Patent Application
20200260952
The present invention relates to a scanning type ocular fundus imaging device that two-dimensionally scans and projects laser light on an ocular fundus and receives reflected light from the ocular fundus to capture an image of the ocular fundus.
A scanning type ocular fundus imaging device is known which two-dimensionally scans laser light in a horizontal direction and a vertical direction, illuminates an ocular fundus with the two-dimensionally scanned laser light, and receives reflected light from the ocular fundus to capture an image of the ocular fundus.
In such a scanning type ocular fundus imaging device, the light ray illuminating the ocular fundus is reflected from the surface of an objective lens and incident on a light. receiving element, so that a center spot image due to the reflected light occurs at the center of the captured image of the subject eye and deteriorates the image quality. In a proposed configuration to eliminate such deterioration, a light shielding member is disposed at a position at which the image of a laser irradiation area on the objective lens plane is formed, harmful reflected light from the lens plane of the objective lens is prevented from being incident on the light receiving element, and an image of the ocular fundus is captured with high image quality (the following Patent Document 1).
In general, the objective lens is composed of a plurality of lenses rather than a single lens, and particularly in a wide-angle scanning type ocular fundus imaging device, the objective lens is composed of a lens group having three or more lenses. In such a scanning type ocular fundus imaging device, the focal length of an objective lens is shorter than the thickness, the ocular fundus conjugate plane may overlap any of lens planes of the lens group, and the reflected light generated at the lens plane overlapping the ocular fundus conjugate plane becomes harmful light (center spot image) to deteriorate the captured image quality.
Moreover, when performing diopter adjustment, the ocular fundus conjugate plane overlaps any of lens planes of the objective lens group depending on the diopter of the subject eye, thus causing the same problem.
The present invention has been made to solve such a problem, and an object of the present invention is to provide a scanning type ocular fundus imaging device that can capture an image of an ocular fundus with high image quality by shielding the harmful reflected light ray due to the reflection from a lens plane of an objective lens composed of a plurality of lenses.
The present invention (claim 1) provides a scanning type ocular fundus imaging device comprising:
a light projecting optical system that projects light from a light source on an ocular fundus of a subject eye via an objective lens optical system, the light being scanned as scanned illumination light using a scanning optical system;
a light receiving optical system that receives reflected light from the ocular fundus via the objective lens optical system and the scanning optical system;
a diopter adjusting mechanism that moves an ocular fundus conjugate plane formed by the objective lens optical system in an optical axis direction;
a light receiving pinhole disposed in the vicinity of an ocular fundus conjugate position in the light receiving optical system; and
a light shielding member disposed in the light receiving optical system to shield harmful reflected light from a lens plane of the objective lens optical system,
wherein the objective lens optical system is composed of a first lens group and a second lens group disposed at a distance from the first lens group in the optical axis direction, and the ocular fundus conjugate plane is located between the first and second lens groups of the objective lens optical system within a diopter adjustment range by the diopter adjusting mechanism.
The present invention (claim 10, 11) provides a scanning type ocular fundus imaging device comprising:
a light projecting optical system that projects light from a light source on an ocular fundus of a subject eye via an objective lens optical system, the light being scanned as scanned illumination light using a scanning optical system;
a light receiving optical system that receives reflected light from the ocular fundus via the objective lens optical system and the scanning optical system;
a light receiving pinhole disposed in the vicinity of an ocular fundus conjugate position in the light receiving optical system; and
a light shielding member disposed in the light receiving optical system to shield harmful reflected light from a lens plane of the objective lens optical system.
In the invention of claim 10, the light receiving optical system and the objective lens optical system are configured such that a light beam of scanned back-projection light is separated on the lens plane of the objective lens optical system from a light beam of the scanned illumination light, wherein the scanned back-projection light is scanned by the scanning optical system after exiting the light receiving pinhole and passing through the light shielding member, wherein the same scanning as that for the scanned back-projection light performed for the scanned illumination light, while in the invention of claim 11, the light receiving optical system and the objective lens optical system are configured such that a light beam of scanned back-projection light is separated on the ocular fundus conjugate plane from a light beam of reflected light of the scanned illumination light from the lens plane of the objective lens optical system, wherein the scanned back-projection light is scanned by the scanning optical system after exiting the light receiving pinhole and passing through the light shielding member, wherein the same scanning as that for the scanned back-projection light is performed for the scanned illumination light.
