Abstract:
A laser treatment apparatus for performing treatment by irradiating an affected part with a laser beam, the apparatus including: a laser source ( 9 ) which emits a laser beam having a wavelength in a visible wavelength region; a polarization splitting member ( 11 ) which splits the laser beam emitted from the laser source into a P-polarized component and an S-polarized component; and a polarization combining member ( 16 ) which combines optical axes of the split components in a predetermined positional relation.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a laser treatment apparatus or performing treatment by irradiating an affected part with a laser beam.  
           [0003]    2. Description of Related Art  
           [0004]    There is a laser treatment apparatus which is used for treatment with a treatment laser beam (hereinafter, “a treatment beam”) to irradiate an affected part of the fundus of a patient&#39;s eye and others. In this type of apparatus, an aiming beam of a different wavelength (color) from the treatment beam is generally used. However, the use of the aiming beam of substantially the same wavelength (color) as the treatment beam is more convenient because the transmittance property of the treatment beam can be observed and confirmed by the use of the aiming beam. For instance, if an intermediate optic media such as a crystalline lens and a vitreous body is clouded, the transmittance property of the treatment beam largely differs depending on wavelengths (colors) of the treatment beam.  
         SUMMARY OF THE INVENTION  
         [0005]    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 capable of easily and efficiently producing an aiming beam of the same wavelength (color) as that of a treatment laser beam.  
           [0006]    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.  
           [0007]    To achieve the purpose of the invention, there is provided a laser treatment apparatus for performing treatment by irradiating an affected part with a laser beam, the apparatus including: a laser source which emits a laser beam having a wavelength in a visible wavelength region; a polarization splitting member which splits the laser beam emitted from the laser source into a P-polarized component and an S-polarized component; and a polarization combining member which combines optical axes of the split components in a predetermined positional relation.  
           [0008]    According to another aspect of the present invention, there is provided a laser treatment apparatus for performing treatment by irradiating an affected part with a laser beam, the apparatus including: a laser source which emits a laser beam having a wavelength in a visible wavelength region; a polarization splitting member disposed on an optical axis of the laser beam, for splitting the laser beam emitted from the laser source into a first polarized component to be used for treatment and a second polarized component to be used for aiming, the first polarized component being larger in a polarization ratio than the second polarized component; and a polarization combining member disposed on optical axes of the split components, for combining the optical axes of the split components in a predetermined positional relation. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    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.  
         [0010]    In the drawings,  
         [0011]    [0011]FIG. 1 is a perspective external view of a laser treatment apparatus in an embodiment according to the present invention;  
         [0012]    [0012]FIG. 2 is a schematic view showing an optical system provided in the interior of the apparatus;  
         [0013]    [0013]FIG. 3 is a block diagram showing a control system of the apparatus;  
         [0014]    [0014]FIG. 4 is a schematic view showing a modification example of the optical system of the apparatus; and  
         [0015]    [0015]FIG. 5 is a schematic view showing another modification example of the optical system of the apparatus. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    A detailed description of a preferred embodiment of a laser treatment apparatus embodying the present invention will now be given referring to the accompanying drawings.  
         [0017]    [0017]FIG. 1 is a perspective external view of a laser photocoagulation apparatus in the present embodiment. Numeral  1  is a main unit of the apparatus in which a laser source and an optical system for allowing a laser beam to be incident on an optical fiber  2 . Numeral  3  is a control box for setting and displaying photocoagulation conditions (laser irradiation conditions) such as laser output power, an irradiation duration and a wavelength of the laser beam, and displaying the status of the apparatus. Numeral  4  is a slit lamp delivery for irradiating the laser beam to an affected part of a patient&#39;s eye while allowing an operator to observe the patient&#39;s eye. This slit lamp delivery  4  is provided with a laser irradiating part  5  for irradiating the laser beam delivered through the optical fiber  2 , an illuminating part  6  for illuminating the patient&#39;s eye, and a binocular microscope  4  for observation of the patient&#39;s eye. Numeral  7  is a footswitch for generating a trigger signal for laser irradiation.  
         [0018]    [0018]FIG. 2 is a schematic view explaining an optical system provided in the interior of the main unit  1  of the apparatus. FIG. 3 is a block diagram of a control system of the apparatus. Numeral  9  is a laser source, which is internally provided with an Nd:YAG crystal serving as a solid laser medium, a diode laser serving as an exciting light source, and a nonlinear crystal serving as a wavelength converter. The Nd:YAG crystal emits light beams having a plurality of different oscillation lines (peak wavelengths) in a near-infrared region by excitation light from the diode laser. The nonlinear crystal is used to generate the second harmonic waves of three oscillation lines of about 1064 nm, about 1123 nm, and about 1319 nm, which are higher in output power among the plurality of oscillation lines, thus emitting laser beams of three colors having wavelengths in a visible region, namely, about 532 nm (green), about 561 nm (yellow), and about 659 nm (red).  
