JP2009165558A - Method and device for measuring inside of oral cavity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for measuring the inside of the oral cavity, which allows precise shape measurement of the inside of the oral cavity. <P>SOLUTION: The method for measuring the inside of the oral cavity includes a light projecting process, an imaging process, an exposure time control process, an image composition process, and a three-dimensional arithmetic process. In the light projecting process, an encoded stripe pattern is projected. In the imaging process, an area where the stripe pattern is projected, is picked up as a two-dimensional static image. In the exposure time control process, an exposure time is controlled so as to be able to optimally pick up the two dimensional static image in the imaging process. In the image composition process, two-dimensional static images picked up by at least two different exposure times are combined to generate a composite two-dimensional static image. In the three-dimensional arithmetic process, three-dimensional coordinates of the inside of the oral cavity is calculated on the basis of the composite two-dimensional static image. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for imaging an intraoral area for producing a dental prosthesis such as an inlay, a crown, and a bridge, and more specifically, an intraoral measurement method for directly measuring an intraoral area of a patient, and The present invention relates to an intraoral measurement device.

  Conventionally, for the production of dental prostheses such as inlays, crowns and bridges, a method of casting a metal material or a ceramic material by a lost wax casting method has been generally adopted. However, in the creation of dental prostheses in recent years, in-oral measurement of teeth and gingiva using an optical three-dimensional camera such as the SEREC system (system of Sirona, Germany) and a CAD / CAM system are used. Attention has been focused on the design and production system of dental prosthesis used.

  For the optical three-dimensional camera, a non-contact three-dimensional measurement technique represented by a phase shift method or a spatial encoding method is used. The optical three-dimensional camera directly reads the shape of the abutment tooth, the tooth formed in the cavity, and in some cases, the adjacent tooth and the counter tooth (for example, see Patent Document 1).

  This optical three-dimensional camera and CAD / CAM system can efficiently produce a dental prosthesis as compared with the casting method as described above. If the design is appropriately performed, the completed dental prosthesis can be obtained. It has the advantage of being able to produce a dental prosthesis that has high accuracy and is excellent in conformity to the oral cavity. However, in the optical three-dimensional camera and the CAD / CAM system, the calculation for determining the final shape of the dental prosthesis (the shape becomes information for processing) can be automatically calculated by a computer. It depends on each patient, and the surface reflectance of each tissue differs depending on the condition of the caries and the composition of the enamel, dentin and gingiva that make up the teeth. It is difficult to measure the shape of teeth and gums. For this reason, there has been a problem that it becomes difficult to produce an ideal dental prosthesis excellent in conformity accuracy.

In order to solve such a problem, in order to make the difference in the reflectance in the oral cavity uniform, in the SEREC system (system of Sirona, Germany), powder such as titanium oxide is sprayed in the oral cavity.
JP 2000-74635 A

  However, the spraying of the powder is an action that causes bitterness and discomfort for the patient because the powder is a metal powder, and for the doctor, it is an action that requires time and skill because a uniform spray is required.

  This invention solves the said subject, and it aims at providing the intraoral measurement method and intraoral measurement apparatus which can measure the shape of an intraoral correctly, without spraying powder.

  An intraoral measurement method according to a first invention is an intraoral measurement method for measuring the intraoral area, and includes a light projecting step, an imaging step, an exposure time control step, an image composition step, and a three-dimensional calculation. Process. The light projecting process projects the coded fringe pattern. In the imaging step, a region on which the fringe pattern is projected is captured as a two-dimensional still image. The exposure time control step controls the exposure time so that a two-dimensional still image can be optimally captured in the imaging step. The image synthesizing step synthesizes the two-dimensional still image captured by at least two different exposure times to generate a synthesized two-dimensional still image. In the three-dimensional calculation step, three-dimensional coordinates in the oral cavity are calculated based on the synthesized two-dimensional still image.

  Here, in the exposure time control step, the exposure time is controlled so that a two-dimensional still image can be optimally captured in the imaging step, and in the image composition step, a two-dimensional still image captured by at least two different exposure times is synthesized. Thus, a composite two-dimensional still image is generated.

  Conventionally, the shape of a dental prosthesis is determined by measuring the intraoral shape using an optical three-dimensional camera and a CAD / CAM system. However, the intraoral shape can only capture an image with a small contrast because the surface reflectance of each tissue differs depending on the state of the caries and the composition of the gingiva. For this reason, accurate tooth and gingival shape measurement is difficult.

