JP2927505B2 - Fundus camera and image display method thereof - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fundus camera suitable for use in analyzing polarization characteristics of a fundus anatomy.

(Prior art) Conventionally, it has been known that the fundus structure, particularly the optic nerve fiber and the macula, have polarization characteristics. If the optic nerve fiber has a defect, the polarization characteristic disappears at the defect. Have been found. Also, in certain fundus diseases,
It is said that the polarization characteristics of the macula also disappear. Therefore,
The polarization characteristics of the fundus anatomy can be an important factor in analyzing fundus disease.

(Problems to be Solved by the Invention) By the way, conventionally, there is a fundus camera capable of performing normal photographing using a black-and-white film and a color film, visible fluorescence photographing, and the like. It was not preferred for use in analyzing the polarization properties of the structure.

Therefore, an object of the present invention is to provide a fundus camera suitable for use in analyzing the polarization characteristics of the anatomy of the fundus, and to provide an image display method thereof.

(Means for Solving the Problems) In a fundus camera according to claim 1 of the present invention, an illumination optical system is provided with an illumination system polarizing element for linearly polarizing illumination light for fundus illumination, and a biological structure of the fundus is provided. In the reflected light having the polarization characteristics based on the imaging system, an imaging system polarizing element that transmits a polarization component that is substantially orthogonal to the polarization component transmitted through the illumination system polarization element is provided in the imaging optical system. The element and the imaging system polarizing element are rotated around the optical axis of each of the optical systems while maintaining a relationship of transmitting polarized light components that are substantially orthogonal to each other, and a fundus image based on polarized illumination light at each predetermined angle is captured. It is characterized by doing.

In a fundus camera according to a second aspect of the present invention, an illumination optical system is provided with an illumination system polarizing element for linearly polarizing illumination light for fundus illumination, and reflected light including polarization characteristics based on a biological structure of the fundus. Among them, an imaging system polarizing element that transmits a polarization component substantially parallel to a polarization component that transmits the illumination system polarization element is provided in an imaging optical system, and the illumination system polarization element and the imaging system polarization element are provided. The optical system is characterized in that it is rotated around the optical axis of each of the optical systems while maintaining a relationship of transmitting polarized components that are substantially parallel to each other, thereby capturing a fundus image based on polarized illumination light at each predetermined angle.

According to a third aspect of the present invention, there is provided an image display method, wherein the fundus camera according to any one of the first to third aspects is used to image a fundus at each rotation angle of a polarizing element. And obtaining a plurality of fundus images, dividing the fundus into a plurality of fundus parts, comparing the corresponding fundus parts for the entire fundus image with each other, and determining the brightest imaged fundus part for each fundus part. Then, the operation of cutting out the fundus image including the brightest imaged fundus region as the image piece with the brightest imaged fundus region is executed for all fundus regions, and the fundus region imaged brightest for each fundus region Is characterized in that a fundus image is reconstructed and displayed by combining image fragments consisting of

The image display method according to the fourth aspect of the present invention is the third aspect of the present invention.
Is performed, and a fundus image is reconstructed and displayed by combining the image pieces of the fundus part imaged darkest for each fundus part.

(Operation) According to the fundus camera according to the present invention, each of the optical system is maintained while maintaining the relationship between the illumination system polarizing element and the imaging system polarizing element that transmits polarized components that are substantially orthogonal to each other (or substantially parallel to each other). When the fundus image is imaged while being rotated about the optical axis, a fundus image based on the polarized illumination light at each predetermined angle is obtained.

Further, according to the image display method according to the present invention, the polarization preservation of each part of the fundus can be easily and finely grasped simply by looking at one image without comparing many images. it can.

Further, by displaying the reconstructed subtraction image of the fundus image, the polarization reflection characteristics of the fundus can be more clearly displayed.

(Example) Hereinafter, an example of a fundus camera according to the present invention will be described with reference to the drawings.

In FIG. 1, 1 is an illumination optical system, and 2 is a photographing optical system. The illumination optical system 1 has a flash tube 3 and a halogen lamp 4, and the light sources 3, 4 are relayed by condenser lenses 5, 6 near the ring-shaped aperture X, respectively.

