WO2018124724A1 - Scanner device and scanning method therefor - Google Patents

Abstract

A scanner device according to one embodiment of the present invention comprises: a light source for emitting light to an object to be measured; an optical system for receiving the light reflected from the object to be measured; a camera for photographing a cross section of the object to be measured by means of the reflected light received by the optical system; a depth control unit for controlling a focus adjustment for a liquid lens included in the optical system by means of an AC pulse; and a main control unit for controlling the camera and controlling a focusing interval setting value on the object to be measured in the depth control unit. According to one embodiment of the present invention, the three-dimensional scanner device can effectively obtain durability and operational reliability in the scanner device for reducing vibration and noise due to non-driving since a non-driving optic system is applied for the focus adjustment.

Description

Scanner device and its scanning method

The present invention relates to a scanner apparatus and a scanning method thereof.

In general, a dental clinic or the like performs treatment and care for a patient's damaged tooth through an impression taking process of producing a plaster model of the patient's teeth. As a supplementary method, X-rays such as X-rays were projected onto the affected area of the oral cavity to obtain a two-dimensional screen, or computer tomography (CT).

However, this approach causes a lot of inconvenience for the patient. In order to make a plaster model, you need to wait for more than a certain period of time with a mold containing semi-solid gypsum in your mouth.If the patient does not bite correctly or the frame moves while biting, an accurate model of the patient's teeth will not be made. You may not be able to. In addition, an error may occur according to the skill of the operator, and even if the frame is made correctly, an error may occur during the process of making a model according to the frame in the technician.

In particular, since several patients use a plaster mold or the like, hygiene may occur when disinfection is not sufficiently performed. Accordingly, in recent years, a technique for actively measuring the shape and condition of the patient's teeth by scanning / photographing the tooth state inside the patient's mouth using physical devices without physical contact has been actively studied.

An object according to an embodiment of the present invention is to eliminate the need for physical movement and driving means for focusing by applying a non-driven optical system when driving a scanner device, thereby improving the operation performance of the scanner with no noise and vibration during the actual scanning process. It is an object of the present invention to provide a scanner device and a scanning method capable of more effectively securing driving reliability.

The present invention also provides a scanner device and a scanning method capable of precise 3D scanning according to the shape and structure of a target object by more precisely controlling the setting of the tomography interval according to the target object during tomography for 3D scanning.

According to an embodiment of the present invention, a scanner apparatus includes a light source for irradiating light onto a measuring object, an optical system for receiving the light reflected by the measuring object, and photographing the end surface of the measuring object by the reflected light received by the optical system. A camera, a depth control unit for controlling the focus control of the liquid lens included in the optical system through the AC pulse and the camera, and the depth control unit includes a main control unit for controlling a focusing interval setting value for the measurement object.

The main controller may further include a driving controller for driving the light source and a database storing pre-standard image information of the measurement object corresponding to the cross-sectional image information of the measurement object photographed by the camera. The focusing interval setting value of the depth controller may be controlled by matching the cross-sectional image information provided by the camera and pre-standard image information of the measurement object.

The depth controller may apply the AC pulse onto the liquid lens, and may vary at least one of the amplitude, frequency, and duty of the AC pulse according to the measurement distance of the measurement object or the appearance gradient of the measurement object. have.

The apparatus may further include a 3D image output unit which receives the cross-sectional image data of the measurement object obtained by the camera from the main controller and converts the cross-sectional image data into a 3D image.

In addition, the main control unit, if the measurement object is an oral tooth, the database stores the image of the standard tooth, and compares the image obtained by the camera with the image of the standard tooth to determine the tooth type The depth control unit may be controlled by a focusing interval set value set according to a range of inclination of the outer cross section of the tooth according to the tooth type.

In addition, the optical system may further include a polarizing filter coupled to one end.

