting in difficult to handle cleaning situations in-between the teeth. Therefore, since the early days of dentistry there has been a lot of attempts and different treatment procedures directed to achieve a "natu- -2 -ra1" and correct teeth alignment Some of the treatment options included simple wooden spatulas designed to apply physical pressure to a position of a single tooth or fixed dental braces, wherein the braces are able to treat simultaneously a complete dental arch. In the last years a new treatment option appeared on the market also based on applying physical forces to distinct teeth regions. The concept uses aligners, i.e. polymeric shells which can be placed over the dental arches, and the aligners are configured to move one or more tooth from a misaligned to a correct position. The aligners are individually designed and processed and enable the dentist to perform complex treatment plans. The starting point of the treatment includes the assessment of a model of the actual teeth configuration and based on this model one or more intermediate tooth configurations are planned until the final, correct alignment is achieved. For the assessment of the initial tooth configuration different processes are known. A standard method includes the use of a negative alginate or gypsum mold taken from the patient teeth, which is transferred into a positive model, digitized and used for aligner manufacture. The assessment of the correct actual teeth configuration is of utmost importance, because this configuration forms the starting point and determines the selection of the best treatment path and, in consequence, the potential treatment outcome.

Several different methods for assessing a patient tooth configuration are disclosed in the patent literature.

WO 2018/087363 Al for instance relates to an intraocular scanner for forming digital dental impressions in dentistry, comprising: at least one hand-held device which is designed for detecting digital tooth shape data of at least one tooth of a patient by means of handling an operator; an electronic evaluation module which is connected to the at least one hand-held device and which is configured for generating a digital dental impression based on the detected digital tooth shape data of the at least one tooth of the patient; at least one set of projection glasses, which is a glasses structure that can be worn in front of the eyes of the operator and which is designed to generate a projection of virtual images in the field of vision of the user wearing the projection glasses; and an electronic projection module, which is configured to project a projection of the digital dental impression as a virtual image in the field of vision of the operator wearing the projection glasses by means of the projection glasses and based on the generated digital dental impression, characterized in that the projection module is also configured to project a projection of an operating menu having a plurality of operating fields as a virtual image in the field of vision of the operator wearing the projection glasses by means of the projection glasses, wherein at least one operating field is assigned at least one control command provided for controlling the intraoral scanner, and the at least one set of projection glasses has at least one sensor for detecting hand movements, hand-held device movements and/or eye movements of the operator wearing the projection glasses, wherein an electronic control module is provided which is designed to recognize a hand movement, hand-held device movement and/or eye movement as the actuation of an operating field of the operating menu projected in the field of vision of the operator depending on the detected hand movement, hand-held device movement and/or eye movement, and which is configured to carry out the control command associated with the actuated operating field.

US 2018/0028063 Al describes methods and apparatuses for generating a model of a subject's teeth. Described are intraoral scanning methods and apparatuses for generating a three-dimensional model of a subject's intraoral region (e.g., teeth) including both surface features and internal features. These methods and apparatuses may be used for identifying and evaluating lesions, caries and cracks in the teeth. Any of these methods and apparatuses may use minimum scattering coefficients and/or segmentation to form a volumetric model of the teeth.

Another patent document, US 2015/0348320 Al, disclose a method for measuring regions of a tooth in a mouth including: measuring at least one surface point on a surface of the tooth with respect to an element mechanically coupled to said surface point; determining a location of at least one visible reference mechanically coupled to said surface point with respect to said element; estimating a location of said surface point with respect to said visible reference. A -4 -device used for such measuring may include a main body comprising a final optical element of an imager which defines an optical field of view directed in a first direction; and a measurement element coupled to said main body extending generally in said first direction; Where a tip of said measurement element is sized and shaped to be inserted between a tooth and adjacent gingiva; Where said optical field of view is sized to image at least part of a tooth.

Nevertheless, besides the already existing methods for the determination of patient tooth configurations there still exist the need for further elaborated methods, which are able to precisely and reliably access the teeth position within a patient's oral cavity.

