Abstract:
A laser treatment apparatus for irradiating an affected part of a patient&#39;s eye with a treatment laser beam to treat the affected part is disclosed. The laser treatment apparatus includes treatment beam irradiation section including a first irradiation optical system for irradiating the treatment beam; aiming beam irradiation section including a second irradiation optical system for irradiating an aiming beam, the second irradiation optical system being optically adjusted such that sighting of the treatment beam is completed when the aiming beam forms a predetermined shape on a reflection plane; image pickup section including an image pickup optical system for imaging an area including the affected part of the patient&#39;s eye; sighting detection section for processing an image of the aiming beam picked-up by the image pickup section to detect a sighting state; movement detection section for detecting movement in an optical axis direction of at least one of at least a part of the image pickup optical system and at least a part of the irradiation optical system; and determination section for determining a direction in which at least one of at least the part of the image pickup optical system and at least the part of the irradiation optical system is to be moved based on results detected by the sighting detection section and the movement detection section respectively.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a laser treatment apparatus for irradiating an affected part of a patient&#39;s eye with a treatment laser beam. 
     2. Description of Related Art 
     For treatment for aftercataract and so on of a patient&#39;s eye, there conventionally has been used a laser treatment apparatus (laser operation equipment) for irradiating an affected part of the patient&#39;s eye with a treatment laser beam of pulse wave. The apparatus of this kind is designed to vaporize and crush the tissue of the affected part by focusing the treatment laser beam on a desired point (an area to be treated) of the affected part, thereby forming plasma to generate shock waves. Accordingly, the importance is to precisely focus the treatment laser beam on the desired point. For achieving this purpose, there has been known a method of focusing a treatment laser beam on a desired point after irradiating two (or more) visible aiming beams so as to coincide with each other (i.e., to overlap two images of the aiming beams) at the desired point on which the treatment laser beam is to be focused. It is to be noted that the coincidence of two aiming beams at the desired point for the focusing of the treatment laser beam on the desired point is referred hereinafter to as “sighting”. 
     Moreover, there is a method of shifting a focus point of the treatment laser beam to the coincident point of the aiming beams. In this case, the sighting is also important. 
     For treatment for retinal diseases, there has been used a laser treatment apparatus (photocoagulation apparatus) for irradiating an affected part of a patient&#39;s eye with a treatment laser beam of continuous wave. The apparatus of this type is designed so that a visible aiming beam is irradiated to focus on a desired point which is the same as a focus point of the treatment laser beam to form an image with the minimum spot diameter, whereby the treatment laser beam is precisely focused on the desired point. It is also noted that the focusing of the aiming beam on the desired point to ensure the focusing of the treatment laser beam thereon is also referred to as “sighting”. 
     The sighting, however, is performed by an operator while observing the coincident state of the two aiming beams (the overlapping condition of the two images of the aiming beams) or the focusing condition of the aiming beam (the spot diameter of the image of the aiming beam) through eyepieces of a microscopic section of the apparatus. This would cause a difficulty for low-skilled operators in judging the propriety of the sighting. Furthermore, differences among operators may be included in determinations about the propriety of the sighting. 
     During treatment, for example, during sighting of the aiming beams or irradiating of the treatment laser beam, the operator has to observe the patient&#39;s eye through the eyepieces of the microscopic section while holding a contact lens by one hand on the patient&#39;s eye. Thus, some operators who are for example of short stature must operate and observe in a forced or uncomfortable position. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide a laser treatment apparatus which allows an operator to easily observe a patient&#39;s eye and to precisely easily perform sighting in order to focus a treatment laser beam on a desired point. 
     Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
     To achieve the purpose of the invention, there is provided a laser treatment apparatus for irradiating an affected part of a patient&#39;s eye with a treatment laser beam to treat the affected part, including: treatment beam irradiation means including a first irradiation optical system for irradiating the treatment beam; aiming beam irradiation means including a second irradiation optical system for irradiating an aiming beam, the second irradiation optical system being optically adjusted such that sighting of the treatment beam is completed when the aiming beam forms a predetermined shape on a reflection plane; image pickup means including an image pickup optical system for imaging an area including the affected part of the patient&#39;s eye; sighting detection means for processing an image of the aiming beam picked-up by the image pickup means to detect a sighting state; movement detection means for detecting movement in an optical axis direction of at least one of at least a part of the image pickup optical system and at least a part of the irradiation optical system; and determination means for determining a direction in which at least one of at, least the part of the image pickup optical system and at least the part of the irradiation optical system is to be moved based on results detected by the sighting detection means and the movement detection means respectively. 
