Abstract:
An ophthalmic measuring device for obtaining three-dimensional information of an eye to be examined without time lag by projecting pulsed light chirped in such a manner that color is continuously changed from the leading end through the tail end of a pulsed light with time on the eye to be examined, cutting out the pulsed light reflected from the eye to be examined at a predetermined timing by a shutter, and obtaining spectroscopic distribution characteristic of the cut-out image by a spectroscopic unit.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an ophthalmic measuring device using pulsed light chirped in such a manner that color is continuously changed from the leading end through the tail end of a pulsed light with time.  
           [0003]    2. Description of the Related Art  
           [0004]    In the ophthalmic measurement of the related art, a reference mark is projected on the eye to be examined, and then the distance or the shape of the eye to be examined is obtained from defocusing or position of the image of the reference mark reflected from the eye to be examined.  
           [0005]    However, in the related art described above, a complicated mechanism using light scanning technology or the like is necessary to obtain three-dimensional information, and time lag due to scanning time is inevitable. In addition, there is a limit of measuring accuracy due to variations in intensity of reflected light from the eye to be examined or due to limits of accuracy of the reference mark.  
         SUMMARY OF THE INVENTION  
         [0006]    It is an object of the present invention to provide an ophthalmic measuring device for obtaining three-dimensional information of the eye to be examined without time lag by the steps of projecting a pulsed light chirped in such a manner that color is continuously changed from the leading end through the tail end of the pulsed light with time on the eye to be examined, cutting out the pulsed light reflected from the eye to be examined by a shutter at a predetermined timing, and examining spectral distribution characteristics of the cut-out image by a spectroscope.  
           [0007]    Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments (with reference to the attached drawings). 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a block diagram of a ophthalmic measuring device according to a first embodiment.  
         [0009]    [0009]FIG. 2 is an explanatory drawing illustrating cutting-out of a color image from a reflected pulsed light.  
         [0010]    [0010]FIG. 3 is a block diagram of a ophthalmic measuring device according to a second embodiment.  
         [0011]    [0011]FIG. 4 is a front view of a linear spectroscopic prism.  
         [0012]    [0012]FIG. 5 is a drawing showing a principle of two-layer measurement using the linear spectroscopic prism.  
         [0013]    [0013]FIG. 6 is an explanatory drawing illustrating each layer on the two-dimensional color image pick-up unit in the case in which the object to be examined S has three-layer structure.  
         [0014]    [0014]FIG. 7 is a front view of a number of prism blocs arranged on a substrate.  
         [0015]    [0015]FIG. 8 is an explanatory drawing illustrating the positions of coordinates on the two-dimensional color image pick-up unit.  
         [0016]    [0016]FIG. 9 is a block diagram of a ophthalmic measuring device according to a third embodiment.  
         [0017]    [0017]FIG. 10 is an explanatory drawing of a color film analysis unit.  
         [0018]    [0018]FIG. 11 is an explanatory drawing illustrating distribution of color images as mapped out in contours.  
         [0019]    [0019]FIG. 12 is an explanatory drawing illustrating distribution of color images as mapped out in contours.  
         [0020]    [0020]FIG. 13 is an explanatory drawing illustrating distribution of color images as mapped out in contours.  
         [0021]    [0021]FIG. 14 is an explanatory drawing illustrating distribution of color images of a color film as mapped out in contours.  
         [0022]    [0022]FIG. 15 is a block diagram of a fourth embodiment. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]    [First Embodiment] 
         [0024]    Referring now to the drawings, embodiments of the invention will be described in detail.  
