Abstract:
A method of constructing tooth images utilizes a probe to take images of teeth at one place using a first light ray of wavelength less than or equal to 460 nm and a second light ray of wavelength greater than or equal to 600 nm, thereby generating a first image and a second image. After receiving the first image and the second image, an image processing unit superimposes the first image and the second image to produce a composite tooth image. Using the light of wavelength less than or equal to 460 nm has the advantage of reducing reflection disturbance from saliva, thereby increasing the precision in tooth images.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to a method of constructing tooth images and, in particular, to the method of obtaining composite tooth images with two different wavelengths and superimposing the images. 
         [0003]    2. Description of Related Art 
         [0004]    To build a three-dimensional model for a tooth, one needs to obtain images of the tooth from various perspectives. Take the biting surface as an example. A dentist sticks a probe into the mouth cavity of a patient in order to take images of the biting surfaces of all the teeth in the upper and lower jaws. An image processing unit connected to the probe receives the images. After the image processing unit receives the images and joints them, the complete biting surfaces of the tooth of the patient are obtained. However, the probe in the prior art takes the images with a monochromatic source, such as those in U.S. Pat. Nos. 6,594,539 B1 and 7,312,924 B2. However, objects inside the mouth cavity have different absorption properties. In particular, saliva inside the mouth cavity reflects part of light. The tooth image quality suffers from this, and a lot of details may be missing. 
         [0005]    To ensure the image quality, the dentist usually sprays a saliva inhibiting agent in the mouth of the patient before taking the images, thereby reducing saliva secretion and reflection. However, it is an additional process for the dentists to control the spray thickness and effective saliva inhibiting time. 
       SUMMARY OF THE INVENTION 
       [0006]    In view of the foregoing, an objective of the invention is to provide a method of constructing tooth images using dual-wavelength light. Images obtained using two light sources of different wavelengths are superimposed to overcome difficulties in the prior art. 
         [0007]    The disclosed method of constructing tooth images using dual wavelength light comprises the steps of: 
         [0008]    using a probe to take images of teeth in the mouth cavity at one place using a first light ray of wavelength less than or equal to 460 nm and a second light ray of wavelength greater than or equal to 600 nm, thereby producing a first image and a second image; and 
         [0009]    using an image processing unit to receive the first image and the second image, and to superimpose the first image and the second image to generate a composite tooth image. 
         [0010]    The image processing unit reduces noise and combines details of the two images into the composite tooth image with more detail information and higher accuracy. 
         [0011]    According to experiments, light of wavelength less than or equal to 460 nm is less reflected by saliva. That is, light of wavelength less than or equal to 460 nm is less disturbed by saliva. Therefore, the first image can present details of the teeth. The composite tooth image can enhance the image quality for subsequent three-dimensional tooth model building. Moreover, the invention circumvents the disturbance of saliva through image processing techniques. Therefore, it does not have the trouble of using a saliva inhibiting agent. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a block diagram of a system for implementing the method of the present invention; 
           [0013]      FIG. 2  is a schematic view of a first image taken by a first light source in accordance with the present invention; 
           [0014]      FIG. 3  is a schematic view of a second image taken by a second light source in accordance with the invention; and 
           [0015]      FIG. 4  is a schematic view of a composite tooth image in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0016]    The system employing a method in accordance with the present invention includes a probe  100  and an image processing unit  30 . Please refer to  FIG. 1 . The probe  100  comprises a housing  10  inside which are provided with a driving unit  20 , a first light source  21 , a second light source  22 , a reflecting device  23 , a reflector  24 , and an image capturing device  25 . The image processing unit  30  can be a computer outside the housing  10 . The image processing unit  30  connects to the image capturing device  25  for data transmissions. 
