Abstract:
An opthalmic apparatus includes an illumination optical system for illuminating an eye of a patient, the illumination optical system including a plurality of LEDs which are illumination light sources for emitting beams of light of wavelengths in different regions and a composing optical system for composing optical paths of the beams of light emitted from the LEDs, an observation optical system for observing the patient&#39;s eye, and a light quantity control section capable of controlling an illumination light quantity of each of the LEDs to produce substantially white illumination light.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an ophthalmic apparatus for performing observation or treatment by illuminating an eye of a patient.  
           [0003]    2. Description of Related Art  
           [0004]    As an ophthalmic apparatus for observing a patient&#39;s eye, there is known a slit lamp for projecting slit-shaped illumination light on the patient&#39;s eye, thereby allowing observation through an observation optical system, or a laser treatment apparatus constructed by a combination of the slit lamp and a laser irradiation device.  
           [0005]    These ophthalmic apparatus each cause an illumination light source provided inside of the apparatus to project illumination light on the patient&#39;s eye to thereby performing observation and treatment. A tungsten lamp, a halogen lamp or the like is generally used for the illumination light source.  
           [0006]    However, an illumination light source using a lamp is short in service life. Thus, such illumination light source requires frequent replacement, which is cumbersome and imposes burden on operators or the like. In addition, the lamp has a large heat rate during illumination, and may have a thermal effect on its periphery. It is therefore required to pay attention to a material or an installation position, etc. of the periphery of the illumination light source during design.  
           [0007]    The slip lamp is provided with a mechanism to insert/remove a wavelength selection filter for enabling fluorescent observation or the like into/from an illumination optical path. This may increase complexity in configuration of the apparatus.  
           [0008]    In many cases, a laser treatment apparatus for performing photocoagulation or the like is provided with a protective filter disposed in an observation optical path in order to protect an operator&#39;s eye from a laser beam for treatment reflected from the patient&#39;s eye or the like. However, in the case of observation through a protective filter for cutting a visible treatment laser beam, an observation image looks more colorful than that in the case where no protective filter is provided, has strangeness, and makes it difficult to ensure observation.  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention has been made in view of the above mentioned technical problems. It is an object of the present invention to provide an ophthalmic apparatus provided with an illumination light source which is easy-to-handle and arranged in simplified configuration.  
           [0010]    Another object of the present invention is providing an ophthalmic apparatus capable of facilitating observation even in the presence of a protective filter during laser treatment.  
           [0011]    In order to solve the foregoing problems, the present invention is characterized by comprising the following constituent elements.  
           [0012]    According to a first aspect of the present invention, there is provided an ophthalmic apparatus including: an illumination optical system for illuminating an eye of a patient, the illumination optical system including a plurality of LEDs which are illumination light sources for emitting beams of light of wavelengths in different regions and a composing optical system for composing optical paths of the beams of light emitted from the LEDs; an observation optical system for observing the patient&#39;s eye; and a light quantity control section capable of controlling an illumination light quantity of each of the LEDs to produce substantially white illumination light.  
           [0013]    According to another aspect of the present invention, there is provided an ophthalmic apparatus including: an illumination optical system for illuminating an eye of a patient, the illumination optical system including a plurality of LEDs which are illumination light sources for emitting beams of substantially white light and a composing optical system for composing optical paths of the beams of light emitted from the LEDS; an observation optical system for observing the patient&#39;s eye; and a light quantity control section for controlling the light emission quantity of each of the LEDs.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    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.  
         [0015]    In the drawings,  
         [0016]    [0016]FIG. 1 is an external view showing a laser treatment apparatus in an embodiment according to the present invention;  
         [0017]    [0017]FIG. 2 is a schematic view showing an optical system of the apparatus;  
         [0018]    [0018]FIG. 3 is a block diagram schematically showing a control system of the apparatus;  
         [0019]    [0019]FIG. 4 is a view showing wavelength characteristics of each LED;  
         [0020]    [0020]FIG. 5 is a view showing wavelength transmission characteristics of a protective filter; and  
         [0021]    [0021]FIG. 6 is a block diagram schematically showing a mechanism for selectively lighting LEDs.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0022]    A detailed description of a preferred embodiment of an ophthalmic apparatus embodying the present invention will now be given referring to the accompanying drawings. The present embodiment exemplifies a laser treatment apparatus as the ophthalmic apparatus according to the present invention. FIG. 1 is an external view showing a laser treatment apparatus for performing photocoagulation treatment by irradiating a laser light beam for treatment (hereinafter, merely referred to as a treatment beam) to the periphery an affected part of a patient&#39;s eye. FIG. 2 is a schematic view showing an opitical system of the apparatus.  