In the vicinity of the ring-shaped stop X, an illumination system polarizing element 8 is provided.
And a visible light shutter including a visible light cut filter 9 is provided in the vicinity of the illumination system polarizing element 8. The ring-shaped aperture X is relayed to the vicinity of the pupil of the eye 13 through a lens 10, a mirror 11, a lens 12, a perforated mirror 15, and an objective lens 14, similarly to a general fundus camera. The photographing optical system 2 includes an objective lens 14 facing the eye 13 to be inspected, a perforated mirror 15, a focusing lens 17, a relay lens 18, a quick return mirror 19, a CCD camera 20 as an image pickup tube, and a photographic film 21. Photographic film 21 and CCD camera 20
Is at a conjugate position with respect to the quick return mirror 19. The quick return mirror 19 is inserted into the optical path between the relay lens 18 and the CCD camera 20 as shown by a broken line when taking a photographic film, and is retracted from the optical path when observing or photographing with the CCD camera.

The reflected light from the fundus 23 is reflected by the objective lens 14 and the perforated mirror.
15 holes 24, shooting aperture Y, focusing lens 17, relay lens 18
Through the imaging surface 22 of the CCD camera 20, the imaging surface 22
A fundus image is formed in the image. The video output of the CCD camera 20 is input to a frame memory 25 shown in FIG. 2, and displayed on a monitor TV 26 via the frame memory 25. The alignment and focusing of the fundus image can be performed while observing the fundus image captured by the CCD camera 20 on the monitor TV 26. During this observation, the visible light shutter 9
It is needless to say that if the observation is performed using near-infrared light while closing the image, the burden on the subject is reduced.

A photographic system polarizing element 16 is provided between the photographic stop Y and the focusing lens 17. Illuminating polarizing element 8 as a polarizing element (polarizer) for extracting natural light as linearly polarized light
And the imaging system polarizing element 16 are rotated while maintaining the polarization transmission axis at a substantially parallel or substantially orthogonal relative angle. Which relative angle is selected is up to the operator and can be set in advance.

If the polarizing elements 8 and 16 are retracted out of the optical path, they can function as a normal fundus camera. However, in the case of polarized illumination, the illumination system polarizing element 8 is inserted into the optical path of the illumination optical system 1; The imaging system polarizing element 16 is inserted into the optical path of the imaging optical system 2.

The CCD camera 20 outputs a frame index signal for each frame, and the frame index signal is input to the polarization element rotation driving devices 29 and 30. The frame index signal is output 30 times per second, and the illumination system polarization element 8 and the imaging system polarization element 16 are feedback-controlled based on the rotation position detection signal and the frame index signal.

The frame memory 25 is reset on the basis of a photographing start signal by operating the photographing switch 28, and the fundus image can be stored in the frame memory 25. The video output of the CCD camera 20 is input to the frame memory 25 in real time, and a fundus image based on the illumination light is stored in the frame memory 25 at each predetermined angle around the optical axis.

The frame memory 25 is controlled by the host computer 31. When the display changeover switch 32 is operated, a fundus image at each angle around each optical axis is displayed on the monitor TV 26 during shooting, and the above-described fundus image alignment and focusing are performed. Becomes possible. The host computer 31 plays a role of displaying each fundus image on the monitor TV 26 without displacement, and is used for a process of cutting out the brightest image or the darkest image for each fundus region and reconstructing the image.

 Hereinafter, the procedure of the polarization imaging will be described.

In the present embodiment, since it is considered that a large number of fundus images at predetermined angles are obtained by a series of photographing, it is assumed that the subject's eye 13 is mydriatic. In such a case, it is sufficient to take an image at a predetermined angle at intervals of a time when the pupil opens to a size at which the image can be taken.

When the operator finishes the alignment of the fundus image and the alignment of the apparatus body with respect to the eye 13 and turns on the photographing button 28, the visible light cut filter 9 is retracted out of the optical path of the illumination optical system 1 by a photographing start signal, The rotation of the illumination system polarization element 8 and the imaging system polarization element 16 starts. After turning on the shooting button 28, each of the polarizing elements 8, 16
If it is desired to eliminate the time lag until the rotation starts, the polarization elements 8 and 16 may be constantly rotated.

On the other hand, the shooting start signal is sent to the host computer 31, and the host computer 31 sends the frame start signal to the frame memory.
At 25, image capture starts. This frame memory
The 25 has a frame rate of 30 frames / sec and can capture a large number of images. The host computer 31 operates the polarizing element driving units 16 and 29 in order to know the angle of the illumination system polarizing element 8 with respect to the eye 13 for each image frame.
Read the frame index while counting the pulses from.

A large number of images thus obtained are managed by the host computer 31 with the illumination polarization direction of each fundus image and the relative direction information of the two polarizing elements 8 and 16 added thereto. For example, if the illumination polarization direction is changed every 10 °, the required number of images is 18, so the time required for imaging is 0.6 seconds, and the subject's eye 13 moves during imaging because it is relatively short. Therefore, it is considered that the frequency of invalidating the photographing is low.