In the present invention (claim 1), the ocular fundus conjugate plane is located in a space between the first lens group and second lens group of the objective lens optical system; therefore, the ocular fundus conjugate plane does not overlap a lens plane of the first or second lens group and it is possible to effectively prevent the occurrence of a center spot image due to harmful reflected light from the objective lens plane.
Moreover, in the present invention (claim 10), on a lens plane of the objective lens optical system, the light beam of the scanned back-projection light scanned by the scanning optical system after exiting the light receiving pinhole and passing through the light shielding member does not overlap the light beam of the scanned illumination light for which the same scanning as that for the scanned back-projection light is performed, and it is therefore possible to reliably prevent the occurrence of a center spot image.
Furthermore, in the present invention (claim 11), on the ocular fundus conjugate plane, the light beam of the scanned back-projection light scanned by the scanning optical system after exiting the light receiving pinhole and passing through the light shielding member does not overlap the light beam of the reflected light of the scanned illumination light from a lens plane of the objective lens optical system, for which the same scanning as that for the scanned back-projection light is performed, and it is therefore possible to reliably prevent the occurrence of a center spot image.
Hereinafter, the present invention will be described in detail on the basis of one or more examples or embodiments with reference to the drawings
The laser light incident on the optical path splitting mirror 14 is reflected therefrom and incident on a horizontal scanning device 20 and is scanned at high speed in the horizontal direction (main scanning direction). The horizontal scanning device 20 is composed, for example, of a polygon mirror. The laser light scanned at high speed is incident on a vertical scanning device 23 via scanning relay lenses 21 and 22 and scanned at low speed in the vertical direction (sub-scanning direction). The vertical scanning device 23 is composed, for example, of a galvanomirror. The horizontal scanning device 20, the scanning relay lenses 21 and 22, and the vertical scanning device 23 constitute a scanning optical system 2.
The laser light scanned in the horizontal and vertical directions by the scanning optical system 2 is incident on an objective lens optical system. 3 that is composed of a first lens group (which may be a single lens) 30 and a second lens group (which may be a single lens) 31. As illustrated in
The laser light scanned two-dimensionally by the scanning devices 20 and 23 is incident as scanned illumination light on the pupil 50a of the subject eye 50 via the objective lens optical system 3 and projected on the ocular fundus 50b. The ocular fundus 50b is raster-scanned with the laser light in the horizontal and vertical directions, and the ocular fundus 50b in the scanning area is illuminated with the laser light.
The laser light projected on the ocular fundus 50b is reflected from the ocular fundus 50b, and the reflected light travels in the same optical path in the opposite direction and passes through the objective lens optical system 3. The objective lens optical system 3 is configured such that, as illustrated in
The laser light having passed through the objective lens optical system 3 is reversely scanned in the vertical and horizontal directions by the scanning optical system 2 and incident on the optical path splitting mirror 14 as the same light ray as before being incident on the scanning optical system 2. The optical path splitting mirror 14, which is disposed so that its center coincides with the optical axis, passes the reflected light from outside of the mirror to the light receiving optical system 4 and therefore splits the optical path into a light projecting optical path and a light receiving optical path. On the other hand, the optical path on the subject eye side of the optical path splitting mirror 14 is an optical path common to the light projecting optical system 1 and the light receiving optical system 4.
The light receiving optical system 4 is composed of a light receiving lens 40, a light shielding member 41, a light receiving pinhole 42, and a light receiving element 43. The reflected light from the ocular fundus 50b having passed through the optical path splitting mirror 14 passes through the light shielding member 41, the light receiving lens 40, and the light receiving pinhole 42 and is received by the light receiving element 43. The light receiving pinhole 42 is disposed in the vicinity of a position conjugate with the ocular fundus 50b. The light shielding member 41 is disposed in the vicinity of a position conjugate with the anterior ocular part, for example, the pupil or the crystalline lens, of the subject eye and shields the harmful reflected light from a lens plane of the objective lens optical system 3.
