Patent Abstract:
For improving the operability of the apparatus, the ophthalmologic apparatus of the invention comprises a measuring optical system which optically measures an eye to be examined, a detection system which detects alignment information of the eye for the measurement, a driving mechanism which moves the measuring optical system relative to the eye, an operating device which allows an operator to manually control the driving mechanism in order to move the measuring optical system, and a controller which controls the driving mechanism to perform alignment of the measuring optical system with respect to the eye, with a plurality of modes including a first mode executing automatic alignment within a predetermined range based on the alignment information of the detection system and a second mode executing manual alignment within a range broader than the predetermined range based on the operation of the operation device, wherein the controller automatically changes between the first mode and the second mode based on a predetermined event.

Full Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to an ophthalmologic apparatus such as an autorefractometer used for the measurement of an eye to be examined in a hospital or an optician&#39;s store.  
           [0003]    2. Related Background Art  
           [0004]    There are known an ophthalmologic apparatus for effecting auto-alignment after manual alignment, and an ophthalmologic apparatus which can select manual alignment and auto-alignment. However, in the ophthalmologic apparatus for effecting auto-alignment after manual alignment, when alignment becomes impossible due to some cause or other after auto-alignment has been started, alignment must be manually effected again from the first. Also, after auto-alignment has been started, if alignment is manually effected without noticing it, measurement will sometimes become impossible. Also, in the ophthalmologic apparatus capable of effecting both of manual alignment and auto-alignment, the changeover between the manual operation and the automatic operation is cumbersome, and an improvement in operability is required.  
         SUMMARY OF THE INVENTION  
         [0005]    The present invention aims at improvements in the ophthalmologic apparatuses according to the prior art and a primary object thereof is to provide an ophthalmologic apparatus excellent in operability. Another object of the present invention is to provide an ophthalmologic apparatus in which smooth shift is possible between manual alignment and auto-alignment. Still another object of the present invention is to provide an ophthalmologic apparatus which quickly and reliably makes alignment and measurement possible. Yet still another object of the present invention is to provide an ophthalmologic apparatus provided with an optical element with a prism which makes alignment possible by a simple construction.  
           [0006]    The ophthalmologic apparatus according to the present invention for achieving the above objects is an ophthalmologic apparatus comprising a measuring optical system which optically measures an eye to be examined, a detection system which detects alignment information of the eye for the measurement, a driving mechanism which moves the measuring optical system relative to the eye, an operating device which allows an operator to manually control the driving mechanism in order to move the measuring optical system, and a controller which controls the driving mechanism to perform alignment of the measuring optical system with respect to the eye, with a plurality of modes including a first mode executing automatic alignment within a predetermined range based on the alignment information of the detection system and a second mode executing manual alignment within a range broader than the predetermined range based on the operation of the operation device, wherein the controller automatically changes between the first mode and the second mode based on a predetermined event.  
           [0007]    Further objects and forms of the present invention will become apparent from the following description of some embodiments of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 shows the construction of an ophthalmologic apparatus to which the present invention is applied.  
         [0009]    [0009]FIG. 2 is a front view of an optical element with a prism used for alignment detection.  
         [0010]    [0010]FIG. 3 shows an example of the display by a display.  
         [0011]    [0011]FIG. 4 shows the construction of another embodiment of the ophthalmologic apparatus.  
         [0012]    [0012]FIG. 5 is a front view of an optical element in FIG. 4. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0013]    [0013]FIG. 1 shows an ophthalmologic apparatus to which the present invention is applied, herein a compound machine of a refractometer for measuring the eye refractive power of an eye to be examined and an auto-keratometer for effecting the measurement of the cornea of the eye to be examined. The present invention is not restricted thereto, but is also applicable various ophthalmologic apparatuses (such as a tonometer and an eyeground examining apparatus) in which the alignment of an optical system relative to an eye to be examined is necessary.  
         [0014]    On a base  1 , there is provided a driving mechanism  2  including three motors, and a measuring unit  3  containing a measuring optical system therein is mounted on the driving mechanism  2 . The driving mechanism  2  drives the measuring unit  3  in any three-dimensional direction. On the operator side (the right side as viewed in FIG. 1) of the base  1 , there are provided a measuring switch  4  and an operating device  5  such as a track ball or a joy stick. A ring light source  6  for cornea measurement is provided on the panel of the eye to be examined E side (the left side as viewed in FIG. 1) of the measuring unit  3 , and a mode changeover device  7  is provided on the panel of the operator side thereof.  