         [0023]    Reference numeral  1  denotes a main body of the laser treatment apparatus. Reference numeral  2  is a control board for setting and inputting irradiation output conditions of the treatment beam. Reference numeral  3  denotes a slit lamp delivery comprising a laser irradiation optical system  30 , an illumination optical system  40 , and an observation optical system  50 . Reference numeral  4  is a fiber cable for delivering the treatment beam or an aiming laser light beam (hereinafter, merely referred to as an aiming beam) from the main body  1  to the slit lamp delivery  3 . Reference numeral  5  is a foot switch for generating a trigger signal to start Laser irradiation. Reference numeral  6  is a joystick for moving the slit lamp delivery  3 .  
         [0024]    Reference numeral  7  denotes a switch for lighting LEDs  41   a - 41   c  that constitute an illumination light source incorporated in the slit lamp delivery  3 . Reference numeral  8  denotes a light adjusting knob for adjusting an illumination light quantity. Reference numeral  9  is a cable connecting between the slit lamp delivery  3  and a control section  60  (see FIG. 3) on the side of the main body  1 . The cable  9  is used for transmitting and receiving a command signal to insert/remove a protective filter  57  with respect to an optical path of the observation optical system  50  (hereinafter, referred to as an observation optical path) or a detection signal indicating the insertion or removal of the filter  57  (i.e. the presence or absence of the filter  57  in the observation optical path). The cable  9  is also used to transmit whether the toot switch  5  is active or inactive to the slit lamp delivery  3 .  
         [0025]    Reference numeral  10  denotes a laser source for emitting a treatment beam. In the present embodiment, as the laser source  10 , an Nd:YAG laser capable of oscillating a fundamental wave of 1064 nm is used to generate a green light of 532 nm (linearly polarized light), which is double the fundamental wave. Reference numeral  11  is a beam splitter having the property of transmitting most part of the treatment beam emitted from the laser source  10  while reflecting a part of the beam. The part of the treatment beam reflected by the beam splitter  11  enters an output sensor  13  through a diffusing plate  12  for detecting the output value of the treatment beam.  
         [0026]    Reference numeral  14  is a safety shutter. When the foot switch  5  is depressed, issuing a command for laser irradiation (i.e. generating a trigger signal), the safety shutter  14  is removed from the optical path, thus enabling the passing of the treatment beam. In case where an abnormality occurs, the safety shutter  14  is inserted into the optical path to thereby intercept the laser beam. The opening and closing of this shutter  14  is detected by means of a shutter sensor  14   a.    
         [0027]    Reference numeral  15  denotes a laser light source for emitting an aiming beam. In the present embodiment, there is used a semiconductor laser source capable of emitting a red aiming beam of 630 nm. The aiming beam emitted from the light source  15  passes through a collimator lens  16  and is made coaxial to the treatment beam by means of a dichroic mirror  17 .  
         [0028]    Reference numeral  18  is a second safety shutter. The opening and closing of this shutter  18  is detected by a shutter sensor  18   a . Reference numeral  19  denotes a focusing lens for focusing the laser beams (the treatment beam and the aiming beam) to an incident end face  4   a  to enter the fiber  4 . The laser beams are delivered through the fiber  4  to the irradiation optical system  30  of the slit lamp delivery  3 .  
         [0029]    The irradiation optical system  30  comprises a collimator lens  31 , a variable magnification lens group  32 , an objective lens  33 , and a driving mirror  34 . An operator can operate a manipulator (not shown), whereby to change the reflection angle of the driving mirror  34  to fine adjust a laser irradiation position.  
         [0030]    Reference numeral  40  denotes an illumination optical system. Reference numerals  41   a ,  41   b , and  41   c  each denote an LED used as an illumination light source. The LEDs  41   a - 41   c  emit beams of illumination light in wavelength regions for red (R), green (t), and blue (B), respectively, that are the primary colors of light.  