According to another aspect of the present invention, there is provided a scanning method of a scanner device, the method including: (A) irradiating light to a measurement object with a light source, (B) receiving light reflected from the measurement object, and including an optical system including a liquid lens. Scanning according to a focusing interval setting value by a depth control unit for adjusting a focus of the liquid lens; (C) a camera through a main control unit for each end face of the measurement object scanned by the optical system according to the focusing interval setting value; Photographing with; And (D) transmitting the image photographed by the camera to the 3D image output unit through the main controller and converting the image photographed by the camera into a 3D image by the 3D image output unit.

Herein, after the step (D), when the converted 3D image is indeterminately determined, the step (B) is performed by the main controller to further refine the focusing interval setting value. Controlling and scanning, wherein (C) comprises: photographing each end surface of the measured object scanned by a camera according to the subdivided focusing interval setting value; In the step (D), the step of converting each cross-sectional image of the measurement object scanned into a three-dimensional image through a 3D image output unit and outputting the same may be repeated according to the subdivided focusing interval setting value.

The depth controller may apply the AC pulse onto the liquid lens, and may vary at least one of the amplitude, frequency, and duty of the AC pulse according to the measurement distance of the measurement object or the appearance gradient of the measurement object. have.

The scanning method of the scanner apparatus according to another embodiment of the present invention, (A) irradiating the light in the oral cavity with a light source, (B) receives the light reflected from the tooth, the optical system including a liquid lens Scanning according to a focusing interval setting value by a depth control unit for adjusting a focus of the liquid lens, (C) photographing each end surface of the tooth scanned according to the focusing interval setting value with a camera, (D) the Determining a tooth type by comparing each section of the photographed tooth with a database storing standard tooth image data. (E) when the tooth type is determined, the main controller controls the depth control unit to set a focusing interval set value according to the tooth type. Correcting and scanning at the optimal focusing interval setting through (F) the camera scanning the cross section of the tooth that has been corrected and scanned using the optimal focusing interval setting. Freezing step and through (G) parts of the 3D image output to the cross-section image taken by the camera and a step of switching to the 3D image.

Here, in step (E), if the tooth type is not determined, step (B) controls and scans the depth controller so that the focusing interval setting value is further divided by the main controller, and (C). Step) photographing each end surface of the tooth scanned by the camera according to the subdivided focusing interval setting value; And (D) may further comprise repeating the step of determining a tooth type by comparing each section of the photographed tooth with a database storing standard tooth image data according to the subdivided focusing interval setting value. have.

In addition, the depth control unit applies the AC pulse on the liquid lens, the at least one of the amplitude, frequency and duty of the AC pulse can be varied according to the shape of the measurement distance to the tooth or the appearance gradient of the measurement object. have.

The features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings.

Prior to this, the terms or words used in this specification and claims are not to be interpreted in a conventional and dictionary sense, and the inventors may appropriately define the concept of terms in order to best explain their invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention.

According to one embodiment of the present invention, in the 3D scanner apparatus, by applying a non-driven optical system to adjust the focus does not have a separate drive means according to the drive in the device can be made thin and small easily, There is an effect that can effectively secure the durability and reliability of the operation of the scanner device for reducing vibration and noise.

In addition, in order to effectively secure the 3D scanning image in the scanning process, precise 3D scanning according to the shape and structure of the object is possible by more precisely controlling the setting of the tomography interval according to the object during tomography.

In addition, when applied for scanning in the oral cavity, by effectively utilizing the standard data of the type of teeth, it is possible to perform a more accurate and accurate 3D oral scan in consideration of the shape according to the type of teeth.

