KR20130019296A - Scanning system and method for oral cavity - Google Patents

Abstract

PURPOSE: An oral scanning system and a scanning method thereof are provided to improve the preciseness of an image by radiating laser light from a laser diode and transmitting the laser light to oral objects from a transmitting part. CONSTITUTION: A laser diode(20) irradiates laser light. A light transmitting part(30) is connected to a front part of a case. A camera unit(40) takes a picture of the light reflected from an object. A lattice mask converts the light irradiated from the laser diode to a lattice pattern. A piezo actuator moves the lattice mask.

Description

Intraoral scanning system and scanning method {SCANNING SYSTEM AND METHOD FOR ORAL CAVITY}

The present invention relates to an intraoral scanning system and a scanning method for scanning a three-dimensional shape of an intraoral tooth.

Currently, as a method for producing dental prostheses such as inlays, crowns, bridges, and the like, a method of casting a metal material or a ceramic material by a lost wax process is employed.

Recently, however, as a method of manufacturing a dental prosthesis instead of the lost wax method, after measuring the oral cavity of teeth and gums using an optical three-dimensional camera, a dental prosthesis is designed and manufactured using a CAD / CAM system. The system of attention is attracting attention. A representative example of this system is the Serec system.

The Serek system performs intraoral measurements of teeth and gums by reading the shape of the teeth directly in the oral cavity using an optical three-dimensional camera.

As an optical three-dimensional camera, the camera which performs the non-contact three-dimensional measurement represented by the phase shift method or the spatial coding method is used. As described above, by using the optical three-dimensional camera and the CAD / CAM system, the dental prosthesis can be produced more efficiently than the lost wax method, and excellent in the accuracy of fit in the mouth. Dental prostheses can be produced.

However, in the conventional optical three-dimensional camera, the triangulation method is used. Therefore, in order to improve the measurement accuracy, it is necessary to enlarge the anticipated angle of the optical axis of a light transmission side, and the optical axis of an imaging side. In order to increase the expected angle, it is necessary to increase the size of the optical three-dimensional camera. However, since the optical three-dimensional camera is inserted into the oral cavity, there is a limit to increasing the size.

A conventional digital camera for intraoral imaging is disclosed in Korean Patent Laid-Open Publication No. 10-2008-0081804.

Conventional intraoral cameras include a camera body comprising a barrel portion inserted into the oral cavity, an intermediate portion connected to the barrel portion, and a grip portion extending from the intermediate portion, a dental instrument fitted to the barrel portion, and a camera installed on the camera body. It includes a liquid crystal display for displaying an image taken by the main body.

However, the conventional intraoral imaging camera only takes a function of photographing a tooth using a digital camera and displaying the photographed image on a liquid crystal display, and thus cannot obtain a 3D stereoscopic image of the tooth.

The present invention has been made to solve the above problems, an object of the present invention is to provide an intraoral scanning system that can obtain a three-dimensional stereoscopic image of the oral cavity, such as teeth and gums.

Another object of the present invention is to provide an intraoral scanning system that is easy to use because the intraoral scanning is possible by reducing the size of the system and holding the handle and turning on the photographing switch installed on the handle.

It is still another object of the present invention to provide an intraoral scanning system capable of improving the precision of a 3D image by allowing a plurality of grating patterns to be projected in parallel to the scan area.

The technical problem to be achieved by the present invention is not limited to the technical problem mentioned above, and other technical problems not mentioned above may be clearly understood by those skilled in the art from the following description. will be.

Intraoral scanning system according to the present invention for solving the above problems is a case, a laser diode installed at the rear of the case to irradiate the laser light, the laser light is generated in the laser diode connected to the front of the case A light transmitting portion for transmitting the light to the object to be measured in the oral cavity, a camera unit for photographing the light reflected from the object to be measured, a grating mask for forming the light emitted from the laser diode into a grating pattern form, and moving the grating mask. And piezo actuators.

The first lens assembly for diffusing the laser light is disposed behind the laser diode of the present invention.

A rear side of the grating mask of the present invention is characterized in that a second lens assembly is arranged which makes laser light parallel light.