         [0025]    [0025]FIG. 1 is a block diagram of a first embodiment. An objective lens  1 , a beam splitter  2 , an illuminating aperture diaphragm  3 , a relay lens  4 , a chirp light generating unit  5 , and a mode locked ti-sapphire laser light source  6  for emitting ultra-short pulsed light are arranged in sequence forwardly of the eye to be examined E. A light receiving aperture diaphragm  7  disposed in conjugation with the illuminating aperture diaphragm  3 , a projection lens  8 , an ultra high-speed non-linear optical shutter  9  of carbon disulfide molecular liquid, and a two-dimensional color image pick-up unit  10  are arranged in sequence in the direction of reflection of the beam splitter  2 . An output of a computing unit  11  for supplying timing signals for cutting out images at a certain timing is connected to the laser light source  6  and the ultra high-speed optical shutter  9 .  
         [0026]    The two-dimensional color image pick-up unit  10  is disposed at the position in conjugation with the eyeground Er of the eye to be examined E with respect to the objective lens  1 , the beam splitter  2 , the aperture diaphragm  7 , the projection lens  8 , and the ultra high-speed optical shutter  9 .  
         [0027]    The projection lens  8  is disposed in such a manner that the light receiving aperture diaphragm  7  coincides with the position of the front focus point for collecting light from the eyeground Er passed through the projection lens  8 .  
         [0028]    A pulsed light emitted from the laser light source  6  is guided while being blocked in the optical fiber having extremely thin core of high index of refraction in the chirp light generating unit  5  to generate non-linear optical effects and hence to cause frequency modulation of light pulses so that a pulsed light whereof the color varies regularly with time is generated. The pulsed light passed through the relay lens  4  and the illuminating aperture diaphragm  3 , and then though the beam splitter is converged to the point near the iris of the eye to be examined E by the objective lens  1  and then is illuminated to the eyeground Er. The light reflected from the eyeground Er leaves the iris again and enters into the objective lens  1 , and then is reflected from the beam splitter  2 , passed through the light receiving aperture diaphragm  7 , the projection lens  8 , and the ultra high-speed optical shutter  9 , and then projected on the two-dimensional color image pick-up unit  10 . The pulsed light from the laser light source  6  is obtained at the timing sent from the computing unit  11 , and the ultra high-speed optical shutter  9  is operated synchronously with the pulsed light. The computing unit  11  is connected to the image pick-up unit  10 , and processes signals from the image pick-up unit to display three-dimensional information of the eye to be examined on the display unit  12 .  
         [0029]    [0029]FIG. 2 is an explanatory drawing illustrating cutting out of the color image obtained by the two-dimensional color image pick-up unit  10 . The advanced position of a pulsed light reflected from the subject S differs depending on the height of the subject S. The pulsed light L 1  reflected at the high position is ahead of the pulsed light L 2  reflected at the lower position.  
         [0030]    The chirp light has longer wavelength at the leading end than the tail end of the pulse. When focusing attention on the cut-off timing A on the cut-off timing axis, the pulsed light L 1  reflected at the high position and the pulsed light L 2  reflected at the low position have different frequencies f at the common cut-off position B, and in the cut-off two-dimensional image, the former generates a color image Cb closer to blue in comparison with the latter, while the latter generates a color image Cr closer to red in comparison with the former.  
         [0031]    The color images Cb, Cr are to be displayed in contrast to the positional information of the subject S, and information of height or depth is only for the surface or a plane.  
         [0032]    It is needless to say that the method of display is not limited to display in colors, but some other methods of display may also be employed. For example, it may be displayed by contours, numerous value, cross sections, or concentrations.  
         [0033]    [Second Embodiment] 
         [0034]    [0034]FIG. 3 is a block diagram showing a multi-layer measuring system according to the second embodiment in which information of a plurality of items such as depth or distance are obtained. The same reference numerals as in FIG. 1 represent the same parts. A substrate  22  provided with a linear spectroscopic prism  21  is disposed between the ultra high-speed shutter  9  and the two-dimensional color image pick-up unit  10 . The light source unit, that is, the ultra-short pulsed light generating portion is the same as the one in FIG. 1, and thus is omitted.  