1 is a view showing a scanner according to an embodiment of the present invention;

FIG. 2 is a more detailed view of the control circuit of the 3D oral cavity scanner shown in FIG. 1;

3 illustrates a scanning system according to another embodiment of the present invention;

4 is a flowchart provided to explain a scanning method according to an embodiment of the present invention;

5 is a flowchart of a scanning method for an oral cavity, which is one specific embodiment of the present invention;

Figure 6 illustrates the results of performing oral scanning in accordance with an embodiment of the present invention

The objects, specific advantages and novel features of one embodiment of the present invention will become more apparent from the following detailed description and the preferred embodiments associated with the accompanying drawings. In the present specification, in adding reference numerals to the components of each drawing, it should be noted that the same components as possible, even if displayed on different drawings have the same number as possible. In addition, terms such as “one side”, “other side”, “first”, “second”, etc. are used to distinguish one component from another component, and a component is limited by the terms. no. Hereinafter, in describing one embodiment of the present invention, detailed descriptions of related well-known techniques that may unnecessarily obscure the subject matter of one embodiment of the present invention will be omitted.

Hereinafter, with reference to the accompanying drawings, an embodiment of the present invention will be described in detail, the same reference numerals refer to the same members.

1 is a view showing a scanner according to an embodiment of the present invention, Figure 2 is a view showing in more detail the control circuit of the 3D oral scanner shown in Figure 1, Figure 3 is another embodiment of the present invention A diagram of a scanning system according to the present invention.

Scanner apparatus according to an embodiment of the present invention, the cross section of the measurement object by a light source 110 for irradiating light on the measurement object, an optical system for receiving the light reflected by the measurement object, the reflected light received by the optical system The depth control unit 192 and the camera 120 to control the focus control of the camera 120 and the liquid lens included in the optical system to control the camera 120, the measurement object to the depth control unit 192 It includes; main control unit 191 for controlling the focusing interval set value for the.

As shown in FIG. 1, the scanner apparatus includes a light source 110, a camera 120, a polarization filter, a lens housing, a liquid lens 150 (Liquid Lens), an optical lens 160, a probe, and a reflector. , To the main controller 191 and the depth controller 192.

The light source 110 irradiates light to the measurement object, and receives the light reflected by the measurement object from the optical system so that the camera 120 photographs the cross-sectional shape of the measurement object. By combining a plurality of cross-sectional images of the measurement object, a three-dimensional final image can be output as described later.

The light source 110 is a device that generates light by using an LED or a laser. The light source 110 may radiate light to a measurement object through a mirror, and the light source 110 directly radiates light directly to the mirror 180 through a probe 170. can do.

The optical system is a place where light by the light source 110 irradiated to the measurement object is reflected and incident, and may include a liquid lens that is a variable focus lens for focusing the measurement object. The liquid lens focuses on the measurement object to be scanned more accurately with no noise and no vibration by adjusting the focus by no driving so that the reflected light reflected from the measurement object is incident and the camera 120 can take a cross-sectional image of the measurement object. Adjustable

The optical system may further include the optical lens 160 and the polarization filter 130. Here, the polarization filter 130 can suppress diffuse reflection as much as possible by disposing at the end of the lens in order to minimize the scattered light according to the reflectance of the target object to be scanned.

The camera 120 accurately transmits the measurement of each section of the measuring object to be photographed through the focus adjustment of the liquid lens and transmits the related information to the main control unit 191 to output the 2D or 3D image of the final desired measuring object. Make it possible.

The depth controller 192 adjusts the focus of the liquid lens included in the optical system. The focusing of the liquid lens is possible by applying a voltage, and particularly, the precision of the focusing is required for a small or more accurate scan of the object to be measured. In one embodiment of the present invention, by applying an AC pulse to the liquid lens for more effective scanning of the measurement object, it is possible to continuously or continuously control the fine focusing. In addition, the depth control unit 192 may also be implemented through electrical control of the focal adjustment of the liquid lens intermittently changing. If the applied voltage is DC, it may be fixed to the lens housing 140 shown in FIG. 1 and thus may be insensitive to a slight change in the voltage, thereby applying an AC type pulse.

Here, the AC pulse is a pulse capable of varying the amplitude (0V ~ 60V), the frequency (240Hz ~ 3.9KHz), the duty (0 ~ 100%).