         [0031]    The wavelength characteristics of each of the LEDs  41   a ,  41   b , and  41   c  are shown in FIG. 4. The LED  41   a  emits illumination light of the blue wavelength region of which a peak light emission wavelength is close to 460 nm, and the blue illumination light is allowed to pass through dichroic mirrors  80  and  81  disposed on an optical axis L. The LED  41   b  emits illumination light of a green wavelength region of which a peak light emission wavelength is close to 520 nm. The green illumination light is reflected by the dichroic mirror  80  to be composed with the blue illumination light. Then, the resultant light is allowed to pass through the dichroic mirror  81 . The LED  41   c  emits illumination light of a red wavelength region of which a peak light emission wavelength is close to 630 nm. The red illumination light is reflected by the dichroic mirror  81  to be composed with the beams of blue and green illumination light.  
         [0032]    In the present embodiment, although the dichroic mirrors  80  and  81  are used to make the beams of illumination light (red, green, and blue light beams) coaxial to each other (composed with each other), the present invention is not limited to such dichroic mirror. A beam combining device such as half mirror, polarizing plate, or prism may be used.  
         [0033]    The beams of visible illumination light emitted from the LEDs  41   a - 41   c  and made coaxial (composed with each other) on the optical axis L are allowed to pass through a condenser lens  42 . A height and a width of the resultant light are determined by a variable circular aperture plate  43  and a variable slit plate  44  respectively to be formed into a slit-shaped luminous flux. Then, the slit-shaped illumination light is allowed to pass through a projection lens  46  and then reflected by dividing mirrors  48   a  and  48   b  toward the patient&#39;s eye E. The light thus illuminates the eye E through a contact lens  49 . Reference numeral  47  is a correction lens, and reference numeral  45  is a wavelength selection filter to be inserted into or removed from the optical path of the illumination optical system  40  (hereinafter, referred to as illumination optical path).  
         [0034]    An observation optical system  50  comprises: an objective lens  51  shared between the left and right observation optical paths; a variable magnification lens  52 ; an image forming lens  53 ; an erect prism  54 ; a field diaphragm  55 ; eyepiece lenses  56 ; and the protective filter  57 ; the elements  53 - 57  being disposed in the left and right observation optical paths, respectively. FIG.  5  is a view showing wavelength transmission characteristics of the filter  57 . The filter  57  used in the present embodiment has the property of cutting 99% or more of light of a narrow bandwidth wavelength region (520 nm-540 nm), the center of which is 532 nm of the treatment beam, while allowing most of light of the visible wavelength region.  
         [0035]    The filter  57  is arranged to be insertable into or removable from the observation optical path by means of a movement mechanism constructed of a motor or the like (not shown). The insertion and removal of the filter  57  with respect to the observation optical path is effected based on the presence or absence of the trigger signal from the foot switch  5 . The condition of the filter  57 , or the presence or absence of the filter  57  in the observation optical path, is detected by means of a sensor  57   a.    
         [0036]    Operation of the apparatus constructed as above will be described with reference to a block diagram schematically showing a control system shown in FIG. 3.  
         [0037]    An operator turns on the LEDs  41   a - 41   c  by means of the switch  7 . At this time, the light quantity of each of the illumination light beams emitted from the LEDs  41   a - 41   c  is controlled in advance by a light quantity control section  61  so that white illumination light is produced after three luminous fluxes (red, green, and blue) have been composed. To be more specific, the light quantities of the LEDs  41   a ,  41   b , and  41   c  are each controlled so that the light quantities have the following ratio; LED  41   a : LED  41   b : LED  41   c  (B:G:R)=0.5:0.6:1.0.  
         [0038]    As a result, the illumination light beams emitted from the LEDs  41   a - 41   c  are changed into a substantially white illumination light after they are composed; the white illumination light illuminates the patient&#39;s eye E; and the operator can obtain an observation image (observation visual field) in close to a natural color. It in to be noted that the light quantity ratio is not limited to the above, another ratio may be adopted if only the color of the illumination light produced by composition is within a region of white light.  
         [0039]    Even when the light quantity of illumination light projected to the patient&#39;s eye E is changed by using the light adjusting knob  8 , the light quantity is increased or decreased by the light quantity control section  61  without changing the ratio of the light emission quantities of the LEDs  41   a - 41   c . This makes it possible to maintain the illumination light after composed in a substantially white color.  
