Intraoral imaging scanner

Abstract

The present invention discloses an intraoral image scanner, which can reduce stray light and ensure good contrast and spatial resolution. An intraoral image scanner includes a laser, an optical mechanism for processing a laser beam emitted by the laser, a scanning mechanism for forming a movable scanning spot irradiated on an image plate by the laser beam, a fluorescence collection mechanism for collecting fluorescence excited on the image plate, and a photoelectric conversion mechanism for photoelectric conversion, the intraoral image scanner also includes a filtering component for allowing the fluorescence excited by the scanning spot on the image plate to pass through, the filtering component is arranged between the fluorescence collection mechanism and the photoelectric conversion mechanism, and a slit is provided on the filtering component, and the slit is conjugate with the scanning spot irradiated on the image plate.

Description

Technical Field

[0001] The invention belongs to the field of laser scanning imaging and relates to an intraoral imaging scanner based on X-rays. 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] In the dental industry, CR scanners are commonly used to read tooth profile information on the image plate. The performance of intraoral imaging scanning systems is basically divided into three aspects: signal-to-noise ratio, spatial resolution, and contrast. At present, there are certain studies and related improvement methods for the signal-to-noise ratio and spatial resolution of intraoral imaging scanning systems. However, the issue of improving image contrast only stays in the later software processing. However, contrast enhancement through later software processing will lose image details, resulting in a decrease in the spatial resolution of the system. Summary of the invention

[0004] In view of the above problems, the present invention provides an intraoral image scanner, which can reduce stray light and ensure good contrast and spatial resolution.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] An intraoral image scanner comprises a laser, an optical mechanism for processing a laser beam emitted by the laser, a scanning mechanism for forming the laser beam into a movable scanning spot for irradiating an image plate, a fluorescence collecting mechanism for collecting fluorescence excited on the image plate, and a photoelectric conversion mechanism for performing photoelectric conversion. The intraoral image scanner also comprises a filtering component for allowing the fluorescence excited on the image plate by the scanning spot to pass through, the filtering component is arranged between the fluorescence collecting mechanism and the photoelectric conversion mechanism, and a slit is formed on the filtering component, and the slit is conjugate with the scanning spot for irradiating the image plate.

[0007] Preferably, the intraoral image scanner further comprises a filter, and the filter is arranged between the filtering component and the fluorescence collecting component.

[0008] Preferably, the fluorescence collecting mechanism comprises a cylindrical mirror.

[0009] More preferably, the cylindrical mirror is coated with a 350-450nm dielectric film layer.

[0010] More preferably, the NA of the cylindrical mirror is greater than 0.5.

[0011] Preferably, the laser is a single-mode semiconductor laser.

[0012] Preferably, the laser is conjugate with the scanning spot for irradiating the image plate.

[0013] Preferably, the optical mechanism comprises a collimating lens, an aperture stop and a focusing lens which are arranged in sequence.

[0014] More preferably, the collimating lens is composed of a single aspherical mirror, the focal length of the aspherical mirror is 15-25 mm, the diameter of the aperture stop is 5-10 mm, and the focal length of the focusing lens is 100-180 mm.

[0015] Preferably, the scanning mechanism comprises a galvanometer mirror for reflecting the laser beam onto the image plate and a galvanometer mirror motor for driving the galvanometer mirror to deflect within a certain angle.

[0016] The present invention adopts the above technical solution, which has the following advantages compared with the prior art:

[0017] The use of a filtering component with a slit in the intraoral image scanner can effectively suppress various stray lights in the system. The secondary or tertiary fluorescence existing in the intraoral image scanner can be greatly suppressed, ensuring that the intraoral image scanner has excellent contrast and spatial resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] 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.

[0019] Figure 1 is a schematic structural diagram of an intraoral image scanner according to an embodiment of the present invention;

[0020] Figure 2 The theoretical model of laser scanning three points (O1, O2, O3) continuously is shown;

[0021] Figure 3 The actual model of laser continuous scanning of three points (O1, O2, O3) in the prior art is shown;

[0022] Figure 4 for Figure 1 Schematic diagram of an intraoral imaging scanner is shown.

[0023] In the above-mentioned figures,

[0024] 1. Laser; 2. Optical mechanism; 21. Collimating lens; 22. Aperture; 23. Focusing lens; 3. Scanning mechanism; 31. Galvanometer; 32. Galvanometer motor; 4. Scanning path; 5. Cylindrical mirror; 6. Filter component; 61. Slit; 7. Filter; 8. Photoelectric conversion mechanism. DETAILED DESCRIPTION

[0025] 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.

