Intraoral imaging scanner

Abstract

The present invention discloses an intraoral image scanner, which adopts a flat field scanning method and has a high spatial resolution while avoiding the use of an f-θ lens. An intraoral image scanner comprises a laser light source, an optical mechanism for processing a laser beam emitted by the laser light source, a scanning mechanism for moving a light spot formed by the laser beam, a fluorescence collection mechanism for collecting fluorescence excited by an image plate, and a photoelectric conversion mechanism for photoelectric conversion; the optical mechanism comprises a collimating lens, an aperture stop and a focusing lens arranged in sequence, the collimating lens is composed of an aspherical mirror, the focal length of the aspherical mirror is 15 to 25 mm, the diameter of the aperture stop is 5 to 10 mm, and the focal length of the focusing lens is 100 to 180 mm.

Description

Technical Field

[0001] The invention belongs to the field of laser scanning imaging and relates to an intraoral image scanner. Background Art

[0002] Laser scanning imaging specifically refers to recording images through X-rays and using lasers to read images recorded on a flexible imaging plate. Computed X-ray Radiography (CR) has been widely used in the field of medical health. Compared with traditional X-ray photography technology, its main feature is that it uses a flexible, erasable imaging plate (IP) instead of silver halide film, and can store and display image information using a computer. X-rays penetrate objects and irradiate the imaging plate containing light-stimulated phosphors, which will produce a frame of latent image and store it in the imaging plate. When a laser of a certain wavelength (600-700nm) is used for irradiation, the imaging plate will excite fluorescence of a specific wavelength (350-450nm), and its energy distribution characteristics are completely related to the latent image morphology. These fluorescences are collected, converted into electrical signals and digitized, thereby converting the latent image into a two-dimensional digital image that can be stored and transmitted.

[0003] Intraoral image scanners based on X-ray photography technology (CR) are widely used in the treatment and diagnosis of oral diseases. For example, in the dental industry, CR scanners are commonly used to read tooth profile information on the image plate. At present, intraoral image scanning systems can be divided into flat field scanning systems and curved surface scanning systems. The difference between them lies in the posture of the image plate (IP) when it is irradiated and stimulated by the laser.

[0004] The curved scanning system means that the IP plate is in a curved state during the scanning process. The degree of curvature depends on the configuration of the system. Its purpose is to cooperate with the optical rotation device to avoid the IP plate not being in the optical optimal image plane due to rotation. Figure 1 As shown, the servo motor drives the pentaprism to rotate, and the rotation of the pentaprism drives the rotation of the laser beam, thereby realizing the laser scanning of the IP plate 1'. Figure 1 It can be seen that the IP plate 1' is attached to a curved surface. In order to keep the curvature of the IP plate 1' consistent with the curvature of the curved surface, the fluorescent surface of the IP plate 1' must be pressed by a roller 2' or other means. The pressing method will inevitably reduce the service life of the IP plate. In addition, scratches and other defects caused by pressing will cause doctors to misjudge the image.

[0005] Flat-field scanning system means that the IP plate is flat during scanning. Compared with curved surface scanning, if the optical system is not specially designed, the spatial resolution of the entire oral scanner will be limited. For this reason, the flat-field scanning system is generally equipped with an f-θ lens to solve the large defocus caused by the scanning angle. Figure 2 As shown, it can be seen that the flat-field scanning achieved by the f-θ lens 3' will lead to some difficult-to-solve problems. First, the system becomes complicated and expensive; second, the installation requirements of the f-θ lens 3' are very high, and some slight system processing deviations or assembly deviations will cause the performance of the whole machine to deteriorate; thirdly, due to the use of the f-θ lens 3', the fluorescence collection efficiency of the entire intraoral scanning system will be reduced, affecting the signal-to-noise ratio of the whole machine. Summary of the invention

