Abstract:
The present disclosure relates to an OCT device, which can be simply mounted without changing the structure of a microscope or an endoscope, thereby realizing an OCT system and, more particularly, to a removable OCT device including: a tunable laser configured to emit light to the light output side of an optical device by tuning the wavelength of the light; a first beam splitter installed on a path of the light emitted from the tunable laser; and a reference mirror installed on a path of the light that has passed through the first beam splitter, wherein the removable OCT device is mounted at the light output side of the optical device.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a removable OCT (Optical Coherence Tomography) device and, more particularly, to an OCT device which can be simply mounted without changing the structure of a microscope or an endoscope to implement an OCT system. 
       BACKGROUND ART 
       [0002]    An OCT device is a device capable of taking tomography images of a human body using interference of light in the infrared band. At the initial stage of technology development, it was possible to obtain images of several frames per second by changing the optical path mechanically. Nowadays, tomography images of several hundred frames per second can be taken by employing a three-dimensional OCT technique that makes use of a wavelength tunable laser and a high-speed digitizer. 
         [0003]      FIG. 1 , shows a conventional OCT device and a microscope equipped with the OCT device. The conventional OCT device captures tomography images with an interference signal of the signal light and the reference light by bypassing the light of an object incident on the microscope. 
         [0004]    However, since the OCT device of the type shown in  FIG. 1  requires a portion (A) (a beam splitter or the like) of the OCT device to be interposed between the main body of the microscope or the like and the objective lens (B) in order to bypass the signal light. This raises a problem that installation of the OCT device is difficult and that the alignment of precision equipment such as a microscope or the like is disturbed. 
         [0005]      FIG. 2 , shows an endoscope in which an OCT device is integrally formed. The endoscope in which the OCT device is integrally formed therewith can simultaneously perform the functions of the endoscope and the OCT device because a transducer and a optical fiber for a light source are formed within the endoscope. 
         [0006]    However, the OCT device of the type shown in  FIG. 2  suffers from a problem that all existing conventional endoscopes should be discarded and replaced by new ones, which leads to excessive waste of resources. 
       SUMMARY 
       [0007]    Embodiments of the present disclosure solve the problems mentioned above. In some embodiments, a removable OCT device is capable of being easily installed and removed and minimizing a change of an existing optical device such as a microscope. 
         [0008]    A removable OCT device according to one embodiment includes: a tunable laser configured to emit light to a light output side of an optical device by tuning a wavelength of the light; a first beam splitter installed on a path of the light emitted from the tunable laser; and a reference mirror installed on a path of the light that has passed through the first beam splitter, wherein the removable OCT device is mounted at the light output side of the optical device. 
         [0009]    The removable OCT device may be used in state in which the removable OCT device is mounted on the light output side of an existing optical device. It is therefore possible to remarkably reduce the risk of misalignment or damage of the existing optical device. 
         [0010]    Furthermore, the removable OCT device may be mounted while maintaining the existing optical device. It is therefore possible to use the existing optical device without having to discard the same. 
         [0011]    Moreover, the removable OCT device may be easily attached and detached. It is therefore possible to use the OCT device by installing the same in one or more optical devices. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  shows a conventional OCT device and a microscope equipped with the OCT device. 
           [0013]      FIG. 2  shows an endoscope with which the OCT device is integrally formed. 
           [0014]      FIG. 3  is a structural diagram of a removable OCT device according to a first embodiment of the present disclosure. 
           [0015]      FIG. 4  is a structural diagram of a removable OCT device according to a second embodiment of the present disclosure. 
           [0016]      FIG. 5  shows a use state in which the removable OCT device according to the first embodiment of the present disclosure is mounted to an endoscope. 
           [0017]      FIG. 6  shows a use state in which the removable OCT device according to the second embodiment of the present disclosure is mounted to a microscope. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    A removable OCT device according to the present disclosure will now be described in detail with reference to the accompanying drawings. 
         [0019]      FIG. 3  is a structural diagram of a removable OCT device according to a first embodiment of the present disclosure. The removable OCT device according to the present embodiment is a device mounted at the light output side of an optical device such as an endoscope, a microscope or the like (at the same side as an ocular lens) and simultaneously acquires a visible light image and an OCT image. The removable OCT device includes a tunable laser  10 , a first beam splitter  20 , a reference mirror  30 , a second beam splitter  40 , a band pass filter unit  50  and an image detector unit  60 . The removable OCT device may further include a vibration compensator  70  and an image processor (not shown). 