         [0035]    The pulsed light passed through the illuminating aperture diaphragm  3  passed through the beam splitter  2 , and then converged at the point in the vicinity of the iris of the eye to be examined E by the objective lens  1 , and then irradiated on the eyeground Er. The light reflected from the eyeground Er leaves the iris again and enters into the objective lens  1 , and subsequently, is reflected from the beam splitter  2 , then passes through the light receiving aperture diaphragm  7 , the projection lens  8 , the ultra high-speed optical shutter  9 , and the linear spectroscopic prism  21  on the substrate  22  and then projected on the two-dimensional color image pick-up unit  10 .  
         [0036]    In FIG. 2, when the pulsed light L 1  reflected at the high position and the pulsed light L 2  reflected at the low position are on the same advancement axis, that is, in the case of multi-layer measurement, the pulsed light L 1  reflected at the high position and the pulsed light L 2  reflected at the low position are aligned. Therefore, though one is at the position ahead of the other, they cannot be separated by the two-dimensional color image pickup unit  10  in this case.  
         [0037]    [0037]FIG. 4 is a front view of the linear spectroscopic prism  21 , and FIG. 5 is an explanatory drawing of a two-layer measurement. The portion other than the spectroscopic prism  21  on the front surface of the substrate  22  is covered by a douser  23 . For example, when the subject S is double-layer structure, the light from the eyeground Er is separated toward two directions that are appropriate to an apex angle of the spectroscopic prism  21  such as a red beam La and a blue beam Lb by the spectroscopic prism  21 , and then recognized as a red image signal Pa, and a blue image signal Pb in the two-dimensional color image pick-up unit  12 . The amount of separation will be the extent corresponding to the position thereof in the second coordinate S 2  as well.  
         [0038]    Information of the depth or the height on the line corresponding to the length of the linear spectroscopic prism  21  may be obtained by covering the portion other than the spectroscopic prism  21  by the douser  23  in this state as shown in FIG. 5.  
         [0039]    The case in which the subject S has a two-layer structure is described in this embodiment, when the number of layer is more than two, the number of color separations corresponds to the number of layers. FIG. 6 shows each layer on the two-dimensional color image pick-up unit  10  in the case where the subject S has a three-layer structure. The three-layer structure on the meridians of eye can be numerically obtained by obtaining the positions of the tree-layers Pa, Pb, Pc in the first coordinate, the positions of the three-layers Pa′, Pb′, Pc′ in the second coordinate, and the positions of the three-layers from the third coordinate on. The number of layers is not limited thereto, but analysis of the multi-layer structure is possible.  
         [0040]    [0040]FIG. 7 shows a state in which a number of prism blocks  24  are regularly arranged on the substrate  22  instead of a linear spectroscopic prism  21 . In this case, separation by the number of the layers may be performed by the prism block  24  at this position. For example, the three-layer separated image generated by the prism block  24 ′ is represented as the coordinate Qa, Qb, Qc on the two-dimensional color image pick-up unit  10  shown in FIG. 8, and the same results may be obtained from other prism blocks  24  arranged regularly.  
         [0041]    The same effect is expected by using a Fresnel prism instead of arranging the prism blocks  24 , and shielding the position other than the coordinate to be measured by the douser  22 .  
         [0042]    [Third Embodiment] 
         [0043]    [0043]FIG. 9 shows a third embodiment in which a color film  31  is disposed instead of the two-dimensional color image pick-up unit  10 , and the color image is picked up by the color film  31 . Further detailed positional coordinate and the map of the distance or the depth of the image recorded on the color film  31  may be created by analyzing the color of the image by a spectroscope.  
         [0044]    [0044]FIG. 10 is a block diagram of the analyzing apparatus for images on the color film. A condenser lens  33 , a color film  34 , an imaging lens  35 , and a spectroscope  36  are arranged forwardly of the while color light source  32 .  
         [0045]    The light from a white light source  32  is converted on the color film  34  via the condenser lens  33 , and illuminated and spotlighted. The light passed through the color film  34  enters into the spectroscope  36  via a light-beam pick-up window  36   a  and then split up.  