[0006] In view of the above problems, the present invention provides an intraoral image scanner which adopts a flat field scanning method and has a high spatial resolution while avoiding the use of an f-θ lens.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] An intraoral image scanner comprises a laser light source, an optical mechanism for processing a laser light beam emitted by the laser light source, a scanning mechanism for moving a light spot formed by the laser light beam, a fluorescence collecting mechanism for collecting fluorescence excited by an image plate, and a photoelectric conversion mechanism for photoelectric conversion; the optical mechanism comprises a collimating lens, an aperture diaphragm and a focusing lens arranged in sequence, the collimating lens is composed of an aspherical mirror, the focal length of the aspherical mirror is 15 to 25 mm, the diameter of the aperture diaphragm is 5 to 10 mm, and the focal length of the focusing lens is 100 to 180 mm.

[0009] Preferably, the aspherical mirror is coated with a dielectric film layer.

[0010] Preferably, the laser light source is a single-mode semiconductor laser.

[0011] More preferably, the wavelength of the laser beam emitted by the single-mode semiconductor laser is 635 nm.

[0012] Preferably, the scanning mechanism is a galvanometer system, and the galvanometer system includes a galvanometer motor and a galvanometer driven by the galvanometer motor to deflect within a certain angle.

[0013] Preferably, the fluorescence collecting mechanism comprises a light collector, and the light collector comprises a hollow shell, wherein the shell has a scanning port for facing the image plate and a fluorescence emission port corresponding to the photoelectric conversion mechanism.

[0014] More preferably, the housing further comprises a laser incident port for projecting the laser beam to the scanning port.

[0015] More preferably, the shell has an arc-shaped inner wall, and a UV-enhanced filter membrane is plated on the inner wall.

[0016] More preferably, a portion of the inner wall of the housing is selectively coated with a low-reflection film.

[0017] More preferably, the light collector further comprises a baffle fixedly connected to the housing, wherein the baffle partially blocks the scanning port.

[0018] The present invention adopts the above technical solution, which has the following advantages compared with the prior art:

[0019] The flat field scanning technology is used to avoid squeezing the image plate and increase the service life of the image plate; at the same time, the design of the entire intraoral scanner is simplified. The optical structure with low magnification, long working distance and large focal depth is used to greatly reduce the large defocus caused by the scanning angle, thereby achieving high spatial resolution of the optical system in the entire scanning field of view. The entire optical system avoids the use of f-θ lenses, and the entire optical system becomes simple and low-cost; due to the low magnification, long working distance and large focal depth design of the optical system, the entire intraoral image scanner has a large tolerance, so the spatial resolution of the system is not sensitive to the processing deviation and assembly deviation of the components, so the design tolerance of the components can be relaxed, and the assembly process does not require high-end optical equipment to assist in installation and detection, which greatly reduces the processing and assembly costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solution of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0021] Figure 1 It is a structural schematic diagram of an intraoral image scanner in the prior art;

[0022] Figure 2 It is a schematic diagram of another structure of an intraoral image scanner in the prior art;

[0023] Figure 3 is a three-dimensional schematic diagram of an intraoral image scanner according to an embodiment of the present invention;

[0024] Figure 4 for Figure 3 A side view of the intraoral imaging scanner is shown;

[0025] Figure 5 Schematic diagram of the structure of a fluorescence collection mechanism in an embodiment of the present invention.

[0026] In the above-mentioned figures,

[0027] 1. Laser light source; 10. Laser beam; 2. Optical mechanism; 21. Collimating lens; 22. Aperture; 23. Focusing lens; 3. Scanning mechanism; 31. Galvanometer; 32. Galvanometer motor; 4. Fluorescence collection mechanism; 41. Shell; 411. Scanning port; 412. Laser incident port; 42. Baffle; 5. Photoelectric conversion mechanism. DETAILED DESCRIPTION