SUMMARY OF THE INVENTION

The present invention has the object of providing a fast, precise and patient friendly method for assessing a dental arch configuration and building a dental model therefrom. In addition, it is an object of the present invention and to solve at least in part some the shortcomings of the prior art by the method according to claim I, the device according to claim 7 and the system according to claim 15 Preferred embodiments of the invention are disclosed in the dependent claims.

It is within the scope of the invention to disclose a holography based method for generating a three-dimensional (3D) volumetric dental arch model, the method comprising: - placing a holographic imaging device at least comprising an object and a reference la-ser beam source and a device capable of recording a holographic image in view to a subject's dental arch; - recording at least one holographic image of at least a portion of the subject's dental arch; - re-constructing the subject's dental arch holographic image from the recorded image data; and -5 - -forming a 3D volumetric model of at least a part of the subject's dental arch by using the data of the re-constructed holographic image.

Surprisingly it was found that above disclosed method is able to assess in an easy, fast and highly accurate way the teeth status of a patient and, additionally, to transform the teeth status into a 3D volumetric model. Without being bound by the theory the advantages of the overall method are based, at least in part, on the suitability of the holographic teeth recording. Holography recordings are known for assessing an image of the soft tissue, like the face or the body, of a patient, but have not been used in the field of imaging teeth structures. It has surprisingly been found that the teeth structures in the oral cavity can precisely be resolved even under less than optimal lighting conditions and that also small movements of the patient during recording are not affecting the quality of the image outcome that much. The holography recording can be obtained on a very short timescale by taking only a very limited amount of pictures, i.e. in an optimal case only one, easing the situation for the patient during recording. In addition, the information content of only one recording is very huge, resulting in a better resolution compared to standard recording techniques. These advantages can be transferred to the volumetric 3D model, resulting in a model comprising a higher degree of details compared to other imaging devices. In addition, the inventive method results in 3D models comprising less artifacts, because standard imaging techniques usually require stripe light projections, wherein the projection is based on a special illumination pattern on the teeth. In the surrounding of the oral cavity this special illumination patter/technique may result in recording artifacts, which have to be eliminated manually from the model in following process steps. Such artifacts can be avoided completely, by using the inventive holography method.

The method used in this invention is a holography based method. Holography is a practice of making holograms. A hologram is a photographic recording of a light field, rather than of an image formed by a lens, and it is used to display a filly three-dimensional image of the holographed subject. The hologram itself is not an image and is usually unintelligible when -6 -viewed under diffuse ambient light. It is an encoding of the light field as an interference pattern of seemingly random variations in the opacity, density, or surface profile of the photographic medium. When suitably lit by a laser, the interference pattern diffracts the light into a reproduction of the original light field and the objects exhibiting visual depth cues such as parallax and perspective that change realistically with any change in the relative position of the observer. Holography requires the use of laser light for illuminating the subject and for viewing the finished hologram. A microscopic level of detail throughout the recorded volume of space can be reproduced.

The holographic recording is used for generating a three-dimensional (3D) volumetric dental arch model. As used herein, a 3D volumetric dental arch model may include preferably a digital representation of a dental arch in three dimensions, also comprising surfaces and structures within that volume in three dimensions. The model may also include proportion and the relation of teeth to each other and to additional surface features and structures like the gum tissue. For example, a volumetric representation of a tooth may include the outer tooth surface and the surrounding gum tissue. A volumetric model may be digital or physical. A physical volumetric model may be formed, e.g., by 3D printing, or the like from the data obtained in the recording. The volumetric models described herein may comprise tooth and oral cavity surface structures on a length scale of 1 mm, preferably 0.1 mm and even more preferred 0.02 mm. Typical axial resolutions may be in the range of 0.1 -0.5 mm. For the generation of the digital model the data of one or more images can be used.