Here, by applying the AC pulse, by applying any one of the amplitude, frequency, and duty of the AC pulse, it is possible to appropriately adjust the focal length, the focusing precision and the duration of the focus maintenance for the measurement object. If the measurement object is a tooth in the oral cavity, there is a remarkable difference in the inclination of the side surfaces of various related teeth, and since it is a very narrow measurement in the oral cavity, it is necessary to appropriately adjust the accuracy of the focus adjustment and the waveform of the applied voltage. will be.

In addition, the depth controller 192 may adjust the focusing interval setting value of the target measurement object through the focusing interval setting value by the main controller 191 together with the focusing control of the liquid lens. The focusing interval setting value will be described later.

The main controller 191 controls the camera 120 and may control a focusing interval setting value for the measurement object to be scanned through the depth manufacturing that controls the focus adjustment of the liquid lens.

The main controller 191 includes a drive controller for driving the light source 110, that is, a constant voltage / constant current controller, and is a pre-standard for the measurement object corresponding to the cross-sectional image information of the measurement object photographed by the camera 120. It may include a database for storing the image information.

Here, the standard image information of the measurement object may be standard data of the measurement object to be scanned, that is, data of a standard shape of each tooth in the case of oral teeth. In addition, it is possible to output more precise and reliable three-dimensional images by storing in advance a general and standard information image of a measurement object to be scanned, and matching this data with image information that is actually photographed in the scanning process. It is.

That is, for example, when scanning a tooth in the oral cavity, standard data about the tooth may be stored in a database. The image information of the standard tooth can obtain an optimized precise scan image that matches the characteristics of the measurement object by effectively setting a large or small focusing method or focusing interval in consideration of the shape and appearance of the tooth. In particular, by transmitting information on the focusing interval setting value to the depth control unit 192 for driving the liquid lens, the optical system can scan the measurement object according to the focusing interval setting value.

For example, since the cross section of the canine is rapidly changed, the focusing intervals are set small, and the incisor and the molar are smoothly changed, so setting the focusing intervals is larger than the canine, thereby increasing the accuracy and reliability of the scan.

Each cross-sectional image of the measurement object taken by the camera 120 is finally transmitted to the 3D image output unit through the main controller 191. Here, the plurality of related cross-sectional images may be converted into three-dimensional images to output a final scanned image.

Specifically, as shown in FIG. 2, a detailed process of the main controller 191 and the depth controller 192 will be described.

As illustrated in FIG. 2, the main controller 191 includes a camera 120 controller for controlling the camera 120 and a constant voltage / constant current controller for driving the light source 110. The controllers are controlled by the MCU. The cross-sectional images of the measurement object generated by the camera 120 are input through the camera 120 interface and then transferred to the 3D image output unit through the main controller 191.

As shown in FIG. 2, the depth controller 192 may include a D / A converter, a bias circuit, a frequency generator, a DC / DC converter, and a full-bridge switching circuit. The depth controller 192 applies an AC pulse other than DC to the liquid lens 150 to adjust the focal length of the liquid lens 150.

 The focal length of the liquid lens 150 controlled by the depth controller 192 corresponds to the depth of the cross section of the measurement object. The depth controller 192 transmits the depth information to the main controller 191, and the main controller 191 transmits the depth information together when transferring the measured object cross-sectional images generated by the camera 120 to the 3D image output unit. .

The 3D image output unit lists cross-sectional images of the measurement object according to depth information to generate an image of the 3D measurement object. The 3D image output unit may be driven by a PC as well as other computing devices.

The 3D image output unit may control the depth controller 192 through the main controller 191. Accordingly, the 3D image output unit may operate the liquid lens 150 in the step mode or the sweep mode, and control the focal length of the liquid lens 150 (that is, the depth of the measurement object cross-sectional image) from 0 to 4096 steps. have.

3 illustrates a scanning system according to another embodiment of the present invention. As shown in FIG. 3, a scanning system according to an embodiment of the present invention may include a scanner 100, a system body 200, a processor 300, and a 3D printer 400.