         [0015]    On an optical path  01  behind the ring light source  6 , there are successively arranged a dichroic mirror  8  reflecting visible light, a lens  9 , an apertured mirror  10 , a stop  11  conjugate with the pupil, a lens  12  and a light source  13  for refraction measurement. On the optical path in the incidence direction of the dichroic mirror  8 , there are arranged an objective lens  14 , a half mirror  15 , a dichroic mirror  16  reflecting visible light, and a light source  17  for alignment, and the light source  17  for alignment is disposed near the focus of the objective lens  14 . On the optical path in the reflecting direction of the dichroic mirror  16 , there are disposed a diopter varying lens  18  and a fixation target  19 . On the optical path in the reflecting direction of the half mirror  15 , there are successively arranged an optical element  21  for alignment measurement selectively insertable into the optical path, a lens  22 , a dichroic mirror  23 , a stop  24  for cornea measurement selectively insertable into the optical path, and an area sensor (an array sensor such as a CCD)  25 . FIG. 2 shows the details of the optical element  21 . It is of such structure that two wedge prisms  20  are attached to the surface of a light-transmitting substrate, and has the function of deflecting and separating part of light incident on the optical element  21  by the wedge prisms  20 . An actuator  26  including a plurality of solenoids is provided to retractably insert the optical element  21  and the stop  24  into the optical path. On the optical path in the reflecting direction of the apertured mirror  10 , there are arranged a six-hole stop  27  conjugate with the pupil, a separating prism  28  and a lens  29 , and this optical path leads to the dichroic mirror  23 . The output of the area sensor  25  is electrically connected to a controller  30  including a microprocessor, and the output of the controller  30  in turn is connected to the driving mechanism  2 . The measuring switch  4 , the operating device  5  and the mode changeover device  7  are also electrically connected to the controller  30 .  
         [0016]    In the above-described construction, the measuring unit  3  is three-dimensionally moved on the base  1  by the driving mechanism  2 , whereby the alignment of the measuring optical system relative to the eye to be examined E is effected. A beam from the light source  13  for refraction measurement passes through the lens  12 , the stop  11 , the apertured mirror  10 , the lens  9  and the dichroic mirror  8 , and is projected onto the fundus of the eye to be examined E. The reflected light from the fundus of the eye returns along the same optical path is reflected by the apertured mirror  10 , passes through the six-hole stop  27 , the separating prism  28  and the lens  29 , is reflected by the dichroic mirror  23  and is received by the area sensor  25 . The six positions of the received beam are calculated by the controller  30  to thereby calculate the eye refraction value. During the measurement of the eye to be examined, the fixation target  19  is presented on the eye to be examined E through the diopter varying lens  18 , the dichroic mirror  16 , the half mirror  15 , the objective lens  14  and the dichroic mirror  8 . Also, the front eye part of the eye to be examined E is imaged on the area sensor  25  by an imaging optical system including the objective lens  14  and the lens  22 . This imaging optical system is used for cornea measurement as well as for the alignment of the front eye part.  
         [0017]    The optical element  21  and the stop  24  are exclusively put into and out of the optical path by the actuator  26 . That is, during alignment, the optical element  21  is inserted into the optical path and the stop  24  is put out of the optical path. On the other hand, during cornea measurement, the optical element  21  is put out of the optical path and in operative association therewith, the stop  24  is inserted into the optical path. Actuators  26  may be provided discretely for the optical element  21  and the stop and be individually driven.  
         [0018]    The optical element  21  deflects transmitted light in the left and right directions as indicated by arrows in FIG. 2 by the two wedge prisms  20  provided thereon. The upper wedge prism  20  has such a cross-sectional shape as deflects the beam to the right side as viewed in FIG. 2, and the lower wedge prism  20  has such a cross-sectional shape as deflects the beam to the left side as viewed in FIG. 2. The other portion than the wedge prisms  20  does not deflect the light beam but makes the beam rectilinearly travel and be transmitted. Thereby, the beam incident on the wedge prisms  20  and the other beam are separated (divided). The number of the wedge prisms need not be two, but if the algorithm of signal processing which will be described later is changed, the number of the wedge prisms may be three, four, . . . or one and the detection of alignment state will be possible.  