     It is preferable that the laser treatment apparatus further includes observation means including a display for displaying an image picked up by the image pickup means on the display. 
     It is preferable that the laser treatment apparatus further includes display control means for causing the display to display that the sighting state is proper based on the result detected by the sighting detection means. 
     It is further preferable that the laser treatment apparatus further includes display control means for causing the display to display the direction in which at least one of at least the parts of the image pickup optical system and the irradiation optical system are to be moved based on the result detected by the determination means. 
     Preferably, in the laser treatment apparatus the display is place-changeably mounted on the apparatus. 
     It is preferable that the laser treatment apparatus further includes movement means for automatically moving at least one of at least the part of the image pickup optical system and at least the part of the irradiation optical system based on the result detected by the determination means. 
     It is preferable that the laser treatment apparatus further includes: movement means for automatically moving at least one of at least the part of the image pickup optical system and at least the part of the irradiation optical system; and movement control means for controlling the movement means to move at least one of at least the part of the image pickup optical system and at least the part of the irradiation optical system by a predetermined amount in a predetermined direction based on an instruction to start automatic sighting. 
     Preferably, in the laser treatment apparatus the aiming beam irradiation means irradiates a plurality of aiming beams which are symmetrical about an optical axis to coincide with each other at a focus point of the treatment laser beam, and the sighting detection means detects the sighting state based on an overlapping condition of the images of the plurality of aiming beams. 
     Preferably, in the laser treatment apparatus the aiming beam irradiation means irradiates the aiming beam to focus on a focus point of the treatment laser beam, and the sighting detection means detects the sighting state based on a spot diameter of the image of the aiming beam. 
     Preferably, in the laser treatment apparatus the treatment beam irradiation means includes a laser source which emits a YAG laser beam as the treatment laser beam. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification illustrate an embodiment of the invention and, together with the description, serve to explain the objects, advantages and principles of the invention. 
       In the drawings, 
         FIGS. 1A and 1B  are schematic perspective views of a laser treatment apparatus in a first embodiment according to the present invention; 
         FIG. 2  is a schematic sectional view of a mechanism for mounting a display on a main unit in the first embodiment; 
         FIG. 3  is a schematic structural view of a mechanism for detecting moving directions of the main unit; 
         FIG. 4  is a schematic structural view of an optical system and a control system of the apparatus in the first embodiment; 
         FIGS. 5A ,  5 B, and  5 C are explanatory views of showing a method of detecting a coincident state of aiming beams by image processing; 
         FIGS. 6A and 6B  are examples of a screen appearing on the display; 
         FIG. 7  is an explanatory view of showing a method of finding a deviation direction of the aiming beams; 
         FIG. 8  is a flowchart of showing a routine of automatic sighting in the first embodiment; 
         FIG. 9  is a schematic perspective view of a laser treatment apparatus in a second embodiment according to the present invention; 
         FIG. 10  is a schematic structural view of an optical system and a control system of the apparatus in the second embodiment; and 
         FIG. 11  is a flowchart of showing a routine of automatic sighting in the second embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A detailed description of preferred embodiments of a laser treatment apparatus embodying the present invention will now be given referring to the accompanying drawings. 
       FIG. 1  is a schematic perspective view of the laser treatment apparatus (YAG laser operation apparatus) in the first embodiment according to the present invention. 
     Numeral  1  is a main unit of the apparatus for emitting a treatment laser beam (which is hereinafter simply referred to as a treatment beam) of pulsed wave. This main unit  1  is internally provided with a treatment laser source, an aiming laser source, a light delivery optical system, a controller, and others. Numeral  2  is a stand with a table which is movable up and down, on which the main unit  1  is mounted. Numeral  4  is a joystick used for moving the main unit  1  on the table of the stand  2  in a back-to-front and right-to-left directions. The joystick  4  is provided at its upper portion with a rotating knob which is used for moving the main unit  1  up and down. The moving mechanism of the main unit  1  by means of the joystick and the rotating knob are well known, of which explanation is therefore omitted. The joystick  4  is also provided at its top portion with a trigger switch  4   a  for generating an instruction signal to start emission of the treatment beam. Numeral  3  is a control panel used for setting laser irradiation conditions such as the number of pulses of the treatment beam, the power of the same, and the luminous intensity of an aiming laser beam (which is hereinafter simply referred to as an aiming beam), and others. 