  Therefore, in the intraoral measurement method of the present invention, an exposure time control step for controlling the exposure time so as to optimally capture a two-dimensional still image in the imaging step, and a two-dimensional still image captured by at least two different exposure times. And an image synthesis step for generating a synthesized two-dimensional still image.

  This makes it possible to extract regions with different surface reflectivities and capture a two-dimensional still image with an optimal exposure time for each region. Is possible. Further, by synthesizing the respective two-dimensional still images captured with the optimum exposure time, it is possible to obtain a synthesized two-dimensional still image having a large contrast for all the regions.

  As a result, since it is possible to measure using a synthesized two-dimensional still image imaged with good contrast, the shape of the oral cavity can be accurately measured without spraying powder.

  The intraoral measurement method according to the second invention is the intraoral measurement method according to the first invention, and in the exposure time control step, each region of teeth and gingiva in the oral cavity is optimally captured by the imaging step. The exposure time is controlled as follows.

Here, a tooth region and a gingival region in the oral cavity are extracted, and the exposure time is controlled so that each region is optimally captured by the imaging process.
As a result, a two-dimensional still image can be captured with an optimum exposure time for each of the tooth region and the gingival region. Therefore, a two-dimensional still image having a large contrast for the tooth region and a two-dimensional still image having a large contrast for the gingival region. It is possible to acquire two images with a three-dimensional still image. Then, by combining the two two-dimensional still images, it is possible to obtain a combined two-dimensional still image having a large contrast in both the tooth region and the gingival region.

  An intraoral measurement method according to a third invention is the intraoral measurement method according to the first or second invention, and the exposure time control step includes a data separation step, an exposure time calculation step, and an exposure time adjustment step. And have. In the data separation step, signal data is separated from the video signal obtained in the imaging step. The exposure time calculation step calculates an exposure time at the saturation limit in the two-dimensional still image based on the signal data. The exposure time adjustment step adjusts the exposure time based on the exposure time calculated in the exposure time calculation step.

  Here, in the data separation step, signal data is separated from the video signal obtained in the imaging step, and in the exposure time calculation step, the saturation limit exposure time in the two-dimensional still image is calculated based on the signal data.

  Thereby, signal data used for calculating the exposure time can be extracted, so that the exposure time can be calculated appropriately. It is also possible to calculate the state with the highest contrast by calculating the exposure time at the saturation limit.

An intraoral measurement method according to a fourth invention is the intraoral measurement method according to any one of the first to third inventions, wherein the exposure time control step is based on the luminance information and the tooth region and gingiva. Set the area.
Here, luminance information is used in extracting the tooth region and the gingival region.
This makes it possible to extract the tooth region and the gingival region relatively easily.

  An intraoral measurement apparatus according to a fifth invention is an intraoral measurement apparatus whose measurement target is the intraoral area, and includes a light projecting unit, an imaging unit, an exposure time control unit, an image synthesis unit, and a three-dimensional calculation Department. The light projecting unit projects the coded stripe pattern. The imaging unit captures a region on which the fringe pattern is projected as a two-dimensional still image. The exposure time control unit controls the exposure time so that the imaging unit can optimally capture a two-dimensional still image. The image synthesizing unit synthesizes the two-dimensional still images captured by at least two different exposure times to generate a synthesized two-dimensional still image. The three-dimensional calculation unit calculates three-dimensional coordinates in the oral cavity based on the synthesized two-dimensional still image.

  Here, the exposure time control unit controls the exposure time so that the imaging unit can optimally capture the two-dimensional still image, and the image synthesis unit synthesizes the two-dimensional still image captured by at least two different exposure times. Then, a synthesized two-dimensional still image is generated.

  Conventionally, the shape of a dental prosthesis is determined by measuring the intraoral shape by an optical three-dimensional camera and a CAD / CAM system. However, the intraoral shape can only capture an image with a small contrast because the surface reflectance of each tissue differs depending on the state of the caries and the composition of the gingiva. For this reason, accurate tooth and gingival shape measurement is difficult.

  Therefore, in the intraoral measurement apparatus of the present invention, an exposure time control unit that controls the exposure time so that the imaging unit can optimally capture a two-dimensional still image, and a two-dimensional still image captured by at least two different exposure times. And an image synthesis unit that synthesizes and generates a synthesized two-dimensional still image.