[0028] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] This embodiment provides an intraoral image scanner. Figures 3 to 5 As shown, the intraoral image scanner includes a laser light source 1, an optical mechanism 2 for processing the laser light beam emitted by the laser light source 1, a scanning mechanism 3 for moving the light spot formed by the laser light beam 10, a fluorescence collection mechanism 4 for collecting the fluorescence excited by the image plate, and a photoelectric conversion mechanism 5 for photoelectric conversion. The above mechanisms are arranged in sequence along the propagation path of the laser light beam. Specifically, the laser light source 1 emits a laser; the optical mechanism 2 processes the laser light beam 10 emitted by the laser light source 1 (such as collimation, focusing, etc.); the processed laser light beam 10 is reflected to the image plate by the scanning mechanism 3, and at the same time, the scanning mechanism 3 will move accordingly to change the position of the laser light beam 10 irradiating the image plate, that is, changing the position of the scanning light spot formed by the laser light beam 10 on the image plate; the fluorescence collection mechanism 4 is arranged behind the image plate, and the laser light beam 10 will excite and generate fluorescence after irradiating the image plate, and the scattered light generated by the image plate is collected by the fluorescence collection mechanism 4; the photoelectric conversion mechanism 5 is arranged behind the fluorescence collection mechanism, and the collected fluorescence is photoelectrically converted to output a corresponding electrical signal.

[0030] In this embodiment, a single-mode semiconductor laser is selected as the laser light source 1. The wavelength of the laser beam 10 emitted by the single-mode semiconductor laser is 635nm, and the size of the light-emitting surface is constant, about 1-4μm, which has excellent beam quality, ensuring that the entire intraoral impact scanner has good spatial resolution, and this will greatly reduce the difficulty of designing the laser shaping optical path, which will be described in detail below.

[0031] The optical mechanism 2 includes a collimating lens 21, an aperture stop 22 and a focusing lens 23 arranged in sequence. The laser beam 10 first passes through the collimating lens 21 to form a parallel beam. The parallel beam passes through the aperture stop 22 and is focused by the focusing lens 23. In this embodiment, the collimating lens 21 is composed of an aspherical mirror, and the focal length of the aspherical mirror is 15 to 25 mm. Since a single-mode semiconductor laser is selected as the laser light source 1 in this embodiment, the M of the slow axis and the fast axis of the laser 2 Both are close to 1, so only one aspherical mirror is used to collimate the laser. The focal length of the aspherical mirror is 15-25mm, which can perfectly collimate the laser with NA of 0.2, and the aberration is controlled within the diffraction limit; at the same time, the surface of the aspherical mirror is coated with a dielectric film with a transmittance of about 99.5%, thereby ensuring that the laser has sufficient power.

[0032] The aperture diaphragm 22 has a diameter of 5 to 10 mm, thereby increasing the focal depth of the optical system. Specifically, the aperture diaphragm 22 is designed in a circular blade shape, and the interior is blackened, which can effectively control the stray light of the system and more accurately control the NA of the optical system. The intraoral image scanner of the present invention is a flat field scan, so the setting of the aperture size of the diaphragm (3) is very critical. Since flat field scanning will cause light at different angles to have different optical paths, that is, the laser spot size at different spatial positions of the IP plate will have a large difference. In this embodiment, the diameter of the aperture diaphragm 22 is set to 5 to 10 mm, which can better avoid the above problems.

[0033] In this embodiment, the focal length of the focusing lens 23 is 100-180 mm. In order to cover the entire image plate and reduce the scanning angle of the laser, the optical system adopts a long working distance design. However, if the working distance is too long, it will inevitably lead to a larger optical magnification of the entire optical system. Since the size of the light-emitting surface of the single-mode semiconductor laser is constant, about 1-4um, if the magnification of the optical system is too large, the spot size of its image surface will also increase accordingly. Therefore, the intraoral image scanning system of this embodiment uses a focusing lens 23 with a focal length set to 100-180 mm to focus the light beam, that is, to balance the optical magnification and the low scanning angle, and cooperates with a small aperture diaphragm 22 to achieve that the laser spot size is within the diffraction limit within the entire scanning angle, that is, to achieve flat field scanning without an f-θ lens, while achieving high spatial resolution of the intraoral image scanner, that is, within the entire scanning angle range, the laser spot is very small and within the diffraction limit of the optical system.