     Numeral  5  is a display for displaying information (data) transmitted from a CCD camera  26  and a controller  30  (which will be mentioned later) through a cable  7 . This display  5  is attached on a rack  6  fixedly provided to the main unit  1  as shown in  FIG. 1A , and is removable from the rack  6  as shown in  FIG. 1B . The display  5  can thus be used in any place where an operator wishes. 
     The display  5  is attached on the rack  6  under the condition that a support shaft  6   a  of the rack  6  is inserted in a hole  5   a  of the display  5  as shown in  FIG. 2 . The display  5  is rotatable about the support shaft  6   a.    
     Numeral  8  is an axle for moving the main unit  1  in a forward (an arrow F in  FIGS. 1A and 3 ) direction and a backward (an arrow B) direction. As shown in  FIG. 3 , in the main unit  1  a potentiometer  9  is attached on the axle  8  through gears, whereby to allow detection of a moving direction (and also a moving amount) of the main unit  1  on the basis of a rotating direction of the axle  8  (and also a rotating amount). Information (data) on a detected moving direction (and also a moving amount) is used in a sighting operation for focusing of the treatment beam. 
       FIG. 4  is a schematic structural view of an optical system and a control system of the apparatus in the first embodiment. Numeral  10  is a Nd:YAG laser serving as a treatment laser source which emits a treatment beam having a dominant wavelength of 1064 nm. Numeral  11  is a half-wavelength plate for rotating the direction of polarization of the treatment beam. Numeral  12  is a polarizing filter placed at the Brewster angle. The wavelength plate  11  is rotated by operation of an energy adjusting knob not shown to adjust the power of the treatment beam to be irradiated to the affected part in combination with the polarizing filter  12 . Numeral  13  is a beam splitter. A part of the treatment beam passed through the polarizing filter  12  is reflected by the beam splitter  13  to enter a power sensor  14  which detects the power of the treatment beam. 
     Numeral  15  is a safety shutter serving to intercept the treatment beam when inserted on the beam path in a predetermined case for example of an oscillation test or occurrence of an abnormal event. While the shutter  15  is out of the beam path, the treatment beam being not intercepted by the shutter  15  is expanded by a group of expander lenses  16 . The treatment beam is then reflected by a dichroic mirror  17  to made coaxial with the aiming beam (which is a red light having a dominant wavelength of 633 nm) emitted from a semiconductor laser  18  serving as an aiming laser source. The aiming beam emitted from the laser source  18  is made into parallel luminous flux by a lens  19  and split into two beams by an aperture  20  having two openings formed symmetrically with respect to an optical axis L. 
     Numeral  21  is a group of expander lenses for expanding each luminous flux of the treatment beam and the aiming beam. Numeral  22  is a dichroic mirror which reflects most of the treatment beam and the aiming beam, while transmitting an observation light, whereby to make the optical axis L coaxial with the optical axis of an objective lens  23 . The treatment beam, after reflected by the dichroic mirror  22 , is focused on a point near the affected part of the patient&#39;s eye E through the objective lens  23  and a contact lens  24 . The two split aiming beams are reflected by the dichroic mirror  22  and coincide with each other at a reference focus point of the treatment beam. The focus point of the treatment beam may be shifted with respect to the coincident point of the aiming beams by movement of the expander lenses  16  in the optical axis direction. 
     Numeral  25  is a slit light projecting optical system. The slit light from the projecting optical system  25  is delivered to illuminate the eye E through the contact lens  24 . 
     Numeral  26  is a CCD camera for receiving the reflection light from the eye E. The image picked-up by the CCD camera  26  is displayed on the display  5 . 
     Numeral  30  is a controller for controlling the whole apparatus. Numeral  31  is an image processing section for processing the images of the two aiming beams picked-up by the camera  26  to detect the overlapping condition of the images. 
     Next, explanation is made on a method of detecting the overlapping condition (coincident state) of the images of the aiming beams by image processing, referring to  FIG. 5 .  FIG. 5  is an explanatory view of the method of detecting the overlapping condition of the aiming beams by extracting only the images of the aiming beams and its surrounding area picked-up by the camera  26 . 
