KR20230070931A - Illumination and image forming apparatus for fundus image and method thereof - Google Patents

Abstract

The present invention is an objective lens installed on one open end of the main body; a lens unit installed behind the objective lens to focus light; an image sensor into which the light focused by the lens unit is incident; a plurality of light sources disposed around an optical axis and each installed so as to be axially symmetrical with respect to the optical axis; an operating unit for selecting an operation; and sequentially driving the plurality of light sources by manipulation of the control unit, obtaining an image for each of the sequentially driven light sources from the image sensor, and summing the images to remove stray light due to reflection of the cornea or crystalline lens It relates to an eye fundus camera for retinal image observation and a lighting and image processing method using the same.
According to the present invention, even when the alignment of the optical axis and the maintenance of the working distance are easily shaken due to the limitation of being portable in the fundus camera, it has an effect of improving usability so that a wide-field retinal image can be accurately and easily obtained.

Description

Fundus camera for retinal image observation and illumination and image processing method using the same {Illumination and image forming apparatus for fundus image and method thereof}

The present invention relates to a fundus camera for retinal image observation and a lighting and image processing method using the same, and more particularly, to a fundus camera for retinal image observation that improves usability so that a wide-field retinal image can be accurately and easily obtained. And it relates to a lighting and image processing method using the same.

There are photoreceptors in the retina of the eye that allow us to perceive light. Light is recognized in the photoreceptors, and information is transmitted to the brain through the optic nerve to observe objects. Therefore, abnormalities can be observed through observation of the retina. The retina of the eye can be observed through the pupil, and since the inside of the eye is dark, separate lighting is required.

An ophthalmoscope or fundus camera is a device for observing the retina of the eye and is composed of a lighting unit for illuminating the retina and an imaging unit for observing an image of the retina.

Referring to FIG. 1, in a conventional fundus camera, an image of the retina is formed in the middle by an objective lens L1, and this image is inverted and formed on a CMOS, CCD, or film by a lens L2, This path is called an image formation part. In order to observe the retina of the eye, light must shine through the pupil. A conventional fundus camera adjusts to focus on the retina using near infrared rays emitted from an IR LED, and obtains a picture or image by illuminating white light emitted from a snapshot LED.

Since the human eye cannot see near-infrared rays, the size of the pupil does not change when observing with near-infrared rays, so near-infrared rays are used to adjust the retinal observation area or focus. The light from NIR LED or white LED goes directly to the objective lens, or goes to the objective lens through a beamsplitter or a holed mirror, and the light passing through the objective lens is directed to the pupil of the human eye. It is focused so that the retina can be observed widely. This path is called the lighting section.

Light used for retinal illumination is also reflected from the cornea and lens of the eye. In particular, since the light reflected from the cornea is higher than the reflectance of the retina, observation on the retina is hindered. The reflectance of the retina is slightly different for each region of the retina, but is approximately within 2% in the visible light region (see FIG. 2).

In addition to the retina, a method commonly used to prevent light reflected from the cornea or lens from interfering with the formation of a clear retinal image is a geometric pupil separation in which the area used for image formation and the area used for illumination do not overlap in the pupil of the eye ( geometric pupil separation). Geometric pupil separation means that the path of the imaging beam and the path of the illumination beam must be spatially separated at all points where scattering and reflection can occur. will be. As a method of implementing this concretely, there are ring illumination (see FIG. 3) and off axis illumination (see FIG. 4).

Ring illumination is a method used in most fundus cameras, and is a method in which illumination is illuminated in a ring form on the cornea or lens, preventing reflected light from entering the observer's eye or the sensor of the camera. This has the advantage that it can illuminate a wide viewing angle of 40 degrees or more, but has the disadvantage that the lighting unit is long and complicated.