         [0020]    The tunable laser  10  is a component which emits light to the light output side while tuning the wavelength so that the human body tissue can be taken tomographically by depth, and which makes sure that an infrared ray is reflected from a measurement target object (a human body or the like) to be measured by an optical device (that the light incident on the light output side reaches the measurement target object through the optical device). In some embodiments, the wavelength is tuned in the infrared region of 750 to 1300 nm. As the wavelength grows longer, the depth of infiltration of the light into the human body tissue becomes deeper. Thus, by emitting light while changing the wavelength of the light from a short wavelength to a long wavelength, it is possible to acquire stereoscopic interference signals from the surface of the human body tissue to a predetermined depth. An OCT can be implemented by image-processing the interference signals. The tunable laser  10  may further include an LED, a lamp or the like, which covers a visible ray region, so that the tunable laser  10  can provide a visible ray when the amount of the visible ray emitted from the measurement target object is deficient. 
         [0021]    The first beam splitter  20  is a component which generates a reference light (light for setting a phase reference plane) by allowing a portion of the light emitted from the tunable laser  10  to pass through the first beam splitter  20  and to move toward the reference mirror  30 , and generates a signal light (a light reflected or emitted from the measurement target object and containing information of the measurement target object) by reflecting a portion of the light emitted from the tunable laser  10  and allowing the light to move toward the light output side. The first beam splitter  20  is configured to reflect the reference light reflected from the reference mirror  30  and is configured to allow the signal light emitted from the light output side to pass through the first beam splitter  20  and to move toward the second beam splitter  40 . Information on the measurement target object can be obtained by causing the reference light and the signal light, which are generated by the first beam splitter  20  in this way, to interfere with each other. 
         [0022]    The reference mirror  30  is a component which reflects the light passed through the first beam splitter  20  and generates a reference light, namely a light to be compared with phase-shifted signal light. 
         [0023]    The second beam splitter  40  is a component which allows a portion of the light emitted from the light output side and the light emitted from the reference mirror  30  to pass through the second beam splitter  40  while it reflects the other portion to divide the optical path into two. Since the second beam splitter  40  is installed on an optical path of the light emitted from the light output side and passed through the first beam splitter  20 , the reference light and the signal light are incident on the second beam splitter  40 . The removable OCT device according to the present embodiment is configured to simultaneously pass a visible ray of a typical optical device and an infrared ray emitted by the tunable laser  10 . Thus, the removable OCT device includes an infrared ray image detector  62  and a visible light image detector  64  in order to separately take an image of the visible ray and the infrared ray. The second beam splitter  40  splits the light to be incident on the infrared image detector  62  and the visible light image detector  64 . 
         [0024]    The band pass filter unit  50  is a component which filters the light to be incident on the infrared image detector  62  and the visible light image detector  64 . The band pass filter unit  50  may include an infrared band pass filter  52  installed on a path of one of the light beams split in the second beam splitter  40  and may further include a visible ray band pass filter  54  installed on a path of the other of the light beams split in the second beam splitter  40 . In the removable OCT device according to the present disclosure, the infrared image detector  62  has to receive only an electromagnetic wave of an infrared band as a signal. Thus, it is necessary to provide the infrared band pass filter  52  which passes the light of an infrared band. The visible ray band pass filter  54  is an optional component. In general, a CCD or CMOS image detector is sufficient to take visible light images. Thus, the visible ray band pass filter  54  may be provided when one wishes to enhance the purity of a visible light image by removing the light in the infrared band. 
         [0025]    The image detector unit  60  may include an infrared image detector  62  and a visible light image detector  64 . On the basis of a travel direction of light, the infrared image detector  62  is installed behind the infrared band pass filter  52 , and the visible light image detector  64  is installed behind the second beam splitter  40  or the visible ray band pass filter  54 . In this regard, the rear side of the second beam splitter  40  refers to a travel path of the light other than the light which is separated by the first beam splitter  20  and is incident on the infrared image detector  62 . 