     In  FIG. 5 , numerals  50   a  and  50   b  denote the images of the two split aiming beams irradiated in two directions to the eye E. For example, they are the images of the aiming beams reflected at the desired point (the area to be treated) such as a point in posterior capsule and picked-up by the camera  26 . 
     The image processing is executed in the following manner. The image processing section  31  first extracts the images  50   a  and  50   b  of the aiming beams based on a difference in light quantity with respect to the surroundings in the image data coming from the camera  26 . Sequentially, a straight line Xa is created to come in contact with the uppermost end of the extracted images of the aiming beams (which is an upper end of the image  50   a  of the aiming beam in the present embodiment) and to be parallel with an X-axis, and another straight line Xb is created to come in contact with the lowermost end of the images (which is an lower end of the image  50   b  in the present embodiment) and to be parallel with the X-axis, as shown in  FIG. 5A . Similarly, a straight line Ya is created to come in contact with the leftmost end of the images (which is a left end of either one of the images  50   a  and  50   b ) and to be parallel with a Y-axis, and another straight line Yb is created to come in contact with the rightmost end of the images (which is a right end of either one of the images  50   a  and  50   b ) and to be parallel with the Y-axis. 
     The straight lines Xa, Xb, Ya, and Yb created as above define a rectangle region  51 . This region  51  changes in area depending on an overlapping condition of the two images of the aiming beams, namely, a coincident state of those images. To be more specific, when the images  50   a  and  50   b  come close to each other to overlap (coincide with) each other as shown in  FIG. 5B  from the state in  FIG. 5A , the area of the region  51  is reduced. When the region  51  is reduced to the minimum area where the images  50   a  and  50   b  of the aiming beams are completely overlapped each other on the treatment area as shown in  FIG. 5C , the image processing section  31  determines that sighting to the treatment area is completed, namely, that the sighting point is proper. 
     Operation of the laser treatment apparatus having the above configuration will be explained below. 
     At first, using the control panel  3 , an operator sets laser irradiation conditions such as the power of the treatment beam and others. The controller  30  then causes the display  5  to display the set laser irradiation conditions as setting information  53  in a lower part on the display  5  (see  FIG. 6 ). With the laser irradiation conditions displayed on the display  5 , the operator can confirm the laser irradiation conditions without the need of directly viewing the main unit  1  side (the control panel  3 ). 
     The operator may place the display  5  in an easy-to-see place in consideration of treatment using the contact lens  24 . By the operation of the joystick  4 , the operator moves the main unit  1  until the image of the eye E appears on the display  5 . 
     As shown in  FIG. 6A , on the display  5  the two images of the aiming beams reflected by the treatment area come to appear. The operator further operates the joystick  4  to slightly move the main unit  1  so that the images  50   a  and  50   b  of the aiming beams overlap each other. The image processing section  31  detects the overlapping condition (the coincident state) of the images  50   a  and  50   b  by the image processing at all times to transmit the image information (data) to the controller  30 . 
     Simultaneously the potentiometer  9  transmits the movement information (data) on the movement of the main unit  1  to the controller  30 . The controller  30  causes the display  5  to display the information (data) on the coincident state of the aiming beams with respect to the treatment area based on the image information (data) coming from the image processing section  31  and the movement information (data) coming from the potentiometer  9  respectively. 
     For example, when the coincident point of the aiming beams is at an operator&#39;s side (in the direction B), the main unit  1  should be moved forward (in the direction F), whereby the region  51  shown in  FIG. 5A  is reduced in area. The controller  30  can find the deviation direction of the coincident point of the aiming beams (i.e., the focus point of the treatment beam) with respect to a proper sighting point based on the information (data) on the moving direction of the main unit  1  from the potentiometer  9  and the information (data) on the changes in area of the region  51  (which is the information on the overlapping condition of the images of the aiming beams). When the deviation direction of the coincident point is at the operator&#39;s side with respect to the proper sighting point, the controller  30  causes the display  5  to display an “ant” sign representing that effect and an arrow mark  55  indicating the direction in which the main unit  1  should be moved. The operator, viewing the displayed information, operates the joystick  4  to move the main unit  1  forward. In further sighting, the images  50   a  and  50   b  of the aiming beams come to overlap each other on the treatment area, resulting in difficulty in recognizing them with the naked eye of the operator. However, the operator can perform the sighting based on the information displayed on the display  5 . 