The method disclosed herein includes placing a holographic imaging device at least comprising an object and a reference laser beam source and a device capable of recording a holographic image in view to a subject's dental arch. This means that the imaging device used according to the invention at least comprises one or more laser beam sources, wherein a laser beam source can be defined as a laser light emitting device or a device capable of transmitting laser light. The different object and reference beam sources may be generated by two inde- -7 -pendent laser emitting devices or it is also possible that the object and the reference beam are generated by the same laser source, wherein the laser light path of the reference and the object beam to the recorded objects are different. For instance, it is possible to use only one laser light source and split the beam into two different beams, wherein the object path and the reference path differ with respect to distance and/or distance and angle relative to the recorded objects. The laser beam sources can be a continuous wave-laser, for instance an Nd:YAGlaser emitting laser light of 532 nm. It is also possible to use an arrangement for short-coherence holography, wherein the short-coherence light source or quasi short-coherence light source having frequency comb characteristic is formed as at least one single frequency comb laser. By means of the frequency comb technology, frequency combs of high quality can be obtained. An example of a frequency comb laser, which can particularly be used for holography on the microscopic and optionally also on the mesoscopic scale, is a monolithic torod al microresonator with an optical delay length in the order of approximately 400 micrometers and a coherence length in the medium one-digit micrometer range at a central wavelength of approximately 1550 nm and a spectral range of approximately 400 nm.

The device capable of recording the holographic image can be an electronic detector, e.g. a monochrome matrix CCD or matrix CMOS camera or a color matrix CCD or color CMOS camera, in a single-chip or multi-chip arrangement. The detector can be a rasterized detector formed by a plurality of camera chips in matrix form, wherein preferably the arrangement of several chip matrices is possible as well, for example one chip matrix for a specific spectral range. It is also possible that the device capable of recording the holographic image is a nonelectronic device, e.g. a standard colloidal film material, wherein silver salts are dispersed. Such material is only able to record one image.

The method disclosed herein includes that the device capable of recording the holographic image is placed in view to a subject's dental arch. The view between the recording device and the dental arch may either be direct or indirect, i.e. it is possible that the dental arch is illumi- -8 -nated by the laser beams and the surface reflected laser light is directly recorded by the recording device. In addition, it is possible that the tooth surface reflected laser light is firstly reflected by a mirror surface and that the mirror reflected light is recorded. It is also possible that several mirrors are used before the tooth surface reflected laser light is recorded. Typical positions with view to the subject's dental arch may be in front of the dental arch outside of the oral cavity, e.g. in front of the patients face or within the oral cavity.

The method includes the recording of at least one holographic image of at least a portion of the subject's dental arch. By using the holography setup including the two laser light sources and the recording device at least one, preferable more than one tooth is pictured. Besides the tooth surface and the relation of different tooth positions at the dental arch the picture can also comprise 3D-surface information about the gum tissue or other parts of the oral cavity. It is also possible and intended, that more than one tooth is recorded. For instance, a complete or nearly a complete arch structure can be recorded by taking one holographic picture, only. Therefore, it is advantageous that at least three, more preferred at least 5 teeth are recorded in one image. It is further possible, that only the one side of the arch, either front or back side, is recoded and the complete model is build based on the combined data of the front-and backside image.

The recording of the holographic image may be performed in a professional surrounding, for instance at a clinic or at a medical practice or surgery. In addition, it is also possible to perform the recoding at home, wherein the recording device is delivered to the patient's home and the recording is performed without the help of a dentist or another professional. For the further processing and model build the images may be send or transferred to another location. Furthermore, it is possible that the recording is performed in a special environment, wherein the special environment is not a medical but a conditioned environment. The conditioned environment may be controlled for instance with respect to the hygienic, humidity or illumination conditions. Furthermore, the conditioned or controlled environment may provide a fixed -9 -or very controlled recoding set-up, restricting the possible positioning variance of the recording device with respect to the patient. Such controlled environment can, for instance, be provided within a -photobox", which is publicly accessible. The photobox is a closed space, wherein the imaging can be performed under controlled conditions. The photobox may comprise, besides the devices necessary for image recoding, a seat, a controlled ambient light source and a communication terminal, adapted to supply user instructions and/or to communicate with the patient. The seat may further be adapted to guarantee a fixed position between the patient and the image recording device. Additional features can be provided by the photo-box. E.g. it is possible to integrate a subject identification procedure, wherein the patient in the photobox is identified. Furthermore, it is possible to provide video assistance during the recording process by a healthcare professional.