Off-axis illumination is a method suitable for small instruments such as portable ophthalmoscopes or binocular indirect ophthalmoscopes, and makes the illumination area in the pupil separate from the imaging beam in a simple circle rather than a ring shape. This has the advantage that the lighting part is short and simple, and does not require the use of a mydriatic agent, but most of them have a narrow viewing angle of about 25 degrees, and the optical axis of illumination and optical axis of imaging are different, so the ophthalmoscope or fundus camera needs to be rotated differently from the optical axis of the human eye. there is. 5 shows an optical axis mismatch due to off-axis illumination.

As a prior art, Korean Patent Registration No. 10-2140486, "Illumination device for retinal observation and fundus camera having the same," arranges lights that are axially symmetrical with respect to the optical axis, and takes pictures at the part where the lights overlap to match the optical axes and improved to maintain the distance between the eye and the fundus camera (eye spot distance) to fit the design.

However, despite these improvements, the prior art does not maintain stable postures of the patient and the observer when used portablely, so that when the optical axis or focal distance does not match during measurement, light reflected on the cornea or lens enters There is an inconvenience that the retinal image is obscured (see FIG. 6).

In order to solve the problems of the prior art as described above, the present invention is an eye fundus camera or ophthalmoscope due to portable limitations, even when the alignment of the optical axis and the maintenance of the working distance are easy to shake little by little, the retinal image of the wide field is accurately and easily The purpose is to improve the usability so that you can get it.

Other objects of the present invention will be easily understood through the description of the following embodiments.

In order to achieve the above object, according to one aspect of the present invention, an objective lens installed on one open end of the main body; a lens unit installed behind the objective lens to focus light; an image sensor into which the light focused by the lens unit is incident; a plurality of light sources disposed around an optical axis, each of which is axially symmetrical with respect to the optical axis; an operating unit for selecting an operation; and sequentially driving the plurality of light sources by manipulation of the control unit, obtaining an image for each of the sequentially driven light sources from the image sensor, and summing the images to remove stray light due to reflection of the cornea or crystalline lens There is provided an eye fundus camera for retinal image observation including; an image generating unit for generating a retinal image.

The light source includes first and second light sources that are axially symmetrical at 180 degrees with respect to the optical axis, and the image generating unit turns on the first light source by manipulation of the control unit, and the image sensor Stores a first image obtained by, turns off the first light source, turns on the second light source, stores a second image obtained by the image sensor, and and removing the stray light present in each of the second images, and generating a single image on the retina by merging the first and second images from which the stray light is removed.

According to another aspect of the present invention, an objective lens installed on one open end of the main body, a lens unit installed at the rear of the objective lens for focusing light, and an image sensor into which light focused by the lens unit is incident In the illumination and image processing method for retinal image observation using an eye fundus camera including a plurality of light sources arranged around an optical axis and each installed so as to be axially symmetric with respect to the optical axis, the plurality of light sources are sequentially driven, but images for each of the sequentially driven light sources are obtained from the image sensor, and the images are combined to remove stray light due to reflection of the cornea or lens to generate a retinal image. Lighting and image processing methods are provided for

turning on the first light source among the plurality of light sources including first and second light sources and storing a first image obtained by the image sensor; turning off the first light source, turning on the second light source, and storing a second image acquired by the image sensor; removing the miscellaneous light existing in each of the first and second images; and merging the first and second images from which the stray light is removed to generate a single image on the retina.

According to the fundus camera for retinal image observation and the lighting and image processing method using the same according to the present invention, even when the coincidence of the optical axis and the maintenance of the working distance are easy to shake slightly due to the portable limitation of the fundus camera or ophthalmoscope, the wide field of view It has the effect of improving the convenience of use so that the retinal image can be accurately and easily obtained.

1 shows the structure of a fundus camera according to the prior art.
Figure 2 shows the reflectance of the retina according to the wavelength.
3 shows ring illumination in a conventional fundus camera.
4 shows off-axis illumination in a conventional fundus camera.
5 shows a mismatch between an imaging optical axis and an illumination optical axis due to off-axis lighting.
FIG. 6 is a retinal image in the case where the ocular distances do not match or the optical axes do not match in the conventional fundus camera illumination system, showing stray light (indicated by a red line).
7 is a configuration diagram showing an eye fundus camera for retinal image observation according to an embodiment of the present invention.
8 is a conceptual diagram illustrating manipulation of a light source in the fundus camera for retinal image observation according to an embodiment of the present invention.
9 is a diagram for explaining an illumination and image processing method for retinal image observation according to an embodiment of the present invention.