     When the image processing section  31  detects that the images  50   a  and  50   b  of the aiming beams are overlapped each other into one image (or enter in a predetermined acceptable range), the controller  30  causes the display  5  to display an “OK” sign and a mark  56  indicating that the sighting is the most proper. When that sign appears on the display  5 , the operator stops the sighting and depresses the trigger switch  4   a  to start irradiation of the treatment beam to the treatment area. 
     In the above manner, the sighting can be executed based on the information (data) produced by the image processing, so that the operator can properly perform the sighting even if the coincident state of the aiming beams is difficult for the operator to recognize. 
     In the present embodiment, the control panel  3  is used to set the laser irradiation conditions, but it is not limited thereto. The display  5  may be configured in a touch panel type so as to allow the operator to set the laser irradiation condition with a touch of the screen of the display  5 . 
     The deviation direction of the coincident point of the aiming beams (the focus point of the treatment beam) can also be found in the following manner. As shown in  FIG. 7 , a shutter  27  is provided to alternately open the openings  20   a  and  20   b  of the aperture  20 . Under control of the controller  30 , the shutter  27  is driven to alternately allow irradiation of the two aiming beams. Based on the information (data) on the images  50   a  and  50   b  of the aiming beams by the image processing and the information (data) on opening/closing of the shutter  27 , the controller  30  determines the deviation direction of the coincident point of the aiming beams and the propriety as to whether the sighting is proper. To be more specific, when the coincident point is deviated to the operator&#39;s side (in the direction B), the opening  20   a  is opened to allow irradiation of the aiming beam, whereby the image  50   a  shown in  FIG. 5A  is detected. When the opening  20   b  is opened, the image  50   b  is detected. On the other hand, when the coincident point is deviated to the rear side (in the direction F), the detected image is opposite to above. Thus, the deviation direction in relation to the coincident point can be found; the operator&#39;s side or the rear side. Alternatively, the propriety of the sighting can be determined according to whether the distance between the centers of the images  50   a  and  50   b  of the aiming beams is within a predetermined acceptable range. 
     Utilizing the above information, the sighting also can be executed automatically (see  FIGS. 5 and 8 ). Upon depression of an automatic sighting switch not shown of the control panel  3  (S 1 ), the controller  30  drives a lens driving section not shown consisted of motors and cams to move the lens  23  by a predetermined amount in a predetermined direction (which may be either direction of the optical axis) (S 2 ). If the region  51  is reduced in area in association of the movement of the lens  23  in the predetermined direction (S 3 : YES), the lens  23  is further moved in the same direction as the predetermined direction (S 4 ). When the area of the region  51  comes to increase past the minimum (S 6 : YES), the lens  23  is moved in the reverse direction to reduce the area of the region  51 . The lens  23  is then stopped when the region  51  is reduced to the minimum area (S 7 ). If NO in S 6 , on the other hand, the lens  23  is further moved in the same direction as in S 4  (S 8 ). 
     If the moving direction and the moving amount of the lens  23  are stored in the controller  30  in relation to the information (data) detected by the image processing, the lens  23  can be easily returned to the position where the area of the region  51  reaches the minimum. 
     On the other hand, if the region  51  is increased in area when the lens  23  is moved in the predetermined direction (S 3 : NO), the lens  23  is moved in the reverse direction to reduce the area of the region  51  (S 5 ). Then, when the area of the region  51  comes to increase (S 6 : YES), the lens  23  is moved in the reverse direction to in S 5  and is stopped when the region  51  is reduced to the minimum area (S 7 ). If No in S 6 , the lens  23  is further moved in the same direction as in S 5  (S 8 ). 
     Upon stop of the lens  23  (completion of the sighting), the OK sign and the mark  56  are displayed on the display  5 . Viewing the displayed information, the operator stops the sighting and depresses the trigger switch  4   a  to start irradiation of the treatment beam to the treatment area. 
     In the case where the two aiming beams are alternately irradiated as shown in  FIG. 7 , similarly, the deviation direction of the coincident point of the aiming beams and the propriety of the sighting can be determined based on the information (data) on the images  50   a  and  50   b  of the aiming beams by the image processing and the information (data) on opening/closing of the shutter  27 , thus enabling the automatic sighting. 