         [0040]    Since the LED is used as the illumination light source in the present embodiment, heating quantity can be reduced, thus eliminating the need to consider a thermal effect caused by the illumination light from the LED. Such each LED has its long service life, and may not be frequently replaced.  
         [0041]    The illumination light beams from the LEDs  41   a ,  41   b , and  41   c  are composed by the dichroic mirrors  80  and  81 , whereby substantially white illumination light is produced as described above, which illuminates the patient&#39;s eye E through the illumination optical system  40 . The operator can observe through the observation optical system  50  the fundus of the patient&#39;s eye E illuminated by the white illumination light.  
         [0042]    Next, the aiming laser source  15  is lit by a switch (not shown) on the control board  2 . Upon setting of the emission of the aiming beam, the control section  60  causes the shutter  18  to be removed from the optical path.  
         [0043]    The operator operates the joystick  6  and a manipulator (not shown) while observing the aiming beam irradiated to the eye fundus, and performs alignment with respect to an affected part of the eye fundus. The operator sets irradiation conditions such as the irradiation power or irradiation time of the treatment beam by using various switches on the control board  2 . When the laser irradiation is ready, a READY status is established such that the irradiation of the treatment beam is enabled. Then, the operator operates the manipulator (not shown) to make fine adjustment for alignment with the affected part. After completion of the alignment, the operator depresses the foot switch  5  to start the laser irradiation. Upon receipt of the trigger signal from the foot switch  5 , the control section  60  generates a command signal to insert the filter  57  into the observation optical path. The sensor  57   a  detects that the filter  57  is inserted into the observation optical path and transmits the detection signal to the light quantity control section  61 .  
         [0044]    Upon receipt of the detection signal from the sensor  57   a , the light quantity control section  61  changes the ratio of the light quantities of the LEDs  41   a - 41   c  in synchronization with the insertion of the filter  57  into the observation optical path. A change quantity of this light quantity ratio is preset so that the light densities of R, G, and B that pass through the filter  57  are close to those obtained in the absence of the filter  57  in the observation optical path.  
         [0045]    The above change of the light quantity ratio by the light quantity control section  61  is effected for the following reason.  
         [0046]    That is, when the reflection light from the patient&#39;s eye E passes through the filter  57 , light of wavelengths in a range of 520 nm to 540 nm is cut by the filter  57  in order to cut the treatment beam. In association with this, the density of the green light is reduced. In this case, the ratio of the light quantities of the light beams passed through the filter  57  becomes the following relation; B:G:R=0.8:0.3:1.0. Consequently, the entire observation image obtained during observation through the filter  57  is more colorful (purplish) than that obtained in the absence of the filter  57 .  
         [0047]    To compensate for the density of the green light cut by the filter  57 , the density of light of a green wavelength region which is allowed to pass through the filter  57  is relatively increased.  
         [0048]    The ratio of respective light quantities of the LEDs  41   a - 41   c  is changed, for example, by increasing the light quantity of LSD  41   b , while decreasing those of the LEDs  41   a  and  41   c , so that the light quantity ratio of the light beams passed through the filter  57  is adjusted to the relation; B:G:R=0.5:0.6:1.0. In this case, the ratio of respective actual light quantities of the LEDs shows the following relation; LED  41   a : LED  41   b  LED  41   c  (B:G:R)= 0.3:1.0:0.9. In this manner, the colored degree of an observation image is lowered, and an observation image produced in the presence of the filter  57  in the observation optical path can be given the tone close to the observation image produced in the absence of the filter  57  therein.  
         [0049]    Relative control of the light quantity ratio of the LEDs  41   a - 41   c  may be experimentally determined so that the tones of the observation images in the presence and the absence of the filter  57  are as identical to each other as possible.  
         [0050]    When confirmed the insertion of the filter  57  into the observation optical path through the sensor  57   a  (when received the detection signal representative of the presence of the filter  57  from the sensor  57   a ), the control section  60  causes the shutter  14  to be removed from the optical path and the laser source  10  to emit the treatment beam. The treatment beam is delivered through the optical system in the main body  1 , the fiber  4 , and the irradiation optical system  30 , to irradiate the affected part of the patient&#39;s eye E.  