The case of the present invention is characterized in that the handle portion is connected to the lower surface, the handle portion is provided with a shooting switch for operating the scanning system.

The light transmitting part of the present invention is connected to the front surface of the case and the tube portion which serves as a passage through the laser light, the measuring nozzle bent at a right angle in the downward direction at the end of the tube portion to scan the object to be measured, and the measuring nozzle A reflector disposed on an upper surface of the reflector to reflect the laser light.

The outer surface of the tube of the present invention is characterized in that the position sensor for detecting the position and position of the light transmitting portion is installed.

The present invention further includes a three-dimensional scanning unit installed at one side of the light transmitting part to obtain three-dimensional coordinates of the object to be measured.

The grating mask of the present invention is characterized in that streaks are formed at regular intervals in the vertical direction, and the grating pattern projected on the scan area can have uniform brightness.

The piezo actuator of the present invention is characterized in that four grid images moved by 0, π / 2, π, and 3π / 2 by moving the grating mask in steps.

The intraoral scanning method of the present invention comprises the steps of making the laser light in the form of a lattice pattern, irradiating the laser light to the measurement object in the oral cavity, photographing the laser light reflected from the measurement object; Moving the grid mask to obtain four pattern images having different phases; and calculating and displaying a three-dimensional image from the four pattern images on the display unit.

In the obtaining of the four pattern images of the present invention, the grid mask is disposed at a first position to obtain a first pattern image, and the grid mask is moved to a second position to obtain a second pattern image moved by π / 2. Obtain a third pattern image shifted by π by moving the grating mask to a third position, and obtain a fourth pattern image shifted by 3π / 2 by moving the grating mask to a fourth position do.

Computing the three-dimensional image of the present invention comprises the steps of completing the phase map by calculating the phase of the four pattern images having different phases, and proceeds continuously from 0 to 2πn + Φ without repeating the calculated phase And converting the phase map, comparing the phase map with a pre-stored reference phase map, calculating a phase difference, and calculating a measurement coordinate (x, y, z) to obtain a 3D stereoscopic image.

The intraoral scanning system according to the present invention configured as described above is irradiated with laser light from the laser diode, the laser beam is transmitted to the object to be measured in the oral cavity in the light transmitting portion, and the light reflected from the object to be measured in the camera unit By taking a picture, a three-dimensional stereoscopic image of an object to be measured in the oral cavity such as teeth and gums may be obtained.

In addition, the intraoral scanning system of the present invention is convenient because the intraoral scanning is possible by holding the handle portion and turning on the photographing switch installed on the handle.

In addition, the intraoral scanning system of the present invention can improve the accuracy of the three-dimensional image by allowing a plurality of grating patterns to be projected in parallel to the scan area.

1 is a perspective view of a scanning system according to an embodiment of the present invention.
2 is a block diagram of a scanning system according to an embodiment of the present invention.
3 is a block diagram of a scanning system according to an embodiment of the present invention.
4 is a block diagram showing the configuration of a scanning system according to an embodiment of the present invention.
5 is a flowchart illustrating a scanning method of a scanning system according to an embodiment of the present invention.
6 is a view showing four grid images according to an embodiment of the present invention.
7 is a diagram illustrating a process of scanning a hemispherical object according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The sizes and shapes of the components shown in the drawings may be exaggerated for clarity and convenience. In addition, terms defined in consideration of the configuration and operation of the present invention may be changed according to the intention or custom of the user, the operator. Definitions of these terms should be based on the content of this specification.

1 is a perspective view of a scanning system according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of a scanning system according to an embodiment of the present invention, and FIG. 3 is a block diagram of a scanning system according to an embodiment of the present invention. to be.

1 and 3, a scanning system according to an embodiment of the present invention includes a case 10, a laser diode 20 installed at the rear of the case 10 to irradiate laser light, and a front of the case. A light emitting unit 30 connected to the light emitting unit 30 to transmit the laser light generated by the laser diode to the object to be measured (tooth and gum) 100 in the oral cavity, and a camera unit to photograph the light reflected from the object to be measured 100 ( 40).