  This makes it possible to extract regions with different surface reflectivities and capture a two-dimensional still image with an optimal exposure time for each region. Is possible. Further, by synthesizing the respective two-dimensional still images captured with the optimum exposure time, it is possible to obtain a synthesized two-dimensional still image having a large contrast for all the regions.

  As a result, since a three-dimensional coordinate can be calculated using a synthesized two-dimensional still image imaged with good contrast, the shape of the oral cavity can be accurately measured without spraying powder.

  An intraoral measurement device according to a sixth invention is the intraoral measurement device according to the fifth invention, wherein the exposure time control unit optimally captures each region of the teeth and gingiva in the oral cavity by the imaging unit. The exposure time is controlled as follows.

Here, a tooth region and a gingival region in the oral cavity are extracted, and the exposure time is controlled so that each region is optimally captured by the imaging unit.
As a result, a two-dimensional still image can be captured with an optimum exposure time for each of the tooth region and the gingival region. Therefore, a two-dimensional still image having a large contrast for the tooth region and a two-dimensional still image having a large contrast for the gingival region. It is possible to acquire two images with a three-dimensional still image. Then, by combining the two two-dimensional still images, it is possible to obtain a combined two-dimensional still image having a large contrast in both the tooth region and the gingival region.

  An intraoral measurement device according to a seventh invention is the intraoral measurement device according to the fifth or sixth invention, wherein the exposure time control unit is a data separation unit, an exposure time calculation unit, and an exposure time adjustment unit. And have. The data separation unit separates signal data from the video signal obtained in the imaging unit. The exposure time calculation unit calculates the exposure time at the saturation limit in the two-dimensional still image based on the signal data. The exposure time adjustment unit adjusts the exposure time based on the exposure time calculated by the exposure time calculation unit.

  Here, the data separation unit separates the signal data from the video signal obtained in the imaging unit, and the exposure time calculation unit calculates the saturation limit exposure time in the two-dimensional still image based on the signal data.

  Thereby, signal data used for calculating the exposure time can be extracted, so that the exposure time can be calculated appropriately. It is also possible to calculate the state with the highest contrast by calculating the exposure time at the saturation limit.

  An intraoral measurement device according to an eighth invention is the intraoral measurement device according to any one of the fifth to seventh inventions, wherein the exposure time control unit is configured to determine a tooth region and a tooth area based on the luminance information. Set the gingival area.

Here, luminance information is used in extracting the tooth region and the gingival region.
This makes it possible to extract the tooth region and the gingival region relatively easily.

  According to the intraoral measurement method and the intraoral measurement device according to the present invention, since a three-dimensional coordinate can be calculated using a synthesized two-dimensional still image imaged with good contrast, the intraoral shape is accurately measured. It becomes possible.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1]
FIG. 1 is an intraoral imaging and image measurement flowchart in the first embodiment of the present invention.
In FIG. 1, an optical three-dimensional camera (hereinafter referred to as an oral scanner) set in the oral cavity performs an operation similar to that of a conventional video system for intraoral imaging (S01). In the imaging frame, the teeth 108 and the gingiva 109 are imaged by the imaging lens and sensor, and the images are displayed on the display. Thereby, a standard video image is obtained (S02). At this time, in order to accurately match the imaging position of the oral scanner with the tooth 108 and the gingiva 109, for example, the imaging position may be designated by a mark such as a frame or a cross.

  Next, in order to perform three-dimensional image processing by fringe pattern projection with high speed and high accuracy, the shutter speed of the image sensor is adjusted, and the optimal exposure time for each of the tooth 108 region and the gingival 109 region is adjusted. Setting is performed (S03: exposure time control step). Note that the region formation of the teeth 108 and the gums 109 and the setting of the optimum exposure time condition for each region will be described later.

  Next, it is confirmed whether or not the images of the teeth 108 and the gingiva 109 are good with respect to the video image obtained in the imaging scanning stage (S04). If it is satisfactory, image measurement is performed using a foot switch or the like.