         [0051]    Even if the filter  57  is inserted during laser irradiation, i.e., in the observation optical path, the observation image is obtained in a color state close to a natural color which is obtained during the observation in the absence of the filter  57 . Thus, the state of the affected part or treatment result can be observed without any strangeness. Further, even when the filter  57  is placed in the observation optical path for a long time for continuous laser irradiation, there is no need to remove the filter  57  in the middle of treatment because of a low visibility in order to allow the operator to check the treatment state without the filter  57 . The light quantity control mentioned above is therefore particularly effective for the continuous laser irradiation.  
         [0052]    When the operator stops depressing the foot switch  5 , no trigger signal is generated therefrom. In response to no signal from the foot switch  5 , the control section  60  stops the laser emission from the laser source  10  and removes the filter  57  from the observation optical path. In association with the detection signal from the sensor  57   a  that has detected the removal of the filter  57 , the light quantity control section  61  resets the light quantity ratio of the LEDs  41   a - 41   c  to the original light quantity ratio used before the insertion of the filter  57 . In this manner, even after the filter  57  is removed from the observation optical path, there can be obtained an observation image with substantially the same tone as that obtained before the insertion of the filter  57  into the observation optical path.  
         [0053]    The present invention may be embodied in other specific forms without departing from the essential characteristics thereof.  
         [0054]    For instance, in the above embodiment, the light quantity ratio of the LEDs  4 l a - 41   c  is changed in association with the detection signal from the sensor  57   a  representing the presence/absence of the filter  57  in the observation optical path. Alternatively, the ratio may be changed in response to the trigger signal from the foot switch  5 .  
         [0055]    The above embodiment has described an example of using three types of LEDs for emitting beams of illumination light of wavelengths in regions for R, G, and B. However, if those three types of LEDs are insufficient to produce a substantially white illumination light, the types of LEDs for emitting beams of illumination light of wavelengths in different regions from the above three regions may be further increased so that the substantially white illumination light is easily obtained. In the case where the illumination light quantity is insufficient, the number of LEDs may be increased for each color.  
         [0056]    Furthermore, although the present embodiment describes an example of a laser treatment apparatus, the present invention is, of course, applicable to only a slit lamp. In this case, there is conveniently provided selection keys  70   a ,  70   b , and  70   c  for selectively lighting the LEDs  41   a ,  41   b , and  41   c  for B, G, and R light or individually adjusting the light quantity of each of the  41   a - 41   c  (see FIG. 6). For example, in the fluorescent observation using fluorescein eyewash, the LED  41   a  is lit so that the patient&#39;s eye E is illuminated by blue illumination light capable of exciting fluorescein.  
         [0057]    In the observation of blood vessels of conjunctiva or the like, the LED  41   b  for emitting green illumination light is lit without illumination by red illumination light, thereby facilitating the observation. This makes it also possible to eliminate a filter mechanism for selecting wavelengths from the illumination optical system  40 . In such a case, an LED for emitting light of wavelengths required for the fluorescence observation or the like may be provided in advance as an LED for an illumination light source.  
         [0058]    Alternatively, the light quantity of red illumination light may be reduced or the light quantity of green illumination light or blue illumination light may be increased in order to finely adjust the illumination light to an easy-to-observe color according to the color of an observation site.  
         [0059]    The lighting of the LEDs  41   a - 41   c  or the light quantity control is effected by the light quantity control section  61  connected to the selection keys  70   a - 70   c . In the case where the entire illumination light quantity is controlled without changing the light quantity ratio of the colors, the knob  8  is used. Alternatively, an LED for emitting illumination light of wavelengths according to types of the fluorescence observation or the like may be provided separately from the LED for an illumination light source.  
         [0060]    Furthermore, even if only one type of a white-emitting LED is used without use of three types (R, G, and B) of LEDs, the use of such white-emitting LED is very effective in heat generation and service life in comparison with a conventional halogen lamp or tungsten lamp.  
         [0061]    As has been described above, according to the present invention, the apparatus with an illumination light source which is easy-to-handle and a simplified configuration can be achieved. Furthermore, in the laser treatment, the affected part of the patient&#39;s eye can be easily observed even in the presence of the protective filter in the optical path of the observation optical system.