The case 10 is an exterior case having a space therein and constitutes an external appearance, and has a small size in which the user can sufficiently carry a scanning system and measure the oral cavity.

The case 10 has a light transmitting part 30 connected to the front side, and the laser diode 20 is installed on the back side of the light transmitting part 30 in a straight line. And, the camera unit 40 is installed on the side of the case 10, the handle portion 50 for the user to hold by hand is installed on the lower surface of the case (10).

Here, the handle 50 is provided with a photographing switch 52 to enable the user to operate the scanning system while holding the handle 50. That is, since the photographing switch 52 is installed at the upper portion of the handle part 50, the photographing switch 52 can be operated by the hand holding the handle part 50, which is convenient to use.

Since the overall appearance of the scanning system is formed as a gun type, it is convenient for a user to grab the handle 50 and insert the light-transmitting portion 30 into the oral cavity to measure the object 100 to be measured. .

The light transmitting part 30 is connected to the front surface of the case 10 and serves as a passage through which the laser light passes, and is bent at a right angle downward from the end of the pipe part 32 to face the object to be measured. The measurement nozzle 36, which is positioned to see and photographs the object 100, and the laser light which is disposed at a predetermined angle on the upper surface of the measurement nozzle 36 and travels along the pipe part 32, is measured through the measurement nozzle 36. A reflector 34 reflecting the light to be transmitted and reflecting the light reflected from the object 100 to be transmitted to the camera unit 40 is provided.

The light transmitting part 30 is provided with a three-dimensional scanning unit 38 for obtaining three-dimensional coordinates of the object 100 to be measured.

Here, the tube part 32 is formed in the shape of a rectangular cylinder whose cross section is rectangular in shape to help the progress of the laser light, and the cross section becomes smaller in the direction connected to the measurement nozzle 36 in the part connected to the case 10. .

And, the outer surface of the tube portion 32 is provided with a position sensor 54 for detecting the current position and posture of the light transmitting portion (30). For example, when measuring the front teeth and the molars when the position of the light transmitting unit 30 is different, the position sensor 54 detects the current measuring position of the light emitting unit 30 to control the signal When applied to the unit 60, the control unit 60 determines the position and posture of the light transmitting unit 30 in accordance with the signal applied from the position sensor (54).

The laser diode 20 is operated according to a signal applied from the laser controller 62 and is mounted at the end of the cylindrical barrel 22 horizontally connected to the rear of the case 10. In addition, inside the barrel 22, first lens assemblies 24 and 26 having a plurality of lenses that enlarge the laser light emitted from the laser diode 20 to fit the scan area are provided.

As an example of assembling the second lens, an aspheric lens 24 and an objective lens 26 may be applied.

Inside the case 10, a lattice mask 70 for making a laser pattern irradiated from the laser diode 20 into a lattice pattern, and a lattice piezo actuator for making four images having different phases by finely moving the lattice mask 70. (Pizeo actuator) 72.

The grating mask 70 has stripes formed at regular intervals in the vertical direction, that is, in the vertical direction, so that the laser light passes through the grating mask 70 to form a grating pattern. In addition, the grating mask 70 allows the grating pattern projected on the scan area to have uniform brightness.

The piezo actuator 72 drives the grating mask 70 according to a signal applied from the piezo actuator control unit 64. The piezo actuator 72 includes a piezoelectric element to drive the grating mask in the direction of the voltage applied to the piezoelectric element.

As such, the piezo actuator 72 is driven to move the grating mask 70 four times to obtain four images, calculate phases using the four images, and use the same to shape the object 100 to be measured. Calculate

A second lens assembly 74 having a plurality of lenses that pass through the grating mask 70 and makes laser light into parallel light having a grating pattern is provided behind the grating mask 70. For example, the chromatic aberration correcting lens may be applied to the second lens assembly.

The prism 76 is installed inside the case 10, and the prism 76 is irradiated from the light projecting portion 30 to the object to be measured and reflected by the object to be measured 100. Refract toward 42).

The camera lens 42 focuses and forms an image for the camera unit 40 to photograph the light refracted by the prism 15.