Within the disclosed method a re-construction of the subject's dental arch holographic image from the recorded image data is performed. A further step of the presented method includes the re-construction of the dental arch image from the recorded holographic image. This step may be performed by using a reconstruction laser, e.g. a coherent 532 nm laser using in the translation stage a step width of 1 p.m. The re-constructed image may be recorded by any of the above mentioned recording means or by an electronic scanner device. The re-constructed image comprises all the necessary surface information of the patient's dental arch. In principle it is possible to re-construct the complete image or only parts thereof Within the disclosed method a 3D volumetric model of at least a part of the subject's dental arch is formed by using the data of the re-constructed holographic image. After reconstruction, i.e. after transformation of the recorded image data to a holographic image by using a re-construction laser, the data can be used to from a 3D volumetric model of at least a part of the subject's dental arch. It is possible to build a complete model of the full dental arch or to build a model ofjust a part of the recorded arch section. The 3D volumetric model may be a physical model oil may be a digital model. A digital model may include overall tooth size/dimension, position relative to the neighboring teeth, surface defects, surrounding gum tissue, tooth numeration/assignment, tooth axis, surrounding tooth space or the like. The 3D volumetric model may especially be suited to assess differences between the actual tooth position and a desired tooth position. The tooth model can further be used to change tooth positions from an actual to a desired position and be used to process an aligner, e.g. by deep drawing of a polymeric sheet. The overall model can be based on one or more image data

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In a preferred embodiment of the method, for recording the holographic image the object and the reference laser beam source and the image recording device can be placed into the oral cavity. It has been found useful to place the recording device including the laser beam sources into the oral cavity of a patient. This configuration enables the recording of very large portion or the complete inner dental arch structures. Furthermore, this set-up may be able to reduce possible interference of outside light or radiation sources. In addition, based on the close proximity of the recording device and the dental arch high resolution images of the dental arch structures are possible. Such set-up may for instance be achieved by introducing all component together on a carrier device and introducing the carrier device into the oral cavity. Based on the image details it is further possible to extrapolate the not recorded teeth structures and o generate a complete teeth model based on one holographic image, only.

In another preferred aspect of the method the holographic imaging device may comprise a mirror device, wherein for recording the holographic image the object and reference laser beam source and the image recording device are placed outside and the mirror device is placed inside the oral cavity. In this embodiment the complete set-up for image generation and recording is located outside of the oral cavity and the perspective to the dental arch, especially the dental arch inside of the oral cavity, is established via the mirror device. Such set-up may reduce the amount of devices which are placed into the oral cavity and might help to in-crease the patient's acceptance of the recording process. Suitable mirrors may be planar or convex/concave mirrors, adapted to reflect incoming waves to the recording device. Furthermore, it is possible to use a two mirror set-up, wherein the different mirrors are angled and adapted to reflect the image of the upper and lower arch at the same time. In his configuration the complete inner teeth structure and surface of the upper and lower arch can be recorded.

In a further preferred characteristic of the method the holographic imaging device comprises a light-sensor and the light conditions are recorded before and/or during recording. In order to establish a constant optical background, it may be helpful to assess the overall light condition by the help of a light sensor. The sensor may be adapted to measure the overall intensity supplied by the laser light sources, i.e. the sensor may be wavelength specific sensor. It is also possible that the sensor is capable of measuring the overall light intensity and that a recording is halted or postponed in cases, wherein too much ambient or artificial light is detected. It is also possible that the light conditions are recorded as a function of time and that these intensity values are used to normalize the recoded data in order to reduce lighting artifacts.

Within another preferred embodiment of the method the holographic imaging device may comprise a motion-sensor and the position and position changes of the image device are assessed before and/or during recording. Based on the holographic recording set-up the time for image recording is very short. This feature increases the measurement acceptability and also reduces the risk of recording failures based on a relative movement between the dental arch and the recording device. Nevertheless, this risk can even be reduced by recording possible relative movements of the recording device and the dental arch and stop the recording in cases, wherein a certain relative movement threshold is missed. Possible motion sensors may be based on the acceleration of the recording device or based on changes of the relative device position.

-12 -In a further preferred aspect of the method at least two holographic images of different view angles can be recorded for each of the upper and lower dental arch and the 3D volumetric model is generated based on the combination of the holographic images. It has been found useful to generate the volumetric model based on more than one holographic image. The use of more than one image may increase the detail depth of the final model or may include a complete arch model comprising inner and outer arch tooth surfaces. The combination of the holographic images may include a combination of two images of the same or of a different perspective. For instance, it is possible to combine two images from the in-and the outside of the oral cavity. Within this embodiment the complete arch surface structures can be resolved. In addition, it also further possible that by the combination of two or several holographic images the detail depth can be enhanced and the presence of image artifacts reduced.