[0026] This embodiment provides an intraoral image scanner with low stray light, thus having good contrast and spatial resolution. Figure 1 As shown in the figure, the intraoral image scanner includes a laser 1, an optical mechanism 2, a scanning mechanism 3, a fluorescence collection mechanism, a filtering component 6, a filter 7 and a photoelectric conversion mechanism 8. The above components and mechanisms are arranged in sequence along the propagation path of the laser beam. Specifically, the laser 1 emits a laser; the optical mechanism 2 processes the laser beam emitted by the laser 1 (such as collimation, focusing, etc.); the processed laser beam passes through the scanning mechanism 3 to form a movable scanning spot, which is irradiated onto the image plate and moves along the Figure 1The scanning path 4 in the image board moves on the image board. This is because the scanning mechanism 3 will move accordingly to make the laser beam irradiate different positions of the image board, that is, to change the position of the scanning spot formed by the laser beam on the image board; the fluorescence collecting mechanism is arranged behind the image board, and the laser beam will stimulate fluorescence after being irradiated on the image board, and the scattered light generated by the image board is collected by the fluorescence collecting mechanism; the filtering component 6 is arranged behind the fluorescence collecting mechanism, and is used to allow the fluorescence excited by the scanning spot on the image board to pass through; the filter 7 is arranged behind the filtering component 6, and is used to filter out the excitation light mixed in the fluorescence and only allow the fluorescence to pass through; the photoelectric conversion mechanism 8 is arranged behind the filter 7, and performs photoelectric conversion on the collected fluorescence and outputs a corresponding electrical signal.

[0027] In this embodiment, the laser 1 adopts 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, about 1~4μm, and the M of the slow axis and the fast axis of the laser is 2 They are all close to 1, 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.

[0028] In this embodiment, the optical mechanism 2 includes a collimating lens 21, an aperture stop 22 and a focusing lens 23 which are sequentially arranged along the optical axis of the laser beam. The collimating lens 21 collimates the laser beam to form a parallel beam. Preferably, the collimating lens 21 is composed of a single aspherical mirror. That is, in this embodiment, only one aspherical lens is used to collimate the laser. The laser with an NA of 0.2 is well collimated by the single aspherical mirror, and the phase difference is controlled within the diffraction limit. After passing through the collimating lens 21, the laser passes through the aperture stop 22. The aperture stop 22 is a circular knife-edge design and is blackened internally, thereby effectively controlling the stray light of the system and expanding the focal depth of the entire optical system. The optical mechanism 2 in this embodiment adopts an optical design with a long working distance and a low magnification to achieve a high spatial resolution of the intraoral image scanner, that is, within the entire scanning angle range, the laser spot is very small and is within the diffraction limit of the optical system. The specific description is as follows.

[0029] In this embodiment, the collimating lens 21 is composed of an aspherical mirror, and the focal length of the aspherical mirror is 15-25 mm. Since a single-mode semiconductor laser is selected as the laser light source 1 in this embodiment, the slow axis and the fast axis M of the laser are 2All 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 achieve perfect collimation of lasers with an 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 layer with a transmittance of about 99.5%, thereby ensuring that the laser has sufficient power. The diameter of the aperture diaphragm 22 is 5~10mm, thereby increasing the focal depth 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 5~10mm, which can better avoid the above problems. The focal length of the focusing lens 23 is 100~180mm. 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, the optical magnification of the entire optical system will inevitably increase. 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 100-180mm 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, and at the same time achieve 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.

[0030] In this embodiment, the scanning mechanism 3 includes a galvanometer 31 for reflecting the laser beam onto the image board and a galvanometer motor 32 for driving the galvanometer 31 to rotate. The galvanometer 31 is fixed to the output shaft of the galvanometer motor 32. The galvanometer motor 32 reciprocates within a certain angle, thereby driving the galvanometer 31 to reciprocate within a certain angle. Therefore, the laser spot formed by the laser beam reflected by the galvanometer 31 onto the image board also reciprocates along a track. The track is the scanning path 4 of the laser beam on the image board, as shown in FIG. Figure 1 As shown, each time the galvanometer 31 rotates one stroke, the laser spot completes scanning of one row of the image plate; multiple reciprocating strokes are performed until the laser spot completes scanning of the entire image plate.