The camera unit 40 is used as a CCD camera, is operated according to the signal of the camera controller 66, and photographs the light reflected through the prism 76 to obtain an image, the obtained image is obtained by the control unit 60 The 3D shape is calculated and the final 3D image is displayed on the display 68.

A scanning method of a scanning system according to an embodiment configured as described above will be described below.

4 is a block diagram showing a configuration of a scanning system according to an embodiment of the present invention, Figure 5 is a flow chart showing a scanning method of the scanning system according to an embodiment of the present invention.

First, the user grasps the handle 50 and inserts the light-transmitting portion 30 into the oral cavity, and then matches the measurement nozzle 36 to the position of the tooth to be measured.

Thereafter, when the photographing switch 52 installed in the handle part 50 is operated, the scanning system is driven to scan the object 100 in the illumination to display a three-dimensional image of the object 100 on the display 68. Is displayed.

Specifically, the laser diode 20 is operated according to the signal applied from the laser controller 62 to irradiate the laser light from the laser diode 20 (S10).

Then, the laser light irradiated from the laser diode 20 is extended while passing through the first lens assemblies 24 and 26, and made into light in the form of a lattice pattern while passing through the grating mask 70, and the second lens assembly 74. By parallel light) (S20)

Then, the light is reflected by the reflector 34 and is projected to the object 100 through the measurement nozzle 36. (S30) And the light reflected from the surface of the object 100 is reflected to the reflector 34 After re-reflection, the light is transmitted to the camera unit 40 by the prism 76, and the camera unit 40 captures the light reflected by the prism 76 to obtain a grid pattern image.

Then, the control unit 60 synthesizes the image photographed by the camera unit 40 and the grid pattern image having no pre-stored change. Combining two pattern images with the same wavelength causes interference between the patterns, resulting in a greater difference in brightness of light than the original pattern, and generating different patterns at regular intervals, which are called moire patterns.

The moiré pattern enables the height information of the object to be measured to obtain three-dimensional data.

However, since the height of a perfect object cannot be obtained with only one pattern, the height is calculated by moving the grid pattern three times to obtain four different images to increase accuracy.

That is, when the grating mask 70 is first placed in the first position, the first pattern image 80 as shown in FIG. 6 is obtained, and the piezo actuator 72 is driven to drive the grating mask 70 in the second position. When moved to a position, a second pattern image 82 moved by π / 2 is obtained. When the piezo actuator 72 is driven to move the grating mask 70 to a third position, the third pattern image moved by π. (84), and when the piezo actuator 72 is driven to move the grating mask 70 to the fourth position, the fourth pattern image 86 moved by 3π / 2 is obtained.

7 is a view showing a process of obtaining a 3D image by the intraoral scanning system according to an embodiment of the present invention.

The three-dimensional shape is calculated using the four images thus obtained: 1) pattern transparency, 2) phase wrap, 3) unwraped phase, and 4) phase-to-height. height conversion).

1) pattern projection

Equation 1 below represents an intensity of light in the first pattern image 80, the second pattern image 82, the third pattern image 84, and the fourth pattern image 86.

Ⅰ ₁ = a (x, y) + b (x, y) cos [Φ (x, y)]

Ⅰ ₂ = a (x, y) + b (x, y) cos [Φ (x, y) + Π / 2]

Ⅰ ₃ = a (x, y) + b (x, y) cos [Φ (x, y) + Π]

I ₄ = a (x, y) + b (x, y) cos [Φ (x, y) + 3Π / 2] .......... Equation (1)

Where I _n = light intensity function of the nth pattern image, a = average intensity of light, b = change in light intensity

If the intensity of the light obtained through the four pattern images by the above equation (1) is put into the equation (2) below, the phase angle Φ (x, y) can be obtained and the height of the measured object can be calculated.

Φ (x, y) = tan ^-1 [I ₄ (x, y) -I ₂ (x, y) / I ₁ (x, y) -I ₃ (x, y)] ....... . (2)

2) Phase wraping

The phase angle obtained by Equation (2) is periodically repeated at a magnitude of 0 to 2π.

The phase wrapping diagram shown in FIG. 7 shows a phase image calculated by projecting a fringe pattern onto a plane as a pattern image.