         [0026]    The infrared image detector  62  has to take infrared images in a wavelength range of 750 to 1300 nm. Thus, different types of image detectors are used depending on the wavelength range. Specifically, in the wavelength range of 750 to 1100 nm, a typical CCD or CMOS image detector like the visible light image detector  64  may be used. However, since the typical CCD or CMOS image detector cannot detect an infrared ray of a wavelength of 1100 nm or more, an InGaAs image detector is used. The visible light image detector  64  is an image detector used in a typical digital camera. A CCD or CMOS image detector is used as the visible light image detector  64 . 
         [0027]    By providing a plurality of infrared ray image detectors  62 , it is possible to improve the quality of an OCT image. For example, when images are taken by installing two infrared ray image detectors  62  and synchronizing the image-taking timings thereof, it is possible to obtain two-fold images per unit time and to obtain OCT images having a high quality. When one wishes to obtain images of the same quality, it is possible to shorten the image-taking time by one half. Thus, the images are less susceptible to vibration and are somewhat free from the restrictions in the performance of the vibration compensator  70 . 
         [0028]    The visible light image detector  64  may be an ocular lens. Since the human eyes may be regarded as one kind of the visible light image detector  64 , it is possible to implement an OCT device capable of taking infrared images with the infrared image detector  62  while seeing visible light images through an ocular lens. In this case, the human eyes serve as the visible ray band pass filter  54 . Thus, by removing the visible ray band pass filter  54 , it is possible to simplify the configuration of the OCT device. 
         [0029]    The vibration compensator  70  is a component which compensates the vibration of the lens or the image detector unit  60 . The vibration compensator  70  may be an actuator (of hardware type) which mechanically compensates the vibration of the lens or the image detector unit  60  by measuring the vibration, or may be a processor (of software type) which compensates the vibration through image correction by matching the measured images. In the removable OCT device according to the present disclosure, the vibration compensation is needed for the following reason. Due to the characteristics of the OCT device, a plurality of images is taken within a short period of time while tuning the wavelength (namely, while changing the image-taking depth). At this time, if vibration or position shift occurs, an error may be generated in a stereoscopic image. The hardware type vibration compensator  70  is configured to physically cancel the actual vibration. The software type vibration compensator  70  is configured to compensate the error, which is generated in the image due to the vibration, through an image processing process. 
         [0030]    The image processor (not shown) is a component which is connected to the image detector unit  60  and configured to process the visible light images and the infrared images acquired in the image detector unit  60 . Specific forms of the image processor include a field programmable gate array (FPGA), a digital signal processor (DSP), an ARM, and the like. 
         [0031]      FIG. 4  is a structural diagram of a removable OCT device according to a second embodiment of the present disclosure. The removable OCT device according to the present disclosure is mounted to the light the output side of a binocular optical device. The removable OCT device includes a tunable laser  10 , a pair of first beam splitters  20 , a reference mirror  30 , a pair of second beam splitters  40 , a pair of band pass filter units  50  and a pair of image detector units  60 . The removable OCT device may further include a vibration compensator  70  and an image processor. It can be said that the removable OCT device according to the second embodiment of the present disclosure is configured to be binocular, namely as a stereo system, by combining, in parallel, two removable OCT devices according to the first embodiment of the present disclosure. Accordingly, the removable OCT device according to the second embodiment of the present disclosure is useful in a device such as a microscope. 
         [0032]    In order to take images by separating an infrared ray and a visible ray, the first beam splitters  20 , the second beam splitters  40 , the band pass filter units  50  and the image detector units  60  are respectively provided in a pair. The tunable laser  10  may be provided in a pair. Since it is desirable to irradiate the same light on an object, it is preferred that there is provided only one tunable laser  10 . Furthermore, a pair of reference mirrors  30  may be provided and may be respectively installed at the rear side of the first beam splitters  20 . Alternatively, one double-sided mirror may be installed as the reference mirror  30 . A pair of vibration compensators  70  and a pair of image processors may be provided, one in each of the image detector units  60 . Alternatively, one vibration compensator  70  and one image processor may be provided in the image detector units  60  as a whole. 
         [0033]      FIG. 5  shows a use state in which the removable OCT device according to the first embodiment of the present disclosure is mounted to an endoscope.  FIG. 6  shows a use state in which the removable OCT device according to the second embodiment of the present disclosure is mounted to a microscope. It can be noted that the removable OCT device  100  according to the present disclosure can be easily mounted to and removed from an existing optical device such as an endoscope, a microscope or the like.