         [0019]    [0019]FIG. 3 shows an example of the display by a display  31 , and the output image of the area sensor  25  is displayed. Corneal reflected images R 1  and R 2  by the light source  17  for alignment are displayed on a front eye part image E′, and further an alignment mark A is displayed. A small circle at the center of the alignment mark A coincides with the optical axis. Here, the corneal reflected images R 2  are provided by a beam deflected by the wedge prisms  20  on the optical element  21 , and the corneal reflected image R 1  is provided by a beam not deflected but rectilinearly travelling through the optical element  21 . Unless the corneal reflected image R 1  and the area sensor  25  are conjugate with each other, the two corneal reflected images R 2  rotate about R 1  as shown, but if they become conjugate with each other, the line linking the two corneal reflected images R 2  together will become a horizontal line. Consequently, if three-dimensional alignment is perfect, all the corneal reflected images R 1  and R 2  lie in a straight line on the horizontal alignment mark A, and R 1  overlaps the center of the alignment mark A.  
         [0020]    The controller  30  calculates the positions of the corneal reflected images R 2  and R 1  on the basis of a signal from the area sensor  25  to thereby calculate the alignment state, i.e., the degree (amount) and direction of the positional deviation, of the eye to be examined E relative to the optical system. The wedge prisms  20  are sufficiently small as compared with the size of an opening around them and therefore, it does not happen that a front eye part image weak in reflection is reflected in overlapping relationship therewith. Also, these beams passed through the optical element  21  are deep in depth of focus and therefore, even if the distance therebetween is considerably great, it is possible to reflect the corneal reflected images R 2 , and the alignment state can be reliably recognized by calculation. The controller  30  drives the driving mechanism  2  on the basis of the detected alignment state in such a direction and amount of movement that the deviation becomes null, and executes auto-alignment. The mode in which the controller  30  automatically controls the driving mechanism  2  on the basis of the detection of the alignment state so as to eliminate this alignment deviation is called the “auto mode”. In contrast, the mode in which automatic control is not effected, but the driving mechanism  2  is driven on the basis of a signal from the operating device  5  is called the “manual mode”.  
         [0021]    Description will now be made of sequences which the apparatus according to the present embodiment has, i.e., a sequence in which shift is automatically made between the manual mode and the auto mode and alignment is effected, and a sequence in which measurement is automatically started when alignment is completed.  
         [0022]    At the start of the alignment relative to the eye to be examined, usually great positional deviation takes place beyond a predetermined range within which auto-alignment is possible, and the display as shown in FIG. 3 cannot be obtained. Consequently at first, the auto mode does not operate and an operator manually effects alignment roughly by the manual mode. That is, the operator operates the operating device  5  to thereby move the measuring unit  3  while looking at the eye to be examined E on the display  31 , and adjusts the measuring unit so that the pupil may come into the screen as shown in FIG. 3. The controller  30  controls the driving mechanism  2  on the basis of the operation of the operating device  5  and in the meantime, the controller  30  continues the detection of the alignment state from the signal of the area sensor  25 . When the detected amount of alignment deviation has come to lie in the predetermined range within which auto-alignment is possible, the controller  30  automatically shifts the apparatus from the manual mode to the auto mode to thereby start the auto-alignment operation.  
         [0023]    When the auto-alignment operation has been entered, characters “ALIGNMENT WORKING” are indicated on the display  31  as shown in FIG. 3, thereby informing the operator that auto-alignment is being executed. When the operation confirms this indication and releases the operating device  5 , alignment will be automatically completed with nothing being operated thereafter. The way of indication on the display  31  is not limited to this, but may be by a change in the flash, luminance, color or the like of the display. Also, while in the present embodiment, the character indication on the display  31  is an indicator for enabling the operator to distinguish between the auto/manual modes, there may also be visual or aural indication techniques. For example, an indicator comprising a lamp for exclusive use may be provided at a location on the apparatus which can be seen by the operator so as to indicate the distinction between the auto/manual modes to the operator by the turning-on thereof or a change in the color thereof. Otherwise, some kind of sound may be used as the indicator. At any rate, it is important to indicate by the indicator that shift has been made from the manual mode to the auto mode, thereby informing the operator that the operation thereafter is not necessary.  