     In the automatic sighting, the apparatus may be arranged to automatically irradiate the treatment beam after completion of the sighting, where the trigger switch  4   a  may be omitted. It may also be arranged to preclude laser irradiation until the sighting is completed by inserting the shutter  15  in the beam path. The same goes for the manual sighting mentioned above. 
     Although the automatic sighting is conducted by movement of the lens  23  in the optical axis direction in the above embodiment, the sighting may be conducted by automatic movement of the main unit  1  caused by means of a mechanism for electrically moving the main unit  1  forward and backward based on the information and others by the image processing. 
     To the contrary, the manual sighting may be executed by movement of the lens  23  by operation of a knob not shown instead of movement of the main unit  1  by operation of the joystick  4 . 
     It is needless to say that the automatic sighting is effective in a conventional laser treatment apparatus provided with a microscope. 
     Next, a second embodiment according to the present invention will be described.  FIG. 9  is a schematic perspective view of a laser treatment apparatus (Green-YAG laser photocoagulation apparatus) in the second embodiment. 
     Numeral  101  is a main unit of the laser treatment apparatus for emitting a treatment laser beam of continuous wave (which is hereinafter simply referred to as a treatment beam). The main unit  101  is internally provided with a treatment laser source, an aiming laser source, a light delivery optical system, and a controller, and others. Numeral  102  is a stand movable up and down. Numeral  104  is a joystick (and a rotating knob) used for moving the main unit  101  and is provided at its top with a trigger switch  104   a  for generating an instruction signal of emission of the treatment beam. Numeral  103  is a control panel used for setting laser irradiation conditions such as the power and the number of pulses of the treatment beam, the luminous intensity of a laser beam for aiming (which is hereinafter simply referred to as an aiming beam). 
     Numeral  105  is a slit-lamp delivery unit for irradiating the treatment beam to an affected part of a patient&#39;s eye E while allowing an operator to observe the affected part. The slit-lamp delivery unit  105  is essentially consisted of a laser irradiation section  105   a  internally provided with an irradiation optical system  140 , an illumination section  105   b  internally provided with an illumination optical system  125 , and a microscopic section  105   c  internally provided with an observation optical system  150 . Numeral  107  is a cable for transmitting the image information (data) from a CCD camera  126  included in the observation optical system  150  to the main unit  101 . 
     Numeral  109  is a foot switch serving as a trigger switch used for generating an instruction signal of emission of the treatment beam. 
       FIG. 10  is a schematic structural view of an optical system and a control system of the apparatus in the second embodiment. Numeral  110  is a laser source which is an Nd:YAG laser capable of oscillating a fundamental wavelength of 1064 nm. In the present embodiment, the laser source  110  generates a green treatment beam of 532 nm (linearly polarized light) which is double the fundamental wavelength. A part of the treatment beam emitted from the laser source  110  is reflected by a beam splitter  113  and, after passing through a diffusing plate  114   a , is detected by a power sensor  114   b.    
     Numeral  115  is a first safety shutter for intercepting the treatment beam. Numeral  117  is a dichroic mirror for reflecting the treatment beam to make it coaxial with the aiming beam (which is a red light of a dominant wavelength of 633 nm) from a semiconductor laser  118  serving as an aiming laser source. Numeral  119  is a collimator lens and numeral  120  is a second safety shutter which is inserted in the beam path while the aiming laser source  118  does not emit the aiming beam. When the shutter  120  is moved out of the beam path, the treatment beam and the aiming beam are allowed to pass without interception by the shutter  120  and are converged by a focusing lens  121  into an entrance  106   a  of an optical fiber  106 . 
     Numeral  140  is an irradiation optical system in the laser irradiation section  105   a . The treatment beam and the aiming beam delivered to the system  140  through the fiber  106  pass through a relay lens  122   a , a group of zoom lenses  122   b  movable in the optical path for changing a spot diameter of the beams, and an objective lens  123 . The beams are then reflected by a movable mirror  127  to irradiate the affected part of the eye E through a contact lens  124 . The objective lens  123  is structured of a fixed lens  123   a  and a movable lens  123   b . Moving the movable lens  123   b  in the optical axis direction executes a minute sighting. 
     Numeral  125  is a slit-light projecting optical system in the illumination section  105   b . The slit light from this system  125  illuminates the eye E through the contact lens  124 . 