         [0019]    Numeral  10  is a safety shutter, which is removed from an optical path by driving of a driving device  61  to allow the laser beam to travel along the optical path and, alternatively, which is inserted in the optical path in a predetermined case for example of occurrence of an abnormal event to intercept the laser beam. The opening and closing of this safety shutter  10  is detected by a shutter sensor  10   a.    
         [0020]    Numeral  11  is a polarizer, e.g., a polarization beam splitter, which splits the laser beam from the laser source  9  into a P-polarized component and an S-polarized component. In many cases, the laser sources to be used for treatment emit linearly polarized light having a P-to-S polarization ratio of about 1000 to 1. Thus, an S-polarized component of about 1/1000 can be taken out, so that a quantity of light needed for the aiming beam can be divided with a low loss.  
         [0021]    The P-polarized component utilized as a treatment laser beam (hereinafter, “a treatment beam”) passes through the polarizer  11  and succeedingly travels along an optical axis L 1 . On this optical axis L 1 , a shutter  17  for the treatment beam is disposed. This shutter  17  is inserted in the optical path by driving of a driving device  67  to intercept the treatment beam when the treatment beam is not required. The opening and closing of the shutter  17  is detected by a shutter sensor  17   a.    
         [0022]    The S-polarized component utilized as the aiming beam is reflected by the polarizer  11  and a mirror  12  in sequence and then travels along an optical axis L 2 . On this optical axis L 2 , there is disposed a compensating lens  13  for compensating a difference in optical length between the optical axes L 1  and L 2 . Preferably, a shutter  14  for the aiming beam is also provided on the optical axis L 2 . When the aiming beam is not required, the shutter  14  is inserted in the optical path by driving of a driving device  64  to intercept the aiming beam. The opening and closing of the shutter  14  is detected by a shutter sensor  14   a.  The S-polarized component having passed through the shutter  14  is reflected by a mirror  15  toward a polarizer  16  which combines the P-polarized beam and the S-polarized beam again into a coaxial beam.  
         [0023]    The polarizer  16  allows the P-polarized beam traveling along the optical axis L 1  to pass through, while reflects the S-polarized beam traveling along the optical axis L 2 , thereby producing a combined laser beam. Numeral  22  is a light condensing lens, which converges the laser beam on an incident end of the optical fiber  2  and allows the laser beam to be incident thereon. The laser beam delivered into the slit lamp delivery  4  through the optical fiber  2  is irradiated by the laser irradiating part  5  to an affected part of a patient&#39;s eye.  
         [0024]    In FIG. 3, numeral  60  is a control part, to which the laser source  9 , the footswitch  7 , the control box  3 , each sensor, each driving device, and others are connected. In the control box  3 , there are provided a rotary knob  3   a  for setting laser output power of the treatment beam, a switch  3   b  for setting a light quantity of the aiming beam, a color switch  3   c  for selecting (setting) a wavelength (color) of the treatment beam and the aiming beam, and a switch  3   d  for switching an operating mode of the apparatus between a laser irradiation enabled state (a READY mode) and a laser irradiation disabled state (a STANDBY mode). In addition, the control box  3  is provided with switches for setting photocoagulation conditions for example a duration of laser irradiation and a time interval of laser irradiation, and a display part, which are not shown in FIG. 3. The shutter  17  for the treatment beam is opened for the set irradiation duration when the footswitch  7  is depressed. The shutter  14  for the aiming beam is opened when the switch  3   b  is turned on (where the aiming beam is not zero).  
         [0025]    The operation of the apparatus having the above structure is explained below.  
         [0026]    For laser irradiation, the operator operates each switch on the control box  3  to set in advance photocoagulation conditions for example selection of a wavelength of the treatment beam and the aiming beam, laser output power, an irradiation duration. The selection of a wavelength of the treatment beam and the aiming beam is made by use of the color switch  3   c  to select a wavelength (red, yellow, green) adequate for a treatment purpose. In the present embodiment, the explanation is made assuming that the yellow laser beam is selected. After the selection of the wavelength, the laser beam of a selected wavelength is emitted from the laser source  9 . The operator presses the switch  3   d  to change the operating mode of the apparatus from the STANDBY mode to the READY mode, thereby opening the safety. shutter  10 . When the switch  3   b  is turned on, furthermore, the shutter  14  is opened by the driving device  64 , which allows only the S-polarized beam utilized as the aiming beam split by the polarizer  11  to travel through the optical fiber  2  and be delivered to the laser irradiating part  5  of the slit lamp delivery  4 . Thus, the aiming beam is irradiated to the eye fundus.  
