JP5006129B2 - Scanning laser ophthalmoscope - Google Patents

Description

  The present invention relates to a scanning laser ophthalmoscope for capturing a fundus image by two-dimensionally scanning a laser beam on the fundus of an eye to be examined.

2. Description of the Related Art Conventionally, a scanning laser ophthalmoscope (scanning laser ophthalmoscope, abbreviated as SLO) is known in which a fundus image is obtained by scanning a laser beam two-dimensionally with respect to the fundus and receiving the reflection. . The ophthalmoscope is generally configured to perform main scanning of laser light using a rotating polygon mirror (see Patent Document 1).
JP 2006-239196 A

  However, when a rotating polygon mirror is used to scan a laser beam, the wind noise increases with an increase in scanning speed, or dust inside the apparatus that has been swollen by the wind generated by the rotating polygon mirror becomes an optical member (for example, a mirror). The noise component of the fundus image to be acquired. In order to solve such a problem, in a state where the rotating polygon mirror is stored in the storage case, an opening with a transparent member made of glass or resin as a protective window is provided in a part of the storage case. A method of isolation from the outside can be considered. By placing the rotating polygon mirror in the storage case in this manner, it is possible to suppress problems such as noise and dust, but the fundus reflection that is reflected by the rotating polygon mirror and passes through the transparent member as it is toward the light receiving element. Interference between the light component and the fundus reflection light component reflected by the rotating polygon mirror and reflected once by the front and back surfaces of the transparent member toward the light receiving element is likely to occur, and this is a new noise component of the fundus image acquired It is easy to become.

  In view of the above problems, an object of the present invention is to provide a scanning laser ophthalmoscope capable of suppressing noise caused by a rotary polygon mirror and obtaining a fundus image with little noise.

  In order to solve the above problems, the present invention is characterized by having the following configuration.

(1) An irradiation optical system for irradiating a fundus of a subject's eye with a laser beam emitted from a laser light source, and a polygon mirror and a galvanometer for two-dimensionally scanning the laser beam emitted from the laser light source on the fundus A scanning laser ophthalmoscope that has an irradiation optical system having a scanning unit composed of a mirror and a light receiving optical system that receives laser light emitted to the fundus of the subject's eye with a light receiving element, and captures a fundus image of the eye to be examined A storage case for storing the polygon mirror therein, a storage case having an opening for allowing laser light to enter and exit the polygon mirror, and a transparent member for closing the opening and transmitting the laser light And the transparent member formed so that the extended surface of the front surface and back surface of this transparent member may cross at a predetermined angle is provided.
(2) In the scanning laser ophthalmoscope of (1),
The transparent member is provided so as to be inclined with respect to a light receiving optical axis of the light receiving optical system.
(3) In the scanning laser ophthalmoscope of (2),
The transparent member is provided so as to be inclined with respect to a rotation axis of the rotary polygon mirror.

  According to the present invention, it is possible to suppress noise caused by the rotating polygonal mirror and obtain a fundus image with less noise.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a view showing an optical system of a scanning laser ophthalmoscope according to this embodiment.

  Reference numeral 1 denotes a light source that emits laser light having an infrared wavelength or visible wavelength. In this embodiment, a semiconductor laser, an SLD (super luminescence diode), or the like is used. 2 is a perforated mirror having an opening in the center, and 3 is a lens. Reference numerals 4 and 5 denote mirrors which are movable in the direction of the arrow shown in FIG. 1 and can perform focusing (diopter correction) by changing the optical path length. 6, 8 and 10 are concave mirrors. 7 is a polygon mirror (rotating polygonal mirror) that serves as a deflecting means for deflecting and scanning the laser light in the horizontal direction on the fundus of the eye to be examined (main scanning), and 9 is a laser perpendicular to the scanning direction by the polygon mirror 7. This is a galvanometer mirror serving as a deflecting means for deflecting and scanning light (sub-scanning).

  The laser light emitted from the light source 1 passes through the opening of the perforated mirror 2, passes through the lens 3, is reflected by the mirror 4, the mirror 5, and the concave mirror 6, and travels toward the polygon mirror 7. The light beam reflected by the polygon mirror 7 is reflected by the concave mirror 8, the galvano mirror 9, and the concave mirror 10, and then condensed on the fundus of the eye to be examined, and the fundus is two-dimensionally (in the XY axis direction shown in the drawing). ) Scan. An irradiation optical system for irradiating the fundus of the eye to be examined with laser light is formed by these optical members. In the present embodiment, the X-axis direction is the left-right direction (horizontal direction), and the Y-axis direction is the up-down direction.