         [0046]    Spectroscopic information by each coordinate may be obtained from the whole color film  34  by performing flat bed scanning on the plane of the color film  34 . This spectroscopic information allows obtaining of the layer structure on the plane or the solid structure with respect to the color information and the layer structure of the subject S.  
         [0047]    [0047]FIG. 11, FIG. 12, and FIG. 13 respectively represent color image distributions on the color film  34  as mapped out in contours by each of three layers. They are represented by, depending on the height of the plane of reflection, a first contour C 11 , a second contour C 12 , a third contour C 13 , a fourth contour C 14 , and a fifth contour C 15  on the first layer, a first contour C 21 , a second contour C 22 , a third contour C 23 , a fourth contour C 24 , and a fifth contour C 25  on the second layer, and a first contour C 31 , a second contour C 32 , a third contour C 33 , a fourth contour C 34 , and a fifth contour C 35  on the third layer.  
         [0048]    [0048]FIG. 14 represent color image distributions on the color film  34  as mapped out in contours by each of three layers. A plurality of color distributions D 1 , D 2  are displayed in the imaging region R as a first layer. Such color distributions D are converted into height information, and the detailed relation between the color and the height is displayed on a color scale  41 .  
         [0049]    The height information may be displayed as values in various cross sections. For example, the height of the cross section X is displayed by a scale  42  and a linear elevation Hi.  
         [0050]    Given that it is three-layer display for example, the color distribution may be displayed by each layer by switching operation. In the cross section X, it may be displayed as, for example, a linear elevation H 2  or a linear elevation H 3  after being combined with the linear elevation H 1 . The cross section may be selected freely in rotation. When the second cross section X′ is selected, a linear elevation corresponding thereto is displayed. It is also possible to display the image of the eyeground, which is the object to be measured, with the contour display of the color image distribution overlapped thereon.  
         [0051]    [Fourth Embodiment] 
         [0052]    [0052]FIG. 15 shows a fourth embodiment using an afocal light receiving system, which is capable of measuring the anterior ocular segment. The same reference numerals as those in FIG. 1 represent the same parts in the optical system. An adapter lens  51  is disposed between the objective lens  1  and the eye to be examined E. The anterior ocular segment Ep of the eye to be examined is to be disposed at the position in conjugation with the two-dimensional color image pick-up unit  10  with respect to the adapter lens  51 , the objective lens  1 , the beam splitter  2 , the light receiving aperture diaphragm  7 , the projection lens  8 , and the ultra high-speed non-linear optical shutter  9 .  
         [0053]    The light from the illuminating aperture diaphragm  3  is, after passing through the beam splitter  2 , converged once by the objective lens  1 , and then converted into a parallel light by the adapter lens  51  disposed so that the converging portion coincides with the rear focal point. Subsequently, it proceeds toward the eye to be examined E, and is reflected from the anterior ocular segment Ep.  
         [0054]    The light reflected from the anterior ocular segment Ep passes again through the adapter lens  51 , enters into the objective lens  1 , reflects from the beam splitter  2 , passes through the light receiving aperture diaphragm  7 , the projection lens  8 , and the ultra high-speed non-linear optical shutter  9 , and is projected on the two-dimensional color image pick-up unit  10 . By cutting out this reflected light at a certain timing by the computing unit  11 , the two-dimensional color image having color distribution corresponding to the configuration of the anterior ocular segment Ep may be obtained.  
         [0055]    Handling and display of the image may be performed in accordance with the description in conjunction with FIG. 3 through FIG. 14.  
         [0056]    As is described thus far, according to the invention, necessity of mechanical mechanisms such as a light scanning mechanism may be eliminated, and time lag hardly occurs. In addition, the invention enables provision of three-dimensional information of the eyeground, which is improved in terms of accuracy.  
         [0057]    While the present invention has been described with reference to what are presently considered to be the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. On the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.