[0031] In the present embodiment, the fluorescence collection mechanism is composed of a cylindrical mirror 5, which is used for collecting and focusing, and the generatrix of the cylindrical mirror 5 is parallel or parallel to the scanning path 4 of the laser light beam on the image plate. The cylindrical mirror 5 is arranged in a position adjacent to the image plate, so that it can be arranged close to the image plate, so that more fluorescence can be collected. The cylindrical mirror 5 has a large NA. Specifically, the NA of the cylindrical mirror is greater than 0.5, which increases the fluorescence collection efficiency of the system. The high fluorescence efficiency ensures the signal-to-noise ratio of the intraoral image scanning system. And the surface of the cylindrical mirror 5 is coated with a high-transmittance dielectric film layer of 350-450nm, which has a high fluorescence collection efficiency. In addition, the cylindrical mirror has excellent imaging capabilities on the image plate, and it can image fluorescence emission points such as Figure 4 The fluorescence emission point 92 in the image is imaged without aberration at the slit 61 of the filter component 6.

[0032] In this embodiment, the filter component 6 is disposed between the fluorescence collection mechanism and the photoelectric conversion mechanism 8. A slit 61 is provided on the filter component 6, and the slit 61 is conjugate with the scanning light spot used to irradiate the image plate. Specifically, the filter component 6 can be a thin sheet with a slit 61. The center line of the slit 61 is parallel or juxtaposed with the scanning path 4 of the scanning light spot on the image plate.

[0033] In this embodiment, the filter 7 is disposed between the filtering component 6 and the photoelectric conversion mechanism 8 to filter out the excitation light mixed in the fluorescence after passing through the slit 61 .

[0034] In this embodiment, the photoelectric conversion mechanism 8 includes a photomultiplier tube.

[0035] The intraoral imaging scanner adopts a confocal system, that is, the laser 1, the scanning spot on the imaging plate ( Figure 1 The scanning path 4) and the slit 61 in the image are in a conjugate relationship, thereby achieving low stray light for the entire intraoral image scanning system. The conjugate relationship between the laser 1 and the scanning spot ensures that the spatial resolution of the intraoral image scanner meets the theoretical design. The conjugate relationship between the scanning spot and the slit 61 ensures that only the fluorescence excited at the scanning spot can pass through the slit 61, and the harmful fluorescence signals excited by the secondary or tertiary level will hit other positions of the filter component 6 and cannot pass through the slit 61, thereby suppressing the influence of stray light on the contrast and spatial resolution of the image. The confocal system uses a slit 61 to suppress stray light, and the size of the slit 61 is the diffraction limit size of the collection optical system. The slit 61 and the image plate (scanning path 4) are in an optically conjugate position, and the laser and the image plate (scanning path 4) are in an optically conjugate position.

[0036] Combine the following Figures 2 to 4 The principle of the above confocal system is explained.

[0037] The basic principle of traditional intraoral image scanners is: the laser passes through a collimator and a focusing lens and then hits a prism (triangular prism or pentaprism). The prism is rotated to rotate the laser beam, thereby realizing the laser scanning of the image plate. During the laser scanning of the image plate, the image plate is excited by the laser to emit fluorescence, which is collected by the laser and enters the photoelectric sensor. This method of fluorescence excitation and collection of the image plate is the method used by image plate scanners in the prior art. This method has problems with stray light intensity and poor image contrast for the following reasons:

[0038] First, the surface of the image plate is not a mirror, but a rough surface, so the laser incident on the image plate will cause a laser glare effect. In theoretical design, in order to ensure the spatial resolution of the intraoral scanning system, the size of the laser spot on the image plate needs to be controlled to be very small, generally at the level of tens of microns. However, due to the rough nature of the image plate surface, a very small laser spot quickly generates a large amount of scattered light near the laser spot after being incident on the image plate surface, and these scattered lights will produce secondary excitation on the image plate. The secondary excited fluorescence is directly harmful to the image quality, not only affecting the spatial resolution of the intraoral image scanning system, but also having a very large impact on the contrast of the original image.

[0039] Second, the general fluorescence collection device is a parabolic mirror coated with a high-reflective film. When the laser is incident on the image plate, a large amount of stray light will be incident on the parabolic mirror, and then reflected back to the image plate by the parabolic mirror, causing three excitations of the image plate. The three-times excited fluorescence will also have a great impact on the spatial resolution and contrast of the image.