  In image measurement, a triangulation method is used to project a fringe pattern for converting a two-dimensional still image into a three-dimensional still image, pick it up using an image sensor such as a CCD, and store it as image data (two-dimensional still image). (S05: Projection process, imaging process). At this time, the stripe pattern is preferably a pattern called a gray code as shown in FIG. 2 if a spatial encoding method is used. A normal code pattern can be used if the measurement accuracy is sufficient. If the phase shift method is used, it is common to use a known shading pattern that changes in a sine wave shape.

  Next, in order to improve the contrast of the fringe pattern of the image data recorded in the memory, two-dimensional image processing such as noise removal, gradation correction, and gamma correction is performed in the areas of the teeth 108 and the gums 109 (S06).

  Subsequently, tone correction is performed on the tooth region and the gingival region while referring to the histogram of the captured image, and the image is synthesized (S07: image synthesis step). A method for synthesizing the teeth and gingiva regions will be described later.

  Further, low-accuracy three-dimensional image conversion is performed by triangulation from the image data obtained by thinning the final three-dimensional data amount to 1/2 to 1/10 (S08). Thereby, it is determined whether or not the captured image is good (S09). This is intended to speed up the pass / fail judgment of the obtained image, and is unnecessary when speeding up is not necessary.

  If the last captured image is good, highly accurate three-dimensional image conversion is performed by triangulation, and the obtained three-dimensional coordinates are stored in memory as point cloud data or STL (Stereo Lithography) data. Then, using the data, three-dimensional coordinates are displayed on the display (S10: three-dimensional calculation step). Here, point cloud data or STL data is cited as a representative data format, but the data format is not limited to this.

FIG. 3 is a schematic configuration diagram of the oral scanner (oral cavity measuring device) 1 according to the first embodiment of the present invention.
As shown in FIG. 3, the oral scanner 1 includes an exterior case 101 that stores internal components so that the oral scanner 1 can be directly inserted into the oral cavity of a patient. A light source (light projecting unit) 102 made of a light emitting diode LED or a laser is attached in the exterior case 101. The light from the light source 102 passes through the condenser lens 103 and can irradiate the pattern mask 104 for generating a fringe pattern composed of an LCD shutter or the like. The fringe pattern that has passed through the beam splitter 105 is projected onto the tooth 108 and the gum 109 that are the objects to be measured via the aperture 106 and the objective condenser lens 107. In addition, a beam splitter 105 is provided to separate the light beam from the light source into the projection light path and the observation light path. The fringe pattern light is finally received by an image sensor (imaging unit) 111 such as a CCD through the imaging lens 110. The input data is transferred to the image processing unit (image combining unit) 113 stored in the external device 120 such as a PC via the transfer cable 112.

  The external device 120 includes an image processing unit 113, an exposure time control unit 114 that controls an exposure time when the image sensor 111 captures an intraoral image, and a captured image generated by the image processing unit 113. And a three-dimensional calculation unit 118 that calculates three-dimensional coordinates. The exposure time control unit 114 further includes a data separation unit 115, an exposure time calculation unit 116, and an exposure time adjustment unit 117. The data separation unit 115 separates the video signal obtained by the image sensor 111 into an L signal and an S signal. The exposure time calculation unit 116 calculates the optimum exposure time when the signal image obtained by the data separation unit 115 is captured. The exposure time adjustment unit 117 optimizes the exposure time in the image sensor 111 based on the optimum exposure time calculated by the exposure time calculation unit 116.

In the present embodiment, the example in which the image processing unit 113, the exposure time control unit 114, and the three-dimensional calculation unit 118 are stored in the external device 120 has been described, but these are built in the oral scanner 1. Alternatively, it may be stored in a server connected by a wireless LAN or the like.
Details of processing performed by the image processing unit 113, the exposure time control unit 114, and the three-dimensional calculation unit 118 will be described later.

  FIG. 4 is a process flow diagram regarding the region formation of the teeth 108 and the gingiva 109 and the setting of the exposure time condition for each region in the first embodiment.

  When the setting of the exposure time is started (T01), the intraoral video signal is taken into the image processing unit 113 from the image sensor 111 (T02). At this time, the image sensor 111 sets the horizontal transfer rate of the CCD to twice the normal speed, and for each horizontal line, the image signal (L signal) having a long exposure time and the video signal (S) having a short exposure time. By alternately outputting (signal), an L signal and an S signal are each output for one field within a period in which an image for one field is output in normal imaging.