It is further within the scope of invention to disclose a holographic dental image device for assessing the configuration of a subject's dental arch, wherein the device at least comprises: an object and a reference laser source and an image recording media on a support. For a safe and fast assessment of a dental arch configuration of a patient it has been found useful to use a device, wherein besides the recording medium also the laser light sources are integrated. This may reduce the probability of a mismatch between the laser light beams and the recording medium, and may, in addition, help to keep a constant relative position between the recording medium/laser sources and the teeth. Thus, the holographic picture quality may be increased by using such quipped device. Possible laser light sources and possible recording media are disclosed in the context of the inventive method. By using a suitable mirror set-up the object and reference laser beam ca be generated by one laser light source, only. The support may be adapted to keep the image recording media, e.g. a photographic film, in a fixed position. In case that other recoding media are used, e.g. a CCD-chip, the support may be integrated within the chip.

In a preferred embodiment of the dental image device the image recording media may be selected from the group consisting of photographic films, CCD-devices or a combination thereof. Especially, photographic films have been found useful as recoding media, because this non-electronic media are able to provide a large information density on a very small scale. High quality recordings are possible, providing 3D images comprising a very high surface resolution. In addition, the photographic film recoding medium is durable and cheap. In the class of electronic recording media, the CCD (charge coupled devices)-sensors are preferred, because this recording device class is able to deliver the necessary pixel resolution for high quality holographic images.

Within a further preferred embodiment the image recording media and the object and reference laser source can be adapted to be located within the oral cavity during recording. It has been found that the overall process can be performed in a fast and easy way in cases, wherein the complete set-up is located within the patient oral cavity during the recording process. The device can be fixed by a handle or hand-held from the outside of the oral cavity. This set-up ensures a very efficient recording procedure and limits the overall use of materials for the device. Data processing can also be very fast, because unnecessary data transfer is omitted. In addition, the patient acceptance is very high, because the patient can visually concentrate on the healthcare professional, because most of the recording device is invisible. The overall device can, for instance, be designed in the form of a spoon, wherein the spoon base may comprise the CCD-recording and the light sources are also integrated.

In another aspect of the dental image device the image device may comprise a motion detector. In order to also compensate for possible image device movement related artifacts in the holographic images it has been found useful to also integrate a motion detector in the device. The motion detector may be used to assess the current recording situation and record images only in cases, wherein a stable position of the device without any movement is present.

-14 -In a further embodiment of the dental image device the dental image device may comprise a light sensor. In order to compensate for artificial light artifacts based on a non-stable light environment is has been found favorable to integrate a light sensor on the image device. The light sensor may either assess the overall light intensity or may assess a wavelength dependent light intensity. Based on one or more light intensity threshold values the recording may be started or halted.

Within a further aspect of the dental image device the dental image device may comprise a light shield, wherein the light shield is adapted to exclude ambient light during image recording. In order to assure rather constant lighting conditions during recoding is has been found useful to further integrate a light shield capable of restricting the access of ambient light to the recording device. The light shield may for instance be a box surrounding the recording device except for the light bath of the laser beams. In addition, it may be possible that the light shield surrounds the overall recording or image device and prevents ambient light from entering the oral cavity.

In another characteristic of the dental image device the object and the laser beam source can be a short pulsed diode laser. Especially, the short pulsed laser diodes have been found useful to reproducibly provide detailed images at high resolution. In addition, the power consumption of the diodes is low and therefore it is possible to rung the overall device by a battery pack only. This may be favorable, because the amount of cables or cords for external power supply is minimized.

Within another embodiment of the dental image device the device may further comprise at least one minor surface adjacent to the image recording media. In order to fully explore the large view angle of the holography recording it has been found suitable to enlarge the field vision by adding one or more mirror surfaces besides the recording media and, thus, increase the information amount during recording. The recorded images comprise more data and larger -15 -areas can be modeled by using less recordings. This may also increase the patient's acceptance.