The processor body 300 is accommodated in the system body 200, a display is provided, and the scanner 100 and the 3D printer 400 are connected. The processor 300 executes the above-described 3D image output unit and displays an image of a three-dimensional measurement object on a display.

Under the control of the 3D image output unit, the 3D printer 400 may produce a product or an object having a desired three-dimensional shape through a three-dimensional image of a desired measurement object.

FIG. 4 is a flowchart provided to explain a scanning method according to an embodiment of the present invention, and FIG. 5 is a flowchart of a scanning method for an oral cavity, which is one specific embodiment of the present invention.

Scanning method according to an embodiment of the present invention, (A) the step of irradiating light to the measurement object with the light source 110 (S10), (B) receives the light reflected from the measurement object, and includes a liquid lens Scanning by the depth control unit 192 adjusting the focus of the liquid lens according to a focusing interval setting value (S20), (C) the measurement object scanned by the optical system according to the focusing interval setting value Photographing each cross section of the camera 120 through the main controller 191 (S30); And (D) converting the image photographed by the camera 120 to a 3D image output unit through the main controller 191 and converting the image captured by the camera 120 into a 3D image by the 3D image output unit (S40). do.

First, step S10 of irradiating light onto a target object to be scanned through the light source 110.

Next, the light reflected from the measurement object is incident to the optical system, through which the camera 120 captures and scans a cross-sectional image of the measurement object (S20). In the optical system including the liquid lens, the depth controller 192 adjusts the focus of the liquid lens according to the focusing interval setting value. The depth controller 192 may apply a voltage for adjusting the focus of the liquid lens. Specifically, the depth controller 192 may apply an AC pulse, and may measure at least one of an amplitude, a frequency, and a duty of the AC pulse to measure the measurement distance or the measurement object. It has already been described above that it can be varied depending on the shape of the appearance gradient of the object.

Next, in operation S30, each end surface of the measurement object scanned by the optical system is photographed by the camera 120 through the main controller 191 according to the focusing interval setting value. The main controller 191 may include a controller for driving the light source 110, control the camera 120, and control a focusing interval setting value by the depth controller 192 for adjusting the focus of the liquid lens. Can be. Here, the focusing interval setting value may have a fixed value basically fixed by the information about the first target measurement object, and may be adjusted in an appropriate range as will be described later.

Next, the image photographed by the camera 120 is transmitted to the 3D image output unit through the main controller 191 and is converted into a 3D image by the 3D image output unit (S40). By transmitting the cross-sectional image information according to the depth of the measurement object through the focus control of the liquid lens to the 3D image output unit by the main control unit 191, the three-dimensional scan image is finally output.

In addition, if the scanned image is checked by the 3D image output unit (S50), and the image is not clear or a fine scan cannot be performed according to the related focusing interval setting value, the depth control unit 192 in step (B) is performed. As a result, the process returns to the step of scanning according to the focusing interval setting value and drives the process again. However, in this case, when the process returns to step (B) again, the main controller 191 causes the depth controller 192 to newly set a smaller focusing interval setting value than before (S60). The final 3D scanned image through the conversion of the 3D image can obtain a clearer and more precise image.

Determination of the scanned image by the 3D image output unit can be made by a practical user, or by setting a setting value for specific information of the image, and automatically focusing interval when the element falls below or significantly exceeds the reference value. By setting the setting value smaller or larger, scanning can be realized at an optimal focusing interval setting value suitable for the measurement object.

When the output image by the 3D image output unit is a desired image, the final 3D scan image is naturally output and the related process is terminated.

As a specific example, as shown in Figure 5, a specific process in the case of scanning the teeth in the mouth according to an embodiment of the present invention will be described.

First, (A) is a step (S110) of irradiating the light in the oral cavity with the light source (110).