The light receiving element 43, which is composed of a photodiode, for example, sends luminance information at each point of the raster-scanned ocular fundus 50b to an image processing unit 44. The image processing unit 44 creates an ocular fundus image from the scanning position of the ocular fundus 50b and its luminance information. Although not illustrated, the ocular fundus image thus created is stored in a storage device, displayed on a display, or printed by a printer.
In the present example, a diopter adjusting mechanism for diopter adjustment of the subject eye 50 is provided in each of the light projecting optical system 1 and the light receiving optical system 4. As illustrated in
If the ocular fundus conjugate plane 32 overlaps a lens plane of the objective lens optical system 3, the occurrence of a center spot image (false image) that causes harmful light due to reflection from the objective lens plane cannot be avoided. In the objective lens optical system 3 of the present example, therefore, the first and second lens groups 30 and 31 are disposed at a distance from each other in the optical axis direction so that the ocular fundus conjugate plane 32 exists in the space therebetween. Thus, even when the objective lens is composed of a plurality of lens groups, the ocular fundus conjugate plane does not overlap an objective lens plane, and the occurrence of a center spot image can be prevented.
During the diopter adjustment, the ocular fundus conjugate plane 32 moves along the optical axis in the space between the first lens group 30 and the second lens group 31 and may possibly overlap a lens plane of the first or second lens group depending on the diopter adjustment. In the present example, therefore, the distance between the first lens group 30 and the second lens group 31 is set such that the ocular fundus conjugate plane 32 is located at a position that is not close to or does not overlap a lens plane of the first or second lens group. As illustrated in
In such a configuration, when capturing an image of the ocular fundus, the laser light source 10 is turned on. The light from the laser light source 10 is split in the optical path by the optical path splitting mirror 14 via the light projecting optical system 1 and scanned two-dimensionally in the horizontal and vertical directions by the scanning optical system 2, passes through the objective lens optical system 3, and is projected as the scanned illumination light on the ocular fundus 50b of the subject eye 50.
The ocular fundus 50b of the subject eye 50 is raster-scanned with the laser light, and the reflected light from the ocular fundus 50b passes through the objective lens optical system 3, the scanning optical system 2, and the optical path splitting mirror 14 and is incident on the light receiving optical system 4. Most of the harmful reflected light is removed by the optical path splitting mirror 14, and the harmful reflected light from an objective lens plane is shielded by the light shielding member 41 and the light shielding part of the light receiving pinhole 42. This allows the light receiving element 43 to receive the reflected light from the ocular fundus without a center spot image (false image due to harmful light). The light receiving element 43 sends the luminance information of each point of the raster-scanned ocular fundus 50b to the image processing unit 44, which creates an ocular fundus image from the scanning' position of the ocular fundus 50b and its luminance information and provides the captured image of the ocular fundus.
When adjusting the diopter of the subject eye, the collimator lens 13 of the light projecting optical system and the light receiving lens 40 of the light receiving optical system 4 are moved in association with each other thereby to adjust the diopter. The diopter adjustment is usually performed within a range of −10 diopter to +10 diopter. In the diopter adjustment within this range, as illustrated in
Moreover, the diopter adjusting mechanism is provided in each of the light projecting optical system and the light receiving optical system rather than on the common optical path of these systems, and the diopter adjustment can therefore be reliably performed because it is not necessary to incline the diopter adjusting lenses with respect to the optical axis to avoid the occurrence of a center spot image.
In the present example, as illustrated in
The upper part of
On the other hand, the middle part of
The light beams 61 and 63 on the ocular fundus conjugate plane 32 and the light beams 60 and 62 on the lens plane of the objective lens optical system illustrated in the lower part of
Referring again to the lower part of
In the example illustrated in
As illustrated in
On the other hand, when the light beams 63 and 61 are separated on the ocular fundus conjugate plane 32, light beams 63′ and 61′ on the light receiving pinholes 42 corresponding to the light beams 63 and 61 are also separated because the light receiving pinhole 42 is on the ocular fundus conjugate plane. The light beam 63′ forms an ocular fundus image while the light beam 61′ is the harmful reflected light from the lens reflection plane and therefore shielded by the light shielding part of the light receiving pinhole 42. Accordingly, the light beams 63 and 61 being separated on the ocular fundus conjugate plane 32 is the second condition that a center spot image does not occur. Thus, two conditions of the first and second conditions being satisfied in the simulation means that the harmful reflected light generated due to the reflection of the scanned illumination light from the same lens plane can be shielded by the combination of the light shielding member 41 and the light receiving pinhole 42.