In a preferred embodiment of the dental image device the device may further comprise at least two mirror surfaces adjacent to the image recording media. In order to maximize the viewing/recording angle for a single recording it has been found useful to further include two mirrors beside the recording media. By using such device, it is possible to record a complete dental arch within only one image. This is by far better compared to the standard techniques, wherein several images have to be recorded. Preferably, the mirror images are of the same size and the recording device is symmetrically surrounded by the mirrors. This set-up may further enhance the viewing and recording angle.

Within another characteristic of the dental image device the device may further comprise a light illumination source. It has been proven advantageous to the recorded image quality to further stabilize the light environment during recording by using besides the laser sources another light source. This light source can be diode, adapted to emit light of a specific wavelength range or may be adapted to supply light over the complete visible range. It is preferred that the additional light source emit light of a specific wavelength rang, suitable for enhancing the contrast between the teeth and the other structures of the oral cavity. Such setup is able to deliver images comprising more teeth details.

In addition, it is within the scope of invention to disclose a holographic dental image scanning system adapted to generate a three dimensional (3D) volumetric model of at least a part of a subject's dental arch, the scanning system comprising: - a scanner head capable of being placed into the oral cavity or in front of a dental arch of a subject, - an image recording device adapted to record a holographic image; - one or more short pulsed laser light sources configured to supply at least two different laser light beams adapted to illuminate at least a part of a subject's dental arch; - a holographic read-out device adapted to generate a holographic image from the rec-orded holographic image data and - a processor adapted to generate a 3D volumetric model of the subject's dental arch based on the holographic image.

This dental scanning system is able to deliver a high resolution 3D volumetric model based on a very limited number of images, only. In the best case it is possible that only one image is necessary for obtaining all necessary information of the dental arch tooth status. The system is able to supply data at a very high resolution and this recording technique is less prone to recording artifacts, reducing the amount of digital post-processing. Based on the very short recording times and the chosen components the overall system is very patient friendly, because the system is very small. The recording part can easily be placed in the oral cavity and the recording duration is very short. For the further advantages of the inventive system it is explicitly referred to the advantages of the inventive process.

Claims (11)

1. Claims 1 A holography based method for generating a three-dimensional (3D) volumetric dental arch model, the method comprising: -placing a holographic imaging device at least comprising an object and a reference laser beam source and a device capable of recording a holographic image in view to a subject's dental arch; - recording at least one holographic image of at least a portion of the subject's dental arch; -re-constructing the subject's dental arch holographic image from the recorded im-age data; and - forming a 3D volumetric model of at least a part of the subject's dental arch by us-ing the data of the re-constructed holographic image.
2. 2. Method according to claim 1, wherein for recording the holographic image the object and the reference laser beam source and the image recording device are placed into the oral cavity.
3. 3. Method according to claim 1, wherein the holographic imaging device comprises a mirror device, wherein for recording the holographic image the object and reference laser beam source and the image recording device are placed outside and the mirror device is placed inside the oral cavity.
4. 4. Method according to any one of claims 1 -3, wherein the holographic imaging device comprises a light-sensor and the light conditions are recorded before and/or during re-cording.
5. -18 -Method according to any one of claims 1 -4, wherein the holographic imaging device comprises a motion-sensor and the position and position changes of the image device are assessed before and/or during recording.
6. 6 Method according to any one of claims 1 -5, wherein at least two holographic images of different view angles are recorded and the 3D volumetric model is generated based on the combination of the different holographic image data.
7. 7. Holographic dental image device for assessing the configuration of a subject's dental arch at least comprising: - an object and a reference laser source and - an image recording media on a support.
8. 8. Dental image device according to claim 7, wherein the image recording media is se-t5 lected from the group consisting of photographic films, CCD-devices or a combination thereof
9. 9. Dental image device according to any one of claims 7 -8, wherein the image recording media and the object and reference laser source are adapted to be located within the oral cavity during recording.
10. 10. Dental image device according to any one of claims 7 -9, wherein the dental image device comprises a light sensor.
11. 11. Dental image device according to any one of claims 7 -10, wherein the dental image device comprises a light shield, wherein the light shield is adapted to exclude ambient light during image recording.