Next, (B) receiving the light reflected from the tooth, the optical system including the liquid lens is scanned by the depth control unit 192 for adjusting the focus of the liquid lens in accordance with the focusing interval set value (S120) . In the case of teeth, it has already been described that the optical system may include a polarizing filter 130 to minimize scattered light according to its reflectivity.

Next, (C) photographing each section of the scanned tooth according to the focusing interval setting value with the camera 120. Here, the focusing interval setting value is initially set in an appropriate range, and it is easy to convert and output related image data into a 3D image. As described below, the focusing interval setting value can be adjusted within an appropriate range.

Next, (D) step (S130) to determine the type of teeth by comparing each section of the photographed teeth and the database that stores the standard tooth image data. The existing standard image information of the tooth is previously stored in a database, and the type of the tooth is determined by comparing and analyzing the cross-sectional image photographed by the camera 120. Determining the type of teeth is to appropriately set the range of depth of focusing according to the type of teeth.

In addition, in order to obtain a more suitable scan image according to the appearance shape of the tooth or the range of the inclination, the focusing interval set value already set by the standard image information may be appropriately applied according to the type of the tooth. In this case, it may be appropriate to classify into several groups of types of teeth, set the focusing interval setting values optimized for each classification group, and finally scan the focusing interval setting values within a predetermined range during the scanning process of the entire tooth.

Next, as described above, (E) when the tooth type is determined, the main controller 191 corrects and scans the focusing interval setting value set according to the tooth type to an optimal focusing interval setting value through the depth control unit 192. Step S150. The main controller 191 includes a database storing not only the control of the camera 120 but also standard image information of the teeth, and compares the cross-sectional image information of the camera 120 with the standard image information to set an appropriate focusing interval setting value. Control may be performed through the depth controller 192.

Next, (F) the camera 120 photographs the cross section of the tooth that has been corrected and scanned through the optimal focusing interval setting value (S160). By setting the focusing interval setting value and the range of focusing optimized for the shape and depth of the tooth to be scanned, a more accurate and accurate scanning image can be obtained.

Finally, (G) converting the cross-sectional image photographed by the camera 120 to a 3D image through the 3D image output unit (S170).

If, in step (E), the type of tooth cannot be determined, that is, when the cross-sectional image information is not correct by the camera 120 or the type of tooth cannot be specified,

And controlling (S140) the depth control unit 192 to scan the depth control unit 192 so that the focusing interval setting value is further subdivided by the main controller 191 in step (B), and the newly set subdivided focusing interval in step (C). Photographing each end surface of the scanned tooth according to a set value with the camera 120; And determining the type of the tooth by repeatedly performing the step of determining the tooth type by comparing each section of the photographed tooth and the database of the standard tooth image data stored according to the subdivided focusing interval setting value in step (D). You can proceed with the related process.

On the other hand, it is not possible to check the tooth type because accurate scanning is not performed due to a user's mistake or bleeding or a foreign object, or when the adjacent image information suddenly differs by comparing captured images of each tomographic image section. You can generate a message.

In addition, the scanning value may be subdivided to adjust the setting value so that the wrongly scanned portion may be normally scanned. If not incorrectly scanned, the tomography section may be further subdivided so as to correct this even when the area between the respective images is formed too wide.

In addition, the scanning process is performed again with the segmented tomography section, thereby obtaining a more accurate 3D image of the tooth.

6 illustrates the results of performing 3D oral scanning according to an embodiment of the present invention. 6 is a three-dimensional combined image using Cloud Point data, which is just before obtaining 3D data.

Although the present invention has been described in detail through specific examples, it is intended to describe the present invention in detail, and the present invention is not limited thereto, and should be understood by those skilled in the art within the technical spirit of the present invention. It is obvious that the modifications and improvements are possible.

All simple modifications and variations of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be apparent from the appended claims.