The CCD camera 20 may be monochrome or color, but if a color camera is used, R, G,
By changing the ratio of the B data, it is also possible to obtain an image in which red light, which is effective for observing the surface layer of the fundus, is suppressed. The illumination optical system 1 includes a red light suppression filter 27.
May be inserted.

Furthermore, with the visible light cut filter 9 inserted,
If the imaging device 20 having sensitivity to near-infrared light is used, polarization characteristics due to near-infrared light can also be captured. How to display the polarization characteristics of the fundus oculi 23 from the multiple images thus obtained will be described below.

In general, it is considered that surface reflection preserves the polarization direction, and when the polarization direction of reflected light is dispersed, light that has entered the inside of the object is randomly scattered and returned.
Further, it is considered that a scatterer having a regular internal structure having a certain directivity exhibits a dispersion of the polarization direction of the reflected light depending on the polarization direction of the incident light.

The structure of the fundus oculi 23 is considered to exhibit polarization characteristics in which the direction of the optic nerve fiber layer is the clearest, and if the direction changes due to degeneration of the fiber layer, the difference from the normal direction in the vicinity is the reflected light. It is thought that it appears in the fundus image as a polarization-dependent change. This polarization dependence eliminates the hassle of comparing many different fundus images as has been done conventionally, and the difference between the degenerate part and the normal part can be easily observed just by looking at one image It is an object of the present invention to obtain a fundus image as possible.

The brightly visible fundus region of the fundus image captured under the condition that the polarization directions of the illumination light and the imaging light are substantially orthogonal has a reflection characteristic that further disperses the polarization direction, while the fundus region that appears dark has a further polarization direction. It can be said that it has a reflection characteristic to preserve. The host computer 31 converts the relative positions of the fundus image group so that all fundus images overlap.

 Next, the host computer 31 performs the following processing.

A plurality of fundus images a ₁ as shown in FIG. 3 by imaging the fundus for each rotation angle of the polarizing element 8, 16, using a fundus camera ~
get a _n . Next, the fundus is divided into a plurality of fundus sites. For example, the fundus region is divided into m sections. Then, to determine the corresponding fundus portion are compared with each other brightest imaged fundus portion for each fundus portion for all the fundus image a ₁ ~a _n. For example, in the first section, the fundus region of a ₁₁ is the brightest, and similarly, in the second section, a ₃₂ ,
Assume that the third section is a ₄₃ , the fourth section is a ₁₄ , the fifth section is a _n5 , and so on. Next, the brightest imaged fundus sites a ₁₁ , a ₃₂ , a ₄₃ , a ₁₄ , a _n5 ,
... executed for all of the fundus portion (m bits) fundus image a ₁ including the most brightly imaged fundus portion as an image _{piece, a 3, a 4, a} n, a work cut from ... to. Then, a single fundus image is reconstructed and displayed by combining m pieces of images a ₁₁ , a ₃₂ , a ₄₃ , a ₁₄ , an ₅ ,... I do.

In one fundus image obtained in this way, a fundus part that looks brighter has larger polarization dispersion characteristics, and a fundus part that looks darker has more polarization preservation. This fundus image reflects the difference in the reflectance of each fundus region, but if the difference is recognized, only by looking at a single fundus image obtained in this way, the abnormal region and the abnormal region Can be distinguished from the site. Further, in the fundus image reconstruction, if the adoption criteria of the image piece is changed to `` selection of the darkest photographed image '' and adopted, and a reconstructed fundus image and a subtraction image of the reconstructed image are obtained. It is possible to know the magnitude of the change in the polarization dispersion characteristics. That is, the brighter fundus part of the subtraction image is a fundus part whose polarization dispersion characteristic is more strongly dependent on the illumination polarization direction, and the fundus part that looks darker is a fundus part whose direction dependency is smaller. . In this subtraction image, the difference in reflectance for each fundus site has been cancelled, and only the polarization direction dependence appears. If such processing is performed, even if a slight discontinuity occurs in the fundus region exhibiting a continuous direction change such as the running of the optic nerve fiber, the difference will appear in the fundus image. Would.

On the other hand, for a series of fundus images captured under the condition that the illumination polarization direction and the imaging system transmission polarization direction are substantially parallel, when three types of reconstructed fundus images are obtained by the same method as the above-described means, , Indicating the preservability of incident polarized light.