  Reference numeral 11 denotes a lens, and reference numeral 12 denotes a pinhole plate having a pinhole on the optical axis. In the present embodiment, the diameter of the pores formed in the pinhole plate 12 is fixed. However, the present invention is not limited to this, and the diameter of the pores may be varied so that the contrast and brightness of the fundus image can be varied. It may be. The lens 11 places the observation point of the fundus of the eye to be examined and the pinhole plate at a conjugate position. Reference numeral 13 denotes a condensing lens, and reference numeral 14 denotes a light receiving element having sensitivity in the visible region and the infrared region. Note that an APD (avalanche photodiode) is used for the light receiving element 14 of the present embodiment.

  The reflected light of the laser light applied to the fundus of the eye to be examined follows the optical path of the irradiation optical system in the reverse direction, is reflected by the perforated mirror 2, and is bent downward. The pupil position of the eye to be examined and the opening of the perforated mirror 2 are conjugated by the lens 3. The reflected light reflected by the perforated mirror 2 passes through the lens 11 and is focused on the pinhole of the pinhole plate 12. The reflected light focused by the pinhole is received by the light receiving element 14 through the lens 13. A photographing optical system (light receiving optical system) is formed by these optical members. A confocal optical system 50 is formed by optical members included in the irradiation optical system and the photographing optical system.

  FIG. 2 is a schematic external view when the periphery of the polygon mirror 7 according to the present embodiment is viewed obliquely from above. Reference numeral 20 denotes a storage case for storing the polygon mirror 7 in a rotatable manner. Reference numeral 21 denotes an opening formed in the storage case 20 for allowing laser light to enter and exit the polygon mirror 7. Reference numeral 22 denotes a transparent member (for example, a resin such as a glass plate or acrylic) that closes the opening 21 and transmits laser light, and covers the opening 21 and serves as a protective window. Note that an antireflection film for increasing the transmittance of the laser light is provided on the front surface and the back surface of the transparent member 22. R1 is the rotation axis of the polygon mirror 7. In the present embodiment, a rectangular glass plate extending in the rotation direction of the polygon mirror 7 (perpendicular to the rotation axis R1) is used as the transparent member 22. The polygon mirror 7 is housed in the housing case 20 in a state where it is placed on a table not shown, and is almost sealed from the outside.

  FIG. 3 is a cross-sectional view in the longitudinal direction of the transparent member 22 according to the present embodiment. As shown in FIG. 3, the cross-sectional shape in the longitudinal direction of the transparent member 22 is such that the thickness of the transparent member 22 gradually changes in the longitudinal direction. That is, the transparent member 22 is formed such that the extended surface between the front surface and the back surface intersects at a predetermined angle (for example, 30 minutes). In this case, as the inclination α (wedge angle) of the back surface with respect to the front surface of the transparent member 22, the fundus reflection light component that is reflected by the polygon mirror 7 and passes through the transparent member 22 as it is toward the light receiving element 14 is reflected by the polygon mirror 7. The interference fringes generated by the interference with the fundus reflected light component that is reflected once on the front surface and the back surface of the transparent member 22 and that travels toward the light receiving element 14 need not affect the fundus image, and are inclined more than necessary. There is no need to increase the angle. This is because the refraction of laser light can become a problem when the tilt angle is increased.

  FIG. 4 is a diagram showing the positional relationship between the transparent member 22 and the polygon mirror 7 according to this embodiment. As shown in FIG. 4, the transparent member 22 is provided so that the front surface and the back surface thereof are inclined (not parallel) with respect to the rotation axis R1. In this case, the inclination angle β of the transparent member 22 with respect to the rotation axis R1 is caused by laser light irradiation to optical members (for example, the mirror 4, the mirror 5, the concave mirror 6 and the like) provided in the optical system inside the apparatus. As long as the scattered light is reflected by the front and back surfaces of the transparent member 22 and is not received by the light receiving element 14, it is not necessary to increase the tilt angle more than necessary. This is because increasing the inclination angle leads to an increase in the arrangement space of the transparent member 22. Therefore, the upper limit of the tilt angle includes a state in which the front and back surfaces are tilted by about 45 degrees with respect to the rotation axis R1.

  A pair of left and right inclined portions 20a extending in the direction of the polygon mirror 7 is formed in the window frame portion of the storage case 20 to which the transparent member 22 is attached. The inclined portion 20a is designed so that the transparent member 22 is arranged at an inclination angle β with respect to the rotation axis R1, and the end portion of the inclined portion 20a and the transparent member 22 are interposed with an adhesive or the like. Are joined. Thereby, while being able to maintain the sealing state inside the storage case 20, the transparent member 22 can be attached to the storage case 20 compactly.