Since the present invention can make various changes and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and should be understood in such a way as to include all changes, equivalents, or substitutes included in the technical spirit and scope of the present invention, and may be modified in various other forms. However, the scope of the present invention is not limited to the following examples.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings, the same reference numerals will be assigned to the same or corresponding components regardless of reference numerals, and redundant descriptions thereof will be omitted.

7 is a configuration diagram showing an eye fundus camera for retinal image observation according to an embodiment of the present invention.

Referring to FIG. 7 , the fundus camera 100 for retinal image observation according to an embodiment of the present invention includes an objective lens 120, a lens unit 130, an image sensor 150, light sources 171 and 172, and a manipulation unit ( 110) and an image generator 180.

The objective lens 120 is installed on one open end of the main body, and is located on the side of the eye 10 to be inspected, so that the light of the lighting device is irradiated to the eye 10. The objective lens 120 uses an aspheric lens and a lens processed to fit the shape of glass. When a mold such as a plastic lens or a glass mold is used, reflected light increases due to birefringence of the lens generated by the manufacturing process, obstructing retinal image observation. The shorter the focal length of the objective lens 120, the wider the viewing angle. On the other hand, since the distance between the eye and the objective lens 120 is shortened, the subject may feel uncomfortable. In this embodiment, the focal length of the objective lens 120 may be set to about 22 mm (45, 45 Diopter) so that the focal length is secured at 25 mm or more and the viewing angle is 45 degrees or more. In normal vision, light departing from the retina becomes parallel light when it passes through the cornea.

The size of the image by the objective lens 120 can be expressed as in Equation 1 below.

Here, f _eye is the focal length of the eye, f _O is the focal length of the objective lens 120, S _o2 is the object distance of the lens unit 130, and S _i2 is the image distance of the lens unit 130.

On the other hand, the main body has an inner space with one end opened, and a cap for attaching and detaching the objective lens 120 may be screwed to one open side, and a fixed housing for installing the lens unit 130 on the inside It may be fixed by bolts or the like.

The lens unit 130 is installed to focus light in the inner space of the body so as to be located behind the objective lens 120, and focuses the light coming from the eye 10 to be irradiated to the image sensor 150. Here, at least one lens unit 130 may be formed of a lens group as in the present embodiment by being formed of at least one lens unit 130 for convergence of light.

The image sensor 150 may obtain an image of the eye by allowing light focused by the lens unit 130 to be incident, and various sensors may be used for image acquisition, including, for example, CMOS or CCD. . In this embodiment, the image sensor 150 may obtain an image of the eye by allowing light focused by the lens unit 130 and passing through the prism 140 to be incident.

The prism 140 may be installed in the inner space of the main body so that light focused by the lens unit 130 passes therethrough. Therefore, the prism 140 changes the optical path so that the eye gazes at the gaze target 160, and the light emitted from the eye reaches the image sensor 150 through the objective lens 120 and the lens unit 130. can be investigated.

The gaze target 160 is installed in the inner space of the main body so that the eye gazes at one side of the prism 140, and the image sensor 150 and the gaze target 160 form an angle of 90 degrees with respect to the prism 140. It can be. Since the angle of view of the fundus camera 100 for retinal image observation is constant, it is difficult to observe a sufficiently wide area at once. In order to overcome this disadvantage, the observer can observe another area by turning his or her eyes away. The gaze target 160 is made for this purpose. The gaze target 160 is disposed on the prism 140 in front of the image sensor 150, and changes the path of light using the prism 140. The gaze target 160 may include a plurality of LEDs, and low power display LEDs may be used as the LEDs.

The prism 140 may use a method of polarization separation by a polarization beam splitter coating. In this way, as in the present embodiment, insufficient performance of the polarizers 220 and 230 used in the fundus camera 100 can be compensated for.