Claims (12)

A light source for irradiating light onto the measurement object; An optical system for receiving light reflected by the measurement object; A camera for photographing the section of the measurement object by the reflected light received by the optical system; And A depth control unit controlling a focus control of the liquid lens included in the optical system through an AC pulse; And And a main controller for controlling the camera and controlling a focusing interval setting value for the measurement object in the depth controller. The method according to claim 1, The main control unit, A drive controller for driving the light source; And And a database storing pre-standard image information of the measurement object corresponding to the cross-sectional image information of the measurement object photographed by the camera. And a cross section image information provided by the camera and pre-standard image information of the measurement object to control a focusing interval setting value of the depth controller. The method according to claim 1, The depth control unit applies the AC pulse on the liquid lens, the scanner device for varying at least one of the amplitude, frequency and duty of the AC pulse in accordance with the shape of the measurement distance of the measurement object or the appearance gradient of the measurement object. The method according to claim 1, And a 3D image output unit which receives the cross-sectional image data of the measurement object acquired by the camera from the main controller and converts the cross-sectional image data into a 3D image and outputs the 3D image. The method according to claim 2, The main control unit, When the measurement object is an oral tooth, The database stores an image of a standard tooth, and compares the image obtained by the camera with the image of the standard tooth to determine the tooth type, And a depth control unit configured to control a depth control unit to a focusing interval set value set according to a range of an external cross-sectional inclination of a tooth according to the tooth type. The method according to claim 1, The optical system further comprises a polarizing filter coupled to one end. (A) irradiating light to the measurement object with a light source; (B) receiving light reflected from the measurement object, and scanning the optical system including a liquid lens according to a focusing interval setting value by a depth controller for adjusting a focus of the liquid lens; (C) photographing each end surface of the measurement object scanned by the optical system with a camera through a main controller according to the focusing interval setting value; And And (D) transmitting the image photographed by the camera to the 3D image output unit through the main control unit and converting the image photographed by the camera into a 3D image. The method according to claim 7, After the step (D), (E-1) when the converted 3D image is unclearly determined, Step (B) may include controlling and scanning the depth controller so that the focusing interval setting value is further refined by a main controller; Step (C) may include photographing each end surface of the measured object scanned by a camera according to the subdivided focusing interval setting value; And The step (D) is a step of repeating the output of each of the cross-sectional image of the measurement object scanned to the three-dimensional image through the 3D image output unit according to the subdivided focusing interval setting value; The method according to claim 7, The depth control unit applies the AC pulse on the liquid lens, and at least one of the amplitude, frequency and duty of the AC pulse to vary depending on the shape of the measurement distance of the measurement object or the appearance gradient of the measurement object. (A) irradiating the light in the oral cavity with a light source; (B) receiving light reflected from the tooth, and scanning by an optical system including a liquid lens according to a focusing interval setting value by a depth controller for adjusting a focus of the liquid lens; (C) photographing each end surface of the tooth scanned according to the focusing interval setting value with a camera; (D) determining a tooth type by comparing each section of the photographed tooth with a database storing standard tooth image data; (E) correcting and scanning the focusing interval setting value set according to the tooth type to an optimal focusing interval setting value through the depth control unit when the tooth type is determined; (F) photographing, by the camera, a section of the tooth that has been corrected and scanned using the optimal focusing interval setting value; And (G) converting a cross-sectional image photographed by the camera to a three-dimensional image through a 3D image output unit. The method according to claim 10, Step (E), If the tooth type is not determined, Step (B) may include controlling and scanning the depth controller so that the focusing interval setting value is further refined by a main controller; Step (C) may include photographing each end surface of the tooth scanned by the camera according to the subdivided focusing interval setting value; And The step (D) further comprises the step of repeating the step of determining the tooth type by comparing each section of the photographed teeth and the database of the standard tooth image data stored according to the subdivided focusing interval set value; . The method according to claim 10, The depth control unit applies the AC pulse on the liquid lens, and at least one of the amplitude, frequency, and duty of the AC pulse to vary depending on the shape of the measurement distance to the tooth or the appearance gradient of the measurement object

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