3) Phase unwraping

The wrapped phase information calculated previously performs phase unwraping because the value of 0 to 2π is repeated periodically. That is, the phase unwinding function converts 2π + Φ when a continuous wrapped phase is repeatedly given and when the value of the previous phase exceeds 2π and goes to the next phase Φ. After phase solving, the phase is continuously expressed from 0 to 2πn + Φ without repeating the phase. The released phase is then proportional to the height of the object.

4) Phase-to-height conversion

The phase difference is obtained by calculating the difference between the phase map and the pre-stored reference plane phase map calculated for each pixel, and the Z coordinate is calculated because the phase difference is proportional to the height value in the Z direction of the measurement object. The y value is also calculated.

Through this process, a 3D image is obtained, and the 3D image is displayed on the display unit 68.

In the foregoing, the present invention has been described in detail based on the embodiments and the accompanying drawings. However, the scope of the present invention is not limited by the above embodiments and drawings, and the scope of the present invention will be limited only by the contents described in the claims below.

10: case 20: laser diode
22: barrel 24, 26: first lens assembly
30: floodlight 32: tube
34: reflector 36: measuring nozzle
40: camera unit 42: camera lens
50: handle 52: shooting switch
60: control unit 62: laser control unit
64: piezo actuator control unit 66: camera control unit
68: display unit 70: grid mask
72: piezo actuator 100: measured object

Claims (12)

case;
A laser diode installed at the rear of the case to irradiate laser light;
A light transmitting part connected to the front of the case and configured to transmit the laser light generated by the laser diode to a measurement target in the oral cavity;
A camera unit for photographing light reflected from the object to be measured;
A grating mask for making light irradiated from the laser diode into a grating pattern form; And
And an piezo actuator for moving the grating mask. The method of claim 1,
And a first lens assembly configured to diffuse laser light behind the laser diode. The method of claim 1,
And a second lens assembly arranged behind the grating mask to produce laser light into parallel light. The method of claim 1,
The case is connected to the handle portion on the lower surface, the intraoral scanning system, characterized in that the shooting switch for operating the scanning system is installed. The method of claim 1,
The light transmitting portion is connected to the front surface of the case and the tube portion that serves as a passage through the laser light, the measuring nozzle bent at a right angle in the downward direction at the end of the tube portion to scan the object to be measured, the upper surface of the measurement nozzle An intraoral scanning system comprising a reflector disposed at and reflecting laser light. The method of claim 5,
Intraoral scanning system, characterized in that the position sensor is installed on the outer surface of the tube to detect the position and position of the light transmitting portion. The method of claim 5,
And a three-dimensional scanning unit installed on one side of the light transmitting part to obtain three-dimensional coordinates of the object to be measured. The method of claim 1,
The grating mask is striped in the vertical direction at regular intervals, the intraoral scanning system, characterized in that the grid pattern projected on the scan area to have a uniform brightness. The method of claim 1,
And the piezo actuator gradually moves the grating mask to produce four pattern images shifted by 0, π / 2, π, and 3π / 2. Making the laser light into a grid patterned light;
Irradiating the laser light to an object to be measured in the oral cavity;
Photographing the laser light reflected from the object to be measured;
Moving the grating mask to obtain four pattern images of different phases; And
Intraoral scanning method comprising the step of calculating a three-dimensional image from the four pattern image and display on the display. The method of claim 10,
The obtaining of the four pattern images may include obtaining a first pattern image by arranging a lattice mask at a first position, obtaining a second pattern image moved by π / 2 by moving the lattice mask to a second position. And moving the grating mask to a third position to obtain a third pattern image shifted by π, and moving the grating mask to a fourth position to obtain a fourth pattern image shifted by 3π / 2. My scanning method. The method of claim 10,
The calculating of the 3D image may include: calculating a phase of four pattern images having different phases to complete a phase map;
Converting the calculated phase to proceed continuously from 0 to 2πn + Φ without repeating;
Calculating a phase difference by comparing the phase map with a previously stored reference phase map; And
Intraoral scanning method comprising the step of obtaining a three-dimensional stereoscopic image by calculating the measurement coordinates (x, y, z).

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