[0040] In the theoretical design, the model of laser continuous scanning of three points (O1, O2, O3) should be as follows: Figure 2 , the laser continuously scans the three points O1, O2, and O3, and the fluorescence signals 1, 2, and 3 emitted are independent of each other. However, in the prior art, after O1 is actually excited, due to the glare effect of the laser and the reflection of the inner wall of the collecting parabolic mirror, a large area near point O1 is illuminated by the laser, generating a lot of secondary excitation fluorescence and tertiary excitation fluorescence. These harmful fluorescences cause the fluorescence signals 1, 2, and 3 emitted by points O1, O2, and O3 to affect each other, such as Figure 3 This reduces the spatial resolution and contrast of the intraoral imaging scanner.

[0041] like Figure 4As shown, point 91, point 92 and point 93 represent the fluorescence excitation points on the image plate, and only point 92 is conjugate with slit 61. Among them, point 92 and point 93 are secondary or tertiary fluorescence excitation points. These fluorescence signals damage the contrast and spatial resolution of the image, so they must be effectively filtered out. Since the planes where point 92 and slit 61 are located are in a conjugate relationship, only the fluorescence emitted by point 92 can be imaged at the slit 61 of the filtering component 6. The fluorescence emitted by point 92 is imaged at the slit 61 and reaches the photoelectric conversion mechanism 8 after passing through the slit 61 for photoelectric conversion. Since these secondary or tertiary fluorescence excitation points, point 91 and point 93, do not conform to the conjugate optical system of the cylindrical mirror imaging, point 91 and point 93 are imaged at the non-opening position of the filtering component 6, and therefore cannot pass through the slit 61. Therefore, the conjugate collection imaging system can effectively filter out the secondary or tertiary fluorescence emitted by points 91 and 93, thereby ensuring the contrast and spatial resolution of the intraoral image scanning system.

[0042] The above intraoral imaging scanner has the following features:

[0043] The use of a confocal system in an intraoral image scanner can effectively suppress various stray lights in the system. The secondary or tertiary fluorescence existing in the intraoral image scanning system can be greatly suppressed, ensuring that the intraoral image scanner has excellent contrast and spatial resolution.

[0044] 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, an optical mechanism for processing a laser beam emitted by the laser, a scanning mechanism for forming a movable scanning spot of the laser beam onto an image plate, a fluorescence collecting mechanism for collecting fluorescence excited on the image plate, and a photoelectric conversion mechanism for performing photoelectric conversion, characterized in that: The intraoral image scanner also includes a filtering component for allowing the fluorescence excited by the scanning light spot on the image plate to pass through, the filtering component is arranged between the fluorescence collecting mechanism and the photoelectric conversion mechanism, a slit is provided on the filtering component, the filtering component is a thin sheet provided with the slit, the center line of the slit is parallel to the scanning path of the scanning light spot on the image plate, the size of the slit is the diffraction limit size of the optical mechanism, and the slit is conjugate with the scanning light spot used to irradiate the image plate; the intraoral image scanner also includes a filter, the filter is arranged between the filtering component and the fluorescence collecting mechanism to filter out the excitation light mixed in the fluorescence after passing through the slit.

2. The intraoral image scanner according to claim 1, characterized in that: The fluorescence collecting mechanism includes a cylindrical mirror.

3. The intraoral image scanner according to claim 2, characterized in that: The cylindrical mirror is plated with a dielectric film layer of 350-450nm.

4. The intraoral image scanner according to claim 2, characterized in that: The NA of the cylindrical mirror is greater than 0.

5.

5. The intraoral image scanner according to claim 1, characterized in that: The laser is a single-mode semiconductor laser.

6. The intraoral image scanner according to claim 1 or 5, characterized in that: The laser is conjugate with the scanning spot used to illuminate the imaging plate.

7. The intraoral image scanner according to claim 1, characterized in that: The optical mechanism comprises a collimating lens, an aperture stop and a focusing lens which are arranged in sequence.

8. The intraoral image scanner according to claim 7, characterized in that: The collimating lens is composed of a single aspherical mirror, the focal length of the aspherical mirror is 15-25 mm, the diameter of the aperture stop is 5-10 mm, and the focal length of the focusing lens is 100-180 mm.

9. The intraoral image scanner according to claim 1, characterized in that: The scanning mechanism includes a galvanometer mirror for reflecting the laser beam onto the image plate and a galvanometer mirror motor for driving the galvanometer mirror to deflect within a certain angle.

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