  FIG. 5 is a block diagram showing a control system of the scanning laser ophthalmoscope according to the present embodiment. Reference numeral 30 denotes a control unit that controls the entire apparatus. The control unit 30 includes a laser light source 1, a light receiving element 14, a driving unit 31 for driving the mirrors 7 and 9, a driving unit 36 for moving the mirrors 4 and 5 in the optical axis direction, and used for diopter correction. A control unit 32 having a diopter correction knob and the like, and an image processing unit 33 for forming an image of the fundus of the eye to be examined based on a signal received by the light receiving element 14 are connected. Reference numeral 34 denotes a monitor on which a fundus image formed by the image processing unit 33 is displayed. Reference numeral 35 denotes a storage unit (memory) for storing various information.

  A case where the fundus of the eye to be examined is photographed in the apparatus having the above configuration will be described. Here, the examiner moves the apparatus using a joystick (not shown) and performs alignment so that the fundus of the eye to be examined is irradiated with laser light and a desired image is displayed on the monitor 34. When the fundus image of the eye to be examined appears on the monitor 34, the focus adjustment of the fundus image is performed using the control unit 32.

  Here, the control unit 30 drives the driving means 31 to operate the polygon mirror 7 and the galvanometer mirror 9 to scan the laser light two-dimensionally on the fundus of the eye to be examined. Thereby, the fundus reflection light corresponding to the scanning position of the laser beam on the eye fundus is sequentially received by the light receiving element 14. Here, the image processing unit 33 constructs one fundus image (an image for one frame) based on the light reception signal sequentially output from the light receiving element 14 and displays the fundus image on the monitor 34. Then, by repeating the above operation, the fundus of the eye to be examined can be observed in real time as a moving image on the screen of the monitor 34. Further, the control unit 30 drives the driving unit 36 based on the operation signal from the control unit 32 to move the mirrors 4 and 5 in the optical axis direction. Note that when an imaging switch (not shown) is pressed by the examiner, the fundus image captured as described above is stored in the storage unit 35.

  With the above configuration, the problem of noise and dust caused by the polygon mirror 7 can be avoided, interference fringes reflected in the fundus image can be removed, and a fundus image with less noise light can be obtained. Further, it is possible to remove the reflection of noise light caused by the scattered light generated by the irradiation of the laser beam to the optical member provided in the optical system inside the apparatus being reflected by the front and back surfaces of the transparent member 22.

  Further, in the above description, the configuration in which the transparent member 22 is inclined with respect to the rotation axis R1 can remove the reflection of scattered light without taking a large arrangement space of the transparent member 22. it can. However, the present invention is not limited to this, and may be provided so as to be inclined with respect to the light receiving optical axis L1 of the light receiving optical system (for example, the transparent member 22 is inclined with respect to the left-right direction). The light receiving (imaging) optical axis L1 in the present embodiment is an optical axis formed by the laser light reflected by the polygon mirror 7, and the optical axis of the laser light corresponding to the center of the scanning range by the polygon mirror 7. Say.

It is the figure which showed the optical system of the scanning laser ophthalmoscope which concerns on this embodiment. It is a schematic external view when the polygon mirror periphery which concerns on this embodiment is seen from diagonally upward. It is sectional drawing in the longitudinal direction of the transparent member which concerns on this embodiment. It is a figure shown about the positional relationship of the transparent member and polygon mirror which concern on this embodiment. It is the block diagram which showed the control system of the scanning laser ophthalmoscope which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 7 Polygon mirror 9 Galvano mirror 14 Light receiving element 20 Storage case 21 Opening part 22 Transparent member 50 Confocal optical system

Claims (3)

An irradiation optical system for irradiating the eye fundus with a laser beam emitted from a laser light source, comprising a polygon mirror and a galvanometer mirror for two-dimensionally scanning the laser beam emitted from the laser light source on the fundus In a scanning laser ophthalmoscope for photographing a fundus image of an eye to be examined, including an irradiation optical system having a scanning means, and a light receiving optical system for receiving laser light emitted to the fundus of the eye to be examined by a light receiving element.
A storage case for storing the polygon mirror therein, and a storage case having an opening for allowing laser light to enter and exit the polygon mirror;
A scanning member comprising a transparent member that closes the opening and transmits a laser beam, the transparent member being formed such that an extended surface of the front surface and the back surface of the transparent member intersect at a predetermined angle. Laser ophthalmoscope. The scanning laser ophthalmoscope according to claim 1,
The scanning laser opthalmoscope, wherein the transparent member is provided so as to be inclined with respect to a light receiving optical axis of the light receiving optical system. The scanning laser ophthalmoscope according to claim 2,
The scanning laser ophthalmoscope according to claim 1, wherein the transparent member is provided so as to be inclined with respect to a rotation axis of the rotary polygon mirror.

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