  Next, preprocessing such as noise removal is performed on the signal output from the image sensor 111 (T03). Subsequently, the preprocessed signal is converted from an analog signal to a digital signal (T04). Next, the time between the L signal and the S signal continuously generated by the image sensor 111 so that the L signal and the S signal can be handled independently in the video signal generated by the image sensor 111. The axis is converted (T05).

Next, the L signal and the S signal are stored in the storage memory in the image processing unit 113 as an L signal image and an S signal image (T06).
Subsequently, information used for setting the regions of the teeth 108 and the gums 109 is extracted from the L signal image (T07). The area setting information may be a luminance signal or a specific color signal. Further, the maximum value or the minimum value of these luminance signals and color signals may be used. Here, a description will be given assuming that the most common luminance value is used for area setting. In this example, the L signal image having a long exposure time is used for region setting because of noise, but an S signal image may be used.

Next, a threshold value for area setting is calculated (T08). Here, the average of the data which is not saturated from the extracted luminance value is taken as the threshold value.
Next, the brightness value of each pixel is compared with the threshold value for region setting (T09). If the luminance value is less than the threshold value, it is set as the region of the gum 109 (T10).

  Subsequently, the exposure time of the gum region 109 is adjusted (T12). Usually, since the region of the gingiva 109 is darker than the region of the tooth 108, an L signal image having a long exposure time is used for adjusting the exposure time.

  Next, the exposure time is changed to capture an L signal image (T13). The exposure time is delayed until the luminance level in the region of the gum 109 in the L signal image is saturated, and the exposure time is optimized (T14). Here, processing is performed on the assumption that the luminance level is not saturated, but in the opposite case, adjustment is performed while increasing the exposure time.

  When the brightness level is saturated, the exposure time is returned to the level immediately before saturation, and the exposure time of the region of the gum 109 is determined (T15). At the same time, the region exposure time (GT) of the gingiva 109 is recorded (T16).

Similarly, the adjustment of the exposure time in the area of the tooth 108 and the recording of the area exposure time (DT) of the tooth 108 are performed (T17 to T21). However, since the region of the tooth 108 is brighter than the region of the gingiva 109, an S image having a short exposure time is used for adjusting the exposure time.
As described above, the setting of the exposure time is completed by performing the flow from T01 to T22 (T22).

  FIG. 5 is a flowchart of image composition processing of each image of the region of the tooth 108 and the region of the gingiva 109 in the first embodiment.

  When image composition is started (U01), the L signal and the S signal photographed with the exposure times GT and DT adjusted in the flow of FIG. 4 are taken into the image processing unit 113 (U02). Also at this time, the image sensor 111 alternately outputs the L signal and the S signal for each horizontal line by setting the horizontal transfer speed of the CCD to twice the normal speed, so that an image for one field is obtained in normal imaging. The L signal and the S signal are each output for one field within the period for outputting. Next, preprocessing such as noise removal is performed on the signal output from the image sensor 111 (U03). Subsequently, the preprocessed signal is converted from an analog signal to a digital signal (U04). Next, the time axis of the L signal and the S signal continuously generated by the image sensor 111 is set so that the video signal generated by the image sensor 111 can be handled independently of the L signal and the S signal. Convert (U05).

  Next, the L signal and the S signal are stored in the storage memory in the image processing unit 113 as an L signal image and an S signal image (U06). The L signal image and the S signal image are divided into a tooth 108 region and a gingival 109 region (U07). Based on this information, the regions of the teeth 108 and the gingiva 109 are set (U08, U09).

  FIGS. 6A to 6D are diagrams for explaining region division (U07) between the tooth 108 and the gum 109 in the first embodiment. FIG. 6A is a diagram illustrating the teeth 108 and the gingiva 109 captured by the image sensor 111. Generally, the region of the tooth 108 is a high luminance region, and the region of the gingiva 109 is a low luminance region. FIG. 6B shows the luminance value of the L signal image acquired with the long exposure time GT adjusted according to the region of the gingiva 109, and FIG. 6C shows the short time adjusted according to the region of the tooth 108. Is the luminance value of the S signal image acquired at the exposure time DT. Both FIG. 6B and FIG. 6C are luminance values corresponding to the AB line of the image shown in FIG. Here, the luminance value of the L signal image and the threshold value are compared. If the luminance level is less than the threshold value, the region is divided into the region of the gingiva 109, and if the luminance level is equal to or greater than the threshold value, the region is divided into the tooth 108 region. DA) and the gingival 109 region signal (GA) are given (U08, U09). In FIG. 6 (d), it is divided into regions of teeth 108 and gingiva 109.