The light sources 171 and 172 are lighting devices used to provide illumination to devices for observing the retina, and are configured to be used for illumination of the fundus camera 100 for retinal image observation as well as illumination of the ophthalmoscope. may be A plurality of light sources 171 and 172 are disposed around the optical axis, and each is installed so as to be axially symmetrical with respect to the optical axis. Therefore, the other light source 172 is installed to be axially symmetrical with respect to the light source 171 eccentric to the optical axis, so that the illumination optical axis and the imaging optical axis can be aligned. Here, the meaning of axisymmetric is generally known, and may mean symmetry in which the same shape as the original can be maintained when rotated by an arbitrary angle around a certain axis.

The light sources 171 and 172 are arranged so that the irradiated light is focused on the pupil of the human eye by the objective lens 120, and a lamp or LED can be used. In the case of the LED, since the light emitting area is larger than 1mm, light is emitted in front of the LED. You can place holes to control the area. The polarizers 220 and 230 to be described later may be disposed so that the polarization of light emitted from the light sources 171 and 172 and the polarization of the imaging optical system reflected from the retina are 90 degrees apart.

In this embodiment, the light sources 171 and 172 may include first and second light sources 171 and 172 that are axially symmetrical at 180 degrees with respect to the optical axis. Here, the axial symmetry of 180 degrees may mean having symmetry such that the original arrangement of the light sources 171 and 172 is maintained when rotated by 180 degrees about the optical axis. Therefore, by disposing the first and second light sources 171 and 172 as in the present embodiment, the imaging pupil is located at the center of the pupil, and the light sources 171 and 172 are disposed at 180 degrees around the imaging pupil.

In this embodiment, the light sources 171 and 172 may be made of white LEDs, but are not limited thereto, and each may be made of a white LED and a near-infrared LED, and various other light emitting elements may be used. In the case of the fundus camera 100 for retinal image observation, it may be adjusted to focus on the retina using Near Infrared emitted from the near infrared LED, and a photo or image may be obtained by illuminating white light emitted from the white LED. can be made Since the human eye cannot see near-infrared rays, the size of the pupil does not change when observing with near-infrared rays, so near-infrared rays are used to adjust the retinal observation area or focus. As such, since the human eye responds only to visible light, techniques using near-infrared rays are often used to adjust the focus. A retinal photograph may be taken after focusing using near-infrared rays, or a photograph may be taken by irradiating visible light in a state in which a focal position is found. When taking a picture with visible light, it is possible to take a picture by irradiating visible light in a strong state for a short period of time. When taking a picture with visible light, the size of the pupil decreases after the picture is taken because strong light shines for a short time. In general, the focus is adjusted using the lens unit 130 or the image sensor 150. In addition, in order to reduce the size of the fundus camera 100 for overall retinal image observation, a relatively small-sized LED may be disposed in a reserve on an optical path without using a beam splitter or a mirror.

In addition, the fundus camera 100 for retinal image observation according to an embodiment of the present invention may further include a mask 190, wherein the mask 190 has grooves or holes to forwardly expose each of the light sources 171 and 172. This formation allows light emitted from the light sources 171 and 172 to be radiated in a desired direction without scattering, and noise generation due to dispersion of light can be minimized. In addition, the mask 190 controls the size of the light emitting area of the light sources 171 and 172. Through the mask 190, the light for image formation passes through the hole in the center and partially blocks the area exiting from the bottom of the light sources 171 and 172. Thus, it is possible to prevent the pupil of the eye from invading the pupil of the imaging system. Meanwhile, a diffuser together with the mask 190 may be disposed in front of the light sources 171 and 172 .

An aperture 210 and a polarizing plate 220 may be installed on an optical axis between the light sources 171 and 172 and the lens unit 130, and the polarizing plate 230 may be installed in front of the light sources 171 and 172. Here, the diaphragm 210 is a disc-shaped device that controls the amount of light passing through by adjusting the size of the hole. The aperture 210 may be set in front of the lens unit 130 in the imaging system.