         [0027]    The operator observes the fundus of the patient&#39;s eye and the aiming beam through the slit lamp delivery  4  to make alignment of the aiming beam with respect to the affected part. Succeedingly, when the operator depresses the footswitch  7 , the shutter  17  is opened. This allows the P-polarzed beam utilized as the treatment beam to pass through the polarizer  16  and be combined with the S-polarized beam utilized as the aiming beam, and then the combined laser beam is delivered to the laser irradiating part  5  through the optical fiber  2 . Thus, the treatment beam and the aiming beam are irradiated to the eye fundus. The control part  60  controls the output power of the laser source  9  so that the laser output power of the treatment beam and the quantity of the aiming beam are adjusted to the settings determined by the use of the rotary knob  3   a  and the switch  3   b  on the control box  3 , respectively.  
         [0028]    In the above apparatus, the aiming beam of the same color (wavelength) as that of the treatment beam is used for alignment, which enables observation of the transmittance property of the actual treatment beam. The yellow laser beam is selected in the above explanation; however, if the transmittance property become largely different depending on laser wavelengths, the operator selects an appropriate laser beam from among green, yellow, and red laser beams by observing each transmittance property.  
         [0029]    [0029]FIG. 4 is a schematic view showing a modification example of the optical system of the apparatus. In some cases, the solid laser such as an Nd:YAG laser may provide more satisfactory stability when the laser is operated at a fixed output power. In this case, as the modification example shown in FIG. 4, a ½ wave plate  32  is disposed on the optical axis L 1  and another ½ wave plate  31  is disposed on the optical axis L 2 , so that respective light quantities (powers) of the treatment beam and the aiming beam can be controlled. In FIG. 4, like elements corresponding to those of the optical system shown in FIG. 2 are indicated by like numerals.  
         [0030]    When the ½ wave plates  31  and  32  are rotated, a polarization plane of each beam which passes through each plate is rotated. Accordingly, a polarization ratio (P/S) in each beam can be freely changed. The polarizer  16  combines only the P-polarized beam passed through the ½ wave plate  32  and the S-polarized beam passed through the ½ wave plate  31  and directs the combined laser beam into the optical fiber  2 . More specifically, the polarizer  16  not only serves to combine the P-polarized beam for treatment and the S-polarized beam for aiming but also serves as an attenuator in combination with the ½ wave plates  31  and  32  to control each light quantity. It is to be noted that the S-polarized beam passed through the ½ wave plate  32  is reflected by the polarizer  16  and the P-polarized beam passed through the ½ wave plate  31  is allowed to pass through the polarizer  16 , and both the polarized beams come into a diffuser  33 . That is, the diffuser  33  serves to absorb the laser beam no longer required in order to reduce outputs of the treatment beam and the aiming beam.  
         [0031]    The laser output power of the treatment beam is set with the rotary knob  3   a  and the light quantity of the aiming beam is set with the switch  3   b.  The ½ wave plate  32  is rotated by a driving part  32   a  and the ½ wave plate  31  is rotated by a driving part  31   a.    
         [0032]    [0032]FIG. 5 is a schematic view showing another modification example of the optical system shown in FIG. 4. This optical system is arranged such that the mirror  15  and the polarizer  16  in the optical system of FIG. 4 are interchanged to provide the optical paths of equal length between the polarizers  11  and  16 . The optical paths of equal length can eliminate the need of the compensating lens  13  disposed on the optical axis L 2 .  
         [0033]    In the above embodiment, a polarizing filter may be provided instead of the ½ wave plate  31  disposed on the optical axis L 2 . In this case, the polarizing filter is driven to rotate, thereby attenuating the light quantity of the aiming beam to control the light quantity. Instead of the ½ wave plate  31 , alternatively, a variable density filter which continuously varies optical density clockwise may be provided. In this case, the variable density filter is driven to rotate, thereby attenuating the light quantity of the aiming beam to control the light quantity.  
         [0034]    Furthermore, a brewster plate may be used as the polarizer. This brewster plate has an advantage of causing little loss with respect to linearly polarized light.  
         [0035]    The polarization ratio of the S-polarized beam for aiming to the P-polarized beam for treatment which are split by the polarizer  11  has only to be in just about the same range as an attenuation ratio of an attenuation filter conventionally used, so that the above structure can be used effectively.  
         [0036]    Although the S-polarized beam is utilized as the aiming beam in the above embodiment, instead thereof, the P-polarized beam may be utilized as the aiming beam if the P-polarized beam becomes lower in value of the polarization ratio than the S-polarized beam in association with the linear polarization of the laser beam from the laser source and the placement of the polarizer  11 .  
         [0037]    As described above, according to the present invention, an aiming beam of the same wavelength (color) as the treatment laser beam can be obtained with a low loss by a simple manner. In addition, the mechanism for controlling output power of the treatment laser beam and the aiming beam can economically be structured.  
         [0038]    While the presently preferred embodiment of the present invention has been shown and described, it is to be understood that this disclosure is for the purpose of illustration and that various changes and modifications may be made without departing from the scope of the invention as set forth in the appended claims.