Next, as shown in FIG. 5, luminance histogram data is acquired in each region (U12, U13). Since the region of the tooth 108 is a high luminance region, the histogram is concentrated on a bright portion. Therefore, gradation correction is performed to lift a bright part (U14). On the contrary, since the region of the gingiva 109 is a low luminance region, the histogram is concentrated in a dark part. Therefore, gradation correction is performed so as to lift a dark part (U15).
Finally, using the region signals DA and GA, the tone-corrected tooth 108 region image (two-dimensional still image) and the gingival 109 region image (two-dimensional still image) are synthesized (U16).

  FIG. 7A to FIG. 7C are comparison diagrams of an image captured by the normal processing flow and an image captured using the processing flow according to the first embodiment of the present invention.

  FIG. 7A and FIG. 7B have different exposure times for images captured in a normal processing flow. FIG. 7C is an image (combined two-dimensional still image) that has been imaged in the processing flow according to the first embodiment of the present invention. Here, a tooth model is used as a measurement target. As is apparent from FIGS. 7A to 7C, the gradation information is maintained and the image is taken in both the teeth 108 and the gingiva 109.

[Embodiment 2]
FIG. 8 is a process flow diagram regarding the region formation of the teeth 108 and the gingiva 109 and the setting of the exposure time condition for each region in the second embodiment. The difference from the first embodiment is a processing flow for regionizing teeth and gums. Since the other flow configuration is the same as that of the first embodiment, the description thereof is omitted here.
In the processing flow regarding the region formation of teeth and gingiva and the setting of the exposure time condition for each region in the second embodiment, the luminance value of the comparison region is used for comparison of the luminance component of the L signal image (V11). This is a difference from the first embodiment.

Hereinafter, it demonstrates according to a flow.
First, when the setting of the exposure time is started (V01), an intraoral video signal is taken into the image processing unit 113 from the image sensor 111 (V02). At this time, the operation of the image sensor 111 is the same as that of the first embodiment.

  Next, preprocessing such as noise removal is performed on the signal output from the image sensor 111 (V03). Subsequently, the preprocessed signal is converted from an analog signal to a digital signal (V04). Next, the time between the L signal and the S signal continuously generated by the image sensor 111 so that the video signal generated by the image sensor 111 can be handled independently of the L signal and the S signal. The axis is converted (V05). Further, the L signal and the S signal are stored as an L signal image and an S signal image in the storage memory in the image processing unit 113 (V06).

  Subsequently, a luminance value used for setting the region between the tooth 108 and the gum 109 is extracted from the L signal image (V07). Next, a threshold value for area setting is calculated (V08). Here, the average of the data which is not saturated from the extracted brightness | luminance value is taken as a threshold value.

  Next, a comparison area frame for comparing the luminance value of each pixel with the area setting threshold is set (V09). Subsequently, an average of the data that is not saturated within the comparison area frame (comparison area average luminance value) is taken (V10).

  Next, the comparison area average luminance value is compared with the area setting threshold value (V11). Here, if the luminance value is less than the threshold value, the region of the gum 109 is set (V12). If the luminance value is equal to or greater than the threshold value, the region of the tooth 108 is set (V13).

  Subsequently, the exposure time of the gum region 109 is adjusted (V14). Usually, since the region of the gingiva 109 is darker than the region of the tooth 108, an L image having a long exposure time is used for adjusting the exposure time.

  Next, the exposure time is changed to capture an L signal image (V15). Then, the exposure time is delayed until the luminance level of the region of the gum 109 in the L signal image is saturated, and the exposure time is optimized (V16). Here, processing is performed on the assumption that the luminance level is not saturated, but in the opposite case, adjustment is performed while increasing the exposure time.

  Next, when the brightness level is saturated, the exposure time is returned to the level immediately before saturation, and the exposure time of the region of the gum 109 is determined (V17). At the same time, the region exposure time (GV) of the gingiva 109 is recorded (V18).

  Similarly, the exposure time of the area of the tooth 108 is adjusted and the area exposure time (DV) of the tooth 108 is recorded (V19 to V23). However, since the tooth 108 region is brighter than the gingival 109 region, an S image having a short exposure time is used for exposure time adjustment.