The larger the aperture 210 is, the brighter and clearer the image can be made, but on the other hand, light reflected from the cornea or the objective lens 120 may enter, so an appropriate size must be selected. The polarizers 220 and 230 are devices that obtain linearly polarized light by using the property that optical optical isomers change the color of polarized transmitted light depending on the direction. The light provided from the light sources 171 and 172 uses only one polarized light when it goes toward the eye by the polarizer 230 located in front of the light sources 171 and 172, and when it hits the retina, the polarizer 220 rotated 90 degrees is disposed. Therefore, it blocks the light of the same polarization as the polarized light irradiated to the retina, and transmits only the light of which the polarization is returned by birefringence. The polarizers 220 and 230 block light reflected from the objective lens 120 or the cornea. In general, light reflected from the objective lens 120 or the surface of the cornea maintains incident polarization. The polarization direction of light passing through the cornea and entering the retina is changed by birefringence. Of this light, only the polarized light 90 degrees different from the polarized light emitted from the light source is used for image formation.

The control unit 110 is an operation signal input device such as a switch, button, or touch panel for selecting an operation, for example, on or off, and is disposed on an outer surface of a main body (not shown) to enable operation. can

The image generator 180 sequentially drives the plurality of light sources 171 and 172 by manipulation of the control unit 110, and acquires images for each of the sequentially driven light sources 171 and 172 from the image sensor 150, The images are merged to eliminate stray light due to reflection from the cornea or lens to create a retinal image.

As shown in FIG. 8 , the image generator 180 turns on the first light source 171 by manipulating the control unit 110, stores the first image obtained by the image sensor 150, and , the first light source 171 is turned off, the second light source 172 is turned on, and the second image obtained by the image sensor 150 is stored, and the first and second images are respectively Stranded light due to reflection from the cornea or lens may be removed, and a single image on the retina may be generated by merging first and second images from which the scattered light due to reflection from the cornea or lens is removed.

9 is a diagram for explaining an illumination and image processing method for retinal image observation according to an embodiment of the present invention.

Referring to the lighting and image processing method for retinal image observation according to an embodiment of the present invention, the fundus camera 100 for retinal image observation according to an embodiment of the present invention described above, that is, the open end of the main body An installed objective lens 120, a lens unit 130 installed behind the objective lens 120 for focusing light, an image sensor 150 into which light focused by the lens unit 130 is incident, and an optical axis An illumination and image processing method for retinal image observation using an eye fundus camera 100 including light sources 171 and 172 arranged around a periphery and each installed so as to be axially symmetric with respect to an optical axis, wherein a plurality of The light sources 171 and 172 are sequentially driven, and images for each of the sequentially driven light sources 171 and 172 are obtained from the image sensor 150, and the images are combined to remove stray light due to reflection of the cornea or lens to form a retinal image. can be created. Meanwhile, since the fundus camera 100 for retinal image observation according to an embodiment of the present invention has already been described in detail, overlapping descriptions will be omitted.

To illustrate this more specifically, as shown in (a) of FIG. 9, the first light source 171 is turned on among the plurality of light sources 171 and 172 composed of the first and second light sources 171 and 172, and the image sensor Storing the first image obtained by 150, turning off the first light source 171 and turning on the second light source 172, as shown in (b) of FIG. Stores the second image acquired by the image sensor 150, removes the scattered light due to the reflection of the cornea or lens, which exists for each of the first and second images, and as shown in (c) of FIG. 9, the cornea A single image on the retina is created by merging the first and second images from which stray light due to reflection of the lens or lens is removed. When synthesizing the first and second images, blood vessels and optic nerve discs may be matched.

According to the present invention, a retina image is created by sequentially driving a plurality of light sources 171 and 172, sequentially acquiring images accordingly, and combining images from which light reflected from the cornea or lens is removed. Therefore, a method of arranging the light sources 171 and 172 so as to be symmetrical (axially symmetrical) at one or more locations while basically maintaining the form of off-axis lighting is applied. Accordingly, it is possible to provide uniform lighting comparable to ring lighting while simplifying the structure of lighting corresponding to the light sources 171 and 172 . In addition, a retinal image is obtained in a section where the illumination by two or more light sources 171 and 172 overlaps, so that the optical axis and ocular distance can be easily guided.