         [0024]    The controller  30 , if the sequentially calculated alignment deviation is within a range smaller than a prescribed value, judges that the alignment has been completed. Subsequently, it automatically starts the measurement of the eye to be examined (the measurement of eye refractive power and cornea shape). That is, even if the operator does not depress the measuring switch  4 , the measurement of the eye to be examined is automatically started after the completion of the auto-alignment and therefore, operability is good. During the measurement, the optical element  21  is retracted out of the optical path by the actuator  26 , the stop  24  is inserted, the ring light source  6  is turned on and the corneal reflected image therefrom is received by the area sensor  21 , and the signal thereof is calculated by the controller  30  to thereby find the measured value of the eye to be examined.  
         [0025]    On the other hand, even if auto-alignment is working, when the operator operates the operating device  5 , priority is given to the manual operation. That is, when the operator desires the manual operation for some reason or other, the auto mode becomes off and the manual mode is automatically restarted. At this time, the indicator changes and therefore, the operator can confirm that the auto mode has been released. Even if the manual mode is working, when the operator discontinue the operation of the device  5  and the signal from the operating device  5  is interrupted for a predetermined time (e.g. one second), the auto mode is automatically restarted and auto-alignment driving is resumed again. Also during the manual mode, the controller  30  continues to recognize the alignment state from the signal of the area sensor  25 , and when it judges that the alignment has been completed, it immediately starts measurement. When the operator depresses the measuring switch  4  even if the alignment is not yet completed, measurement is effected with priority given thereto. As described above, the auto mode and the manual mode are automatically changed over without the changeover operation being performed and therefore, an ophthalmologic apparatus excellent in operability is provided. Also, priority is given to the operators intention (operation) and therefore safety is high. This sequence is effective when for example, the eye to be examined has an exceptional characteristic and the corneal reflected images R 2  are not sufficiently obtained and the auto-alignment does not work well.  
         [0026]    While the sequence in which the manual/auto modes are automatically changed over has been described above, a manual fixed mode can be provided if the operator designates it by the mode changeover device  7 . When the manual fixed mode is selected, the auto mode does not work and the controller  30  moves the position of the measuring unit  3  by the driving mechanism  2  on the basis of the signal of the operating device  5 . The operator visually observes the display  31  and effects alignment, and when he confirms perfect alignment, the apparatus carries out the measurement of the eye to be examined if the operator depresses the measuring switch  4 . That is, the auto mode does not work at all from the first to the last.  
         [0027]    A modification of the above-described embodiment will now be described. FIG. 4 shows the general construction of the modification, and in FIG. 4, the same reference numerals as those in FIG. 1 designate the same members. As compared with the embodiment of FIG. 1, this modification differs in the structure, and location of an optical element  35 , and greatly differs in that the actuator for moving it is unnecessary. The ring light source  6  for cornea measurement illuminates the cornea of the eye to be examined E by parallel light, and the optical element  35  is disposed near the focus point of imaging optical system of the lens  14  and the lens  22 .  
         [0028]    [0028]FIG. 5 shows a front view of the optical element  35 . An opening  36  for transmitting therethrough the wavelength of the ring light source  6  for measurement is provided in the central portion of a transmissive substrate, and dichroic film having the characteristic of not transmitting the wavelength of the ring light source  6  therethrough but transmitting therethrough the wavelength of the light source  17  for alignment is formed around the opening  36 . The opening  36  functions as a stop during cornea measurement and therefore, the stop  24  in the aforedescribed embodiment is unnecessary. Openings comprising two wedge prisms  37  used for alignment are formed outside the opening  36 . These wedge prisms  37  are located around an opening in an imaging optical system comprising the objective lens  14  and the lens  22 . The number of the wedge prisms is not limited to two as previously described.  
         [0029]    According to the construction of the present embodiment, the wavelength of the light source  17  for alignment is transmitted through all portions of the optical element  35  and therefore, during both of measurement and alignment, the optical element  35  may be placed in the optical path and need not be moved. An actuator therefor becomes unnecessary and the construction is simple and high in reliability.  
         [0030]    Further, as the imaging optical system of the lens  14  and the lens  22 , and the area sensor  25  are used both for three-dimensional alignment and cornea measurement of the construction is simple.

Technology Classification (CPC): 0