         [0017]    A side surface of the housing  10  has an opening  11 . The first light source  21  and the second light source are disposed opposite to the reflecting device  23 . The reflecting device  23  is mounted on an inner side of the opening  11  and opposite to the opening  11 . Moreover, the reflecting device  23  is located on the light output path of the first light source  21  and the second light source  22 . The light emitted by the first light source  21  and the second light source  22  is reflected by the reflecting device  23  to pass through the opening  11  of the housing  10 , projecting the light outward. The wavelength of the first light source  21  is less than or equal to 460 nm. The wavelength of the second light source  22  is greater than or equal to 600 nm. The reflecting device  23  can be an active or passive reflecting device. The active reflecting device uses Liquid Crystal on Silicon (LCoS) projection technique. After the active reflecting device receives the light from the first light source  21 , only part of the first light source  21  is reflected to a certain region. The passive reflecting device consists of a motor, a transmission mechanism, and a reflecting mirror. The motor drives the transmission mechanism to rotate the reflecting mirror, so that the first light source  21  projects toward a specific region. 
         [0018]    The reflector  24  is disposed on the inner side of the opening  11  of the housing  10 .  FIG. 1  only shows a planar view. In fact, the reflector  24  is disposed parallel to but off the optical path of the first and second light sources  21 ,  22 . Therefore, the reflector  24  does not affect the projection of the first light source  21  and the second light source  22 . The image capturing device  25  and the reflector  24  are disposed opposite to each other. When the light is projected by the first light source  21  or the second light source  22  outward to an object  40 , the object  40  forms an image on the reflector  24 . The image capturing device  25  then extracts the image of the object  40  from the reflector  24  under the light of the first light source  21  or the second light source  22 . The image capturing device  25  can be a CMOS image sensor or CCD image sensor. 
         [0019]    This embodiment uses a tooth on the lower jaw as an example. But the invention is not limited to this example. It can be used for a tooth on the upper jaw as well. The user first puts the opening  11  on the probe  100  above the biting surface of the tooth. At that point, the driving unit  20  drives in sequence the first light source  21  and the second light source  22  to project light onto the biting surface of the tooth. The reflecting device  23  only allows the first light source  21  to project light onto the biting surface of the tooth, instead of the mouth cavity tissue around it (such as the gum part). On the other hand, the second light source  22  simultaneously projects light to the biting surface of the tooth and the surrounding mouth cavity tissue. Therefore, as shown in  FIG. 2 , when the image capturing device  25  takes a photo, a first image  51  is produced under the light of the first light source  21 . The first image contains only the tooth information  511 . As shown in  FIG. 3 , the image capturing device  25  generates a second image  52  under the light of the second light source  22 . The second image  52  simultaneously comprises the tooth information  521  and the mouth cavity tissue information  522 . It is noted that the tooth information  521  in the second image  52  obtained with the second light source  22  is relatively unclear. 
         [0020]    After the probe  100  obtains the first image  51  and the second image  52 , the image processing unit  30  receives the first image  51  and the second image  52  from the image capturing device  25 . With reference to  FIGS. 2 to 4 , the image processing unit  30  superimposes the two images  51 ,  52  to produce a composite tooth image  53 . Since the first image  51  and the second image  52  are taken when the probe  100  is at the fixed point, the spatial configurations presented by the first image  51  and the second image  52  are exactly the same. After the first image  51  and the second image  52  are superimposed, the tooth information  511  of the first image  51  is superimposed on the tooth information  521  of the second image  52 . As a result, the composite tooth image  53  contains detailed tooth information  531  and mouth cavity tissue information  532 . 
         [0021]    For the composite tooth image  53 , the second image  52  taken under the light of the second light source  22  presents the mouth cavity tissue information. The tooth information  531  of the composite tooth image  53  is the combined result of the tooth information  511 ,  521  in the first image  31  and the second image  32 , respectively. As the wavelength of the light from the first light source  21  is less than or equal to 460 nm, the invention can effectively reduce the disturbance due to reflections from saliva inside the mouth cavity. If a CMOS image sensor is used as the image capturing device  25 , it is more sensitive to the wavelength of the first light source  21  and, therefore, can present a very fine appearance for the biting surface of the tooth. Consequently, the tooth information  531  of the composite tooth image  53  can not only enhance the details of the tooth, but also present the margin line between the tooth information  531  and the mouth cavity tissue information  532 , such as the gum line information. The invention is able to clearly identify the tooth and the gum line, providing an accurate tooth image. 
         [0022]    Furthermore, the present invention can be used for single tooth or multiple teeth at one time for upper jaw or lower jaw as well to obtain a composite image containing teeth information. 
         [0023]    While the invention has been described by way of example and in terms of the preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.