When a single white LED is used as illumination, miscellaneous light reflected from the cornea or crystalline lens tends to be biased to one side of the image when the optical axis or focal length is slightly misaligned. Therefore, as in the present invention, if the scattered light corresponding to the reflected light is removed and the remaining images are combined to create one image, the scattered light can be perfectly controlled, and more information can be obtained from the overlapping images. For example, in the conventional method, if the flash duration corresponding to the light sources 171 and 172 is 200 ms and there are two white LEDs, each flash duration can be alternately driven within 100 ms. All images are obtained within 200 ms, and since the interval is very short, there is almost no eye movement, so each image can obtain an almost identical retinal image. In addition, even a slight deviation can be corrected using a general image stitching method.

This method can be applied to fundus cameras of various configurations using two or more light sources 171 and 172, and the light sources 171 and 172 are not necessarily white LEDs, but individual RGB LEDs, fluorescent LEDs, or IR LEDs. The same can be applied to obtaining an image.

According to the fundus camera for retinal image observation and the lighting and image processing method using the same according to the present invention, even when the alignment of the optical axis and the maintenance of the working distance are easily shaken little by little due to the limitations of being portable in the fundus camera or ophthalmoscope, Convenience of use can be improved so that a wide-field retinal image can be accurately and easily obtained.

As described above, the present invention has been described with reference to the accompanying drawings, but various modifications and variations can be made without departing from the technical spirit of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, and should be defined by not only the claims to be described later, but also those equivalent to these claims.

110: control unit 120: objective lens
130: lens unit 140: prism
150: image sensor 160: gaze target
171: first light source 172: second light source
180: image generator 190: mask
210: Aperture 220, 230: Polarizer
240: memory unit 250: power supply unit

Claims (4)

An objective lens installed on one open end of the main body;
a lens unit installed behind the objective lens to focus light;
an image sensor into which light focused by the lens unit is incident;
a plurality of light sources disposed around an optical axis and each installed so as to be axially symmetrical with respect to the optical axis;
an operating unit for selecting an operation; and
By operating the control unit, the plurality of light sources are sequentially driven, and images for each of the sequentially driven light sources are obtained from the image sensor, and the images are combined to remove stray light due to reflection of the cornea or crystalline lens. an image generator for generating an image;
Including, fundus camera for retinal image observation. The method of claim 1,
The light source,
It consists of first and second light sources that form an axial symmetry of 180 degrees with respect to the optical axis,
The image generator,
By manipulation of the control unit, the first light source is turned on, the first image acquired by the image sensor is stored, the first light source is turned off, and the second light source is turned on ( on), stores the second image acquired by the image sensor, removes the scattered light existing for each of the first and second images, and merges the first and second images from which the scattered light has been removed. A fundus camera for retinal imaging, allowing the creation of a single image on the retina. An objective lens installed at one open end of the main body, a lens unit installed behind the objective lens for focusing light, and an image sensor into which the light focused by the lens unit is incident, arranged in plural numbers around the optical axis. In the illumination and image processing method for retinal image observation using an eye fundus camera including light sources, each of which is installed to be axially symmetrical with respect to the optical axis,
Sequentially driving the plurality of light sources, acquiring images of each of the sequentially driven light sources from the image sensor, and combining the images to remove stray light due to reflection of the cornea or lens to generate a retinal image, Illumination and image processing method for retinal image observation. The method of claim 3,
turning on the first light source among the plurality of light sources including first and second light sources and storing a first image obtained by the image sensor;
turning off the first light source, turning on the second light source, and storing a second image acquired by the image sensor;
removing the miscellaneous light existing in each of the first and second images; and
merging the first and second images from which the stray light is removed to generate a single image on the retina;
Including, illumination and image processing method for retinal image observation.

Images