Among the fundus images reconstructed by collecting the brightest image pieces, a fundus portion that looks bright means that the polarization preservation is large. The fundus image reconstructed by collecting the darkest pixel pieces obtained by the substantially orthogonal polarizing elements 8 and 16 is also
It is clear that the lightness and darkness are opposite, but also indicate that the polarization preservation is large.However, considering that the gradation of the fundus image is finite, each fundus region in the fundus image captured darkly is different. Since it is not appropriate to grasp the difference between the two, it is advantageous to perform imaging under these substantially parallel conditions.

Examining the direction dependence of the polarization preservation is considered effective for diagnosis of a thin portion of the retinal layer (for example, near the macula).

Investigating the polarization characteristics of such an object has been conventionally performed with a mineral microscope or the like.However, since an excessive amount of illumination light is projected on the human eye, it has conventionally been detailed in a long time. It is difficult to observe the polarization characteristics. In contrast, the present invention is effective for obtaining necessary information in a short photographing time and observing in detail later.

According to this embodiment, despite the fact that the polarized illumination light is rotated about the optical axis every 10 ° using the CCD camera 20 for imaging, the imaging can be performed in a short time without burdening the patient. There is.

Although the embodiments have been described above, it is also possible to fix one of the illumination system polarization element 8 and the imaging system polarization element 16 and rotate the other to photograph a fundus image.

(Effect) Since the fundus camera according to the present invention is configured as described above, it has an effect that it is suitable for analyzing the polarization characteristics of the anatomy of the fundus.

ADVANTAGE OF THE INVENTION According to the image display method concerning this invention, the polarization characteristic of the biological structure of a fundus can be observed easily, easily, and finely.

[Brief description of the drawings]

 FIG. 1 is an optical diagram of a fundus camera according to the present invention, FIG. 2 is a control system diagram of the fundus camera according to the present invention, and FIG. 3 is an explanatory diagram of image display. DESCRIPTION OF SYMBOLS 1 ... Illumination optical system, 2 ... Shooting optical system 4 ... Halogen lamp (illumination light source) 8 ... Polarization element for illumination system, 13 ... Eye to be examined 14 ... Objective lens, 15 ... Hole mirror 16 ... ... Polarizing element for photographing system 20 ... CCD camera (imaging means) 23 ... Fundus, 26 ... TV monitor

Claims (4)

(57) [Claims] An illumination optical system is provided with an illumination system polarizing element for linearly polarizing illumination light for fundus illumination, and said illumination system polarization element is selected from among reflected light having polarization characteristics based on the anatomy of the fundus. A polarizing element for the imaging system that transmits a polarization component that is substantially orthogonal to the polarization component that transmits the element is provided in the imaging optical system, and the illumination system polarization element and the imaging system polarization element are substantially orthogonal to each other. A fundus camera that rotates the optical system around the optical axis of each of the optical systems while maintaining a relationship of transmitting light, and captures a fundus image based on polarized illumination light at predetermined angles. 2. An illumination optical system further comprising: an illumination system polarization element for linearly polarizing illumination light for fundus illumination, wherein the illumination system polarization element includes reflected light having polarization characteristics based on the anatomy of the fundus. The imaging optical system is provided with an imaging system polarizing element that transmits a polarization component that is substantially parallel to a polarization component that passes through the element, and the illumination system polarization element and the imaging system polarization element are used to change the polarization components that are substantially parallel to each other. A fundus camera, characterized in that the fundus camera is rotated around the optical axis of each of the optical systems while maintaining a transmission relationship, and captures a fundus image based on polarized illumination light at predetermined angles. 3. A fundus camera according to any one of claims 1 and 2, wherein a plurality of fundus images are obtained by imaging the fundus at each rotation angle of a polarizing element. Dividing the fundus into a plurality of fundus parts, comparing the corresponding fundus parts for the entire fundus image with each other, determining the brightest fundus part for each fundus part, and determining the brightest fundus part. The operation of cutting out the fundus image including the brightest image of the fundus region as an image piece is performed for all fundus regions, and the fundus image is combined by combining the image pieces of the fundus image that is brightest captured for each fundus region. An image display method characterized by reconstructing and displaying an image. 4. A fundus camera according to any one of claims 1 and 2, wherein a plurality of fundus images are obtained by imaging the fundus at each rotation angle of a polarizing element. Dividing the fundus into a plurality of fundus parts, comparing the corresponding fundus parts with respect to the fundus image, determining the darkest fundus part for each fundus part, and determining the darkest fundus part The work of cutting out from the fundus image including the darkest fundus part as an image piece is performed for all fundus parts, and the fundus image is combined by combining the image pieces consisting of the fundus part that is captured darkest for each fundus part. An image display method characterized by reconstructing and displaying.