[0034] The scanning mechanism 3 uses a galvanometer system. The galvanometer system includes a galvanometer motor 32 and a galvanometer 31 driven by the galvanometer motor 32 to deflect within a certain angle. As the galvanometer motor 32 drives the galvanometer 31 to vibrate rapidly back and forth within a certain angle, the reflection angle of the laser beam 10 reflected by the galvanometer 31 also changes accordingly, and the spot position on the image plate also changes accordingly, thereby realizing the scanning of the image plate by the laser beam 10.

[0035] The fluorescence collecting mechanism 4 includes a light collector. Figure 5 As shown, the light collector includes a hollow shell 41, and the shell 41 has a scanning port 411 for facing the image board and a fluorescent outlet corresponding to the photoelectric conversion mechanism 5. The shell 41 is also provided with a laser incident port 412 for the laser beam 10 to be projected to the scanning port 411. The laser incident port 412 is in the shape of a slit, and its shape matches the scanning path of the laser beam 10 on the image board. During scanning, the light collector is placed above the image board, and its scanning port 411 faces the image board. The laser beam 10 reflected by the galvanometer 31 enters the shell 41 from the laser incident port 412 and is projected from the scanning port 411 to the image board for scanning. The fluorescent character scanning port 411 excited by the image board enters the shell 41 and finally exits from the fluorescent outlet.

[0036] Furthermore, the shell 41 of the laser is generally in a parabolic shape, the inner wall of the shell 41 is arc-shaped, and the inner wall is coated with a UV-enhanced aluminum film, which has a reflectivity of about 90% in the fluorescence band (about 400nm) to effectively collect fluorescence. Figure 5 As shown, the shell 41 is composed of two half shells that are parabolic in shape as a whole, and the two half shells are fixedly connected by fasteners such as screws. The inner cavity of the shell 41 is truncated cone-shaped as a whole, and the shell 41 is also truncated cone-shaped as a whole, and the scanning port 411 is located at the end of the shell 41 with a larger inner diameter, the fluorescence outlet is located at the end of the shell 41 with a smaller inner diameter, and the laser incident port 412 is opened on the side wall of the shell 41. In addition, the inner wall of the shell 41 is selectively coated with a low-reflection film locally to solve the problem of uneven images caused by the difference in the excitation angle of the fluorescence in general flat field scanning, and can overcome the unevenness problem caused by flat field scanning. Specifically, the low-reflection film is formed by a low-reflection material coated on a UV-enhanced aluminum film, and the low-reflection material is specifically a material with a reflectivity lower than that of aluminum.

[0037] The light collector further includes a baffle 42 fixedly connected to the housing 41, and the baffle 42 partially blocks the scanning port 411. Specifically, there are two baffles 42, which are arranged in parallel on the end of the housing 41 with a larger inner diameter, and there is a gap between the two baffles 42, and the scanning port 411 is formed at the gap between the two. By providing the baffle 42, the reflected light generated by the laser reflection inside the housing 41 is prevented from being reflected to the IP plate, thereby preventing the occurrence of image non-uniformity caused by re-excitation of the IP plate.

[0038] The laser fluorescence collection efficiency in this embodiment is about 40%, and can achieve uniform collection of fluorescence at different angles, and can achieve very high image uniformity.