By performing the above flow of V01 to V24, the setting of the exposure time is completed (V24).
If the second embodiment is used, it is possible to speed up the exposure time condition setting.

  The intraoral measurement method and apparatus have an effect of accurately measuring teeth and gingiva having different surface reflectivities, and directly measuring the suitability of dental prostheses having different surface reflectivities in the patient's oral cavity. It can also be applied to.

The flowchart of intraoral imaging | photography and image measurement in Embodiment 1 of this invention. The figure which showed an example of the gray pattern used by the space coding method. 1 is a schematic configuration diagram of an oral scanner in Embodiment 1 of the present invention. FIG. 5 is a processing flow diagram for setting an optimum exposure time according to the first embodiment of the present invention. The flowchart of the image composition process of each image of the tooth | gear area | region and gingiva area | region in Embodiment 1 of this invention. (A)-(d) is explanatory drawing of the area | region division of the tooth | gear and gingiva in Embodiment 1. FIG. The comparison figure of the image imaged by the conventional imaging flow (a), (b) and the imaging flow in Embodiment 1 (c) of this invention. FIG. 10 is a process flow diagram for setting an optimum exposure time in Embodiment 2 of the present invention.

Explanation of symbols

1 Oral scanner (oral cavity measuring device)
101 exterior case 102 light source (light emitting part)
103 condensing lens 104 pattern mask 105 beam splitter 106 stop 107 objective condensing lens 108 tooth 109 gingiva 110 imaging lens 111 image sensor (imaging part)
112 Transfer cable 113 Image processing unit (image composition unit)
114 Exposure time control unit 115 Data separation unit 116 Exposure time calculation unit 117 Exposure time adjustment unit 118 Three-dimensional calculation unit 120 External device

Claims (8)

An intraoral measurement method for measuring the intraoral area,
A light projecting process for projecting a coded fringe pattern;
An imaging step of capturing the area where the fringe pattern is projected as a two-dimensional still image;
An exposure time control step for controlling an exposure time so as to optimally capture the two-dimensional still image in the imaging step;
An image synthesis step of synthesizing the two-dimensional still image captured by at least two different exposure times to generate a synthesized two-dimensional still image;
A three-dimensional calculation step of calculating three-dimensional coordinates in the oral cavity based on the synthesized two-dimensional still image;
An intraoral measurement method comprising: The exposure time control step controls the exposure time so that each region of teeth and gingiva in the oral cavity is optimally captured by the imaging step,
The intraoral measurement method according to claim 1. The exposure time control step includes
A data separation step of separating signal data from the video signal obtained in the imaging step;
An exposure time calculating step of calculating the exposure time at the saturation limit in the two-dimensional still image based on the signal data;
An exposure time adjustment step of adjusting the exposure time based on the exposure time calculated in the exposure time calculation step;
The intraoral measurement method according to claim 1 or 2, comprising: The exposure time control step performs setting of the tooth region and the gingival region based on luminance information.
The intraoral measurement method according to any one of claims 1 to 3. An intraoral measurement device for measuring the intraoral area,
A light projecting unit that projects a coded stripe pattern;
An imaging unit that captures a region on which the stripe pattern is projected as a two-dimensional still image;
An exposure time control unit that controls an exposure time so that the imaging unit can optimally capture the two-dimensional still image;
An image synthesis unit that synthesizes the two-dimensional still image captured by at least two different exposure times to generate a synthesized two-dimensional still image;
A three-dimensional calculation unit that calculates three-dimensional coordinates in the oral cavity based on the synthesized two-dimensional still image;
An intraoral measuring device. The exposure time control unit controls the exposure time so that each region of teeth and gingiva in the oral cavity is optimally captured by the imaging unit,
The intraoral measurement apparatus according to claim 5. The exposure time controller is
A data separation unit for separating signal data from a video signal obtained in the imaging unit;
An exposure time calculation unit that calculates the exposure time of the saturation limit in the two-dimensional still image based on the signal data;
An exposure time adjusting unit for adjusting the exposure time based on the exposure time calculated in the exposure time calculating unit;
The intraoral measuring device according to claim 5 or 6, wherein The exposure time control unit performs setting of the tooth region and the gingival region based on luminance information.
The intraoral measurement device according to any one of claims 5 to 7.

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