Even when both the above-described first and second conditions are not satisfied, that is, when only one of the conditions is satisfied, it is possible to shield the harmful reflected light generated due to the reflection from a lens plane of the objective lens optical system. Accordingly, parameters such as the hole diameter of the light receiving pinhole 42 of the light receiving optical system, the diameter of the light shielding plane of the light shielding member 41, and the power distribution and lens shapes of the objective lens optical system are set such that a state is made in which the light beam of the scanned back-projection light and the light beam of the scanned illumination light do not overlap each other on a lens plane of the objective lens optical system or a state is made in which the light beam of the scanned back-projection light and the light beam of the reflected light of the scanned illumination light from the same lens plane do not overlap each other on the ocular fundus conjugate plane.
Additionally or alternatively, the above-described first condition or second condition should be satisfied in the entire range of the diopter adjustment by the diopter adjusting mechanism. For example, if the ocular fundus conjugate plane 32 is located at a position as illustrated in
On the other hand,
The above-described first condition that the two light beams 60 and 62 are separated on the lens plane 33 of the objective lens optical system 3 or the second condition that the two light beams 61 and 63 are separated on the ocular fundus conjugate plane 32 should be satisfied at each scanning angle (scanning point) of the scanning optical system 2. The upper part of
While
Regarding the size of the light shielding member 41, it is preferred to set the size ratio between the light beam image of the scanned illumination light and the image of the light shielding member 41 on the pupil plane of the pupil 50a of the subject eye within a range of 1:1 to 1:4. As the ratio becomes smaller, the optical system can capture an image even with a small pupil diameter, which is advantageous in capturing the image of an ocular fundus, but on the other hand, a center spot image is more likely to occur. In contrast, as the ratio becomes larger, a center spot image is less likely to occur, which is advantageous in removing false image, but there is a disadvantage that a bright fundus image cannot be obtained for a patient with a small pupil diameter.
The harmful reflected light (center spot image) is generated not only on the lens plane 33 of the second lens group 31 as described above but also on the lens plane 34 of the first lens group 30 as illustrated in
Thus, even if the two light beams 61 and 63 cannot be separated on the ocular fundus conjugate plane 32, when the two light beams 60 and 62 do not overlap each other on the lens plane 34 of the objective lens optical system, the occurrence of a center spot image can be reliably prevented.
When the diopter is adjusted in the minus direction, the ocular fundus conjugate plane comes close to the second lens group 31 and a center spot image is likely to occur. To prevent this, in the case of the diopter adjustment in the minus direction, the light shielding member may have to be made larger than that at the case of the 0 diopter. However, it is difficult to continuously change the size of the light shielding member in accordance with the diopter. An example for solving this problem is illustrated in
In
Additionally or alternatively, in
In such a configuration, in a normal diopter adjustment range, as described above, the ocular fundus conjugate plane 32 formed by the objective lens optical system is located between the first and second lens groups 30 and 31. Most of the harmful reflected light is removed by the optical path splitting mirror 14 and the light receiving pinhole 42, and the harmful reflected light from an objective lens plane having passed through the light receiving pinhole 42 is shielded by the light shielding member 41. At this time, when the adjustment to the minus diopter is performed, the light shielding member 41 is continuously moved toward the light receiving pinhole 42 side in the direction opposite to the moving direction of the light receiving lens 40, and the apparent light shielding size increases accordingly to respond to a large center spot image. This allows the same effect to be obtained as that when the light shielding member 41 is fixed and its size is continuously changed, without changing the size of the light shielding member 41.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-169819 | Sep 2017 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2018/032562 | 9/3/2018 | WO | 00 |