[0039] The photoelectric conversion mechanism 5 is a photomultiplier tube. Specifically, the photomultiplier tube is fixedly mounted on the light collector, preferably fixedly mounted on the end of the laser housing 41 with a smaller inner diameter, and facing the fluorescent light outlet on the housing 41. In addition, the photoelectric conversion mechanism 5 can also be a silicon photomultiplier, which includes an avalanche photodiode array, which is composed of a plurality of avalanche photodiodes arranged in an array. The avalanche photodiode array includes at least one row of avalanche photodiodes, and the plurality of avalanche photodiodes constituting the row of avalanche photodiodes are arranged in a direction parallel to the scanning track of the laser beam 10 on the image board.

[0040] The above-mentioned intraoral image scanner has the following characteristics: 1. The laser beam realizes the scanning of the image plate by the vibration of the galvanometer. Applying the galvanometer to the intraoral image scanner will greatly reduce the cost of the system; in addition, compared with the servo motor system, the galvanometer system has the advantages of simple debugging and no need for dynamic balancing, which greatly simplifies the assembly process. 2. The flat field scanning technology is adopted to avoid the system from squeezing the image plate and improve the service life of the image plate; at the same time, the design of the entire intraoral scanner is simplified. 3. The optical mechanism 2 with low magnification, long working distance and large focal depth is adopted to greatly reduce the large defocus caused by the scanning angle, thereby realizing the high spatial resolution of the optical system in the entire scanning field of view. The entire optical system avoids the use of f-θ lenses, and the entire optical system becomes simple and low-cost; due to the low magnification, long working distance and large focal depth design of the optical system, the entire intraoral image scanner has a large tolerance, so the spatial resolution of the system is not sensitive to the processing deviation and assembly deviation of the components, so the design tolerance of the components can be relaxed, and the assembly process does not require high-end optical equipment to assist in installation and detection, which greatly reduces the processing and assembly costs. 4. The light collector is based on a parabolic shape, and the inner wall is coated with UV-enhanced aluminum film, which has a reflectivity of about 90% in the fluorescence band (around 400nm), and can effectively collect fluorescence. The image uniformity problem is achieved by selectively coating some parts of the inner wall of the light collector with low reflectivity materials. 5. A baffle is set at the bottom of the light collector to prevent the reflected light generated by the laser reflection inside the light collector from re-exciting the image plate, thereby avoiding the occurrence of image unevenness.

[0041] The above embodiment is only for illustrating the technical concept and features of the present invention, and is a preferred embodiment, and its purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. An intraoral image scanner, comprising a laser light source, an optical mechanism for processing a laser beam emitted by the laser light source, a scanning mechanism for moving a light spot formed by the laser beam, a fluorescence collecting mechanism for collecting fluorescence excited by an image plate, and a photoelectric conversion mechanism for performing photoelectric conversion; characterized in that: The laser light source is a single-mode semiconductor laser, the wavelength of the laser beam emitted by the single-mode semiconductor laser is 635nm and the size of the light-emitting surface is constant; the optical mechanism includes a collimating lens, an aperture diaphragm and a focusing lens arranged in sequence, the collimating lens is composed of an aspheric mirror, the aspheric mirror is coated with a dielectric film layer, the focal length of the aspheric mirror is 15-25mm, the diameter of the aperture diaphragm is 5-10mm, and the focal length of the focusing lens is 100-180mm; the fluorescence collection mechanism includes a collector, the collector includes a hollow shell, and the inner wall of the shell is selectively coated with a low-reflection film locally; the collector also includes a baffle fixedly connected to the shell, the shell has a scanning port for facing the image plate and a fluorescence emission port corresponding to the photoelectric conversion mechanism, and the baffle blocks a part of the scanning port; the scanning mechanism is a galvanometer system, and the galvanometer system includes a galvanometer motor and a galvanometer driven by the galvanometer motor to deflect within a certain angle.

2. The intraoral image scanner according to claim 1, characterized in that: The housing also has a laser incident port for projecting the laser beam to the scanning port.

3. The intraoral image scanner according to claim 1, characterized in that: The shell has an arc-shaped inner wall, and an ultraviolet enhanced filter membrane is plated on the inner wall.

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