     Numeral  150  is an observation optical system in the microscopic section  105   c . This microscopic section  105  is designed for binocular observation and provided with a pair of the observation optical systems  150 , though only one of the systems  150  is shown in  FIG. 10 . The observation optical system  150  includes an objective lens  151 , a group of variable magnification lenses  152 , a protective filter  153 , a group of erect prisms  154 , a field diaphragm  155 , and eyepieces  156 . A half mirror  157  is disposed between the erect prisms  154  and the field diaphragm  155  on either one of binocular observation optical paths. The light reflected by the half mirror  157  is received by a CCD camera  126 . 
     Numeral  130  is a controller for controlling the whole apparatus. Numeral  131  is an image processing section for processing the image of the aiming beam picked-up by the camera  126  to detect a forming state (a spot diameter) of the image. 
     It is to be noted that the lens  123   b  and the lens  151  are moved interlockingly on respective optical axes by means of corresponding lens driving sections  132  and  133 . 
     Next, explanation is made on a method for executing automatic sighting based on image processing, referring to a flowchart in  FIG. 11 . To focus the aiming beam on the same point as the treatment beam, the sighting is conducted such that the spot diameter of the aiming beam reflected at a desired point (the treatment area) is reduced to the minimum. 
     Upon depression of an automatic sighting switch not shown on the control panel  103  (S 11 ), the image processing section  131  extracts the image of the aiming beam based on a difference in light quantity with respect to the surroundings in the image data transmitted from the camera  126  to detect the spot diameter of the aiming beam. Subsequently, the controller  130  causes the lens driving sections  132  and  133  to move the lenses  123   b  and  151  in a predetermined direction (which may be either direction of each of the optical axes) by a predetermined amount whereby a change of the spot diameter can be recognized (S 12 ). The image processing section  131  detects the spot diameter which varies with the movement of the lenses  123   b  and  151  and transmits the information (data) on the spot diameter to the controller  130 . The controller  130  then compares the spot diameters between before and after the movement of the lenses  123   b  and  151 . If the spot diameter after the lens movement is smaller than that before the lens movement (S 13 : YES), the controller  130  further moves the lenses  123   b  and  151  in the same direction as above (S 14 ). If the spot diameter after the lens movement is larger (S 13 : NO), to the contrary, the controller  130  moves the lenses  123   b  and  151  in the reverse direction (S 15 ). 
     The image processing section  131  detects the spot diameter of the aiming beam continuously and transmits the information (data) thereon to the controller  130 . The controller  130  stops movements of the lenses  123   b  and  151  at the time when the spot diameter increases past the minimum value (S 16 : YES), and then moves the lenses  123   b  and  151  in the reverse direction to in S 14  (for S 13 : YES) or in S 15  (for S 13 : NO) to return them to the positions where the minimum value of the spot diameter is detected (S 17 ). If NO in S 16 , on the other hand, the lenses  123   b  and  151  are moved in the same direction as in S 14  (for S 13 : YES) or in S 15  (for S 13 : NO) (S 18 ). 
     If the moving direction and the moving amount of the lenses  123   b  and  151  are stored in relation to the information (data) of the image processing, the lenses  123   b  and  151  can be easily returned to the positions where the minimum spot diameter is detected. Using the above manner, the automatic sighting can be conducted. 
     In the above embodiment, the lenses  123   b  and  151  are moved interlockingly on respective optical axes. However, it is not so difficult for the operator to conduct sighting by manual operation while observing the affected part until the surroundings of the affected part is clearly observed. Accordingly, it is possible to move only the lens  123   b  without moving the lens  151 . 
     In the above embodiment, the automatic sighting is conducted by movement of the lenses  123   b  and  151  in the respective optical axis directions. An alternative design is to provide a mechanism for electrically move the main unit  101  forward and backward whereby to execute the sighting by automatically moving the main unit  101  based on the information (data) obtained by the image processing. 
     In the apparatus of the second embodiment, as well as in the first embodiment, it may be arranged such that manual sighting is conducted by displaying the information (data) on the display, instead of the automatic sighting. 
     The automatic sighting switch may be provided on the head of the joystick instead of the control panel. In this case, the foot switch may also be used as a trigger switch. Moreover, it may be provided a selection switch for selecting use/nonuse of the automatic sighting. 
     With the laser treatment apparatus in the above embodiments, the operator can easily observe the patient&#39;s eye in a comfortable position. The apparatus can ensure accuracy and easiness in sighting to focus the treatment laser beam to the desired point. 
     The foregoing description of the preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiment chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents.