Abstract:
Provided is an optical alignment apparatus and method that can enhance the efficiency of optical alignment by using a light source for generating light of a visible wavelength range and lensed fiber and perform optical alignment quickly, precisely and economically. The optical alignment apparatus of the present research includes: a first light source for providing light of a visible wavelength range to perform optical alignment; a second light source providing light of an infrared wavelength range; a micrometer stage for aligning the light outputted from the first light source or the second light source with an active area of a detector; lensed fiber for inputting light into the active area of the detector; an optical alignment confirming means for visually confirming whether the light outputted from the lensed fiber is aligned with the active area of the detector; an image information acquiring means for acquiring image information; and a control means for operating the micrometer stage.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an optical alignment apparatus and method for aligning light of an infrared wavelength range which is used for an optical communication quickly, precisely and economically by using images and a light source generating light of a visible wavelength range; and, more particularly, to an optical alignment apparatus and method that uses the visible light source for optical alignment and enhances the efficiency of optical alignment by using lensed fiber, checks whether the inputted light is aligned with a detector by using a microscope and a charge coupled device (CCD), performs optical alignment between the inputted light and the detector by using a control circuit connected to the CCD and moving an X, Y, Z, Tilt micrometer stage, and then performs optical alignment between the light that has an infrared wavelength and the detector by inputting the light that has an infrared wavelength.  
         DESCRIPTION OF RELATED ART  
         [0002]    One of optical alignment methods performs optical alignment by using the optical intensity of inputted light. To describe it in detail, optical alignment is performed by inputting light having a predetermined optical intensity to an active area of a detector, and detecting a point where the optical intensity of the inputted light is measured to be the maximum in the detector. However, this method that uses the optical intensity can hardly confirm whether optical alignment is performed exactly. Moreover, it is hard to manually detect the point where the optical intensity is the maximum. In case where optical alignment is performed automatically, it takes a little time and an expensive instrument is needed to measure the optical intensity.  
           [0003]    Another optical alignment method utilizes a light emitting diode (LED) and a CCD camera. This method will be described below with reference to FIG. 1.  
           [0004]    [0004]FIG. 1 is a diagram describing the prior optical alignment method. In this method, light outputted from the LED  110  meets an active area  140  of the detector  130  and is reflected.  
           [0005]    The reflected light goes to a reflector  170  through a beam splitter  150 , and the light reflected from the reflector  170  enters a CCD camera  180 . Through these processes, an optical system  120  is aligned with the active area  140  of the detector  130 . First, the optical system  120  and the active area  140  of the detector  130  are aligned by using images of the optical system  120  and the active area  140  of the detector  130  and then light  190  is inputted. The light  190  is transmitted to the detector  130  through the optical system  120 , and the light reflected from the detector  130  is transmitted to the CCD camera  180  through a beam splitter  150  and the reflector  170 . From the CCD camera  180 , it can be known on what part of the detector  130  the inputted light  190  is focused. Also, the inputted light  190  can be brought into a focus in the active area  140  of the detector  130  by moving the optical system  120  based on the difference between focus of previous alignment by LED  110  and focus of the light  190 . In this method, the Z axis and tilt are out of consideration, and the optical system  120  and the active area  140  are aligned with respect to the X and Y axes. In order for the inputted light to be seen in the CCD camera  180 , the inputted light should be in the range of visible wavelength. Therefore, this method cannot be used for communication. To be used for communication, the above method requires an expensive infrared camera.  
           [0006]    As described above, the conventional methods have advantages and disadvantages of their own, and a new technology needs to be developed to solve the problems of the conventional technologies and perform optical alignment quickly, precisely and economically.  
         SUMMARY OF THE INVENTION  
         [0007]    It is, therefore, an object of the present invention to provide an optical alignment apparatus and method that can enhance the efficiency of optical alignment by using a light source which generates light of a visible wavelength range and a lensed fiber, and perform optical alignment quickly, precisely and economically.  
           [0008]    In accordance with an aspect of the present invention, there is provided an optical alignment apparatus using visible light and images, including: a first light source for providing light of a visible wavelength range to perform optical alignment; a second light source providing light of an infrared wavelength range; a micrometer stage for aligning the light outputted from the first light source or the second light source with an active area of a detector; a lensed fiber connected to the micrometer stage, for inputting the light outputted from the first light source or the second light source into the active area of the detector; an optical alignment confirming unit for visually confirming whether the light outputted from the lensed fiber is aligned with the active area of the detector; an image information acquiring unit connected to the optical alignment confirming unit, for acquiring image information; and a control unit for operating the micrometer stage by using the image information acquired by the image information acquiring unit to perform optical alignment.  
           [0009]    In accordance with another aspect of the present invention, there is provided an optical alignment apparatus including: an optical coupler for connecting the first light source and the second light source simultaneously and outputting inputted light in a predetermined proportion; a compensation unit for compensating a difference in distances to a beam waist, the difference being generated by different wavelengths of the first light source and the second light source; and an optical intensity supervising unit for controlling optical intensity of light inputted to an active area of a detector by connecting the optical intensity supervising unit with an output port of the optical coupler which is not coupled with the detector.  
           [0010]    In accordance with another aspect of the present invention, there is provided an optical alignment method using visible light and images, comprising the steps of: a) aligning the light outputted from a light source with an active area of a detector; b) inputting the light outputted from the light source into the active area of the detector through an optical coupler and lensed fiber; c) visually confirming on what part of the active area of the detector the light transmitted through the lensed fiber is focused by using a microscope, and providing image information, which shows an extent of optical alignment and is provided by a charge coupled device connected to the microscope, to a control circuit unit; d) controlling the micrometer stage to perform optical alignment by using the image information provided by the charge coupled device in the control circuit unit; and e) performing optical alignment between the lensed fiber and the active area of the detector by operating the micrometer stage under the control of the control circuit unit.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The above and other objects and features of the present invention will become apparent from the following description of the preferred embodiments given in conjunction with the accompanying drawings, in which:  
         [0012]    [0012]FIG. 1 is a diagram describing a prior optical alignment method;  
         [0013]    [0013]FIG. 2 is a block diagram illustrating an optical alignment apparatus using a visible optical source and images in accordance with a preferred embodiment of the present invention; and  
         [0014]    [0014]FIGS. 3A and 3B are graphs illustrating the size of beam waist in accordance with a preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    Other objects and aspects of the invention will become apparent from the following description of the embodiments with reference to the accompanying drawings, which is set forth hereinafter.  
         [0016]    [0016]FIG. 2 is a block diagram illustrating an optical alignment apparatus using a visible optical source and images in accordance with a preferred embodiment of the present invention. FIGS. 3A and 3B are graphs illustrating the size of beam waist in accordance with a preferred embodiment of the present invention.  
         [0017]    Referring to FIG. 2, the optical alignment apparatus of the present invention includes: a first light source  200  for generating light of a visible wavelength range and used for optical alignment; a second light source  210  for generating light of an infrared wavelength range and used for optical communication; an optical coupler  220  for connecting the first light source  200  and the second light source  210  simultaneously and supervising optical alignment and optical intensity simultaneously; a first input port  221  of the optical coupler  220 ; a second input port  222  of the optical coupler  220 ; a first output port  223  of the optical coupler  220 ; a second output port  224  of the optical coupler  220 ; lensed fiber  240  for collecting the light from the first output port  223  of the optical coupler  220  in an active area  251  of a detector  250 ; an X, Y, Z, Tilt micrometer stage  230  for aligning the lensed fiber  240  with the active area  251  of the detector  250 ; the detector  250  which is aligned with the light outputted from the first light source  200  or the second light source  210 ; a microscope  260  for visually confirming whether the light outputted from the first light source  200  is aligned with the active area  251  of the detector  250 ; a charge coupled device (CCD)  270  for performing optical alignment by using images seen in the microscope  260 ; a control circuit unit  280  for aligning the light outputted from the first light source  200  with the active area  251  of the detector  250  by using the image seen in the CCD  270  and moving the X, Y, Z, Tilt micrometer stage  230 ; and an optical intensity supervising unit  290  for maintaining the intensity of light at a predetermined level.  
         [0018]    The light outputted from the first light source  200  or the second light source  210  is inputted to the first input port  221  or the second input port  222  of the optical coupler  220  and outputted through the first and second output ports  223  and  224  simultaneously. The optical intensity supervising unit  290  connects the first or second light source  200  or  210  and the second output port  224  to maintain the intensity of light from the first output port  223  at a predetermined level.  
         [0019]    Hereinafter, the optical alignment apparatus of the present invention having the above described elements will be described more in detail. The light outputted from the first light source  200  of the visible wavelength range is aligned with the active area  251  of the detector  250 . The light outputted from the first light source  200  is inputted into the active area  251  of the detector  250  through the optical coupler  220  and the lensed fiber  240 .  
         [0020]    Since the light from the first light source  200  is in the range of visible wavelengths, it can be confirmed visually on what part of the active area  251  of the detector  250  the light transmitted through the lensed fiber  240  is focused. The CCD  270  connected to the microscope  260  provides image information which reveals the extent of optical alignment to the control circuit unit  280 . The control circuit unit  280  controls the X, Y, Z, Tilt micrometer stage  230  to perform optical alignment by using the image information transmitted from the CCD  270 .  
         [0021]    The X, Y, Z, Tilt micrometer stage  230  performs optical alignment between the lensed fiber  240  and the active area  251  of the detector  250  under the control of the control circuit unit  280 . The light outputted from the first light source  200  is aligned with the active area  251  of the detector  250  precisely by repeating the above processes.  
         [0022]    After the optical alignment between the lensed fiber  240  and the active area  251  of the detector  250 , the first light source  200  is turned off, and the second light source  210  which provides light of the infrared wavelength range is turned on. The wavelengths of the light from the first light source  200  and the light from the second light source  210  are different. So, there is a difference in a distance from a lensed fiber  240  to a beam waist between the first light source  200  and the second light source  210 .  
         [0023]    The difference in the distance from a lensed fiber  240  to the beam waist, which is caused by the difference in the wavelengths of the light transmitted from the first and second light sources may be compensated or not compensated. Whether to compensate or not is determined based on the size of the active area  251  of the detector  250  and the kind of the lensed fiber  240 . If it needs to be compensated, the Z axis is moved as much as needed by using the X, Y, Z, Tilt micrometer stage  230   
         [0024]    For example, when the first and second light sources  200  and  210  generate light of 635 nm and 1550 nm, respectively, and the size of the active area  251  of the detector  250  is 30 um, whether to compensate for the difference in the distances to the beam waist is determined as follows.  
         [0025]    Let&#39;s define that T is the lens thickness of the lensed fiber  240  and Rc is the curvature radius of the lensed fiber  240 . First, when a T value and an Rc value of the lensed fiber are 400 um and 92 um, respectively, the distance from the lensed fiber  240  to the beam waist of the first light source  200  is 380 um and the distance from the lensed fiber  240  to the beam waist of the second light source  210  is 450 um. Here, the distance difference between the first and second light sources  200  and  210  is 70 um. In FIG. 3A, the size of the beam waist of the second light source  210  is 22.8 um and the size of the waist at a location  70  um away from the beam waist position is around 25 um. Since the size of the active area  251  of the detector  250  is 30 um, no compensation needs to be made on the Z axis.  
         [0026]    Secondly, when the T value and Rc value of the lensed fiber  240  are 520 um and 78 um, respectively and the distance from the lensed fiber  240  to the beam waist of the first light source  200  is 286 um and the distance from the lensed fiber  240  to the beam waist of the second light source  210  is 300 um. Here, the distance difference between the first and second light sources  200  and  210  is 14 um. In FIG. 3B, the size of the beam waist of the second light source  210  is 10 um and the size of the waist at a location  14  um away from the beam waist position is about 13 um. Since the size of the active area  251  of the detector  250  is 30 um, no compensation needs to be made on the Z axis. If the kind of lensed fiber  240  is proper to the size of the active area of the detector, the difference in the distances to the beam waist, which is generated due to the difference in the wavelengths of the light generated by the light sources, needs not be compensated.  
         [0027]    The light outputted from the first light source  200  or the second light source  210  is transmitted to the first output port  223  and the second output port  224  of the optical coupler  220  in a predetermined proportion. If the optical intensity of the light transmitted to the first output port  223  needs to be maintained at a predetermined level, the optical intensity of the light outputted from the first or second light source  200  or  210  is controlled by supervising the optical intensity of the light transmitted to the second output port  224 .  
         [0028]    In the present invention, the light outputted from a light source can be aligned with the active area of the detector by using the light of the visible wavelength range. As described before, many methods for aligning the light outputted from a light source with the active area of the detector are disclosed in the prior researches. One of the commercialized methods is a structure that performs optical alignment by measuring the optical intensity of the light outputted from a light source.  
         [0029]    The technology of the present invention, however, is very economical because it does not require special equipment for measuring the optical intensity of inputted light owing to the use of the visible light source. Since it uses images to perform optical alignment between the light and the active area of the detector, it can perform the optical alignment quickly. Also, when the kind of lensed fiber is proper to the size of the active area of the detector, the optical alignment can be performed precisely even without compensation for the difference in the distances to the beam waist, which occurs due to the use of different light sources. In addition, the optical intensity of the light inputted to the active area of the detector can be controlled at a predetermined level by using the optical coupler and an optical intensity supervising unit.  
         [0030]    In accordance with the present invention, the optical alignment can be performed quickly, precisely and economically by using the visible light source and images to determine whether the light outputted from the visible light source is aligned with the active area of the detector. Therefore, the cost for performing optical alignment can be reduced and an optical alignment apparatus that can perform optical alignment at an inexpensive cost can be fabricated.  
         [0031]    While the present invention has been described with respect to certain preferred embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined in the following claims.